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Human biology

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Human biology is the study of the biochemical process that make up the human metabolism.

Also see Human biology A-Z


Table of contents:

.A | .B | .C | .D | .E | .F | .G | .H | .I | .J | .K | .L | .M

.N | .O | .P | .Q | .R | .S | .T | .U | .V | .W | .X | .Y | .Z

blood-type classification based on the presence or absence of A and B glycoproteins on the erythrocyte membrane surface

the combination of an acetyl group derived from pyruvic acid and coenzyme A which is made from pantothenic acid (a B-group vitamin)

enzyme that breaks down ACh into acetyl and choline

a substance that donates hydrogen ions and therefore lowers pH

globular contractile protein that interacts with myosin for muscle contraction

a momentary change in the electrical potential of a neuron (or muscle) membrane

the amount of initial energy necessary for reactions to occur

an immunity that occurs as a result of the activity of the body's own cells rather than from antibodies acquired from an external source

a specifc region on the enzyme where the substrate binds

the method of transporting material that requires energy

a specifc immune response that occurs after exposure to an antigen either from a pathogen or a vaccination

the attraction between water molecules and molecules of a diferent substance

the endocrine gland associated with the kidneys

arteriole that branches from the cortical radiate artery and enters the glomerulus

clustering of cells into masses linked by antibodies

(plural = alae) small, faring structure of a nostril that forms the lateral side of the nares

cartilage that supports the apex of the nose and helps shape the nares; it is connected to the septal cartilage and connective tissue of the alae

most abundant plasma protein, accounting for most of the osmotic pressure of plasma

the mechanism for inhibiting enzyme action in which a regulatory molecule binds to a second site (not the active site) and initiates a conformation change in the active site, preventing binding with the substrate

air space within alveoli that are unable to participate in gas exchange

small tube that leads from the terminal bronchiole to the respiratory bronchiole and is the point of attachment for alveoli alveolar macrophage

cell of the alveolus that removes debris and pathogens

opening that allows airflow between neighboring alveoli

cluster of alveoli

small, grape-like sac that performs gas exchange in the lungs

a monomer of a protein

a structure within the limbic system that processes fear

an enzyme found in saliva and secreted by the pancreas that converts carbohydrates to maltose

describes the pathway that requires a net energy input to synthesize complex molecules from simpler ones

assembly of more complex molecules from simpler molecules

cellular respiration the use of an electron acceptor other than oxygen to complete metabolism using electron transport-based chemiosmosis

the stage of mitosis during which sister chromatids are separated from each other

(plural = anastomoses) area where vessels unite to allow blood to circulate even if there may be partial blockage in another branch

air space present in the airway that never reaches the alveoli and therefore never participates in gas exchange

defciency of red blood cells or hemoglobin angiotensin converting enzyme (ACE) enzyme that converts angiotensin I to angiotensin II

product in the renin-angiotensin-aldosterone pathway

molecule that afects diferent organs to increase blood pressure

a negative ion formed by gaining electrons

vessels that parallel the small cardiac arteries and drain the anterior surface of the right ventricle; bypass the coronary sinus and drain directly into the right atrium

(also, left anterior descending artery or LAD) major branch of the left coronary artery that follows the anterior interventricular sulcus

sulcus located between the left and right ventricles on the anterior surface of the heart

hormone that prevents the loss of water

(also, immunoglobulins or gamma globulins) antigen-specifc proteins produced by specialized B lymphocytes that protect the body by binding to foreign objects such as bacteria and viruses

a protein that is produced by plasma cells after stimulation by an antigen; also known as an immunoglobulin

a macromolecule that reacts with cells of the immune system and which may or may not have a stimulatory efect antigen-presenting cell (APC) an immune cell that detects, engulfs, and informs the adaptive immune response about an infection by presenting the processed antigen on its cell surface

the exit point of the digestive system for waste material

(also, aortic semilunar valve) valve located at the base of the aorta

tip of the external nose

network of neurons within the pons that stimulate the neurons in the dorsal respiratory group; controls the depth of inspiration

a form of science that solves real-world problems

artery that branches from the interlobar artery and arches over the base of the renal pyramids

(also, resistance vessel) very small artery that leads to a capillary

short vessel connecting an arteriole directly to a venule and bypassing the capillary beds

blood vessel that conducts blood away from the heart; may be a conducting or distributing vessel

medical device that transmits electrical signals to the heart to ensure that it contracts and pumps blood to the body

part of the loop of Henle that ascends from the renal medulla to the renal cortex

amount of force that is exerted by gases in the air surrounding any given surface

a basic unit of matter that cannot be broken down by normal chemical reactions

the number of protons in an atom

(also, adenosine triphosphate) the cell's energy currency

a membrane-embedded protein complex that regenerates ATP from ADP with energy from protons difusing through it

clump of myocardial cells located in the inferior portion of the right atrium within the atrioventricular septum; receives the impulse from the SA node, pauses, and then transmits it into specialized conducting cells within the interventricular septum

(also, bundle of His) group of specialized myocardial conductile cells that transmit the impulse from the AV node through the interventricular septum; form the left and right atrioventricular bundle branches

(also, left or right bundle branches) specialized myocardial conductile cells that arise from the bifurcation of the atrioventricular bundle and pass through the interventricular septum; lead to the Purkinje fbers and also to the right papillary muscle via the moderator band

cardiac septum located between the atria and ventricles; atrioventricular valves are located here

one-way valves located between the atria and ventricles; the valve on the right is called the tricuspid valve, and the one on the left is the mitral or bicuspid valve

(plural = atria) upper or receiving chamber of the heart that pumps blood into the lower chambers just prior to their contraction; the right atrium receives blood from the systemic circuit that fows into the right ventricle; the left atrium receives blood from the pulmonary circuit that fows into the left ventricle

sense of hearing

extension of an atrium visible on the superior surface of the heart

the part of the peripheral nervous system that controls bodily functions

ability of cardiac muscle to initiate its own electrical impulse that triggers the mechanical contraction that pumps blood at a fxed pace without nervous or endocrine control

a tube-like structure that propagates a signal from a neuron's cell body to axon terminals

electrically sensitive structure on the cell body of a neuron that integrates signals from multiple neuronal connections

structure on the end of an axon that can form a synapse with another neuron

tube-like structure that propagates a signal from a neuron's cell body to axon terminals


a lymphocyte that matures in the bone marrow

(also, interatrial band) group of specialized conducting cells that transmit the impulse directly from the SA node in the right atrium to the left atrium

an interconnected collections of cells in the brain that are involved in movement and motivation

a substance that absorbs hydrogen ions and therefore raises pH

science that seeks to expand knowledge regardless of the short-term application of that knowledge

sti8 structure in the cochlea that indirectly anchors auditory receptors

(also, mitral valve or left atrioventricular valve) valve located between the left atrium and ventricle; consists of two _aps of tissue

a digestive juice produced by the liver; important for digestion of lipids

yellowish bile pigment produced when iron is removed from heme and is further broken down into waste products

green bile pigment produced when the non-iron portion of heme is degraded into a waste product; converted to bilirubin in the liver

