Cell and tissues

The human body is formed of hierarchically organized components (tissues, organs, and systems), of which the basic unit is the cell. Cells are the site of intense activity: they accumulate and transmit energy, make proteins that are essential to the body’s functioning, and constantly reproduce by cellular division. They also contain all of the genes belonging to each individual.

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structure of a cell

estructura F de la célula F All human cells have a similar structure: they are formed of a nucleus surrounded by cytoplasm and encased in a membrane.

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human cell célula F humana Basic unit of the human body, whose size and shape vary depending on the functions that it performs.

centriole centríolo M

Cell structure playing a key role during mitosis.

vacuole vacuola F

Spherical cavity in which water, waste and various substances required by the

cell are stored.

mitochondrion mitocondria F

Structure associated with cell breathing; it produces and stores

energy in the cell.

endoplasmic reticulum retículo M endoplásmico

Cell structure consisting of a network of pockets surrounding the nucleus; it is

involved in protein synthesis.

cell nucleus núcleo M celular

Central core of the cell containing genetic information in the form of DNA

and guiding protein synthesis.

cytoplasm citoplasma M

Liquid substance forming the inside of the cell, around the nucleus, in which

cellular organelles bathe.

Golgi apparatus aparato M de Golgi Cell structure consisting of a group of membrane sacs; it is involved in the transport and maturation of proteins in the cell.

microfilament microfilamento M

Rod-shaped structure supporting the cell and giving it its shape.

microtubule microtúbulo M Cylindrical structure supporting the cell and allowing organelles and substances in the cell to move about.

pseudopod pseudópodo M

Extension of the cytoplasm of certain cells, serving mainly in cell

displacement.

ribosome ribosoma M

Organelle, floating free or bound to the endoplasmic reticulum, producing proteins essential to the formation and

functioning of the human body. cell membrane

membrana F celular Bilayer of lipid molecules forming the outer surface of the cell.

lipids lípidos M Molecules containing fatty acids, making up the cell membrane.

protein proteína F Organic compound formed of amino acids; in the cell membrane, proteins form channels allowing the exchange of substances with the outside environment.

Each human being is composed of more than 50 trillion cells. Hundreds of millions of them die every minute, and just as many are born through cellular division. Some, such as certain white blood cells, die after only a few hours, while others, such as neurons, may survive throughout a human being's life.

The Life of Cells

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cell nucleus

núcleo M celular Central core of the cell containing genetic

information in the form of DNA and guiding protein synthesis.

human cell

nuclear envelope envoltura F nuclear Membrane surrounding the nucleus.

chromatin cromatina F

Substance consisting of proteins and DNA contained in the nucleus; it is

compressed into chromosomes during mitosis.

nucleoplasm nucleoplasma M

Liquid substance forming the inside of the nucleus of a cell and in which

especially chromatin and nucleoli bathe.

nucleolus nucléolo M Spherical body located inside the nucleus and playing a role in the synthesis of ribosomes.

fat cell

adipocito M Cell forming the essential component

of adipose tissue and ensuring the synthesis, storage and release of lipids.

spermatozoon

espermatozoide M Mature and mobile male reproductive cell produced by the testis; the main

constituent of sperm, its purpose is to fertilize the ovum.

chondrocyte

condrocito M Cell, constituent element of cartilage.

white blood cell

glóbulo M blanco Blood cell belonging to the immune

system, thus playing an essential role in the body’s defenses.

photoreceptor

fotorreceptor M Cell found in the retina capable of

capturing light rays and translating them into nerve signals.

osteocyte

osteocito M Mature cell, constituent element of bone

tissue.

red blood cell

glóbulo M rojo Blood cell that carries oxygen from the lungs to the tissues and carbon dioxide

from the tissues to the lungs.

ovum

óvulo M Mature female reproductive cell

produced by the ovary; after fertilization by a spermatozoon, it enables an embryo

to develop.

neuron

neurona F Cell of the nervous system allowing

information to be carried in the form of electrical and chemical signals.

muscle fiber

fibra F muscular Contractile cell, constituent element of

muscles.

examples of cells ejemplos M de células F

The human body has about 200 types of cells, having very different characteristics and appearance depending on the functions that they perform in the organism.

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epithelium

tejido M epitelial Tissue formed of cells organized in layers; it serves covering, secretory and protective functions.

