CH 25 Digestive system Flashcards
(305 cards)
1
Q
What is gastroenterology?
A
the study of the digestive tract and the diagnosis and treatment of its disorders
2
Q
What is the digestive system?
A
organ system that processes food, extracts nutrients, and eliminates residue
3
Q
What are the 5 stages of digestion?
A
Ingestion
Digestion
Absorption
Compaction
Defecation
4
Q
what is Ingestion?
A
selective intake of food
5
Q
What is Digestion?
A
mechanical and chemical breakdown of food into a form usable by the body
6
Q
What is Absorption?
A
uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph
7
Q
What is Compaction?
A
absorbing water and consolidating the indigestible residue into feces
8
Q
What is Defecation?
A
elimination of feces
9
Q
What is mechanical digestion?
A
physical breakdown of food into smaller particles
Cutting and grinding action of the teeth
Churning action of stomach and small intestines
10
Q
What is chemical digestion?
A
a series of hydrolysis reactions that breaks dietary macromolecules into their monomers
11
Q
Which nutrients are present in a usable form in ingested food and can be directly absorbed?
A
Vitamins, amino acids, minerals, cholesterol, and water
12
Q
Where are digestive enzymes produced?
A
salivary glands
stomach
pancreas
small intestine
13
Q
What are the two subdivisions of the digestive system?
A
Digestive tract
Accessory organs
14
Q
What is the Gastrointestinal tract?
A
stomach and intestines
15
Q
What are the accessory organs of the digestive system?
A
Teeth
tongue
salivary glands
liver
gallbladder
pancreas
16
Q
What is another term for the digestive tract?
A
Alimentary canal
17
Q
What is the digestive tract?
A
30 ft long muscular tube extending from mouth to anus composed of:
Mouth
pharynx
esophagus
stomach
small intestine
large intestine
18
Q
Name the organ labelled A
A
Liver
19
Q
Name the organ labelled B
A
pancreas
20
Q
Name the organ labelled C
A
Gallbladder
21
Q
What are the main structural layers of the digestive system?
A
–Mucosa
–Submucosa
–Muscularis externa
–Serosa
22
Q
Name the layer labelled A
A
Mucosa
23
Q
Name he layer labelled B
A
Submucosa
24
Q
Name the layer labelled C
A
Muscularis externa
25
Name the layer labelled D
Serosa
26
What does the Mucosa Layer consist of?
* Epithelium
* Lamina propria
* Muscularis mucosae
27
What does the Serosa consist of
Thin layer of areolar tissue
topped with simple squamous epithelium
28
What is the submucosa?
Thicker layer of loose connective tissue
Contains blood vessels and lymphatics
29
What does the Muscularis externa consist of?
Two layers of muscle near the outer surface
30
What is –Mucosa-associated lymphatic tissue (MALT)?
the mucosa exhibits an abundance of lymphocytes and lymphatic nodules
31
where is MALT found in the body?
In every exposed system of the body
32
What is the muscularis externa?
consists of usually 2 layers of muscle near the outer surface
Inner circle layer
Outer longitudinal layer
33
What is serosa?
composed of a thin layer of areolar tissue topped by simple squamous mesothelium
34
What is the –Adventitia?
fibrous connective tissue layer that binds and blends the pharynx, most of the esophagus, and the rectum into adjacent connective tissue of other organs
35
What is the enteric nervous system?
nervous network in esophagus, stomach, and intestines that regulates digestive tract motility, secretion, and blood flow
36
Which of the other nervous systems is the enteric nervous system considered a part of?
–autonomic nervous system (ANS)
37
What are the 2 networks of neurons of the Enteric nervous system?
–Submucosal (Meissner) plexus: in submucosa
–Myenteric (Auerbach) plexus: parasympathetic ganglia and nerve fibers between the 2 layers of the muscularis externa
38
What is the fubction of the Submucosal (Meissner) plexus
* Controls glandular secretions of mucosa
* Controls movements of muscularis mucosae
39
What is the function of the Myenteric (Auerbach) plexus?
