Digestive System Flashcards
(204 cards)
1
Q
What is the gastrointestinal tract?
A
Long tube, approximately 23 feet
2
Q
How does the GI tract control the movement of contents from one area to another?
A
GI tract contains sphincters
3
Q
What are the four sphincters of the GI tract?
A
cardiac, pyloric, ileocecal, and anal sphincters
4
Q
Cardiac sphincter location
A
between the esophagus and stomach (located level with the heart)
5
Q
Cardiac sphincter function
A
prevents contents of stomach from coming back up the esophagus
6
Q
Pyloric sphincter location
A
between stomach and duodenum (first part of the small intestines)
7
Q
Pyloric sphincter function
A
Control the rate of emptying the stomach and acid neutralization
8
Q
Ileocecal sphincter location
A
between small and large intestine
9
Q
Anal sphincter location
A
between rectum and outside
10
Q
Accessory organs of the GI tract do not contain what?
A
do not contain ingested material but help with digestion (e.g. teeth, liver)
11
Q
The mouth is the site for what?
A
- Site where food enters the digestive tract, aka ingestion
- Site of sensory receptors
12
Q
How do the lips, cheeks, and tongue assist in digestion?
A
manipulate and hold food for chewing
13
Q
Teeth are responsible for what function?
A
used for mechanical digestion
14
Q
What two substances are teeth composed of?
A
the bone-like material dentin and enamel
15
Q
What are the four types of teeth that humans have?
A
- Incisors
- Canines
- Molars
- Bicuspids
16
Q
Incisors function
A
biting (like scissors)
17
Q
Canines function
A
ripping
18
Q
Molars and Bicuspids function
A
chewing/grinding (like tenderizers)
19
Q
What are the two sets of teeth that humans receive in their lifetime?
A
Baby/deciduous/milk teeth (20)
Permanent teeth (32)
20
Q
What structure covers the dorsal surface of the tongue?
A
papillae (dem bumps on the tongue)
21
Q
What are the functions of the tongue?
A
Manipulation of food
The primary site of taste buds
Secretes lingual lipase
22
Q
What is lingual lipase?
A
enzyme that breaks down lipids
23
Q
Salivary glands function
A
Secrete saliva for moistening and digestion
24
Q
How much saliva do humans secrete daily?
A
1.5 L /day
25
What are the three pairs of salivary glands?
- Parotids
- Sublingual
- Submandibular
26
Parotid glands location
near ears
27
Sublingual glands location
under tongue
28
Submandibular location
under tongue, behind sublinguals
29
Composition of saliva: percentage
99.5% water
0.5% solutes
30
What solutes are found in the saliva?
- Salts
- Lysozyme
- Salivary amylase
- Mucins
31
Lysozyme function
destroy bacteria
32
Salivary amylase function
starch breakdown
33
Mucins function
lubrication
34
What are the functions of saliva?
Keeps membranes moist
Dissolves chemicals for taste
Lubricates and begins chemical digestion of food
35
Define mechanical digestion
mastication of food to form a bolus
36
What is a bolus?
mixture of food and saliva
37
What enzymes are involved in the chemical digestion taking place in the mouth?
Salivary amylase and Lingual lipase
38
Salivary amylase function
breakdown starch into simple sugars
39
Lingual lipase function (again)
STARTS lipid digestion
- Most lipid digestion does not begin until in the stomach
40
What is the bolus role in continuing the digestive process from the mouth to the rest of the body?
the bolus is pushed back to the pharyngeal (pharynx) region by the tongue initiating the swallowing reflex
41
The pharynx is the common passageway to what to tracts?
to both GI and respiratory tract
42
The pharynx is responsible for what problem in the mouth?
choking
43
What is the pharynx function in the GI tract?
connects mouth to esophagus
44
Esophagus characteristics
- About 10 inches long
- Passes through diaphragm
- Upper 1/3 is skeletal muscle, lower 2/3 is smooth muscle
45
Esophagus function
Connects pharynx to the stomach
46
What process pushes food along?
peristalsis
47
Peristalsis
The involuntary contraction of the muscles of the intestine or another canal creates wave-like movements that push the contents of the canal forward.