  GLOSSARY 425 the concept of energy _ow through living systems

the study of living organisms and their interactions with one another and their environments

a collection of all ecosystems on Earth * bipolar neuron]] neuron with two processes from the cell body, typically in opposite directions

liquid connective tissue composed of formed elements3erythrocytes, leukocytes, and platelets3and a _uid extracellular matrix called plasma; component of the cardiovascular system

relationship between blood pH and oxygen dissociation from hemoglobin

a mass of food resulting from chewing action and wetting by saliva

hard, dense connective tissue that forms the structural elements of the skeleton

structure that encloses the glomerulus

  • Boyle's law relationship between volume and pressure as described by the formula: P1V1 = P2V2

a portion of brain that connects with the spinal cord; controls basic nervous system functions like breathing and swallowing

portion of the external nose that lies in the area of the nasal bones

collective name for the multiple branches of the bronchi and bronchioles of the respiratory system

branch of bronchi that are 1 mm or less in diameter and terminate at alveolar sacs

tube connected to the trachea that branches into many subsidiaries and provides a passageway for air to enter and leave the lungs

a solution that resists a change in pH by absorbing or releasing hydrogen or hydroxide ions

thin, pale layer of leukocytes and platelets that separates the erythrocytes from the plasma in a sample of centrifuged blood

the paired glands in the human male that produce a secretion that cleanses the urethra prior to ejaculation

(also, atrioventricular bundle) group of specialized myocardial conductile cells that transmit the impulse from the AV node through the interventricular septum; form the left and right

Table of contents:

.A | .B | .C | .D | .E | .F | .G | .H | .I | .J | .K | .L | .M

.N | .O | .P | .Q | .R | .S | .T | .U | .V | .W | .X | .Y | .Z


structure that connects the renal pelvis to the renal medulla

(singular = canaliculus) channels within the bone matrix that house one of an osteocyte's many cytoplasmic extensions that it uses to communicate and receive nutrients

(cd) unit of measurement of luminous intensity (brightness)

ability of a vein to distend and store blood

  • capacitance vessels veins and capillary bed network of capillaries connecting arterioles to venules.

smallest of blood vessels where physical exchange occurs between the blood and tissue cells surrounded by interstitial _uid

bound form of hemoglobin and carbon dioxide

compound of carbon dioxide and hemoglobin, and one of the ways in which carbon dioxide is carried in the blood

a biological macromolecule in which the ratio of carbon to hydrogen to oxygen is 1:2:1; carbohydrates serve as energy sources and structural support in cells

enzyme that catalyzes the reaction that causes carbon dioxide and water to form carbonic acid

period of time between the onset of atrial contraction (atrial systole) and ventricular relaxation (ventricular diastole)

tissue muscle tissue found only in the heart; cardiac contractions pump blood throughout the body and maintain blood pressure

depression in the medial surface of the inferior lobe of the left lung where the apex of the heart is located

(also, skeleton of the heart) reinforced connective tissue located within the atrioventricular septum; includes four rings that surround the openings between the atria and ventricles, and the openings to the pulmonary trunk and aorta; the point of attachment for the heart valves

muscle cell of the heart

  • cartilage semi-rigid connective tissue found on the skeleton in areas where _exibility and smooth surfaces support movement

describes the pathway in which complex molecules are broken down into simpler ones, yielding energy as an additional product of the reaction

breaking down of more complex molecules into simpler molecules

a positive ion formed by losing electrons

  • cell cycle checkpoints mechanisms that monitor the preparedness of a eukaryotic cell to advance through the various cell cycle stages

the ordered sequence of events that a cell passes through between one cell division and the next

a structure formed during plant-cell cytokinesis by Golgi vesicles fusing at the metaphase plate; will ultimately lead to formation of a cell wall to separate the two daughter cells

smallest independently functioning unit of all organisms; in animals, a cell contains cytoplasm, composed of _uid and organelles

the smallest fundamental unit of structure and function in living things

a rigid cell covering made of cellulose in plants, peptidoglycan in bacteria, non-peptidoglycan compounds in Archaea, and chitin in fungi that protects the cell, provides structural support, and gives shape to the cell

an adaptive immune response that is controlled by T cells

a polysaccharide that makes up the cell walls of plants and provides structural support to the cell

longitudinal channel in the center of each osteon; contains blood vessels, nerves, and lymphatic vessels; also known as the Haversian canal

one of the specialized receptors that are located in the brain that sense changes in hydrogen ion, oxygen, or carbon dioxide concentrations in the brain

the nervous system made up of the brain and spinal cord; covered with three layers of protective meninges

a large plant cell organelle that acts as a storage compartment, water reservoir, and site of macromolecule degradation

a paired rod-like structure constructed of microtubules at the center of each animal cell centrosome

the brain structure involved in posture, motor coordination, and learning new motor actions

the outermost sheet of brain tissue; involved in many higher-order functions

a clear liquid that surrounds the brain and 9lls its ventricles and acts as a shock absorber

an interaction between two or more of the same or di8erent elements that results in the formation of molecules

the movement of hydrogen ions down their electrochemical gradient across a membrane through ATP synthase to

chiasmata (singular = chiasma) the structure that forms at the crossover points after genetic material is exchanged

a type of carbohydrate that forms the outer skeleton of arthropods, such as insects and crustaceans, and the cell walls of fungi

facilitated di8usion that exchanges bicarbonate (HCO32)with chloride (Cl2) ions

a plant cell organelle that carries out photosynthesis

string-like extensions of tough connective tissue that extend from the _aps of the atrioventricular valves to the papillary muscles

a mixture of partially digested food and stomach juices

(plural: cilia) a short, hair-like structure that extends from the plasma membrane in large numbers and is used to move an entire cell or move substances along the outer surface of the cell

describes a time cycle about one day in length

branch of the left coronary artery that follows coronary sulcus

a series of enzyme-catalyzed chemical reactions of central importance in all living cells that harvests the energy in carbon-carbon bonds of sugar molecules to generate ATP; the citric acid cycle is an aerobic metabolic pathway because it requires oxygen in later reactions to proceed

