8 human cell Smallest living structure and constituent unit of human beings; the sizes and shapes of cells vary according to their function. CELL AND TISSUES Golgi apparatus Organelle composed of a series of pockets that receive proteins produced by the ribosomes and either transport them outside the cell or to other organelles. centriole Structure consisting of small rods that play a major role in cell division. Each cell usually contains two. nuclear envelope Envelope formed of two layers surrounding the nucleus and pierced with small holes, which allow exchanges between the cytoplasm and the nucleus. lysosome Small spheroid organ containing enzymes that break down food, spent cell components and other harmful substances that have been absorbed. vacuole Spherical cavity containing water, waste and various substances required by the cell. cytoplasm Clear gelatinous substance surrounding the various cellular structures. mitochondrion Ovoid organelle that produces the energy necessary for cell activity. endoplasmic reticulum Organelle formed of walls to which the ribosomes are attached. ribosome Organelle, free or attached to the endoplasmic reticulum, producing proteins essential to the constitution and functioning of living beings. nucleus Organelle containing a cell’s genes and controlling its activities. chromatin Mass of very fine filaments of DNA, the genetic material of the cell; it is compressed into chromosomes during cell division. cell membrane The cell’s flexible outer casing; it separates the cell from the surrounding environment and works as a filter to control the entry and exit of certain substances.
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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.
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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.
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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
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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
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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
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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
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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.