Chapter 16: The Digestive System Flashcards
1
Q
What is the purpose of the digestive system
A
- transfer nutrients, electrolytes. ect. from food to the internal environment (ECF)
2
Q
ingested food yields ATP that can be used by body cells for (4)
A
- transportation
- contraction
- synthesis
- secretion
3
Q
what percentage of ingested food is available for the bodys use
A
95%
4
Q
what are the 4 processes used in digestion
A
- motility
- secretion
- digestion
- absorption
5
Q
what are the 2 types of motility
A
- propulsive motility
- mixing movements
6
Q
what are the three types of digestion
A
- CHO
- proteins
- lipids/fats
7
Q
propulsive motility
A
- muscular contrations propel the food contents forward in the digestive tract
- allows appropriate velocity
8
Q
mixing movements functions
A
- mixes the food with the digestive juices
- exposes all portions of the food to the absorbing surface of the digestive tract
9
Q
secretion control
A
under neural or hormonal control
10
Q
secretion
A
digestive juices from the exocrine glands into the digestive lumen
11
Q
CHO is broken down into
A
monosaccarides
12
Q
proteins are broken down into
A
amino acids
13
Q
lipis/fats are broken down into
A
fatty acids
14
Q
carbohydrates (CHO)
A
- form of polysaccaride that consists of chains of interconnected glucose molecules
15
Q
types of CHO
A
- starch
- cellulose
- glycogen
- dietary CHO (Sucrose, lactose, ect)
16
Q
starch
A
plants
17
Q
cellulose
A
plant cell wall
18
Q
glycogen
A
body muscles (meat)
19
Q
what are the 3 disaccarides
A
- maltose
- sucrose
- lactose
20
Q
what breaks down maltose
A
maltase
21
Q
what breaks down sucrose
A
sucrase
22
Q
what breaks down lactose
A
lactase
23
Q
maltose breaks down maltase into
A
glucose
24
Q
sucrase breaks down sucrose into
A
glucose and fructose
25
lactase breaks down lactose into
glucose and galactose
26
absorption
- takes place in the small intestine
- transfers nutrients from the digestive tract luman to the body / lymph fluid
27
where does absorption occur
small intestine
28
what are the accessory digestive organs
- salivary glands
- exocrine pancreas
- bilary system
29
what are the digestive organs
- mouth
- pharynx
- esophagus
- stomach
- small intestine (duodenum, jejunum, ileum)
- large intestine (cecum, appendix, colon, rectum)
- anus
30
moth and salivary glands motility
chewing
31
pharynx and esophagus motility
swallowing
32
stomach motility
- receptive relaxation; peristalsis
33
small intestine motility
segmentation; migrating motility complex
34
large intestine motility
haustral contraction; mass movements
35
what are the 4 tissues layers of the digestive tract
- mucosa (innermost layer)
- submucosa
- muscularis externa
- serosa (outer layer)
36
mucous membrane
- protective surface
- modified secretion and absorption
37
mucous membrane contains
- exocrine gland cells
- endocrine gland cells
- epithelial cells
38
function of mucosa exocrine cells
digestive enzymes
39
mucosa endocrine glands function
- blood born gastrointestinal hormones (gastrointestinal peptide, GIP, secretion, gastrin)
40
mucosa epithelial cells function
absorbing digestive nutrients
41
what are the 2 divisions of the mucosa
- Lamina propria
- muscularis mucosa
42
lamina propria
- house gut associated lymphoid tissue (GALT)
- important in defence againt disease causing intestinal bacteria
43
Muscularis mucosa
- a thin layer of smooth muscle
44
submucosa
- provides the distensibility and elasticity to the GI tract
- contain blood and lymph vessels
- contains submucosal plexus
45
Muscularis externa
- forms smooth muscle coat of the GI tract
- contains the myenteric plexus
46
what are the 2 layers of the muscularis externa
- circular layer (innermost layer)
- longitudinal layer (outermost layer)
47
circular layer
- decreases the diameter of the lumen
- innermost layer
48
Longitudinal layer
- contraction shortens the GI
- outermost layer
49
myenteric plexus
- located in the muscularis externa
- lies between the two muscle layers
50
mesentery
- part of the serosa
50
Serosa
secretes fluid that lubricates and prevents friction between digestive organs and the surrounding viscera
51
mesentery 3 functions
- the attachment provides relative fixation
- secure the digestive organs in proper place
- allow the freedom for mixing and propulsive movements
52
lips
- help procure, guide, and contain food in the mouth
- important in speech
- provide tactile sensation
53
palate
- forms roof of the oral cavity
- contains uvula (seals off nasal passages during swallowing)
54
tongue
- composed of skeletal muscle
- aid in chewing and swallowing