  428 GLOSSARY a constriction formed by the actin ring conducting zone clitoris during animal-cell cytokinesis that leads to cytoplasmic division region of the respiratory system that includes the organs and structures that provide passageways for air and are not

a sensory and erectile structure in female mammals, homologous to the male penis,

cone weakly photosensitive, chromatic, cochlea whorled structure that contains receptors for transduction of the mechanical wave into an electrical signal

three consecutive nucleotides in mRNA that specify the addition of a speci9c amino acid or the release of a polypeptide chain during translation

the intermolecular forces between water molecules caused by the polar nature of water; creates surface tension

the largest portion of the large intestine consisting of the ascending colon, transverse colon, and descending colon

a set of populations inhabiting a particular area

dense osseous tissue that can withstand compressive forces

a general mechanism of enzyme activity regulation in which a molecule other than the enzyme's substrate is able to bind the active site and prevent the substrate itself from binding, thus inhibiting the overall rate of reaction for the enzyme

an array of approximately 20 soluble proteins of the innate immune system that enhance phagocytosis, bore holes in pathogens, and recruit lymphocytes

an area of high concentration across from an area of low concentration cone-shaped neuron in the fovea of the retina that detects bright light and is used in daytime color vision

most common type of capillary, found in virtually all tissues except epithelia and cartilage; contains very small gaps in the endothelial lining that permit exchange

a part of an experiment that does not change during the experiment

transparent layer over the front of the eye that helps focus light waves

branches of the ascending aorta that supply blood to the heart; the left coronary artery feeds the left side of the heart, the left atrium and ventricle, and the interventricular septum; the right coronary artery feeds the right atrium, portions of both ventricles, and the heart conduction system

large, thin-walled vein on the posterior surface of the heart that lies within the atrioventricular sulcus and drains the heart myocardium directly into the right atrium

sulcus that marks the boundary between the atria and ventricles

vessels that drain the heart and generally parallel the large surface arteries

a thick nerve bundle that connects the cerebral hemispheres

the endocrine tissue that develops from an ovarian follicle after ovulation; secretes progesterone and estrogen during pregnancy

outer layer of an organ like the kidney or adrenal gland

nephron that lies in the renal cortex

peritubular capillary network that allows exchange of solutes and water from the renal tubules

osmotic gradient in the renal medulla that is responsible for concentration of urine

a type of strong bond between two or more of the same or di8erent elements; forms when electrons are shared between elements

portion of the larynx composed of a ring of cartilage with a wide posterior region and a thinner anterior region; attached to the esophagus

blood test for identi9cation of blood type using antibodies and small samples of blood

(also, recombination) the exchange of genetic material between homologous chromosomes resulting in chromosomes that incorporate genes from both parents of the organism forming reproductive cells

a chemical messenger that regulates cell di8erentiation, proliferation, and gene expression to e8ect immune responses

the division of the cytoplasm following mitosis to form two daughter cells

the entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals

the network of protein 9bers that collectively maintains the shape of the cell, secures some organelles in speci9c positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move

the gel-like material of the cytoplasm in which cell structures are suspended

an adaptive immune cell that directly kills infected cells via enzymes, and that releases cytokines to enhance the immune


statement of the principle that a speci9c gas type in a mixture exerts its own pressure, as if that speci9c gas type was not part of a mixture of gases

a form of logical thinking that uses a general statement to forecast speci9c results

the loss of shape in a protein as a result of changes in temperature, pH, or exposure to chemicals

a structure that extends away from the cell body to receive messages from other neurons

structure that extends away from the cell body to receive messages from other neurons

an immune cell that processes antigen material and presents it on the surface of its cell in MHC class II molecules and induces an immune response in other cells

molecule of hemoglobin without an oxygen molecule bound to it

a double-stranded polymer of nucleotides that carries the hereditary information of the cell

a 9ve-carbon sugar molecule with a hydrogen atom rather than a hydroxyl group in the 2' position; the sugar component of DNA nucleotides

a change in the membrane potential to a less negative value

change in the membrane potential to a less negative value

part of the loop of Henle that descends from the renal cortex into the renal medulla

a form of science that aims to observe, explore, and 9nd things out

a linkage between adjacent epithelial cells that forms when cadherins in the plasma membrane attach to intermediate 9laments

changes an organism goes through during its life

tubular shaft that runs between the proximal and distal ends of a long bone

period of time when the heart muscle is relaxed and the chambers 9ll with blood

  process by which unspecialized cells become specialized in structure and function

a passive process of transport of low-molecular weight material down its concentration gradient

describes a cell, nucleus, or organism containing two sets of chromosomes (2n)

layer of spongy bone, that is sandwiched between two the layers of compact bone found in _at bones

two sugar monomers that are linked together by a peptide bond

part of the renal tubule that is the most distant from the glomerulus

the enzyme that catalyzes the joining of DNA fragments together

an enzyme that synthesizes a new strand of DNA complementary to a template strand

region of the medulla oblongata that stimulates the contraction of the diaphragm and intercostal muscles to induce inspiration

intermediate portion of the external nose that connects the bridge to the apex and is supported by the nasal bone

the molecular shape of DNA in which two strands of nucleotides wind around each other in a spiral shape

a decrease in the number of hormone receptors in response to increased


all living things in a particular area together with the abiotic, nonliving parts of that environment

an organism that relies primarily on environmental heat sources to maintain its body temperature

a lymphocyte that has di8erentiated, such as a B cell, plasma cell, or cytotoxic T cell

arteriole that exits from the glomerulus

  • elastic artery (also, conducting artery) artery with abundant elastic 9bers located closer to the heart, which maintains the pressure gradient and conducts blood to smaller branches

surface recording of the electrical activity of the heart that can be used for diagnosis of irregular heart function; also abbreviated as EKG

a gradient produced by the combined forces of the electrical gradient and the chemical gradient

a negatively charged particle that resides outside of the nucleus in the electron orbital; lacks functional mass and has a charge of 21

the movement of electrons from one element to another

a series of four large, multi-protein complexes embedded in the inner mitochondrial membrane that accepts electrons from donor compounds and harvests energy from a series of chemical reactions to generate a hydrogen ion gradient across the membrane

one of 118 unique substances that cannot be broken down into smaller substances and retain the characteristic of that substance; each element has a speci9ed number of protons and unique properties

