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HLSC 128 - Human Physiology II > Chapter 16 - Digestive System > Flashcards

Chapter 16 - Digestive System Flashcards

1
Q

What is the primary function of the digestive system?

A

transfer nutrients, water, and electrolytes from ingested food into the body’s internal environment

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2
Q

How long is the digestive tract?

A

4.5m

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3
Q

What is food broken down into?

A

molecular forms

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4
Q

What are the 4 functions of the digestive system?

A

motility, secretion, digestion, absorption

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5
Q

Motility

A

the muscular contractions that mix and move forward the contents

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6
Q

What kind of muscle makes up the digestive tract?

A

smooth muscle

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7
Q

Tone

A

-the constant low level of contraction maintained by smooth muscles

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8
Q

What is tone used for?

A

-maintains a steady pressure
-prevents permanent stretching

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9
Q

Propulsive Movements

A

-a type of motility
-used to push contents forward through the tract

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10
Q

Mixing Movements

A

-a type of motility
-two functions: 1) mixing food with juices 2) absorption

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11
Q

Where is skeletal muscle used in digestion?

A

-mouth and anus
-chewing, swallowing, defecation are voluntary

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12
Q

What secretes digestive juices?

A

exocrine glands

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13
Q

What makes up digestive secretions

A

water, electrolytes, specific organic constituents (enzymes, bile salts, mucus)

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14
Q

What monitors the release of secretions?

A

neural or hormonal stimulation

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15
Q

When are digestive secretions normally reabsorbed?

A

after their participation in digestion

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16
Q

Digestion

A

the biochemical breakdown of structurally complex food into smaller, absorbable units

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17
Q

What accomplishes digestion?

A

enzymes

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18
Q

What is the absorbable unit of carbohydrates?

A

Monosaccharides (ie. glucose and fructose)

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19
Q

What must be done to disaccharides and polysaccharides before they can be absorbed?

A

they must be broken down into monosaccharides

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20
Q

What are some polysaccharide examples?

A

starch, glycogen, cellulose

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21
Q

What are some disaccharide examples?

A

sucrose, maltose, and lactose

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22
Q

What are some monosaccharide examples?

A

glucose, fructose, galactose

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23
Q

Disaccharide

A

2 monosaccharides linked together

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24
Q

Polysaccharide

A

multiple monosaccharides (glucose) linked together

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25
Q

What is the organic composition of single sugars?

A

C₆H₁₂O₆

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26
Q

Sucrose = Glucose + __________

A

fructose

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27
Q

Lactose = Glucose + _________

A

galactose

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28
Q

Maltose = Glucose + _________

A

glucose

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29
Q

What are proteins broken down into?

A

peptide fragments

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30
Q

What are peptide fragments further digested into?

A

amino acids

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31
Q

Where do amino acids go?

A

epithelial cells

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32
Q

Can short amino acid chains be absorbed?

A

yes

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33
Q

What form are dietary fats in?

A

triglycerides

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34
Q

What does fat digestion produce?

A

2 free fatty acids and monoglyceride

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35
Q

Hydrolysis

A

how the enzymes break bonds to digest contents into smaller molecules

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36
Q

Where does most absorption occur?

A

the small intestine

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37
Q

Absorption

A

of small units resulting from digestion, vitamins, electrolytes, and water into blood or lymph

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38
Q

Digestive Tract Organs

A

-mouth
-pharynx
-esophagus
-stomach
-sm. intestine (duodenum, jejunum, ileum)
-lg. intestine (cecum, appendix, colon, rectum)
-anus

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39
Q

Accessory Digestive Organs

A

-salivary glands
-pancreas (exocrine)
-liver
-gall bladder

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40
Q

What are the functions of the mouth and pharynx?

A

-chewing
-swallowing

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41
Q

What are the functions of salivary glands?

A

-moisten and dissolve food
-lubrication
-polysaccharide digesting enzyme (amylase)

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42
Q

What do the salivary glands secrete?

