Physiology and Anatomy: Small Intestine Flashcards
(94 cards)
1
Q
3 regions of the small intestine?
A
- Duodenum (shortest)
- Jejunum
- Ileum (longest)
2
Q
T/F: The majority of the duodenum is retroperitoneal?
A
True
3
Q
The jejunum has large _______
A
Plicae circulares
4
Q
The ileum has many large ________
A
Lymphoid nodules (Peyer’s Patches)
5
Q
Arterial supply of the first 2/3 of duodenum?
A
Hepatic artery of celiac trunk => superior pancreaticoduodenal art.
6
Q
What branch of the superior mesenteric artery also supplies the duodenum?
A
Inferior pancreaticoduodenal art.
7
Q
Arterial supply of the rest of the small intestine?
A
Superior mesenteric artery => jejunal and ileal arteries
8
Q
Venous drainage of the intestines?
A
Superior mesenteric (SI, LI, stomach and pancreas) + Splenic vein => portal hepatic vein
9
Q
Mucosa epithelium?
A
Simple columnar, villi
10
Q
Where are crypts of Lieberkuhn found?
A
In the mucosa of the duodenum, jejunum, and ileum
11
Q
What type of glands does the duodenum contain?
A
Brunner’s glands
12
Q
Are there any glands in the jejunum and ileum?
A
No
13
Q
What are plica circulares? What do they do? (3)
A
Folds in mucosa and submucosa
- Enhance absorption
- Increase SA
- Encourage mixing
14
Q
Each villus is covered by _______ with core of ______
A
Epithelium; Lamina Propria
15
Q
What is in the connective tissue of villi? (4)
A
Arteriole, venule, capillary network, lacteal
16
Q
What are microvilli and what do they do?
A
- Projections of apical membrane too small to be seen individually = brush border
- Greatly increase SA
17
Q
Where are goblet cells in the SI and what are they for?
A
Scattered among absorptive cells - secrete mucous to facilitate passage of materials
18
Q
What do Paneth cells do? (2)
A
- Regulate the microenvironment of intestinal crypts
- Initiate immune response
19
Q
Where are I cells? What do they secrete? What is their main function?
A
- Location: SI/duodenum
- Hormone: CCK
- Fun: Pancreatic enz secretion, GB contraction
20
Q
Where are S cells? What do they secrete? What is their main function?
A
- Location: SI
- Hormone: Secretin
- Fun: Bicarb and H2O secretion from pancreas, inhibit gastric emptying
21
Q
What do D cells secrete?
A
Somatostatin
22
Q
What do K cells secrete?
A
GIP
23
Q
Where are L cells? What do they secrete? What is their main function?
A
- Location: SI
- Hormone: Peptide YY
- Fun: Inhibit gastric secretion and motility
24
Q
Where are Mo cells? What do they secrete? What is their main function?
A
- Location: SI
- Hormone: Motilin
- Fun: Migrating motor complex
25
What does stretch from chyme against the intestinal wall elicit?
Concentric contractions
26
What does the spacing between contractions cause? What is it?
Segmentation - chyme from one segment forced into relaxed next = mixes and circulates
27
A powerful wave of contractile activity that travels long distances down the small intestine?
Peristaltic rush
28
Control of peristalsis can be _____ or ______
Nervous or Hormonal
29
Nervous control of the gut? (3)
- Law of the gut
- Chyme entering duodenum
- Gastroenteric reflex initiated by distension
30
What is the "law of the gut"? What mediates it?
- Distention in the alimentary canal causes distal parts of the canal to relax and proximal parts to contract (circular muscle)
- Mediated by ENS
31
Hormonal control of peristalsis: Enhanced by...? (3)
- Gastrin
- CCK
- Serotonin
32
Hormonal control of peristalsis: Inhibited by...? (3)
- Secretin
- Peptide YY
- Epinephrine
33
Requirements for chyme entering the duodenum? (3)
- Food particles must be very small
- Small volumes of low pH fluid
- Gradual release
34
What is the major organ that regulates the rate of gastric emptying?
Duodenum
35
Nervous control that can inhibit gastric emptying? (2)
- SNS: level of spinal cord
- ENS: submucosal and myenteric plexuses
36
What will nervous control inhibit gastric emptying in response too? (4)
- Change osmolarity in duod.
- Decrease pH in duod.
- Distention/irritation of duod.
- Breakdown products of proteins/FAs
37
Substances that elicit CCK release?
Fats > peptides > carbs
38
What is likely the major paracrine regulator of gastric emptying?
CCK
39
Substances that elicit secretin release?
low pH > fats, capsaicin, bile acids
40
What kind of impact does secretin have on gastric emptying?
Mild impact
41
What major hormone performs the role of "ileal brake"?
Peptide YY
42
Substances that elicit peptide YY release?
Fats > carbs, amino acids
43
What does Peptide YY do if undigested foods are reaching the distal small intestine?
Slows everything down
44
The ileocecal valve protrudes into the _____ of the cecum
lumen
45
The ileocecal valve is forcefully ____ when excess ______ builds up in the cecum
Closed; pressure
46
What supplies a watery vehicle for absorption of substances from chyme as it comes in contact with villi?
Intestinal digestive juices by enterocytes
47
Glands found proximal to Sphincter of Oddi?
Brunner's glands
48
What do Brunner's glands secrete? What is it in response to?