(also, preload) the amount of blood in the ventricles at the end of atrial systole just prior to ventricular contraction

amount of blood remaining in each ventricle following systole

describes a chemical reaction that results in products that store more chemical potential energy than the reactants

innermost layer of the heart lining the heart chambers and heart valves; composed of endothelium reinforced with a thin layer of connective tissue that binds to the myocardium

process in which bone forms by replacing hyaline cartilage

the gland that secretes hormones into the surrounding interstitial _uid, which then di8use into blood and are carried to various organs and tissues within the body

a type of active transport that moves substances, including _uids and particles, into a cell

the group of organelles and membranes in eukaryotic cells that work together to modify, package, and transport lipids and proteins

a series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids

  432 layer of smooth, simple squamous epithelium that lines the endocardium and blood vessels

an organism that relies primarily on internal heat sources to maintain its body temperature

a catalyst in a biochemical reaction that is usually a complex or conjugated protein

a molecule that catalyzes a biochemical reaction

surface arteries of the heart that generally follow the sulci

innermost layer of the serous pericardium and the outermost layer of the heart wall

leaf-shaped piece of elastic cartilage that is a portion of the larynx that swings to close the trachea during swallowing

completely ossi9ed remnant of the epiphyseal plate

(also, growth plate) sheet of hyaline cartilage in the metaphysis of an immature bone; replaced by bone tissue as the organ grows in length

wide section at each end of a long bone; 9lled with spongy bone and red marrow

(also, red blood cell) mature myeloid blood cell that is composed mostly of hemoglobin and functions primarily in the transportation of oxygen and carbon dioxide

a tubular organ that connects the mouth to the stomach

  a nutrient that cannot be synthesized by the body; it must be obtained from food

a reproductive hormone in females that assists in endometrial regrowth, ovulation, and calcium absorption

an organism with cells that have nuclei and membrane-bound organelles

a cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs

the release of water molecules from liquid water to form water vapor

the process of gradual change in a population that can also lead to new species arising from older species excitatory postsynaptic potential

depolarization of a postsynaptic membrane caused by neurotransmitter molecules released from a presynaptic cell

describes a chemical reaction that results in products with less chemical potential energy than the reactants, plus the release of free energy

the gland that secretes chemicals through ducts that lead to skin surfaces, body cavities, and organ cavities.

a process of passing material out of a cell

  • exon a sequence present in protein-coding mRNA after completion of pre-mRNA splicing

(also, exhalation) process that causes the air to leave the lungs

  GLOSSARY 433 amount of air that can be forcefully exhaled after a normal tidal exhalation

membrane composed of elastic 9bers that separates the tunica media from the tunica externa; seen in larger arteries

region of the nose that is easily visible to others

gas exchange that occurs in the alveoli

  • extracellular matrix the material, primarily collagen, glycoproteins, and proteoglycans, secreted from animal cells that holds cells together as a tissue, allows cells to communicate with each other, and provides mechanical protection and


a process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins

able to be disproven by experimental results

a lipid molecule composed of three fatty acids and a glycerol (triglyceride) that typically exists in a solid form at room temperature

portion of the posterior oral cavity that connects the oral cavity to the oropharynx

a mechanism of enzyme activity regulation in which the product of a reaction or the 9nal product of a series of sequential reactions inhibits an enzyme for an earlier step in the reaction series

type of capillary with pores or fenestrations in the endothelium that allow for rapid passage of certain small materials

the steps that follow the partial oxidation of glucose via glycolysis to regenerate NAD+;occurs in the absence of oxygen and uses an organic compound as the 9nal electron acceptor

protein-containing storage form of iron found in the bone marrow, liver, and spleen

the union of two haploid cells typically from two individual organisms

plasma protein produced in the liver and involved in blood clotting

specialized membrane that connects the ends of the C-shape cartilage in the trachea; contains smooth muscle 9bers

(plural: _agella) the long, hair-like structure that extends from the plasma membrane and is used to move the cell

a model of the structure of the plasma membrane as a mosaic of components, including phospholipids, cholesterol, proteins, and glycolipids, resulting in a _uid rather than static character

a reproductive hormone that causes sperm production in men and follicle development in women

opening in the fetal heart that allows blood to _ow directly from the right atrium to the left atrium, bypassing the fetal pulmonary circuit

  434 (also, hyperpnea) mode of breathing that occurs during exercise or by active thought that requires muscle contraction for both inspiration and expiration

cellular components of blood; that is, gene   a channel between two adjacent animal cells that allows ions, nutrients, and other low-molecular weight substances to pass between the cells, enabling the cells to

erythrocytes, leukocytes, and platelets

  • fossa ovalis oval-shaped depression in the interatrial septum that marks the former location of the foramen ovale

region in the center of the retina with a high density of photoreceptors and which is responsible for acute vision

the part of the cerebral cortex that contains the motor cortex and areas involved in planning, attention, and language

sum of ERV and RV, which is the amount of air that remains in the lungs after a


a cell-cycle phase distinct from the G1 phase of interphase; a cell in G0 isnot preparing to divide

(also, 9rst gap) a cell-cycle phase; 9rst phase of interphase centered on cell growth during mitosis

(also, second gap) a cell-cycle phase; third phase of interphase where the cell undergoes the 9nal preparations for mitosis

the organ that stores and concentrates bile

  • gamete a haploid reproductive cell or sex cell (sperm or egg)

the physical and functional unit of heredity; a sequence of DNA that codes for a speci9c peptide or RNA molecule

the amino acids that correspond to three-nucleotide codons of mRNA

the entire genetic complement (DNA) of an organism

the length of time of development, from conception to birth, of the young of a viviparous animal

the development before birth of a viviparous animal

(also, glial cells) cells that provide support functions for neurons

(also, glial cells) the cells that provide support functions for neurons

heme-containing globular protein that is a constituent of hemoglobin

heterogeneous group of plasma proteins that includes transport proteins, clotting factors, immune proteins, and others

Filtration of blood in the glomerular capillary network into the glomerulus

amount of Filtrate formed by the glomerulus per minute

part of the renal corpuscle that contains the capillary network

in the olfactory bulb, one of the two neural clusters that receives signals from one type of olfactory receptor

opening between the vocal folds through which air passes when producing speech

a storage carbohydrate in animals

the process of breaking glucose into two three-carbon molecules with the production of ATP and NADH

a eukaryotic organelle made up of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution gonadotropin-releasing hormone

a hormone from the hypothalamus that causes the release of FSH and LH from the anterior pituitary

vessel that follows the interventricular sulcus on the anterior surface of the heart and _ows along the coronary sulcus into the coronary sinus on the posterior surface; parallels the anterior interventricular artery and drains the areas supplied by this vessel

process of increasing in size


relationship between the partial pressure of oxygen and the a_nity of hemoglobin for carbon dioxide

describes a cell, nucleus, or organism containing one set of chromosomes (n)

interruption in the normal conduction pathway

sounds heard via auscultation with a stethoscope of the closing of the atrioventricular valves (-lub.) and semilunar valves (-dub.)