•Controls peristalsis and other contractions of muscularis externa
40
What are the mesenteries?
•connective tissue sheets that suspend stomach and intestines from abdominal wall
41
What is the Parietal peritoneum
a serous membrane that lines the wall of the abdominal cavity
42
What is the dorsal mesentery?
a translucent two-layered membrane extending to the digestive tract
43
Where might the anterior (ventral) mesentery be located?
* May hang freely in the abdominal cavity
* May attach to the anterior abdominal wall or other organs
44
What is the Lesser omentum?
a ventral mesentery that extends from the lesser curvature of the stomach to the liver
Attaches the stomach to the liver
45
What is the Greater omentum?
* hangs from the greater curvature of the stomach (its left inferior margin)
* Covers small intestine like an apron
46
What is the Mesocolon?
extension of the mesentery that anchors the colon to the abdominal wall
47
What is does Intraperitoneal mean?
when an organ is enclosed by mesentery on both sides
48
What does Retroperitoneal mean?
when an organ lies against the posterior body wall and is covered by peritoneum on its anterior side only
49
What is the membrane labelled A?
Lesser omentum
50
What is the membrane labelled B? yes that is a B
Greater omentum
51
What is the structure labelled A?
Mesocolon
52
What is the structure labelled B ?
Mesentery
53
How are motility and secretion of the digestive tract controlled?
* neural
* hormonal
* paracrine mechanisms
54
What are the two types of neural control?
Short (myenteric) reflexes
Long (vagovagal) reflexes
55
What is the function of the Short (myenteric) reflexes?
* stretch or chemical stimulation acts through myenteric plexus
* Stimulates paristaltic contractions of swallowing
56
What is the function of the –Long (vagovagal) reflexes?
parasympathetic stimulation of digestive motility and secretion (think rest and digest)
57
What is the function of Hormones in the digestive system?
* Chemical messengers secreted into bloodstream that stimulate distant parts of the digestive tract
* Gastrin and secretin
58
What is the function of Paracrine secretions in the digestive system?
## Footnote
–
Chemical messengers that diffuse through the tissue fluids to stimulate nearby target cells
59
What is the mouth also known as?
Oral or Buccal cavity
60
What are the functions of the mouth in the digestive system?
–Ingestion (food intake)
–Taste and other sensory responses to food
–Chewing and chemical digestion
–Swallowing, speech, and respiration
61
What type of cells is the mouth lined with?
•Stratified squamous epithelium
–Keratinized in areas subject to food abrasion: gums and hard palate
–Nonkeratinized in other areas: floor of mouth, soft palate, and insides of cheeks and lips
62
What is the Oral fissure?
anterior opening between lips
63
What is the Fauces?
posterior opening to the throat
64
What are the functions of the tongue in the digestive system?
–Manipulates food between teeth
–Senses taste and texture of food
–Can extract food particles from the teeth after a meal
65
What cells cover the surface of the tongue?
–Nonkeratinized stratified squamous epithelium covers its surface
66
What are the Lingual papillae?
bumps and projections that are the sites of most taste buds
67
Which part of the tongue is the root?
posterior 1/3
68
Which part of the tongue is the body?
Anterior 2/3
69
What is dentition?
The teeth
70
What does it mean to masticate?
* Chew food into smaller pieces to be swallowed
* Exposes more surface area to enzymes
* 1st step in mechanical digestion
71
How many adult teeth should you have?
32
72
How many teeth should be in the mandible?
16
73
How many teeth should be in the maxilla?
16
74
What are the different types of teeth?
Incisors
Canine
premolar
molars
75
What is the alveolus?
Tooth socket in the bone
76
What is the function of the peridontal ligament?
–Anchors tooth firmly in alveolus
–Allows slight movement under pressure of chewing
77
What is the Gingiva (Gum)?
