Glands 2 Exocrine and Specialised Flashcards
What are the two types of epithelial cells
- cells lining the ducts
- cells that make secretory products
What are myoepithelial cells
Where and how do they form
- Cells that have features of both an epithelial cell and a smooth muscle cell
- Help to eject secretions from the duct
- Some of the cells at the secretory ends of the ducts change morphology and class by turning into myoepithelial cells
What is periodic shift reagent
Cell Staining technique that stains sugars (useful for staining goblet cells)
What is the masseter muscle used for
The masseter muscle is one of the four muscles responsible for the action of mastication (chewing)
Parotid Gland structure
(Look at lecture slide pg7)
- Starts with the Acinus
- These cells secrete a fluid that contains water, electrolytes, mucus and enzymes, all of which flow out of the acinus
- Between two lobules - intracellular duct
- When they come together this forms the striated duct
- Striated duct comes together to form the excretory duct
- Excretory duct is a larger duct that goes out onto the surface
How do mumps form
- The virus of mumps attacks ducts
- This causes a blockage at the striated duct level
- Salivary Glands still continue to produce secretion
- As striated duct level is blocked it cannot pass
- There is a build up behind the striated duct
- This causes the swelling (mumps)
In Striated duct why is nucleus being moved away from the basement membrane
- This is due to Basal Infolding
- Basement and Plasma membrane are folded in on its self across the basement membrane (Basal infolding)
- this pushes everything infront towards the Apex and Lumen
Striated duct - function
- Na+, K+, Cl-, HCO3-, H2O all travel into the Acinus.
- As you travel down into the Intercalated duct Na+ and Cl- will travel out of cell whilst K+ and HCO3- travel into the ducts
- As you travel in to the striated duct K+ still travels into the cell whilst Na+ travels out of cell
- Water is left behind (as the pushing out of Na+ and pushing in of K+ allows for a balance)
- This all helps prevent water loss so water can move to secretory duct.
Where do you find the Submandibular glands
Underneath the Jaw
Structures in the Parotid glands
look at lecture slide
Structures in the Submandibular glands
Look at the lecture slide
What ducts are found in the Submandibular Gland
Warhtin’s duct,
The Submandibular Gland has a duct called the Warhtin’s duct,
It comes up from all the up to underneath the tongue and joins up with another duct from the parotid gland.
Difference when staining the parotid gland and the Submandibular glands
Parotid Gland has a darker stain sue to it producing more proteins (enzymes) , as the Submandibular glands produces mucos aswell.
Where do you find the Sublingual Gland
Underneath the tongue
What is the difference between the Parotid gland, the Submandibular Gland and the Sublingual Gland
(eg with staining with H&E)
- Parotid is the darkest (when stating with H&E) - Produces the most proteins (enzymes) (mostly Serous)
- Submandibular gland in lighter in colour - Mostly Serous but more Mucous
- Sublingual Gland is the Lightest, Almost completely mucous, little serous. More Mucus produced
What happens to the
Parotid,
Sublingual and
Submandibular with age
They will Adipose Tissue
What stimulus produces Saliva
Only NEURONAL stimulation
Stimulus is neuronal
What is the autonomic Nervous system (ANS), split into
- Parasympathetic and Sympathetic pathways
What does the Parasympathetic and Sympathetic pathways do in the ANS to supply salivary glands and increase salivary secretion
Parasympathetic - Produces a large volume of watery saliva rich in enzymes.
Sympathetic - Produces a small, thick secretion of saliva, rich in mucus
What is the largest Exocrine Gland
The liver – the largest exocrine gland
Ligaments in the liver label
look at lecture slide pg 15
What happens in the hepatic portal system
- Arterial Blood
- Blood goes into the stomach and intestines
- Splits up into the first capillary bed
- Nutrients and toxins from the the stomach and intestines are absorbed into the blood stream
- Blood with there nutrients and toxins then travel into the hepatic portal vein
- Then splits in to the second capillary LIKE bed
(LIVER SINUSOLIDS) - Nutrients and toxins leave into the liver cells where they are processes
- Blood then Capillary like bed back into the Hepatic vein
- Then joins the Venous blood
How does the liver get its oxygenated and deoxygenated blood.
- Liver has its own Artery
- Blood comes in from the Aorta
- This can either split into the Hepatic Artery which takes oxygenated blood directly to liver or
- Into the Splenic Artery
- The Splenic Artery travels into the spleen
- The Splenic Vein leaves the spleen
- The Splenic Vein joins to the inferior mesenteric vein from the large intestines and also joins to the superior mesenteric vein from the small intestines
- This forms the portal vein which deoxygenated blood to the liver
- What percentage of blood goes to liver from portal vein & what percentage comes from Hepatic Artery
70-80% comes from Portal vein (deoxygenated blood)
20-30% comes from Hepatic Artery (oxygenated blood)
What is the portal triad
The portal triad contains the Hepatic portal vein, hepatic artery, and bile ducts coming into the liver
What is a liver lobule structur, how does it work
- Liver lobule – hexagonal shaped – 6 sided
- Each Node “end” is has a portal triad
- Blood flows down to the central vein in the middle,
- As it flows down bile is produced and flows down the opposite direction
- Oxygenated and Deoxygenated blood mixes and passes down central vein.