the energy transferred from one system to another that is not work

an enzyme that helps to open up the DNA helix during DNA replication by breaking the hydrogen bonds

a cell of the adaptive immune system that binds APCs via MHC class II molecules and stimulates B cells or secretes cytokines to initiate the immune response

(also, packed cell volume) volume percentage of erythrocytes in a sample of centrifuged blood

production of blood cells, which occurs in the red marrow of the bones

red, iron-containing pigment to which oxygen binds in hemoglobin

oxygen-carrying compound in erythrocytes

  • hemolysis destruction (lysis) of erythrocytes and the release of their hemoglobin into circulation hemolytic disease of the newborn

(also, erythroblastosis fetalis) disorder causing agglutination and hemolysis in an Rh+ fetusor newborn of an Rh- mother

protein-containing storage form of iron found in the bone marrow, liver, and spleen

  • Henry's law hilum concentration of gas in a liquid is directly proportional to the solubility and partial

a weak bond between partially positively charged hydrogen atoms and partially negatively charged elements or molecules

region in the renal pelvis where blood vessels, nerves, and ureters bunch before entering or exiting the kidney

the brain structure in the temporal lobe involved in processing memories

opening or depression in a bone

the ability of an organism to maintain constant internal conditions

chromosomes of the same length with genes in the same location; diploid organisms have pairs of homologous chromosomes, and the members of each pair come from di8erent parents

a chemical released by cells in one area of the body that a8ects cells in other parts of the body

a chemical signaling molecule, usually a protein or steroid, secreted by an endocrine gland or group of endocrine cells; acts to control or regulate speci9c physiological processes

an organism that is invaded by a pathogen or parasite human beta chorionic gonadotropin

a hormone produced by the chorion of the zygote that helps to maintain the corpus luteum and elevated levels of progesterone

describes a substance that dissolves in water; water-loving

describes a substance that does not dissolve in water; water-fearing

(also, farsightedness) visual defect in which the image focus falls behind the retina, thereby making images in the distance clear, but close-up images blurry

change in the membrane potential to a more negative value

describes a solution in which extracellular _uid has higher osmolarity than the _uid inside the cell

pathological enlargement of the heart, generally for no known reason

the brain structure that controls hormone release and body homeostasis

a suggested explanation for an event, which can be tested

a form of science that begins with a speci9c explanation that is then tested

describes a solution in which extracellular _uid has lower osmolarity than the _uid inside the cell

below-normal level of oxygen saturation of the adaptive immune response that is blood (typically <95 percent) controlled by activated B cells and antibodies

Table of contents:

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.N | .O | .P | .Q | .R | .S | .T | .U | .V | .W | .X | .Y | .Z


an acquired ability to prevent an unnecessary or harmful immune response to a detected foreign body known not to cause disease

(also, antibodies or gamma globulins) antigen-speci9c proteins produced by specialized B lymphocytes that protect the body by binding to foreign objects such as bacteria and viruses

(also, anvil) second of the three bones of the middle ear

a form of logical thinking that uses related observations to arrive at a general conclusion

large systemic vein that returns blood to the heart from the inferior portion of the body

one of the main veins in the human body

  • in_ammation the localized redness, swelling, heat, and pain that results from the movement of leukocytes through opened capillaries to a site of infection

a hormone made by Sertoli cells, provides negative feedback to hypothalamus in control of FSH and GnRH release

hyperpolarization of a postsynaptic membrane caused by neurotransmitter molecules released from a presynaptic cell

an immunity that occurs naturally because of genetic factors or physiology, and is not caused by infection or vaccination

innermost part of the ear; consists of the cochlea and the vestibular system

(also, inhalation) process that causes air to enter the lungs

sum of the TV and IRV, which is the amount of air that can maximally be inhaled past a tidal expiration

amount of air that enters the lungs due to deep inhalation past the tidal volume

(also, Bachmann's bundle) group of specialized conducting cells that transmit the impulse directly from the SA node in the right atrium to the left atrium

cardiac septum located between the two atria; contains the fossa ovalis after birth

physical junction between adjacent cardiac muscle cells; consisting of desmosomes, specialized linking proteoglycans, and gap junctions that allow passage of ions between the two cells

a cytokine that inhibits viral replication

a period of rest that may occur between meiosis I and meiosis II; there is no replication of DNA during interkinesis

artery that branches from the segmental artery and travels in between the renal lobes

membrane composed of elastic 9bers that separates the tunica intima from the tunica media; seen in larger arteries

gas exchange that occurs at the level of body tissues

specialized conductile cells within the atria that transmit the impulse from the SA node throughout the myocardial cells of

the period of the cell cycle leading up to mitosis; includes G1,S, and G2 phases; the interim between two consecutive cell divisions

a cell type found next to the seminiferous tubules that makes testosterone

the _uid found between cells in the body, similar in constitution to the _uid component of blood, but without the high concentrations of proteins

a cell type found next to the seminiferous tubules that makes testosterone

cardiac septum located between the two ventricles

(intrapulmonary pressure) pressure of the air within the alveoli

a hormone receptor in the cytoplasm or nucleus of a cell

pressure of the air within the pleural cavity

non2protein-coding intervening sequences that are spliced from mRNA during processing

an atom or compound that does not contain equal numbers of protons and electrons, and therefore has a net charge

a chemical bond that forms between ions of opposite charges

pigmented, circular muscle at the front of the eye that regulates the amount of light entering the eye

describes a solution in which the extracellular _uid has the same osmolarity as the _uid inside the cell

one or more forms of an element that have di8erent numbers of neutrons

(also, isovolumetric contraction) initial phase of ventricular contraction in which tension and pressure in the ventricle increase, but no blood is pumped or ejected from the heart

initial phase of the ventricular diastole when pressure in the ventricles drops below pressure in the two major arteries, the pulmonary trunk, and the aorta, and blood attempts to _ow back into the ventricles, producing the dicrotic notch of the ECG and closing the two semilunar

J juxtaglomerular cell cell in the a8erent and e8erent arterioles that responds to stimuli from the macula densa

nephron that lies in the cortex but close to the renal medulla, kidney organ that performs excretory and osmoregulatory functions

the organ that performs excretory and osmoregulatory functions

the type of energy associated with objects in motion

a protein structure in the centromere of each sister chromatid that attracts and binds spindle microtubules during


labia majora   GLOSSARY 439 the large folds of tissue covering inguinal area

the smaller folds of tissue within labia lens transparent, convex structure behind the cornea that helps focus light waves on the retina majora

  • labyrinth bony, hollow structure that is the most internal part of the ear; contains the sites of transduction of auditory and vestibular information

