GI- intestines Flashcards
(100 cards)
1
Q
what are the 3 divisions of the small intestine?
A
duodenum, jejunum, ileum
2
Q
what are the 4 regions of the large intestine?
A
caecum, colon, rectum and anal canal
3
Q
intestinal blood supply
A
inferior and superior mesenteric arteries w/ many anastomoses
4
Q
venous drainage of the intestines
A
superior mesenteric and inferior mesenteric to splenic vein; all eventually draining into hepatic portal vein
5
Q
what does the superior mesenteric artery drain?
A
the small intestine and proximal 2 thirds of the large intestine
6
Q
what does the inferior mesenteric artery drain?
A
distal 1/3 of the large intestine
7
Q
what are the alterations in the small intestine?
A
plicae circularis, villi, microvilli
8
Q
plicae circularis
A
intense foldings of the mucosa to increase SA for absorption and digestion
9
Q
villi
A
- small fingerlike projections on the mucosal surface of the small intestines that increase surface area
- has a blood supply for nutrient exchange and transport
- has a lacteal
10
Q
lacteal
A
modified lymphatic vessel in villi allowing nutrient absorption (large molecules); GI tract lymphatic fluid dumps into the left subclavian vein
11
Q
microvilli (brush border)
A
- projections that increase the surface area of apical surface area of absorptive cells
- contain enzymes for carbohydrate and protein digestion
12
Q
duodenum features
A
- most dense pilcae circularies (lots of enzyme secretion)
- major sote of Ca2+ and Fe absorption
- Brenner’s gland and hepatopancreatic ampulla
13
Q
Brunner’s gland
A
secretes bicarb. rich mucous to protect duodenum from acidic chyme
14
Q
hepatopancreatic ampulla
A
receive liver and pancreatic duct secretions rich in bicarbonate
15
Q
jejunum features
A
- 40% length of small intestine
- mostly absorbs glucose, a.a.’s and water
16
Q
ileum features
A
- lumen shrinks in size as nutrients are being absorbed
- plicae circularis taper out
- abundant lymphoid nodules (MALT) - Payer’s patches in submucosa
- vitamin B12 absorbed here
17
Q
gastroileal reflex
A
long reflex from stomach that jumps to distal portion; peristalsis to clear out residual matter into large intestine and keep bacterial count down
18
Q
ileocaecal valve
A
sphincter muscle situated at the junction of the small intestine (ileum) and the large intestine; inefficient and requires immune complex
19
Q
cephalic and gastric phase (intestinal digestion)
A
- vagal nerve stimulation causing release of pancreatic juice
- neural; parasympathetic nervous system stimulation
20
Q
what happens when chyme enters the duodenum?
A
enteroendocrine cells release secretin and CCK to enter the bloodstream
21
Q
upon reaching the pancreas, secretin and CCK secrete:
A
bicarb. rich juice and enzyme rich juice, respectively
22
Q
patterns of intestinal contraction
A
fed and fasting patterns
23
Q
fed pattern
A
during feeding, irregular contractions mix contents w/ digestive juices (segmentation)
24
Q
fasting pattern
A
migrating motor complex (peristalsis) begins at duodenum and propels residual material into colon
25
pancreatic proteases
- secreted as inactive enzymes to protect pancreas from autodigestion ('pro' or 'gen')
- trypsin is key to activating these proteases
- trypsinogen is activated by membrane-bound enteropeptidase (brush border enzyme)
26
steps of fat digestion
- fat globules emulsified by bile salts
- lipases break fat down into monoglycerides and FFAs and associate w/ bile salts to form micelles
- they then recombine and package w/ protein (chylomicron)
- undergo exocytosis to lacteals which are carried away by left thoracic duct to liver for processing
27
in what ways may nutrients be absorbed in the small intestine?
active transport, secondary transport (using one nutrient's chemical gradient to pull another nutrient in), facilitated diffusion, diffusion
28
how are fat soluble vitamins absorbed and what are they?
vitamins A, D, E, K absorbed by micelles
29
how are water soluble vitamins absorbed?
diffusion
30
how is glucose absorbed?
secondary active transport using Na+ [ ] gradient (2Na+/glucose); if glucose is high inside cell, goes to bloodstream to be processed by liver
31
how are amino acids absorbed?
secondary active transport w/ Na+ and simple diffusion on basolateral membrane; can also go to bloodstream
32
how are essential amino acids absorbed?
primary active transport (ATP)
33
how are short chain FAs absorbed?
simple diffusion across apical membrane
34
how are glycerol or long chain FAs absorbed?
first combine w/ bile salts to make micelles (active transport); repackage w/ chylomicrons to enter lacteals
35
water & electrolyte balance
intestines are responsible for fluid balance where lectrolytes are absorbed/reabsorbed in small and large intestine
- water via osmotic gradient
- Ca2+ and Fe2+ absorbed in duodenum, glucose and a.a. absorption are coupled w/ Na+ absorption
- lots of bicarb. ions reabsorbed in large intestines
36
what are alterations in the large intestines?
