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Human Phys
Digestion
| Question | Answer |
|---|---|
| What is in the mouth? | - palate - uvula - tongue - teeth |
| What are the salivary glands? | - sublingual - submandibular - parotid |
| What is in the small intestines? | - duodenum - jejunum - ileum |
| What is in the large intestines? | - colon - cecum - rectum |
| What does proximal mean? | close to mouth |
| What does distal mean? | further away from mouth |
| How does the digestive system work? | - food enters mouth and goes down esophagus - digestion in stomach - absorption and secretion in small intestines and colon - hepatic portal vein to liver and heart - rectum moves feces to anus for excretion |
| Pancreatic bile duct | - secreted in an inactive form so they don't act on their own tissues |
| Small intestine | Single layer epithelial cells line gut, due to absorption Villi are protusions that increase SA Cripts at base of villi Goblet cells secrete mucus Enterocytes secrete hormones |
| The villus | - entire lining replaced every 5 days |
| Nutrient digestion | - carbs - starch - glycogen - disaccharides |
| Starch | Glucose polymer Amylose a-1,4 Amylopectin a-1,4 and a-1,6 |
| In the lumen | - lactose: glucose and galactose into glucose carrier with Na+ - sucrose: fructose into fructose carriers - starch: dextrins (a-dextrinase) and maltose/maltotriose (glucoamylase) into glucose carrier with Na+ |
| COH digestion and absorption | Lumen: fructose, glucose and galactose transport Na+ into intestinal epithelial cells and into interstital fluid K+ and Na+ through potassium channels into interstitial |
| Nutrient digestion 2 | Proteins: must be broken down to amino acids and peptides before being utilised |
| What happens in the stomach? | - site of initial protein hydrolysis - pepsinogen, from chief cells in gastric mucosa, converted to pepsin (active enzyme) by acidic environment |
| What is the role of the duodenum? | - any small peptides or amino acids liberated by stomach are sensed - duodenum releases cholecystokinin (CKK), that releases pancreatic peptidases |
| What are the endopeptidases? | Trypsinogen Chymotrypsinogen Pro-elastase |
| What are the exopeptodases? | Carboxypeptidase A Carboxypeptidase B |
| How are proenzymes activated? | In the lumen: enteropeptidase stimulates trypsinogen conversion to proenzyme trypsin |
| Terminal digestion | - endopeptidases - aminopeptidases - carboxypeptidases - dipeptidases convert oligopeptides into amino acids and di/tripeptides |
| How are amino acids and peptides absorbed? | - active transport coupled to Na+ or H+ - absorbed by facilitated diffusion |
| Nutrient digestion 3 | - iron (micronutrient) - not all iron from diet is absorbed |
| Where is iron stored? | - total iron content around 50mg/kg - 60% in haemoglobin - 25% in liver stores |
| How is ferric iron absorbed? | Dietary ferric iron (Fe3+) is reduced to Fe2+ and its entry is through the divalent metal cation transporter DMT1 |
| In the portal plasma? | Iron export to portal plasma is controlled by ferroportin Iron is oxidised before binding to transferrin in plasma |
| How is haem iron absorbed? | Haem is absorbed after binding to its receptor protein HCP-1 |
| How are fat droplets absorbed? | - emuslified by bile salts and PLs into micelles that are digested by pancreatic lipase |
| What are chylomicrons? | - drops of fat - processed and trafficked in the cell and exported to the lymph system and onto adipose tissue - specific transporters also exist for vitamins and minerals such as dietary iron |
Created by:
reub8n
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