Gastrointestinal Flashcards
Satiety center is located in ….., feeding center in ….. . The one usually active is ….. .
Destruction of the feeding center leads to …., while the satiety center …..
ventromedial nuclus, lateral hypothalamus
feeding center is usually active
anorexia
obesity syndrome
What are the hormones that cause the decrease of appetite?
- CCK: released from mucosa of upper intestine upon introduction of food in the small intestine
- Calcitonin: from thyroid gland.
Distension of the alimentary tract causes ……., whereas contraction …….
decrease of appetite, increases it
Warm environment …. appetite, while the cold …..
decrease, stimulates it
The lipostatic theory suggests …..
the presence of humoral response between fats in the body and the hypothalamus that inhibits the feeding center
* Leptin is released from the fat to inhibit hunger
The glucostatic theory suggests that …..
the increase in appetite is due to decrease in blood glucose detected by the satiety center
Thirst is controlled by the ……, while the decrease of ECF volume activates the ……. through cardiac and vascular baroreceptor. Volume stretching of stomach …… drinking
osmoreceptor in ant. hypothalamus (activated by increased osmotic pressure)
renin-angiotensin system
Decreases
Humans secrete about …… liter/day saliva, with pH ……,
pH increased with food to …..
1.5
7
8
What are the major salivary glands and what is their secretion??
- Submandibular: 70% of total (mixed, most serous)
- Parotid: 20% of total (serous)
- Sublingual: 5% of total (mixed, most mucous)
* 5% from minor glands
Von Ebner gland is ….., Blandin Nuhn & labial glands are …., and palatine/glossopharyngeal are …
serous, mixed, mucous
The saliva has two enzymes: ….. & ……., and their functions are ..?
- Ptyalin (alpha-amylase): initiates starch breakdown in the mouth. Found in serous secretions
- Lingual lipase: initiates fat break down into fatty acids and monoglycerides
* Lingual lipase is secreted by von ebner glands
Function of :
- Mucin
- Lysozyme
- Lactoferrin
- High proline proteins
- IgA
- Kallikrein
- lubrication
- breaks down bacterial cell wall
- binds iron and bacteriostatic
- protects enamel
- defensive against bacteria (opsonization)
- cleaves kiniogens to form bradykinin
Define bradykinin and state its function
works on blood vessels to release prostacyclin & nitric oxide causing vasodilation and lower blood pressure.
* ACE inhibitor inhibits bradykinin degradation, potentiating its effect of blood pressure
Sympathetic and parasympathetic innervation ….. salivation.
increases
- Sympathetic increases viscous saliva rich in (amylase, K, HCO3) via action on beta-adrenergic receptors
- Parasympathetic increases watery saliva via acetylcholine on muscarinic receptor, and via kallikrein (vasodilator)
Reflex innervation regulates salivation via ….
increase saliva secretion in response to visual, taste, smell etc…
Swallowing is triggered by …. & ….
IX & X
Describe the swallowing process
- mouth closed on bolus, mouth propels food towards pharynx
- involuntary contraction of pharynx to propel bolus. The glottis closes to prevent aspiration
- peristaltic movement of esophagus to move food to stomach
UES function is …
automatic relax upon swallowing, then automatic contraction behind the bolus, preventing reflux
LES is ….. sphincter, controlled by ….. . It ….. automatically upon swallowing
physiologic (not true) but with high muscle tone to prevent reflux
X
relaxes
What is the effect of the following on LES tone
- Gastrin
- Secretin & CCK
- decreases
2. decrease
Define achalasia
Inability of LES to relax, causing food accumulation in the esophagus
Esophageal reflux results from ….. . Treated with ……., ….., …… . The symptoms is confused with ……
Incompetent LES
H2 blocker, proton pump inhibitors, fundoplication
MI
* Fundoplication is raising a flap from the fundus area over the base of esophagus
H2 blockers effect is ……, while the proton pump inhibitor effect is …..
- block action of histamin on parietal cells of stomach, decreasing acid production
- Covalently binding to the H/K ATPase pump (final stage of acid secretion) and inactivating it
The major function of stomach is …., …. & ….
storage, mixing & controlled emptying
* small amount of digestion occurs in stomach
What are the muscular layers of stomach?
outer longitudinal, inner circular & inner most unique oblique layer
The stomach pacemaker are ….. & ……
Auerbach (myenteric): between the outer & inner
Submucosal (Meissner’s plexus) in the submucosa
Gastric atony may occur after ….
strong adrenergic stimuli (trauma). May lead to aspiration of retained stomach content
Chyme is formed by ….
mixing the food with gastric acid, mainly in the antrum
Gastric emptying occur in small spurts due to …. . Some factors like ….. also have effect on the rate of emptying
the contraction of the pyloric sphincter with the longitudinal and circular muscles of the stomach.
