Epithelium

Question 1

What are tissues?

Answer 1

A group of closely associated cells that perform related functions and are similar in structure.
-Between cells: non living extracellular material

Question 2

What are the 4 basic types of tissue?

Answer 2

• epithelium -covering
• connective tissue- support
• muscle tissue - movement
• nervous tissue - control

Question 3

What is epithelium?

Answer 3

Sheet of cells that covers a body surface or lines a body cavity; also form most of the body’s glands

Question 4

What are the roles and functions of epithelia?

Answer 4

Roles: as interfaces and as boundaries

Functions:

• protection
• sensory reception
• secretion
• absorption
• ion transport
• filtration
• formation of slippery surfaces for movement.

Question 5

What are the special characteristics of epithelia?

Answer 5

• cellularity
• specialized contacts cell junctions
• polarity
  
  • free upper (apical) surface
  • Lower (basal) surface contributing basal lamina to basement membrane

-support by connective tissue

• Avascular but innervates
  
  • without vessels
  • with nerve endings

-regeneration

Question 6

How can epithelia be classified according to shape?

Answer 6

Squamous- wider than tall (flattened appearance)

Cuboidal- as tall as wide

Columnar- taller than wide

Question 7

How can epithelia be classified according to thickness?

Answer 7

Simple- one cell layer

Stratified- more than one layer of cells (which are named according to the shape of the cells in the apical layer)

Question 8

Which epithelial cell classification is important for diffusion?

Answer 8

Squamous

Question 9

Which epithelial classification is important for secretion and absorption ? Why ?

Answer 9

Cuboidal and columnar

Larger cells because of machinery of production, packaging, and energy requirements

Question 10

What are the 6 type of epithelial tissue?

Answer 10

• simple squamous epithelium
• simple cuboidal epithelium
• simple columnar epithelium
• pseudostratified epithelium
• stratified squamous epithelium
• transitional epithelium

Question 11

Where would simple squamous epithelium be located?

Answer 11

Simple squamous epithelium may be located at sites of rapid diffusion, such as:

• lining of the lung alveoli
• lining of blood vessels
• in the lining of major body cavities

Question 12

What is endothelium?

Answer 12

A simple squamous epithelium that lines the interior of the circulatory vessels and the heart

Question 13

What is the mesothelium?

Answer 13

Simple squamous epithelium that lines the peritoneal, pleural and pericardial cavities and covers the viscera

Question 14

Which body parts require for simple cuboidal epithelium?

Answer 14

Ducts of glands

• small ducts - simple cuboidal epithelium
• large ducts - stratified cuboid
  
  • N.B. deeper cells may also be cuboidal

Pigmented layer of retina

Surface of Ovary

Follicular cells of thyroid

Question 15

Which body parts use simple columnar epithelium?

Answer 15

Some usual locations

• gall bladder
• epithelium of digestive system
• epithelium of uterus
• uterine glands

Question 16

What is pseudostratified epithelium?

Answer 16

Appears stratified, typically with nuclei located in at least two more-or-less distinct levels. But in fact every cell rests on the basement membrane, so the epithelium is technically “simple”, in spite of appearances

Question 17

Where is pseudostratified epithelium found?

Answer 17

Found lining the respiratory system and in the excretory ducts of the male reproductive system

Question 18

What kind of pseudostratified epithelium is in the respiratory system?

Answer 18

Pseudostratified epithelium with goblet cells

Question 19

What are the stratified squamous epithelium?

Answer 19

Surface cells are squamous

Deeper cells may be cuboidal in nature and can regenerate

Question 20

What is the usual function of stratified squamous epithelium?

Answer 20

Usually protective in function. The outer layer may or may not be keratinized

Also used where transport is important

Question 21

Where are the stratified squamous epithelium found?

Answer 21

Gastrointestinal tract e.g. oesophagus, anus- non-keratinized

• Vagina - non-keratinized
• Skin - keratinized

Question 22

What are transitional epithelium?

Answer 22

Urothelium

Lines the distensible walls of the urinary tract

Question 23

Glands are formed from

Answer 23

Epithelial cells

Question 24

Describe the functioning of glands

Answer 24

• production and secretion of needed substances
• Aqeous (water-based) products
• the protein product is made in rough ER, packed into secretory granules by Golgi apparatus, released from the cell by exocytosis

Question 25

What the classification of glands ?

Answer 25

Exocrine: external secretion onto body surfaces (skin) or into body cavities Endocrine: secrete messenger molecules (hormones) which are carried by blood to target organs; “ductless” glands By cell count: unicellular or multicellular

Question 26

Give an example of a unicellular exocrine glands

Answer 26

Unicellular: goblet cell scattered within epithelial lining of intestines and respiratory tubes Product: mucin Mucus is mucin and water

Question 27

What is distinctive about multicellular exocrine glands?

Answer 27

Epithelium-walled duct and a secretory unit

Question 28

Give some examples of exocrine gland products

Answer 28

Many types of mucus secreting glands - sweat glands of skin - oil glands of skin - salivary glands of mouth - liver(bile) - pancreas (digestive enzymes) - mammary glands (milk)

Question 29

Describe endocrine glands

Answer 29

Ductless glands - release hormones into extracellular shape - hormones are messenger molecules -Hormones enter blood and travel to specific target organs

Question 30

List the epithelial surface features

Answer 30

- lateral surfaces - basal surfaces - apical surfaces

Question 31

Describe the lateral epithelial cell surfaces

Answer 31

- adhesion - tongue and groove wavy contours - cell junctions

Question 32

Describe the basal epithelial surface

Answer 32

Basal lamina: noncellular sheet of protein together with reticular fibers form basement membrane

Question 33

List the type of cell junctions

Answer 33

- tight junctions - adherents junctions - desmosomes - gap junctions

Question 34

What are the functions of gap junctions?

Answer 34

Allow small molecules to move between cells

Question 35

What are the functions of desmosomes ?

Answer 35

- anchoring junctions | - filaments anchor to the opposite side

Question 36

What are the functions of adherents junctions?

Answer 36

Transmembrane linker proteins

Question 37

What are the function of tight junctions?

Answer 37

Impermeable

Question 38

List the features if the apical features

Answer 38

Microvilli Cilia Flagellum

Question 39

What are cilia?

Answer 39

Whiplike motile extensions of the apical surface membranes

Question 40

What are flagellum?

Answer 40

- long isolated cilium | - only found as sperm in human

Question 41

What are microvilli?

Answer 41

Maximize surface - finger like extensions of the plasma membrane of apical epithelial cells - on moist and mucus secreting epithelium - longest in epithelia that absorb nutrients (small intestine) or transport ions (kidneys)