1
Q
Identify the different parts of the gastrointestinal (GI) tract
A
- esophagus
- gallbladder
- liver
- stomach
- pancreas
- small intestine
- large intestine
- rectum
- anus
2
Q
What is the function of the capillaries in the GI tract?
A
- transport absorbed nutrients to the liver via hepatic portal vein
3
Q
How are absorbed nutrients transported from the GI tract?
A
- absorbed nutrients are transported through a network of capillaries via the hepatic portal vein to the liver
- libids are absorbed in lacteals and lymphatic vessels
4
Q
What is peristalsis?
A
- it is a reflex controlled contraction-relaxation giving a one directional flow for food
5
Q
What is segmentation?
A
- it is contraction-relaxation of non-adjacent sections, which moves food back and forth in 2 directions, mixing it with digestive juices
6
Q
What is the “food bolus” shown in the diagram for peristalsis?
A
- food bolus is the mass of chewed food mixed with saliva that travels down the esophagus into the stomach
7
Q
What is the role of the esophageal sphincter in the process of peristalsis?
A
The esophageal sphincter will relax to allow the food bolus to pass from the esophagus into the stomach
8
Q
What is a sphincter?
A
- A sphincter is a ring of muscle that acts as a valve to control the flow of materials in the digestive tract
9
Q
What is the location and function of the esophageal sphincter?
A
- located at the junction between the esophagus and the stomach
- it prevent backflow of stomach contents into the esophageal
10
Q
Which sphincter is located at the end of the common bile duct, and what stimulates it to open?
A
- the oddi sphincter
- cholecystokinin stimulates the gallbladder during digestion which relaxes the sphincter, allowing bile to flow down the common bile duct and enter the duodenum
11
Q
Where is the pyloric sphincter, and what is it controlled by?
A
- the junction between the stomach and the first part of the small intestine
- it is controlled by the hormonal and nervous system
- it also prevents backflow of intestinal contents into the stomach
12
Q
Which sphincter is under voluntary control?
A
- the anal sphincter
13
Q
What is the role of the mucous neck cells in the stomach?
A
- mucous cells secrete mucous
14
Q
What do parietal cells secrete?
A
- parietal cells mostly secrete HCL
15
Q
What substance do chief cells produce?
A
- chief cells secrete pepsinogen (inactive version of pepsin)
16
Q
Which part of the small intestine is connected to the stomach?
A
- The duodenum is the part of the small intestine that is connected to the pylorus of the stomach
17
Q
What are the three sections of the small intestine?
A
- duodenum
- jejunum
- ileum
18
Q
Where does most digestion and absorption occur?
A
- in th small intestine
19
Q
What are the primary functions of the villi and microvilli
A
- together they increase the surface area of the small intestine to promote absorption
20
Q
What is another name for microvilli?
A
brush border
21
Q
What are the six segments of the large intestine mentioned in the provided document?
A
- the descending colon
- the transverse colon
- the sigmoid colon
- the ascending colon
- the rectum
- the anal canal
22
Q
What is the main function of the large intestine (colon)?
A
- absorbs water, sodium, chloride, potassium and vitamin k
- allows bacteria to ferment food residue
- stores feces
23
Q
What does bacteria do within the small intestine?
A
- bacteria digest small amounts of fibre
- sunthezise vitamin K and biotin that are absorbed
24
Q
What is the secretion from the salivary glands and what is its action?
A
- Secretion: saliva
- Action: breaks down CHOs
25
What is the function of gastric juice, and which organ secretes it?
- gastric glands secrete gastic juices
- it mixes with food bolus, its HCL and enzymes degrade proteins
26
What is the role of pancreatic juice?
- pancreatic juices, which are secreted by the pancreas and target the small intestine, contain bicarbonate to neutralize acidic gastric juices and enzymes that degrade CHOs, lipids and proteins.
27
Where is bile stored and what is its function?
- The bile secreted by the liver is stored in the gallbladder
- When needed, it is released into the small intestine to emulsify lipids, facilitating their breakdown by enzymes
28
What is the general name for enzymes that hydrolyze proteins?
- The general name is proteases
29
The gallbladder secretes what and what does it cause
- it secretes bile to the small intestine, where it emulsifies lipid to facilitate breakdown by enzymes
30
Describe the pathway for carbohydrate digestion and absorption, from the mouth to the large intestine.
- Digestion begins in the mouth, where salivary amylase breaks down starches into simple disaccharides
- little digestion occurs in the stomach because salivary amylase is deactivated by the low pH
- Digestion continues into the small intestine, where pancreatic amylase continues CHO hydrolysis to give dextrins
- the enzymes on the brush border (maltose, lactose, and sucrose), in the final stage of digestion, break down into monosaccharides
- glucose and galactose are absorbed by Na+ dependent carrier transport
- Fructose is aborbed by a much slower diffusion
- the monosacharrides are secreted into capillaries and drain into the hepatic portal vein andd to liver
- water insoluble fibers and undigested CHO are acted on bacteria in colon
31
Describe the digestion and absorption pathway for lipids.
