Epithelial Tissue

Question 1

What is Epithelial Tissues function?

Answer 1

• Cover body surface
• Lines hollow organs, cavities and ducts
• Forms the glands if the body

Question 2

How is Epithelial Tissue arranged?

Answer 2

Arranged in continuous sheets as single or multiple layers and is held together by different cell junctions

Question 3

Name the five main cell junctions that Epithlial Tissue is held together by

Answer 3

• Tight junctions
• Adheren junction
• Gap junction
• Desmosomes
• Hemidesmosomes

Question 4

Name the three surfaces of Epithelial cells

Answer 4

• Apical
• Lateral
• Basal

Question 5

What makes up the cytoskeleten?

Answer 5

Microfilaments, Actin filaments and Intermediate filaments

Question 6

Tight junctions function?

Answer 6

They are individual sealing strands, sewn together by different molecules, main ones being claudins and occludins. These form an important seal between us and the outside world

Question 7

Adherens junction function?

Answer 7

Holds two cells together but leaves a can called Cadherin. These junctions prevent cell separation from tension forces such as contractions

Question 8

Desmosomes function?

Answer 8

It has a gap, this gap is too called Cadherin and it binds to desmoplakin. It links the cell surface to keratin. These junctions bind muscle cells

Question 9

Gap junction function?

Answer 9

A direct connection between cells, made up of 6 connexin proteins and form a hemichannel of connexon. They form little tunnels between cells. Very important for coordination of cardiac contraction.

Question 10

Hemidesmosomes function?

Answer 10

Connect epithelia to basement membrane, links keratin to basement membrane. The linker protein is called integrin and it binds to another protein called laminin and this stops cells from sliding all around

Question 11

All epithelia overlay a basement membrane, made of two parts, what are they?

Answer 11

Basal lamina - contains collagen, laminin and other proteoglycans and glycoproteins

Reticular lamina - Made by the underlying connective tissue called fibroblasts. Contains collagen and fibronectin

Question 12

Describe simple squamous epithelium

Answer 12

• Most delicate kind
• Located where there is filtration or diffusion or secretion
• These are single layered squished cells
• The specialised subtypes are Mesothelium and Endothelium

Question 13

Describe simple cuboidal epithelium

Answer 13

• Located where there is secretion and absorption
• They are cuboidal boxes and their specialised subtypes are Nil

Question 14

Describe Simple columnar epithelium

Answer 14

• Rectangular and elongated, quite big cells
• They have more organelles
• Two major subtypes are non-ciliated and ciliated, see slides for the specifics on both
• Can either have cilia or microvilli

Question 15

Describe Stratified squamous epithelium

Answer 15

• Cuboidal or columnar, very thin as they are less active cells.
• Located where mechanical or chemical stress is severe.
• The specialised subtypes are keratinised and non keratinised
• Keratinised would be skin and Non keratinised would be mouth, throat, anus, vagina e.t.c

Question 16

Pseudostratified columnar epithelium

Answer 16

• Appears to have lots of layers but that’s not the case. - All cells contact the basement membrane but not all reach the apical surface
• The specialised subtypes are either ciliated or non ciliated

Question 17

Where do exocrine glands secrete?

Answer 17

Into ducts

Question 18

Where do endocrine glands secrete?

Answer 18

Into blood