histology of accessory glands Flashcards
salivary gland functions
tasting, digesting and swallowing food
produce 700-1100ml of saliva each day
secretory potion arrangement
tubules and acini
three cell types on salivary glands + functions
serous cells- secrete proteins and polysaccharides
mucous cells- secrete mucous
myoepithelial basket cells- several long processes that envelop the acinus and contract to expel secretions
explain duct arrangement
highly branched ducts formed of
intercalated to striated to intralobular to interlobular to lobar to principle terminal
function of terminal ducts
deliver saliva to oral caity
two types of salivary gland
major and minor salivary glands
three types of major salivary gland
parotid, sublingual and submandibular
parotid size and secretion
largest gland
produces 30% of saliva
serous secretion with high levels of amylase
sublingual size and secretion
very small gland
5% of saliva
mainly composed of mucus and serous cells
submandibular size and secretion
produces 60% saliva and serious cells predominate
acinar and duct cell functions
acinar- responsible for volume of saliva
duct- responsible for composition
explain sympathetic control of secretion
superior cervical ganglion, release of noradrenaline, decreases production of saliva, increased protein
explain parasympathetic control of secretion
innervation due to facial and glossopharyngeal nerve
afferent fibres in the mouth detect changes to food in mouth- travel to the medulla
parasympathetic fibres release acetylcholine onto muscarinic receptors
increase secretion from acinar cells
duct cells increase bicarbonate secretion
contraction of myoepithelium
two component of pancreas + function
exocrine- secretes enzymes
endocrine - secretes hormones
explain endocrine structure
islets of Langerhans comprise 1-2% of the volume
consist of beta, alpha, delta and pancreatic polypeptide cells
pancreatic polypeptide fucntion
inhibits acinar endocrine secretion
explain exocrine structure
clusters of cells
duct cells penetrate into central regions of acini called centroacinar cells
where do the ducts open into?
the common bile duct, and empty into the major papilla duct (ampulla of vater)
what is present in both salivary and pancreatic acinar cells?
zymogen granules
zymogen granule function
specialised storage granules of proteases, that allow for release
what is the largest gland within the body?
liver
how much blood perfuses the liver per minute?
1.5 litres
liver major functions
recycling, waste disposal
how is the liver represented?
polygonal aggregation of cells that are arranged in irregular radial cords of cells interrupted by strands of supporting tissues that contain vascular and biliary passages
main cell type in liver
hepatocytes
classic liver lobule structure
central vein, peripheral portal triads set at angles to the polygons
hepatocytes radiating from central vein separated by vascular sinusoids
sinusoid definition
low pressure vascular channels that receive blood from hepatic arteries and the hepatic portal vein at the peripheries of the lobules and then bring them towards the central vein
liver capillary
hepatic lobule definition
building block of the liver
contains a central vein, portal triad, hepatocytes in linear cords and a capillary network
what is present in the portal triad?
hepatic artery, portal vein, bile ductule, lymphatic vessels and branch of vagus nerve
portal triad shape
triangle, connecting three central veins
two important features of liver sinusoids
Kuppfer cells and space of Disse
explain structure and function of space of Disse
space between a sinusoid and the hepatocyte
contains blood plasma
microvilli of hepatocytes extend here so that they can absorb molecules from blood
structure of sinusoid
discontinuous basement membrane and fenestrated endothelium allows for easy exchange
kupffer cell location
within sinusoids
kupffer cell function
specialised macrophages
clear bacteria
break down red blood cells, split haemoglobin
kupffer cells are an example of
mononuclear phagocyte systems
bile duct definition
tiny intracellular spaces flanked by tight junctions that form small conduits around hepatocytes
produce bile continually
bile function
emulsify fats and facilitate their absorption
what is bile?
breakdown products of worn out red blood cells
biliary tract definition
liver, gall bladder and bile ducts
gall bladder function
reservoir for bile
concentrates bile
adds mucus to bile
when does the gall bladder secrete bile?
discharges its contents in response to the entry of fatty foods into the duodenum
histology of gall bladder
folded mucosa or simple columnar epithelial cells
fibrovascualr lamina propria
deep muscularis
external layer of supporting tissue with elastic fibres
outer serosa
what is the gall bladder epithelium resistant to?
bile
common disorder of the biliary system
gallstones
explain gall stones
excessive accumulation of cholesterol in the bile
excess sterol may crystallise and calcify into a stone
painless unless they are located in the neck where they may obstruct outflow and cause inflammation
