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Explain anatomy and histology of the stomach
- - Below the esophagus, the GI tract expands to form the stomach, a temporary "storage tank" where chemical breakdown of proteins and food occurs.
- - The stomach lies in the upper left quadrant of the peritoneal cavity, almost covered by the liver and diaphragm.
- - Stomach varies from 15-25cm long but its diameter and volume depend on how much food it contains.
- Main regions include:
- -plyoric antrium
- -plyoric canal
- -plyoric sphincter
- 3 Layers are:
- -smooth muscle
Process of carbohydrate digestion and enzymes involved
- - Chemical digestion of starch begins in mouth
- - Salivary amylase splits starch into oligosaccharides
- -Continues until amylase is inactivated by stomach acid and broken apart by the stomachs protein digesting enzymes.
- -Starchy foods and other digestible carbohydrates that escape being broken down are acted on by pancreatic amylase in the small intestine
- - Intestinal enzymes further digest these to monosaccharides.
Main Events in Prevolunray and postvoluntary phase
- Prevoluntary Phase:6-13 days
- In the ovary(follicular phase)-several follicles are developing under stimulation by FSH and produce oestrogen
- -only one follicle survives
- In the uterus(proliferative phase)
- -increasing oestrogen levels stimulate repair and thickening of endometrium
- Postvoluntary Phase:14 Days
- In the ovary (luteal phase)-corpus luteum produces progesterone (p) and oestrogen (o)
- -if fertilisation doesnt occur--> scar is formed and secretion of P & O stops
- -if fertilsation occurs--> HCG is released
- In the uterus(secretory phase)-corpus luteum hormones promote formation of endometrial glands
- -if no fertilisation occurs --> menstrual phase will start.
Main functions of the liver
- The liver is one of the most important organs. It has many metabolic and regulatory functions.
- -Its digestive role is to produce bile for export to the duodenum.
- -The livers main function is to filter and process the nutrient rich blood delivered to it.
- Other functions include:
- -Carbohydrate metabolism
- -Lipid metabolism
- -Protein Metabolism
- -Activation of vitamin D
Composition and role in digestion of Gastric Juice and Pancreatic Juice
- Gastric Juice:Composition-Parietal Cells- Releasing HCL
- -Chief Cells- Producing pepsinogen
- -histamine/serotonin- control activation and releass of pepsinogen
- -secretin- inhibits gastric gland secretion
- Role-Produce contractions of stomach muscles
- Pancreatic Juice:
- -Consists of water, salts and biocarbonate
- Also consists of enzymes:
- -pancreatic amylase
- -pancreatic lipase
- Role-Neutralise acidic gastric juices
- -Stop action of Pepsin
- -Create Proper pH for digestive enzymes
Enzymes involved in digestion:
- Protein digestion begins in the stomach when pepsinogen secreted by the chief cells is activated to pepsin
- Trypsin and chymotrypsin:-secreted by the pancreas
- -chop the proteins into smaller peptides
- Carboxypeptide:-Splits off one amino acid at a time from the end of the polypeptide chain
- Aminopeptidase and dipeptidase:-Liberate the final amino acid product
Composition and role of bile in digestion
- Composition:-Yellow/Green alkaline solution
- -bile salts
- -bile pigments
- Role in digestion:- Main role of bile is to emulsify fats
- - As aresult, large fat globules entering the small intestine are physically separated into smaller droplets
- -Stored in gallbladder and released when needed
Anatomy and histology of liver + liver recieving blood
- - Largest gland in the body - 1.4kg
- - Located under the diaphragm almost entirely within the ribcage
- - Liver has 4 primary lobes
- -Right lobe is the largest, separated from left lobe via falciform ligament.
- -Caudate lobe and the gaudate lobe are inferior to the left lobe
- - Each lobule is roughly hexagonal in shape.
- The liver recieves blood from the :
- Hepatic portal vein:
- -Bring nutrient rich blood from stomach and intestines
- Hepatic artery:
- -Brings oxygenated blood
Mechanism of regulation of secretion and release of bile and pancreatic juice.
- -secretion of bile and pancreatic juice and the release of these secretions to the small intestine is regulated by the same factors:
- -neural stimuli
- -Bile salts are the major stimuli for enhanced bile secretion as well as secretin.
- -when no digestion occurs, the hepatopancreatic sphincter is closed and the released bile backs up into the cystic duct to the gallbladder for storage.
- - The main stimuli for gallbladder contraction is cholecystokinin.
- -cholecystokinin also stimulates secretion of pancreatic juice.
- -both secretin and cholecystokinin prompt the pancrese to release its juice
Actions of hormones that show effects on solutes in blood
- Aldosterone:-When aldosterone concentraions are high, all the remaining filtered sodium is actively reabsorbed in the proximal convoluted tubule and collecting duct.
- -When aldesterone release is inhibited, virtually no sodium reabsorption occures beyond distal tubule.
- Angiotensin:-Prods the adrenal cortex to release aldosterone and also increases sodium reabsorption.
- Atrial Natriuretic Peptide:
- - Reduces blood pressure and volume by inhibiting events that promote vasoconstriction.
- - Promotes excretion of sodium and water
Mechanisms of formation of concentrated and dilute urine
- Controlling the reabsorption of the water from filtrate in the collecting ducts is the job of ADH.
- -ADH inibits urine output
- Concentrated Urine:
- -depending on the amount of ADH released, urine concentration may rise to 1200m0sm.
- -with maximal ADH secretion, up to 99% of the water in the filtrate is reabsorbed in the blood.
- Dilute Urine:
- -Tubular filtrate is diluted as it travels through the ascending limb of the loop of henle, so all the kidney has to do to secrete dilute urine is allow it continue its way the renal pelvis.
- -when ADH isnt being released, collecting ducts remain impermeable to water.
Anatomy of the kidneys and main function
- Anatomy:-2 kidneys
- -bean shaped organ, laying between the dorsal body wall and the parietal peritoneum.
- -Recieve some protection from the lower part of the rib cage
- -Right kidney is crowded by the liver and is slightly lower than the left.
- - The ureter, renal blood vessels, lymphatics and nerves all join each kidney at the hilium and occupy the sinus.
- 3 layers of supportive tissue around each kidney:
- -renal fascia
- -perirenal fat capsule
- -thin fibrours capsule
- Main function:- Main excretory organ
- -Regulates volume and chemical makeup of blood.
- -maintain proper balance between water/salts and acids/bases
- -regulates blood pH
- -Metabolise vitamin D
Structure and function of a nephron:
- -structural and functional units of the kidneys
- -consists of a glomerulus and a renal tubulse
- -Renal tubule has a cup shaped end which surrounds the glomerulus
- - Together these form the renal corpsule
- -Remainder of renal tuble is 3cm long and has 3 parts.
- -It leaves the glomerular capsule as the coiled proximal convulted tubule makes a hairpin loop called the loop of henle, then winds and twists again as the distal convoluted tubule, before emptying into a collecting duct.
- -Blood processing
- -carry out processes that form urine