(singular = lacuna) spaces in a bone that house an osteocyte

during replication of the 3' to 5' strand, the strand that is replicated in short fragments and away from the replication fork

a digestive system organ that reabsorbs water from undigested material and processes waste matter

region where the two lamina of the thyroid cartilage join, forming a protrusion known as -Adam's apple.

portion of the pharynx bordered by the oropharynx superiorly and esophagus and trachea inferiorly; serves as a route for both air and food

cartilaginous structure that produces the voice, prevents food and beverages from entering the trachea, and regulates the volume of air that enters and leaves the lungs

the strand that is synthesized continuously in the 5' to 3' direction that is synthesized in the direction of the replication fork

(also, mitral valve or bicuspid valve) valve located between the left atrium and

life science a 9eld of science, such as biology, that studies living things

a connected brain area that processes emotion and motivation

lymphoid tissue located at the base of the tongue

a class of macromolecules that are nonpolar and insoluble in water

Filter paper that has been treated with a natural water-soluble dye so it can be used as a pH indicator

an organ that produces bile for digestion and processes vitamins and lipids

renal pyramid along with the adjoining cortical region

the position of a gene on a chromosome

  • loop of Henlepart of the renal tubule that loops into the renal medulla

interior of a tubular structure such as a blood vessel or a portion of the alimentary canal through which blood, chyme, or other substances travel

a reproductive hormone in both men and women, causes testosterone production in men and ovulation and lactation in women.

