Lecture 12 - Exocrine & Specialised Glands

Question 1

Where are the parotid glands located?

Answer 1

Underneath the skin, the top of the glands are at the head of the mandible, the bottom is 2cm below the angle of the mandible

Question 2

What colour does the parotid gland stain and why?

Answer 2

Purple as it is a serous gland. the pale structure is the striated duct of the gland, surrounded by simple columnar epithelial cells.

Question 3

Where does saliva pool due to a blockage in the parotid gland that ultimately leads to swelling?

Answer 3

In the striated duct, as infections of the gland cause a blockage here which fills with saliva from acinar cells.

Question 4

Where is the submandibular gland located?

What are the 2 parts and what are they separated by?

Answer 4

• Underneath the mandible and jaw

- Superficial and deep - separated by mylohyoid muscle

Question 5

The 3 salivary glands are parotid, submandibular and sublingual - which ones are serous, mucous or both?
How can this be used to tell them apart on a H&E stain?

Answer 5

• Parotid = serous. Submandibular = Mostly serous, some mucous. Sublingual = Mucous
• Serous stains purple and mucous stains white, so purple = parotid, mixed = submandibular and white = sublingual

Question 6

How is salivary secretions stimulated/regulated?

Answer 6

Via ANS supply to the salivary glands (neural ONLY)- BOTH sympathetic and parasympathetic increase saliva secretion.

Question 7

What is the difference in saliva secretions when stimulated by sympathetic and parasympathetic innervation?

Answer 7

Parasympathetic = Watery saliva rich in enzyme 
Sympathetic = Small, thick secretions rich in mucous

Question 8

What 2 vessels supply blood to the liver and how much does each contibute?
Is the blood from each vessel deoxygenated or oxygenated?

Answer 8

1) Hepatic portal vein (70-75%) - deoxygenated
2) Hepatic artery (25-30%) - oxygenated

NB: HPV also supplies the spleen, stomach and intestines.

Question 9

What is the structure called that blood is fed into when the HPV and hepatic artery come together?

Answer 9

• A sinusoid tube (irregularly shaped)

Question 10

What are the large gaps in sinusoidal cells called and why do they have them?

Answer 10

• Sinusoids
• So that cells can squeeze through the large gaps and enter the tissues directly, which is important for places such as the liver, spleen, bone barrow and lymph nodes.

Question 11

What are the three main cells of the liver?

Answer 11

1) Hepatocytes
2) Kupffer cells
3) Ito (stellate) cells

Question 12

What are Kupffer cells and what is their function in the liver?

Answer 12

Kupffer cells are specialised macrophages that form part of the sinusoidal lining. They trap and phagocytose any aged erythrocytes missed by the spleen (or take over this role after splenectomy) - Erythrocyte typically last 120 days/4months

Question 13

What are stellate (ito) cells?

What happens to stellate cells in liver cirrhosis?

Answer 13

• Stellate cells are the major storage site of vitamin A (in their cytoplasmic vacuoles) but also respond to hepatic injury.
• They lose their Vit A storage ability, differentiate into myofibroblasts which deposit collagen in the perisinusoidal space and cause liver fibrosis.

Question 14

Which cell constitutes to 80% of the liver cell population?
What is its function?
What organelles do they have in abundance?

Answer 14

• Hepatocytes
• Metabolism, detoxification, protein synthesis + has regenerative ability
• Peroxisomes, free ribosomes, RER, SER, golgi apparatus and glycogen deposits

Question 15

what are the major functions of the liver?

Answer 15

1) Storage - iron, lipid soluble vitamins (A,B12,K), glycogen
2) Anabolism - more than 60% of body proteins, e.g.: albumin, enzymes, lipid carrier proteins, AA’s
3) Catabolism - of drugs, hormones, Hb, poisons/toxins
4) Bile production - through ducts into the gall bladder which emulsifies fats and assists in Vit K absorption from the SI
5) Production and modification of hormones

Question 16

What are the 4 main ways in which the liver is regulated?

Answer 16

1) Autocrine signalling via VEGF - acts on own receptors inside cell
2) Paracrine signalling via succinate - acts on adjacent cells
3) Endocrine signalling via GH - Acts long distance
4) Intracrine signalling - stimulates production of APO A1 which increased HDL in blood

Question 17

The liver is the largest exocrine and endocrine gland. What are its exocrine and constitutive & regulatory endocrine secretions?
The pancreas also shows both endocrine & exocrine functions, why is the liver different from the pancreas?

Answer 17

• Exocrine = Bile - which is passed into the gall bladder and stored (eventually leaked into the duodenum) - emulsifies fats and assists vit K absorption from the duodenum.
• Endocrine (regulatory) - IGF1
• Endocrine (constitutive) - Albumin
• Unlike the pancreas, the same cell (hepatocyte) executes both the exocrine and endocrine functions.