A

-salt
-water
-mucus
-amylase

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43
Q

What does the stomach do?

A

-store, mix, dissolve
-continue digestion
-regulate emptying into sm. intestine

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44
Q

What does the stomach secrete?

A

-HCl (kill microbes, pepsinogen to pepsin)
-Pepsin (protein digesting enzyme)
-Mucus (lubrication and protection)

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45
Q

What does the pancreas do?

A

-secrete enzyme and bicarbonate

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46
Q

What does the pancreas secrete?

A

-enzymes (digestion)
-bicarbonate (neutralize HCl entering sm. intestine)

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47
Q

What does the liver do?

A

-secrete bile

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48
Q

What does the liver secrete?

A

-bile salts (solubilize fats)
-bicarbonate (neutralize HCl)

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49
Q

What does the gallbladder do?

A

store and concentrate bile between meals

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50
Q

What does the small intestine do?

A

-digestion and absorption of most substances
-mixing and propulsion

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51
Q

What does the small intestine secrete?

A

-enzymes (digestion)
-salt and water (fluid balance)
-mucus (lubrication)

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52
Q

What does the large intestine do?

A

-storage
-absorption of salt and water
-mixing and propulsion
-defecation

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53
Q

What does the large intestine secrete?

A

mucus for lubrication

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54
Q

What are the 4 major tissue layers of the digestive tract?

A

from inward to outward: mucosa, submucosa, muscularis externa, serosa

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55
Q

Mucosa

A

-lines luminal surface
-divided into 3 layers: mucous membrane, lamina propria, muscularis mucosa

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56
Q

What do the folds of the mucosa do?

A

increase absorptive surface area

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57
Q

Mucous Membrane

A

-most inward
-exposed to lumen
-serves as a protective surface
-secretion and absorption in certain areas

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58
Q

Mucous Membrane: Exocrine Gland Cells

A

secrete digestive juices

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59
Q

Mucous Membrane: Endocrine Gland Cells

A

secrete blood-borne GI hormones

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60
Q

Mucous Membrane: Epithelial Cells

A

-specialized
-absorb digestive nutrients

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61
Q

Lamina Propria

A

-thin middle layer
-house GALT

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62
Q

Gut-Associated Lymphoid Tissue (GALT)

A

defence against pathogenic bacteria

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63
Q

Muscularis Mucosa

A

-outermost mucosal layer
-sparse layer of smooth muscle

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64
Q

Submucosa

A

-second layer inward
-thick connective tissue layer

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65
Q

What is the function of the submucosa?

A

provides distensibility and elasticity

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66
Q

What does the submucosa have?

A

-larger blood and lymph vessels
-submucosal plexus

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67
Q

Submucosal Plexus

A

nerve network in the submucosa

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68
Q

Muscularis Externa

A

-third layer inward
-the major smooth muscle coat
-2 layers: circular and longitudinal
-myenteric plexus

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69
Q

Muscularis Externa: Circular Layer

A

-inner muscular layer
-controls diameter of lumen

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70
Q

Muscularis Externa: Longitudinal Layer

A

-outer layer
-controls length of the tube

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71
Q

What is the function of the muscularis externa?

A

propulsion and mixing

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72
Q

Interstitial Cells of Cajal

A

-cells between the two muscularis externa layers
-the origin of BER

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73
Q

Basic Electrical Rhythm (BER)

A

-rhythmic electrical activity
-pacemaker cells
-control slow wave cycle activity
-not action potentials, controlled by calcium

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74
Q

Myenteric Plexus

A

-lies btween the two muscularis externa layers
-extensive network of nerve cells

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75
Q

What regulates local gut activity?

A

-submucosal and myenteric plexuses
-hormones
-local chemical mediators

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76
Q

Serosa

A

-outer of the 4 layers
-connective tissue covering

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77
Q

What does the serosa secrete?

A

serous fluid to lubricate and prevent friction with surrounding organs

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78
Q

What is the serosa continuous with? Why?

