A&P Chapter 4 Section 1

Tissue classes

1) Epithelial 2) Connective 3) Muscle 4) Neural

intercellular attachements

1) Occluding junctions 2) adhesion belt 3) gap junctions 4) desmosomes

Functions of the epithelial tissue

1) Provide physical protection 2) Control permeability 3) Provide sensation 4) Produce specialized secretions.

methods of secretion

1) merocrine secretion 2) apocrine secretion 3) holocrine secretion

Membranous organelles

1)Golgi apparatus (facing apical surface) 2) Endoplasmic reticulum (often extensive around the nucleus) 3) Nucleus (in a tall cell, located closer to the base than the apical surface) 4) Mitochondria (may be apical or basal, depending on cell functions)

lumen

a passageway or space inside a tube such as in the intestinal tract

intracellular cement

a thin layer of proteoglycans that contain polysaccharide derivatives, most notably hyaluronan.

control permiability

any substance that enters or leaves the body has to cross an epithelium. Most are capable of selective absorption or secretion. The epithelial barrier can be regulated and modified in response to various stimuli.

cuboidal shape

appear like little boxes

columnar shape

appear like tall, relatively slender rectangles

columnar epithelium

appear rectangular. In reality they are hexagonal, but they are taller and more slender than cells in a cuboidal epithelium. the elongated nuclei are crowded into a narrow band close to the basal lamina.

squamous shape

appear thin and flat

glands

are derived from epithelia, but secretory cells predominate; there are two types: exocrine glands and endocrine glands.

simple cuboidal epithelia

are found lining exocrine glands and ducts. they are also found in portions of the kidneys and lining secretory chambers in the thyroid gland.

microvilli

are often found on the apical surfaces of epithelial cells that line internal passageways of digestive, urinary, and reproductive tracts.

stratified columnar epithelium

are relatively rare. may have either two layers or multiple layers. In the latter case, only the superficial cells are columnar in shape. They are most often found lining large ducts such as those of the salivary glands or pancreas.

stratified cuboidal epithelia

are relatively rare. they are most common along the ducts of sweat glands, mammary glands, and other exocrine glands.

squamous epithelium

are thin, flat, and somewhat irregular in shape. In sectional view, the disc-shaped nucleus occupies the thickest portion of each cell.

cell adhesion molecules (CAMs)

are transmembrane proteins that bind to each other and to extracellular materials.

hemidesmosomes

attach the deepest epithelial cells to the basal lamina. the basal cytoskeleton is locked to peripheral proteins and to transmembrane proteins that are firmly attached to a layer of extracellular protein filaments and fibers.

holocrine secretion

by contrast, destroys the gland cell. The entire cell becomes packed with secretory products and then bursts, releasing the secretion and killing the cell. Further secretion depends on the replacement of destroyed gland cells by the division of stem cells.

connexons

channel proteins that form a narrow passageway and let small molecules and ions pass from cell to cell.

tissues

collections of cells and cell products that perform a relatively limited number of specialized functions.

dense layer (lamina densa)

containing bundles of coarse protein fibers, gives the basal lamina its strength and acts as a filter that restricts diffusion between the adjacent tissues and the epithelium.

clear layer (lamina lucida)

contains glycoproteins and a network of fine protein filaments.

stratified epithelia

contains several layers of cells. generally located in areas that need protection from mechanical or chemical stresses ,such as the surface of the skin and the lining of the mouth.

Epithelia

cover exposed surfaces and line internal cavities and passageways; they often contain secretory cells, or gland cells, scattered among the other cell types.

cilia

cover the apical surfaces in portions o fthe respiratory and reproductive tracts. They beat in a coordinated fashion

provide physical protection

epithelia protect exposed and internal surfaces from abrasion, dehydration, and destruction by chemical or biological agents.