- digestion of lipids begins in the mouth with lingual lipase which mainly acts on short and medium chain saturated FAs
- digestion continues in the stomach with lingual lipase and gastric lipase on some saturated FAs
- High lipid content can stimulate the release of gastric inhibitory peptide (GIP) and secretin which slows gastric motility
- The majority of lipid digestion occurs in small intestine where bile from the gallbladder will mix with chyme and emulsify the fats, to facillitate their breakdown
- pancreatic lipase is the main enzyme which digests long FAs chain. this process hydrolyzes tryglycerides into monoglycerides and FFAs
- short and medium chain FAs are absorbed into the hepatic portal vein bound by albumin and travel to the liver for energy
- long chin FA's are absprbed in epithelial cells and are reformed into TAGs
- TAGs are transported by chylomicrons via the lacteals and lymphatic system, which then drain into large veins via the thoracic duct and the right lymphatic duct
32
What is action of lipoprotein lipases?
- They hydrolyze TAG to give FFA and glycerol for peripheral tissues
33
Describe the digestion and absorption pathway for proteins.
- protein digestion begins in the stomach with pepsin from a precursor pepsinogen which is produces chief cells to digest short chain polypeptides
- gastrin stimulates parietal cells to secrete HCL which activates pepsin
- in the duodenum the high pH inactivates pepsin
- trypsin, a precursor of trypsinoegen from the pancreas hydrolyzes di, tri and single polypeptides and amino acid
- free amino acids are absorbed by Na+ coupled active transport
- di and tri polypeptides are absorbed by a carrier using H+ gradient
- amino acids reach the liver via hepatic portal system
34
What happens to amino acids once they reach the liver
- conversion to glucose from glucogenic amino acids
- conversion to lips from ketongenic amino acids
- direct release into blood stream as plasma proteins such as albumin or FAA
35
What happens when gastrin stimulates secretion of HCL
- activates pepsin
- improves calcium and iron absorption
- kills pathogenic organisms
- inactivates hormone of plant and animal origin
- denatures food proteins
36
What are the 4 hormones that control digestions
- gastrin
- gastric inhibitory peptide
- secretin
- cholecystokinin
37
What is the origin, secretion stimulus, and action of the hormone GIP (Gastric Inhibitory Peptide)?
Origin: Duodenum, jejunum.
Secretion Stimulus: Lipids; proteins.
Action: Inhibits the secretion of stomach acid and enzymes; slows gastric emptying
38
What is the origin, secretion stimulus, and action of the hormone CCK (Cholecystokinin)?
Origin: Duodenum, jejunum.
Secretion Stimulus: Lipids and proteins in the duodenum.
Action: Contraction of the gallbladder and flow of bile to the duodenum; causes secretion of enzyme-rich pancreatic juice and bicarbonate-rich pancreatic fluid; slows gastric emptying.
39
What is the origin, secretion stimulus, and action of the hormone Secretin?
Origin: Duodenum, jejunum.
Secretion Stimulus: acidic chyme and peptones
Action: secretes bicarbonate-rich pancreatic fluid to neutralize stomach acid, making the duodenum more neutral, and it slows down gastric emptying
40
How are most vitamins absorbed in the body?
- mainly by passive diffusion in the dudoneum and jejenum
41
How is Vitamin B12 specifically absorbed?
- Vitamin B12 binds with an intrinsic factor secreted by the stomach, and then SI absorbs IF-B12 complex via endocytosis
- once absorbed chylomicrons and lipoproteins transport these insoluble fat bitamins for the liver and fatty tissues
42
What are some of the factors that can affect the absorption of minerals in the body?
- bioavailability = amount ingested reaches systemic circulation
- transit time from dietary source to absorption site
- quantity of digestive juices
- pH of the intestinal lumen contents
43
What percentage of ingested calcium is typically absorbed, and how does this differ between males and females?
- The body absorbs 35% of ingested calcium
- Males absorb more than women
44
What much % of Mg does the body absorb
- 20-30%
45
How are metallic minerals absorbed in the body?
- with specific or general carriers
- they can also be combined with other proteins such as albumin
46
What are the common pathways for mineral excretion?
- feces
- sweat
- urine
47
What is the total estimated daily volume of water that enters the gastrointestinal (GI) tract?
- about 9000 ml/day of fluid enters the GI
48
What percentage of the total water entering the GI tract is absorbed by the small intestine and the large intestine?
- 72% of water is absorbed by the proximal part of the small intestine
- 20% of water is absorbed by the distal part of the small intestine
- 8% of water
49
How much water is contributed to the GI tract daily from oral intake versus from secretions by organs like the salivary glands, stomach, and pancreas?
- salivary glands: 1500 ml
- oral intake: 2000 ml
- stomach: 2000 ml
- bile: 500 ml
- pancreas: 1500 ml
- intestine: 1500 ml
50
What is diverticula
- small dark sphere bulging out in the colon
51
What is diverticulosis?
- inflammation and infection
52
What are the key characteristics of Irritable Bowel Syndrome (IBS)
- bloating, diarrhea, constipation may persist, and chronic abdominal pain, discomfort
53
What are some disorders of the GI tract
- diverticulosis
- diverticula
- Irritable bowel syndrome (IBS)
- functional dyspepsia
BPK 312
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