A

-the mesentery
-suspends GI organs like a sling
-provides fixation and support

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79
Q

What regulates motility and secretion?

A

-autonomic smooth muscle
-BER
-intrinsic nerves plexuses
-extrinsic nerves plexuses
-GI hormones

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80
Q

What are the two intrinsic nerve plexuses?

A

ENS (myentric and submucosal)

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81
Q

Enteric Nervous System

A

-the GI tracts own NS
-mostly self-regulated but receives some ANS input

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82
Q

The ENS has ________ and ________ functions

A

sensory and motor

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83
Q

Extrinsic Nerve

A

-from both ANS branches
-originate outside GI tract

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84
Q

Sympathetic NS

A

-inhibit GI contraction and secretion
-digestion not a priority in an emergency

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85
Q

Parasympathetic NS

A

-dominates when regular activity needed

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86
Q

Gastrointestinal Hormones

A

-carried through blood and exhibit functions
-ie. Gastrin stimulates gastric juice release in stomach

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87
Q

Lips

A

-opening to the digestive tract
-procure, guide, maintain food in mouth
-speech
-tactile sensation

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88
Q

Palate

A

arched roof of the oral cavity

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89
Q

Uvula

A

seals off nasal passages during swallowing

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90
Q

Tongue

A

-floor of oral cavity
-chewing
-swallowing
-speech
-taste

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91
Q

What type of muscle is the tongue made of?

A

skeletal

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92
Q

Pharynx

A

-the cavity at the back of the throat
-passageway for air and food

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93
Q

Tonsils

A

-side walls of pharynx
-lymphoid tissue for immune support

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94
Q

Teeth

A

-functions of chewing
-mechanical digestion
-increases surface area for enzymes to act on
-mix food and saliva and stimulate taste buds

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95
Q

What are the 3 pairs of salivary glands?

A

-parotid
-sublingual
-submandibular

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96
Q

How is saliva secretion accomplished?

A

by a large increase in blood flow

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97
Q

Which exocrine has the largest secretion per gram?

A

salivary glands

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98
Q

What is the composition of saliva?

A

99.5% water and 0.5% electrolytes and proteins (amylase, mucus, lysozyme)

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99
Q

Salivary Amylase

A

-begins the digestion of carbohydrates
-breaks polysaccharides into maltose

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100
Q

Antibacterial Action of Saliva

A

-lysozyme breaks down the cell walls of certain bacteria
-rinse away food that could feed bacteria

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101
Q

Lubrication at Oral Cavity

A

-saliva moistens food

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102
Q

How does saliva act as a solvent?

A

-taste buds need moisture to work

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103
Q

Bicarbonate in Saliva

A

-neutralizes acids to prevent cavities and tooth decay

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104
Q

Do sympathetic or parasympathetic NS control saliva release?

A

both

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105
Q

Where is amylase broken down?

A

stomach

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106
Q

Is digestion at the oral cavity essential?

A

no, most of it is done later on

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107
Q

Parasympathetic Salivary Secretion

A

-low-level
-keeps throat and mouth always moist

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108
Q

Simple Salivary Reflex

A

-controlled by chemoreceptors and pressure receptors responding to presence of food

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109
Q

Salivary centre

A

-located in the medulla
-controls digestive activities

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110
Q

Conditioned Salivary Reflex

A

-occurs without oral stimulation
-thinking about, seeing, smelling, hearing food can activate

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111
Q

Is parasympathetic and sympathetic activity at salivary glands antagonistic?

A

no

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112
Q

What motility is associated with the pharynx and esophagus?

A

swallowing

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113
Q

Swallowing is an ______ or _____ reflex.

A

all or none

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114
Q

When is swallowing initiated?

A

when bolus is forced by tongue into pharynx

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115
Q

What is the most complicated reflex in the body?

A

swallowing

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116
Q

Can swallowing be stopped once begun?

A

no

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117
Q

Is swallowing voluntary?

