FORM & FUNCTION (Epithelial Tissues)

Question 1

Characteristics of epithelia:

Answer 1

-exhibit polarity with three domains (apical, basal and lateral)
>function will depend on the features in each domain
-avascular (devoid of blood vessels)
>ends in connective tissue under the epithelium

Question 2

Apical domain: features

Answer 2

-directed to the lumen/external surface
-modifications likely present: cilia, stereocilia or microvilli

Question 3

Microvilli:

Answer 3

-cytoplasmic processes that extend from cell surface
Ex. small intestinal epithelium

Question 4

Stereocilia

Answer 4

-microvilli of unusual length
Ex. inner ear, testis

Question 5

Cilia:

Answer 5

-motile cytoplasmic processes
Ex. respiratory epithelium

Question 6

Lateral domain: features

Answer 6

-makes connections to the adjacent/neighbouring cells and communicates with them
-various types of junctions are present
>tight junctions (barrier function)
>anchoring junctions (mechanical stability)
>communicating junctions (direct communication between cells)
*paracellular pathway

Question 7

Basal domain: features

Answer 7

-basement membrane
-contains basal lamina and lamina lucida
>contain secretions from the epithelial cells (eg. Proteoglycans and collagen: proteins and fibrous material)

Question 8

Basal lamina:

Answer 8

-structural attachment site for overlying epithelial cells and underlying connective tissues

Question 9

Epidermis:

Answer 9

-stratified squamous epithelium (based on the top layer)
-with and without keratin (produced by stratum granulosum)

Question 10

Layers of epidermis:

Answer 10

1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum

Question 11

stratum basale

Answer 11

-uni-layer of stem cells (cubodial)

Question 12

stratum spinosum

Answer 12

-prickle cells

Question 13

stratum granulosum

Answer 13

-produces keratin

Question 14

stratum lucidum

Answer 14

-flattened and tightly packed keratinocytes filled with keratin filaments

Question 15

stratum corneum

Answer 15

-various layers of squamous cells
-secrete the keratin to the top
-no nucleus (‘dying’), will release keratin stored in them

Question 16

Keratinocytes in stratum corneum:

Answer 16

-produces keratin
-when keratin is present on the surface=epithelium is named keratinized

Question 17

Epitheloid tissues:

Answer 17

-tissues that appear epithelial, make contact with adjacent cells, but are devoid of the characteristic free surface

Question 18

Example of epitheloid tissue:

Answer 18

*endocrine organs which develop from typical epithelia, but lost its connection to a surface during development
-pancreatic islet cells
-Leydig cells in testis
-anterior pituitary cells
-adrenal parenchyma cells

Question 19

Why is epithelia so important?

Answer 19

-secretion
-absorption
-transport
-protection
-receptor
*problems with the form and/or function of epithelia lead to diseases

Question 20

Secretion:

Answer 20

-columnar epithelium of gastric glands (enzymes for digestion)

Question 21

Absorption:

Answer 21

-columnar epithelium of small intestine

Question 22

Transport:

Answer 22

-respiratory and olfactory epithelia

Question 23

Protection:

Answer 23

-stratified squamous epithelium of the skin (epidermis)

Question 24

Receptor:

Answer 24

-epithelia of tongue (taste buds) and nasal mucosa (smell)

Question 25

Simple squamous example:

Answer 25

-vascular system
>exchange

Question 26

Simple cuboidal example:

Answer 26

-small ducts of exocrine glands
>absorption and secretion

Question 27

Simple columnar example:

Answer 27

-small intestine and colon
>absorption and secretion

Question 28

Pseudostratified example:

Answer 28

-trachea and bronchial tree
>secretion
>absorption

Question 29

Stratified squamous example:

Answer 29

-epidermis, oral cavity, vagina
>barrier
>protection

Question 30

Stratified cuboidal example:

Answer 30

-sweat gland ducts
>barrier

Question 31

Stratified columnar example:

Answer 31

-largest ducts of exocrine glands
>barrier

Question 32

Transitional example:

Answer 32

-renal calyces, ureters, bladder, urethra
>barrier