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47 Cards in this Set
- Front
- Back
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How are monosaccharides transported?
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Facilitated diffusion or active transport
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How are amino acids, dipeptides, and tripeptides transported?
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Active transport
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How are lipids absorbed from lumen of SI?
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Very short fatty chains by simple diffusion
Larger lipids incorporated into micelles |
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How are large lipids absorbed from lumen of SI?
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Incorporated in micelles
Fuse with plasma membranes of absorptive cells Release lipids inside absorptive cells Lipids aggregate, reassemble, and become coated with protein forming chylomicrons |
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How do chylomicrons leave absorptive cells?
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By exocytosis and enter lymph capillaries (lacteals)
From lymph they enter blood via lymphatic ducts |
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How are electrolytes mainly transported in SI?
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Active transport and diffusion
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What stimulates active transport of Ca2+?
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Calcitrol
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What vitamins are incorporated into micelles in the SI?
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Fat soluble A, D, E, and K
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How do water soluble vitamins leave absorptive cells?
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Most B and vitamin C by simple diffusion
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How is B12 absorbed in the lumen?
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B12 combines with intrinsic factor and is absorbed in the ileum
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How is water absorbed?
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Osmosis
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About how long is the large intestine is a living adult?
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About 5 feet
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Rectum is how long in a living adult?
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about 6 inches
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Mucosa of large intestine made up of what?
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Simple columnar epithelium– mostly absorptive and goblet cells. Located in tubular intestinal glands
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Absorptive cells (with microvilli) primary function
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Mostly absorb water
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Solitary lymphatic nodules of the mucosa may extend into the ____.
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Submucosa
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Muscularis of the large intestine anatomy
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External longitudinal muscle and internal circular smooth muscle
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Portions of longitudinal muscle are thickened forming bands called the ____.
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Teniae coli
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Contractions of the teniae coli gather the colon into pouches called ___.
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Haustra
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Passage of chyme from ileum to cecum is regulated by what?
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ileocecal sphincter (usually partially closed)
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After a meal, what reflex occurs?
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Gastroileal reflex
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What does the gastroileal reflex do?
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Increases contractions in the ileum and opens the ileocecal valve moving chyme into the cecum
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Haustral churning caused by what?
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Distension reaches a certain point and the walls of the haustra contract to mix and squeeze contents onward
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Peristalsis
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Propulsive contractions
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Mass peristalsis
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strong peristaltic wave that begins in the transverse colon and quickly drives the contents of the colon into the rectum
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What in the large intestine that completes digestion?
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Bacteria
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Carbohydrates are _____ by bacteria
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fermented
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Bilirubin is decomposed to ___ and other pigments by bacteria
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stercobilin
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What vitamins are synthesized by bacterial metabolism?
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Some B vitamins and vitamin K
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What does the colon absorb?
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Water, electrolytes, and some vitamins
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After chyme has been in the colon 3–10 hours what does it become?
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Feces
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Defecation reflex regarding rectal wall
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Distends
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Defecation reflex regarding stretch receptors
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Send sensory nerve impulses to the sacral spinal cord
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Defecation reflex regarding motor impulses
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Travel back to large intestines
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Longitudinal rectal muscles ___ and the internal anal sphincter ___.
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Contract
Opens |
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What occurs when the external anal sphincter is voluntarily relaxed?
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Defecation
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Cephalic stage of digestion
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Smell, sight, thought, and initial taste of food activates centers in the cerebral cortex hypothalamus and brain stem.
Brain stem stimulates cranial nerves which increase salivation and gastric juice secretion. |
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Neural response during gastric phase once food reaches the stomach
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Presence of food stimulates stretch receptors.
Increase in pH stimulates chemoreceptors |
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Neural receptors in gastric phase (once food reaches the stomach) activate what?
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Parasympathetic and enteric neurons, stimulate peristalsis, and flow of gastric juice.
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Hormonal mechanisms of the gastric phase (once food reaches the stomach)
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Gastrin is secreted in response to distension of the stomach, increased pH, and partially digested proteins
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What does gastrin stimulate?
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Secretion of gastric juice and increased motility of the stomach
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Intestinal phase of digestion. Neural.
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Distension of duodenum causes enterogastric reflex.
Stretch receptors send impulses to the medulla and stimulate sympathetic output to the stomach decreasing gastric motility |
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Hormonal mechanisms of intestinal phase
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Cholycystokinin (CCK) secreted by intestinal glands in response to partially digested food
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Why is CCK (cholycystokinin) secreted?
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in response to partially digested food (by the intestinal glands)
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What does CCK (cholycystokinin) stimulate?
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Secretion of pancreatic juice
Contraction of gallbladder Relaxation of sphincter of Oddi Feeling of satiety |
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What stimulates secretin to be secreted from intestinal glands?
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Acidic chyme
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What does secretin stimulate?
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Flow of pancreatic juice and bile
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