Epithelial Tissue

Question 1

Name the types of epithelial tissue

Answer 1

Simple squamous
Simple cuboidal
Simple columnar
Stratified squamous
Stratified cuboidal
Stratified columnar
Pseudo-stratified columnar
Transitional

Question 2

Describe simple squamous tissue?

Answer 2

Thin and flat with flat disc nucleus
Permeable
^ facilitate diffusion, only possible function
Found in alveoli, glomerulus, endothelium and mesothelium

endothelium - cells that line the interior surface of blood vessels
mesothelium - membrane composed of simple squamous epithelium that forms the lining of several body cavities: the pleura (thoracic cavity), peritoneum (abdominal cavity including the mesentery), mediastinum and pericardium (heart sac)

Question 3

Describe simple cuboidal tissue?

Answer 3

Cube with a spherical nucleus
Secrete and absorb
Found in nephron lining, thyroid, salivary glands, ovary surface

Question 4

Describe simple columnar tissue?

Answer 4

Column shaped, elongated nucleus and contain cilia that help movement of mucous
Secrete digestive enzymes and absorb digested food
Found in stomach, intestines and endometrium (the inner lining of the uterus)

Question 5

Describe stratified squamous tissue?

Answer 5

Multiple layers of flat cells
keratinized or not
Only available function is protection
Keratinized tissue found in skin, dead layers of cells that are expendable
Non keratinized found in moist linings: mouth, oesophagus, vagina

Question 6

Describe stratified cuboidal tissue?

Answer 6

Multiple layers of cuboidal
Secretion + Reabsorption
Found in mammary glands

Question 7

Describe stratified columnar tissue?

Answer 7

Multiple layers of columnar
Protection + secretion
Urethra

Question 8

Describe pseudo-stratified columnar tissue?

Answer 8

‘Multiple’ looking layers of cells. ALL connect with basement membrane
Secretion
Large glands like sperm carrying ducts and trachea

Question 9

Describe transitional tissue?

Answer 9

Resemble both stratified squamous and stratified cuboidal
Has elastic properties
Urethra, urinary bladder (stretch)

Question 10

What are the 6 functions of epithelial tissue?

Answer 10

Protection
Absorption
Filtration
Excretion
Secretion
Sensory

Question 11

Example of protection?

Answer 11

Skin epidermis - Stratified squamous e.g.

Gut lumen

Question 12

Example of Absorption?

Answer 12

Intestines - absorb nutrients

Question 13

Example of filtration?

Answer 13

Respiratory tract - filters air

Question 14

Example of excretion?

Answer 14

Skin - sweats and oils

Question 15

Example of secretion?

Answer 15

All glands are made of epithelial tissue - thyroid, pineal gland

Question 16

Example of sensory?

Answer 16

Ear and nose

Question 17

Describe a tight junction

Answer 17

Forms the continuous intercellular barrier between epithelial cells, which is required to separate tissue spaces and regulate selective movement of solutes across the epithelium

Question 18

Describe an adhesion belt

Answer 18

The adhesion belts are directly apposed in adjacent epithelial cells, with the interacting plasma membranes held together by the cadherins that serve here as transmembrane adhesion proteins

Question 19

Describe a desmosome protein

Answer 19

Desmosomes are intercellular junctions that provide strong adhesion between cells. Because they also link intracellularly to the intermediate filament cytoskeleton they form the adhesive bonds in a network that gives mechanical strength to tissues

Question 20

What is the difference between an adhesion belt and a desmosome?

Answer 20

Adhesion belts are involved in dynamic cell interactions in development and disease, whereas desmosomes are responsible for strong adhesion in epithelia and cardiac muscle

Question 21

Describe a hemidesmosome

Answer 21

Similar to desmosomes but anchor cell to basement membrane

Stop cells lifting off

Question 22

Describe a gap junction

Answer 22

Small pores / tubes
Allow chemical communication between cells
Contains connexons (made of connexins)

Question 23

Describe a connexon

Answer 23

Also known as a connexin hemichannel, is an assembly of six proteins called connexins that form the pore for a gap junction between the cytoplasm of two adjacent cells. This channel allows for bidirectional flow of ions and signaling molecules

Question 24

What are the cell junction transmembrane glycoproteins?

Answer 24

Adherin + Integrin

Adherin: Part of the adhesive belt; Attaches to actin microfilaments on the cytoskeleton; binds adjacent cells

Integrin: attaches to actin microfilaments on the cytoskeleton; Within hemidesmosomes, attach cell to basement membrane

Question 25

Describe the hypodermis

Answer 25

Mainly adipose tissue
Subcutaneous fat
Makes sense

Question 26

Describe the dermis

Answer 26

Vascularised
Strong + flexible
Innervated with
Meissners capsules - Touch receptors
Pacinian capsules - Pressure receptors
Nutrients diffuse through it into epidermis

Question 27

Describe the epidermis

Answer 27

Contains:
Keratinocytes (keratin)
Melaninocytes (melanin)
Langerhans cells (epidermal phagocytes)
Merkel cells (touch receptors)

Question 28

What is the difference between endocrine and exocrine glandular epithelia?

Answer 28

Endocrine epithelia
Ductless
Secrete internally e.g. Thyroid

Exocrine epithelia
Secrete externally e.g. Sweat glands