* pH, liquid/solid nature of food, particle size, caloric density & osmolarity
In the small intestine, the chyme is mixed with …., ….. & …..
bile acids, pancreatic juice & mucosal cells secretions
The mucus in the small intestine is produced by ….. & …… . Its function is ……. . The production is increased by …., ….. & …..
- Brunner’s glands: in the submucosa of the duodenum
- Goblet cells: throughout the intestinal mucosa
* Function of mucous is lubrication & protection from gastric acid, binding of bacteria & immunoglobulins
* increased by physical & chemical stimuli, cholinergic stimulation
….. is the peristalitic movement of small intestine, controlled by …..
Segmentation, myenteric plexus (not extrinsic stimulation)
The major function of the colon is ….
storage of feces, absorption of fluids & electrolytes
* Na is actively transported, water follows. While K & HCO3 are secreted into the colon
The outer muscular layer of colon is called…., which is shorter than the colon, creating …..
teniae coli
haustra (pouching)
The brown color of feces is due ….., while the odor is due to …..
action of bacteria on bile pigments
sulfides & indolic compounds
Rectal distension causes …… . The inner sphincter is ….., while the outer is …..
urge to defecate
- The inner anal sphincter is a smooth muscle (controlled by sacral reflex), while the outer is skeletal (controlled by pedundal N.)
- Gastric distension may increase the urge to defecate, this gastrocolic reflex is mediated by parasym., CCK & gastrin
Gastrin is secreted by ….., CCK is secreted by ….. . Their functions are …..
- G cells: in duodenum and pyloric area. Main role is stimulation of HCl secretion by parietal cells
- by I cells in the duodenal & jeujenal mucosa. Main role is stimulating of pancreatic secretion and gall bladder contraction.
see p. 398 for full functions
Secretin is secreted by ….., GIP is secreted by ….. . Their functions are ……
- S cells of duodenum. Role is increase HCO3 secretion by biliary ducts & inhibiting parietal H secretion
- by K cells in the duodenum. Role is stimulation of insulin release by the pancreas
VIP is located in ….. with the main functions ….
parasympathetic ganglia, sphincters and gallbladder.
has neurotransmitter function (non choinergic & non adrenergic)
1. Increase H2O & HCO3 by cAMP
2. Relax intestinal & gastric smooth muscles, & vasodilation by nitric oxide
VIPoma is
tumor of non alpha & non beta cells of the pancreas that secretes VIP, causes watery diarrhea.
Tx by resection of tumor
Somatostatin is secreted by ….
D cells of pancreas, antrum & hypothalamus. It inhibits gastrin, CCK and most other hormones
Pancreatic polypeptide is secreted by ….
F cells of pancreas & also in the CNS
It inhibits HCO3 secretion & relaxes the gallblader
Substance P is secreted by ….
enterochromaffin cells in CNS, intestine & colon
stimulus for release is vagal –> myenteric
Role is increase GI motility and saliva secretion. Also pain transmission in the CNS
The glands at the cardiac region are….., the ones at body are ….., while the pyloric region contain …..
mucous producing
HCl & intrinsic factor (parietal/oxyntic), chief cells (pepsinogen) & enterochromaffin cells
mucous/gastrin/somatostatin producing
The stomach mucosa has ……
gastric pits
* the neck of the pit mainly mucous & enterochromaffin cells. The body is made of parietal & mucous, while the ones at the base are chief cells
The action of HCl is ….. & …..
denatures protein & bacteria, activates pepsinogen
Pepsinogen is stored in …… in chief cells in order to …… . Its secretion is increased by ….., …..& …..
zymogen granules, protect the cell from its effect
HCl, gastrin & vagal stimulation
Pepsin digests about ….. of protein into peptides
20%
* High pepsin levels may cause acute gastric ulceration. The other contributor is high HCl levels
What are the functions of the intrinsic factor?
important for vit B12 absorption by ilium
The pancreas produces …., ….. & ……
H2O
HCO3 (by ductal cells)
15 enzymes (by acinar cells)
see p.401
Pancreatic secretion is under the control of ….. & ……
vagal stimulation, CCK
Hepatic secretions are …., …. & …., they are under hormonal control by ….
