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Order of anatomy of the digestive tract?
Mouth --> Esophagus --> Stomach --> Small intestine --> Larhe intestine --> Rectum --> Anus
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Where does digestion begin? What marcomolecule first begins digestion and with what enzyme?
Digestion begins in the mouth ; Digestion of startch (carb) with alpha-amylase
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What is the bolus transformed into in the stomach?
Chyme
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What kind of glands does the stomach contain?
Exocrine glands - known because they release enzymes
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Where does protein digestion start and with what enzyme?
In the stomach with pepsin
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4 cells in stomach and their actions
1. Mucous cells - lubrication+protection from pH
2. Chief cells - secrete pepsinogen
3. Parietal cells - secrete HCl
4. G cells - secrete gastrin (stimulate parietal cells to secrete HCl)
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Where does absorption occur?
Small intestine
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Parts of the small intestine and what occurs where
1. Duodenum - most digestion
2. Jejunum - absorption
3. Ileum - absorption
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Surface of small intestinal wall
Brush border (contains enzymes to break down carbs, proteins, and nucleotides)--> microvilli --> Villi (increase surface area for absorption) --> lacteal capillary network (site of nutrient absorption) -->
Exocrine glands within villi = secrete 7.6 intestinal juice
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Goblet cells
- Found in the small intestine, secrete mucus for protection
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What is the pH in the small intestine and why does it have its value?
pH of 6
Slightly basic compared to stomach because of bicarbonate ion
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What does the pancreas secrete through its exocrine abilities?
1. Bicarbonate ion to alter pH of duodenum
2. Trypsin, Chymotrypsin, Pancreatic amylase, Lipase, RiboandDeoxyribonuclease
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All enzymes released from pancreas are released as...
Zymogens! Activated by trypsin
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How are carbohydrates absorbed?
Broken down into di and trisaccharides by pancreatic amylase
Further broken to monosaccharides by brush border enzymes
Absorbed as monosaccharides
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Where is bile produced and stored? What are its functions?
Produced by the liver and stored in the gall bladder
Bile emulsifies fat in the small intestine, increasing its surface area and making it easier to be absorbed by enterocytes
Bile does NOT digest fat at all
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What is bilirubin?
Endproduct of Hb degradation
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What are the major functions of the large intestine?
- 1. Water absorption
- 2. Electrolyte absorption
- 3. Symbiotic hub for gut flora like E.Coli (produce Vitamins)
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What composes healthy poop?
- 1. Water
- 2. Dead bacteria
- 3. Fat
- 4. Inorganic matter
- 5. Protein
- 6. Roughage
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What do the hormones secreted by the small intestine do?
Increase blood insulin levels , peptide hormones
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Carbohydrate absorption
- 1. Broken down into monomers glucose, fructose, galactose
- 2. Absorbed via secondary active transport glucose absorbed into enterocyte with Na+)
- 3. Glucose move out of cell via facilitated transport from intestinal lumen --> enterocyte ... but passive/facilitated diffusion from enterocyte --> blood
- 4. Carried to liver
- 5. If max [glycogen] reached by cells, converted to fatty acids
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Where does the conversion of glucose to fat take place?
Liver + fat cells
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Protein absorption
- 1. Absorbed into enterocytes via active or facilitated transport
- 2. Cells immediately make protein from amino acids to keep amino acid [] low
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What is ammonia converted to and by what?
Converted to urea by the liver and then excreted by the kidney
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Energy in protein, carbs, and fat
Fat > Carbs > Protein
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Fat absorption
- 1. Separated by bile micells and broken down by lipase and brush border enzymes
- 2. Once in cell, fats re-converted into triglycerides at sER
- 3. Attached to apoproteins = chylomicrons
- 4. Exocytosed by cells
- 5. Move into lacteal of lymph system
- 6. Enter thoracic duct
- 7. Jugular Vein
- 8. Absorbed into liver and other cells
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Blood supply to liver
- 1. Nutrients: hepatic portal vein
- 2. Oxygen: hepatic artery
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8 jobs of the liver?
- 1. Blood reservoir
- 2. Blood filtration
- 3. Carbohydrate metabolism
- 4. Fat metabolism
- 5. Protein metabolism
- 6. Detoxification (lots of sER)
- 7. RBC destruction (but mostly by spleen)
- 8. Vitamin storage
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Albumin
osmoregulatory factor, binds to lipids to transport through blood
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How does oxidation of protein and fat by the liver affect blood pH?
pH will DECREASE, acidity increases
keto acidosis
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Functions of the kidney
- 1. Excretion of waste
- 2. Homeostasis
- 3. pH control
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Path of excretion
Urine created by kidnet and emptied into --> renal pelvis --> ureter --> bladder --> urethra
glomerulus --> Bowman's capsule --> PCT --> Loop of henle --> DCT --> collecting duct --> ureter
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What is the functional unit of the kidney?
Nephron
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What force allows glomerular filtration to occur?
Hydrostatic pressure
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What molecules are PREVENTED from filtering into the bowman's capsule through the glomerulus?
Blood cells and large proteins
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Where does most reabsorption in the kidney take place?
Proximal tubule
- 1. glucose, amino acids, vitamins, and water is reabsorbed
- 2. Toxins, uric acid, drugs, and H+ ions are secreted
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What is the job of the Loop of Henle?
To concentrate the renal medulla! This will allow for H2O absoroption later on...
Filtrate entering loop is more concentrated than filtrate exiting loop.
- Descending: water absorbed
- Ascending: Na+ absorbed
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What is the job of the distal tubule?
Lower filtrate osmolarity
Reabsorption of Na+ and Ca2+
Secretion of K+, H+, and HCO3-
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Where does aldosterone exert its effects?
Distal tubule
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What is the job of the collecting duct?
To concentrate urine
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Where does ADH exert its effects?
The collecting duct to increase permeability to water and concentrating the filtrate
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Water permeability in the loop of henle
Descending branch - permeable to water
Ascending - Impermeable to water
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RAA system
Renin secreted by kidney - acts as a catalyst because it's an enzyme
Adrenal cortex stimulated to secrete aldosterone
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Where does most mechanical and chemical digestion occur?
Mechanical: mouth
Chemical: Duodenum
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How do most fats enter circulation?
First converted to chylomicrons and shipped to lacteal lymph system to be deposted in thoracic duct
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Main effect on BP of the RAA?
Increase in systemic blood pressure
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