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A&P 2 > Lessons 15-17 > Flashcards

Lessons 15-17 Flashcards

1
Q

digestive system

A

organ system that processes food, extract nutrients, and eliminates residue

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2
Q

what are the five stages of digestion

A
  • ingestion
  • digestion
  • absorption
  • compaction
  • defecation
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3
Q

five stages of digestion: ingestion

A

selective intake of food

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4
Q

five stages of digestion: digestion

A

mechanical and chemical breakdown of food into a form usable by the body

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5
Q

five stages of digestion: absorption

A

uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph

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6
Q

five stages of digestion: compaction

A

absorbing water and consolidating the indigestible residue into feces

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7
Q

five stages of digestion: defecation

A

elimination of feces

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8
Q

mechanical digestion

A

physical breakdown of food into smaller particles

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9
Q

what are two examples of mechanical digestion

A
  • cutting and grinding action of the teeth
  • churning action of stomach and small intestine
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10
Q

what is the purpose of mechanical digestion

A

exposes more food surface to digestive enzymes

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11
Q

chemical digestion

A

a series of hydrolysis reactions that breaks dietary macromolecules into their monomers

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12
Q

what carries out chemical digestion

A

digestive nzymes produced by salivary glands, stomach, pancreas, and small intestine

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13
Q

what are the four main breakdowns of that occur in chemical digestion

A
  • polysaccharides to monosaccharides
  • proteins into amino acids
  • fats into monoglycerides and fatty acids
  • nucleic acids into nucleotides
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14
Q

what nutrients are ingested as usable material

A
  • vitamins
  • amino acids
  • minerals
  • cholesterol
  • water
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15
Q

what are the two subdivisions of the digestive system

A
  • digestive tract
  • accessory organs
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16
Q

digestive tract

A
  • 30ft long muscular tube extending from mouth to anus
  • mouth, pharynx, esophagus, stomach, small and large intestine
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17
Q

accessory organs of the digestive system

A
  • teeth
  • tongue
  • salivary glands
  • liver
  • gallbladder
  • pancreas
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18
Q

what are the four layers of the digestive tract innermost to outermost?

A
  • mucosa
  • submucosa
  • muscularis externa
  • serosa
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19
Q

what are the three layers of the mucosa?

A
  • epithelium
  • lamina propria
  • muscularis mucosae
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20
Q

what are the two layers of the muscularis external?

A
  • inner circular layer
  • outer longitudinal layer
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21
Q

what are the two layers of the serosa?

A
  • areolar tissue
  • mesothelium
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22
Q

mucosa of the digestive tract layers

A

lines the lumen

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23
Q

the epithelium of the mucosa what kind of tissue for most of the digestive tract

A

simple columnar

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24
Q

where is the mucosa not simple columnar tissue? what is it instead?

A
  • mouth through esophagus and the lower anal canal
  • stratified squamous
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25
Q

lamina propria of mucosa

A

loose connective tissue layer

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26
Q

muscularis mucosae of mucosa

A
  • thin layer of smooth muscle
  • improves efficiency of digestion and nutrient absorption
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27
Q

how does the muscularis mucosae improve digestion and nutrient absorption efficiency

A

tenses mucosa creating grooves and ridges that enhance surface area and contact with food

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28
Q

mucosa-associated lymphatic tissue

A
  • abundant in the mucosa
  • included lymphocytes and lymph nodes
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29
Q

submucosa of the digestive tract layers

A
  • thicker layer of loose connective tissue
  • contains blood and lymphatic vessels, a nerve plexus, and in some spots mucous secreting glands that dump lubricating mucus in the lumen
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30
Q

____ extends into the submucosa in some parts of the GI tract

A

MALT

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31
Q

inner circular smooth layer of the muscularis externa

A
  • cells encircle tract
  • responsible for the motility that propels food and residue through the tract
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32
Q

in some places the inner circular layer of the muscularis externa the layer thickens to form what?

A

valves that regulate the passage of material through the tract

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33
Q

serosa layer of the digestive tract is composed of

A

a thin layer of areolar tissue topped by simple squamous mesothelium

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34
Q

where does the serosa begin?

A

in the lower 3-4 cm of the esophagus and ends just before the rectum

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35
Q

some organs do not have serosa. what are they covered with instead?

A

adventitia

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36
Q

adventitia

A

fibrous connective tissue layer that binds and blends into adjacent organs

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37
Q

what parts of the digestive tract have adventitia rather than serosa

A
  • pharynx
  • most of the esophagus
  • rectum
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38
Q

enteric plexus

A

nervous network in esophagus, stomach, and intestines that regulates digestive tract motility, secretion, and blood flow

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39
Q

innervation of the enteric plexus

A
  • can function independently of CNS but it usually exerts influence on its action
  • often considered part of ANS
  • two networks of neurons
  • sensory neurons included
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40
Q

what are the two networks of neurons that make up the enteric plexus

A
  • submucosal plexus
  • myenteric plexus
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41
Q

submucosal plexus

A
  • found in submucosa
  • controls glandular secretions of mucosa and movements of muscularis mucosae
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42
Q

myenteric plexus

A
  • ganglia and nerve fibers between the two layers of the muscularis externa
  • controls peristalsis and other contractions of muscularis externa
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43
Q

what do the sensory neurons in the enteric plexus do?

A

monitor tension in gut wall and conditions in lumen

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44
Q

mesentery

A

connective tissue sheet that suspends stomach and intestines from abdominal wall

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45
Q

the looseness of the mesentery allows for what to occur?

A

the stomach and intestines to undergo strenuous contractions with freedom of movement in the abdominal cavity

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46
Q

what are the functions of the mesentery (3)

A
  • hold abdominal viscera in proper relationship to each other
  • prevent intestines from becoming twisted and tangled by changes in body position and by their own contractions
  • provide passage of blood/lymphatic vessels and nerves that supply the digestive tract
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47
Q

intraperitoneal

A

when an organ is enclosed by mesentery (serosa) on all sides

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48
Q

which organs are considered intraperitoneal?

A
  • stomach
  • liver
  • jejunum and ileum of small intestine
  • appendix, cecum, transverse, and sigmoid colon of large intestine
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49
Q

retroperitoneal

A
  • when an organ lias against the posterior body wall and is covered by peritoneum on its anterior side only
  • considered outside the peritoneal cavity
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50
Q

what organs are considered retroperitoneal?