A

yes

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118
Q

Where is the swallowing centre located?

A

medulla

119
Q

Epiglottis

A

-small cartilage flap
-protects airways from food

120
Q

Esophagus

A

-straight muscular tube between pharynx and stomach

121
Q

The esophagus has ________ at each end.

A

sphincters

122
Q

Pharyngoesophageal Sphincter

A

-upper esophageal sphincter
-prevents large volumes of air from entering digestive tract during breathing

123
Q

Gastroesophageal Sphincter

A

-lower esophageal sphincter
-prevents reflux of gastric contents

124
Q

Peristaltic Waves

A

push food through the esophagus

125
Q

Esophageal secretions are entirely _________

A

protective (mucus lubricates)

126
Q

What are the 3 sections of the stomach?

A
  1. fundus
  2. body
  3. antrum
127
Q

Fundus

A

-lies above esophageal opening
-thin smooth muscle

128
Q

Body (Stomach)

A

-the middle/main part
-thin smooth muscle

129
Q

Antrum

A

-lower part
-heavier smooth muscle

130
Q

Pyloric Sphincter

A

-barrier between stomach and duodenum (sm. intestine)

131
Q

Where are the mucosa located in the stomach?

A
  1. Oxyntic (in the body and fundus)
  2. Pyloric Gland Area (in the antrum)
132
Q

What are the 3 main stomach functions?

A
  1. Store ingested food
  2. Secrete HCl and enzymes for protein digestion
  3. Mixing to convert food to chyme
133
Q

What are the 4 aspects of gastric motility?

A
  1. filling
  2. storage
  3. mixing
  4. emptying
134
Q

Gastric Filling

A

-stomach has a 50mL capacity at empty but can hold up to 1L

135
Q

Receptive Relaxation

A

-an aspect of filling
-how the stomach accommodates volume change
-stomach folds relax and get smaller as it fills
-without increasing pressure

136
Q

Where does gastric storage take place?

A

the body of the stomach

137
Q

What moves contents into the storage area?

A

-peristalsis
-BER

138
Q

Where does gastric mixing take place?

A

antrum of the stomach

139
Q

How is food mixed? What does it turn into?

A

food is mixed by strong peristaltic waves and is turned into chyme

140
Q

Factors that influence gastric emptying: Stomach

A

-amount of chyme
-Gastrin
-fluidity of the chyme

141
Q

Factors that influence gastric emptying: Duodenum

A

-*primary controls
-duodenum must be ready
-presence of fat, acid, hypertonicity, distention

142
Q

How does ACID affect emptying in duodenum?

A

-acid in duodenum inhibits further emptying of acidic contents

143
Q

How does HYPERTONICITY affect emptying in duodenum?

A

-emptying is inhibited when osmolarity starts to rise

144
Q

How does DISTENSION affect emptying in duodenum?

A

-too much chyme inhibits emptying

145
Q

How does FAT affect emptying in duodenum?

A

-fat digestion and absorption only occur in sm. intestine
-when fat is already present, emptying is inhibited

146
Q

Emptying: Neural Response (Enterogastric Reflex)

A

-mediated by intrinsic nerve plexuses (short) and autonomic nerves (long)

147
Q

Emptying: Hormonal Response (Enterogastrones)

A

-released from duodenal mucosa
-secretin and cholecystokinin

148
Q

Effect of emotions and pain on emptying:

A

-decrease motility - sadness, fear, pain (SNS)
-increase motility - anger, aggressioon

149
Q

What are the 3 types of secretory cells in oxyntic mucosa?

