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human physio > Digestive > Flashcards

Digestive Flashcards

1
Q

Functions of Digestive system

A
  1. motility
  2. secretion
  3. digestion
  4. absorption
  5. storage and elimination
  6. immune barrier
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2
Q

Motility

A

physical breakdown, preogresses through the 30 feet from mouth to rectum, movement of food trhoguh digestive tract

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3
Q

Movement of food through digestive tract

A
  1. ingestion (eating)
  2. mastication (chewing)
  3. deglutition (swallowing)
  4. peristalsis and segmentation
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4
Q

Secretion

A

both exocrine/endocrine secretions

exocrine: water, HCl, bicarbonate, and digestive enzymes are secreted into lumen of GI tract
endocrine: stomach and small intestine secrete hormones that help regulate the digestive system

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5
Q

Digestion

A

breakdown of food molecules into smaller subunits: allowing them to be absorbed

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6
Q

Absorption

A

passage of digested end products into lymph/blood

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7
Q

Storage and elimination

A

temporary storage and subsequent elimination of indigestible food molecules

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8
Q

Immune barrier

A

columnar epithelium provides physical barrier to penetration of pathological organisms/ their toxins- cells of immune system reside in connective tissue located under epithelium to promote immune response

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9
Q

Anatomy of digestive system

A

tube system of 4 layers

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10
Q

4 layers of digestive system

A
  1. mucosa
  2. submucosal layer
  3. muscular tissue
  4. serosal layer
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11
Q

mucosa

A

inner layer next to lumen, primary absorptive epithelium, major absorptive layer and secretary layer

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12
Q

submucosal layer

A

involves immune, nervous tissues, lymph tissues and other connective tissues (these give it strength/ flexibility)

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13
Q

Muscular tissue

A

Made up of circular muscle and longitudinal muscle

i. circular muscle contracts
ii. longitudinal muscle helps move things (motility)

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14
Q

Serosal layer

A

provides blood supply, connective tissue that holds the 30 ft of GI tract together.

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15
Q

First stage: chewing through swallowing to stomach

A

chewing (mastication)–> mixes food wiht saliva secreted by salivary glands

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16
Q

saliva

A

contains mucus and various antimicrobial agents as well as salivary amylase

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17
Q

salivary amylase

A

enzyme that can catalyze partial digestion of starch

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18
Q

Swallowing

A

deglutition, divided into 3 phases: oral, pharyngeal, esophageal (oral is voluntary, pharynx/esophageal are automatic)

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19
Q

Middle and lower esophagus are

A

smooth and innervated by autonomic neurons

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20
Q

Swallowing phases

A

oral

pharyngeal

esophageal

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21
Q

Oral phase

A

First phase of swallowing:
muscles of mouth/tongue mix food with saliva and create a bolus of food, size to be swallowed. Tongue muscle moves it toward oropharynx–> receptors in posterior portion of oral cavity stimulate next phase

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22
Q

Pharyngeal

A

Second phase of swallowing:
soft palate lifts to close off the nasopharynx from oropharynx, prevents food from going out the nose, vocal chords close off to larynx, epiglottis covers vocal cords, llarynx moved away from bolus toward esophagus (prevents choking), upeper esophageal sphincter relaxes, this all takes <1 second

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23
Q

Esophageal

A

third phase of swallowing

lasts 5-6 seconds, bolus fo food moved by peristaltic contractions toward stomach

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24
Q

Stomach functions- role of acid

A
  1. Store food (Stomach very distensible and can accept bolus after colus)
  2. initiate digestion of proteins (pepsin activation)
  3. kill bacteria with strong acidity of gastric juice (pH = 2 so very acidic)
  4. move food into the small intestine as chyme.
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25
Q

Role of acid

A

HCl sterilizes the food we eat, preventing harmful bacteria into GI tract. Triggers the release of enzymes (pepsin) which are essential for protein digestion

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26
Q

Acid serves three functions

A
  1. ingested proteins denatured at low pH, so they become more digestible.
  2. In acidic conditions weak pepsinogen enzymes partially digest each other
  3. pepsin is more active under acidic conditions
  4. pepsin/HCl permits partial digestion of food in stomach
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27
Q