A
  • duodenum
  • pancreas
  • ascending colon, descending colon, and rectum of large intestine
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51
Q

what controls the motility and secretion of the digestive tract? (3)

A

neural, hormonal, and paracrine mechanisms

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52
Q

neural controls of the digestive tract (2)

A
  • short (myenteric) reflexes
  • long (vagovagal) reflexes
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53
Q

short (myenteric) reflexes

A
  • stretch or chemical stim acts through myenteric plexus
  • stims peristatic contractions of swallowing
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54
Q

long (vagovagal) reflexes

A

parasympathetic stim of digestive motility and secretion

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55
Q

what are two hormones secreted in the blood that stimulate parts of the digestive tract?

A
  • gastrin
  • secretin
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56
Q

paracrine secretions stimulate

A

nearby target cells

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57
Q

the mouth is aka (2)

A
  • the oral cavity
  • buccal cavity
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58
Q

functions of the mouth (4)

A
  • ingestion
  • taste and other sensory responses to food
  • chewing and chemical digestion
  • swallowing, speech, and respiration
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59
Q

functions of the cheek and lips (3)

A
  • retain food and push it between the teeth
  • involved in speech
  • essential for sucking and blowing actions (suckling)
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60
Q

tongue

A

muscular, bulky, but agile and sensitive organ of the mouth

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61
Q

functions of the tongue

A
  • manipulate food between teeth
  • senses taste and texture of food
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62
Q

lingual papillae

A

bumps and projections that are the sites of most taste buds

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63
Q

body of the tongue

A
  • anterior two-thirds of tongue
  • occupies the oral cavity
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64
Q

root of the tongue

A
  • posterior one third of the tongue
  • occupies the oropharynx
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65
Q

vallate papillae

A

a v-shaped row of papillae that mark the boundary between the body and root of the tongue

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66
Q

intrinsic muscles of the tongue

A
  • entirely contained in tongue
  • produce subtle tongue movements of speech
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67
Q

extrinsic muscles of tongue

A
  • with attachments outside of tongue
  • produce stronger movements of food manipulation
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68
Q

lingual glands

A
  • serous and mucous glands within tongue amid the extrinsic muscles
  • secrete a portion of the saliva
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69
Q

lingual tonsils contained where?

A

in the root of the tongue

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70
Q

the palate functions (2)

A
  • separates oral cavity from nasal cavity
  • makes it possible to breathe while chewing food
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71
Q

hard palate

A

anterior portion that is supported by the palatine processes of the maxillae and the palatine bones

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72
Q

palatine rugae

A

transverse ridges that help the tongue hold and manipulate food

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73
Q

soft palate

A

posterior to hard palate with more spongy texture

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74
Q

uvula

A
  • conical medial projection visible at the rear of the mouth
  • helps retain food in the mouth until one is ready to swallow
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75
Q

how many adult teeth are there?

A

32

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76
Q

teeth are collectively called

A

the dentition

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77
Q

functions of the teeth (4)

A
  • function to break food into smaller pieces
  • makes food easier to swallow
  • exposes more surface area for action of digestive enzymes
  • speedy chemical digestion
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78
Q

mastication

A
  • breaks food into smaller pieces to be swallowed and exposes more surface to digestive enzymes
  • first step in mechanical digestion
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79
Q

how does mastication occur? (3)

A
  • food stims oral receptors that trigger an involuntary chewing reflex
  • tongue and other muscles in oral cavity manipulate food
  • masseter and temporalis elevate the lower teeth to crush food
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80
Q

functions of saliva (6)

A
  • moistens mouth
  • begins starch and fat digestion
  • cleanses teeth
  • inhibits bacterial growth
  • dissolves molecules so they can stim the taste buds
  • moistens food and binds it together into a soft mass to aid in swallowing
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81
Q

saliva is a _____ solution of _____ water

A
  • hypotonic
  • 97-99.5%
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82
Q

what is the pH of saliva?

A

6.8-7

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83
Q

what are the solutes found in saliva? (6)

A
  • mucus
  • electrolytes
  • lysozymes
  • IgA
  • salivary amylase
  • lingual lipase
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84
Q

mucus in saliva

A

binds and lubricates a mass of food and aids in swallowing

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85
Q

electrolytes of saliva

A

slats of Na+, K+, Cl-, phosphate, and bicarbonate

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86
Q

lysozymes of saliva

A

enzyme that kills bacteria

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87
Q

IgA of saliva

A

antimicrobial antibody

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88
Q

salivary amylase of saliva

A

enzyme that begins starch digestion in the mouth

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89
Q

lingual lipase of saliva

A

enzyme that begins fat digestion in the mouth (mainly after food is swallowed)

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90
Q

what are the two types of salivary glands

A
  • intrinsic (minor) salivary glands
  • extrinsic (major) salivary glands
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91
Q

intrinsic (minor) salivary glands

A
  • small glands dispersed amid other oral tissues
  • secrete saliva at constant rate whether eating or not
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92
Q

extrinsic (major) salivary glands

A

three pairs of larger, more discrete organs connected to oral cavity by ducts

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93
Q

what are the three major salivary glands?

A
  • parotid glands
  • submandibular glands
  • sublingual glands
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94
Q

parotid glands are located where?

A

beneath the skin anterior to the earlobe

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95
Q

submandibular glands are located where?

A

halfway along the body of the mandible

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96
Q

sublingual glands are located where?

A

in the floor of the mouth

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97
Q

the sublingual glands have several ducts that empty where?

A

posterior to the papilla of the submandibular duct

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98
Q

extrinsic salivary glands secrete about ___ of saliva a day

A

1-1.5 liters

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99
Q

______ respond to signals generated by presence of food

A

salivary nuclei in medulla oblongata and pons

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100
Q

salivary nuclei are excited by what?

A

tactile, pressure, and taste receptors

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101
Q

salivary nuclei receive input from higher brain centers. explain why.

A

odor, sight, or thought of food stims salivation

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102
Q

salivary glands send signals by way of what kind of fibers via what two nerves.

