Chapter 16 - Digestive System Flashcards
1
Q
Four major functions of digestive system
A
Motility
Secretion
Digestion
Absorption
2
Q
Motility
A
Muscular activity, mix and move
3
Q
Propulsive motility vs mixing motility
A
Propulsive: push contents forward thru digestive tract
Mixing: mixing food with digestive juices, absorption
4
Q
Digestive secretions
A
Consist of water, electrolytes and specific organic constituents
-released into GI lumen with appropriate neural/hormonal stimulation
-usually reabsorbed into blood after participation
5
Q
Digestion
A
-biochemical breakdown into smaller absorbable units
-digestive enzymes
6
Q
Carbohydrates into
A
Monosaccharides
7
Q
Proteins into
A
Amino acids
8
Q
Fats
A
Glycerol and fatty acids
9
Q
Only ___ are absorbed by the intestinal cells for use in the body
A
Monosaccharides
10
Q
Disaccharides and polysaccharides must be
A
Digested to monosaccharides before they can be absorbed for use in the body
11
Q
2 monosaccharides linked together =
A
Double sugar or disaccharide
12
Q
Many sugar linked together =
A
Polysaccharide
13
Q
Maltose hydrolysis into
A
Glucose and glucose
14
Q
Examples of polysaccharides
A
Starch, cellulose, glycogen
15
Q
Disaccharides example
A
Sucrose, lactose, maltose
16
Q
Monosaccharides example
A
Glucose, fructose, galactose
17
Q
What examples are composed of glucose
A
Start, cellulose, glycogen
18
Q
Glucose fructose makes up
A
Sucrose
19
Q
Glucose galactose makes up
A
Lactose
20
Q
Glucose glucose makes up
A
Maltose
21
Q
Proteins are broken down to
A
Peptide fragments
22
Q
Peptide fragments are further digested to
A
Free amino acids
23
Q
Free amino acids —->
A
Enter epithelial cells
24
Q
Short chains of two or three amino acids can be absorbed (true or false)
A
True
25
Dietary fats are
Triglycerides
26
Digestion produces 2 _____ ____ _____ and _______
2 free fatty acids, monoglyceride
27
Absorption
Smaller units resulting rom digestion along with water
-vitamins, electrolytes
-transferred from GI to blood or lymph
28
Mouth and salivary glands (motility, secretion, digestion, absorption)
-chewing
-saliva (amylase, mucus, lysozyme)
-carbohydrate on digestion begins
-medications such as nitroglycerin
29
Pharynx and oesophagus (motility, secretion, digestion, absorption)
-swallowing
-mucus
-no digestion
-no absorption
30
Stomach (motility, secretion, digestion, absorption)
-peristalsis
-gastric juice
-carbohydrate, protein
-lipid solvable substances (alcohol and aspirin)
31
Gastric juice
HCl, pepsin, mucus, intrinsic factor
32
saliva
Amylase, mucus, lysozyme
33
Exocrine pancreas
-no motility
-pancreatic digestive enzymes
-various digestion in duodenal lumen
-no absorption
34
Liver (motility, secretion, digestion, absorption)
-no motility
-bile
-bile salts facilitate fat digestion and absorption
-no absorption
35
Small intestine (motility, secretion, digestion, absorption)
-segmentation, migrating motility complex
-succus entericus, mucus, salt
-carbohydrate and protein, fat 100%
-all nutrients most electrolytes and water
36
Large intestine (motility, secretion, digestion, absorption)
-haustral contractions, mass movements
-mucus
-no digestion
-salt and water, convert to feces
37
Pancreatic digestive enzymes
-tripsin, chymotrypsin, carboxypeptidase
-amylase
-lipase
38
Bile
-bile salts
-alkaline secretion
-bilirubin
39
Parts of small intestine
-duodenum
-jejunum
-ileum
40
Large intestine
-cecum
-appendix
-colon
-rectum
41
Accessory digestive organs
-salivary glands
-exocrine pancreas
-liver/gallbladder
42
Digestive tract
Mouth, throat, oersophagus, stomach, small intestine, large intestine and anus
43
Biliary system
Gallbladder, liver
44
Four major tissue layers
-mucous
-submucosa
-muscularis externa
-serosa
45
Innermost tissue layer
Mucosa
46
Outer layer
Serosa
47
Mucosa
Lines luminal surface
-highly folded surface (more SA)
48
three layers of mucosa
-mucous membrane
-lamina propria
-muscularis mucosa
49
Mucous membrane
-protective surface
-secretion and absorption
Contains: exocrine, endocrine, epithelial
50