Mucous in response to:
- Tactile/irritating stimuli
- Vagal stimulation
- GI hormones (secretin)
49
Function of Brunner's glands?
Protect duodenal wall from digestion of gastric juices
50
What inhibits Brunner's glands?
Sympathetic stimulation
51
_____ and ______ chemically digest macromolecules in the chyme?
Bile and Pancreatic enzymes
52
What does bile digest/do?
Emulsification of lipids
53
What do pancreatic enzymes do?
Hydrolysis of fats, proteins, carbs into smaller molecules
54
Bile is secreted by the liver by what ducts? What do they join to form?
Right and left hepatic ducts => common bile duct
55
What regulates the secretion of bile into the duodenum?
Sphincter of Oddi
56
If the Sphincter of Oddi is closed, where is bile stored?
Gall Bladder
57
The main pancreatic duct meets the common bile duct where?
Ampulla of Vater
58
Digestive enzymes of the pancreas: protein digestion? (4)
- Trypsin
- Chymotrypsin
- Elastase
- Carboxypeptidase
59
Digestive enzymes of the pancreas: carb digestion?
- Pancreatic amylase
60
Digestive enzymes of the pancreas: lipid digestion? (2)
- Pancreatic lipase/co-lipase
- Phospholipase A2
61
What enzyme is contained in saliva? What is it secreted from?
Ptyalin (salivary amylase) - secreted by parotid gland
62
What does ptyalin hydrolyze? What blocks its activity?
- Hydrolyzes starch
- Inhibited by acid of gastric secretions
63
Most important for digestion of starches?
Pancreatic amylase
64
3 major enzymes of the brush border? What do they digest?
- Lactase, Maltase, Sucrase
- Digest major disaccharides
65
Monosaccharides can be absorbed via what? (2)
- Facilitated diffusion
- Co-transport via Na+ gradient
66
Digestion of proteins in the mouth?
Only mechanical, no enzymatic digestion
67
Digestion of proteins in the stomach? (2)
- HCL: denatures proteins
- Pepsin: begins process of digestion (can digest collagen)
68
Where does most of protein digestion occur?
Duodenum and upper jejunum
69
When proteins/peptides enter the small intestine, what enzymes attack them? (4)
- Trypsin
- Chymotrypsin
- Carboxypeptidase
- Proelastase
70
What activates trypsinogen? => trypsin ?
Enterokinase (brush border enzyme) in the lumen
71
What zymogens can trypsin activate? (4)
- Chymotrypsin
- Pro-elastase
- Pro-carboxypeptidase
- Pro-phospholipase A2
72
What does trypsin do after food "runs out"?
Digests pancreatic hormones
73
Membrane-bound peptidases that aid in digestion of large peptides to di- and tri-peptides?
Brush border peptidases
74
33% of absorption is ____ and 67% is ______
Free amino acids; peptides
75
Amino acid absorption? (2)
Active transport or secondary transport with Na+
76
Dipeptide or tripeptide absorption? (3)
- Some Na+ dependent
- Some secondary transport with H+
- Within cytoplasm of enterocyte, most are hydrolyzed to FAAs
77
Why does digestion of fat present a problem?
Not water soluble so tends to accumulate in large droplets = reduced SA
78
Solution to challenge of fat digestion?
Emulsify fat droplet into small droplets with amphipathic outer molecule = micelle
79
Amphipathic molecules in bile that help form micelles? (3)
- Lecithins
- Bile salts
- Cholesterol
80
Once micelles have been formed, ________ can act on the triglycerides in “interior” of the micelle
Pancreatic lipase
81
What does pancreatic lipase need to help it insert into the micelle and activate it?
Co-lipase
82
What does pancreatic lipase break triglycerides into?
2 FFAs and 2 monoacyl glycerols
83
What happens to lipids after they have been chemically digested and absorbed into the enterocyte?
They’re reassembled into triglycerides and other lipids and inserted into chylomicrons
84
Where are chylomicrons built and secreted into?
- Built: enterocyte
- Secreted: Lymphatic vessels
85
What do the proteins on the outside of the chylomicron help it with?
Helps it be delivered to and used by cells throughout body
86
Carbohydrates and amino acids are transported across the __________ of the enterocyte, and diffuse into the capillary loops within the _______
Basement membrane; villus
87
Small free fatty acids can diffuse into the blood and be carried by ________
Serum proteins
88
Chylomicrons are secreted via ______ into the lamina propria
Exocytosis
89
What can malabsorption result in? (3)
- Diarrhea
- Micronutrient deficiency
- Macronutrient deficiency
90
Types of malabsorption can be pathophysiologically organized into four major problems...?
- Disturbances in intra- luminal digestion
- Disturbances in terminal digestion
- Disturbances in trans-epithelial transport
- Disturbances in lymphatic transport
91
Celiac disease:
- Intra-luminal digestion?
- Terminal digestion?
- Trans-epithelial transport?
- No
- Yes
- Yes
92
Chronic pancreatitis:
- Intra-luminal digestion?
- Terminal digestion?
- Trans-epithelial transport?
- Yes
- No
- No
93
Lactose Intolerance:
- Intra-luminal digestion?
- Terminal digestion?
- Trans-epithelial transport?
- No
- Yes
- No
94
Gastroenteritis:
- Intra-luminal digestion?
- Terminal digestion?
- Trans-epithelial transport?
- No
- Yes
- Yes
