BL 12 Flashcards
Are parotid, submandibular and sublingual glands exocrine or endocrine?
Exocrine!
What type of glands are paratid, sumandibular and sublingual glands? (hint - where are they located)
Salivary glands!
What colour is mucous acini in a H+E stain?
Purple due to lots of protein
Parotid gland (type of gland, structure)
- Serous gland
Parotid gland - issue with the striated ducts
Infection in the gland:
- Infection causes inflammation around the striated duct and excretory duct (proximal end of the striated duct)
- The salivary gland continues producing saliva (the acinus glands do). This means the fluid builds up, leading to the swelling.
- Inflammation (the blockage) is caused by neutrophils etc moving into the infected area
- Therefore, the gland expands
What are the roles of the enfoldings in the basement membrane of the straited duct cells?
These enfoldings allow the epithelial cell to ‘flatten’ to be able to cope with the swelling due to the extrac fluid coming in
Paratoid gland - what the TEM looks like
Submandibular gland (structure, type)
Mixture of secretory cells:
- serous acini
- mucous acini
- some cells are a mixture - both serous and mucous acini
Summary, what type of glands are paratoid, submandibular, sublingal gland
- Paratoid gland: Almost totally serous acini
- Submandibular gland: Mixture
- Sublingual gland: Almost totally mucous (some are mixed = demilomes)
TEM - how do paratoid, submandibular and sublingual glands look?
- Mucous acini: Mucous is white as it isn’t stained by H+E
- Serous acini: Very purple as contains lots of proteins (lots of nuclei)
What is stimulus do the 3 salivary glands respond to?
Neuronal
Discuss the neuronal signalling with the salivary glands (must talk about mucous and serous cells)
Salivary system is controlled almost exclusively by neuronal singalling (other than digestive secretion, which is regulated by nervous system and hormones)
Both parasympathetic and sympathetic ANS (autonomic nervous system) supply the salivary glands and increase salivary secretion:
- Parasympathetic: produces a large volume of watery saliva rich in enzymes (SEROUS CELLS)
- Sympathetic: produces a small, thick secretion of saliva, rich in mucus (MUCOUS CELLS)
Liver - what type of glands?
Exocrine and endocrine function
Liver structure (must learn)
Liver blood supply (type of blood supply)
2 blood supplies TO the liver:
- Hepatic portal (part of the hepatic portal system)
- Hepatic artery (livers own blood supply)
What is a portal system?
One capillary bed connected to another capillary bed by portal veins. The capillary bed in the liver is mostly made up of sinusoids.
Why does the liver need it’s own blood supply?
The blood has past through the stomach, intestines and then to the liver. Therefore, once the blood reaches the liver, it is extremely deoxygenated. Therefore the portal vein doesn’t supply the liver with oxygen, the hepatic artery does instead.
Proportions of blood coming into the liver by each method
- Portal vein = 70-75%
- Hepatic artery = 25-30%
How the hepatic artery and hepatic vein ‘come together’ in the liver
- The oxygenated blood from the hepatic arteriole and the deoxygenated blood from the hepatic vein join. Before joining together, they are both capillaries. After they join, the structure is called a hepatic sinusoid.
(There contents mix when they join)
Draw a diagram to show the HA and HPV joining
How does the blood leave the liver?
Blood in the sinusoids, leaves the liver through the central vein, then goes to the gut.
Capillary vessels: Name the different types, explain there main features and where they are found
- Continuous: Epithelial cells very tightly together
- Fenestrations: Epithelial cells tightly packed together with tight junctions, however also have little holes in (fenestrations). Fenestrations pass right through to the basement membrane. Allows movement in and out quickly
- Sinusoid: Tight junctions where the epithelial cells do meet, however, large intracellular gaps. Basement membrane also got very large gaps in them. Cells can fit through the gaps.
Liver lobule (number of shapes,
Liver is divided into liver lobules (1 million liver lobules!)
Each liver lobule has 6 sides
Lobules divided into different acini
3 vessels together (hepatic artery, portal vein and bile duct) is called the portal triad
Bile passes out of the portal triad (away from the central vein)
What does a liver lobule look like?
Liver acinus
This is oblong shape, smallest functioning unit (LOOK DIAGRAM IN NOTES)
Portal triad (size of each component)
How many nuclei do hepatoctyes have?
- One
- Two
- or three
(if 2 or 3, said to be bi or tri nucleated)
What are the hepatocyte cells?
Hepatocytes are epithelial cells that synthesize and secrete bile, form and store proteins, remove toxins, and store and release carbohydrates.
Draw a diagram showing the hepatoctyes in the liver
What is the bile canaliculus?
Canal taking the bile to the first part of the bile duct is called the bile caniculus. These are between different layers in the hepocytes. THE HEPATOCYTES SECRETE THEIR PRODUCTS FROM THEIR APICAL MEMBRANE INTO THE BILE CANICULUS. Bile in the canaliculus is flowing perpendicular to the blood in the sinusoid.
