Term
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Definition
-mixing chamber and holding reservoir
-continuation of starch digestion
-digestion of proteins and triglycerides
-bolus converted to liquid
-certain substances absorbed |
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Term
| 4 district regions of the stomach |
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Definition
1. mucosa
-simple columnar / lamina propria / mm muscosa / gastric glands (mucous neck, parietal, chief cells) / gastric juices (2000-3000ml/per day) / enteroendocrine (G cells)
2. submucosa: areolar connective tissue
3. muscularis: 3 layers of smooth mm / outer-longitudinal; middle-circular; inner-oblique
4.serosa: simple squamous epithelium (mesothelium) / areolar connective tissue / portion of visceral peritoneum |
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Term
| how does mechanical digestion work |
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Definition
-peristaltic movements: mixing waves; creates chyme (liquid material)
- less movement; greater movement (fundus / body / pylorus / gastric emptying: 3 ml of chyme from pylorus into duodenum / remaining chyme returns into the body of the stomach-continued mixing |
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Term
| how does chemical digestion work |
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Definition
-salivary amylase still effective if food that is not mixed with gastric acid remains in the fundus
-gastric (inactive salivary amylase / actives lingual lipase; digestion of triglycerides into FA and diglycerides)
-parietal cells: secretes H+ and Cl = HCI
-proton pumps (H+/K+ ATPase) transports H+ into lumen while K+ into cells / Cl and K+ diffuse out into the lumen through Cl and K+ channels in the apical membrane
-formation of H2CO3 (carbonic acid): carbonic anhydrase H20C02 / HCO3 exchanges for Cl
- HCI secretion can be stimulated by several sources: EACh release by Ps neurons / Gastrin secretion by G cells / histamine secretion by mast cells
-receptors for all 3 substances present in the plasma membrane of parietal cells
-pepsin-secreted by chief cells: only proteolytic enzyme in stomach / most effective in acidic environments (pH2) / inactive with higher pH
-Pepsinogen (inactive form in pH 5-6)
-gastric lipase: splits triglycerides into FA and MG / limited role/active in ph 5-6 |
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Term
| small intestine function and size |
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Definition
-function: digestion and absorption of nutrients
-size: diameter 2.5cm length 3m |
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Term
| circular folds (plica circulares) location and significance |
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Definition
location: duodenum (proximal) - ileum (midpoint)
significance: enhance absorption |
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Term
| villi location and significance |
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Definition
location: surrounding epithelium; core lamina propria
significance: contains arterioles, venues, capillaries, lacteals
increase SA of epithelium for absorption and digestion |
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Term
| microvilli location and significance |
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Definition
location: brush border w/ enzymes extends into the lumen
significance: projections of absorbtive cells |
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Term
| intestinal juice: amount per day / what it contains & function |
|
Definition
-1-2L per day
-contains water and mucus - slightly alkaline
-function: provides medium to aid the absorption of chyme and works with pancreatic juices |
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Term
| what is brush border enzymes & what types of enzymes does is contain |
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Definition
- its a the plasma membrane of absorptive cells
-4 carb digesting enzymes
-2 protein digesting enzymes
-2nucleotide digesting enzymes |
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Term
| Small I mechanical digestion segmentation |
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Definition
Localized, mixing contractions
Mix chyme with digestive juices and allows it to contact with
the mucosa for absorption
Duodenum (12 times/min)
Ileum (8 times/min) |
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Term
| Small I mechanical digestion migrating motility complex (MMC) |
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Definition
Slow peristalsis
Begins in stomach (lower portion)
Reaches ileum within 90-120 min |
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Term
| Small I chemical digestion (what does it digest) |
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Definition
| carbs / proteins / lipids / nucleic acids |
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Term
| how are carbs digested in the Small I |
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Definition
Salivary amylase: inactive in stomach (acidic pH)
Pancreatic amylase: breaks down maltose, maltotriose, and
α-dextrins
No effect on cellulose
α-dextrinase (BBE)
Sucrase, lactase, maltase (BBE)
Digests the disaccharides into monosaccharides
Digestion of carbohydrates ends with the production of
monosaccharides |
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Term
| how are proteins digested in the Small I |
|
Definition
Pepsin
Pancreatic enzymes: trypsin, chymotrypsin,
carboxypeptidase, and elastase
Each splits peptide bonds bw different amino acids
Brush-border enzymes: Aminopeptidase and Dipeptidase
Each splits dipeptides into single amino acids |
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Term
| how are lipids digested in the Small I |
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Definition
Lipases – enzymes that split triglycerides and
phospholipids
