Epithelia

Question 1

Name the 4 fundamental tissue types. Name the function of each.

Answer 1

• connective tissue = supportive/packing
• epithelium = lining/barrier
• muscular = contractile
• nervous = Action potential/transmission

Question 2

Define the term “epithelia”.

Answer 2

Epithelia is a cohesive sheet of epithelial cells that separate the external environment from the internal environment of the body.

Question 3

What’s the term for internal facing epithelial tissue?

Answer 3

Endothelium

Question 4

What’s the term for external facing epithelial tissue?

Answer 4

Epithelium

Question 5

What are the 3 types of cells that epithelia are derived from?

Answer 5

ectoderm, mesoderm, endoderm

Question 6

Connective tissue is only derived from ——.

Answer 6

Mesoderm

Question 7

Give examples of external-facing surfaces and internal-facing surfaces made from epithelial cells.

Answer 7

Internal facing - Blood vessels
External facing - Mouth, Bladder

Question 8

Name two surfaces found in most epithelia.

Answer 8

Free surface and Basal surface

Question 9

What is the function of the basal membrane?

Answer 9

The function of the basal membrane is to separate the epithelia from all other tissues including its own blood supply.

Question 10

Name the 5 functions of epithelia—name examples where each of the functions works.

Answer 10

1. Barrier
   skin prevents water loss and entry
2. Protection
   outer layer of skin and oral cavity
3. secretion
   sweat glands
4. absorption
   gut epithelia
5. permitting the passage of substances
   Pulmonary alveoli diffusion of O2 and CO2

Question 11

Name and describe the 3 classifications of epithelia by layers.

Answer 11

1. Simple epithelia
   one layer of cells all in contact with the basal membrane
2. Stratified epithelia
   two or more layers of epithelial cells where only the lowest layer is in contact with the basement membrane
3. Pseudostratified epithelia
   simple epithelia that looks stratified but all the cells are in contact with the basement membrane.
   the nuclei are at different levels.

Question 12

Name the 3 classifications by shape.

Answer 12

1. squamous
2. cuboidal
3. columnar

Question 13

Describe the appearance of simple squamous epithelium.

Answer 13

A single layer of very flat cells
minimal cytoplasm which is nearly invisible

Question 14

Name 3 functions of simple squamous epithelium. Give examples.

Answer 14

1. Diffusion
   eg: pulmonary alveoli
2. Filtration
   eg: Bowman’s capsule in the kidney
3. Lining
   eg: Heart (endocardium), Blood Vessels (Endothelium)

Question 15

Describe the appearance of simple cuboidal epithelium.

Answer 15

the cell height is similar to the cell width
rounded,centred nuclei

Question 16

Name 2 functions of simple cuboidal epithelium.

Answer 16

Active transport
Facilitated diffusion (Secretion and Absorption)

Question 17

Name 2 features that some simple cuboidal epithelium may have. Why?
Where are the 2 named features found?

Answer 17

Cillia - To move the mucus over the surface
Microvilli - to increase surface area

Kidney tubules, Choroid plexus(CSF), Lining of ducts of many glands (salivary glands, pancreas and thyroid follicles), respiratory tract

Question 18

What is the choroid plexus?

Answer 18

A network of blood vessels in the ventricles of the brain, producing CSF.Cerebrospinal fluid).

Question 19

Name all the types of epithelium that may have cilia or microvilli. *

Answer 19

Simple cuboidal epithelium, simple columnar epithelium, pseudostratified columnar

Question 20

Describe the appearance of simple columnar epithelium.

Answer 20

Cell height is greater than cell width
(in practical at least twice the height)
Elongated (oval) nuclei towards the base of the cell

Question 21

Name 2 features of some columnar epithelium.

Answer 21

Cilia
Microvilli

Question 22

Features of simple columnar epithelium

Answer 22

Contains numerous organelles to support complex functions (secretion and absorption)

Question 23

Where is simple columnar epithelium found?

