Exocrine And Special Glands Flashcards
Where is the parotid gland (serous gland) found? And how are the cells stained using H&E?
- Parotid gland is situated on the side of the head, underneath the skin.
- Parotid glands are serous glands and contain serous acini and stain purple on the H&E because it contains a lot of proteins and mRNA.
- Also contains a lot of alpha amylase, an enzyme which digest starch.
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What is seen on H&E staining of serous acinus?
- Serous acinus nuclei are closer to the basement membrane and they have a lot of secretory vesicles near the apical surface which is near the intra lobular ducts.
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How do you know a duct is a striated duct on a H&E stain ?
- The nuclei aren’t close to the basement membrane.
- The nuclei tend to be closer to the lumen in the striated duct.
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What occurs in the striated duct in the parotid gland?
- The striated duct is the site of sodium reabsorption and secretion of potassium.
- increasing the amount of fluid in the duct
- iron anions, chloride and bicarbonate ions are exchanged across the membrane
- this increases the water retention and this is why serous acinus produces watery fluid.
What occurs in the ducts when a patient has parotitis?
Parotitis is the inflammation of the parotid gland.
- Inflammation occurs at the proximal end of the duct
- Salivary glands keep on producing saliva, the secretory cells carry on secreting and they build up fluid behind the blockage.
- Due to the blockage, swelling occurs, swelling occurs due to inflammatory cells and parts of the immune system e.g. neutrophils come in and block the duct.
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Where is the submandibular gland found?
Sits underneath the jaw on both sides.
- Has a long convoluted duct
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What type of membrane is found in the parotid and the submandibular?
Parotid gland - Almost totally serous, very few mucous and as we age the cells start to die off and replaced by adipocytes.
Submandibular gland - Mostly serous;more mucous glands than parotid (mixed)
Sublingual gland - Almost complete mucous
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What type of signalling controls the salivary glands?
- Neuronal
- Both parasympathetic and sympathetic ANS supply salivary glands and increase salivary secretions.
Parasympathetic - produces large volume of watery saliva rich in enzymes e.g. serous
Sympathetic - produces a small, thick secretion of saliva rich in mucus e.g. mucous
What is the largest exocrine gland and what provides its blood?
The liver
Hepatic blood supply includes the:
- Hepatic portal vein
- Hepatic artery
How does the Hepatic portal system work?
- Blood enters through the aorta and other vessels to the stomach and intestines where nutrients and sometimes toxins and bacteria are absorbed. (First capillary bed)
- Then the blood passes through the hepatic portal vein into the liver which has its own capillary bed, which is made up of sinusoid, nutrients and toxins leave and interact with the main cells - hepatocytes. (Second capillary bed).
- The blood then leaves through the hepatic vein into the inferior vena cava and back up the right side of the heart
What happens to blood coming from the aorta?
- The blood from the aorta goes through the splenic artery into the spleen and looks after the spleen.
- The deoxygenated blood from the spleen enters the splenic vein and joins up with the inferior mesenteric vein coming from the large intestines.
- This passes through the blood vessel and joins up with the superior mesenteric vein coming from the small intestines and creates the portal vein which is going to the liver.
What is the percentage of oxygenated blood coming from the hepatic artery? What is the percentage of deoxygenated blood coming from the portal vein?
Hepatic artery - 25% to 30% is oxygenated blood coming from the hepatic artery.
Portal vein - 70% to 75% of blood is deoxygenated and coming from the portal vein.
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What happens when the hepatic artery and the hepatic portal vein get to the liver?
- It subdivides and you get oxygenated blood coming from the hepatic arterioles(small artery) and deoxygenated blood coming from the portal venules (small vein).
- They meet at the edge of the liver lobule, the oxygenated blood and deoxygenated blood mix at that point.
- Some of the blood escapes through the hepatic sinusoids.
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What is specialised about the endothelial cell of the hepatic ‘capillaries’? What is the specialisation called?
- When the endothelial cell join together they change their shape and function, so instead of trying to keep the blood in, they are trying to let the blood escape into the hepatic sinusoids.
- The sinusoids are not real capillaries they are blood vessels that are sinusoidal and can be found in the spleen and bone marrow.
- sinusoidal cells have large gaps between them called sinusoids
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What is one of the functions of the liver?
- To take material from the blood supply, interact with them and produce something called bile, which passes out through the bile canal into the bile duct.
What are the different types of capillary vessels and where are they found?
- Continuous - Brain/most of the body
- The basement membrane is very tight and keeps large molecules out from getting into the interstitial space
- The cells are tightly packed together - Fenestrated - pituitary/small intestines/kidneys/some endocrine glands
- The cells are tightly packed together
- There are fenestrations (tiny holes) that allows small molecules to get into the blood vessel very quickly. - Sinusoids - Spleen, bone marrow, liver and lymph nodes
- Incomplete basement membrane and big intracellular gaps
- This allows large molecules, cells and fluids to move into and out of the cell.
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Describe the structure of the liver lobule.
- Hexagonal shaped (6 sides).
- (Terminal) Hepatic venule (centre vein) in the centre where blood comes out
- Portal vein and artery on the edge of the lobule where blood comes in
- The liver is divided into different lobules and the lobule are divided into different acini.
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What is the Hepatic triad?
Bile duct, portal vein and hepatic artery.
- The three vessels come together and are called the hepatic triad.
- Blood from the hepatic portal vein and the hepatic artery are joined together and is flowing through to the central vein and out through the hepatic vein
- Bile is flowing in the opposite direction into the bile duct.
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What are the size of the vessels involved in the hepatic triad relative to each other and what is found between the vessels?
- Hepatic portal vein is the largest compared to the hepatic arteries as veins are usually larger than arteries.
- The artery and bile duct are similar sizes
- Between the three vessels there are some interlobular connective tissue, usually loose areolar tissue.
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How many nuclei do hepatocytes have?
They are sometimes mono, bi- or tri - nucleated
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What are the different cells found in the liver acinus?
- Kupffer cell
- Dendritic cell - cell of the immune system, antigen presenting cell.
- Picks up bacteria, viruses and parasites and presents them to macrophages (kupffer cells). - Pit cell - form of natural killer cell which is part of the T- cell, tumour cells are identified by these cells and are destroyed.
- Stellate cell - cell of the immune system
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What are the features of the hepatocytes?
- Sinusoidal blood passes by the hepatocyte, the hepatocyte have canaliculus passing in 90 degrees angle.
- The hepatocytes sitting next to each other are secreting their products into the canaliculus.
- Hepatocytes are like epithelial cells as they secrete their products onto their apical membrane
- Hepatocytes are different from epithelial cells as they have an apical membrane in opposite sides of the cell and the basement membrane is at the sides where the sinusoidal vessels are.
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What do the microvilli behind the endothelial cells do?
- They absorb anything that comes from the hepatic portal vein e.g. nutrients, toxins and bacteria.
- Around the microvilli there are immune cells.
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What are Kupffer cells?
- Specialised macrophages that form part of the sinusoidal lining
- Constitute 80% of all tissue macrophages
- They are constantly exposed to gut-derived bacteria, microbial
debris, cell debris and bacterial endotoxins. - Kupffer cells migrate into liver tissue at sites of inflammation and damage
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