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tissue tejido M All the cells that have a similar structure and perform similar or complementary functions. Four main cell types make up the frame of the organism: epithelial, connective, muscle and nervous.

epithelial cell célula F epitelial

Cell component of epithelial tissue.

microvillus microvellosidad F Protrusion of the cell membrane that increases its surface.

basal lamina lámina F basal Extracellular matrix anchoring epithelial cells to adjacent tissue.

mucous cell célula F calciforme Epithelial cell that secretes mucus.

epithelium tejido M epitelial

Tissue formed of cells organized in layers; it serves covering, secretory and

protective functions.

mucous gland glándula F mucosa

Exocrine gland that secretes mainly mucus.

chorion corion M Loose connective tissue beneath the epithelial tissue of the mucous membrane.

muscularis mucosae mucosa F muscular Fine layer of smooth tissue beneath the chorion.

submucosa submucosa F Connective tissue beneath the mucous membrane.

mucus mucosidad F

Translucent viscous substance secreted by the mucous membrane and that

plays a protective role.

secretory cell célula F secretora Epithelial cell specialized in the secretion of various substances useful to the body.

excretory duct canal M excretor Duct carrying secretions from the exocrine gland.

examples of epithelia ejemplos M de tejidos M epiteliales They include tissues that form the covering of all body surfaces and line inner cavities (mucous membranes, endothelia, epidermis), and glandular tissues that have secretory functions.

exocrine gland

glándula F exocrina All secretory cells producing secretions released outside the body; they consist especially of salivary and sweat glands.

mucous membrane

mucosa F Damp epithelial tissue lining an open cavity of the body; the mucous membrane plays a role in absorption and secretion (mucus).

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examples of connective tissues ejemplos M de tejidos M conjuntivos

Connective tissue: tissue made up of relatively few cells and fibers bathed in a more or less abundant fluid; its functions are to support, protect and

fill in spaces.

tissue

cartilage tejido M cartilaginoso Connective tissue consisting of cells encased in a rigid substance; it covers the articular surfaces of bones and forms certain soft parts of the body.

adipose tissue tejido M adiposo

Connective tissue made up essentially of adipocytes; it is the body’s energy reserve.

fibrous tissue tejido M fibroso

Connective tissue characterized by an abundance of collagen fibers; it forms especially the tendons and ligaments.

elastic tissue tejido M elástico Connective tissue made up predominantly of elastic fibers; it is found especially in certain ligaments and in the walls of the arteries, trachea and vocal chords.

Connective tissue, present in all organs, is the most abundant tissue in the human body: it accounts for two thirds of the total volume of tissue.

The Most Abundant

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interphase

interfase F Period between two successive cell

divisions, during which the cell grows.

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mitosis mitosis F All the mechanisms of cell division that allow the formation of two identical daughter cells from a mother cell.

centrioles centriolos M Double cellular structures that duplicate during interphase.

chromosomes cromosomas M

Elements of the nucleus of a cell, made up of DNA and proteins and carrying genetic

information; they are observed only during cell division.

mitotic spindle huso M mitótico

Ephemeral cellular structure joining the two pairs of centrioles during mitosis.

chromatid cromátida F

One of the two strands of a chromosome.

cytoplasm citoplasma M

Gel-like substance forming the inside of the cell, around the cell nucleus.

prophase

profase F First stage of mitosis, during which the

chromatin condenses into chromosomes; the two pairs of centrioles move toward

opposite poles.

metaphase

metafase F Second stage of mitosis, during which the

chromosomes align in the middle of the cell, guided by the mitotic spindle; the

nuclear membrane disaggregates.

anaphase

anafase F Third stage of mitosis, during which the chromosomes separate into chromatids

and move to either of the cell’s poles.

telophase

telofase F Fourth stage of mitosis, during which the chromosomes reassume the appearance of the chromatin; a new nuclear envelope

appears to cordon off the two nuclei.

cytokinesis

citocinesis F Stage of mitosis during which the

cytoplasm separates in two; the original cell (or mother cell) is replaced by two

identical daughter cells.

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DNA ADN M

Complex molecule containing the genetic characteristics (genes) of every person.

DNA molecule

molécula F de ADN M The DNA molecule appears in the shape

of a double helix made up of billions of nucleotides; it is the largest molecule in

the human body.

The human genetic heritage is included in 46 chromosomes (22 pairs of autosomes and 1 pair of sex chromosomes). Each cell in the body has its own copy: for example, a skin cell contains the instruction for eye color.

Billions of Copies

adenine adenina F

Complementary nitrogenous base of thymine.

cytosine citosina F

Complementary nitrogenous base of guanine.

thymine timina F Complementary nitrogenous base of adenine.

guanine guanina F

Complementary nitrogenous base of cytosine.

nitrogenous base base F nitrogenada

Small constituent molecule of a nucleotide; there are four types that assemble in the DNA molecule to form a sequence specific to each

individual.

nucleotide

nucleótido M Basic unit of DNA molecules, consisting

of a nitrogenous base.

chromatid cromátida F One of two strands of a chromosome, consisting of a short arm and a long arm; during cell division, the two chromatids separate at the centromere.

centromere centrómero M Short section of a chromosome that holds the two chromatids together.

X chromosome cromosoma M X

Sex chromosome present in both men and women.

Y chromosome cromosoma M Y

Sex chromosome present only in men.

autosome

autosoma M Chromosome that carries hereditary characteristics unrelated to sex. sex chromosomes

cromosomas M sexuales Chromosomes responsible for

determining sex.

chromosomes cromosomas M

Elements of the nucleus of a cell, made up of DNA and proteins and carrying genetic

information; they are observed only during cell division.