8

human cellSmallest living structure and constituent unit of human beings; the sizes and shapes of cells vary according totheir function.

C E L L A N D T I S S U E S

Golgi apparatusOrganelle composed of a series of pockets

that receive proteins produced by theribosomes and either transport them outside

the cell or to other organelles.

centrioleStructure consisting of small rods thatplay a major role in cell division. Each

cell usually contains two.

nuclear envelopeEnvelope formed of two layers

surrounding the nucleus and piercedwith small holes, which allow exchangesbetween the cytoplasm and the nucleus.

lysosomeSmall spheroid organ containing enzymes

that break down food, spent cellcomponents and other harmful substances

that have been absorbed.

vacuoleSpherical cavity containing water,

waste and various substances requiredby the cell.

cytoplasmClear gelatinous substance

surrounding the various cellularstructures.

mitochondrionOvoid organelle that produces theenergy necessary for cell activity.

endoplasmic reticulumOrganelle formed of walls to which the

ribosomes are attached.

ribosomeOrganelle, free or attached to the

endoplasmic reticulum, producingproteins essential to the constitution

and functioning of living beings.

nucleusOrganelle containing a cell’s genes and

controlling its activities.

chromatinMass of very fine filaments of DNA, the

genetic material of the cell; it iscompressed into chromosomes during

cell division.

cell membraneThe cell’s flexible outer casing; it

separates the cell from the surroundingenvironment and works as a filter tocontrol the entry and exit of certain

substances.

9

human cellC E L L A N D T I S S U E S

neuronCell that receives, carries, and

transmits messages in the form ofnerve impulses.

osteocyteIrregularly shaped cell making up bony

tissue.

photoreceptorNerve cell in the retina that convertslight into nerve impulses; these aretransmitted to the cerebrum, whichdecodes them and forms an image.

neutrophilBlood cell that plays an essential role the

body’s defense, characterized by a nucleuswith several lobes and a granular

cytoplasm.

red blood cellBlood cell that transports oxygen andcontains a pigment (hemoglobin); redblood cells are the most numerous.

eggMature female reproductive cell

produced by the ovary, which, afterfertilization by a spermatozoon, enables

the embryo to develop.

spermatozoonMature and mobile reproductive malecell produced by the testicle; the main

constituent of the sperm used tofertilize an egg.

muscle fiberComponent tissue of the muscle; it

includes several nuclei and numerousparallel filaments that can contract

themselves.

examples of cellsThe human body contains some 200 types of

cells. All cells have the same general structurebut are adapted according to their function in

the body.

DNAComplex molecule containing genes, contained in cell nuclei and formed of strands of nucleotides arranged in adouble helix.

10

chromatidEach of the two strands of a

chromosome. During cell division, thetwo strands separate at the centromere.

nucleolusSmall spherical body located inside

the nucleus, within which theribosomes, or protein-synthesizing

structures, are produced.

nucleoplasmGelatinous substance in which thenucleolus and chromatin float.

centromereShort section of the chromosome

joining the two chromatids.

nucleusOrganelle containing a cell’s genes andcontrolling its activities.

chromosomeElement, composed of DNA and proteins,

that carries genetic information. Humancells have 46, which can be observed only

during cell division.

C E L L A N D T I S S U E S

DNA

11

adenineNitrogenous base that can pair up onlywith the thymine in the DNA molecule.

cytosineNitrogenous base complementary to

guanine.

thymineNitrogenous base complementary to

adenine.

guanineNitrogenous base that can pair up onlywith the cytosine in the DNA molecule.

chromatinMass of very fine filaments of DNA, the

genetic material of the cell; it iscompressed into chromosomes during

cell division.

nitrogenous baseMolecule forming a nucleotide. The fournitrogenous bases assemble in the DNA

molecule to form a sequence that isspecific to each individual.

nucleotideThe basic unit of DNA molecules,

composed of a phosphate group and asugar, linked to a nitrogenous base.

nucleosomeMass formed of part of a DNAmolecule coiled around a core of eighthistone molecules.

