Gastrointestinal Physiology MBBS Year 1

Questions and Answers

What is the primary function of lymphatic vessels in the tract?

To innervate the GI tract with autonomic motor and sensory fibres

To secrete electrolytes and proteins into the oral cavity

To aid in the intestinal absorption of dietary fat (correct)

To regulate the endocrine control of the GI tract

What is the main function of saliva in the digestive process?

To aid in the digestion of proteins

To regulate the pH of the stomach

To lubricate food for swallowing and aid in starch digestion (correct)

To stimulate the secretion of gastric acid

What is the outermost layer of the histological organisation of the digestive tract?

Submucosa

Muscularis externa

Adventitia/Serosa (correct)

Mucosa

What type of fibres are present in the GI tract?

Both parasympathetic and sympathetic motor fibres Signup and view all the answers

Where are endocrine cells widely distributed in the GI tract?

Throughout the epithelia of stomach, small and large intestine, appendix, distal esophageal glands, and ducts of pancreas and liver Signup and view all the answers

What are the two phases of gastric acid secretion?

Basal, cephalic, gastric, and intestinal phases Signup and view all the answers

What is the structure that increases in size in an activated parietal cell?

Intracellular canaliculus Signup and view all the answers

What is the significance of vascular and lymphatic vessels in the GI tract?

For the aid in nutrient absorption and supply of nutrients to the epithelial tissue Signup and view all the answers

Which of the following neurotransmitters is released at or near the basolateral surface of parietal cells?

Acetylcholine Signup and view all the answers

What is the mechanism by which histamine reaches the parietal cells?

Paracrine mechanism Signup and view all the answers

Which of the following statements is true about gastrin?

It is released by G cells into the bloodstream Signup and view all the answers

What is the target of proton pump inhibitors like omeprazole?

The proton pump itself on parietal cells Signup and view all the answers

What is the mechanism by which gastrin reaches the parietal cells?

Endocrine mechanism Signup and view all the answers

What is the function of D cells?

To release somatostatin and inhibit acid secretion Signup and view all the answers

Which of the following statements regarding the digestion of carbohydrates is incorrect?

The stomach plays a significant role in the digestion of carbohydrates. Signup and view all the answers

What is the primary function of the muscular valves or sphincters that separate the organs of the digestive tract?

To prevent the backflow of digested contents from one organ to the previous one. Signup and view all the answers

Which of the following layers of the gastrointestinal tract is directly responsible for the lining of the inner surface of the digestive tract?

Mucosa Signup and view all the answers

What is the primary function of bile salts secreted by the liver?

To emulsify fats, making them easier to digest. Signup and view all the answers

What is the correct sequence of the major organs in the digestive tract, starting from the mouth?

Mouth, esophagus, stomach, small intestine, large intestine. Signup and view all the answers

Which of the following is NOT a function of the endocrine control of the gastrointestinal tract?

Coordination of muscle contractions in the digestive tract. Signup and view all the answers

Which of the following is NOT a feature common to all four major organs of the digestive tract after the mouth?

They all directly receive secretions from the exocrine pancreas. Signup and view all the answers

Which of the following statements regarding the enterohepatic circulation is correct?

It involves the recycling of bile salts between the liver and the small intestine. Signup and view all the answers

What is the main characteristic of pancreatic juice in terms of its protein synthesis rate?

It has a high rate of protein synthesis, second only to the lactating mammary gland. Signup and view all the answers

Which component of pancreatic juice is responsible for neutralizing duodenal content?

HCO3 Signup and view all the answers

Which of the following is NOT a proteolytic enzyme found in pancreatic juice?

Amylase Signup and view all the answers

What role do bile salts play in digestion?

They are necessary for the absorption of dietary fats. Signup and view all the answers

Which enzyme in pancreatic juice is specifically responsible for hydrolyzing neutral fats?

Lipase Signup and view all the answers

Which regulatory mechanism is NOT involved in the digestion and absorption of dietary nutrients?

Direct absorption through cell membranes without assistance Signup and view all the answers

Study Notes

Overview of the Digestive System

GI tract consists of serosa, muscularis externa, submucosa, and mucosa, each layer having distinct functions.
Comprises four main organs: esophagus, stomach, small intestine, and large intestine, separated by sphincters.
Carbohydrate digestion begins in the mouth via amylase; most digestion and absorption occurs in the stomach and small intestine.
Exocrine products such as bicarbonate from pancreas and bile salts from liver are crucial for digestion in the small intestine.
Lymphatic vessels aid in the absorption of dietary fats throughout the GI tract.

Salivary Secretions

Salivary glands release electrolytes and proteins, including amylase, to aid food lubrication and starch digestion.
Saliva consists of glycoproteins from submandibular and sublingual glands, facilitating swallows.

Histological Organization and Functionality

Four layers of the digestive tract: mucosa, submucosa, muscularis externa, and adventitia/serosa, with distinct roles in digestion.
Vascular and lymphatic networks support nutrient supply and the removal of waste.
Autonomic nervous system fibers control both motor and sensory functions within the GI tract.
Endocrine regulation involves gut hormones affecting digestion through neurocrine, paracrine, and endocrine mechanisms, distributed across GI epithelium.

Gastric Acid Secretion Phases

Gastric acid secretion occurs in two phases: basal (fasting) and stimulated (post-prandial), subdivided into cephalic, gastric, and intestinal phases.

Regulation of Acid Secretion in Parietal Cells

Acid secretion regulated by acetylcholine, histamine, and gastrin, termed Soll's three receptor hypothesis.
ACh, gastrin, and histamine are involved in different regulatory mechanisms (neurocrine, endocrine, paracrine) affecting parietal cells.
G cells secrete gastrin into circulation, stimulating acid secretion through interactions with parietal cells.

Pancreatic Juice Secretion

The pancreas has a high protein synthesis rate, except for lactating mammary glands.
Aqueous component contains bicarbonate to neutralize acidic chyme entering the duodenum.
Enzyme components include proteolytic enzymes like trypsinogen, chymotrypsinogen, amylase, and lipase for nutrient breakdown.

Digestion and Nutrient Absorption

Carbohydrates, amino acids, and oligopeptides undergo breakdown and absorption through specialized mechanisms.
Bile salts play a critical role in dietary fat absorption, influencing emulsification and micelle formation.
Digestion and absorption processes are regulated through multiple stimulatory and inhibitory pathways involving hormones.

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Description

Quiz based on lectures for MBBS Year 1 students, covering the digestive system, secretions, digestion, and absorption of nutrients, motility, and biliary system. References from Physiology textbooks by Berne, Levy, Koeppen, and Stanton, and Boron and Boulpaep.