GI phys day 1 Flashcards
How many sphincters are in the GI tract
6 plus the sphincter of oddi
How many layers in the GI tract
4
Mucosa (internal lining)
Submucosa (houses BV and nerves)
Muscularis propria (Thickest layer, 2 large layers of muscle)
Serosa ( Mesothelium)
Which layer of the GI tract is most external
serosa (mesothelium)
Which layer of the GI tract is the internal lining of the epithelial membrane
Mucosa
Which layer of the GI tract houses Blood Vessils and nerves
Submucosa
Which layer of the GI tract is the thickest layer, with 2 large layers of muscle?
Muscularis propria
What are the 2 blood supplies of the digestive tract
- Splanchnic circulation (IVC, celiac artery, superior mesenteric artery, portal vein, inferior mesenteric artery)
- Hepatic portal circulation (a portion of the splanchnic circulation, the part between the GI tract and liver)
What does the Hepatic portal circulation lie between
The GI tract and liver
What are the 2 functions of the splanchnic circulation
Feed GI tract cells (nutrients, drop off O2)
Absorb nutrients (put in blood stream)
What are the 2 capillary beds in the Hepatic portal circulation
- In the small intestine, the hepatic portal circulation supplies O2 to small intestine and picks up absorbed nutrients
- In the Liver, the system drops off absorbed nutrients, drains into hepatic veins
Via which artery does oxygenated blood get to the liver
The Hepatic artery
Which nerve allows the enteric nervous system to operate
Vagus nerve
Via which nervous system is the gi tract controlled
Enteric NS
What are the main functions of the enteric NS
- Coordinate activity of the digestive tract
- Make sure food moves at the same pace throughout
Describe the Villi, Microvilli, Capillaries in the GI tract
Villi: Finger-like projections, larger ridges that you can see without a microscope
Microvilli: On top of the villi- hair-like projections that make up the brush boarder in small intestine. Give increased surface area to put enzymes on
Capillaries: Absorb nutrients
What projections make up the brush-boarder in the small intestine
Microvilli
Describe Lacteals, Goblet Cells, and Intestinal Crypt
Lacteals: Lymphatic system, absorb lipids
Goblet cells: Mucus-producing cells
Intestinal crypt: Holes (stem cells inside)
What types of cells are inside of the intestinal crypt
Stem cells
Which nerves provide parasympathetic activation to the Sailvary glands
Facial (7) and Glosopharyngeal (9)
4 Contents of Salivary gland
- Amylase (breakdown carbs)
- IgA/lysozyme: Destrory bacteria
- Mucins (turns into mucus)
- Bicarbonate (alkaline)
What is the secretion and function of Parietal cells
Secrete: HCL
Fx: protein degredation, activate pepsinogin, Vitamin absorbtion
What is the secretion and function of chief cells
Secrete: Pepsinogin
Fx: Protein digestion
What is the secretion and function of ECL cells
Secrete: Histamine
Fx: Stimulate parietal cells
What is the function of Mucous neck cells
Stem cells of stomach, replace surface mucous cells
Surface mucous cells function
lining of stomach
G cells secrete what
Gastrin
Where are G cells found
Antrum
3 Primary stimuli of Gastric secretions
- Gastrin release into bloodstream
- Histamine
- AcH from enteric nerve endings
What is gastrin released in response to
Protein in the digestive tract
What cells does gastrin stimulate
Parietal cells, chief cells, ECL cells
Why are Parietal cells packed with mitochondria?
Their receptors have active channels, so they have to pump out HCl and need ATP to drive the active transport of H+
What 3 binding receptors do parietal cells have
AcH (M3), Histamine(H2), Gastrin (CCK-B)
Where does the small intestine start
Duodenum
Where do bile and pancreatic juices dump
Duodenum
What is the exocrine function of the pancreas
Produce enzymes to produce micronutrients
What is the organ that is the bile resivoir
Gallbladder
Which cells secrete pancreatic juice
Acini cells secrete pancreatic juice into ducts that lead to duodenum
What is the pH of pancreatic juice
PH= 8 to counteract low pH of stomach (bicarbonate ions)
Describe the digestive enzymes in the pancreas
Digestive enzymes that are mostly inactive forms, that then become active in the lumen
Are digestive enzymes active or inactive in the pancreas
mostly inactive (if active, they would eat the bile duct).
They activate in the lumen
Where do digestive enzymes from the pancreas activate
in the lumen
What can acute pancreatitis be caused by in relation to digestive enzymes
If there is pre mature activation of phospholipase A2, this destroys cell membranes because of the activation of the digestive enzymes
What are the 2 stimulants of acini cells to secrete pancreatic juice?
Secretin–> Secretes HCO3 (bicarbonate) rich juice
CCK–> Secretes enzyme rich juice
Where is bile made
in the liver
Bile is connected to the absorbtion of which nutrient
lipids
What are the 2 key components of bile acids
cholic acid, chenodeoxycholic acid
What are the structures of cholic acid and chenodeoxycholic acids, and what do they form?