A
  • autonomic fiber
  • facial and glossopharyngeal nerves
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103
Q

parasympathetic fibers of the salivary nuclei

A

stim the glands to produce an abundance of thin, enzyme-rich saliva

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104
Q

sympathetic fibers of salivary nuclei

A

stims the glands to produce less, and thicker saliva with more mucus

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105
Q

pharynx

A
  • muscular funnel connecting oral cavity to esophagus and nasal cavity to larynx
  • where digestive and respiratory tracts intersect
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106
Q

what are the two layers of muscle within the pharynx

A
  • deep longitudinal skeletal muscle
  • superficial circular skeletal muscle
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107
Q

what is the function of the superficial circular muscle layer of the pharynx

A

forms the pharyngeal constrictors that force food downward during swallowing

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108
Q

how many pharyngeal constrictors are there and what are they called?

A
  • 3
  • superior, middle, inferior
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109
Q

when not swallowing what is the inferior constrictor doing? this constrictor is aka

A
  • contracted to exclude air from the esophagus
  • upper esophageal sphincter
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110
Q

esophagus

A

straight muscular tube 25-30 cm long between pharynx and stomach

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111
Q

the esophagus extends from

A

pharynx to cardiac orifice of stomach passing through esophageal hiatus in diaphragm

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112
Q

lower esophageal sphincter (LES)

A
  • inferior end of esophagus
  • prevents stomach contents from regurgitating into the esophagus and protects esophageal mucosa form erosive stomach acid
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113
Q

heartburn

A

burning sensation produced by acid reflux into the esophagus

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114
Q

deglutition

A
  • complex action involving over 22 muscles in the mouth, pharynx, and esophagus
  • swallowing
  • coordinated by swallowing center
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115
Q

swallowing center

A
  • pair of nuclei in medulla oblongata
  • communicates with muscles of the pharynx and esophagus
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116
Q

what are the three phases of swallowing

A
  • oral phase
  • pharyngeal phase
  • esophageal phase
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117
Q

oral phase of swallowing

A
  • voluntary control
  • tongue forms food bolus by pressing food into hard palate and the pushes it into laryngopharnyx
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118
Q

pharyngeal phase of swallowing

A
  • involuntary control
  • palate, tongue, vocal cords, and epiglottis block the oral and nasal cavities and airway while pharyngeal constrictors push the bolus into the esophagus
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119
Q

what is the role of the epiglottis in the oral phase of swallowing

A

it tips posteriorly to allow food to go into the laryngopharynx without traveling into the larynx

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120
Q

what is the purpose of the pharyngeal phase of swallowing

A

prevents food and drink from reentering mouth or entering the nasal cavity

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121
Q

esophageal phase of swallowing

A

peristalsis drives bolus downward and relaxation of the lower esophageal sphincter admits it into the stomach

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122
Q

peristalsis

A

circular muscle constricts above bolus, relaxes below bolus

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123
Q

when food and liquid is swallowed upright what happens

A

drops through esophagus by gravity faster than peristalsis can keep up with it

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124
Q

stomach

A

muscular sac in upper left abdominal cavity immediately inferior to diaphragm

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125
Q

functions of the stomach

A
  • food storage
  • mechanically breaks up food particles, liquefies the food, and begins chemical digestion of proteins and fat
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126
Q

chyme

A
  • the result of the stomach breaking down materials
  • acidic, soupy mixture of semi-digested food that passes on to the small intestine
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127
Q

what are the four regions of the stomach

A
  • cardiac part
  • fundic region (fundus)
  • body
  • pyloric part
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128
Q

cardiac part of stomach

A
  • small area within about 3 cm of the cardiac orifice
  • entry point of material from esophagus
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129
Q

fundic regions (fundus) of the stomach

A

dome superior to the esophageal attachment

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130
Q

body of the stomach

A

makes up greatest part of distal to cardiac orifice

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131
Q

pyloric part of stomach

A
  • narrower pouch at inferior end
  • subdivided into the antrum and the pyloric canal that terminates at the pylorus
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132
Q

pylorus

A

narrow passage to duodenum

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133
Q

pyloric sphincter

A
  • ring of smooth muscle around pylorus
  • regulates the passage of chyme into the duodenum
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134
Q

describe the mucosa of the stomach

A
  • covered with simple columnar epithelium
  • apical region are filler with mucin
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135
Q

how does mucin become mucus

A

swells with water

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136
Q

what do the mucosa and the submucosa look like when the stomach is full? empty?

A
  • flat when full
  • have longitudinal gastric rugae
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137
Q

the muscularis externa of the stomach has ___ layers. everywhere else has ___ layers.

A
  • three
  • two
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138
Q

what are the three layers of the muscularis externa in the stomach

A
  • outer longitudinal
  • middle circular
  • inner oblique
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139
Q

what cell types can be found in the stomach mucosa?

A
  • mucous cells
  • regenerative (stem) cells
  • parietal cells
  • chiefs cells
  • enteroendocrine cells
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140
Q

mucous cells in stomach

A

secrete mucus

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141
Q

regenerative (stem) cells of stomach

A

divide rapidly and produce continual supply of new cells to replace cells that die

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142
Q

parietal cells of stomach

A

secrete hydrochloric acid, intrinsic factor, and ghrelin

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143
Q

ghrelin

A

stimulates hunger feeling

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144
Q

chief cells of the stomach

A
  • most numerous cell type
  • secrete gastric lipase and pepsinogen
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145
Q

enteroendocrine cells of stomach

A

secrete hormones and paracrine messengers that regulate digestion

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146
Q

gastric pits of the gastric mucosa

A

depressions in gastric mucosa lined with the same columnar epithelium as the surface

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147
Q

gastric juice

A
  • 2-3L per day produced by the gastric glands
  • mainly a mixture of water, HCl and pepsin
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148
Q

functions of the HCl (3)

A
  • activates pepsin and lingual lipase
  • breaks up connective tissues and plant cell walls helping to liquify food and form chyme
  • contributes to innate immunity by destroying most ingested pathogens
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149
Q

pepsin

A
  • released by chief cells as the inactive form pepsinogen
  • digests dietary proteins into shorter peptides
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150
Q

how is pepsin activated

A

HCl removes some of the amino acids from pepsinogen to form pepsin

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151
Q

autocatalytic effect in pepsin

A

as some pepsin is formed it converts more pepsinogen into more pepsin

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152
Q

the digestion of proteins is incomplete in the stomach. where does it finish?