Exocrine gland cells
Secrete digestive juices
51
Endocrine gland cells
Secrete blood borne gastrointestinal hormones
52
Epithelial cells
Specialized for absorbing digestive nutrients
53
Lamina propria
Houses gut associated lymphoid tissue
-important in defence against disease causing intestinal bacteria
54
Muscularis mucosa
Spare layer of smooth muscle
55
Submucosa
-thick layer
-provides GI tract with distensibility and elasticity
-larger blood and lymph vessels
56
Nerve network in submucosa
Submucosa plexus
57
Muscularis externa
-major smooth muscle coat
-circular and longitudinal later
58
Circular layer
Inner layer
-contraction decreases diameter of lumen
59
Longitudinal layer
Outer layer
-contraction shortens the tube
60
Interstitial cells of cajal
-cells between the two muscle layers
-origin of rhythmic electrical activity
Basic electrical rhythm
61
Myenteric plexus
-lies between the two muscles layers
-extensive network of nerve cells
62
What are the intrinsic nerve plexuses (2)
-myenteric plexus
-submucosal plexus
63
Serosa
-secretes serous fluid
-continous with mesentery throughout much of the tract
64
serous fluid
Lubricates and prevents friction between digestive organs and surrounding viscera
65
Function of a continous mesentery
-attachment provides relative fixation
-support digestive organs in proper place
66
Digestive motility and secretion are regulated by
-Autonomous smooth muscle function
-intrinsic nerve plexuses
-extrinsic nerves
-gastrointestinal hormones
67
Autonomous smooth muscle function
Pacemaker cells
-interstitial cells of Cajal
-BER
68
Intrinsic nerve plexuses
ENS = myenteric and submuscosal plexuses
-sensory and motor functions
69
Extrinsic nerves
ANS
70
Gastrointestinal hormones
-gastrin
-brain function
71
Uvula
Seals off nasal passages during swallowing
72
Pharynx
Cavity at rear of throat
-common passageways for digestive and respiratory systems
-tonsils
73
tonsils
-lymphoid tissue
74
Function of chewing
Grind and break food into smaller pieces to make swallowing easier and increase food surface area on which salivary enzymes can act
75
Three pairs of salivary glands
-parotid
-sublingual
-submandibular
76
Secretions in the mouth are accomplished by
Large increase in blood flow
-this is the largest secretion of any exocrine gland
77
Composition of saliva
99.5% H20
0.5% electrolytes and protein (amylase, mucus, lysozyme)
78
Amylase
Beings digestion of carbohydrates
79
saliva
-swallowing by moistening food
-provides lubrication
80
Antibacterial action of saliva
-lysozyme destroys bacteria
-saliva rinses away material that could serve as food source for bacteria
81
Solvent for molecules stimulate
Taste buds
82
What stimulates salivary centre in medulla
-pressure receptors and chemoreceptors in mouth
-thinking, seeing, smelling (cerebral cortex)
83
Salivary centre in medulla signals
Autonomic nerves, which target salivary glands increasing salivary secretion
84
Polysaccharides are digested in the mouth into ____
Disaccharides
85
Motility of swallowing associated with
Pharynx and esophagus
86
Two sphincters of the esophagus
-pharyngoesophageal sphincter
-gastroesophageal sphincter
87
pharyngoesophageal sphincter
Prevents large volumes of air from entering esophagus and stomach during breathing
88
Gastroesophageal sphincter
Prevents reflux of gastric contents
89
Stomach is divided into three sections called
Fundus, body, antrum
90
Stomach mucosa is divided in two two areas
Oxyntic, pyloric gland area
91
Three main functions of stomach
-store ingested food until emptied into small intestine
-secretes HCl and enzymes that begin protein digestion
-mixing movements turn food to chyme
92
Stomach motility aspects (four)
-filling (50 mL to 1L)
-storage (body)
-mixing (antrum)
-emptying (duodenum factors and peristalsis)
93
The stronger the antral contraction the
More chyme is emptied with each contractile wave
94
How does gastric mixing take place
When the pyloric sphincter closes, the chyme hits the closed sphincter and is tossed back into the antrum, mixing!