A
  1. Parietal (oxyntic) Cells
  2. Chief Cells
  3. Mucous Cells
150
Q

Parietal (Oxyntic) Cells

A

-secrete HCl and intrinsic factor

151
Q

Intrinsic Factor

A

used for vitamin B₁₂ absorption

152
Q

Chief Cells

A

secrete pepsinogen, an enzyme precursor

153
Q

Mucous Cells

A

-line gastric pits and gland entrances
-secrete watery mucus for lubrication and HCl and pepsin protection

154
Q

HCl Functions

A

-activates pepsinogen into pepsin
-provides acid medium for optimal pepsin activity
-breakdown of connective tissue and muscle fibres
-denatures proteins
-kills microorganisms

155
Q

Gastric Pits

A

invaginations in the stomach wall

156
Q

Gastric Glands

A

lie at the base of gastric pits

157
Q

The entire stomach mucosa is replaced every ___ days by means of _________ cells.

A

3 days; stem cells

158
Q

Surface Epithelial Cells

A

-cover gastric mucosa
-secrete thick alkaline mucus
-forms visible layer for protection

159
Q

Pepsinogen (inactive)

A

the major digestive constituent of gastric secretion

160
Q

Pepsin (active)

A

splits certain amino acid chains into smaller chains

161
Q

Where is pepsinogen stored and how is it activated?

A

-stored in secretory vesicles called zymogen granules
-HCl activates pepsinogen

162
Q

Autocatalytic (“self-activating”) Process of Pepsin

A

-process by which pepsin activates other pepsinogen molecules to create more pepsin

163
Q

Why is pepsin stored in its inactive form?

A

so it doesn’t digest the proteins of the cells that create it

164
Q

What secretes ‘gastrin’ into the blood?

A

-endocrine ‘G cells’ found in gastric PGA pits

165
Q

What secretes ‘histamine’ into the blood?

A

-Enterochromaffin-like (ECL) cells
-dispersed among parietal and chief cells

166
Q

What secretes ‘somatostatin’?

A

-D cells
-in glands near pylorus and duodenum

167
Q

What 4 substances control secretion of gastric juices?

A

-gastrin
-histamine
-ACh
-somatostatin

168
Q

What does ACh do?

A

-stimulates parietal, chief, G cells, and ECL cells to secrete

169
Q

What does Gastrin do?

A

-stimulates parietal and chief cells
-stimulates ECL cells to release histamine to bring about HCl

170
Q

What does histamine do?

A

-acts locally to speed up HCl secretion

171
Q

What does somatostatin do?

A

-acts as a paracrine gland locally
-negative feedback fashion on G cells and ECL cells to inhibit HCl secretion

172
Q

What does the pyloric gland area (PGA) secrete?

A

gastrin and somatostatin

173
Q

What are the 3 phases of gastric secretion?

A
  1. cephalic
  2. gastric
  3. intestinal
174
Q

Cephalic Phase

A

-acts in the head before food reaches the stomach

175
Q

What happens during cephalic phase?

A

-increased HCl and pepsinogen secretion
-a) thinking about food increases ACh action on these cells
-b) stimulation of G cells enhances HCl and pepsinogen secretion

176
Q

Gastric Phase

A

-begins when food reaches stomach (ie. proteins)

177
Q

What happens during gastric phase?

A

-proteins stimulate nerve pathways and gastrin release

178
Q

Intestinal Phase

A

-the inhibitory phase

179
Q

What happens during the intestinal phase?

A

when chyme begins to empty the flow of gastric juices is shut off

180
Q

Which nerve controls all these actions?

A

vagus

181
Q

What 3 things reduce gastric secretion?

A
  1. as the food empties into duodenum
  2. fall in pH triggers somatostatin release
  3. enterogastric reflex and enterogastrones suppress secretory cells
182
Q

Tight Junctions

A

line mucosa to prevent leaking acid

183
Q

Gastric Mucosal Barrier

A

-lubricant, prevention of mechanical injury, protects from self digestion

184
Q

Peptic Ulcers

A

-when barrier is broken and gastric wall is injured by acid

185
Q

Where does alcohol and aspirin absorption occur?

A

-stomach

186
Q

Where does 95% of absorption occur?