A

in the small intestine

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153
Q

gastric lipase

A
  • released from chief cells
  • plays a minor role with lingual lipase in the digestion of dietary fats
  • digests 10-15% of dietary fats in stomach
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154
Q

where is most all fat digested?

A

small intestine

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155
Q

intrinsic factor

A
  • glycoprotein secreted by parietal cells
  • essential to absorption of B12 by small intestine
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156
Q

how does intrinsic factor help in the absorption of B12?

A

binds B12 and then intestinal cells absorb this complex by receptor-mediated endocytosis

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157
Q

B12 is needed to synthesize

A

hemoglobin

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158
Q

pernicious anemia

A

anemia caused by a deficiency of B12

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159
Q

____ is the only indispensable function of the stomach

A

secretion of intrinsic factor

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160
Q

will digestion continue if the stomach is removed?

A

yes but B12 supplements will be needed

161
Q

most of the chemical messengers that are released by cells in the gastric and pyloric glands are…

A

hormones that enter blood and stim distant cells

162
Q

gut brain peptide

A
  • peptides produced in both the digestive tract and the CNS
  • most of the hormones that enter blood as chemical messengers
163
Q

what are the gut-brain peptides? (6)

A
  • substance P
  • vasoactive peptide (VIP)
  • secretin
  • gastric inhibitory peptide (GIP)
  • cholecystokinin (CCK)
  • neuropeptide Y (NPY)
164
Q

what is the mechanism of gastric motility (4)

A
  • food stims mechanoreceptors in pharynx and transmits signals in medulla during swallowing
  • swallowing center of medulla signals stomach to relax
  • vagus nerve relays message form medulla and activates receptive-relaxation response in stomach
  • soon rhythm of peristalsis starts in stomach
165
Q

what controls peristalsis in stomach

A

enteric pacemaker cells in longitudinal layer of muscularis externa

166
Q

describe peristalsis in the stomach

A
  • ring of constriction every 20 sec and becomes stronger contraction at pyloric part
  • eventually very strong after 30 min
167
Q

what is the function of peristalsis in the stomach

A

churn the food to mix it with gastric juice

168
Q

____ acts as a pump that breaks up semi-digested food and prepares it for the intestine

A

thick muscularis of antrum

169
Q

only about ___ of chyme is released into the duodenum at a time

170
Q

why is there such a small amount of chyme released into the duodenum

A
  • neutralize the stomach acid
  • digest nutrients little by little
171
Q

if duodenum is overfilled what happens?

A

gastric motility is inhibited

172
Q

a typical meal emptied form stomach in ___

173
Q

what can cause a meal to empty from the stomach quicker? slower?

A
  • less time if meal is more liquid
  • a high fat meal can take as long as 6 hours
174
Q

vomiting

A
  • forceful ejection of stomach and intestinal contents form the mouth
  • usually preceded by nausea and retching
175
Q

retching

A

thoracic expansion and abdominal contraction creating a pressure difference that dilates the esophagus and forced open the upper esophageal sphincter

176
Q

vomiting involves the ___ in the medulla

A

emetic center

177
Q

emetic center

A
  • in the medulla
  • integrates strong abdominal contractions combined with reverse peristalsis of gastric antrum and duodenum
178
Q

vomiting is indued by (4)

A
  • overstretching of stomach or duodenum
  • chemical irritants such as alcohol and bacterial toxins
  • visceral trauma
  • intense pain or psychological and sensory stim
179
Q

____ and ____ partially digest protein and lesser amounts of starch and fat in the stomach

A

salivary and gastric enzyme

180
Q

most digestion and nearly all absorption occurs where in the body?

A

small intestine

181
Q

while the stomach does not absorb significant amounts of nutrients what does it absorb?

A

aspirin and some lipid-soluble drugs

182
Q

alcohol is absorbed mainly by

A

small intestine

183
Q

what does the intoxicating feeling of alcohol consumption depend on?

A

how rapidly the stomach is emptied

184
Q

what three ways is the stomach protected from the acidic environment it creates

A
  • mucous coat
  • tight junctions
  • epithelial cell replacement
185
Q

mucous coat as a way to protect the stomach

A

thick highly alkaline mucus resists action of acid and enzymes

186
Q

tight junctions as a way to protect the stomach

A
  • between epithelial cells
  • prevent gastric juice from seeping between them and digesting deeper tissue
187
Q

epithelial cell replacement as a way to protect the stomach

A
  • cells live only 3-6 days
  • sloughed off in chyme and digested with food
  • replaced rapidly by cell division in gastric pits
188
Q

what happens if the protective measures of the stomach are broken down

A

inflammation and peptic ulcer

189
Q

gastritis

A

inflammation of the stomach and can lead to peptic ulcer

190
Q

peptic ulcer

A

pepsin and HCl eroding the stomach wall

191
Q

most ulcers are caused by

A

acid resistant bacteria helicobacter pylori

192
Q

ulcers causes by H pylori can be treated with

A

antibiotic and pepto

193
Q

risk factors for ulcer development

A
  • psychological factors
  • hypersecretion of acid
  • smoking
  • use of aspirin and other nonmedical anti-inflammatory drugs
194
Q

when there is a hypersecretion of acid in the stomach to cause ulcers ___ is sometimes involved

195
Q

gastric secretion and motility are regulated by

A

nervous and endocrine system

196
Q

gastric secretion and motility increase ____

A

when food is eaten

197
Q

what are the three phases of gastric activity

A
  • cephalic phase
  • gastric phase
  • intestinal phase
198
Q

cephalic phase of gastric activity

A
  • stomach being controlled by brain
  • vagus nerve stims gastric secretion even before food is swallowed (smell, thought, sight)
199
Q

gastric phase of gastric activity

A
  • stomach controlling itself
  • food stretches stomach and activates myenteric and vagovagal reflexes which stims gastric secretion
200
Q

intestinal phase of gastric activity

A
  • stomach being controlled by small intestine
  • intestinal gastrin briefly stims stomach but then secretin CCK, and enterogastric reflex inhibit gastric secretion/motility
201
Q

___ and ___ also stim acid and enzyme secretion in the gastric phase of gastric activity

A

histamine and gastrin

202
Q

___ suppresses gastric activity while ____ of the stomach is now inhibited

A
  • sympathetic nerve fibers
  • vagal (parasympathetic) stim
203
Q

what is the nervous system work of the cephalic phase?