95
Factors in duodenum
-acid (inhibit further emptying of acidic gastric contents)
-hypertonicity (gastric emptying is inhibiting when osmolarity of duodenal contents start to rise)
-distension (too much chyme inhibits emptying of even more gastric contents)
96
Gastric emptying factors trigger either
-neural response
-hormonal response
97
Neural response
Mediated through both intrinsic nerve plexuses (short) and autonomic nerves (long)
-enterogastric reflex
98
Hormonal response
Involves release of hormones from duodenal mucosa collectively known as enterogastrones
-secretin
-cholecystokinin
99
Additional factors that influence gastric motility
-emotions (sadness/fear - decrease)(anger/aggression - inc)
-intense pain (inhibits)
100
Two distinct areas of gastric mucosa that secrete gastric juice
-oxyntic mucosa (lines body and fundus)
-pyloric gland area (lines antrum)
101
Mucous cells
Alkaline mucus
-protects mucosa against mechanical, pepsin and acid injury
-stimulated by mechanical
102
Chief cells
Pepsinogen
-begins protein digestion
-activated by ACh, gastrin
103
Parietal cells
Hydrochloride acid and intrinsic factors
-activates pepsinogen, breaks down connective tissue, denatures protein, kills microorganisms
-absorption of vitamin B
-stimulated by ACh, gastrin, histamine
104
Enterochromaffinlike cells
Histamine
-stimulates parietal cells
-stimulued by ACh, gastrin
105
G cells
Gastrin
-stimulates partial chief and ECL cells
-stimulated by protein products, ACh
106
D cells
Somatostatin
-inhibits partial, G, and ECL cells
-stimulated by acid
107
Functions of HCl
Activates pepsingoen to activate enzyme pepsin
-break down connective tissue and muscle fibres
-denatures protein
-kill microorganisms
108
Pepsinogen
Major digestive aspect of gastric secretion
-converted to pepsin
109
Pepsin
Splits certain amino acid linakages
-yield small amino acid chains
110
Gastrin
Stimulate histamine release from ECL cells
111
Cephalic phase
Stimuli acting in the head before food reaches stomach
112
Gastric phase
Begins when food reaches the stomach (protein)
-proteins stimulate nerve pathways and gastrin release
113
Intestinal phase
Inhibitory phase
-helps shut off flow of gastric juices as chy,e begins to empty into small intestine
114
Gastric mucosal barrier
Enables stomach to contain acid without injuring itself
115
Pancreas
Mixture of exocrine and endocrine tissue
-elongated gland
116
Duct cells
Secrete aqueous NaHCO3 solution
117
Acinar cells
Secrete digestive enzymes
118
Exocrine function
Acinar cells secretes pancreatic juice consisting of
-zymogen granules
Duct cells secrete aqueous alkaline
119
Proteolytic enzymes
-trypsinogen
-chymotrpsinogen
-procarboxypeptidase
120
Trypsinogen
Converted to active form trypsin
121
Chymotrypsinogen
Converted to active form chymotrypsin
122
Procarbpxypeptidase
Converted to active form carbodypeptidase
123
Pancreatic amylase
Converts polysaccharides into disaccharide maltose
124
Pancreatic lipase
Only enzyme secreted throughout entire digestive system that can digest FAT
125
Trypsin and chymotrypsin
Break peptide bonds in proteins to form peptide fragments
126
Carboxypeptidase
Splits off terminal amino acid from carbonyl end of protein
127
Liver
Largest and most important metaboloc organ in body
-major biochemical factory
-secretion of bile salts
128
Bile salts
Fat digestion and absorption
-derivatives of cholesterol
129
Bile consists of
Bile salts, cholesterol, lecithin, bilirubin
130
Function of bile salts
Break up large fat droplets with intestinal mixing
-inc surface area for lipase
131
Micelle
Critical for fat absorption
-water soluble structures
-transports digested fats
132
Gall bladder
-secreted bile is stored imbetween meals
-concentrates bile (salt transported out, water follows)
-primary site for precipitation—> gallstones
133
Segmentation
-primary method of motility during digestion
-ring like contractions
-mixes chyme
-relax/contract
134
Segmentation initiated by
Pacemaker cells in small intestine
-basic electrical rhythm (BER)
135
Migrating motility complex
Peristaltic wave sweeps intestines clean between meals
136
Secretions of small intestine
Does not contain digestive enzymes
-lubricates
-salt solution
137
Brushy border enzymes
-enterokinase
-disaccharidase
-aminopeptidases
138
Enterokinase
Trypsinogen to trypsin
139
Disaccharidases
Disaccharides to monosaccarides
140
Aminopeptidases
Peptides to amino acids
141
Function of pancreatic enzymes
Continue carbohydrate and protein digestion
142
Brush border enzymes function
Complete digestion of carbohydrates and protein
143
Pancreatic lipase function
Fat digested entirely
144
Small intestine absorption
-absorbs nearly everything (liquids and solids)
-Vit B12 and bile salts
145
Crypt of lieberkuhn
Part of alveoli
-secretes watery solution and new epithelial cells
146
Large intestine
Drying and storage
147
Taeniae coli
Longitudinal bands of muscle
148
Haustra
Pouches or sacs
-Change location as result of contraction
149
Mass movements
Massive contractions
-moves colonic contents into distal part of LI
150
Gastrocolic reflex
From stomach to colon
-most evident after first meal of the day
-urge to defecate
151
Defecation reflex
-stretch receptors stimulated by distension
-internal anal sphincter to relax and rectum/sigmoid colon to contract more vigorously (PARASYMPATHETIC)
152
Colonic secretions
Alkaline mucous solution
153
Colon absorption
Salt and water
154
Constipation vs diarrhea
C: dry feces, blockages, decreased motility (low bulk diet)
D: loss of watery material, cannot absorb it all, fluid bulk, inc secretion (NOT INC MOTILITY)
155
Gastrin
-stimulated by protein in stomach
-inhibited by acid in stomach
Function: inc secretion of HCl and Pepsi oven
156
Secretin
Stimulated: acid in duodenum
Function: stimulate pancreatic duct cells to produce aqueous NaHCO3 secretion
157
CCK
Inhibits gastric motility and secretion
-stimulate pancreatic Alina cells to inc secretion of pancreatic enzymes