48
How is the bolus moved to the stomach?
- Circular muscles above bolus contract (pushes food
forward)
- Simultaneously, longitudinal muscles contract and
shorten section just below bolus
- This action pushes esophagus walls outward to receive bolus
- Alternating contractions and relaxations move food
towards stomach
49
What causes heartburn?
- Occurs when the cardiac sphincter at the base does not
close
- Hydrochloric acid from the stomach splashes back
into esophagus
- Esophagus does not have a protective coating like
stomach and is burned
- the resulting pain is referred to as heartburn
50
The stomach contains what structures?
- Cardia
- Fundus
- Body
- Pyloris
- Pyloric sphincter
51
What is the Cardia?
The part of the stomach that is closest to the esophagus.
Food and liquids pass through the cardia to enter the stomach from the esophagus.
52
What is the Fundus?
The fundus is a dome-shaped section at the top of the stomach.
It does not usually store food unless the stomach is full.
The fundus stores any gas that is a byproduct of digestion.
53
What is the body of the stomach?
main portion of the stomach that holds and churns food
54
What is the pylorus?
The furthest part of the stomach that connects to the duodenum
55
How much content can the stomach hold at a given time?
1.5 L
56
What are the folds in the mucosal layer of the stomach called?
rugae
57
What is the function of rugae?
increase the surface area of the stomach
58
The stomach contains 3 layers of muscle for what purpose?
Very muscular for mixing & mechanical digestion
59
What are the three muscular layers of the stomach?
- longitudinal
- circular
- oblique
60
What are the structures that are dotted over the mucosa of the stomach called?
gastric pits
61
Gastric pits contain what kind of glands?
exocrine glands
62
What is the epithelium of the gastric pits composed of?
Mucous surface and neck cells
63
Mucous surface and neck cells function
secrete mucous
64
What other cells are found in the stomach's gastric glands (below the gastric pits)?
- Chief (zymogenic) cells
- Parietal cells
- G cells- gastrin
65
Chief (zymogenic) cells function
secrete pepsinogen
66
What is pepsinogen?
a substance that is secreted by the stomach wall and converted into the enzyme pepsin by gastric acid.
67
Parietal cells function
secrete HCL and intrinsic factor
68
What is an intrinsic factor?
an active form of B12
69
G cells function
secrete gastrin
70
What is the function of gastrin?
- Stimulates chief and parietal cells to release their secretions
- Initiates the contractions of gastric wall
71
How long can food remain in the stomach (fundus) before digestion is initiated?
1 hour
72
Mechanical digestion: stomach
mixing waves of peristalsis mix the
food with secretions and serve to break it down
73
What is the product/mixture formed from the mechanical digestion of the stomach?
chyme
74
What is the primary form of digestion in the stomach?
mechanical digestion
75
What two chemicals are involved in the chemical digestion in the stomach?
hydrochloric acid (HCl) and pepsin
76
What is the pH of HCl?
2
77
What are the actions of HCl in the stomach?
- Secretion of acid stops the action of amylase and activates lipase from saliva
- Kills microbes
- Activates pepsinogen to pepsin (protein digestion)
- Activates hormones for secretion of bile and pancreatic enzymes
78
What is the primary function of HCl?
Activates pepsinogen to pepsin (protein digestion)
79
What protects the stomach from being destroyed by HCl?
Mucus lining protects the stomach from acid.
80
The stomach is primarily responsible for the digestion of what macronutrient?
protein
81
Why does very little absorption take place in the stomach?
the mucous lining of the stomach
82
What material CAN be absorbed in the stomach?
water, ions, caffeine
83
How long does it take for the stomach to empty into the duodenum?
2-6 hours after eating
84
What three phases are responsible for controlling gastric secretions?
cephalic, gastric, and intestinal phase
85
What initiates the cephalic phase?