Mechanisms of stomach secretions

A

Inner surface of smooth contains rugae folds- gastric mucosa is also folded (Gastric pits) cells that line the folds secrete productsinto stomach (gastric glands)

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28
Q

Gastric glands

A

mucous neck cells, parietal cells, chief cells, ECL cells, G cells, D cells

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29
Q

Mucous neck cells

A

secrete mucus

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30
Q

Parietal cells

A

secrete HCl

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31
Q

Chief cells

A

secrete pepsinogen (inactive form of pepsin)

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32
Q

ECL cells

A

in stomach/intestine secrete histamine and serotonin as paracrine regulators of GI tract

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33
Q

G cells

A

secrete the hormone gastrin into the blood

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34
Q

D cells

A

secrete hormone somatostatin

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35
Q

Gastric mucosa (parietal cells) secrete

A

a polypeptide intrinsic factor which is required for intestinal absorption of vitamin B12 (necessary for RBC production)

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36
Q

Stomach increases its secretion in anticipation of meal

A

entry of chyme into the duodenum stimulates secretion of hormones which make gallbladder contract, secretion of pancreatic juice, inhibition of gastric activity

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37
Q

Roles of Gastrin

A

hormone secreted by the stomach that stimulates the gastric secretion of HCl and pepsin

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38
Q

gastrin is secreted by

A

G cells

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39
Q

Gastrin does what?

A

Stimulates parietal cells to secrete HCl, stimulates chief cells to secrete pepsinogen, maintains structure of gastric mucosa

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40
Q

Gastrin can stimulate ECL cells

A

ECL cells secrete histamine serotonin, which can enhance stimulation of B12, activates chief cells, activates stomach muscles/motility, stimulate relaxing pyloric sphincter, activates pancreas secretions, activates gallbladder contraction, activates D cells–> somatostatin (acts as feedback loop to inhibit the production of G cells)

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41
Q

Importance of food bolus/stomach distention

A

Formed while chewing–> food mixed with saliva

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42
Q

When bolus is present

A

the esophageal pyloric sphincter opens allowing bolus to enter

43
Q

Bolus in stomach

A

presence of bolus stimulates secretion of acid and gastric juices and which begins process of further mixing the bolus–> presence of bolus sparks acid secretion

Mix of gastric juice/acid with food creates chyme. Stomach mixes/churns bolus until its chyme.

Stomach is place of storage–> its ability to distend and accept bolus after bolus of food allows for distention

44
Q

Distention activates

A

production of G cells which produce gastrin which Stimulates parietal cells to secrete HCl, stimulates chief cells to secrete pepsinogen, maintains structure of gastric mucosa

45
Q

Cells involved in stomach function

A

mucous cells, parietal cells, chief cells, g cells, d cells

46
Q

Mucous cells

A

secrete copious amounts of mucus that has bicarbonate that stick to tissue in contact with food

47
Q

Parietal cells

A

secrete H+ and Cl- as well as an intrinsic factor which plays an important role in absorption of vitamin B12

48
Q

Chief cells

A

secrete enzyme pepsinogen which is the inactive form of pepsing (protein-digesting enzyme)

49
Q

G cells

A

produce/secrete the hormone gastrin (hormone in blood supply–> receptors for gastrin are in stomach)

50
Q

D cells

A

secrete hormone somatostatin which acts as a negative feedback loop to inactivate production of G cells

51
Q

Somatostatin

A

acts as a negative feedback loop to inactivate production of G cells

52
Q

Pyloric sphincter

A

One of the most important human sphincter muscles is the sphincter pylori, a thickening of the middle layer of stomach muscle around the pylorus (opening into the small intestine) that holds food in the stomach until it is thoroughly mixed with gastric juices.

