Lecture 2: Cell junctions and Epithelial tissue

Question 1

What is the structure of a tight junction: what proteins are in it

Answer 1

weblike transmembrane proteins made of claudins and occludins fuse together adjacent cell surfaces

Question 2

What is the structure of an adherens junction; what are its components

Answer 2

Plaque- a dense layer of proteins is the belt. It is connected to the micofilament actin. Catenins link actin to cadherins which are transmembrane glycoproteins forming the finger belt buckle across intercellular space.

Question 3

What are tight junctions good at

Answer 3

stopping the leakage of fluids.

Question 4

What are adherins junctions good at

Answer 4

resist separation during contracile activities such as moving food in the intestine

Question 5

What is the structure of a desmosome; what are its components

Answer 5

Made from a semicircle plaque that connects to intermediate filaments made of keratin across from one side of the cell to the other. Two cells are linked together by glycoprotein cadherins

Question 6

What is the structure of a hemidesmosome; what are its components

Answer 6

one semi circle plaque that links the transmembrane glycoprotein integrin to intermediate keratin filaments. Integrin attach to protein laminim in the basement membrane.

Question 7

What are desmosomes good at

Answer 7

preventing epidermal cells from separating under tension and cardiac muscle cells under contraction

Question 8

What are hemidesmosomes good at

Answer 8

anchoring the cell to the basement membrane

Question 9

What is the structure of a Gap junction; what are its components

Answer 9

6 conneXINs (membrane protein) form one hemichannel. This hemichannel is called an connexON. 2 connexons are tiny fluid filled tunnels that connect neighbouring cells.

Question 10

What are gap junctions good for

Answer 10

Allow passage of ions, small molecules, transferring nutrients and wastes, nerve impulses- communication between cells.

Question 11

What are microfilaments made of

Answer 11

actin

Question 12

What are intermediate filaments made of

Answer 12

keratin

Question 13

What are the two parts of the basement membrane and who secretes them

Answer 13

Basal lamina secreted by epithelial cells and reticular lamina secreted by fibroblasts

Question 14

Does epithelial tissue contain nerves and blood vessels

Answer 14

nerves yes, but it is avascular

Question 15

What materials does the basal lamina contain

Answer 15

collagen, laminim, proteoglycans/glycoproteins

Question 16

What materials does the reticular lamina contain

Answer 16

fibrous proteins- fibronectin, collagen.

Question 17

Simple squamous epithelium has 3 functions and two locations. Tell me

Answer 17

used for filtration, diffusion and slippery surface where secretion is. Found as endothelium (lining cardiovascular/ lymphatic system) and mesothelium (lining peritoneum, pleura, pericardium cavities)

Question 18

Simple cuboidal epithelium have two functions and 4 locations. Tell me

Answer 18

Involved in secretion and absorption so lines many ducts. Locations are kidney tubules, posterior of retina, thyroid and pancreas

Question 19

What types of epithelial cells can be cilliated

Answer 19

simple columnar and pseudostratified

Question 20

What types of epithelial cells can be microvillied and what is another name for this

Answer 20

simple columnar cells can have a ‘brush border’

Question 21

What epithelial cells have goblet cells

Answer 21

Both types of simple columnar but only cilliated pseudostratified columnar.

Question 22

Where are non cilliated simple columnar cells found and why are they there?

Answer 22

lining the gastointestinal tract, gall bladder and gland ducts because they have higher rates of absorption, can lubricate linings

Question 23

Where are cilliated cells found and why are they there

Answer 23

simple columnar are found in spinal cord, bronchioles, fallopian tubes and sinuses.
pseudostratified columnar found lining the upper respiratory tract. This is because cillia can beat in unision to propel foreign stuff out or move eggs.

Question 24

Where are keratinised and non keratinised stratified squamous epithelium found

Answer 24

Keratinised is the superficial layers of skin, non keratinised is where penises go including the oesophagus.

Question 25

Where are stratified cuboidal cells found

Answer 25

they are fairly rare, found in male urethra, oesophageal glands and sweat gland ducts.

Question 26

Where are stratified columnar cells found

Answer 26

large excretory ducts, anal mucous membrane, urethra, eye. squishy and gross

Question 27

What are the main functions of basic stratified cells

Answer 27

protection - against wear and tear and microbes

with limited secretion and absorption.

Question 28

What is the structure, function and location of stratified transitional cells

Answer 28

it goes from relaxed rounded cuboidal stratified to stretched flattened squamous allowing urinary organs (mainly bladder) to hold variable amounts of liquid and maintain protective lining without rupturing.

Question 29

What does pseudo stratified mean

Answer 29

All cells are in contact with the basement membrane but not all of them reach the apical surface of tissue.

Question 30

What is the function and location of non cilliated pseudostratified columnar cells

Answer 30

absorption and protection; lining larger ducts of many glands, epididymus and male urethra

Question 31

What are the two main types of glandular epithelium and how are they different

Answer 31

Exocrine secrete their products into ducts that empty onto the surface of a covering and lining epithelium and Endocrine secretes hormones that enter the interstitial fluid and directly diffuse into the bloodstream.

Question 32

How are multicellular exocrine glands classified and what are the names under each classification

Answer 32

1. Whether the duct is branched or not.
   Simple is no branches. Compound is branched.
2. The shape of the duct
   tubular, branched tubular = one tear drop, clover tear drops. Coiled is a pig tail. Acinar/alveolar is rounded berry drop. Tubuloacinar is a mix.

Question 33

What are the three compound glands

Answer 33

compound tubular, acinar and tubuloacinar.

Question 34

What is holocrine secretion

Answer 34

secretory product is accumulated in the cytosol and then the cell ruptures. eg. sebaceous glands

Question 35

What is apocrine secretion

Answer 35

secretory product accumulates on the apical surface of the cell and then that part pinches off in exocytosis to release the product.

Question 36

What is merocrine secretion

Answer 36

secretory product is synthesised in RER, processed and packaged at the Golgi and sent to be released from the cell in secretory vesicles via exocytosis.