LOOK AT NOTES
Talk about the apical and basal surface of the hepatoctyes
- Hepatocytes are epithelial cells
- They SECRETE their products from their APICAL MEMBRANE. (THEREFORE, THERE APICAL SURFACE IS ALWAYS NEXT TO THE BILE DUCT)
- Each hepatoctye secretes it’s products from BOTH APICAL MEMBRANES
- Other two surfaces are the basement membranes
Overall:
- 2 apical surfaces
- 2 basement membranes
Which other cells are in the liver?
(Hepatoctyes)
RBC
Kupffer cells
Ito cell (Stallate cell)
Dendritic cell
Pit cell
What cells tend to be in the Space of Disse?
This is the space between the endothelial cells and the hepatocytes
Cells of the immune system tend to occupy this space.
Why do the hepocytes has lots of microvilli on the blood vessel lumen side?
So they are able to absorb nutrients, toxins, bacteria etc coming through the portal vein.
Kupffer cells (type of cell, function)
- Specialist 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
FUNCTION:
• Trap and phagocytose any damaged or aged erythrocytes that were missed by the spleen
•After splenectomy, these cells take over the removal of 120 day old (aged) erythrocytes
• The sinuosids are perforated with large holes, meaning the macrophages (including Kupffer cells) can enter. Kuffner cells migrate into liver tissue at sites of inflammation and damage.
What is bilirubin?
Bilirubin is the break down product of RBC.
Kupffer cells break down RBC producing bilirubin, bilirubin is then taken up by the hepotocytes, the hepotocytes then process it. Bilirubin is the main contituent of bile.
Stellate (Ito) cells
- Function: contains cytoplasmic vacuoles containing Vitamin A
- In liver cirrhosis, hepatic stellate cells lose their vitamin A storage capability and differentiate into myofibroblasts. These synthesise and deposit collagen within the perisinusoidal space, resulting in liver fibrosis. CAUSE LIVER FIBROSIS.
Hepatocytes (percentage of liver cells, regeneration, some extra things they have, function)
- Constitute 80% of liver cell population
- Have remarkable regenerative ability!
-
Compared to other cells they contain: Numerous mitochondria
A lot of peroxisomes (organelles full of oxidising agents)
Numerous free ribosomes
A lot of rough endoplasmic reticulum
A lot of smooth endoplasmic reticulum Numerous Golgi complexes
Glycogen deposits - Functions: Detoxification, modification, and excretion of exogenous and endogenous substances / Initiation of formation and secretion of bile / Protein synthesis / Protein storage
Function of the liver - storage
- Iron stores
- Vitamin A, E, D, K (Lipid soluble vitamins)
- Glycogen stores
- Copper stores
Note about iron - when heamoglobin is broken down in RBC, and turned into bilirubin, the iron is kept and stored in the liver.
Liver function - Production
MORE THAN 60% OF ALL THE BODY’S PROTEINS ARE PRODUCED IN THE LIVER
- Major plasma proteins e.g. albumin
- Enzymes e.g. calatase and coagulation factors
- Lipid carrier proteins e.g. LDL, HDL
- Amino acid synthesis
- Haemopoiesis in the fetus (from week 5-32)
Liver function - catabolism (destruction)
DESTRUCTION OF -
- Drugs
- Hormones e.g. steroids, insulin, glucagon, etc
- Haemoglobin, bilirubin passes into the gall bladder
- Poisons/toxins
- After splenectomy - removal of RBC (liver than becomes the main organ to remove RBC as the spleen is no longer available to do it)
Liver - Other functions
- Bile production (exocrine)
- Filtering of cell debris from blood
- Hormones/Growth factors (endocrine) e.g. Angiotensinogen, Thrombopioetin and IGF-1
- Modifies hormones for excretion or function e.g. Oestrogen, progesterone, Thyroxine to T3, Vitamin D3 to calcitriol
How is this all achieved in the liver? e.g. all it’s functions
Achieved through signalling pathways -
• Autocrine signalling – VEGF
e.g. VEGF leads to an autocrine signalling pathway, acting on it’s own receptors inside cells.
• Paracrine signalling – Succinate (hepatocyte regeneration). Works on cells next to it. e.g. succinate hormone stimulates cells to grow.
• Endocrine signalling – GH to IGF1
• Intracrine signalling e.g. oestrogen and thyroid hormones stimulate apolipoprotein A1 production, which increases HDL in the blood – via HDL-C (good cholesterol) reduces risk of stroke and myocardial infarction
Summary - How it is the liver an exocrine gland?
The largest exocrine gland in the body: its constitutive secretion is bile (bile salts) that is passed through ducts to the gall bladder where it is stored (some leaks into the duodenum) – emulsify fats and assists in Vitamin K absorption from the small intestine
Summary - How is the liver an endocrine gland?
The largest endocrine gland in the body: its main constitutive secretion is albumin and its major regulated secretion is IGF-1
What is special about hepocytes?
Hepoctyes has BOTH exocrine and endocrine functions.
Very cool cells!
What are the three salivary gland?
Paratid gland, submandibular and sublingual gland
Draw the three salivary glands shapes, where are they located (be specific)?