Answer 23

Found in some glands
bronchioles of lungs
fallopian tubes
small and large intestines

Question 24

What is stratified squamous epithelium?

Answer 24

Stratified squamous epithelium is a type of tissue composed of multiple layers of cells with a cuboidal base layer that gradually flattens towards the surface.

Question 25

What is the function of stratified squamous epithelia?

Answer 25

Stratified squamous epithelium protects against abrasion, caustic substances, water loss and infection

Question 26

State the features of unkeratinised stratified squamous epithelia. Give an example

Answer 26

Moist Oxygen is available to it All cells are alive eg; pharynx

Question 27

State the features of keratinised stratified squamous epithelia. Give an example

Answer 27

Surface layer - dead, dried, scale like flakes eg: skin epidermis

Question 28

Describe the appearance of pseudostratified columnar epithelium Name example of where it could be found.

Answer 28

All cells in contact with BM Not all cells have a free surface Appear stratified because nuclei are at different levels mostly ciliated and associated with mucus producing cells - goblet cells it synthesises, secretes and moves mucus on the epithelium free surface found in nasal cavity and bronchi

Question 29

Name all the types of epithelia studied in this section

Answer 29

simple squamous simple cuboidal simple columnar stratified squamous pseudostratified columnar

Question 30

What is transitional epithelium and what is its unique characteristic?

Answer 30

Transitional epithelium is a specialized stratified epithelium. It can be stretched without loss of function

Question 31

Where does transitional epithelium typically line?

Answer 31

Transitional epithelium lines cavities that expand, such as the urinary bladder.

Question 32

What is the function of transitional epithelium?

Answer 32

The primary function of transitional epithelium is to enable tissue to expand and contract. in the case of the urinary bladder, it is to protect underlying tissue from corrosive urine.

Question 33

How does transitional epithelium appear in its unstretched state?

Answer 33

Five or more layers of cuboidal or columnar cells Often cuboidal, with a ‘dome-shaped free surface – each cell overlaps underlying cells Middle layers are composed of round/pear-shaped cells Bottom layer cubical – cone-shaped cells that rest on an incomplete basement membrane

Question 34

How does transitional epithelium appear in its stretched state?

Answer 34

In its stretched state, - the number of cell layers decreases - the cells become more flattened, transitioning from cuboidal to squamous in shape.

Question 35

What are the two types of glandular epithelium?

Answer 35

Endocrine and exocrine glands

Question 36

What is the difference between endocrine and exocrine glands?

Answer 36

Endocrine glands are ductless and secrete their products directly into the bloodstream Exocrine glands secrete their products to the exterior of the body through ducts.

Question 37

How are exocrine glands classified?

Answer 37

Exocrine glands can be classified based on their structure or method of secretion.

Question 38

What are the two types of secretory units in exocrine glands?

Answer 38

The two major shapes of secretory units in exocrine glands are tubular and globular shaped.

Question 39

What are some examples of modified epithelium and their functions?

Answer 39

Germinal epithelium: It produces gametes in the ovaries and testes. Sensory epithelium: Found in the retina and taste buds, it receives and conveys stimuli. Myoepithelium: Located in salivary glands and their ducts, these cells contain actin and myosin filaments and contract to release secretory products from the glands. Pigmented epithelium: Present in the retina, the cells contain colored melanin pigment granules. Ependymal epithelium: It forms the lining in the cavities of the brain and spinal cord, and the cells are ciliated. Cuticular epithelium: It secretes the cuticle, which is the tough resistant non-cellular protective layer of the body in invertebrates.

Question 40

Define gland

Answer 40

One or more cells that synthesise or secrete an aqueous fluid.

Question 41

Exocrine glands are connected to surface epithelia by ducts. name the 2 types and how they're connected.

Answer 41

Simple duct: each duct is connected to a single secretory unit Compound duct: numbers of ducts from secretory unit unite to form a large duct