Tissues: Epithelial Tissue

Question 1

what is the study of tissues called?

Answer 1

histology

Question 2

What are the 3 characteristics that help classify tissues?

Answer 2

• structure of cells
• cell function
• extracellular matrix

Question 3

name 4 main types of tissues

Answer 3

• epithelial
• connective
• muscle
• nervous

Question 4

characteristic features of epithelial tissue

Answer 4

protective covering of surfaces inside and outside the body

• composed of many cells packed tightly together in 1 or more layers
• little to no extracellular matrix
• cover body surfaces and forms glands (including body cavities)
• has FREE (APICAL), BASAL and LATERAL surfaces
• always have a BASEMENT MEMBRANE followed by connective tissue
• AVASCULAR (don’t have direct blood supply, uses diffusion instead)
• capable of regeneration

Question 5

difference between free (apical), basal and lateral surfaces in epithelial tissue

Answer 5

FREE (APICAL): lines lumen of ducts, inside of vessels, space in cavity
BASAL: attached to basement membrane
LATERAL: sides of cells

Question 5

What is the basement membrane?

Answer 5

“glue” that holds cells in epithelial layer together
- porous to allow nutrients through
- tissue attached to basal surface
- formed by secretions of both epithelium and connective tissue

Question 6

cell surface modifications on epithelial cells

Answer 6

MICROVILLI: increase surface area for absorption or secreation
CILIA: move materials across cell surface

Question 6

describe functions of epithelial tissue

Answer 6

protects underlying structures
- acts as a barrier (skin)
- filter (kidney)
- secretes substances (pancreas)
- absorbs substances (lining of SI)

Question 7

difference between cilia and microvili

Answer 7

microvilli stationary: larger surface area
cilia move (things along cells)

Question 8

classification of epithelium

Answer 8

NUMBER OF LAYERS OF CELLS
- SIMPLE: one layer, all contact basement membrane
- STRATIFIED: 2+ layers, only bottom touches basement membrane
- PSEUDOSTRATIFIED: appears stratified, but all cells contacts basement membrane, not all contact apical surface

CELL SHAPE ON APICAL SURFACE
- SQUAMOUS: flat, scale-like
- CUBOIDAL: roughly equal hight and width
- COLUMNAR: taller than wide

Question 9

Name functional characteristics of epithelial classifications

Answer 9

SIMPLE: allows diffusion of gasses, filtration of blood, absorption
STRATIFIED: protection (against abrasion, skin)
PSEUDOSTRATIFIED: modification of simple, so allows diffusion

SQUAMOUS: allows diffusion, acts as filter
CUBOILDAL + COLUMNAL: secretion or absorption. May include include GOBLET CELLS that produce and secrete mucus

Question 10

Epithelium types

Answer 10

SIMPLE
- squamous
- cuboidal
- columnar
STRATIFIED
- squamous (nonkeratinized, keratinized)
- cuboidal (very rare)
- columnar (very rare)
PSEUDOSTRATIFIED
- columnar
TRANSITIONAL
- roughly cuboidal to columnar

Question 11

structure, location, function and example of simple squamous epithelium

Answer 11

STRUCTURE
- single layer of flat cells
LOCATION
- blood vessel lining (endothelium), alveoli of lungs, Bowman’s capsule of kidney, lining of serous membrane
FUNCTION
- diffusion, filtration, secretion
EXAMLPE: peritoneum

Question 12

structure, location, function and example of simple cuboidal epithelium

Answer 12

STRUCTURE
- single layer of cuboidal cells
LOCATION
- kidney tubules, glands and their ducts, surface of ovaries
FUNCTION
- absorption and protection
EXAMPLE: tubules of kidney

Question 13

structure, location, function and example of simple columnar epithelium

Answer 13

STRUCTURE
- single layer of columnar cells. some have cilia or microvilli
LOCATION
- glands, bronchioles, uterus, uterine tubes, stomach, intestine, gallbladder, ventricles of brain
FUNCTION
- movement of particles out of bronchioles, movement of oocytes in uterine tubes, secretion by glands in stomach and intestine, absorption by cells of intestine
EXAMPLE (nonciliated): lining of small intestine
EXAMPLE (ciliated): uterine tube

Question 14

structure, location, function and example of pseudostratified columnar epithelium

Answer 14

STRUCTURE
- all cells reach basement membrane. almost always ciliated with goblet cells
LOCATION
- lining upper respiratory tract (ciliated), urethra (nonciliated)
FUNCTION
- synthesize and secrete mucus, move fluid that contains foreign particles, absorption and protection
EXAMPLE: lining of trachea

Question 15

goblet cells

Answer 15

• mucus producing cells most likely found near ciliated cells

Question 16

structure, location, function and example of stratified squamous epithelium

Answer 16

STRUCTURE
- multiple layers of cells that are cuboidal in the basement layer and progressively flatten towards the surface
LOCATION
- keratinized: skin
- nonkeratinized: mouth, throat, esophagus, anus, vagina
FUNCTION
- protection against abrasion
EXAMPLE
- nonkeratinized: vagina, outer layer has fluid
- kertinized: skin, outer layer is dead

Question 17

how are stratified epithelial tissues classified?

Answer 17

based on cell types on apical (top) surface

Question 18

difference between nonkeratinized and keratinized squamous cells

Answer 18

nonkeratinized: moist, lacks keratin protein
keratinized: not moist

Question 19

structure, location, function and example of transitional epithelium

Answer 19

STRUCTURE
- stratified. cells change shape depending on distension of the organ
LOCATION
- lining of urinary system
FUNCTION
- accommodates fluctuations in fluid volume in an organ or tube; protection against caustic effects of urine
EXAMPLE: urinary system
- layers can stretch and change depending on amount of fluid
- multiple layers protect against properties of urine

Question 20

difference in function between pseudostratified and simple columnar epithelium

Question 21

What is a gland? What are the two types of glands and how do they function?

Answer 21

single cell or mass of epithelial cells adapted for secretion

Two types:
ENDOCRINE
- no open contact with exterior, no ducts, produce hormones
- follicle releases hormones into extracellular space to then be taken up by the body
EXOCRINE
- open contact maintained with exterior, ducts (sweat glands, oil grand, mammary glands that produce milk)
- layer of epithelial cells produces a fluid that will exit body via a duct