Lecture 17/18: The Gastrointestinal System Flashcards
(36 cards)
1
Q
What are the main components of the Gastrointestinal Tract and the order they come in?
A
- Oral cavity
- upper esophogeal sphincter
- Esophagus
- lower esophogeal sphincter
- Stomach
- pyloric sphincter
- Small intestine
- ileocecal valve
- Colon (Large intestine)
- anal sphincter
- Rectum
- are main comp and - are the sphincters making sure insides only flow one way
2
Q
What is the Gastrointestinal Tract?
A
- large surface area of body exposed to external environment (ie what comes into body)
- detects food and potentially toxic substances
- sense to expel vomit and diarrhea
- specialized populations of T cells localized to the intestinal mucosa ex: peyer’s patches, mesenteric lymph nodes * specifically help to protect against what exposed to
3
Q
What are unique properties of the GI tract
A
- 28 ft long (extensively folded
- large surface area due to micro villi/villi
- food spends 30-80 hours in tract
- has residence gut microbiome (bacteria) and protects against pathogenic microbes that enter tract
- has own intrinsic nervous system
4
Q
What are the 4 basic processes of the of the GI?
A
- Motility
- Digestion
- Absorption (water & nutrients)
- secretion (salica/mucous, antibodies (IgA), digestive enzymes, bile, bicarbonate)
5
Q
What is the Cephalic Phase of Digestion?
A
- chemical and mechanical digestion beginning in mouth
- chewing (mastication)
- Salivary secretion is under autonomic control (stim by SNS and PNS) which lubricates food and provides enzymes liek amylase and some lipase
6
Q
Does protein digestion begin in the cephalic phase of digestion
A
- no (think don’t want muscles in mouth to break down, only in things with barrier)
- amylases breaks down carbs and some lipids broken down by lipase
7
Q
What is the Gastric Phase of Digestion?
A
- secretory cells of gastric mucosa
- digestion of proteins and fat
- carbs not broken down (amylase is pH sensitive)
- pepsin and gastric lipase secreted
- secretion stimulated by acetylcholine (PNS regulates this think its in charge of resting things)
8
Q
What is the small intestine phase of digestion?
A
- where most digestion takes place
- enzymes released are primarily secreted by pancreas
- enzymes that break down protein are released in inactive form ( Zymogen) prevents autodigestion
- inactive enzymes are activated by trypsinogen (note ogen= not yet activated)
- trypsinogen activated by enterokinase in brush border of duodenum
9
Q
What are the components of small intestine?
A
- top- bottom
- duodenum
- jejunum
- lleum
- gall bladder, liver, pancreas and stomach sit above
- relseases inactive: carboxypeptidase, chymotrypsin(ogen), lipase, amylase
10
Q
What structures are associated with pancreas?
A
- gall bladder: stores bile
- liver: produces bile
11
Q
What helps promote absorption of nutrients?
A
lined villi on small intestine (increased surface area)
12
Q
How are glucose and galactose absorbed?
A
- active transport
- transporter: SGLUT1
- **requires sodium to move across (co-transport)
- would not see in muscle (GLUT1 in muscle)
13
Q
How is fructose absorbed?
A
- facilitated transport
- transporter: GLUT5
- wont be found in skeletal muscle or in adipose
14
Q
What is maltose?
A
2 glucose
15
Q
What is sucrose?
A
1 fructose and one glucose
16
Q
What is lactose?
A
galactose and glucose
17
Q
What is starch?
A
glucose, glucose, glucose….
18
Q
Why is sodium in sports drinks
A
- promote glucose uptake (drink should be about 6-8% glucose)
- required to provide energy
- water follows sodium, fluid absorption will also be improved
- drink designed for recovery not during excersise
19
Q
What happens if an individual has a deficiency in lactase?
A
causes lactose intolerance
20
Q
What happens if fructose is added to sports drinks
A
- now 2 transport systems
- more glucose uptake
- also have to consider that glucose will make water go back into intestine (dehyrate you)
21
Q
How are peptides and amino acids transported?
A
- amino acids cotransported with sodium
- di and tri peptides cotransported with H+
- small peptides carried intact across cell by transcytosis
- mostly amino acids absorbed
- intact proteins are not absorbed (would cause immune reaction, food allergy), may happen in cases of intestinal damage causing “leakiness”
22
Q
How do amino acid/protein supplements work?
A
- aa absorption requires transport (saturable process)
- amino acids go directly to liver, broken down and even transformed to other amino acids
23
Q
What is the maximum effective dose of protein?
A
25g (maybe 2x higher in older individuals)
24
Q
What does leucine do?
A
- ingestion of 5g+ of leucine has stimulatory effect on protein synthesis
- this is what you want
25
How is fat emulsified?
Made soluble with bile:
- fat molecule in aqueous environment
- bile salts are amiphipathic (like soap or detergent both hydro and lipophilic)
- mechanically "busts up" fat globule
Brokendown by lipase:
- fat has triglycerides (3FA on glycerol backbone
- lipase from pancreas breaks down triglyceride
- broken down into fatty acids,
- arrange themselves into micelles, with polar ends facing out.
26
How are fats absorbed and transported?
- absorbed as fatty acids and monoglycerides
- in intestinal cell gets reassembled into triglycerides and packed as chylomicrons (lipoprotein)
- chylomicrons too large to cross capillary wall, must be absorbed into lymphatic system
- enters circulation via thoracic duct near heart
27
How is appetite regulated?
- secondary neurons and primary neurons
- stimulatory arm and inhibitory arm (primary neurons)
- G hrelin stim appetite
- PYY inhibits appetite
- insulin: inhibits appetite
- leptin: inhibits appetite
28
How is dopamine related to appetite?
- dopamine linked to appetite
| - hedonic (pleasure) eating
29
What is gastric bypass surgery?
- Roux-en Y procedure: a small pouch is created in upper stomach attached directly to small intestine, bypass most of stomach and duodenum
- 40-50% weight loss within year of surgery
hormonal changes:
- increased PYY levels: dec appetite
- dec ghrelin levels (dec appetite)
- increased incretin levels postprandially (improves insulin secretion)
- can get incretin increased by diabetes drugs
30
What is Gut Microflora?
- 10x as many microbes as human cells in the body
- assist with digestion: contain enzymes not present to add to supply
- assist with immune function
- synthesis of folate, B12 and K
- promote intestinal growth and differentiation of mucosals
- GI health is a balance between beneficial and harmful bacteria (bifidobacteria and lactobacillus (probiotics))
31
How does gut microflora contribute to obesity
- inc levels bacteriodetes in lean
- inc levels of firmicutes in obese (promote breakdown and absorption of patty acids and polysaccharides)
- directly transferring "obese" microbiota into lean mice causes obesity
- co-housing ob mice with lean mice (with leam type microbiota) prevents weight gain due to exchange of fecal microbes
- lean mice not colonized by obese micrboes
32
What is CCK
cholecystokinin
- released by duodenum
- when fat is sensed, sends feed back system to gall bladder to contract (bile then goes to small intestine)
33
What is G hrelin
- stimulates app
- released by stomach
- stimulated by empty stomach
34
What is PYY?
- inhibits app
- source: intestine
- simulated by bile, chyme, nutrients
35
What is Leptin
- inhibits appetite
- source: adipose
- stimulated by inc in adipose mass
36
What is Insulin (in relation to appetite)
- inhibits appetite
- source: pancreas
- stimulated by inc blood glucose