Flesh that covers alveolar bone
78
What are the regions of a tooth?
–Crown: portion above the gum
–Root: the portion below the gum, embedded in alveolar bone
–Neck: the point where crown, root, and gum meet
–Gingival sulcus: space between the tooth and the gum
79
What is the region labelled A?
Crown
80
What is the region labelled B?
Neck
81
What is the region labelled C?
Root
82
What is occlusion?
Meeting of the teeth with mouth closed
83
What is the structure labelled 1?
Enamel
84
What is the structure labelled 2?
Dentin
85
What is the structure labelled 3?
Pulp in pulp cavity
86
What is the structure labelled 4?
Gingival sulcus
87
What is the structure labelled 5?
Gingiva
88
What is the structure labelled 6?
Alveolar bone
89
What is the structure labelled 7?
Peridontal ligament
90
What is the structure labelled 8?
Root canal
91
What is the structure labelled 9?
Cementum
92
What is the structure labelled 10?
Apical foramen
93
What is the structure labelled 11?
Artery, nerves and veins
94
How many deciduous teeth does a baby have?
20
95
what is Plaque?
sticky residue on the teeth made up of bacteria and sugars
96
What is Root canal therapy?
necessary treatment if cavity reaches pulp
97
What is Gingivitis?
inflammation of the gums
98
What is Periodontal disease?
destruction of the supporting bone around the teeth which may result in tooth loss
99
What is the result of calculus in the gingival sulcus?
wedges the tooth and gum apart
100
What is saliva?
hypotonic solution of 97.0%-99.5% water and solutes
101
What are the functions of saliva?
–Moistens mouth
–Begins starch and fat digestion
–Cleanses teeth
–Inhibits bacterial growth
–Dissolves molecules so they can stimulate the taste buds
–Moistens food and binds it together into bolus to aid in swallowing
102
What is salivary amylase?
–enzyme that begins starch digestion in the mouth
103
Name the solutes within saliva
104
What is Lingual lipase?
enzyme that is activated by stomach acid and digests fat after food is swallowed
105
What is Lysozyme?
enzyme that kills bacteria
106
What is the PH of saliva?
6.8-7.0 (neutral)
107
Which are the intrinsic salivary glands?
Lingual gland
Labial glands
Palatine glands
Buccal glands
108
where are the lingual glands located?
in the tongue
109
Where are the Labial glands located?
inside the lips
110
Where are the palatine glands located?
roof of the mouth
111
Where are the Buccal glands located?
Inside the cheek
112
Which are the extrinsic glands?
Parotid
Submandibular gland
Sublingual gland
113
Where are the parotid glands?
beneath the skin anterior to the earlobe
114
Where are the submandibular glands?
halfway along the body of the mandible
115
where are the sublingual glands located?
in the floor of the mouth
116
How much saliva do the extrinsic salivary glands secrete per day?
about 1-1.5 L
117
What is the function of the Cells of acini?
filter water and electrolytes from blood and add amylase, mucin, and lysozyme
118
What is the function of the Salivatory nuclei in medulla oblongata and pons
respond to signals generated by presence of food
119
Which nervous system is the salivatory nuclei controlled by?
ANS
120
What is Bolus
mass swallowed as a result of saliva binding food particles into a soft, slippery, easily swallowed mass
121
What is the pharynx?
muscular funnel connecting oral cavity to esophagus and nasal cavity to larynx
122
What are the three pharyngeal constrictors?
Superior
Middle
Inferior
123
What is the esophagus?
straight muscular tube 25 - 30 cm long
Extends from pharynx to cardiac orifice of stomach
124
What is heartburn?
burning sensation produced by acid reflux into the esophagus
125
What is the function of the lower esophageal sphincter?
* Prevents stomach contents from regurgitating into the esophagus
* Protects esophageal mucosa from erosive stomach acid
126
Describe the anatomy of the esophagus
–Nonkeratinized stratified squamous epithelium
–Esophageal glands in submucosa secrete mucus
–Deeply folded into longitudinal ridges when empty
–Covered with adventitia
127
What is another term for swallowing?
