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157 Cards in this Set
- Front
- Back
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What are the two types of digestion?
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Mechanical and Chemical
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What are the two functions accomplished by motility?
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Mixing and Propelling
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Describe the extrinsic component of the Digestive System?
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Both divisions of the autonomic nervous system
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What is the intrinsic component?
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The enteric nervouse system
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Where are the ganglia for the enteric nervous system found? (2 places)
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1. The submucosal plexus
2. The myenteric plexus |
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What innervates the longitudinal muscle of the muscularis externa?
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Parasympathetics only
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What innervates the circular smooth muscle of the muscularis externa?
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Sympathetics only
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What are the main functions of the parasympathetics in the digestive system?(2)
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1. Increase motility
2. Produce digestive secretions |
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Parasympathetics to the upper digestive tract are supplied by?
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Vagus nerve (CN X)
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Parasympathetics to the lower digestive tract are supplied by?
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Pelvic nerve
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what two plexuses are innervated by parasympathetics?
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1. The submucosal plexus
2. The myenteric plexus |
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What 3 end organs are stimulated by parasympathetics?
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1. Smooth muscle
2. Endocrine cells 3. Exocrine cells |
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What are the parasympathetic afferents from the digestive system coming from? (3)
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1. mechanorecepters
2. osmoreceptors 3. chemoreceptors |
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What are the neurotransmitters used by parasympathetics in digestive system?
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Acetylcholine and Peptides (substance p, VIP)
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What are the two functions of the sympathetic nervous system in the digestive system?
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1. Decrease motility
2. Decrease digestive secretions |
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What are the 4 sympathetic ganglia associated with the digestive system?
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1. Celiac
2. Superior mesenteric 3. Inferior mesenteric 4. Hypogastric |
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What are the two plexuses innervated by sympathetics in the digestive tract?
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1. Submucosal
2. Myenteric |
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What are the sympathetic afferents from the digestive system coming from? (3)
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1. mechanorecepters
2. osmoreceptors 3. chemoreceptors |
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What 3 end organs are stimulated by sympathetics?
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1. Smooth muscle
2. Endocrine cells 3. Exocrine cells |
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What are the neurotransmitters used by sympathetics in the nervous system?
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Norepinephrine
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What can be said about the differences of the sympathetic and parasympathetic nervouse system contributions to the digestive system innervation?
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They use different neurotransmitters and they have different ganglia, otherwise they innervate and recieve infor from the same stuff
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What is the function of the intrinsic (enteric) nervous system in the digestive tract?
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Does everything that parasympathetics and sympathetics do
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What neurotransmitters does it use?
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all of the ones for both parasympathetics and sympathetics, plus a few more (enkephalins, Gastrin-releasing polypeptide(GRP), Neuropeptide Y)
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what does acetylcholine do in the digestive system? (3)
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1. Contracts smooth muscle in gut wall
2. Relaxes sphincters 3. Increases salivary, gastric, and pancreatic secretions |
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What does norepinephrine do in the digestive system? (3)
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1. Relaxes smooth muscle of gut wall
2. Contracts sphincters 3. Increases mucus content of saliva |
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What does VIP do in the digestive system? (2)
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1. Relaxes smooth muscle of gut wall
2. Increases pancreatic and small intestine secretions |
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What does GRP do in the digestive system? (1)
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1. Increases gastrin production
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What does Enkaphalin do in the digestive system? (2)
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1. Contracts smooth muscle of gut wall
2. Decreases intestinal secretions |
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What does Neuropeptide Y do in the digestive system? (2)
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1. Relaxes smooth muscle of the gut wall
2. Decreases intestinal secretions |
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What does substance P do in the digestive system? (2)
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1. Contracts smooth muscle
2. Increases salivary secretions |
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What is formed when food is mixed with saliva during mechanical digestion in the opral cavity?
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Bolus
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What stimulates the involuntary relfex for mastication?
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The presence of food
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How does the brain know food is present?
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Mechanoreceptors in the soft palate, gums, and tongue
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What nerve carries afferent signals from the mechanoreceptors to the brain stem?
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CN V
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What are the 3 phases of deglutition?
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1. Oral
2. Pharyngeal 3. Esophageal |
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Which phase is under voluntary control?