Sensory receptors in the head:
- sight
- smell
- thought of food
86
Cephalic phase: neurological process
- The cerebral cortex and hypothalamus send signals
to medulla
- Impulse is sent along Vagus nerve to stomach to
begin secretion
- Also stimulates contraction of stomach
87
What initiates the gastric phase?
Sensory receptors in the stomach:
- Chemoreceptors detect changes in pH
- Stretch receptors detect distension of the stomach
88
What is the effect of more food entering the stomach on receptors?
higher pH and higher distension
89
The gastric phase is controlled through what processing system?
negative feedback
90
An increase in pH and distension causes what to happen to the cells in the stomach?
- mucous cells secrete mucous
- chief cells secrete pepsinogen
- parietal cells secrete HCl
- G cells stimulate contractions of stomach
91
Why does the stomach need to secrete HCl when more food enters the stomach?
Food increases the pH, and HCl lowers the pH back down in order to continue digestion
92
What happens when the contraction of the stomach causes some chyme to be ejected into the duodenum?
As chyme leaves, pH decreases and distension
decreases therefore fewer secretions are secreted
93
Why is the intestinal phase named what it is?
the intestines help to regulate the emptying of the contents in the stomach
94
What is the function of the intestinal phase?
prevent overfilling of duodenum
95
What initiates the intestinal phase?
receptors in duodenum
96
What is the function of the receptors in the duodenum?
Has an inhibitory effect on the stomach and its
secretions
- has stretch receptors that stop the activity in the stomach to process material in the duodenum and vice versa
97
What are the additional functions of the intestinal phase?
smooth muscle contraction and stomach emptying
98
What are the accessory organs of the digestive system?
Liver, Gall Bladder, and Pancreas
99
The pancreas empties into the duodenum via what?
pancreatic duct
100
The pancreas contains what kind of cells?
acini cells
101
Acini cells function
cells responsible for excretory function/ produce and secrete digestive enzymes
102
What is pancreatic juice composed of?
Water
Salts
Bicarbonate
Has enzymes involved in carbohydrate, protein, fat, and nucleic acid digestion
103
Bicarbonate function
Stops pepsin
- neutralizes stomach acid so as to not destroy the mucous lining
104
Alpha amylase is produced by what organ?
the pancreas
105
Alpha amylase function
further breaks down carbs
106
What is the largest gland in the body?
the liver (3lbs)
107
The liver contains what kind of cells?
hepatocytes
108
Hepatocytes function
secretes bile (1liter / day)
109
What is the pH of bile, and why?
pH 7.6-8.6
- help bring the pH of chyme up
110
Bile contains what?
- water, bile salts, cholesterol, bile pigments, ions, and lecithin
111
Bile salts function
emulsify lipids
- is a chemical means of breaking lipids down into smaller parts
112
What is the main bile pigment in the liver?
bilirubin
- a breakdown product of hemoglobin
113
Bilirubin is responsible for what characteristic of bile?
bilirubin has no iron causing into produce green coloring; thus why bile is green
114
What is Stercobilin?
is a breakdown product of bilirubin and is responsible for the brown color of feces
115
What are the functions of the liver?
Maintaining glucose levels in the blood (helps store excess glucose as glycogen)
Store some fats and makes cholesterol
De-aminates amino acids
Removal of drugs and hormones
Storage of vitamins and glycogen (vitamin A)
Removal and recycling of RBCs and other blood cells
Plasma protein synthesis
116
What does it mean to de-aminate amino acids?
removes amine group in order to use protein/amino acids as energy when low in glucose
117
Where is the pancreas located?
behind the stomach
118
Where is the gallbladder located?
small sac under the liver
119
What is the function of the gallbladder?
Storage and release of bile
120
How does the gallbladder release into the duodenum?