53
Q

Small intestine general anatomy

A

longest part of the GI system (12-14 feet) made up of three sections: 1. duodenum 2. jejunum 3. ileum

54
Q

Duodoenum

A

chemical digestion/absorption

55
Q

Jejunum

A

where most absorption occurs

56
Q

Ileum

A

colon. Absorption of H2O, electrolytes, bile, salts, vitamin B12

57
Q

Absorption occurs most rapidly because of

A

extensive foldings

58
Q

Microvilli

A

microscopic folds in mucosa, allows absorption to occur rapidly in small intestine

59
Q

Enterokinase

A

embedded in microvilli wall allows trypsinogen to get hydrolyzed to active form trypsin

60
Q

Sucrase

A

digests sucrose to glucose/fructose

61
Q

Maltase

A

digests maltose to glucose

62
Q

Lactase

A

digests lactose into glucose/galactose (lactose intolerance if unable)

63
Q

Aminopeptidase

A

produce free amino acids

64
Q

phosphatase

A

necessary for Calcium reabsorption, requires vitamin D

65
Q

Activation of small intestine

A

motility of small intestine activated by chyme, creates a slow peristalsis. Contractility is enhanced by chyme but it is also intrinsic, so it is happening the absence of food via pacemaker cells connected by gap junctions

66
Q

What does chyme in the small intestine activate?

A

Activates CCK, activates secreton hormong which inhibits: gastrin, HCl, and stomach motility–> activates insulin from pancreas (increases pancreatic secretion

67
Q

Functions of secretin and CCK

A

both are secreted by duodenum response to different stimuli and have different primary effects

68
Q

CCK function

A

secretion stimulated by protein and fat content of chyme. CCK then stimulates secretion of pancreatic juice enzymes that help digest these molecules. Partially digested proteins/fats stimulate CCK secretion which lowers as the chyme passes out of the duodenum into the jejunum

69
Q

Secretin function

A

After a meal when acidic chyme reaches duodenum secretin stimulates bicarbonate and water secretion from pancreatic ductules. Uses cAMP as a second messender–> potentiated by ACh using calcium as a second messenger to stimulate bicarbonate and water secretion. Bicarbonate entering chyme helps prtoect the duodenum mucosa and provides optimal pH environment for pancreatic juice digestive enzymes. HCl passes from stomach into the duodenum releasing secretin into bloodstream and stimulating pancreas to secrete water and bicarbonate into pancreatic ducts which drain into the duodenum. Inhibits secretion of gastrin which triggers initial release of HCl into the stomach–> delays gastric emptying

70
Q

Esophageal pyloric sphincter

A

sometimes called gastroesophageal sphincter, or pyloric sphincter. a ring of muscular tissue that when the bolus of food contacts the sphincter it allows the presentation f the bolus into the stomach.

71
Q

What functions are served by churning bolus into chyme?

A

Storage-distensible, antimicrobial function (Acidic) pH=2. Acid enables denature of proteins. Acid enables activation of pepsin from pepsinogen to degrade proteins.

72
Q

mucosal layer

A

Folds have these deep crevices, and coating all of this is a thick layer of mucus, and so you can see up near the top of the folds are mucus cells, that are secreting a thick layer of mucus pretty much all the time. Stimulated by the bolus entering the stomach, when the bolus comes in, that stimulates bolus cells to secrete more. So then we see a little farther down in these crevices are cells called parietal cells which secrete HCl
Light pink cells are the schematic parietal cells to show how HCl gets secreted into the lumen of the stomach
On the apical surface (inside surface) are K/H ATPases, primary active transport using energy of ATP hydrolysis to secrete hydrogen ions. Which come from carbonic anhydrase.
Carbonic anhydrase comes from red blood cells to move co2 like in the kidneys

73
Q

Major cells in stomach

A

Mucus cells- mucus +HCO3
Parietal cells- h+, cl-, intrinsic factor (b12)
Chief cells- pepsinogen pepsin (active form) which can feed back to form more
G cells- gastrin, secreted in response to protein/peptides (signals in stomach)

74
Q

The vagus nerve

A

stimulates g cells, chief cells, parietal cells

75
Q

Digestive enzymes in microvilli (brush border)

A 
enterokinase
lactase, sucrase, maltase
aminopeptidase
phosphatase
lipase
76
Q

Enterokinase

A

activates trypsinogen from trypsin

77
Q

Phosphatases

A

calcium absorption requires vitamin D

78
Q

Muscle activity in small intestine

A

slow peristalsis

segmentation-intrinsic pacemaker cells

79
Q

Colon (large intestine) anatomy

A

no villi- much smoother. Three patts, ascending( right) colon, transcverse colon, descending (left colon, sigmoid colon, rectum aanus

80
Q

Pancreas

A

endocrine gland secretes insulin and glucagon. Exocrine gland secretes bicarb and 20 enzymes

81
Q

Regulation of digestive system

A

enteric nervous system- presence of chyme, protein. Autonomic nervous system (vagus nerve) gut hormones.