Structure: Amphipathic ( have a polar and nonpolar side
Form: micelles (transport lipids in GI tract)
What are the 2 bile pigments
- Bilirubin
- Biliverdin
What do the 2 bile pigments come from
they are broken down hemoglobin (make bile yellow)
Is biliary secretion acidic or alialine
Alkaline- increases pH
Endocrine vs paracrine
Endocrine: Released in blood and go through body
Paracrine: Local effects in the blood
Water absorbtion is dependent on which ion absorbtion
Na
Na is absorbed via
- Secondary active transport with glucose
- Exchange with H
- Coupled with Cl
- Epithelial Na channels (ENaC)
Reduction of absorbtion of which ion and Increased secretion of which ion is caused by Cholera
Na absorbtion (reduces NaCl absorbtion)
Increased Cl secretion
What disorder results in a hyperosmotic lumen
Cholera
Food poisioning does what in the lumen
Cause increased solute concentrations in the lumen, which draws water in and results in Diarrhea
Diarrhea results in which K dysfunction
Hypokalemia- K secretion in the colon
Constipation results from which nutriant imbalance and what fixes this?
Fiber deficiency (Fiber is a solute in the lumen)
Treated with Mg sulfates (increase osmotic pressure in lumen, pull water in)
What are the 6 processes of the GI tract
Ingestion
Digestion
Absorption
Secretion
Propulsion
Defacation
Which enzyme breaks down carbohydrates in the mouth
Salivary amylase
Which enzyme breaks down carbohydrates in the small intestine
Pancreatic amylases
Which enzymes are bound to microvilli to break down carbohydrates
Brush border enzymes Sucrase, lactase, isomaltase (break down carbs to monosaccharides)
what are carbohydrates absorbed as
Glucose and galactose
- Absorbed through intestinal cells into blood via cotransport with Na
How do carbohydrates leave the intestinal cells to get into the blood
GLUT 2 channels (get glucose out of the cell and into blood vessils)
What channels facilitate the diffusion of fructose
GLUT 5(go into cell), GLUT 2(go from cell to blood)
Where does protein digestion begin
In the stomach
How is pepsionogen converted into pepsin
Via low pH– helps proteins unfold, doesn’t break the bonds directly
Why does pepsinogen stop cleaving peptide bonds in small intestine
there is a higher pH so pepsinogen is not converted to pepsin
Describe the activation of trypsinogen
Enterokinase (brush border) activates trypsionogen to become trypsin, trypsin activates all others
What does trypsinogen do to proteins
creates some amino acids, but mostly small peptide chains
What do brush border proteolytic enzymes break down proteins into
dipeptides, tripeptides, or amino acids
Describe the 7 different mechanisms of amino acid transport
- 5 require Na co-transport (use Na gradient)
- 2 are independent of Na
Dipeptides and Tripeptides are transported via which transporter. What kind of transport is this?
Pep T1 (uses H cotransport)
Where are proteins broken down into individual amino acids
inside of intestinal cells
What emulsify’s fat
Bile acids (sourround them and seperate them from others)
Which side (polar or nonpolar) faces out on micelles
Polar side faces out to get to the brush border enzymes (Transports lipids through GI tract)
After micelles deliver fatty acids and monoglicerides to intestinal cells, describe the fate of lipid digestion
- Lipids sourround by protein to form chylomicrons
- Chylomicrons released into lacteals (dumped into venous system)
- Lacteals go to liver and are converted to LDL, HDL, etc
What is the primary cause of steatorrhea
pancreatic lipase deficiency
Secondary: Too much alkaline secretion, too much acid secretion in stomach (enzyme doesn’t work if the pH is too low), defective reabsorbtion of bile in ilium (if PH too low, cant activate lipases)
Describe the 3 causes of malabsorption
1.Short gut syndrome (50% of gut is removed, lack absorbtion of nutrients)
2. Absorption of vitamins is impaired
3. Celiac disease
Celiac disease pathology
Autoimmune defense against gluten –> inflammation–> loss of cilia and flattened villi–> malabsorption
What are SCFAs and where are they
Short chain fatty acids ( 2-5 carbon weak acids), found in the colon.
Where are SCFAs produced and absorbed
the colon– formed by bacteria via breakdown of fiber
What is the benifit of fiber in relation to the colon
fiber increases the production of SCFAs, which has an anti-inflammatory effect overall
Describe diatary iron and absorbtion
Most is ferrous (Fe3) but needs to be Ferric (Fe2) to be absorbed (Brush boarder enzyme does the conversion to get it into the blood)
What is iron bound to in the blood
carried in blood bound to the transferrin protein
Where are most vitamins absorbed
the duodenum
What does B12 require the release of for absorbtion and where is it absorbed
requries the release of intrensic factor in the duodenum by parietal cells, it is absorbed in the ilium
Which vitamins are Na independent
B12 and folate (other 7 are water soluble that absorb with Na cotransport)
Which vitamins are fat-soluble
A, D, E, K (require bile for absorbtion)
( Always disown every kid )
(Dont come at me for my mnumonic i hate kids and now i can remember which vitamins are fat soluble )
What is Cobalt essential for
Cobalt is a component of B12
Megaloblastic anemia occurs when we have a deficiency in B12/Cobalt/Folate