Release contents into the cystic duct, which joins the hepatic duct (coming out of the liver) to form common bile duct
121
Define digestion
breaking down of food materials for
use by cells of the body
122
Define ingestion
taking food into body
123
Digestive system: define secretion
Cells of the GI tract and glands secrete 7L of fluids
124
Define mechanical processing
physically breaking material down into smaller pieces; mixes with secretions
125
Define chemical digestion
breakdown of food using
digestive enzymes, acids
126
Digestive system: define absorption
passage of nutrients from GI tract
into blood or lymph
127
Define defecation
elimination of indigestible material
128
What are the four layers of the GI tract?
Mucosa
Submucosa
Muscularis
Serosa
129
Mucosa characteristics
- Innermost layer
- Modified in areas for specific function
- Composed of 3 layers
130
What are the three layers of the mucosa?
epithelium, lamina propria, and muscularis mucosa
131
Which layer of mucosa comes in direct contact with the content of the GI tract?
the epithelium layer
132
What are the functions of the epithelium layer of the mucosa?
- Protection against infections
- Secretion of enzymes, mucus, and hormones
133
What type of epithelium is at the esophagus and anal canal?
Stratified squamous epithelium
134
What type of epithelium is at the stomach and intestines?
Simple columnar epithelium
135
What type of tissue is the lamina propria composed of?
Areolar connective tissue and MALT
136
What does the lamina propria contain?
Contains blood vessels and lymph vessels
137
What is the role of the vessels located in the lamina propria?
These vessels are the route by which nutrients
are absorbed by the GI tract are transported
to other areas of body
138
What are the functions of the lamina propria?
- Functions to support epithelium
- Binds epithelium to muscularis
mucosa
139
What type of tissue is the muscularis mucosa?
thin layer of smooth muscle
140
Muscularis mucosa function
- Causes folds in the lining of the stomach and small
intestine
- Movement of these muscles ensures all
absorptive cells come in contact with food
141
What is the submucosa?
Dense irregular connective tissue that binds
mucosa to the third layer
142
The submucosa contains what?
Contains blood vessels, lymph vessels, glands, and nerves
143
The nerves of the submucosa form what?
Enteric nervous system : brain of the gut
144
What is the function of the Enteric nervous
system?
Controls movements of mucosa and diameter of blood vessels going to gut
145
Muscularis: What organs are composed of skeletal muscle for voluntary control?
- mouth
- pharynx
- upper portions of the esophagus
- external anal sphincter
146
The rest of the muscularis layer contains what kind of muscle?
smooth muscle (involuntary)
147
What are the two layers of the muscularis layer?
Inner: circular fibers
Outer: longitudinal fibers
148
Circular fibers function
Control the diameter
149
Longitudinal fibers function
control the shortening and lengthening
150
What organ contains a third layer of the muscularis and what is it called?
Stomach contains third layer (oblique fibers)
151
The circular layer is thickened in areas to form what?
sphincters
152
What is the function of the muscularis?
Function is to mix and propel food along
153
What is the serosa layer?
- Outermost layer of GI tract
- Composed of areolar connective tissue and epithelia
- Also called visceral peritoneum
154
What is the function of the serosa?
Functions in protection and attaching to other structures
155
What organ makes up the most length of the GI tract?
the small intestines
- approximately 20 ft long
156
What is the primary site of nutrient absorption?
the small intestines
157
What are the three sections of the small intestines?
Duodenum: shortest (top)
Jejunum: middle
Ileum: longest (bottom)
158
Jejunum function
primarily breaks down major molecules
159
Ileum function
absorption happen here mainly
160
The mucosa of the small intestines is modified for what purpose?
increase surface area
161
What are the three modifications to the mucosa of the small intestines?
Circular folds (plicae circulares)
Villi
Microvilli
162
Circular folds (plicae circulares) function
Control movement of chyme (spiral motion)
163
What are Villi?
projections from mucosal epithelium & lamina propria
- ½ - 1 mm long; give velvety appearance
164
What are Microvilli?
projections from the apical portion of epithelial cells (it sooo fuzzzy!!) (coming off villi)
165
Villi and microvilli function
secretion, absorption, and cellular sticking or adhesion
166
What are the types of small intestine muscular movements?