A

small intestine

187
Q

Pancreas

A

-below stomach and above duodenum
-has endocrine and exocrine functions

188
Q

Islets of Langerhans

A

secrete insulin and glucagon in pancreas

189
Q

Acini

A

-secretory cells in the pancreas
-connect to ducts and eventually empty into duodenum

190
Q

Exocrine Pancreas

A

-secretes pancreatic juice that consists of 1) pancreatic enzymes secreted by acinar cells 2) aqueous alkaline solution secreted by duct cells

191
Q

Where are pancreatic enzymes stored?

A

zymogen granules (inactive precursors)

192
Q

What is the alkaline solution rich in?

A

sodium bicarbonate NaHCO3

193
Q

What do proteolytic enzymes do?

A

digest proteins

194
Q

What are the 3 proteolytic enzymes?

A

trypsin, chymotrypsin, carboxypeptidase

195
Q

Trypsinogen is converted to ______

A

trypsin

196
Q

Chymotrypsinogen is converted to ______

A

chymotrypsin

197
Q

Procarboxypeptidase is converted to _______

A

carboxypeptidase

198
Q

What 3 pancreatic enzymes are secreted by acinar cells?

A
  1. Proteolytic enzymes
  2. Pancreatic amylase
  3. Pancreatic lipase
199
Q

Pancreatic Amylase

A

-converts polysaccharides into maltose (disaccharide)

200
Q

Pancreatic Lipase

A

-only enzyme that can digest fat

201
Q

What activated trypsinogen?

A

enterokinase in duodenum

202
Q

Secretin acts on the ____ cells of the pancreas.

A

duct

203
Q

CCK acts on the ______ cells of the pancreas.

A

acinar

204
Q

What is the purpose of the alkaline fluid secreted?

A

-duodenum can be damaged by acid
-pancreatic enzymes don’t work in acidic conditions

205
Q

Action of Secretin

A

-release is stimulated by acid in duodenum
-secretin carried by blood to pancreas
-stimulates duct cells to make alkaline fluid
-acid in duodenum is neutralized

206
Q

Action of CCK

A

-presence of fat and protein in duodenum stimulate CCK release
-CCK carried by blood to pancreas
-acts of acinar cells to increase digestive enzyme secretion
-fat and proteins are digested

207
Q

How are digestive enzymes released?

A

all of them are grouped together in zymogen granules and release together

208
Q

What is the largest and most important metabolic organ in the body?

A

liver

209
Q

Where are bile salts secreted from?

A

the liver via gallbladder and ducts

210
Q

What are bile salts used for?

A

fat digestion and absorption

211
Q

Where is bile stored?

A

gallbladder

212
Q

What makes up bile?

A

-bile salts
-cholesterol
-lecithin
-bilirubin (yellow)

213
Q

When does bile enter the duodenum?

A

after a meal

214
Q

What does the hepatic portal vein carry? What does it connect?

A

-carries newly absorbed nutrients to liver for processing
-from sm. intestine to liver

215
Q

What is bile salt?

A

-derivatives of cholesterol

216
Q

What does bile salt do?

A

convert large fat globules into a liquid emulsion

217
Q

What happens to bile salts after participating in fat digestion and absorption?

A

it is reabsorbed into the blood

218
Q

Where are bile salts reabsorbed?

A

terminal ileum

219
Q

Secreted bile salts are ____% recycled, ___% new.

A

95; 5

220
Q

What % of bile salts are lost in feces?

A

5%

221
Q

How do bile salts help lipase?

A

increase surface area for the enzyme to act on

222
Q

Enterohepatic Circulation

A

mechanism that recycles bile salts

223
Q

Micelle

A

-water soluble structures critical component for fat absorption

224
Q

What do micelles do?

A

-transport digested free fatty acids, monoglycerides, fat soluble vitamins, cholesterol in their hydrophobic centre

225
Q

Structure of a Micelle

A

-hydrophilic shell (water loving)
-hydrophobic centre (water fearing)

226
Q

Bilirubin

A

-no role in digestion
-waste product excreted in bile
-pigment derived from breakdown of RBCs

227
Q

How is bile concentration controlled?