A
  • sensory and mental inputs converge on hypothalamus
  • hypothalamus relays signals to medulla
  • vagus nerve fibers from medulla stim enteric nervous system to stomach stim gastric secretion
204
Q

40% of stomach acid secretion occurs in _____ of gastric activity

A

cephalic phase

205
Q

____ of gastric secretion and ___ of acid secretion occur in the gastric phase of gastric activity

A
  • two thirds
  • one third
206
Q

what are the enzymes released during the gastric phase of gastric activity?

A
  • pepsinogen
  • intrinsic factor
207
Q

what are the two ways ingested food stims gastric activity?

A
  • by stretching the stomach
  • by increasing the pH of the inside of the stomach
208
Q

gastric secretion is stim by three chemicals

A
  • acetylcholine
  • histamine
  • gastrin
209
Q

acetylcholine is released by what?

A

secreted by parasym nerve fibers of both reflexes

210
Q

histamine is released by what?

A

a paracrine secretion from enteroendocrine cells in the gastric glands

211
Q

gastrin is released by what?

A

a hormone produced by the enteroendocrine G cells in pyloric glands

212
Q

ACh, histamine, and gastrin stim what cells to release what?

A
  • parietal cells
  • secrete HCl and intrinsic factor
213
Q

gastrin and ACh stim what cells to release what?

A
  • chiefs cells
  • secrete pepsinogen
214
Q

what is the role of the duodenum in the intestinal phase of gastric activity

A
  • duodenum responds to arriving chyme and moderates gastric activity through hormones and nervous reflexes
  • initially enhances gastric secretion but soon inhibits it
215
Q

how does the duodenum inhibit gastric secretion? (3)

A
  • stretching of duodenum accentuates vagovagal reflex that stim stomach
  • peptides and amino acids in chyme stim G cells of duodenum to secrete intestinal gastrin
  • soon acids and fats trigger enterogastric reflex
216
Q

enterogastric reflex

A

duodenum sends inhibitory signals to stomach by way of enteric nervous system

217
Q

duodenum signals medulla to ___ and stim sympathetic neurons to ____

A
  • inhibit vagal nuclei
  • slow stomach activity
218
Q

what happens when duodenum inhibit vagal nuclei

A

reduces vagal stim of stomach

219
Q

what happens when duodenum stim sympathetic neurons

A

sends inhibitory signals to stomach

220
Q

chyme also stims duodenal enteroendocrine cells to release the hormones ___ and ____

A
  • secretin
  • cholecystokinin
221
Q

what do secretin and cholecystokinin do? (2)

A
  • stim the pancreas to release pancreatic fluid and gallbladder to release bile to suppress gastric secretion
  • decreases gastrin secretion and pyloric sphincter contracts tightly to limit chyme entrance to duodenum
222
Q

glucose-dependent insulinotropic peptide (GIP) (3)

A
  • aka gastrin inhibiting peptide
  • secreted by enteroendocrine cells
  • stimulates insulin secretion in preparation for processing nutrients about to be absorbed by small intestine
223
Q

liver

A
  • reddish-brown gland located immediately inferior to the diaphragm
  • largest gland weighing about 3 lbs
224
Q

what is the only function of the liver that contributes to the digestive system?

A

secretion of bile

225
Q

the gallbladder adhere to a depression on the ____ of the liver

A

inferior surface

226
Q

hepatocytes

A

cells in the lobules of the liver

227
Q

what do hepatocytes do after a meal?

A

absorb glucose, amino acids, iron, vitamin, and other nutrients from blood for metabolism or storage

228
Q

what do hepatocytes do between meals?

A

break down stored glycogen and release glucose into the blood

229
Q

hepatocytes remove and degrade what four things?

A
  • hormones
  • toxins
  • drugs
  • bile pigments
230
Q

hepatocyte secrete what into the blood? (5)

A

albumin, lipoproteins, clotting factors, angiotensinogen, and other products

231
Q

the liver receives a mixture of ___ blood and ___ blood

A
  • nutrient-laden venous blood
  • freshly oxygenated arterial blood
232
Q

where does nutrient-laden venous blood from for the liver?

A

the intestines

233
Q

where does freshly oxygenated blood come from for the liver?

A

celiac trunk

234
Q

after filtering through the liver, blood does what?

A

leaves the liver through the hepatic veins and drains into inferior vena cava

235
Q

bile canaliculi

A

narrow channels into which the liver secretes bile which then drains into the right and left hepatic ducts

236
Q

common hepatic duct

A

formed form convergence of right and left hepatic ducts on inferior side of liver

237
Q

cystic duct

A
  • joins the common hepatic duct
  • the cystic duct leads to the gallbladder
238
Q

bile duct

A
  • formed from the union of cystic and common hepatic ducts
  • descends toward the duodenum
239
Q

near duodenum the bile duct joins duct of pancreas where it forms the ____ (two words)

A

hepatopancreatic ampulla

240
Q

hepatopancreatic sphincter

A

regulates passage of bile and pancreatic juice into duodenum from ampulla

241
Q

between meals what happens to the hepatopancreatic sphincter do?

A

sphincter closes and prevents the release of bile into the intestines

242
Q

when does the hepatopancreatic sphincter open?

A

when cholecytokinin (CCK) is released by enteroendocrine cells from the duodenum during a meal

243
Q

gallbladder

A

pear-shaped sac on underside of liver that stores and concentrates bile by absorbing water and electrolytes

244
Q

bile

A

fluid secreted by the liver containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids

245
Q

pigments and color of bile

A
  • yellow-green color when secreted by liver
  • becomes intense green when concentrated in gallbladder
246
Q

bilirubin

A

primary bile pigments from hemoglobin decomposition

247
Q

bacteria in the intestine metabolize bilirubin into _____

A

urobilinogen

248
Q

about half of urobilinogen is converted to ____ and the other half is converted to ____

A
  • urobilin (yellow in color)
  • stercobilin
249
Q

what converts urobilinogen to urobilin? where does it go after this?

A
  • kidneys
  • excreted into urine
250
Q

where does urobilinogen get converted to stercobilin? what is it responsible for?

