Supporting Digestion Flashcards
Describe the composition of saliva and their function
Mucus
Enzymes (mainly amylase)
Antibacterial enzymes (lysozyme that prevent dental decay)
Proteins (lactoferrin)
Antibodies
Inorganic ions (teeth, mineralisation/repair)
Proteins to coat teeth, protection
Functions of saliva
Lubricates Moistens Begins digestion (a amylase, lipase) Antiseptic (IgA and lysozyme) Teeth maintenance and repair
How much saliva do we produce each day
600-1500ml/day
Function of the salivary glands
Types of salivary glands
Secrete in response to physical, chemical, psychological stimuli via parasympathetic
Parotid
Sublingual
Submandibular
Buffalo
Labial
Lingual
Palatine
Describe the composition of parotid glands
Serous cells, thin watery secretion
Enzyme and antibody rich
Stains well with H and E
Describe the composition of sublingual cells
Mucous cells, viscous secretion
Does not stain well
Describe the composition of submandibular glands
Has both serous, mucous secretory cells
Only the serous cells stain well
Describe the composition of a serous acinar cell
Well stained granules Many -Secretory granules -Golgi -RER
Describe the composition of a mucous acinar cell
Poorly stained granules
Many
-Mucus product granules
-Irregularly basally located nuclei
Describe what serous demilunes are
May be a fixation artefact
Conventional fixation leads to serous demilune shape between mucus cells
Describe the composition of intercalated ducts
Lined by cuboidal epithelium
Longest in parotid, join within lobules to form striated ducts
Describe the composition of striated ducts
Lined by tall columnar epithelium ,large nuclei towards apex
Basal cytoplasm has interdigitations of cytoplasmic processes and mitochondrial columns
Na+ pumps reabsorption Na+, Cl-, replaced with K+, HCO3-,
Saliva becomes more hypotonic here
Describe the composition of the interlobular duct
Pseudostratified columnar epithelium
Describe the composition of the lobular duct
Stratified bilayer of cuboidal/columnar
How are secretions from the acinar stimulated
Parasympathetic, sympathetic stimulations cause -Proteins -Enzymes -NaCl -H20 To be secreted from the acinar cells
Isoosmotic saliva passes through the intercalated duct
Hypotonic saliva formed in the striated duct
-NaCl removed
-K+, HCO3- secreted into the duct
Describe the structure of the glands in the pancreas
Compound tubular gland in concavity of duodenum
Combined exocrine and endocrine gland (no digestive function)
Describe the structure of the endocrine glands in the pancreas
Endocrine cells have an apical nucleus, basal secretory vesicles
Release hormones into fenestrated capillaries in the Islets of Langerhans
Describe the cellular composition of the Islet of Langerhans
A cells, (20%) glucagon B cells (70%) insulin S cells (5-10%) somatostatin PP cells (1-2%) pancreatic polypeptide
Other minor cells secrete VIP, P, motilin, seretonin
Describe the structure and composition of the exocrine pancreas
Acinar secretory cells with centroacinar cells (unique to pancreas)
Lumen of acinus leads to intercalated duct lined with simple cuboidal epithelium
Non striated ducts converge => interlobular ducts lined by stratified cuboidal epithelium
Describe the structure of the acinar cells and the centroacinar cell
Acinar cell has a basally located nucleus and apical secretory vesicles
Centroacinar cells line the lumen of the duct
What is the function of the exocrine pancreas acinar
Secrete enzymes
Pyramidal cells with round basally located nuclei, basophils cytoplasm, well developed RER
Apices packed with eosinophilia secretory zymogen granules
Released into lumen, merocrine (CCK response from I cells)
Function of the centroacinar cells
Water and HCO3- secretions
Pale nuclei, sparse pale cytoplasm
In center of acini
Form terminal lining of intercalated ducts
Describe the composition of pancreatic juice (1L/day)
Apical area of acinar cells contains Golgi and zymogen granules with around 20 different enzymes/precursors
Rich in HCO3-, neutralise acidic chyme
Duodenal lining synthesises enteropeptidase, activates trypsinogen => trypsin
Describe the composition of the intercalated ducts in the the exocrine pancreas
Lined by cuboidal epithelium
How are pancreatic secretions stimulated
Parasympathetically stimulated
Acidic chyme causes CCK and secretin to be released into the blood