C E L L A N D T I S S U E S

12

epithelial tissueTissue, formed of closely packed cells,that lines most of the internal andexternal surfaces of the body.

microvillusSmall cytoplasmic protuberance thatincreases the exchange surface ofcells.

basement membraneMembrane on which epithelial cells sitand that connects them with theunderlying vascular tissues.

connective tissueTissue formed of cells floating in anabundant matrix. Cartilage, bonetissue, and most of the tissues thatmake up the organs are connectivetissues.

macrophageCell whose main function is to destroyundesirable elements (foreign bodies,debris, dead cells).

fibroblastCell that manufactures the fibers inconnective tissue.

intercellular matrixSubstance surrounding the cells of theconnective tissue. It is formed mainly

of liquid and fibers.

tissuesCombinations of cells and molecules making up the organs of the human body.

C E L L A N D T I S S U E S

13

muscle tissueTissue forming muscles, whichcontracts in response to a nerve

impulse sent by the central nervoussystem.

muscle fiberComponent tissue of the muscle.

nerve tissueTissue specializing in transmission of

nerve impulses. It is composed ofneurons and glial cells, which protect

and nourish the neurons.

microgliocyteVery small glial cell that rids the nervetissue of foreign bodies and dead cells.

neuronNerve cell that receives, carries, and

transmits messages in the form ofnerve impulses.

oligodendrocyteGlial cell that plays a role in formationof the myelin sheath of the neurons in

the central nervous system.

astrocyteGlial cell whose numerous extensions

terminate in feet that form barriersbetween neurons and blood capillaries.

tissuesC E L L A N D T I S S U E S

14

armpitDepression located beneath theshoulder between the arm and thethorax and covered with hair at puberty.

thoraxBony cage forming the upper portion ofthe trunk and containing the majorrespiratory and circulatory organs(lungs, heart).

abdomenSoft part forming the lower portion ofthe trunk and containing variousorgans of the digestive, urinary andreproductive systems.

ankleJoint of the foot articulating with the

leg, forming internal (tibia) andexternal (ulna) lateral protuberances.

breastAnterior section of the thorax

containing the nipple; unlike in thefemale, the breast plays no role in the

male.

penisMale erectile organ enabling

copulation and excretion of urine.

toeEach of the five terminal parts of the

foot formed of various articulatedbones and ending in a nail.

anterior view

navelScar in the shape of a small round

depression, the result of severing theumbilical cord that connected the fetus

to the mother.

pubisTriangular protuberance of the lower

abdomen; it is covered with hair atpuberty.

kneeJoint that articutes the thighbone(femur) with the lower section of theleg (tibia).

shoulderUpper limb joint articulating with thethorax; extremely mobile, the shoulderis capable of a wide range ofmovements.

instepUpper portion of the foot between the metatarsus and theankle.

manMale human being producing cells able to fertilize the ovum (egg); the male’s skeleton is generally larger andheavier than that of the female.

H U M A N B O D Y

skullBony structure enclosing and

protecting the brain.

faceFront portion of the head bounded by

the hair, ears and chin.

Adam’s appleProtuberance of a man’s neck formed

by the juncture of two strips ofcartilage from the larynx.

foreheadUpper portion of the face between the

eyebrows and the hair roots andextending between the temples.

templeLateral portion of the head between the

forehead, eye, cheek and ear.

earOrgan of hearing that collects sounds;

the inner ear is also the organ ofequilibrium.

hairHair of the head mainly protecting theskin of the skull; its appearance andcolor vary with each individual.

manH U M A N B O D Y

15

chinProtruding portion of the face thatvaries in shape; it corresponds to thelower jawbone.

mouthAnterior cavity of the digestive tractbounded by the lips; it enables thedigestion of food, among otherfunctions.

noseMid-facial protuberance having twoorifices (nostrils); it has an olfactoryand respiratory function.