A
  • intestine
  • the brown color in feces
251
Q

bile enters the gallbladder by

A

filling the bile duct then overflowing into the gallbladder

252
Q

the liver secreted how much bile daily?

A

500-1000 mL

253
Q

what happens to 80% of bile acids?

A

reabsorbed in the ileum and retuned to the liver where hepatocytes absorb and resecrete them

254
Q

what happens to 20% of bile acids?

A

excreted in feces

255
Q

feces is the body’s only way for eliminating what?

A

excess cholesterol

256
Q

the liver synthesizes new bile acids from what?

A

cholesterol

257
Q

gallstones (3)

A
  • hard messes in either the gallbladder or bile duct
  • composed of cholesterol, calcium carbonate, and bilirubin
  • usually removed by laparoscopic surgery
258
Q

cholelithiasis

A
  • presence of gallstones
  • can occur when cholesterol becomes too concentrated, precipitates as crystals that grow in size
259
Q

cholelithiasis is most common in what people?

A

obese women over 40

260
Q

a painful obstruction of the bile ducts can result in what?

A
  • jaundice
  • poor fat digestion
  • impaired absorption of fat-soluble vitamins
261
Q

pancreas

A
  • flattened songy retroperitoneal gland posterior to greater curvature of stomach
  • measures 12-15 cm long, 2.5 cm thick
262
Q

the pancreas is both an ___ and ____ gland

A

endocrine and exocrine

263
Q

endocrine portion of the pancreas

A
  • pancreatic islets that secrete insulin and glucagon
  • concentrated in the tail of the gland
264
Q

exocrine portion of the pancreas

A

99% of pancreas that secretes 1200-1500 mL of pancreatic juice per day

265
Q

what two ducts are apart of the pancreatic duct system

A
  • pancreatic duct
  • accessory pancreatic duct
266
Q

pancreatic duct

A
  • runs lengthwise through middle of the gland
  • joins bile duct at the hepatopancreatic ampulla
267
Q

hepatopancreatic sphincter controls the release of both ___ into the duodenum

A

bile and pancreatic juice

268
Q

accessory pancreatic duct

A
  • smaller duct that branches from the main pancreatic duct
  • bypasses the sphincter and allows pancreatic juice to be released into duodenum even when bile is not
269
Q

pancreatic juice

A

alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other electrolytes

270
Q

____ secrete the enzymes and zymogens of pancreatic juice

271
Q

___ secrete the sodium bicarbonate of pancreatic juice

272
Q

what is the purpose of bicarbonate in pancreatic juice?

A

buffers HCl arriving from the stomach raising the pH to 7

273
Q

what are the pancreatic zymogens

A
  • trypsinogen
  • chymotrypsinogen
  • procarboxypeptidase
274
Q

trypsinogen

A
  • secreted into intestinal lumen to be converted to trypsin
  • autocatalytic
  • also converted to chymotrypsin and carboxypeptidase
275
Q

what converts trypsinogen and trypsin?

A

enteropeptidase

276
Q

enteropeptidase is secreted by

A

brush border of duodenum

277
Q

what makes trypsin autocatalytic

A

converts trypsinogen into still more trypsin

278
Q

what are the pancreatic enzymes (not the zymogens) (4)

A
  • pancreatic amylase
  • pancreatic lipase
  • ribonuclease
  • deoxyribonuclease
279
Q

pancreatic amylase

A

digests starch

280
Q

pancreatic lipase

A

digests fats

281
Q

ribonuclease and deoxyribonuclease

A

digests RNA and DNA

282
Q

when do the pancreatic enzymes become fully active

A

when exposed to bile or ions in intestinal lumen

283
Q

what are the three stimuli that are responsible for the release of pancreatic juice and bile

A
  • ACh (acetylcholine)
  • CCK (cholecystokinin)
  • secretin
284
Q

acetylcholine as stimuli responsible for the release of pancreatic juice and bile

A
  • stims acini to secrete enzymes during cephalic phase fo gastric control even before food is swallowed
  • enzymes remain in acini and ducts until chyme enters the duodenum
285
Q

where does acetylcholine come from to stim release of pancreatic juice and bile?

A

from the vagus and enteric nerves

286
Q

cholecystokinin as stimuli responsible for the release of pancreatic juice and bile

A
  • stim pancreatic acini to secrete enzymes
  • strongly stims gallbladder
  • induced contraction of gallbladder and relaxation of hepatopancreatic sphincter to discharge bile and pancreatic juice into duodenum
287
Q

where does cholecystokinin come from to stim release of pancreatic juice and bile?

A

secreted by mucosa of duodenum in response to arrival of fats in small intestine

288
Q

where does secretin come from to stim release of pancreatic juice and bile?

A

released from duodenum in response to acidic chyme arriving from the stomach

289
Q

secretin as stimuli responsible for the release of pancreatic juice and bile

A
  • stims ducts of both liver and pancreas to secrete more sodium bicarbonate
  • raises pH to the level required for activity of the pancreatic and intestinal digestive enzymes
290
Q

____ is the site of nearly all chemical digestion and nutrient absorption

A

small intestine

291
Q

what are the dimensions of the small intestine?

A

5 meters long 2.5 cm wide

292
Q

what is the blood flow out of the small intestine?

A
  • drained by mesenteric veins
  • converge to superior mesenteric vein
  • joins splenic vein
  • flows into hepatic portal system to the liver with its nutrients load
293
Q

what are the three regions of the small intestine

A
  • duodenum
  • jejunum
  • ileum
294
Q

duodenum of the small intestine (3)

A
  • first 25 cm (10 in)
  • begins at pyloric valve
  • most is retroperitoneal
295
Q

functions of the duodenum (5)

A
  • receives stomach contents, pancreatic juice, and bile
  • neutralizes stomach acid
  • emulsifiers fats
  • inactivates pepsin
  • pancreatic enzymes take over chemical digestion
296
Q

jejunum of the small intestine

A
  • first 40% of small intestine beyond duodenum
  • 1-7 meters
  • has large, tall, closely spaced circular folds
  • wall is relatively thick and muscular
  • rich in blood supply so red in color
297
Q

what is the function of the jejunum

A
  • most digestion and nutrient absorption occur here
  • final digestion and absorption of carbs, lipids, proteins, and nucleic acids
298
Q

ileum of the small intestine

A
  • forms last 60% of the post duodenal small intestine
  • about 1.6-2.7 meters
  • thinner, less muscular, less vascular, and paler pink in color than jejunum
299
Q

aggregated lymphoid nodules

A
  • prominent lymphatic nodules in clusters on the side opposite the mesenteric attachment
  • visible naked eye
  • become larger near large intestine
300
Q

ileocecal junction

A
  • end of the small intestine
  • where the ileum joins the cecum of the large intestine
301
Q

the tissues in the small intestine are similar to that of the ___ and ___

A

esophagus and stomach

302
Q

the lumen of the small intestine is made of what kind of tissue

A

simple columnar epithelium

303
Q

what are the two layers of the muscularis externa in the small intestine?

