Physiology of GIT digesion, Essays (university) of Physiology

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REVISION

GIT PHYSIOLOGY

(Midterm Exam, L1-L6)

(MCQS + Important Notes)

DONE BY:

Mohammed AlTuwijri

Omar AlRahbeeni

1. Muscles in the propulsive and receiving segments of the GI tract respond differently to food movement through the gut. Which of the following statements correctly describes activity in the propulsive segment? A. The circular and longitudinal muscles are contracted. B. The longitudinal muscles are contracted and the circular muscles are relaxed. C. Both the longitudinal muscles and circular muscles are relaxed. D. The circular muscles are contracted and the longitudinal muscles are relaxed.
2. Which of the following is characteristic of the segmenting movements in the small intestine? A. It decreases particle size, which increases the surface area for digestion. B. It brings the products of digestion to the mucosal surface for absorption. C. It results in the mixing of the luminal contents in front of the propulsive segments (i.e. in the receiving segments) D. All of the above.
3. Which of the following is NOT involved in swallowing? A. Contracture of the upper esophageal sphincter. B. Coordination by the swallowing center in the medulla oblongata. C. The approximation of the vocal cords to close the glottis. D. The raising of the larynx to close its entrance.
4. Choose the correct listing of the anatomical divisions of the stomach in the direction food normally passes. A. Corpus, fundus, antrum. B. Fundus, antrum, corpus. C. Antrum, corpus, fundus. D. Fundus, corpus, antrum.
5. Which of the following salivary components continues to be active in the acidic environment of the stomach? A. Alpha-amylase B. Lingual lipase.
6. If you follow the path that food normally takes through the digestive system, which of the following is in the correct order? A. Upper esophageal sphincter, epiglottis, lower esophageal sphincter, pyloric canal, duct of Santorini, duct of Wirsung. B. Pharynx, epiglottis, lower esophageal sphincter, pyloric canal, duct of Wirsung, duct of Santorini. C. Pharynx, epiglottis, lower esophageal sphincter, pyloric canal, duct of Santorini, duct of Wirsung. D. Pharynx, upper esophageal sphincter, pyloric canal, lower esophageal sphincter, duct of Wirsung, duct of Santorini.

13. Vitamin B12 is absorbed mainly in the:

A. stomach B. ileum C. colon D. jejunum

14. Saliva contains the carbohydrate-digesting enzyme: A. pepsin B. carboxypeptidase C. amylase D. trypsin E. lipase
15. Which is the primary absorptive organ of the digestive system? A) small intestine B) stomach C) colon D) pancreas
16. Which tissue layer provides for primary digestive motility? A) Mucosa B) submucosa C) mesentery D) muscularis mucosa
17. during swallowing: A) All processes are consciously controlled B) the swallowing center located in the medulla oblongata inhibits the medullary respiratory center c) the food bolus is forced down the esophagus by gravity

18. Proteins are primarily digested to and absorbed as...

A) amino acids

B) monosaccharides

C) nucleic acids

D) fatty acids & glycerol

19. HCL secretion by the stomach... A) Is triggered by chewing B) denatures proteins C) activates enzymes that digest proteins D) all of these
20. What prevents food from entering the nasal passages during swallowing? A) elevation of uvula B) contraction of pharyngeal muscles C) apposition of vocal folds D) elevation of epiglottis

21. The serosa is...

A) abdominal cavity containing the stomach inner lining of the digestive tract

B) outer connective tissue covering of the digestive tract

22. Some absorption occurs in the large intestine, but this is mostly limited to... A) amino acids B) water & electrolytes C) fatty acids
23. The major chemical digestive activity that takes place in the stomach is... A) breakdown of starch B) breakdown of proteins C) digestion of fats D) neutralization of acid by buffers & mucous

24. Bile acts on...

A) distention in the stomach

B) acid in the stomach

C) fat in the stomach

D) fat in the duodenum

25. Chief cells of gastric mucosa secrete... A) Trypsin B) bicarbonate ions C) pepsinogen D) HCL
26. Which of the following is true about pancreatic secretions? A) CCK causes release of bicarbonate B) secretin causes release of enzymes C) gastrin stimulates release of enzymes D) CCK stimulates release of enzymes while secretin stimulates release of bicarbonate
27. The hormone that inhibit gastric secretion and motility is... A) Gastrin B) histamine C) secretin D) Pepsin
28. Intrinsic factor is... A) secreted by parietal cells and is responsible for vitamin B12 absorption B) not necessary for normal body function C) abundant in pernicious anemia D) an aminopeptidase

37. The volume of food in the stomach has which of the following effects on stomach emptying?

As the volume increases, the rate of emptying increases

38. Which of the following is true of the gastro enteric reflex?

B) It leads to defecation

C) It stimulates contractions of the colon

A) It leads to increased peristaltic activity in the small intestine

39. Which of the following decreases blood flow to the villi of the small intestine?

B) Norepinephrine

40. A patient with trigeminal neurapraxia (temporary segmental demyelination of the trigeminal nerve leading to conduction difficulties) would have the greatest difficulty with which of the following activities?