Deglutition
128
What is the swallowing centre?
pair of nuclei in medulla oblongata that coordinates swallowing
129
What are the phases of swallowing?
1. oral phase
2. pharyngeal phase
3. Esophageal phase
130
What phase of swallowing does the diagram depict?
Oral phase
131
What phase of swallowing does the diagram depict?
Pharangeal phase
132
What phase of swallowing does the diagram depict?
Esophageal phase
133
Which salivary glands are marked with A?
Parotid gland
134
Which salivary glands are marked with B?
Submandibular gland
135
Which salivary glands are marked with c?
Sublingual gland
136
what is the Stomach?
a muscular sac in upper left abdominal cavity immediately inferior to the diaphragm
137
What are the main functions of the stomach?
* food storage organ
* Mechanically breaks up food, liquefies it,
* begins chemical digestion of protein and fat
138
What is Chyme?
soupy or pasty mixture of semi-digested food in the stomach
139
WHat are the four regions of the stomach?
1. Cardiac region (cardia)
2. Fundic region (fundus)
3. Body (corpus)
4. Pyloric region
140
What is the Cardiac region?
small area within about 3 cm of the cardiac orifice
141
What is the Fundic region?
dome-shaped portion superior to esophageal attachment
142
What is the Body of the stomach?
makes up the greatest part of stomach
143
What is the pyloric region?
•narrower pouch at the inferior end
144
What is the function of the pyloric sphincter?
regulates the passage of chyme in to the duodenim
145
What is the structure labelled A?
Fundic region
146
What is the structure labelled B?
Greater curvature
147
What is the structure labelled C?
Lesser curvature
148
What is the structure labelled D?
Antrum
149
What is the structure labelled E?
Pyloric canal
150
What is the structure labelled F
Pylorus
151
What is the structure labelled G
Pyloric sphincter
152
Which nerve fibers does the stomach receive?
–Parasympathetic fibers from vagus
–Sympathetic fibers from celiac ganglia
153
Where is blood to the stomach supplied from?
branches of the celiac trunk
154
Where does blood from the stomach and intestines drain to?
enters hepatic portal circulation and is filtered through liver before returning to heart
155
What is the name of the wrinkles formed when the stomach is empty?
gastric rugae
156
What type of epithelium lines the stomach?
Simple columnar
157
How many layers does the muscularis externa of the stomach have?
3
158
What is this a picture of?
Gastric pits
159
What is the layer labelled A?
Mucosa
160
What is the layer labelled B?
Submucosa
161
What is the layer labelled C?
Muscularis externa
162
What is the layer labelled D?
Serosa
163
What is the function of Mucous cells?
Secrete mucous
164
What is the function of Regenerative (stem) cells?
–Divide rapidly and produce continual supply of new cells to replace cells that die
165
What is the function of Parietal cells?
* Secrete hydrochloric acid (HCl)
* intrinsic factor
* ghrelin
166
What is the function of hydrochloric acid in gastric juice?
* HCl activates pepsin and lingual lipase
* Breaks up connective tissues and plant cell walls
* Helps liquefy food to form chyme
* Converts ingested ferric ions to ferrous ions
* Contributes to nonspecific disease resistance
167
What is the function of Chief cells?
* Secrete gastric lipase
* pepsinogen
168
What is the function of Enteroendocrine cells?
* Secrete hormones
* paracrine messengers
169
How much Gastric juice is produced per day by the gastric glands.
2 to 3 L
170
What is Gastric juice made up of?
water
hydrochloric acid (high concentration)
pepsin
171
What is the PH of gastric juice?
Can be as low as 0.8
172
What are Zymogens?
digestive enzymes secreted as inactive proteins
173
What is the role of gastric lipase and lingual liase in digestion?