CCK causes secretory zymogen granules to be released by the acinar cells
Secretin causes HCO3- to be secreted from the ductal cells
What are the main differences between the pancreatic acinar and the parotid acinar
Parotid
- Striated ducts
- No centroacinar cells
- No Islets of Langerhans
Pancreas
- No striated ducts
- Centroacinar cells
- Islets of Langerhans
What are the main functions of the liver
Protein metabolism Carbohydrate metabolism Fat metabolism Storage Detoxification Secretion
Describe the functions of the liver
Protein metabolism
Non essential AA synthesis
produce plasma proteins (albumin, clotting factors, lipoprotein proteins, Fe, Cu transport proteins)
Describe the function of the liver
Carbohydrate metabolism
Carbs and protein => FA and TAGS
Regulate [blood glucose]
Describe the function of the liver
Fat metabolism
Cholesterol, phospholipids, plasma lipoprotein synthesis
Describe the function of the liver
Storage
Fe
Vitamins
Glycogen
Describe the function of the liver
Detoxification
Of metabolic waste products
Deamination of AA => NH3 => urea => kidneys
Of steroid hormones, lipid soluble drugs
Metabolism of alcohol => acetalaldehyde => acetate
Describe the function of the liver
Secretion
Synthesis, secretion of bile
Describe the liver blood supply
Hepatic artery, hepatic portal vein
HPV brings substances absorbed by GI => liver
HA, oxygenated blood
Blood enters sinusoids of lobules, exposed to hepatocytes over LSA
Central vein collects blood, coalesce to => R and L HV => IVC
What is the portal triad
HPV
HA
BD
Describe the structure of the structural liver lobule
Veins surrounded by hepatocytes
Lobules surrounded by connective tissue
Portal tract forms when CT converges
Sinusoids flow towards central vein
Bile flows away from the central vein, into hepatic duct
Describe the structure of the liver sinusoids
Hepatocytes form sheets with at least 1 surface facing a sinusoid Sinusoid walls (fenestrated epithelium) with Space of Disse between hepatocytes and endothelial sinusoid cells
Space of Disse contains hepatocytes microvilli
Macrophages (Kupffer cells) in inner sinusoid walls
Stellate cells produce ECM
How is bile synthesised
In liver, stored and concentrated in gall bladder
Synthesised from cholesterol, acts as an emulsifying agent in gut, facilitated fat, vitamin absorption across mucosa
Bile salts absorbed in terminal port of ileum, returned to liver via portal system
Bile pigments breakdown products of worn out blood cells, destroyed by macrophages of spleen/Kupffer cells
Describe the structure of the liver acinus
Roughly hexagonal in shape, each point has a bundle of sinusoids and a bile duct
Surround a central vein
Z1, most oxygenated, nutrient rich, closest to blood supply
-Specialised for oxidative functions (gluconeogenesis, B oxidation, cholesterol synthesis)
Z2, intermediate, O2, nutrient depleted
Z3, Specialised for glycolysis, lipogenesis, cytochrome drug detoxification
Describe what happens to the liver in a paracetamol overdose
Extensive damage around central vein, denatured proteins take up more eosin
Hepatocytes around portal trial stain less, accumulate fat
Loss of liver architecture => RBC infiltration between cells
Z3, most sensitive to quinone produced by paracetamol
Describe what happens to the liver in cirrhosis from chronic Hep B
Extensive fibrosis of portal triad, lobules
Architecture of lobules disrupted
Lots of inflammatory cells
Describe what happens to the liver in cirrhosis causes by alcohol
Extensive fibrosis from Stellate cells
Architecture of lobules severely disrupted
Hepatocytes restricted to small regenerative nodules
Describe the composition and function of the gall bladder
Muscular sac with simple tall columnar epithelium
Epithelial have irregular microvilli at luminal surface, basal nuclei
Loose submucosa rich in elastin, blood vessels, lymphatics
Bile resevoir
Conc bile from NaCl pumped from basolateral border => osmotic gradient
This displaces the basolateral surface causing splits between cells
Water enter lymphatics in lamina propria
How does CCK cause bile release
CCK produced by I cells in duodenum in response to lipid
Causes smooth gall bladder muscle to contract
Bile discharges => duodenum via cystic duct and common bile duct controlled by major duodenal papilla
Emulsifying agent in gut, faciliates fat, vitamin absorption across gut mucosa