  • lymphocyte a type of white blood cell that includes natural killer cells of the innate immune system and B and T cells of the adaptive immune system
  • lysosome an organelle in an animal cell that functions as the cell's digestive component; it breaks down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles   appropriate template into which antigens can be loaded for recognition by lymphocytes
  • malleus (also, hammer) 9rst of the three bones of the middle ear marginal arteries branches of the right coronary artery that supply blood to the super9cial portions of the right ventricle
  • mass number the number of protons plus neutrons in an atom
  • mast cell M macromolecule a large molecule typically formed by the joining of smaller molecules
  • macromolecule a large molecule, often formed by polymerization of smaller monomers
  • macrophage a large phagocytic cell that engulfs foreign particles and pathogens
  • macrophage phagocytic cell of the myeloid lineage; a matured monocyte macula densa group of cells that senses changes in sodium ion concentration; present in parts of the renal tubule and collecting ducts major histocompatibility class (MHC) I a group of proteins found on the surface of all nucleated cells that signals to immune cells whether the cell is normal or is infected or cancerous; it also provides the appropriate sites into which antigens can be loaded for recognition by lymphocytes major histocompatibility class (MHC) II
  • molecule a protein found on the surface of antigen-presenting cells that signals to immune cells whether the cell is normal or is infected or cancerous; it provides the a leukocyte that produces in_ammatory molecules, such as histamine, in response to large pathogens
  • matter anything that has mass and occupies space
  • meatus one of three recesses (superior, middle, and inferior) in the nasal cavity attached to the conchae that increase the surface area of the nasal cavity
  • medulla middle layer of an organ like the kidney or adrenal gland medullary cavity hollow region of the diaphysis; 9lled with yellow marrow meiosis I the 9rst round of meiotic cell division; referred to as reduction division because the resulting cells are haploid meiosis II the second round of meiotic cell division following meiosis I; sister chromatids are separated from each other, and the result is four unique haploid cells
  • membrane potential a di8erence in electrical potential between the inside and outside of a cell
  • membrane potential diference in electrical potential between the inside and outside of a cell memory cell an antigen-speci9c B or T lymphocyte that does not di8erentiate into an e8ector cell during the primary immune response but that can immediately become an e8ector cell on reexposure to the same pathogen
  • meninges (singular: meninx) the membranes that cover and protect the central nervous system
  • menstrual cycle the cycle of the degradation and re-growth of the endometrium
  • mesothelium simple squamous epithelial portion of serous membranes, such as the super9cial portion of the epicardium (the visceral pericardium) and the deepest portion of the pericardium (the parietal pericardium)
  • metabolism all the chemical reactions that take place inside cells, including those that use energy and those that release energy
  • metabolism sum of all of the body's chemical reactions metaphase plate the equatorial plane midway between two poles of a cell where the chromosomes align during metaphase
  • metaphase the stage of mitosis during which chromosomes are lined up at the metaphase plate metarteriole short vessel arising from a terminal arteriole that branches to supply a capillary bed
  • microcirculation blood _ow through the capillaries middle cardiac vein   vessel that parallels and drains the areas supplied by the posterior interventricular artery; drains into the great cardiac vein
  • middle ear part of the hearing apparatus that functions to transfer energy from the tympanum to the oval window of the inner ear
  • mineral an inorganic, elemental molecule that carries out important roles in the body mismatch repair a form of DNA repair in which non-complementary nucleotides are recognized, excised, and replaced with correct nucleotides
  • mitochondria (singular: mitochondrion) the cellular organelles responsible for carrying out cellular respiration, resulting in the production of ATP, the cell's main energy-carrying molecule
  • mitosis the period of the cell cycle at which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase mitotic phase the period of the cell cycle when duplicated chromosomes are distributed into two nuclei and the cytoplasmic contents are divided; includes mitosis and cytokinesis mitotic spindle the microtubule apparatus that orchestrates the movement of chromosomes during mitosis
  • mitral valve (also, left atrioventricular valve or bicuspid valve) valve located between the left atrium and ventricle; consists of two _aps of tissue modeling   442   process, during bone growth, by which bone is resorbed on one surface of a bone and deposited on another moderator band band of myocardium covered by endocardium that arises from the inferior portion of the interventricular septum in the right ventricle and crosses to the anterior papillary muscle; contains conductile 9bers that carry electrical signals followed by contraction of the heart
  • molecule a chemical structure consisting of at least two atoms held together by a chemical bond
  • monocyte a type of white blood cell that circulates in the blood and lymph and di8erentiates into a macrophage after it moves into infected tissue
  • monosaccharide a single unit or monomer of carbohydrates motor end plate sarcolemma of the muscle 9ber that interacts with the neuron
  • mRNA messenger RNA; a form of RNA that carries the nucleotide sequence code for a protein sequence that is translated into a polypeptide sequence
  • murmur unusual heart sound detected by auscultation; typically related to septal or valve defects muscular artery (also, distributing artery) artery with abundant smooth muscle in the tunica media that branches to distribute blood to the arteriole network
  • mutation a permanent variation in the nucleotide sequence of a genome
  • myelin   fatty substance produced by glia that insulates axons
  • myelin sheath a cellular extension containing a fatty substance produced by glia that surrounds and insulates axons myocardial conducting cells specialized cells that transmit electrical impulses throughout the heart and trigger contraction by the myocardial contractile cells myocardial contractile cells bulk of the cardiac muscle cells in the atria and ventricles that conduct impulses and contract to propel blood
  • myocardium thickest layer of the heart composed of cardiac muscle cells built upon a framework of primarily collagenous 9bers and blood vessels that supply it and the nervous 9bers that help to regulate it myo9bril long cylindrical structures that lie parallel to the muscle 9ber myo9lament small structures that make up myo9brils
  • myopia (also, nearsightedness) visual defect in which the image focus falls in front of the retina, thereby making images in the distance blurry, but close-up images clear
  • myosin contractile protein that interacts with actin for muscle contraction N naris (plural = nares) opening of the nostrils nasal bone bone of the skull that lies under the root and bridge of the nose and is connected to the frontal and maxillary bones
  • nasal septum wall composed of bone and cartilage that separates the left and right nasal cavities  
  • nasopharynx portion of the pharynx _anked by the conchae and oropharynx that serves as an airway natural killer (NK) cell a lymphocyte that can kill cells infected with viruses or tumor cells
  • natural science a 9eld of science that studies the physical world, its phenomena, and processes
  • nephron functional unit of the kidney
  • nephron the functional unit of the kidney nervi vasorum small nerve 9bers found in arteries and veins that trigger contraction of the smooth muscle in their walls
  • neuron a specialized cell that can receive and transmit electrical and chemical signals
  • neuron specialized cell that can receive and transmit electrical and chemical signals
  • neutron a particle with no charge that resides in the nucleus of an atom; has a mass of 1
  • neutrophil a phagocytic leukocyte that engulfs and digests pathogens
  • nitrogenous base a nitrogen-containing molecule that acts as a base; often referring to one of the purine or pyrimidine components of nucleic acids nodes of Ranvier gaps in the myelin sheath where the signal is recharged
  • noncompetitive inhibition a general mechanism of enzyme activity regulation in which a regulatory molecule binds to a site other than the active site and prevents the active site from binding 443   the substrate; thus, the inhibitor molecule does not compete with the substrate for the active site; allosteric inhibition is a form of noncompetitive inhibition
  • nonpolar covalent bond a type of covalent bond that forms between atoms when electrons are shared equally between atoms, resulting in no regions with partial charges as in polar covalent bonds nontemplate strand the strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA
  • nuclear envelope the double-membrane structure that constitutes the outermost portion of the nucleus
  • nucleic acid a biological macromolecule that carries the genetic information of a cell and carries instructions for the functioning of the cell
  • nucleolus the darkly staining body within the nucleus that is responsible for assembling ribosomal subunits
  • nucleotide a monomer of nucleic acids; contains a pentose sugar, a phosphate group, and a nitrogenous base nucleotide excision repair a form of DNA repair in which the DNA molecule is unwound and separated in the region of the nucleotide damage, the damaged nucleotides are removed and replaced with new nucleotides using the complementary strand, and the DNA strand is resealed and allowed to rejoin its complement
  • nucleus (chemistry) the dense center of an atom made up of protons and (except in the case of a hydrogen atom) neutrons
  • nucleus the cell organelle that houses the cell's DNA and directs the synthesis of ribosomes and proteins nutrient foramen small opening in the middle of the external surface of the diaphysis, through which an artery enters the bone to provide nourishment   a structure formed of tissues operating together to perform a common function
  • organ functionally distinct structure composed of two or more types of tissues organ of Corti in the basilar membrane, the site of the transduction of sound, a mechanical O occipital lobe the part of the cerebral cortex that contains visual cortex and processes visual stimuli
  • octet rule states that the outermost shell of an element with a low atomic number can hold eight electrons
  • odorant airborne molecule that stimulates an olfactory receptor oil an unsaturated fat that is a liquid at room temperature Okazaki fragments the DNA fragments that are synthesized in short stretches on the lagging strand
  • olfactory bulb neural structure in the vertebrate brain that receives signals from olfactory receptors olfactory epithelium specialized tissue in the nasal cavity where olfactory receptors are located olfactory receptor dendrite of a specialized neuron