Digesta 10%-15% of dietary fats in the stomach
174
What is intrinsic factor?
a glycoprotein secreted by parietal cells
175
Name to Zymogens
Pepsinogen
Pepsin
176
What is the name of the linked reaction between Pepsinogen and Pepsin?
177
What is the function of instrinsic factor?
It is essential to the absorption of B12 by the small intestine
178
Why is vitamin B12 so important ?
It helps in synthesizing Hemoglobin
179
Given that secretion of intrinsic factor is the most important function of the stomach. Can we still digest food without it?
180
What type of chemical messengeres are produces on the gastric and pyloric glands?
Hormones
Paracrine secretions
Peptides
gut-brain peptides
181
How long does it typically take a meal to empty from the somach?
4 Hours
182
Which cells of the stomach control the rhythmic peristalsis?
pacemaker cells in longitudinal layer of muscularis externa
183
what center of the medulla oblongata signals stomach to relax
•Swallowing center
184
Which region of the stomach does the contraction become stronger?
Pyloric region
185
Where is alcohol absorbed?
Small intestine
186
Most digestion and nearly all absorption occur where?
small intestine
187
What do salivary and gastric enzymes partially digest in the stomach?
protein and lesser amounts of starch and fat
188
What are the three ways the stomach is protected from the harsh acidic environment?
Mucous coat
Tight junctions
Epithelial cell replacement
189
What can breakdown of the protective measures in the stomach lead to?
inflammation and peptic ulcer
190
What are the three phases of gastric activity?
Cephalic phase
Gastric phase
Intestinal phase
191
Nervous and endocrine systems collaborate to bring about which functions of the gastric function?
* Increase gastric secretion and motility when food is eaten
* suppress them when the stomach empties
192
Stomach being controlled by brain is which phase?
Cephalic phase
193
stomach controlling itself is which phase?
Gastric phase
194
Stomach being controlled by small intestine is which phase?
Intestinal phase
195
In which order do the gastric phases occur?
Phases overlap and can occur simaltaneously
196
Gastric secretion is stimulated by which 3 chemicals?
* Acetylcholine (ACh)
* Histamine
* Gastrin
197
Ingested food stimulates the gastric activity in which two ways?
Stretching the stomach
increasing the PH of it's contents
198
Which chemicals are involved in the intestinal phase?
secretin and cholecystokin (CCK)
199
•Small intestine receives what during the digestive process?
* chyme from stomach
* secretions from liver and pancreas
200
Where is the liver located?
Directly beneath the diaphragm
201
The liver is the body's largest
gland
202
One of the key functions of the liver is to
Secrete bile which contributes to digestion
203
Name the four lobes of the liver
right, left, quadrate, and caudate
204
What is the Porta hepatis
an irregular opening between quadrate and caudate lobes
205
What is the structure Labelled A?
Right lobe
206
What is the structure Labelled B?
Caudate lobe
207
What is the structure Labelled C?
Bare area
208
What is the structure Labelled D?
Right lobe
209
What is the structure Labelled E?
Gallbladder
210
What is the structure Labelled F?
Quadrate lobe
211
What is the structure Labelled G?
Porta hepatis
212
What is the structure Labelled H?
Falciform ligament
213
What is the structure Labelled I?
Left lobe
214
What is the structure Labelled J?
Round ligament
215
What is the structure labelled A?
Central vein
216
What is the structure labelled B?
Hepatic triad
217
What is the structure labelled C?
Hepatocytes
218
What is the structure labelled D?
Bile canaliculi
219
What is the structure labelled E?
Hepatic sinusoid
220
What is the structure labelled F?
Stroma
221
What are Hepatic lobules?
tiny cylinders that fill the interior of the liver
222
What is the Central vein?
