1.02 - Epithelium

Question 1

What is glandular epithelium?

Answer 1

Aggregates of cells, specialised to secret or excrete materials not related to their own metabolic needs

Question 2

What are the two classifications of epithelium?

Answer 2

Simple (Single Layer)

Stratified (Two or more layers)

Question 3

What are the types of Simple epithelium?

Answer 3

Squamous
Cuboidal
Columnar
Pseudostratified

Question 4

What are the types of stratified epithelium?

Answer 4

Squamous
Cuboidal
Columnar
Transitional

Question 5

Describe Simple Squamous Epithelium

Answer 5

Single layer of flat cells
Found at interfaces
Functions:
Diffusion - Lungs for gas exchange between air spaces and blood, Blood vessels for exchange of waste and nutrients between blood and surrounding tissue
Filtration - Kidney - plasma in glomeruli to produce urine
Secretion - lining of pleural, pericardial, peritoneal cavities (mesothelium), produces a lubricating substance to reduce friction

Question 6

Describe Simple Cuboidal Epithelium

Answer 6

Single layer or square cells
Functions:
Absorption: Lining of ducts of kidney to move substances in and out of the kidney tubule.
Secretory: Lining of ducts of salivary glands and pancreas

Question 7

Describe Simple Columnar Epithelia

Answer 7

Single layer of cells taller than they are wide (nucleus located towards the base)
Can be ciliated or non-ciliated
Functions:
Absorption
Secretion
Protection

Question 8

Describe Simple Columnar Ciliated Epithelium

Answer 8

Single layer of columnar cells with cilia
Cilia are short extensions of cytoplasm and cell membrane found on the free surface.
Involved in secretion of mucus and other substances and in moving luminal contents, e.g. fallopian tubes and bronchi.

Question 9

Describe Simple Columnar Epithelium with Microvilli

Answer 9

Single Layer of Columnar cells with Microvilli.
Microvilli are closely bunched tiny projections from the free surface of cells.
Core of actin filaments.
Can have a layer of Glycocalyx on the free surface.
Function:
Absorption: Small & Large Bowel (glycocalyx located here)
Secretion: Stomach and Uterus - Secretion of mucus, enzymes and other substances

Question 10

What is glycocalyx?

Answer 10

An extracellular polymeric material made up of lipids, proteins with carbohydrate side chains and contains within it enzymes for digestion

Question 11

Describe Simple Columnar Epithelium with Goblet Cells

Answer 11

Single layer of Columnar cells with Goblet Cells
They are modified columnar cells that synthesise and secrete mucous
At the apex of the cell are mucigen granules with the nucleus and other organelles located at the base
Function:
Secretion - Small and large intestine

Question 12

Describe Pseudostratified Ciliated Columnar Epithelium

Answer 12

A single layer of cells that appear as two or more layers
All cells rest on basement membrane but nuclei are on different levels
Function: Secretion, Lubrication, Protection, Transportation
Location: Respiratory epithelium of bronchus

Question 13

Describe Stratified Squamous Epithelium

Answer 13

2 or more layers of squamous cells
Function: Mainly protection - resist abrasion
Transition from cuboidal basal layer to flattened surface layer
Can be keratinising or non-keratinising

Question 14

What is Keratin and what is it’s function?

Answer 14

It is a tough protective protein which prevents water loss, is resistant to friction and repels bacteria.

Question 15

Where can Keratinised and Non-Keratinised Stratified Squamous Epithelium be found?

Answer 15

Keratinised: Epidermis of the skin, masticatory mucosa

Non-keratinised: Lines surfaces subjected to abrasion - lining of the mouth, oesophagus, tongue and vagina

Question 16

What are desmosomes and where are they found?

Answer 16

A type of intercellular junction that are characterised as dense regions of attachment between epithelial cells that contribute to strong bonds between cells
Found between squamous epithelium

Question 17

Describe Stratified Cuboidal Epithelium

Answer 17

2 or 3 layers of cuboidal cells
Robust lining
Not much absorption or secretion
Found in the larger ducts of exocrine glands, such as salivary and sweat glands.

Question 18

Describe Stratified Columnar Epithelium

Answer 18

Several layers of epithelial cells but surface layer is made of columnar cells
Roles are protection and secretion
Only located in part of the male urethra, portion of the conjunctiva

Question 19

Describe Stratified Transitional Epithlium

Answer 19

Stratified epithelium
Intermediate between stratified cuboidal and stratified squamous
4 or 5 cells layers
Basal cells are cuboidal, surface large and rounded
Function: Protective and Distensible
Location: Bladder - stretch and copes with toxicity of urine

Question 20

What are the three types of glands?

Answer 20

Goblet cells (unicellular)
Exocrine (Multicellular) - release their products on to free surface of skin or open cavities of body - e.g. sweat and salivary glands
Endocrine (multicellular) - their product (called hormones) are secreted directly in to the blood - e.g. islet cells of pancreas

Question 21

What are the functions of Epithelium?

Answer 21

Diffusion - alveoli of lungs
Barrier - skin
Containment - endothelium - blood brain barrier
Excretion - Collecting ducts of kidney
Secretion - breast (milk), skin (sweat), GIT (mucous), pancreas (hormones)
Absorption - small intestine
Contractility - bladder, salivary glands
Sensation - taste buds, olfactory epithelium