  • oogenesis the process of producing haploid eggs
  • oral cavity the point of entry of food into the digestive system
  • organ wave, to a neural signal
  • organ system group of organs that work together to carry out a particular function
  • organ system the higher level of organization that consists of functionally related organs
  • organelle a membrane-bound compartment or sac within a cell
  • organism living being that has a cellular structure and that can independently perform all physiologic functions necessary for life
  • oropharynx portion of the pharynx _anked by the nasopharynx, oral cavity, and laryngopharynx that is a passageway for both air and food orthopedist doctor who specializes in diagnosing and treating musculoskeletal disorders and injuries
  • osmolarity the total amount of substances dissolved in a speci9c amount of solution osmoregulation the mechanism by which water and solute concentrations are maintained at desired levels
  • osmosis the transport of water through a semipermeable membrane from an area of high water concentration to an area of low water concentration across a membrane osmotic balance the appropriate values of water and solute concentrations for a healthy organism osseous tissue bone tissue; a hard, dense connective tissue that forms the structural elements of the skeleton
  • ossicle one of the three bones of the middle ear ossi9cation (also, osteogenesis) bone formation
  • osteoclast cell responsible for resorbing bone osteocyte primary cell in mature bone; responsible for maintaining the matrix osteogenic cell undi8erentiated cell with high mitotic activity; the only bone cells that divide; they di8erentiate and develop into osteoblasts osteon (also, Haversian system) basic structural unit of compact bone; made of concentric layers of calci9ed matrix
  • outer ear part of the ear that consists of the pinna, ear canal, and tympanum and which conducts sound waves into the middle ear oval window thin diaphragm between the middle and inner ears that receives sound waves from contact with the stapes bone of the middle ear
  • ovarian cycle   the cycle of preparation of egg for ovulation and the conversion of the follicle to the corpus luteum oviduct (also, fallopian tube) the muscular tube connecting uterus with ovary area
  • ovulation the release of an oocyte from a mature follicle in the ovary of a vertebrate
  • oxidative phosphorylation the production of ATP by the transfer of electrons down the electron transport chain to create a proton gradient that is used by ATP synthase to add phosphate groups to ADP molecules oxygen2hemoglobin dissociation curve graph that describes the relationship of partial pressure to the binding and disassociation of oxygen to and from heme oxyhemoglobin (Hb2O2) bound form of hemoglobin and oxygen oxyhemoglobin molecule of hemoglobin to which oxygen is bound P P wave component of the electrocardiogram that represents the depolarization of the atria
  • pacemaker cluster of specialized myocardial cells known as the SA node that initiates the sinus rhythm packed cell volume (PCV) (also, hematocrit) volume percentage of erythrocytes present in a sample of centrifuged blood
  • palatine tonsil one of the paired structures composed of lymphoid tissue located anterior to the uvula at the roof of isthmus of the fauces
  • pancreas a gland that secretes digestive juices
  • pancreas the organ located between the stomach and the small intestine that contains exocrine and endocrine cells
  • papilla one of the small bump-like projections from the tongue papillary muscle extension of the myocardium in the ventricles to which the chordae tendineae attach
  • paranasal sinus one of the cavities within the skull that is connected to the conchae that serve to warm and humidify incoming air, produce mucus, and lighten the weight of the skull; consists of frontal, maxillary, sphenoidal, and ethmoidal sinuses
  • parathyroid gland the gland located on the surface of the thyroid that produces parathyroid hormone parietal lobe the part of the cerebral cortex involved in processing touch and the sense of the body in space partial pressure force exerted by each gas in a mixture of gases
  • passive immunity an immunity that does not result from the activity of the body's own immune cells but by transfer of antibodies from one individual to another
  • pathogen an agent, usually a microorganism, that causes disease in the organisms that they invade pectinate muscles muscular ridges seen on the anterior surface of the right atrium peer-reviewed article a scienti9c report that is reviewed by a scientist's colleagues before publication
  • penis the male reproductive structure for urine elimination and copulation
  • pepsin an enzyme found in the stomach whose main role is protein digestion
  • perfusion distribution of blood into the capillaries so the tissues can be supplied pericardial cavity cavity surrounding the heart 9lled with a lubricating serous _uid that reduces friction as the heart contracts pericardial sac (also, pericardium) membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the 9brous pericardium and the parietal pericardium
  • pericardium (also, pericardial sac) membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the 9brous pericardium and the parietal pericardium periodic table of elements an organizational chart of elements, indicating the atomic number and mass number of each element; also provides key information about the properties of elements peripheral chemoreceptor one of the specialized receptors located in the aortic arch and carotid arteries that sense changes in pH, carbon dioxide, or oxygen blood levels peripheral nervous system (PNS)                                                                                                                                             447   the nervous system that serves as the connection between the central nervous system and the rest of the body; consists of the autonomic nervous system and the sensory-somatic nervous system perirenal fat capsule fat layer that suspends the kidneys
  • peristalsis wave-like movements of muscle tissue peritubular capillary network capillary network that surrounds the renal tubule after the e8erent artery exits the glomerulus
  • peroxisome a small, round organelle that contains hydrogen peroxide, oxidizes fatty acids and amino acids, and detoxi9es many poisons
  • pH scale a scale ranging from 0 to 14 that measures the approximate concentration of hydrogen ions of a substance
  • phagocytosis a process that takes macromolecules that the cell needs from the extracellular _uid; a variation of endocytosis pharyngeal tonsil structure composed of lymphoid tissue located in the nasopharynx
  • pharynx region of the conducting zone that forms a tube of skeletal muscle lined with respiratory epithelium; located between the nasal conchae and the esophagus and trachea
  • pheromone substance released by an animal that can a8ect the physiology or behavior of other animals
  • philtrum concave surface of the face that connects the apex of the nose to the top lip phosphate group   a molecular group consisting of a central phosphorus atom bound to four oxygen atoms
  • phospholipid a major constituent of the membranes of cells; composed of two fatty acids and a phosphate group attached to the glycerol backbone
  • phylogenetic tree a diagram showing the evolutionary relationships among biological species based on similarities and di8erences in genetic or physical traits or both
  • physical science a 9eld of science, such as astronomy, physics, and chemistry, that studies nonliving matter pinna cartilaginous outer ear
  • pinocytosis a process that takes solutes that the cell needs from the extracellular _uid; a variation of endocytosis
  • pituitary gland the endocrine gland located at the base of the brain composed of an anterior and posterior region; also called hypophysis
  • placenta the organ that supports the transport of nutrients and waste between the mothers and fetus' blood in eutherian mammals
  • plasma in blood, the liquid extracellular matrix composed mostly of water that circulates the formed elements and dissolved materials throughout the cardiovascular system
  • plasma membrane a phospholipid bilayer with embedded (integral) or attached (peripheral) proteins that separates the internal contents of the cell from its surrounding environment
  • plasmodesma (plural: plasmodesmata) a channel that posterior interventricular sulcus passes between the cell walls of adjacent plant cells, connects their cytoplasm, and allows materials to be transported from cell to cell
  • platelets (also, thrombocytes) one of the formed elements of blood that consists of cell fragments broken o8 from megakaryocytes pneumotaxic center network of neurons within the pons that inhibit the activity of the neurons in the dorsal respiratory group; controls rate of breathing
  • polar covalent bond a type of covalent bond in which electrons are pulled toward one atom and away from another, resulting in slightly positive and slightly negative charged regions of the molecule
  • polycythemia elevated level of hemoglobin, whether adaptive or pathological
  • polypeptide a long chain of amino acids linked by peptide bonds
  • polysaccharide a long chain of monosaccharides; may be branched or unbranched
  • population all individuals within a species living within a speci9c area posterior cardiac vein vessel that parallels and drains the areas supplied by the marginal artery branch of the circum_ex artery; drains into the great cardiac vein posterior interventricular artery (also, posterior descending artery) branch of the right coronary artery that runs along the posterior portion of the interventricular sulcus toward the apex of the heart and gives rise to branches that supply the interventricular septum and portions of both ventricles sulcus located between the left and right ventricles on the anterior surface of the heart
  • potential energy the type of energy that refers to the potential to do work precapillary sphincters circular rings of smooth muscle that surround the entrance to a capillary and regulate blood _ow into that capillary
  • preload (also, end diastolic volume) amount of blood in the ventricles at the end of atrial systole just prior to ventricular contraction prepotential depolarization (also, spontaneous depolarization) mechanism that accounts for the autorhythmic property of cardiac muscle; the membrane potential increases as sodium ions di8use through the always-open sodium ion channels and causes the electrical potential to rise
  • presbyopia visual defect in which the image focus falls behind the retina, thereby making images in the distance clear, but close-up images blurry; caused by age-based changes in the lens primary immune response the response of the adaptive immune system to the 9rst exposure to an antigen
  • primer a short stretch of RNA nucleotides that is required to initiate replication and allow DNA polymerase to bind and begin replication
  • progesterone a reproductive hormone in women; assists in endometrial regrowth and inhibition of FSH and LH release
  • prokaryote a unicellular organism that lacks a nucleus or any other membrane-bound organelle

See Glossary of biology

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