It passes down the core of the liver
223
What are Hepatocytes?
cuboidal cells surrounding central vein in radiating sheets or plates
224
What are Hepatic sinusoids?
blood-filled channels that fill spaces between the plates
225
What are Hepatic macrophages (Kupffer cells)?
phagocytic cells in the sinusoids that remove bacteria and debris from the blood
226
What are the main functions of hepatocytes?
–After a meal absorb from the blood: glucose, amino acids, iron, vitamins, and other nutrients for metabolism or storage
–Between meals break down stored glycogen and release glucose into the blood
–Remove and degrade: hormones, toxins, bile pigments, and drugs
–Secrete into the blood: albumin, lipoproteins, clotting factors, angiotensinogen, and other products
227
What is the structure labelled A?
Gallbladder
228
What is the structure labelled B?
Hepatic ducts
229
What is the structure labelled C?
Common hepatic duct
230
What is the structure labelled D?
Cystic duct
231
What is the structure labelled E?
Bile duct
232
What is the structure labelled F?
Duodenim
233
What is the structure labelled G?
Pancreas
234
What is the structure labelled H?
Jejunum
235
Hepatic lobules are separated by a sparse connective tissue called
stroma
236
Between liver lobules is a heptaic triad made up of
* branch of hepatic portal vein
* branch of hepatic artery proper
* Bile ductule
237
Blood from the liver drains directly into the
Inferior vena cava
238
What is the gallbladder ?
* a pear-shaped sac on underside of liver
* simple columnar epithelium
* Head (fundus) usually projects slightly beyond inferior margin of liver
* Neck (cervix) leads into the cystic duct
239
What is the main function of the gallbladder?
Serves to store and concentrate bile by absorbing water and electrolytes
240
What is Bile?
yellow-green fluid containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids
241
What is Bilirubin?
* principal pigment derived from the decomposition of hemoglobin
* Responsible for the brown color of feces
242
What are Bile acids (bile salts)?
* steroids synthesized from cholesterol
* aid in fat digestion and absorption
243
What are Gallstones?
* hard masses in either the gallbladder or bile ducts
* may form if bile becomes excessively concentrated with wastes
244
What percentage of bile acids are reabsorbed in the ileum and returned to the liver
80%
245
What percentage of bile acids are excreted in the feces
20%
246
What is Cholelithiasis?
formation of gallstones
247
What is Painful obstruction of ducts
Result in jaundice (yellowing of skin), poor fat digestion, and impaired absorption of fat-soluble vitamins
248
What is Lithotripsy?
use of ultrasonic vibration to pulverize stones without surgery
249
What is the Pancreas?
spongy retroperitoneal gland posterior to greater curvature of stomach
250
Is the pancreas and endocrine or exocrine gland?
Both endocrine and exocrine
251
What is the endocrine function of the pancreas?
* pancreatic islets that secrete insulin and glucagon
* Concentrated in the tail of the gland
252
What is the exocrine function of the pancreas?
99% of pancreas that secretes 1,200-1,500 mL of pancreatic juice per day
253
What is the Pancreatic duct?
runs lengthwise through middle of the gland
254
What is the accessory pancreatic duct?
smaller duct that branches from the main pancreatic duct
255
What is Pancreatic juice?
alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other electrolytes
256
what is the function of sodium mbicarbonate in the liver?
Neutralizes HCL
257
What are zymogens?
Proteins that are converted into active digestive enzymes after secretion
258
What is trypsinogen?
A zymogen that becomes trypsin to digest protein
259
What is chymotrypsinogen?
A zymogen that becomes chymotrypsin to digest protein
260
What is procarboxypeptidease?
A Zymogen that becomes carboxypeptidease which hydrolyses the terminal amino acid from the carboxyl
261
Name the pancreatic enzymes
* Pancreatic amylase
* Pancreatic lipase
* Ribonuclease
* deoxyribonuclease
262
What is the function of Pancreatic amylase?
Digests starch
263
What is the function of Pancreatic lipase?
Digests fat
264
What is the purpose of Ribonuclase?