A) Secondary peristalsis in the esophagus B) Swallowing C) Secondary peristalsis in the esophagus D) Chewing

41. Sodium export through the brush border of the intestinal epithelial cells occurs by which of the following mechanisms?

A): passive diffusion B) Facilitated diffusion

42. Which of following digestive organs does not show peristalsis: A) Esophagus B) Stomach C) Small intestine D) Caecum
43. Regarding slow-waves: A) Cause Muscle contractions by themselves. B) Are Action potential C) Cause Sodium Ions to Enter. D) Cause by interaction between smooth muscle cells and interstitial cells of Cajal. E) Both C+D

Important Notes:

-ICC are involved in the generation of slow waves, which trigger action potentials.

-Each action potential gives rise to a twitch-like contraction; if the frequency of action potentials is sufficient, a tonic-like level of contraction is observed.

-Elevation of intracellular calcium is required to initiate this contraction.

-Smooth muscle fibers are coupled via gap junctions allowing low resistance propagation of electrical signals through the fibers.

-THE MUCOSAL LAYER IS THE INNERMOST LAYER, IT CONSISTS OF:

1-MUCOUS EPITHELIUM:

LOCATION TYPE

MOUTH, OROPHARYNX, ESOPHAGUS, ANUS STRATIFIED

SQUAMOUS

REMAINDER OF THE G.I. TRACT

SIMPLE

COLUMNAR

2-LOOSE CONNECTIVE (LAMINA PROPRIA).

3-THIN MUSCLE LAYER (MUSCULARIS MUCOSA).

- CHARACTERISTICS OF G.I. WALL:

-FUNCTIONS AS A SYNCYTIUM.

-BUNDLES OF 1000+ FIBERS.

-FIBERS ELECTRICALLY CONNECTED BY GAP JUNTIONS.

-IMPULSE TRAVELS RAPIDLY FROM FIBER TO FIBER.

-CONTINUAL SLOW ELECTRICAL ACTIVITY.

- ALLOWS FOR TWO BASIC TYPES OF WAVES: 1-SLOW WAVES: 2-SPIKES:

-ARE NOT ACTION POTENTIALS -SLOW UNDULATING CHANGES IN THE MEMBRANE POTENTIAL -OCCURS 3 PER MINUTE IN STOMACH AND 12 PER MINUTE IN SMALL INTESTINE

-TRUE ACTION POTENTIALS

-OCCUR AUTOMATICALLY WHEN RESTING

POTENTIAL

-GOES BELOW 40 MILLI VOLTS= 1-10 SPIKES PER

SECOND

Hormones/Enzymes Secreted cells Function

Pepsinogen chief cells^ Digestion of Proteins

Lipase enzyme Fundus^ mucosa^ hydrolyze TAG to MG&FA Alpha-Amylase Salivary^ glands^ and Pancreas

Digestion of CHO

Intrinsic factor parietal cells (oxyntic)^ Absorption^ of B12 in Ilium VIP -^ Relaxation of Gastroesophageal stomach GRP -^ Stimulation of Gastrin (G cells) GIP K cells^ Inhibit^ emptying^ of stomach^ + decreases gastric secretion + increase secretion of insulin Gastrin G-cells^ Stimulation^ of^ Partial^ cells + contraction of gastroesophageal Sphincter HCL parietal cells (oxyntic)^ Increase digestion^ and motility of Stomach Mucus & HCO3 Mucus Neck Cells^ Neutralization the acidity Secretin S-cells^ Inhibit^ emptying^ of Stomach^ + relaxation of gastroesophageal sphincter + increase HCO secretion from the pancreas + decrease gastric secretion

Enterogastrones intestines^ inhibitory hormones

CCK I-cells in duodenum and jejunum

Inhibit emptying of Stomach + relaxation of gastroesophageal sphincter + increase pancreatic enzymes + contraction of gall bladder

-Pepsinogen is converted to pepsin by: HCL -The hunger pangs are felt in: Stomach

• SOME SHORT CHAIN FATTY ACIDS ARE DIRECTLY ABSORBED INTO THE BLOOD SYSTEM.
• Trypsinogen is converted to trypsin by: Enterokinase or Trypsin
• Chymotrypsinogen, Procarboxypeptidase are converted to their active forms by Trypsin.

Good luck

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