- As it does this it gives up its oxygen to Hepatocytes
- Hepatocytes pass some of the oxygen back, in the bile.
What is it called when Hepatic artery and HPV come together
Sinusoid
sinusoid tube structure
- a sinusoid tube is an irregularly shaped tube through which blood passes
It is Thin at the Hepatic portal end and Central Vein end
Wide where the two vesicles join together - (its not a real capillary (blood vessel) but similar to that in spleen and bone marrow
- Sinusoidal cells have large gaps between them (sinusoids)
What are the three different types of Capillary Vessels
- Continuous Vessel
- Fenestrated Vessel
- Sinusoid Vessel
What is the Continuous Vessel
- where is it found
- It is packed together very tightly
- Sealed Basement membrane
- Endothelial Layer made of Endothelial and Epithelial cells
- Endothelial layer held together by intracellular cleft
this prevents anything from escaping - If any escape occurs can lead to Odeama
(Brain/Most of the Body)
What is Fenestrated Vessel
- where is it found
- Intact basement membrane, allows for some filtration
- Endothelial layer contains fenestration, little holes which allows for molecules to pass through
- intracellular clefts
(Pituitary/ Small intestines/ Kidneys/ Some Endocrine Glands)
What is the Sinusoid Vessel
- Where is it found
- Caps in the basement membrane allows for cells to leave vessel
- Incomplete basement membrane
- intracellular clefts hold cells together
- Endothelial layer contains intercellular gap allows cells to get though such as RBC’s and WBC’c
(Spleen/ Bone marrow/ Liver/ Lymph nodes)
What can you see with the portal triad microscopy
- Branch of portal vein - Largest ‘hole’
- Branch of bile duct - Stains very purple in H&E
- Branch of Hepatic Artery
- Hepatocytes, sometimes bi- or tri-nucleated
- Septum - holds liver in place
Other structures also found: - Nerves
- Lymphatic vessels
- Fat
Why are Hepatocytes sometimes bi- or tri-nucleated
This is due to its function
As they need to make lots of proteins
Structure of hepatocytes and blood supply around it.
- Hepatocytes are epithelial cells WITHOUT a basement membrane
- They have two apical membranes instead
- In the apical membranes there are tight junctions, gap junctions and adherence junctions
- This is as between the hepatocytes is where the bile ends up
- As the two hepatocytes come together they form a little hole (called the bile canaliculus)
- They have basolateral membranes which have microvilli.
- These sit in a space between the cells of sinusoid and the sinusoid blood vessel itself.
- This place is called the space of Disse
- Blood and bile move in a counter current
- Blood gives up some of its oxygen and that oxygen is brought back to cells that need it.
How do Canaliculi turn to bile ducts
- Canaliculi goes to …
- Interlobular tributaries…
- Periportal bile ductules…
- Bile ducts…
- Left and right hepatic ducts…
What do the Kupffer, stellate and Dendritic cells function in the kidney
- The stellate and dendritic cells sit in the space of Diss
They are part of the immune system - The Kupffer cell is a macrophage, thus when bacteria gets in it engulfs it.
Location and function of the Küpffer cells
- 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
Küpffer cells summary
Kupffer cells are specialised macrophages that patrol the sinusoids, recycling old red blood cells and ingesting pathogens
The lining of these vessels is perforated with large holes
Kupffer cells migrate into liver tissue at sites of inflammation and damage
Stellate (Ito) cells structure
Full of cytoplasmic vacuoles (that coalesce) containing vitamin A
What is an important source of vitamin A
For many years, fish liver oils (e.g., cod liver oil) were medically and important nutritional sources of vitamin A
What happens to cells Stellate cells in liver cirrhosis
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
Why are hepatocytes important
- Constitute 80% of liver cell population
- Have remarkable regenerative ability!