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Oral
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Where is the swallowing center located in the brain?
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Medulla
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What are the afferent nerves involved in the pharyngeal phase?
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CN V, X, XII
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What are the efferent nerves involved in the pharyngeal phase?
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CN V, IX, X, XII
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What keeps the bolus from entering the nasopharynx?
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Soft palate is pulled upward
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What keeps bolus from entering the larynx?
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Epiglottis covers the glottis
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What must relax in order for food to enter the esophagus?
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The upper esophageal sphincter (UES)
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What is the primitive swallowing reflex found in infants that is activated by blowing on their face?
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Santmyer Swallow
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What is the nerve that is associated with this reflex?
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CN V
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What leads to the timely, periodic contraction of smooth muscle in the GI tract?
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Spontaneous slow wave activity
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Where do slow waves originate?
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The interstitial cells of Cajal
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Where are these cells most abundant?
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Myenteric plexus
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What part of the alimentary canal is not thought to be influenced by these cells of Cajal?
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The esophagus
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Why are the spontaneous impulses created by the cells of Cajal rapidly paced on to smooth muscle?
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They are connected via gap junctions (electrical coupling)
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The faster initial depolarization of the slow wave?
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Inward Ca2+ movement through Voltage-gated channels
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What is responsible for the depolarized plateau of the slow waves?
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inward movement of Ca2+ through the opening of L-type Ca2+ channels (slow movement of Ca2+)
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What causes the repolarization of the slow wave?
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outward movement of K+ via voltage-gated K+ channels
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What dictates the tension of the smooth muscle which is undergoing slow waves?
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The number of action potentials at the depolarized plateau
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What two factors causes an increase in the number of action potentials generated?
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1. Greater depolarization waves
2. Longer depolarization plateau |
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What is the product of slow waves that do not completely reach threshhold?
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Weak contractions
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What is the slowest frequency of the slow waves in the body and where is it found?
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3 per minute in the stomach
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What is the fastest frequency of slow waves in the body and where is it found?
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12 per minute in the duodenum
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Describe the neural and hormonal input which control the number of slow waves?
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Trick Question! There are none. The only factor influencing the number of slow waves are the cells of Cajal
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What can nueral and hormonal input influence which is associated with the slow waves?
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The number of action potentials generated (thus contraction strength
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What is the purpose of phasic contractions? (2)
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1. Propel
2. Mix |
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What can inhibit deglutition?
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Rapid swallowing
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What is caused by primary periostaltic contraction at the end of the esophagus?
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Relaxation of the lower esophageal sphincter
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What clears the rest of the bolus from the esophagus after the primary contractions are finished?
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Secondary contractions
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Describe the two types of muscular contractions needed to force food down the esophagus?
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Circular muscle contract in series followed by the ontraction of the longitudinal muscle to shorten the esophagus pushing the food down
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What mediates the relaxing of the LES?
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The vagus nerve
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What else is caused to relax by the vagus nerve?
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The orad region of stomach
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What is the coinciding relaxation with peristaltic activity called? (Know)
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Receptive Relaxation
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What type of contraction is found in sphincters?
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Tonic contraction
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Where do secondary contractions begin in the esophagus?
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At the point of distention cause by remaining bolus
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What mediates secondary contractions?
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Enteric nervous system thus they are a intrinisic neuromuscular reflex
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The pharynx and upper part of the esophagus are composed of what type of muscle?
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Skeletal
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The bottom and middle part of the esophagus is compose of?
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smooth muscle
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What are the 3 major parts of the stomach?
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1. Fundus
2. Body 3. Antrum |
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The fundus and the upper part of the body constitute the ____ region?
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Orad
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The Antrum and the lower part of the body constitute the ___ region?
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Caudad
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Describe the direction of contractions in the Caudad region?
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From Body to Antrum
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What is produced from the mixing of broken up bolus and digestive enzymes in the stomach?
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Chyme
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If chyme is not ready to enter the duodenum, what happens at the pyloric sphincter?
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It undergoes retropulsion (muscular contractions forcing it back to the body of the stomach for more mixing)
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How long does it take to empty the stomach after a meal?
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3 hours
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Which type of chyme exits most readily? Isotonic, hypotonic, or hypertonic?
