A&P Exam 2: Chapter 4 Histology PART 1

Epithelial Tissue

Has little extracellular matrix (consists almost entirely of cells), lines body surfaces (in and out), free border (apical surface), basement membrane attaches to underlying tissue. Avascular so gases&nutrients must diffuse across the basement membrane. Regenerates b/c skin is constanly shedding.

Classification of epithelial tissue

based on % of cell layers and shape

simple epithelium

monolayer. extends from basement membranw to apical (free) surface.

stratified epithelium

multilayer. superficial layer is used to name the tissue.

pseudostratified epithelium

false appearence of being mulilayered but it is SIMPLE. each cell is in contact with the basement membrane. ciliated. not everything reaches the apical surface.

squamous epithelium

flat

cuboidal epithelium

boxlike

columnar epithelium

tall, narrow

stratified squamous epithelium

may be moist (mouth, esophagus, vagina, rectum). OR keratinized

Keratinized

dead outer cells that contain the tough moisture-resistant protein known as keratin

transitional epithelium

stratified. stretches without tearing. cell layers slide past one another and change shape. found in urinary bladder.

function of epithelial tissue

based on # of layers & shape of cells

function of simple epithelium

DIFFUSION (of gases in lungs), SECRETION (through glands), FILTRATION OF BLOOD (glomerulus is the kidney’s filtration system), ABSORPTION (intestines)

function of stratified epithelium

protection from abrasion & barrier function. found in areas where abrasion occurs.

function of squamous epithelium

the thinness&flatness allows for secretion, absorption & diffusion.

function of cuboidal & columnar

secretion & absorption

goblet cells

produce & secrete mucus. found in simple columnar epithelium (including pseudostratified) which is found in the respiratory and digestive tract. are a unicellular GLAND.

microvilli

increase surface area. don’t move/fixed. brush border of small intestine (simple columnar epithelium)

Cilia

direct movement across cell membrane. found in trachea and nasal cavity (psuedostratified columnar epithelium)

cell connections (junctions)

mechanically bind cells together, form a permeability barrier, provide mechanism for intercellular communication, epithelial cells produce glycoprotein that connects cell to each other (lateral surface) & basment membrane (basal surface).

desmosomes

disk-shaped structures with sticky glycoproteins. reinforce cell-cell connections. the stickyness physically hold the cells together.

hemidesmosomes

attach epithelial cells to the basement membrane.

tight junctions

form a permeability barrier (touching). material can’t pass between cells but must pass through cells instead.

zona adherens

part of tight junction. girdle of glycoproteins that bind the cell together.

zona occludens

ring around cells. loose part.

gap junctions

small protein channel that allows small polar channels to pass between cells. allow communication. found in intercalated disks of cardiac muscle.

glands

have secretory function. epithelial tissue is the main tissue that makes up a gland.

exocrine gland

has ducts. secretes sweat to surface of the body.

endocrine gland

ductless. produced and secretes HORMONES into the bloodstream.

multicellular gland

group of cells that function together as a gland, secreting substances through a duct onto the body surface. classified based on duct structure & secretion.

simple multicellular gland

duct with few branches

compound multicellular gland

duct with many branches

tubular multicellular gland

duct ends in striaght/coiled tubes.

acinar multicellular gland

duct ends in cluster of small sacs

alveolar multicellular gland

duct ends in hallow sacs

merocrine (multicellular) gland

secretion with no loss of cytoplasm. example: eccrine sweat gland

apocrine (multicellular) gland

secreition with some loss of cytoplasm. pinched off fragments. example: mammary gland.

holocrine (multicellular) gland

cell becomes part of the secretion. “HOLOcrine= shedding of WHOLE cell.” mitotic divison eventually replaces cell. example: sebaceous gland.

Connective tissue

most abundant tissue in the body, found in every organ. nonliving. makes up extracellular matrix.

Matrix components of CT

protein fibers, ground substance, and fluid present. well-vascularized.

blasts

cells that build/create matrix. example: osteoblasts

cytes

cells that maintain matrix. example: osteocytes

clasts

cells that breakdown/remodel the matrix. example: osteoclasts

Collagen fibers

strong & flexible. doesn’t stretch. primary protein in the body.

Recticular fibers

fine collagen fiber network. form a network or mesh to support organs.

Elastin fibers

stretch & recoil but return to original shape