Produce specialized secretions

epithelial cells that produce secretions are called gland cells. Individual gland cells are often scattered among other cell types in an epithelium that may have many other functions.

occluding junctions

form a barrier that isolates the basolateral surfaces and deeper tissues from the contents of the lumen

simple columnar epithelia

found lining the stomach, intestine, gallbladder, uterine tubes, and ducts within the kidneys. These cells may have microvilli, which increase surface area for absorption, or cilia that move substances across the apical surface.

stratified squamous epithelium

generally located where mechanical or chemical stresses are severe. The cells form a series of layers, like the layers in a sheet of plywood. Form the surface of the skin and line the mouth, throat, esophagus, rectum, anus, and vagina.

simple gland

has a single duct that does not divide on its way to the gland cell. May be one of the following: 1)simple tubular 2) simple coiled tubular 3) simple branched tubular (branched refers to the glandular areas and not the duct) 4) simple alveolar or acinar (sac or chamber pockets) 5) simple branched alveolar

compound gland

if the duct divides one or more times on its way to the gland cells. May be one of the following: 1) compound tubular 2) compound alveolar 3) compound tubloalveolar

basolateral surface

include both the basal surface, where the cell attaches to underlying epithelial cells or deeper tissues, and the lateral surfaces, where the cell contacts its neighbors.

Epithelial tissue includes

includes epithelia and glands

mucous cells

individual secretory cells in epithelia that have independent, scattered gland cells that secrete mucin.

apocrine secretion

involves the loss of cytoplasm as well as the secretory product. the apical portion of the cytoplasm becomes packed with secretory vesicles and is then shed. milk production in the mammary glands involves a combination of merocrine and aporcine secretions.

transitional epithelium

is an unusual stratified epithelium because, unlike most epithelia, it tolerates repeated cylces of stretching and recoiling without damage. line the urinary bladder, the ureters, and the urine-collecting chambers within the kidneys.

avascular

lack blood vessels

Pseudostratified Columnar Epithelium

line the nasal cavities, the trachea, and larger airways of the lungs. They are also found along portions of the male reproductive tract. the epithelium appears to be layered, however it is not truly stratified, though, because every epithelial cell contacts the basal lamina.

adhesion belt

locks together the terminal webs of neighboring cells, strengthening the apical region and preventing distortion and leakage at the occluding junctions.

glandular epithelia

many epithelia contain gland cells that are specialized for secretion. collection of epithelial cells that produce secretions are called glands.

simple sqamous epithelium

most delicate type of epithelium. located in protected regions where absorption of diffusion takes place, or where a slick, slippery surface reduces friction. Found along passageways in the kidneys, inside the eye, and at the gas exchange surfaces (alveoli) of the lungs.

keratinized

on exposed body surfaces, mechanical stress and dehydration are potential problems. apical layers of epithelial cells are packed with filaments of the protein keratin that makes the layers tough and water resistant.

simple epithelia

only one layer of cells present

Basal lamina

or basement membrane, is a complex structure produced by the basal surface of the epithelium and the underlying connective tissue.

gap junctions

permit chemical communication that coordinates the activities of adjacent cells.

desmosomes

provide firm attachment between neighboring cells by interlocking their cytoskeletons.

polarity

refers to the presence of structural and functional differences between the exposed and attached surfaces.

cuboidal epithelium

resemble hexagonal boxes. spherical nuclei near the center of each cell, and the distance between adjacent nuclei is roughly equal to the height of the epithelium.

nonkeratinized

resists abrasion but will dry out and deteriorate unless kept moist. found in the oral cavity, pharynx, esophagus, anus, and vagina.

enocrine glands

secrete hormones or precursors into the interstitial fluid, usually for distribution by the bloodstream.

exocrine glands

secrete onto external surfaces or into internal passageways (ducts) that connect to the exterior.

Provide sensation

sensory nerves extensively innervate most epithelia. specialized epithelial cells can detect changes to the nervous system. A neuroepithelium is a sensory epithelium found in special sense organs that provide the sensations of smell, taste, sight, equilibrium, and hearing.

mesothelium

special simple squamous epithelium that lines each ventral body cavity.

endothelium

special simple squamous epithelium that lines the heart and blood vessels.

merocrine secretion

the product is released from secretory vesicles by exocytosis. this is the most common mode of secretion.

histology

the study of tissues.

exocrine gland structure

three characteristics are used to describe the structure of multicellular exocrine glands: the structure of the duct, the shape of the secretory area of the gland, and the relationship between the duct and the secretory areas.

apical surface

which faces the exterior of the body or some internal space

base

which is attached to adjacent tissues.