epithelial tissue

tissues

similar cells/ extracellular subs w common function

4 major types of tissues (ECMN)

1. epithelial tissue

2. connective tissue

3. muscle tissue

4. nervous tissue

basic epithelial tissue locations (3):

1. linings of organs : inner surface

2. coverings of organs: outer surface

3. Glands

basic functions of epithelial tissues (5):

1. protection

2. absorption

3. secretion

4. diffusion

5. filtration

6 characteristics of epithelial tissue

1.cellular

2. polar

3. attached to noncellular basement membrane

4. avascular

5. innervated

6. regeneration

cellular

composed of sheets of cells

2 polar

apical surface: free, exposed to exterior/lumen

Apical = Away/Above → free/exposed.

basal surface: attached to underlying tissue

BASE = bottom/ “basement”

Polar = 2 poles

basement membrane

Noncellular membrane to which epithelial tissue is attached.

basement= foundation

avascular

lacks blood vessels

A= without+ vascular= blood vessels

innervated

has many nerves for detecting changes

innervated = nerves

regeneration

cell turnover bc constant damage

Damage → Replace → Regenerate

4 types intercellular junctions

1. tight junctions

2. adhering junctions

3. desmosomes

4. gap junctions

tight junctions

prevent passage btw cells

TIGHT = blocks

adhering junctions

stabilize apical surface

ADHERE = hold

desmosomes

resist stress

gap junctions

Direct cytoplasmic connection allowing ions and molecules to flow between cells.

GAP = things can GO through

simple

1 layer

stratified

many layers

squamous

flat cells

cuboidal

cube shaped cells

columnar

column shaped cells

simple squamous ET

structure: 1 layer flat cells

function: diffusion

location: alveoli in lungs

simple cuboidal ET

structure: 1 layer cube-shaped cells

function:secretion

location: kidney tubules

simple columnar ET

structure: 1 layer column-shaped cells

function: absorption

location: lining of stomach

PSCC- pseudostratified ciliated columnar epithelium

structure: 1 layer of ciliated, column-shaped cells “goblet cells”

function:protection

location: lining of trachea

nonkeratinized stratified squamous ET

structure: many layers of LIVING flat cells

function: protection

location: lining of mouth

keratinized stratified squamous ET

structure: many layers of DEAD flat cells

function: protection

location: epidermis

2 types glands

1. endocrine glands

2. exocrine glands

endocrine glands

ENTERS BLOOD = NO DUCTS

“blood”

secretes hormones directly into bloodstream

ex: adrenal gland

exocrine gland

EXITS into DUCTS

“ducts”

sweat glands

goblet cell

unicellular exocrine gland that secretes mucin, which forms mucus.

3 secretion types of exocrine glands -SMM

1. serous glands: secrete watery fluid (sweat)

2. mucous glands: secrete mucin (salivary glands)

3. mixed glands: both serous+ mucous

3 types secretion mechanisms -MAH “crine”

1. merocrine

2. apocrine

3. holocrine

merocrine

secretes via exocytosis

MERO = MERE EXIT → product exits, cell stays intact.

apocrine

Product accumulates at the apex of the cell, which then pinches off.

APO = A PIECE OFF

holocrine

Cell accumulates product + disintegrates.

HOLO = WHOLE cell goes