Digests RNA
265
What is the purpose of Deoxyribonuclease?
Digests DNA
266
What is the purpose of enterokinase in the pancreas?
Catalyst for zymogens to become enzymes
267
Which 3 stimuli are chiefly responsible for the release of pancreatic juice and bile?
* acetylcholine
* cholecystokinin
* secretin
268
Why is the small intestine referred to as small?
It has a small diameter of 2.5cm
269
What are the three regions of the small intestine?
* Duodenim
* Jejunum
* Ileum
270
What is the main function of the small intestine?
Nearly all chemical digestion and nutrient absorption occurs in the small intestine
271
What is the function of the duodenim?
* Receives stomach contents, pancreatic juice, and bile
* Fats are physically broken up (emulsified) by bile acids
* Pepsin is inactivated by increased pH
* Pancreatic enzymes perform chemical digestion
272
What is the main function of the jejunum?
Most digestion and nutrient absorption occurs here
273
Which three important structures are housed by the Ileum?
* Peyer patches
* Ileocecal junction
* Ileocecal valve
274
Circular folds (plicae circulares) of the small intestine increase surface area by a factor of
2-3
275
Villi increase surface area of the small intestine by a factor of
10
276
Microvilli increase the surface area of the small intestine by a factor of
20
277
Where do circular folds occur?
from duodenum to middle of ileum
278
What two types of epithelial cells are villi covered with?
* Absorptive cells (enterocytes)
* Goblet cells—secrete mucus
279
What is the main function of microvilli?
Increase absorptive surface area
280
What is the function of Brush border enzymes contained in plasma membrane of microvilli
Carry out some of the final stages of enzymatic digestion
281
What are Intestinal crypts (crypts of Lieberkühn)?
numerous pores that open into tubular glands on the floor of the small intestine between bases of the villi
282
What cells are clustered at the base of intestinal crypts?
Paneth cells
283
What is the function of the Duodenal glands found in submucosa of duodenum
* Secrete an abundance of bicarbonate-rich mucus
* Neutralize stomach acid and shield the mucosa from its erosive effects
284
How much intestinal juice do the crypts secrete per day?
1-2L
285
What is the PH of intestinal juice?
7.4-7.8
286
what are the three functions of the contractions of the small intestine?
–To mix chyme with intestinal juice, bile, and pancreatic juice
–To churn chyme and bring it in contact with the mucosa for contact digestion and nutrient absorption
–To move residue toward large intestine
287
What is the purpose of segmentation?
to mix and churn
288
What is the purpose of peristalsis?
to move the contents of the small intestine toward the colon
289
Which his the most digestable carbohydrate?
Starch
290
Which carbohydrate is indigestable?
Cellulose
291
80% of absorbed sugar is?
Glucose
292
Amino acids absorbed by the small intestine come from which three sources?
* Dietary proteins
* Digestive enzymes digested by eachother
* Sloughed epithelial cells digested by enzymes
293
Endogenous amino acids come from
internal sources
294
Exogenous amino acids come from
our diet
295
What are Proteases (peptidases)
enzymes that digest proteins
296
What happens to pepsin when it passes into the duodenim?
It is deactivated
297
How do Pancreatic enzymes take over protein digestion in small intestine
by hydrolyzing polypeptides into shorter oligopeptides
298
What makes digestion of lipids complicated?
Their hydrophobicity
299
What are lipases?
fat digesting enzymes
300
Before digestion in duodenum, vigorous pumping in stomach’s antrum does what to fats?
emulsifies the fat (breaks up globs)
301
Emulsification droplets are broken down further by
* bile
* lecithin
* agitation produced by intestinal segmentation
302
Lipase acts on
triglycerides
303
Absorption of free fatty acids, monoglycerides, and other lipids depends on minute droplets in the bile called
micelles
304
What diffuses in to the centre of micelle to form its core
Bile phospholipids and cholesterol
305
Micelles pass down the bile duct in to the
duodenim