A

-salt actively transported out of gallbladder and water osmotically follows

228
Q

After luminal contents pass beyond the sm. intestine, _____ and _____ no longer occur

A

digestion and absorption (except salt and water)

229
Q

What are the motility components of the sm. intestine?

A

-segmentation
-migrating motility complex

230
Q

Segmentation

A

-the sm. intestines primary method of motility
-ring-like contractions

231
Q

What does segmentation do?

A

-mix chyme
-expose chyme to absorptive surfaces in mucosa
-move chyme along lumen

232
Q

What initiates segmentation?

A

-pacemaker cells that produce BER

233
Q

Is segmentation frequency constant?

A

no, it is slower in the ileum

234
Q

When do segmentation contractions cease?

A

when most of the meal has been absorbed

235
Q

What replaces segmentation?

A

migrating motility complex (MMC)

236
Q

When does the MMC act?

A

between meals

237
Q

What does the MMC do?

A

-uses peristaltic waves to sweep from the stomach to the intestine
-get rid of meal debris and bacteria and push towards colon

238
Q

Which hormone regulates MMC?

A

motilin, secreted by intestinal mucosa

239
Q

Ileocecal Valve

A

-keeps ileal contents moving forward

240
Q

The ileocecal juncture function

A

barrier between the sm. and lg. intestines

241
Q

Ileocecal Sphincter

A

-remains mostly constricted
-mediated by intrinsic plexus and gastrin secretion

242
Q

Does the juice secreted by sm. intestine contain digestive enzymes?

A

no

243
Q

Succus Entericus

A

-aqueous salt and mucous solution secreted by sm. intestine
-lubricates and protects
-provides water to help with digestion (hydrolysis)

244
Q

Where do synthesized enzymes in sm. intestine act?

A

within brush-border membrane of epithelial cells

245
Q

What forms the brush border?

A

microvilli that line the intestinal lumen

246
Q

What are the 3 brush border enzymes?

A
  1. enterokinase
  2. disaccharidases
  3. aminopeptidases
247
Q

Enterokinase

A

activates trypsinogen to trypsin

248
Q

Disaccharidases

A

-maltase, sucrase, or lactase convert disaccharides to monosaccharides

249
Q

Aminopeptidases

A

convert peptides to amino acids

250
Q

What continues carb and protein digestion in the sm. intestine?

A

pancreatic enzymes

251
Q

What completes carb and protein digestion in sm. intestine?

A

brush border enzymes

252
Q

Where and by what is fat ENTIRELY digested by?

A

-within small intestine by pancreatic lipase

253
Q

What 2 enzymes digest carbohydrates?

A

-amylase (1st by salivary glands and in stomach: poly to di)
-disaccharidases (2nd by pancreas and sm. intestine: di to mono)

254
Q

What are the absorbable nutrients of carbohydrates?

A

monosaccharides (esp. glucose)

255
Q

What 3 enzymes digest proteins?

A

-pepsin (stomach antrum: peptide fragments)
-Trypsin, chymotrypsin, carboxypeptidase (pancreas: attack different fragments)
-Aminopeptidases (sm. intestine: peptide fragments to amino acids)

256
Q

What are the absorbable nutrients of proteins?

A

amino acids (+ some small peptides)

257
Q

What are the 2 enzymes for digesting fat?

A

-bile salts - *not an enzyme (liver: emulsification for attack by lipase)
-lipase (pancreas: triglycerides to fatty acids & monoglycerides)

258
Q

What are the absorbable nutrients of fat?

A

fatty acids and monoglycerides

259
Q

What does the small intestine absorb?

A

almost everything presented to it

260
Q

Where does most absorption occur at the sm. intestine?

A

duodenum and jejunum

261
Q

Where is absorption of bile salts and vit. B12 done?

