Tissues: Epithelium

Question 1

Epithelial tissue definition

Answer 1

a sheet of cells that covers a body surface or lines a body cavity (cover a surface/line a lumen)
forms most exocrine glands

Question 2

functions of epithelium

Answer 2

protection, secretion, absorption, diffusion, sensory reception

Question 3

Special characteristics of epithelia

Answer 3

cellularity - lots of cells separated by minimal extracellular material
specialized contacts - joined by special junctions
basement membrane - connective tissue layer that epithelial cells sit on
polarity - cell regions of the apical surface differ from basal surface
Avascular but innervated
regenerativ

Question 4

Simple squamous epithelium

Answer 4

single layer of flat cells with disc shaped nuclei
function: passage of materials by passive diffusion and filtration, secretes lubricating substances
location: alveoli, lining of heart, blood vessels, lining of ventral body cavities (serosae)

Question 5

Simple cuboidal epithelium

Answer 5

single layer of cubelike cells with large, spherical, central nuclei
function: secretion and absorption via facilitated diffusion and active transport
location: kidney tubules, secretory portions of glands

Question 6

simple columnar epithelium

Answer 6

single layer of column-shaped cells with oval nuclei (some have cilia, many contain goblet cells)
function: absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus or reproductive cells by ciliary action
location: lines digestive tract, gallbladder, uterine tubes, uterus

Question 7

pseudostratified columnar epithelium

Answer 7

all cels contact the basement membrane but have the illusion of not, only tall cells reach the apical surface, contain cilia and goblet cells, nuclei lie at varying heights within cell
function: secretion of mucus, propulsion of mucus by cilia
location: trachea and most of the upper respiratory system

Question 8

stratified squamous epithelium

Answer 8

keratinized:
epidermis, contains protective protein keratin, waterproof, surface cells are dead
nonkeratinized:
forms moist lining of body openings (esophagus, mouth, vagina, urethra)

function - protects underlying tissues in areas subject to abrasion

Question 9

transitional epithelium

Answer 9

has characteristics of stratified cuboidal and squamous, top cells are domed when not distended
function - permits distension of urinary organs
location - urinary bladder, ureters

Question 10

endocrine glands

Answer 10

ductless glands that secrete directly into the surrounding tissue fluid - produce hormones

Question 11

exocrine glands

Answer 11

have ducts that carry products to epithelial surface (ex. sweat or saliva)

Question 12

unicellular exocrine glands

Answer 12

made of a single cell
ex. goblet cell produces mucin

Question 13

multicellular exocrine gland

Answer 13

made of of many cells
two basic parts: Duct that empties in/onto epithelium (branched or unbranched) ; secretory unit (tubular - straight tube shaped ; acinar or alveolar - saclike structure)

Question 14

tight junctions

Answer 14

close of intracellular space
found a apical region of most epithelium
fuses proteins in plasma membrane of adjacent cells
prevents certain molecules from passing / impenetrable

Question 15

adhesive belt junctions

Answer 15

transmembrane linker proteins attach to actin microfilaments of the cytoskeleton to bind adjacent cells
forms band on connectivity between two cells on the apical side

Question 16

desmosomes (junciton)

Answer 16

main type of junction
scattered along sides of adjacent cells
cytoplasmic side of each plasma membrane has a plaque joined by linker proteins
common in cardiac and epithelial tissue

Question 17

gap junction

Answer 17

passageway between two adjacent cells
let small molecules move directly between neighboring cells
connected by hollow cylinders of protein
aid intercellular communication