A
  • thick inner circular layer
  • thin outer longitudinal layer
304
Q

where are the jejunum and the ileum of the small intestine? what does that mean?

A
  • intraperitoneal
  • covered with serosa
305
Q

what are the three types of internal folds in the small intestine?

A
  • circular folds
  • villi
  • microvilli
306
Q

circular folds increase the surface area in the small intestine by a factor of

307
Q

villi increase the surface area of the small intestine by a factor of

308
Q

microvilli increase the surface area of the small intestine by a factor of

309
Q

circular folds of the small intestine

A
  • transverse to spiral ridges up to 1 cm high
  • largest folds of the intestinal wall
310
Q

the circular folds of the small intestine involve only the ____ and ____

A

mucosa and submucosa

311
Q

where can you find circular folds of the small intestine?

A

duodenum to middle of ileum

312
Q

why are there no circular folds in the distal portion of the ileum in the small intestine

A

because most nutrient reabsorption is complete by this point

313
Q

what is the function of the circular folds of the small intestine

A
  • cause chyme to flow in a spiral path causing contact with mucosa
  • promote more thorough mixing and nutrient absorption
314
Q

villi of the small intestine

A
  • projections 0.5-1 mm high with tongue-to-fingerlike shapes
  • make mucosa look fuzzy
  • covered with two types of epithelial cells
315
Q

what are the two types of epithelial cells that cover the villi small intestine?

A
  • absorptive cells (enterocytes)
  • goblet cells
316
Q

what is the purpose of the two types of epithelial cells that cover the villi of the small intestine

A

secrete mucus

317
Q

the epithelia of villi are joined by tight junctions to do what?

A

prevent digestive enzymes from seeping between them

318
Q

the core of the villus in the small intestine is filled with what?

A

areolar tissue of lamina propria

319
Q

what can be found in the areolar tissue of the lamina propria inside the villus of the small intestine?

A
  • arteriole
  • bloo capillaries
  • venule
  • lacteal
320
Q

lacteal of small intestine

A

lymphatic capillaries in the small intestine villi that absorb most lipids and fats

321
Q

____ absorbs most nutrients in the small intestine

A

blood capillaries in the villi

322
Q

microvilli of the small intestine

A
  • small plasma membrane extensions that form a fuzzy brush border on apical surface of each enterocyte
  • about 1 um high
323
Q

what is the function of microvilli in the small intestine

A

increase absorptive surface area and contain brush border enzymes

324
Q

brush border enzymes

A
  • contained in plasma membrane of microvilli
  • carry out some of the final stages of enzymatic digestion
  • not released into the lumen
325
Q

contact digestion

A

chyme must contact the brush border for digestion to occur

326
Q

____ ensures contact with the mucosa of the small intestine

A

intestinal churning of chyme

327
Q

duodenal glands

A
  • in submucosa of duodenum
  • secrete an abundance of bicarbonate rich mucus
328
Q

what is the function of the bicarbonate released by duodenal glands

A
  • neutralize stomach acid and shield the mucosa from its erosive effects
  • mucus contains signaling molecules that influence immune cells to tolerate food antigens and beneficial bacteria
329
Q

what is the function of the lymphocytes found throughout the lamina propria and submucosa of the small intestine?

A

intercept pathogens before they can invade bloodstream

330
Q

intestinal crypts

A
  • between bases of the villi
  • pores that open into tubular glands on the floor of the small intestine
  • can extend as far as the muscularis mucosae
331
Q

how much intestinal juice do intestinal crypts secrete per day?

A

1-2 liters

332
Q

what triggers intestinal crypts to release intestinal juice?

A
  • acid
  • hypertonic chyme
  • digestion of intestine
333
Q

what is the pH of intestinal juice secreted by intestinal crypts? what is in it?

A
  • 7.4-7.8
  • water, mucus, little enzymes
334
Q

most enzymes found in the small intestine are found where?

A

the brush border and pancreatic juice

335
Q

what are the three functions of the contractions of the small intestine?

A
  • mix chyme with intestinal juice, bile, and pancreatic juice
  • churn chyme and bring it in contact with the mucosa for contact digestion and nutrient absorption
  • to mose residue towards large intestine
336
Q

what is the function of mixing chyme with intestinal juices, bile, and pancreatic juice?

A
  • to neutralize acid
  • digest nutrients more effectively
337
Q

segmentation

A
  • movement in which stationary ring-like constrictions appear in several places along the intestine
  • most common intestinal contraction
  • kneads and churns the intestinal contents
338
Q

when do segmentation rings releax?

A

as new constrictions form elsewhere

339
Q

what controls the rhytm of segmentation in the small intestine?

A

enteric pacemaker cells in the muscularis externa

340
Q

describe the segmentation contractions in the duodenum and ileum

A
  • contracts about 12x per minute in the duodenum
  • 8-9x per min in the ileum
341
Q

what happens to the small intestine contractions when nutrients have been absorbed?

A

segmentation declines and peristalsis begins

342
Q

peristalsis

A
  • rhythmic contractions that moves remaining contents of small intestine toward colon
  • wave travels 10-70cm and dies out followed by another wave starting a little further down the tract
343
Q

migrating motor complex

A
  • successive overlapping waves of contraction
  • milk chyme towards colon over a period of 2 hours
344
Q

food in the stomach triggers ___ that enhances segmentation in the ileum and relaxes the ileal papilla

A

gastroileal reflex

345
Q

what happens to the ileal papilla when there is food in the stomach?

