Question

1. Swallowing a bolus of food involves both voluntary and involuntary movements of the muscles in the mouth, pharynx, and esophagus.  The voluntary phase includes movements of the tongue and mouth to position a bolus of food at the back of the throat near the pharynx. From this point forward, identify the receptors, signaling molecules, and muscle movements that are necessary to bring the bolus of food from the pharynx to the stomach.
2. Identify the cell(s) that produce the following substances and indicate their major action(s) related to the processes of digestion and absorption.Your answers should be specific and concise.
4. 1. Cholecystokinin (CCK):
6. 2. Enterokinase:
8. 3. Gastrin:
10. 4. Secretin:
12. 5. Histamine:
14. 6. Bile:

Answer 1

2.Ans-

a.Cholecystokinin (CCK): Cholecystokinin or pancreozymin, is secreted by enteroendocrine cells in the duodenum of the upper small intestine.

The function of the small intestine:

The small intestine is involved in digestion and absorption of food which are the following:

Role in- digestion:

Digestion takes place in two different parts-

.i. Mechanical digestion: It is the first part where chewing, grinding, churning and mixing takes place in the mouth and the stomach.

ii. Chemical digestion: It is the second part where enzymes and bile acids etc are used for digestion and takes place in the small intestine.

Digestion of proteins: Digestion of proteins, peptides, and amino acids takes place by trypsin and chymotrypsin enzymes that secreted by the pancreas and breaks down into smaller peptides.

Digestion of lipids: Lipase is secreted by the pancreas that digests fats and lipids and breaks down into free fatty acids and monoglycerides. The bile salts help in holding the triglycerides in the water form so that the lipase can break down into the smaller form to enter the intestinal villi for absorption.

Digestion of carbohydrates

Amylase breaks down carbohydrates into simple sugars and glucose.

Absorption in the small intestines: Absorption takes place in the inner walls of the small intestine after breaking down the nutrients into smaller parts. The nutrients are absorbed by different processes such as simple diffusion, facilitated diffusion, primary active transport, and secondary active transport. For transportation,

Lipids undergo simple diffusion

Short-chain fatty acids undergo diffusion

Amino acids undergo primary active transport

Glucose undergo secondary active transport

Fructose underdo facilitated diffusion

Other absorbed substances in the small intestines include:

Other substances such as water, electrolytes and vitamins and minerals are absorbed by osmosis, diffusion, and active transport and diffusion respectively.

b.Enterokinase: Duodenum produces enterokinase.

Digestion: The duodenum is mainly responsible for the 1^st phase of digestion in the small intestine. In the duodenum, food that comes from the stomach is mixed with pancreatic enzymes and bile for the breakdown. Then it transports into the jejunum where the nutrients are absorbed by the inside walls except iron which is absorbed in the duodenum.

c.Gastrin: Gastrin is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach

Digestion:

Parietal cells are mainly responsible for producing both hydrochloric acid (HCl) and intrinsic factor whereas HCL is involved to activate the protein-digesting enzyme called pepsin and also help in kill bacteria.

Absorption:

intrinsic factor is responsible for the absorption of vitamin B₁₂ that used for cellular metabolism and also help in producing red blood cells. Most of the absorption takes place in the small intestine except water during dehydration, aspirin, amino acids, caffeine, and a small amount of water-soluble vitamins.