bile, IgA & bilirubin/toxins/drugs
secretin
Bile salts output is under secretin control. T/F
false
secretin control HCO3 secretion from biliary ductules
Bile flow depend on its concentration, and thus upon enterohepatic circulation
Define urobilinogen
the deconjugated form of bilirubin in the intestine. it is colorless
* Further reduced to stercobilin & urobilin
Define bile salts and their funcion
ionized form of bile acids (conjugated with glycin or taurin). Emulsify fat droplets into micelles preparing them for digestion
What is the function of gall bladder?
storage and concentration of bile
* also acidifies bile
The primary bile acids are …… soluble, examples are …… & ……
Conjugation of primary acids to form bile salts is to ….
lipid soluble, cholic & chenodeoxycholic acids
make them water soluble
* 95% of bile salts are absorbed in the ilium to be recycled by the enterohepatic circulation
Bacteria might ….. bile salts, or may reduce them into….., both which are passively reabsorbed into circulation
deconjugate (forming lipid bile acids)
secondary bile acids (deoxycholic & lithocholic acids)
Salivary Amylase hydrolyzes only …..
alpha 1,4 glycosidic linkages
Pancreatic amylase is highest concentration in ….., while oligosaccharides hydrolases are found in …..
duodenum
brush border of jeujenum & proximal ilium
Glucose absorption occurs in ……, and insulin levels rise due to ……
duodenum and jeujenum
GIP
Glucose is transported across the membrane by ….., and fructose by ……
carrier-mediated active process (Na linked, symported)
carrier mediated diffusion (down concentration gradient)
Emulsification of fat begins in …..
stomach (through churning)
* little fat digestion occurs in the stomach
Fats are absorbed by the time it reaches
midjeujenum
After re-esterification of fat, it is incorporated into ……, which are released by exocytosis into ….
chylomicrons
lacteals
Triglycerides with short/medium chain fatty acids require micelles for absorption. T/F
False
they are quickly hydrolyzed
* Fat soluble vitamine A,D,E,K requires micelles
Why HCl is critical for pepsin?
because it is activated at pH 2 , and irreversibly deactivated at pH 5
About ….. of proteins are hydrolyzed in the stomach, the rest is digested and absorbed in
15%
duodenum
Aminoacids absorption requires ……
Na linked carrier (symported)
* Amino acids absorption is the rate limiting step in protein digestion
What are the causes of steatorrhea?
- pancreatic insuffeciency, CF, tumor
- Bile salt deconjugation (due to bacterial over growth)
- liver disease
Tight junctions in the intestinal epithelium are non permeable to water. T/F
False
Iron absorption depends on …., ….. & …..
form, need & amount ingested
* most Ca, iron, folate absorption occurs in duodenum/jeujenum
The most important absorption in the colon occurs with ….. in exchange for ….
Na, K
* water and Cl diffuse passively in the colon
What are the functions of intrinsic innervation of GIT (plexi)
Coordinate motor and secretory functions of GIT
- Auerbach plexus extends from esophagus to anus (between outer and inner layers)
- Meissner’s plexus in the submucosa of gut wall
- Other plexi like subserosal, deep muscular
Vagus nerve fibers project to 3 areas on the GIT. List
- esophageal plexus (esophagus, heart)
- Ant. vagal trunk (gastric, celiac, hepatic, pyloric plexi)
- Post. vagal trunk (pyloric, small intestine, cecum, right ascending and transverse colon)
Sacral parasympathetic fibers from …… innervates ……
2,3,4
innervate left descending, sigmoid and anorectal area
Salivary duct cells absorbs ….. in exchange for ……
Na/Cl, HCO3/K
* Decreased salivary flow below 0.7 mL/min increases caries risk
Ghrelin is …..
is a polypeptide hormone released by the P/D cells in the fundus and from the pancreas
- Its level increases before meals, causing hunger & opposing leptin from adipose tissue.
- It is a strong inducer for GH release from the anterior pituitary
The enterogastric reflex is …..
the distension of the duodenum with chyme causes inhibition of gastric emptying
What are the stages for gastric secretion??
- Cephalic: smell, taste, vision etc…
- Gastric: triggered by food entering the stomach
- Intestinal: triggered by low pH food entering the duodenum
* Gastric secretion is inhibited via hormonal and enterogastric reflex
What is the location of the different GLUT proteins??
- GLUT1: RBC
- GLUT2: renal, liver, intestine
- GLUT3: Placenta, neurons
- GLUT4: insulin controlled. Skeletal muscles, adipose tissue
In prolonged starvation, the major producer of glucose would be the ……
kidney
The first spot where jaundice is detected is …..
under the tongue