A

ileum

262
Q

Specialized Absorptive Sm. Intestine Surfaces

A

-folds to increase surface area
-microvilli
-600x greater than if it was flat

263
Q

Villus Structure

A

-epithelial cells cover surface
-connective tissue core
-capillary netwrok
-terminal lymphatic vessel (central lacteal)

264
Q

Crypts of Lueberkühn

A

-invaginations between villi
-don’t secrete digestive enzymes
-secrete water and electrolytes
-stem cells for new epithelial cells

265
Q

The lining of the sm. intestine is replaced every ___ days

A

3

266
Q

Protein and carb end products need _______ to cross the membrane during absorption.

A

cell-mediated transport systems

267
Q

How are the products of fat absorbed?

A

broken down and passively absorbed then enter lymph

268
Q

Carbohydrate Absorption (Glucose and Galactose)

A

-active transport by a) Na+ monosaccharide co transport or b) Na+ independent facilitated diffusion

269
Q

Carbohydrate Absorption (Fructose)

A

facilitated diffusion

270
Q

Carbs and proteins _____ into blood

A

diffuse

271
Q

How are proteins absorbed?

A

Na+ depended transport

272
Q

Free Ride

A

glucose, galactose, amino acids get a free ride on the energy expended for Na+ transport

273
Q

How do the Micelle contents enter epithelial cells?

A

passive transport

274
Q

Once entered epithelial cells, monoglycerides and fatty acids are…

A

resynthesized into triglycerides and packaged into chylomicrons

275
Q

Chylomicrons

A

-packaged triglycerides coated in a lipoprotein that makes them water soluble

276
Q

Do chylomicrons enter the blood?

A

no, they go to the central lacteal in the villus (lymph vessel)

277
Q

The large intestine is primarily a ______ and _______ organ.

A

drying (salt and water absorption) and storage (of feces)

278
Q

What does the lg. intestine receive from the sm. intestine?

A

-indigestible food residue
-unabsorbed biliary components
-remaining fluid

279
Q

Taeniae Coli

A

-longitudinal bands of muscle in the lg. intestine

280
Q

Haustra

A

-pouches or sacs on the lg. intestine
-actively change location due to smooth muscle contraction

281
Q

What is the main motility of the colon?

A

haustral contractions

282
Q

How fast are haustral contractions? What regulates them?

A

-slow
-the autonomic rhythmicity of sm. muscle cells

283
Q

Mass Movements

A

-massive contractions of the colon to move contents into distal part
-stored until defecation

284
Q

Gastrocolic Reflex

A

-from stomach to colon
-regulated by ANS and gastrin
-followed by urge to defecate
-evident after 1st meal of the day
-used to make room for new meals

285
Q

What initiates the defecation reflex?

A

stretch receptors in the rectal wall

286
Q

Where are the sensory receptors sent?

A

sacral portion of the spinal cord

287
Q

Does the parasympathetic or sympathetic NS initiate the reflex?

A

parasympatheic

288
Q

What type of muscle is the internal anal sphincter?

A

smooth muscle

289
Q

What type of muscle is the external anal sphincter?

A

skeletal muscle

290
Q

Does the lg. intestine secrete digestive enzymes?

A

no

291
Q

What does the lg. intestine secrete?

A

-alkaline mucous solution
-lubrication and neutralizing acid produced by bacteria

292
Q

Gastrin Summary

A

-stimulated by presence of proteins in the stomach
-inhibited by acid accumulation in stomach
-increase HCl and pepsinogen secretion
-enhances motility, mass movements
-GI tract lining maintenance

293
Q

Secretin Summary

A

-stimulated by presence of acid is duodenum
-inhibits emptying into sm. intestine when acid already present
-stimulates duct cells to excrete alkaline solution
-stimulates bile secretion
-trophic to exocrine pancreas

294
Q

CCK Summary

A

-inhibits motility and secretion
-stimulates acinar cells to secrete pancreatic enzymes
-gallbladder contraction
-trophic to exocrine pancreas

HLSC 128 - Human Physiology II (11 decks)

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