Segmentations and Migrating Motility Complexes (MMCs)
167
What is segmentation?
Local contractions in areas containing chyme
168
Segmentations do not function to do what?
Not for transporting chyme
169
Segmentations function
mix chyme with enzymes and bring it in contact with the walls of the intestine
170
When do Migrating Motility Complexes (MMCs) begin?
after segmentation ends
171
What are Migrating Motility Complexes (MMCs)?
a slow wave of peristalsis beginning at the stomach end, moving to the large intestine
172
Carbohydrate digestion
began in mouth; enzymes (salivary amylase) break polysaccharides into simple sugars for absorption
Alpha amylase (pancreas) finishes breaking down complex carbs left over
173
Protein digestion
4 pancreatic enzymes that finish protein digestion begun in stomach
174
What enzyme in the small intestines breaks down protein?
Protease
175
Lipid digestion
bile salts emulsify fats, and enzymes (lipases) break triglycerides down into fatty acids and glycerol
176
Nucleic acid digestion
nucleases that breakdown nucleic acids down into nucleotides
177
What are the three intestinal hormones?
Secretin
Gastric inhibitory peptide
Cholecystokinin
178
Secretin function
Increase bile secretion
179
Gastric inhibitory peptide function
Release of insulin and inhibits gastrin release
180
Cholecystokinin function
pancreatic secretion and bile release
181
How are carbohydrates absorbed?
as monosaccharides
182
How are proteins absorbed?
as amino acids and small polypeptides (2-3 amino acids)
183
How are short-chain fatty acids absorbed?
by diffusion
184
How are long-chained fatty acids absorbed?
Monoglycerides are surrounded by bile salts to form micelles which transport the lipids to villi for absorption (via endocytosis)
185
How are lipids absorbed?
Inside the cell, the lipids are combined with proteins to form chylomicrons for transport through the lymphatic system (via exocytosis then move into lacteal)
186
How long is the large intestines?
5 feet long
187
What separates the small intestines from the large intestines?
ileocecal sphincter
188
What structures make up the large intestines?
Appendix
Colon
Rectum
Anus
189
Appendix characteristics
Hangs inferior joined to the large intestines
190
What are the four sections colon?
Ascending: right side of the body
Transverse: crosses the abdomen
Descending: left side of the body
Sigmoidal: curves back to meet rectum (s-shaped)
191
Rectum
last 20 cm of GI tract
192
Anus
the terminal end of the GI tract; opening is controlled by the anal sphincter
193
What modification occurs in the mucosa of the large intestines
- the mucosa layer has no villi (because not doing any/much absorption)
- many goblet cells to produce mucus
194
What is the difference in the longitudinal layer of muscularis in the large intestine?
The longitudinal layer of muscularis is reduced to 3 bands of muscle called the teniae coli
195
Tenia coli function
act like a drawstring
- Gather lg. Intestine into pouches called haustra
196
How does chyme move from the small intestines to the large intestines?
Small intestines filters chyme into the large intestines little by little where they're made into larger masses in the large intestines
197
What are the two types of muscular movements of the large intestines?
Haustral churning and Mass peristalsis
198
Haustral churning
- Haustra relax and distend as they fill
- When filling reaches a certain point, they contract and propel contents forward (from haustra to haustra)
199
Mass peristalsis
- Strong peristaltic wave, beginning at the transverse colon and traveling to the rectum
- Pushes contents along
- Occur 3-4 times/day, usually after a meal
200
Any chemical digestion that occurs here is the result of what?
bacterial action
201
Are there digestive enzymes in the large intestines?
nope
202
Bacterial action function
- chemical digestion in the large intestines
- produces vitamins B and K
- products are absorbed into bloodstream and transported to the liver
203
What are the functions of the large intestines?
Final absorption of water (1 liter)
Collection and compaction of wastes for removal
204
Feces characteristics
3-10 hours after reaches large intestines, is converted to feces
5% of feces is bacteria
Feces are eliminated by defecation