Compared to other cells what do hepatocytes contain (7)
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
What happens in hepatocytes during Cirrhosis
Mitocindria have to take up Vitamin A
Mitocondria Expand
This leads to some of then dying
Liver regeneration
- Extent of damage
- How long
- What can cause it
Low to mild (< 50%)
* Viral infections and occasional alcohol use
* 7-8days
Mild to medium (up to 70%)
* Liver transplant or drug toxicity (paracetamol) or heavy alcohol use
* 30-40days
Medium to severe (>70%)
* Chronic liver failure
* Cirrhosis/chronic alcohol misuse/suicide attempts
* Never
*Need a live transplant
How is liver regeneration achieved
- Autocrine signalling – VEGF and HGF
These growth factors stimulates cell to divide - Gap junction signalling – Succinate (hepatocyte
regeneration)
Signals neighbour cell to divide - Paracrine signalling - TGFb to CTGF
Connective tissue formation making septum holding lobules together - Endocrine signalling – GH to IGF1
- Intracrine signalling – Estrogen acting directly on Apo A1 promoter and CYP2A6 to increase HDL-C production and cholesterol accumulation
As it fills with cholesterol cells eat to divide
Whatare the four functions of liver
- Storage
- Anabolism (production)
- Catabolism (destruction)
- Other functions
Liver storage
Metals
* Iron and copper
Vitamins A, D, E and K
(Lipid soluble vitamins)
Sugars
* Glucose (as Glycogen)
Anabolism (production) liver
More than 60% of all the body’s proteins
- Major plasma proteins
* Albumin
- Enzymes
* Catalase and coagulation factors
- Lipid carrier proteins
- Apolipoproteins (HDL, LDL, etc.)
Amino acid synthesis
* aspartate, glutamine, alanine, glycine and serine, etc.
Haemopoiesis in the embryo/fetus (from week 5 to week 32)
Making of RBC’s until bone marrow starts to create them
Catabolism (destruction) liver
Drugs Hormones
* Steroids, insulin, glucagon, etc.
Haemaglobin
* Bilirubin passed to gall bladder
Poisons/toxins
Sugars
* Fructose to glucose
* After splenectomy – removal of aged and damaged RBCs
Other functions in the liver
Bile production (exocrine)
Filtering of cell debris from blood
Hormones/Growth factors (endocrine)
* Angiotensinogen, Thrombopioetin and IGF-1
Modifies hormones for excretion or function
* Oestrogen, progesterone
* Thyroxine to T3, vitamin D3 to calcitriol
SUMMARY OF THE LIVER
- The largest exocrine gland in the body: its constitutive exocrine secretion is bile that is passed through ducts to the gall bladder where it is stored (some leaks into the duodenum) – Function: emulsify fats and assist in vitamin K absorption from the small intestine
- The largest endocrine gland in the body: its main constitutive secretion is albumin and its major regulated secretion is IGF-1 (somatomedin)
- NB The liver is different to pancreas, because the same cell executes both endocrine and exocrine functions - Hepatocyte
what do Lymphoid tissue do in the kidney
Removes fluid from the sinusoid space
Preventing issues such as Oedema
Difference between simple and compound gland
SIMPLE GLANDS contain a single unbranched duct. The secretory portion of the simple glands can be straight, coiled or branched. These can be found in the lower portion of the stomach and are the precursor for sebaceous glands in the skin (not found in the adult) and sweat glands (found in the adult skin).
COMPOUND GLANDS have ducts that branch repeatedly, as shown below. Often the terminal acinus is lined with myoepithelial cells that are specialised epithelial cells that contain actin and myosin (similar to that of a smooth muscle cell) and so can contract and ‘squeeze’ the contents of a mucous cell into the ductile system. There are many examples in the human body (e.g. lung alveoli, the liver, pancreas, breast and parotid glands).
Difference between an acinar and tubular gland
A tubular gland has a tubular shape of the gland and the ducts have a tubular lumen. Alveolar and acinar glands have a spherical gland shape with a bulbous base
Difference between serous and mucous cell
Mucous cells produce mucus, which doesn’t stain very darkly, so the mucous cells look almost clear on these images and on slides. Serous cells produce a watery secretion that contains a lot of proteins. Serous cells stain fairly dark.
What are Unicellular glands
Unicellular exocrine glands are the simplest form of exocrine gland. They occur as isolated secretory cells within an epithelium. The primary example is that of the mucus-secreting goblet cell. These are widely distributed in the intestinal epithelium and are found singly, as in the jejunum, or lining the ducts of simple
How to Goblet cells stain
Goblet cells are interspersed amongst the simple columnar epithelial cells. They synthesise mucin proteins and secrete them onto the epithelial surface, where they form mucus, which lubricates and acts as a protective barrier. Alcian blue stains mucin (the principal glycoprotein constituent of mucus) a vivid blue making the goblet cells easier to see.
What is the function of goblet cells
Their primary function of goblet cells is to produce mucin proteins and to secrete them on their apical surface. With surrounding fluids, the mucin proteins produce mucous, which aids the movements of substances along the epithelial cell surfaces, usually in the presence of cilia or microvilli that have a ‘beating’ action.
What is the function of hepatocytes
Protein synthesis and storage
Carbohydrate metabolism and storage
Fat metabolism and storage
Cholesterol metabolism, synthesis of phospholipids and bile salts
Detoxification, modification and excretion of exogenous and endogenous substances
Initiation of formation and secretion of bile
The storage of essential vitamins and minerals