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Isotonic so it will not upset osmotic pressure in small intestine
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Which food type exits the stomach the fastest?
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Carbohydrates
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Which food type exits the stomach slowest?
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Lipids
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What causes periodic contractions during times of fasting to clear stomach of remaining chyme?
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Migrating myoelectric complexes
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What controls migrating myoelectric complexes?
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the hormone, Motilin
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What is the frequency of these contractions?
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once every 90 minutes
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What is the initial step in the production of saliva?
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The secretions of an isotonic plasma-like solution by acinar cells
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What modifies acinar salivary secretions before they are released into the oral cavity?
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Ductal cells
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Ductal cells cause salivary secretions to be?
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Hypotonic
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What is contained on the lumen surface of a ductal cell? (3)
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1. Na+ / H+ exchanger
2. Cl- / HCO3- exchanger 3. K+ / H+ exchanger |
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What is contained in the basal membrane (faces the blood)? (2)
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1. Na+ / K+ ATPase
2. Cl- Channels |
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What do ductal cells secrete into saliva?
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K+ and HCO3-
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What do ductal cells remove from saliva?
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Na+ and Cl-
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Do ductal cells secrete more ions or remove more ion from the saliva?
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Remove more (Na+ and Cl-) thus forming a hypotonic solution
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What is the unique characteristic of ductal cells that allows them to create hypotonic saliva?
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They are impermeable to water thus removing Na+ does not mean removing water
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What are the 4 components of saliva?
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1. Salivary amylase
2. Lingual lipase 3. Mucin Glycoprotien 4. Antibacterials |
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What percentage of carbohydrate digestion is done by salivary amylase?
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5%
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Does salivary amylase continue to work in the stomach?
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No it is inactivated
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What produces lingual lipase? (2)
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1. Ebners Glands
2. Parotid Gland |
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Does lingual lipase continue to work in the stomach?
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Yes
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To whom is lingual lipase most important?
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Children (esp. infants who are breast feeding), only a minor role in adults
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What are the antibacterials that can be found in saliva? (2)
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1. IgA
2. Lysozyme |
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What secretes gastric acid?
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The parietal cells of the stomach
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What are the 3 functions of gastric acid?
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1. Convert pepsinogen into pepsin
2. Break down CT in meats 3. Kill bacteria |
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Describe the production of gastric acid begining with aerobic metabolism in parietal cells
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1. aerobic metabolism produces CO2
2. CO2 is converted into H+ and HCO3- by carbonic anhydrase 3. HCO3- is transported into blood for Cl- 4. H+ is transported into stomach in exchange for K+ 5. Cl- follow H+ into stomach via Cl- channels |
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What is the phenomenon of increased blood pH during gastric acid formation?
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Alkaline Tide
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What is an inhibitor of the proton pumps on the lumenal side of the parietal cells?
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Prilosec
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What are the 4 components of gastric secretions?
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1. Pepsinogen
2. Intrinsic Factor 3. Gastric Lipase 4. Mucus |
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What produces and secretes pepsinogen?
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Chief Cells
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At what pH does pepsiongen become activated?
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3 or below
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What is intrinsic factor needed for?
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The proper absorbtion of vitamine B12 in the ileum
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If intrinsic factor is not produced, what disorder happends?
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Pernicious Anemia
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What produces and secretes gastric lipase?
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Cheif Cells
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What is the importance of this enzyme in adults?
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Small role in lipid digestion
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What cells produce intrinsic factor?
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Parietal Cells
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What cells produce gastrin?
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G cells
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Where are G cells found?
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In the Antrum
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Where are mucus cells in the stomach?
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In the Antrum
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Where are parietal and cheif cells found in the stomach?
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In the Body
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What is the initial step in the production of the aqueous component of the pancreatic secretions?
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Formation of an isotonic solution by centroacinar cells
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What modifies the isotonic solution by centroacinar cells in the formation of pancreatic secretion?
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Ductal cells
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Where does the plasma like solution for pancreatic secretion come from?
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Blood filtrate
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What modifies the blood filtrate that will become pancreatic secretions
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Ductal cells
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Describe the luminal transport protiens of the pancreatic ductal cells?
