A&P LECTURES 4-5

apical surface

upper free side, exposed to surface or cavity

most are smooth, but some have microvilli or cilia

basal surface

lower attached side

attaches to basal lamina, an adhesive sheet that holds basal surface of epithelia cells to underlying cells

two types of epithelial junctions:

tight junctions and desmosomes

basement membrane

made up of basal and reticular lamina

restricts stretching and tearing

reinforces epithelial sheet and defines epithelial boundary

what is epithelium supplied by?

nerve fibers

simple squamous epithelium

rapid diffusion or filtration are priority

ex: kidney, lungs

endothelium

lining of lymphatic vessels, blood vessels and heart

special simple squamous epithelia

mesothelium

serous membranes in ventral body cavity

special simple squamous epithelium

simple cuboidal epithelium

involved in secretion and absorption

forms walls of smallest ducts of glands and many kidney tubules

simple columnar eptithelium

involved in absorption and secretion of mucus, enzymes and other substances

found in digestive tract, gallbladder, ducts of some glands, bronchi, and uterine tubes

pseudo-stratified columnar epithelium

involved in secretion (mucus) and movement of mucs via ciliary sweeping actions

located in upper respiratory tract, ducts of large glands and tubules in testes

stratified squamous epithelium

located in areas of high wear and tear

transitional epithelium

forms lining of hollow urinary organs (bladder, ureters and urethra)

ability of cells to change shape when stretched

unicellular exocrine glands

mucous cells and goblet cells

all produce mucin

multicellular exocrine glands

usually surrounded by supportive connective tissue that supplies blood and nerve fibers to gland

merocrine

products secreted by exocytosis as secretions are produced (sweat, pancreas, salivary)

holocrine

products accumulate within cell, then rupture (sebaceous oil glands)

collagen fibers

strongest and most abundant type of connective tissue fibers

tough and provides high tensile strengths

elastic fibers

networks of long, thin, elastin fibers that allow for stretch and recoil

reticular fibers

short, fine, highly branched collagenous fibers

branching forms of networks that offer more “give”

ground substance

unstructured gel-like material that fills space between cells

medium through which solutes diffuse between blood capillaries and cells

loose connective tissues:

areolar, adipose, reticular

dense connective tissues:

dense regular, dense irregular, elastic

adipose

white fat- high nutrient storage (cells called adipocytes)

brown fat- contain many mitochondria and use lipid fuels to heat bloodstream

elastic

contains a higher proportion of elastic fibers

found in walls of many large arteries and some ligaments

cartilage

tough yet flexible material that lacks nerve fibers

hyaline cartilage

most abundant

found at tips of long bones, nose, trachea, larynx ad cartilage of the ribs

elastic cartilage

has more elastic fibers than hyaline

found in ears and epiglottis

fibrocartilage

properties between hyaline and dense regular tissue

strong, so found in interverbral discs and knee

osteoblasts

produce matrix

osteocytes

maintain the matrix

bone deposition

new bone matrix deposited by osteoblasts

osteoid seam

surface of the bone

band of un-mineralized bone matrix that marks area of new matrix

calcification front

abrupt transition zone between osteoid seam and older mineralized bone

osteoclasts

dig depressions/grooves as they break down matrix

secrete lysosomal enzymes and protons that digest matrix

mechanical stress

causes remodeling by producing electrical signals when bone is deformed