Lingual lipase, gastric lipase – digestion in stomach
Pancreatic lipase – digestion in small intestine
Emulsification – large lipid globule is broken down into
several small lipid globules
Bile salts are amphipathic – allows for emulsification of large
lipid globule |
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Term
| how are nucleic acids digested in the Small I |
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Definition
Pancreatic juices
Ribonuclease: digests RNA
Deoxyribonuclease: digests DNA
Brush-border enzymes: Nucleosidases and phosphatase
Nucleotides digested into pentoses, phosphates, and
nitrogenous bases |
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Term
| ratio of digestion Small/large I |
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Definition
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Term
| Small I absorption (monosaccharides) process |
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Definition
Abundant levels of monosaccharide absorption
Most dietary carbohydrates digested are absorbed
120 grams/hr
Only cellulose and fibers are indigestible
Absorbed via facilitated diffusion or active transport from
the lumen through the apical membrane in absorptive cells
From absorptive cells --> capillaries of the villi |
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Term
| how are nutrients absorbed |
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Definition
diffusion, facilitated diffusion, osmosis, and active
transport |
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Term
| small I absorption (protein) process |
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Definition
½ of absorbed a.a found in food
½ of absorbed a.a found in body
95% of proteins present in small intestine is digested and
absorbed
Absorbed via active transport into absorptive cells
Duodenum and jejunum
From absorptive cells, aa go through simple diffusion into
capillaries of the villi |
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Term
| small I absorption (lipids) process |
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Definition
95% of lipids in small intestine is digested/absorbed
Emulsification and digestion: triglycerides |
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Term
| small I (electrolyte) absorption process |
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Definition
-from GI secretions of food
-Na+ reclaimed by active transport
-other ions also absorbed by active transport |
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Term
| small I (vitamin) absorption process |
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Definition
-fat soluble vitamins (a,d,e,k): simple diffusion and transported with lipids in micelles
-most water soluble vitamins also absorbed by simple diffusion |
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Term
| (water) absorption process |
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Definition
-9.3l comes from ingestion (2.3l) and Gi secretions (7l)
-absorbtion: SI: 8.3L LI:0.9L
all water absorption by osmosis |
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Term
| large intestine size and function |
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Definition
size: diameter: 6.5cm length: 1.5 meters
completion of absorption, production. of certain vitamins, formation and expulsion of faces from the body |
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Term
| what are the 4 major regions of the large intestine |
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Definition
-cecum
-colon
-rectum
-anal canal |
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Term
| large intestine histology mucosa |
|
Definition
1. Muscosa (Simple columnar epithelium)
-Absorptive cells: Water absorption
-Goblet cells: Secretes mucus – lubricates passageway
-Lamina propria (areolar connective tissue): Solitary lymphatic nodules
-Muscularis mucosae (smooth muscle)
-No structural adaptations that increase SA
2. Submucosa
-Areolar connective tissue
3. Muscularis
-Smooth muscle (longitudinal and circular)
-Teniae coli – 3 longitudinal bands
-Haustra – series of pouches formed by contractions of
the teniae coli
4. Serosa
-Omental (fatty) appendices (viseral peritoneum) |
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Term
| what is gastroileal reflex |
|
Definition
-passage of chyme from ileum to cecum
-ileocecal sphincter (gastrin-relaxant) |
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Term
| large intestine mechanical digestion process |
|
Definition
1. Gastroileal reflex
-Passage of chyme from ileum to cecum
-Ileocecal sphincter (gastrin – relaxant)
2. Hautral churning
-Haustra relaxed until filled (contraction starts)
3.Peristalsis
-Slow rate (3-12 contraction per min)
4. Mass Peristalsis
-Forces colon contacts (quickly) toward rectum |
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Term
| large intestine chemical digestion process |
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Definition
1. Final Stage: Digestion through bacterial action
2. Occur in the colon
3. Mucus is secreted, but no enzymes
4. Fermentation of remaining carbohydrates
- Release H+, CO2, methane gases (flatulence)
- Produce Vitamin B and K
5. Absorption: water w/ ions and some vitamins
6. Feces: chyme remaining for 3-10 hrs
-Water, inorganic salts, epithelial cells from mucosa of GI, bacteria, unabsorbed digested materials, indigestible food |
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Term
| process of the defecation reflex in large intestine |
|
Definition
1. Emptying the rectum.
2. Distension in rectal wall / sensory nerve impulses to
sacral spinal cord / motor responses back to the colon
/ contractions in rectal muscles & voluntary
contractions of diaphragm and abdominal muscles /
opens anal sphincter.
3. Diarrhea
- Increase in frequency , volume, and fluid content
4. Constipation
- Infrequent or difficult defecation |
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