Histology: Epithelial Tissue

what are epithelial tissue

basic human tissue made of tightly joint cells

what are the poles of epithelial cells

basal, apical, lateral

what attaches the basal pole to the basement membrane

hemidesmosomes

how do you characterize squamous cells (appearance)

flattened cells

how do you characterize cuboidal cells (appearance)

equal dimensions (cube-like)

how do you characterize columnar cells (appearance)

taller than they are wide

what are the functions of squamous cells

1. protection

2. transcytosis

3. secretion

What are the functions of cuboidal cells?

1. protection

2. secretion and absorption

3. active transport for substances

What are the functions of columnar cells?

1. protection

2. mostly absorption

what is another name for the intercellular adhesion "tight junction"

zonula occludens

what is another name for the intercellular adhesion "adherens junction"

zonula adherens

what is another name for the intercellular adhesion "desmosome"

macula adherens

what is the function of the tight junction (zonula occludens)

form seals between adjacent cells

What are adherens junction? (zonula adherens)

strong cell adhesion for anchoring

What are desmosomes (macula adherens)?

spots around the cells for anchoring

What is the function of hemidesmosomes?

binds basal pole to cell basal lamina (anchoring)

what is another name for basal lamina

basement membrane

where is the terminal bar of cells located

apical-lateral side of cells

what is the function of microvilli

increase surface area for absorption

where is microvilli found

intestinal epithelium

what is the function of stereocilia

increase surface area for absorption, detect motion

where is stereocilia found

epididymis and hair cells of inner ear

what is the function of cilia

movement of extracellular material, and sensory functions

where is cilia found

respiratory epithelium

what are microtubules of axoneme continuous with

microtubules in the basal body

what type of collagen is found in the basal lamina

type IV (4) forms a 2D network

what is the basal lamina

network of fibrils produced by epithelial cells

Underneath the basal pole of epithelial cells:

• Laminin (glycoproteins)- attach to integrins and project into network of type IV collagen

• Nidogen and perlecan: cross link laminin; help determine porosity of BM

how is the reticular lamina bound to the basal lamina

by type VII collagen

what does the basement membrane proteins mediate

cell-to-cell interactions

what adheres the basal layer to the basal lamina

hemidesmosomes

what is the important mitotic activity of epithelial membranes

self-renewal

are epithelial tissues vascular or avascular?

avascular (no blood vessels)- nutrients are obtained by diffusion

How do epithelial tissues receive nutrients?

from the connective tissue through diffusion

What is the general function of epithelial tissues?

lining and covering body surfaces

where does epithelial tissue not line/cover

• articular cartilage

• tooth enamel

• anterior surface of iris

what is the function of simple squamous epithelium

regulate passage of substance

What is the function of simple cuboidal epithelium?

active transport, and secretion

What is the function of simple columnar epithelium?

specialize in absorption

what type of epithelium contain terminal bars

simple columnar epithelium

where are the terminal bars of simple columnar epithelium located

at apical end of cells

which epithelium have all cells that attach to basement membrane but not all apical sides reach the surface

pseudostratified columnar epithelium

most common type of stratified epithelia

stratified squamous

what is stratified squamous keratinized epithelium

epidermis of skin

What are characteristics of stratified squamous keratinized epithelium

• prevents dehydration

• protects against MO invasion

what are the characteristics of stratifies squamous keratinized epithelium in the superficial layer

• squamous

• anucleate

• dead

• packed-in-keratin cells

where can you find stratified squamous non-keratinized epithelium

• oral cavity

• esophagus

• vagina

where can you find stratified cuboidal/columnar epithelium

at the anorectal junction (transition between anus and rectum)

what cells are in the superficial layer of the transitional epithelium

dome-like cells (umbrella cells)

what type of epithelium do you find unicellular glands

Scattered secretory cells:

• simple cuboidal

• simple columnar

• pseudostratified

what do multicellular glands secrete

1. proteins-pancreas

2. lipids-sebaceous glands

3. complex proteins and carbs-salivary glands

4. water and electrolytes (filtered from blood)-sweat glands

where do glands develop from

epithelial tissue

what is parenchyma

functional tissue of an organ

what is septa

separates glands into lobules

what are the types of exocrine glands

• Merocrine (most common type of exocrine gland)- secretion by exocytosis (ex. golgi complex)

• Holocrine- secretion by disintegration of secretory glands (ex. holocrine glands)

• Apocrine-Secretion involves loss of cytoplasmic content from vesicle (ex. mammary glands)

what are polar cells in the cytoplasm

acidophilia and basophilia

What are merocrine glands?

Glands that release fluid products by exocytosis

What are holocrine glands?

glands that release entire cells (sebaceous glands)

what are apocrine glands

secrete fluid by loss of membrane-enclosed cytoplasm

what components are in merocrine glands of serous cells

• non-glycoslyated proteins

• well developed RER

• golgi complexes

• apical secretory granules

• polar cells

• small duct

what components are in merocrine glands or mucous cells

• heavily glycosylated proteins

• RER

• golgi appartus

• apical secretory granules

• PAS positive

• wider duct

• stain pale

do endocrine glands have myoepithelial cells

no

do endocrine glands have ducts

no

where do myoepithelial cells occur

at the basal end of secretory cells

what are myoepithelial cells rich in

actin filaments and myosins

how are epithelial cells renewed

by mitosis of stem cells

how are myoepithelial cells attached to the basal lamina

by gap junctions and desmosomes

The terminal bar (TEM) is a junctional complex. What forms the terminal bar?

• Zonula occludens (tight junctions)

• Zonula adherens (adherens junctions)

• Macula adherens (desmosomes)

Stereocilia are non motile, and they don’t act like regular cilia. Stereocilia instead:

Increase surface of absorption, and detect motion.

Found in:

• epididymis

• hair cells of inner ear

What is the composition of glycocalyx?

Carbohydrates and polysaccharides

Primary cilium is

non motile in non-epithelial cells