A

releases material from small intestine to large intestine

346
Q

what vitamins are fat soluble?

347
Q

if fat-soluble vitamins are ingested with fat-containing food what happens?

A

they are not absorbed at all and passed in the feces and wasted

348
Q

what are the water-soluble vitamins?

A
  • B complex
  • C
349
Q

how is vitamin C absorbed in the body

A

simple diffusion in the stomach

350
Q

how is B12 absorbed in the body?

A

intrinsic factor in the stomach

351
Q

where does mineral absorption occur?

A

all along the small intestine

352
Q

describe iron and calcium absorption in the small intestine.

A
  • absorbed as needed
  • most absorbed calcium is from meat and diary
  • dietary fat slows calcium absorption
353
Q

parathyroid hormone

A
  • secreted in response to a drop in blood calcium levels to increase calcium absorption in duodenum
  • stims kidney to synthesize vitamin D from precursors made by epidermis and liver
354
Q

the digestive tract receives about ____ water a day

A

nine liters

355
Q

water is absorbed by ___

356
Q

osmosis in the body

A

water follows the absorption of salts and organic nutrients

357
Q

diarrhea

A
  • occurs when large intestine absorbs too little water
  • feces passes through too quickly if intestine is irritated
  • contains high concentration of solute
358
Q

lactose intolerance

A
  • small intestine lack lactose to break down lactose
  • excess lactose in the feces with diarrhea
359
Q

describe the dimensions of the large intestines

A

1.5 meters long and 6.5 cm diameter

360
Q

appendix

A
  • attached to lower end of cecum in large intestine
  • densely populated with lymphocytes and is significant source of immune cells
361
Q

colon

A

portion of large intestine between ileocecal junction and rectum

362
Q

what are the four portions of the colon

A
  • ascending
  • descending
  • transverse
  • sigmoid
363
Q

what three portions of the colon frame the small intestine

A
  • ascending
  • desceinding
  • transverse
364
Q

sigmoid colon

A

S shaped portion leading down into pelvic cavity

365
Q

rectum

A
  • portion ending at anal canal
  • has three curves and three infoldings
366
Q

anal canal

A
  • final 3 cm of the large intestine
  • large hemorrhoidal veins
367
Q

hemorrhoidal veins

A
  • form superficial plexus in anal columns and around orifice
  • lack valves and are subject to distension
368
Q

hemorrhoids

A

permanently distended veins that protrude into anal canal or bulge outside the anus

369
Q

what differentiates the muscularis externa of the colon from other organs with the same layer of muscle?

A
  • taenia coli
  • haustra
  • in rectum and anal canal longitudinal muscle is continuous sheet with no haustra
370
Q

taenia coli

A

longitudinal fibers concentrated in three thickened ribbon like strips

371
Q

haustra

A

pouches in the colon caused by the muscle tone of the taenia coli

372
Q

what two sphincters regulate the anus

A
  • internal anal sphincter
  • external anal sphincter
373
Q

internal anal sphincter

A

smooth muscle of muscularis externa

374
Q

external anal sphincter

A

skeletal muscle of pelvic diaphragm

375
Q

large intestine mucosa (5)

A
  • simple columnar epithelium in all regions except lower half of anal canal
  • no circular folds or villi
  • intestinal crypts are deeper than in small intestine
  • greater amount of goblet cells
  • lots of lymphoid tissue in lamina propria and submucosa
376
Q

what is the purpose of there being an abundance of lymphoid tissue in the large intestine

A

provides protection from large population of bacteria in large intestine

377
Q

gut microbiome

A
  • microbiota
  • more than 1000 species of bacteria, yeasts, viruses and other microbes that populate the large intestine
378
Q

what do bacteria in the gut microbiome do?

A
  • digests cellulose, pectin, and other carbohydrates for which our cells lack enzymes
  • help in the synthesis of vitamins K and B
379
Q

flatus

A

intestinal gas that is expelled

380
Q

an average person produces ____ per day

381
Q

what is in flatus

A
  • hydrogen sulfide
  • indole
  • skatol
382
Q

____ produces odor in flatus

383
Q

the large intestine takes how many hours to reduce food residue to feces

A

36-48 hours

384
Q

how does the large intestine change food residue to feces

A

does not chemically change the residue but reabsorbs water and electrolytes

385
Q

food residue spends the most amount of time in which part of the colon?

A

transverse colon

386
Q

feces is how much water and how much solid?

A

75% water and 25% solid

387
Q

what is in the solids of feces? (percentages too) (4)

A
  • 30% bacteria
  • 30% undigested fiber
  • 10-12% fat
  • small amounts of mucus, proteins, salts, digestive secretions, and sloughed epithelial cells
388
Q

colonic motility includes what two things?

A
  • haustral contractions
  • mass movements
389
Q

haustral contractions of colonic movement

A
  • occur every 30 min
  • distension of a haustrum stims it to contract
390
Q

what is the purpose of haustral contractions of colonic motility

A

churns and mixes residue promoting water and salt absorption

391
Q

mass movement of colonic movement

A
  • stronger contractions that occur one to three times a day
  • triggered by gastrocolic and duodenal reflexes
  • filling of the stomach and duodenum stims motility of the colon
392
Q

what is the purpose of mass movement of colonic motility

A

move residue several cm

393
Q

the stretching of the rectum stims what two defecation reflexes?

A
  • intrinsic defecation reflex
  • parasympathetic defecation reflex
394
Q

how does the intrinsic defecation reflex work

A

stretching signals travel through plexus to the muscularis causing it to contract and the internal sphincter to relax

395
Q

parasympathetic defecation reflex involves the

A

the spinal cord

396
Q

the intrinsic defecation reflex works with what to produce its response?

A

works entirely within myenteric plexus to produce relatively weak response

397
Q

how does the parasympathetic reflex work?

A
  • stretching of rectum sends sensory signals to spinal cord
  • pelvic nerves return signals intensifying peristalsis and relaxing the internal anal sphincter
398
Q

defecation occurs only if ___ and ___ are voluntarily relaxed

A
  • external anal sphincter
  • puborectalis muscles
399
Q

Valsalva maneuver

A

abdominal contractions increase abdominal pressure and compress rectum to assist in defecation

A&P 2 (9 decks)

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