smoother mucosa, teniae coli, thinner circular muscle and haustra
37
teniae coli
three bands of longitudinal smooth muscle in muscularis
38
haustra
pouches that form in the large intestine when the longitudinal muscles are shorter than the colon; contractions are every 30 min
39
histology of the large intestine
mucosa, submucosa, muscularis and serosa; intestinal glands are covered by mucous cells that lubricate to ease passage of feces
40
colonic movement
slow (3-12/min) and contractions aid water reabsorption
41
gastrocolic reflex
increased peristalsis of the colon after food has entered the stomach
42
role of bacteria in the colon
aid digestion of complex starches and sugars present in dietary fiber, as well as synthesizinf vitamin K and some B vitamines
43
rectum and anal canal
20 and 2 cm respectively, anal columns have highly vascular longitudinal folds (dilation of vascular sinusoids = hemorrhoids), have voluntary and involuntary sphincters
44
defecation reflex
1. gastrocolic reflex stretches rectal wall to send afferent signal to spinal cord
2. parasympathetic reflex initiated at sacral level contract rectal wall, relax internal anal sphincter
3. defecation occurs by relaxing external anal sphincter (stretch info. from sigmoid colon shared in cortex - voluntary control)
45
Mechanical Digestion
- chewing within oral cavity
46
Chemical Digestion
- by enzymes or low pH
47
Where does chemical digestion begin?
begins in mouth with salivary amylase and continues in the stomach with HCL, pepsin and gastric lipase
48
Function of pepsin
breaks down proteins
49
function of gastric lipase
breaks down fats
50
Absorption
- absorbing nutrients of food stuff
51
Where does absorption occur?
entire length of small intestine and some of large intestine
52
Where can absorption go?
into blood stream (water soluble) or lymphatics (immune vessels)
53
Propulsion
occurs during entire length of the tube
| - swallowing or deglutition
54
Where does peristalsis begin?
in esophagus and goes throughout the tube
55
How do blood vessels, lymphatics and nerves travel to and from the majority of the small intestine?
by the mesentery
56
What do immune cells use to travel down lymph nodes?
lacteal
57
Absorptive cell
most abundant within the villi
58
Goblet cell
secrete mucus the entire length of the tube
- help protect stomach lining from burning from acid
- helps lubricate or ease passage of food
59
Enteroendocrine cells
release hormones and are at the base of the villi
60
Paneth cell
specialized epithelial cells that talk to immune cells
| - constantly sample stuff to see if immune response needs to be activated
61
Where is the major site of Ca and Fe absorption?
duodenum; only place this is done
62
What does duodenum mean?
means '12'- shortest
63
Where does brunners gland exist?
only within the first 10cm of 25cm of duodenum
64
Why do we not require brunners gland after 10cm?
accessory organs provide mucus
65
What does jujunum mean?
means empty; no residual matter here when people die
66
T: F- Pilicae circulares is not as dense as duodenum
true
67
What does ileum mean?
twisted
68
How much does the ileum occupy?
60% of small intestine (2m)
69
Function of Ileum
- absorbs fats
- most nutrients and vit b12 are absorbed here
- separates small and large intestine
- gastroileal reflex (pushing of food to large intestine)
- contains lymph nodules
70
CCK will
talk to talk to pancreas and liver tell them to release their enzymes to continue chemical digestion
- liver= bile to emulsify fats
- pancreas= plethora of enzymes
71
What detects the presence of food in the duodenum?
enteroendocrine cells because food is slightly acidic which will release CCK and secretin
72
Carbohydrates
- sugar breakdown begins with enzymes released from parotid gland
- amylase, lactase, maltase, sucrase
73
Proteins
- broken down by peptidases
- stomach releases pepsin
- pancrease release trypsin, chymotrypsin, and carboxypeptidase
74
Fats
- difficult to digest so they require bile salts
75
What are bile salts?
amphipathic molecules that help pull on the edges of fat globule and turn it into little droplets
76
Where do lipases come from?
Lingual (tongue), gastric (stomach), pancreatic (pancreas)
77
Nucleic acids
- nuclease, deoxy/ribonucleases to recycle nucleic acids
78
Where and how are enzymes release?
by pancreas found at brush border
79
What makes trypsin active?
enteropeptidase makes trypsinogen into trypsin
80
Fat soluble vitamins
A, D, E K- absorbed via micelles
81
Water soluble vitamins
C, by diffusion
82
Where are electrolytes absorbed and reabsorbed?
small intestine mostly with some large intestine
83
Where are Ca and Fe absorbed?
duodenum
84
Diarreha
not enough time in large intestine to absorb water and bicarb; less buffer
85
Constipation
fecal matter has too much time in large intestine; absorb too much bicarb and water and too much base in blood
86
Bristol- Separate hard lumps
very constipated
87
Bristol- lumpy and sausage like
slightly constipated
88
Bristol- sausage shape with cracks in surface and smooth, sausage like
normal
89
Bristol- soft blobs with clear cut edges
lacking fibre
90
Bristol- mushy consistency with ragged edges
inflammation
91
Bristol- liquid consistency with no solid pieces
inflammation
92
Where does large intestine begin?
ileocecal valve
93
Appendix
- important for ruminant animals that eat a lot of grass and cellulose
94
Hepatic flexure or right colic flexure
• Ascending colon goes up the right side and make a 90 degree turn under the liver
95
What is suspended by mesocolon?
transverse segment
96
splenic flexure or the left colic flexure
Descending colon makes 90 degree turn underneath the spleen
97
sigmoid colon
At distal end of large intestine, it takes an S turn
98
Rectum
is the last straight part of the tube and it will aid in defecation
99
Anus
has skeletal muscle around it for us to decide when it is appropriate to defecate
100
Measurement of rectum and anus
20cm for rectum; 2cm for anus