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Cl- / HCO3- exchanger
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Describe the basal transport proteins of the pancreatic ductal cells? (2)
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1. Na+ / K+ ATPase
2. Na+ / H+ exchanger |
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Describe the process by which pancreatic secretions become alkaline?
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Same process as with production of gastric acid except the H+ goes to the blood and the HCO3- goes to the lumem.
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What does this cause to happen to pancreatic venous blood?
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Makes it more acidic than normal
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What are the 3 enzymatic components to pancreatic secretion?
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1. Pancreatic Amylase
2. Pancreatic Lipase 3. Pancreatic Proteases and Peptidases |
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In what form are pancreatic lipase and amylase secreted?
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Active form
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List the inactive pancreatic proteases and peptides secreted by the pancrease? (5)
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1. Trypsinogen
2. Chymotrypsinogen 3. Proelastase 4. Procarboxypeptidase A 5. Procarboxypeptidase B |
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What is trypsinogen activated by?
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Enterokinase
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What are the pancreatic enzymes other than trypsinogen activated by?
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Trypsin
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What breaks down sucrose?
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Sucrase
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What breaks down Lactose?
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Lactase
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What breaks down Starches?
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alpha-amylase
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What is composed of two glucose molecules bound together that can be found in mushrooms and shrimp?
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Trehalose
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Oligopeptides produced in the stomach are broken down by what in the small intestine?
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Luminal Pancreatic Proteases and Peptidases
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Where can non-pancreatic peptidases be found in the small intestine?
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Peptidases in microvilli of small intestine epithelium
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What are the carbohydrates which can be absorbed through the small intestine? (3)
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1. Glucose
2. Galactose 3. Fructose |
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What transports glucose into the epithelial cells?
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SGLT 1 Na+ / Glucose cotransporter (Secondary Active Transport)
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What transfers glucose into the blood from the intestinal epithelial cells?
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GLUT 2 Transporter (Facilitated Diffusion)
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What brings galactose into intestinal epithelial cells?
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SGLT 1 Na+ / Galactose Cotransporter (Secondary Active Transport)
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What transfers galactose into the blood from the intestinal epithelial cells?
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GLUT 2 Transporter (Facilitated Diffusion)
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What brings fructose into intestinal epithelial cells?
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GLUT 5 transporter (Facilitated Diffusion)
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What transports Fructose from intestinal epithelial cells into blood?
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GLUT 2 Transporter(Facilitated Diffusion)
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What establishes the Na+ gradient needed to draw in glucose and galactose?
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Na+ / K+ ATPase
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While galactose is always converted into glucose (or else galactosemia), why is fructose sometimes allowed to stay unconverted?
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Sperm use it preferentially to glucose
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Describe the three components of Protein absorbtion?
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1. Amino Acids
2. Dipeptides 3. Tripeptides |
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How are amino acids brought into intestinal epithelial cells?
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Na+ / Amino Acid Cotransporters (Secondary Active Transport
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Describe how the cell deals with differently charged AA's and imino amina acids?
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It has a different cotransporter on the apical membrane for each and a different AA transporter for each on the basolateral membrane
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How are amino acids brought out of the intestinal epithelial cells?
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Facilitated diffusion via AA tranporter
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Most protein absorbtion in the small intestine is in the form of?
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Dipeptides and Tripeptides
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How are dipeptides and tripeptides brough into small intestine epithelial cells?
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Via H+ / Peptide cotransporter with a different cotransporter for di or tripeptides
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What converts imported peptides into AA in small intestine epithelium?
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Peptidases, AA are then transported out of the cell via facilitated diffusion mediated by AA transporter
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All products of lipid digestion are said to be contained in what?
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Micelles
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What are the 5 steps in lipid absorbtion?
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1. Digested Lipids are surrounded by bile salts until the get to the epithelial lining
2. lipids are released from micelles and diffuse into epithelial cells 3. Re-esterification occurs (reforms lipid as it was ingested) 4. Lipids then chylomicrons and are packeged by golgi 5. Chylomicron-containing-vesicles undergo exocytosis at the basal membrane |
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Describe a chylomicron?
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Outer shell made of phospholipids and apoproteins, Inner core of cholesterol esters and triglycerides
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After exocytosis from intestinal epithelium, where do chylomicrons go?
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Lymphatic Lacteals
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