- important role in speech
- houses taste buds
55
pharynx
- a common passageway for the digestive and respitory
56
tomsils
- within the walls of the pharynx
- lymphoid tissue
57
teeth
- responsible for mastication
58
mastication
chewing
59
3 functions of chewing
- grind and break food into smaller pieces to make swallowing easier and increase surface area for the salvairy enzyme to act
- mix food with saliva
- simulate taste buds
60
saliva is produced by
the salivary glands
61
compositionof saliva
99.5% H2O
0.5% electrolytes and protein (amalyze, mucus, lysozymes)
62
8 functions of saliva
- contains salivary amylase (carbohydrate digesting enzyme)
- facilitates swallowing by moistening food
- mucus provide lubrication
- antibacterial actions (lysozyme destroys bacteria)
- solvent for molecule that stimulates taste buds
- aids speech by movement of the tongue and lips
- helps keep the mouth clean
- rich in bicarbonate buffers
63
what transport is responsible for glucose and galactose reabsorption
- secondary active transport mechanisms
64
what transport mechanism is responsible for fructose reabsorption
facilitated diffusion
65
simple salivary reflex is activated by
- presence of food in the mouth
- pressure receptors and chemoreceptors in the mouth
66
conditioned salivary reflex is activated by
- prior experience of food
- cerebral cortex: thinking/smelling/seeing food
67
neural regulation of saliva is controlled by
- salivary centre in the medulla
- automatic nerves
68
effect of parasympathetic and sympathetic nervous system on salivary secretion
work SYNERGISTICALLY to increase salivary secretion
69
parasympathetic NS effect on salivary secretion
- stimulates a prompt and abundant saliva is rich in enzymes
70
Sympathetic NS effect of salivary secretion
- elicits smaller saliva volume; feeling mouth drier than usual 9during stress such as speech)
71
salivary secretion is einterly under ______ control
neural control
72
Swallowing is associated with
pharynx and esophargus
73
stages of swallowing
- oropharyngeal stage (voluntary)
- Esopharengeal stage (involuntary)
74
what are the two spinchters in the esophagus
- pharyngoesphageal
- gastroesophagea;
75
pharyngoesophageal sphincter
- prevent large volumes of air from entering into the esophagus and stomach during breathing
76
gastroensphageal sphincter
- prevents reflux of gastric contents
77
what pushes food through the esophagus
peristaltic waves
78
what protects the esophagus
mucus / secretions
79
stomach
j shaped sac-like chamber lying between the esophagus and the small intestine
80
what are the three sections of the stomach
- fundas
- budy
- antrum
81
what are the three functions of the stomach
- food storage
- secretions of HCl and enzymes for protein digestion
- pulverizes semi-solid food into chyme
82
Pyloris sphincter
- severs as a barrier between the stomach and the upper part of the small intestine
83
what are the four aspects of the stomachs gastric motility
- gastric filling
- gastric storage
- gastric mixing
- gastric emptying
84
gastric filling
- involves receptive relaxation
- enhances the stomachs ability to accommodate the extra volume of food
- triggered by the act of eating
- mediated by the vagus nerve
85
gastric storage
the body of the stomach
86
gastric mixing
the antrum of the stomach
87
gastric emptying
- controlled by factors in the duodenum
88
what are the factors in the stomach that regulate gastric emptying
- the amount of chyme in the stomach (influences the strenght of contractions)
89
what are the 4 factors in the duodenum that regulate gastric emptying
- fat(presents of fat in the duodenum prevents gastric emptying)
- acid (unneutralized acid inhibits gastric emptying)
- hypertonicity
- distension
90
fat digestion and reabsorption only takes place in the
small intestine
91
what are the 2 factors that trigger gastric motility
- neural response
- hormonal response
92
neural response
- mediated through the intrinsic nerve plexuses and automatic nerve reflexes
- collectively called enterogastric reflex
93
hormonal response
- involves relase of hormones from the duodenal mucosa, collectively known as enterogastrones
94
what are the enterogastrones
- secretin
- cholecytokinin (CCK)
95
vomiting is controlled by
the vomiting center in the medulla
96
vomiting is caused by
- deep inspiration
- closure of the glottis
97
vomiting is follwoed by
- salivation
- sweating
- rapid heart rate
- snesation of nausea
98
what are 7 causes of vomiting
- tactile stimulation of the throat
- irritation or distention of the stomach and duodenum
