15. Histology of GIT + associated organs Flashcards
3 major salivary glands
1) Parotid 2) Submandibular 3) Sublingual
Functions of saliva
to moisten the mucosa and food before swallowing
high bicarbonate content buffers the oral cavity → stimulate taste buds
begins the digestion of carbohydrates via amylase
controls bacterial flora by secreting lysozyme
secrete IgA and potassium
resorbs sodium
3 types of ducts
1) Intercalated 2) Striated (secretory) 3) Excretory
Intercalated duct
secrete bicarbonate ion (HCO3-)
absorb chloride ion (Cl-)
Striated (secretory) duct
secrete K+
absorb Na+
Sialosis
non inflamatory enlargment of parotids
caused by excess alcohol use.
Benign tumour of the left parotid gland
producing characteristic deflection of the ear lobe
Parasympathetic innervation of salivary glands
cranial nerves: 7 & 9
Sympathetic innervation of Salivary glands
pre-ganglionic nerves in: T1-T3
Epithelium of digestive tract
ends: non-keratinised stratified squamous
in between: simple columnar
Oesophagus
Non-keratinised stratified squamous epithelium
Only lowest portion has Serosa
Rugae (stomach)
allow stomach to expand
Gastric pits (Stomach)
Hole like depressions between villi
ductal openings of stomach glands
Epithelium of stomach
simple columnar
has no goblet cells
Parietal Cells ( produce Acid and Intrinsic factor)
Chief Cells (pepsinogen)
Lamina propria (stomach)
abundant glands
secrete mucus
Functions of the small bowel
Main site of digestion and secretion
Coeliac Disease
Autoimmune
destruction of the small bowel villi
due to gluten exposure
Gliadin is presented by APCs on MHC Class II
leads to T Helper Cell mediated tissue damage
Flattening of the villi, Hyperplasia of Crypts and increase in interepithelial lymphocytes
Adaptations of Duodenum: Shortest Segment
Long-leaf-like villi
Brunner’s Glands
Order of number of Plicae Circulares (most to least)
1) Jejunum
2) Duodenum
3) Ileum
Adaptations of Ileum
↑ number of Goblet cells
↑ Peyer’s Patches and M cells
Teniae coli in the Colon
three visible strips of longitudinal muscle
aid in peristalsis
everywhere except appendix and rectum
Haustra in the colon
small saccules of large intestine
Help move faeces in segmental fashion
What adaptations are NOT found in the Colon?
plicae
villi
Mucosa of colon
thin
columnar Epithelium
simple tubular glands → crypts → produce mucus
Largest internal organ
Liver
Hepatocytes
Large polygonal cells
form plates of hepatic lobule
Hepatocyte Function
Protein synthesis
Protein storage
Transformation of carbohydrates
Synthesis of cholesterol, bile salts and phospholipids
Detoxification
Formation and secretion of bile.
What percentage of the liver’s cytoplasmic mass do hepatocytes make up?
70-85%
Sinusoids
endothelium with large gaps between cells
incomplete basement membrane
Where are sinusoids found? (4)
Liver
Spleen
Adrenal Medulla
Bone Marrow
Kupffer Cells (liver)
macrophages
Stellate cells (liver)
Found in Space of Disse
Store fats, Vits A,D,E,K B12
Secrete ECM
What produces bile?
hepatocytes
The Bile duct
carries bile → gallbladder
Canaliculi
channels lined by the cell membranes of adjacent hepatocytes
Carry bile outward from hepatocytes → Portal Triad where they join a branch of the bile duct
Zone 1 of the liver
nearest to distributing vessels
first to be affected by incoming blood
Zone 3 of the liver
furthest from vessels
first to show ischaemic necrosis and fat accumulation
last to be affected by toxic substances
Zone 2 of the liver
mix of zone 1 & 3 characteristics
Classical Liver Lobule
Hexagonal Division
1 central vein
6 hepatic portal triads one in each corner of the hexagon
Portal Lobule
Triangular division
3 central veins in each corner
1 hepatic portal triad in the centre
Hepatic Acinus
2 adjacent triangular wedges
2 central veins at each apex of each triangle
2 hepatic lobules
Pancreatic acini cells
contain inactive forms of digestive enzymes
drained by a series of inter-connecting ducts
emptying directly into the main pancreatic duct