82
Q

Intestinal regulation

A

enteric nervous system and hormones regulate motility. Reflexes: gastroileal, ileogastric; intestino-intestinal. paracrine regulation: ECL cells secrete serotonin and motilin.

83
Q

The presence of lipids and carbohydrates stimulates

A

CCK and GIP which inhibit chief cells (from producing pepsinogen) and parietal cells (from producing HCl) and peristalsis.

84
Q

Decreased pH stimulates during the intestinal phase

A

secretin, which contributes to inhibiting chief cells (from producing pepsinogen) and parietal cells (from producing HCl) and peristalsis.

85
Q

Stomach to intestine

A

chyme enters duodenum causing the release of CCK and secretin from duodenal enteroendocrine cells

86
Q

CCK

A

induces secretion of enzyme rich pancreatic juice

87
Q

secretin

A

causes the secretion of bicarbonate rich pancreatic juice

88
Q

Bile salts and to a lesser extent secretin transported via blood stream stimulate

A

liver to produce bile more rapidly

89
Q

CCK via blood stream causes

A

gall bladder to contract and hepatopancreatic sphncter to relax so that bile enters the duodenum

90
Q

What is the bottom-line message of Richards + Gumz’s review?

A

Circadian regulation of all body systems
Important of down-time
Central/peripheral “clocks”

How are physiological systems regulated and coordinated to optimize overall functions
Heart and lungs would regulate with endocrine system, and nervous system, ex: hypothalamaic adrenal

91
Q

Functions of the colon

A

absorb water, electrolytes and certain vitamins from the chyme it gets from SI. passes waste products out of the body through rectum

92
Q

Anatomy of the colon

A

descending, colon, peritoneum, ascending colon, transverse colon, sigmoid colon, rectum, anal canal

93
Q

Descending colon

A

stores food to be emptied into rectum . walls absorb water and remaining nutrients/vitamins from feces

94
Q

peritoneum

A

holds colon together. thin layer of tissue that supports abdominal organs

95
Q

ascending colon

A

carries feces from cecum superiorly along the right side of the abdominal cavity to the transverse colon

96
Q

cecum

A

first part of the colon between the small intestine and large intenstine

97
Q

Liver

A

monitors all the material coming through intestinal system, place where things like alcohol can be detoxified, where cholesterol metabolism si regulated. Blood is screened and old RBCs degrade and hemoglobin is metabolized. the site of the production of plasma proteins like albumin but also the proteins that are part of the blood clotting cascade

98
Q

Gallbladder

A

tissue-organ that stores bile and contraction of that duct can be regulated by the digestive process

99
Q

pancreas

A

has endocrine function through insulin secretion into the bloodstream and exocrine function via bicarbonate

100
Q

Enteric nervous system

A

neurons/glial cells organized into ganglia that are interconnectedby outer myenteric plexus (found along entire GI tract) and the inner submucosal plexus (located in small/large intestine). Intrinsic afferents= sensory neurosn that have theri cell bodies in the myenteric or submucosal plexuses and synpase with interneurons of ENS. Out number extrinsic afferents (Regulated by autonomic NS) emphasis is on local regulation of intestinal function. Recevies input formautonomic NS but it can and will operate independently of brain and spnal cord

101
Q

Bolus of chyme and GI regulation

A

stimulates intrinsic afferents-activates enteric interneurons which stimulate motor neurons

102
Q

Extrinsic afferents and different peptide hormones released from intestine alert brain to condition of gi tract

A

impt for CNS regulation of digestion and in both conscious/unconscious perceptions of food intake.

103
Q

ECL cells of intestinal mucosa and GI regulation

A

secrete serotonin which stimulates intrinsic afferents which conduct impulses into submucosal myenteric plexus and there activate motor neurons

104
Q

Primary function of GI hormones

A

maintain strucutre of their target organs by gastrin hormone

human physio (9 decks)

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