- elevated intracranial pressure caused by cerebral haemorrhage
- rotation or acceleration of head producing dizziness
- chemical agents (drugs)
- chemotherapy agents
- emotional factos
99
3 effects of vomiting
- loss of fluids and acid (results in metabolic alkalosis)
- reduction in plasma volume
- dehydration and circulatory problems
100
2 advantages of vomiting
- removal of noxious material
- removal of accidental ingestion of emetics and posion from the body
101
emetics
vomiting agents
102
what are the 2 distinct areas of gastric mucosa (gastric secretions)
- oxyntic mucosa
- pyloric gland area (PGA)
103
oxyntic mucosa location
- lines body and fundus
104
pyloric gland area location
lines the antrum
105
what are the three types of gastric exocrine seretory cells
- mucosal cells
- chief cells
- parietal (oxyntic) cells
106
mucosal cells
- line the gastric pits and the entrance of glands
- secrete thin, watery mucus
107
cheif cells
- secrete enzyme precursor pepsinogen
108
parietal cells
- secrete HCl and intrinsic factor
109
what are the functions of alkaline mucous
- protects mucosa against mechanical, pepsin, and acid injury
110
what is the function of pepsinogen
- when activated, begins protein digestion
111
what is the function of HCl
- activates pepsinogen, breaks down connective tissue, denatures proteins, kills microorganisms
112
what is the function of intrinsic factor
- facilitates absorption of vitamin B12
113
what are the 3 endocrine / paracrine cells
- Enterochromaffin - like cells (ECL)
- G cells
- D cells
114
what does the ECL cells secrete and function
- histamine
- stimulate parietal cells
115
what does G cells secrete and function
- gastrin
- stimulates parietal, cheif and ECL cells
116
what does the D cells secrete and function
- somatostain
- INHIBITS parietal, G and ECL cells
117
hormonal control of gastric activities is controlled by
the presence of acid in the duodenal luman
118
Negative feedback of gastric activities process
1. acid in the duodenal lumen
2. increases Secretin release from the duodenal mucosa
3. stimulates pancreatic duct cells
4. increases secretion of aq NaHCO3 (bicarbonate) into the duodenal lumen
5. nutralizes
119
the presences of acid in the duodenum stimulates the relase of
secretin in the blood
120
secretin functions
- inhibits emptying to prevent acid from entering the duodenum
- inhibits gastric secretions to reduce the normal acid production s
- stimualtes the pancreatic duct cells to produce bicarbonate to neutralize the acid
121
secretin and CCK are ______
trophic hormones to pancreas
122
presence of protein rich food in the stomach causes
gastrin release
123
functions of gastrin
- increases HCl (parietal cells) and pepsinogen (cheif cells) secretion --> promotes protein digestion
- enhances gastric mitility, stimulates ideal motility
-relaxes the ileocecal sphincter and induces mass movements of the colon
124
gastrin has trophic effects on the
stomach and small intestine
- to keep digestive tract viable
125
what are the major proteolytic enzymes on protein digestion
- trysinogen
- chymotrysinogen
- procarboxypeptidase
126
Dietary and endogenous proteins are hydrolyzed to their constitutes amino acids and a few small peptide fragments by
gastric pepsin and pancreatic proteolytic enzymes
127
amino acids enter the blood through
Na and energy dependent secondary active transport
128
pancreas is a ______ gland
mixed
129
pancreas endocrine functions
Islets of langerhans
- secrete insulin and glucagon
130
pancreas exocrine functions
secrete pancreatic jucies
131
pancreatic juice consits of
- pancreatic enzymes (secreted by acinar cells
- NaHCO3 (alkaline solution)--> secreted by duct cells
132
exocrine secretion of the pancreas is regulated by
- secretin
- CCK
133
proteolytic enzymes fucntion
digest protein
134
trysinogen
converted to active form trypsin
135
Chymotrysinogen
converted to active form chymotrysin
136
procarboxypeptidase
- converted to active form carboxypepidase
137
pancreatic amalyse
- converts polysaccarides into disaccarides
138
pancreatic lipase
- a fat digesting enzyme secreted throughout the entire digestive system
139
after participating in fat digestion, bile salts are reabsorbed back into the blood via
active transport mechanism
140
recycling of bile salts between the liver and the small intestine is refered to as
enterohepatic circulation
141
bile is secreted by
the liver
142
bile is stored and concentrated in the
gallbladder
143
bile consits of
- bile slats
- cholesterol
- lecithin
- bilirubin
144
bile salts are responsible for
emulfification
145
bile salts
- derivatives of cholestrol
- convert large fat globules into liquid emulsion
146
what percentage of bile salts are recycles
95%
147
what breads down triglycerides into monoglycerides and fatty acids
pancreatic lipase
148
monoglycerides and fatty acids are enclosed in a shell called
micelle
149
process of emulsification
bile salts --> large fat droplets --> small fat droplets --> enclosed in micelle
150
bile salts and lecithin contain both
a water soluble protion and a lipid soluable portion
151
the hydrophobic core of the micelle is made up of
- cholesterol
- bile salts (lipid soluble portion)
- lecithin (lipid soluble portion)
152
the hydrophilic shell of the micelle is made up of
- bile salt (water soluble portion)
- lecithin (water soluble portion)
153
what type of action do bile salt preform
detergent
154
water insoluable products are carried within the interior of the
micelle
155
micelles are extruded through the basal membrane by
exocytosis
156
iron absorbed into the blood is bound to
transferrin
157
ferritin
the pool of iron not absorbed by the blood
- converted to fecal matter
158
negative feedback of pancreatic lipase under control of CCK
fat and protein products in the duodenal lumen --> increases CCK release from the duodenal mucosa --> pancreatic acinar cell --> increases the secretion of pancreatic digestive enzymes the the duodenal luman --> digest fat and proteins
159
CCK is released in response to
the presences of fat and other nutrients
160
CCK functions
- inhibits gastric motility and secretion (allows more time for nutrients to be absorbed)
- stimulates pancreatic enzyme secretion of acinar cells
- causes the contration of the gall bladder and relaxation of the sphincter of oddi
- involved in long term adaptive changes
- stimulate food intake (satiety)
161
hepatitis
an inflammatory disease of the liver caused by a viral infection or exposure of a toxic substance
- can result in acute massive liver damage
162
Cirrhosis
- prolonged hepatic infection.
- associated with chronic alcholism
- damaged hepatocytes are permanently replaced by connective tissue
- causes gradual reduction in acute liver tissue, leading to chronic liver failure
163
where does most digestion and absorption take place
the small intestine
164
what percentage of absorption takes place in the small intestine
99%
165
what are the three segements of the small intestine
- duodenum
- jejunum
- ileum
166
segmentation
- the primary method of motility in the small intesitne consists or ring-like contractions
- action mixes chyme throughout the small intestine lumen
167
Segementation is intitated by
the pacemaker cells in the small intestine
- produce basic electrical rhythm (BER)
168
functions of segmentation
- mixes chyme with digestive juices screted into the small intestine lumen
- exposes all chyme to absorbative surfaces of the small intestine
169
where does absorption take place
the duodenum and jejunum
170
vili
microscopic figure like projections that increase the surface area of the small intestine
171
microvili
arise from the luminal surface of epithelial cells and increase surface area in the small intestine
172
functions of the colon
- extracts water and slat from contents
- temporary storage of feces
173
taeniae coli
- longitudinal bands of muscle
174
haustra
- pouches or sacs
- actively change location as a result of contration of cicular smooth muscle
175
haustual contractions
- main motility
- initiated by the autonomous rhythmicity of colonic smooth msucles cells
176
mass movements
- massive contractions
- moves colonic contents into the distal part of the large intestine
177
Gastrocoloic reflex
- mediated from the stomach to the colon by gastrin and by autonomic nerves
- most evident after the first meal of the day
- often followed by the urge to deficate
178
Defication reflex
- caused by the distention of the rectums stretch receptors
- internal and external sphincter relax
- voluntary
179
Constipation
- delay in deification; may result in constipation
180
constipation causes
- retention of colonic contents is longer than normal
- more than usual amount if water is reabsorbed from the feces; stool may be hard and dry
- delay is deification frequencies beyond normal
181
constipation symptoms
abdominal discomfort, dull headache, loss of appetites, followed by nausea, and mental depression
- disappear after defication
182
appendicitis
deposition of the hardened fecal material in the appendix causes inflammation
- appendix becomes swollen and filled with pus; may die as a result of local circulary interference
