Nutrient Absorption in the Digestive System

Micelles are formed when bile emulsifies the fat which makes it water soluble and can be absorbed by the intestinal wall. Later on, they convert into chylomicrons by coating them with proteins are absorbed by the lymph vessels which transport it into a blood and then it reaches the cell.

Micelles are formed when bile emulsifies the fat which makes it water soluble and can be absorbed by the intestinal wall, later on, they convert into chylomicrons by coating them with proteins are absorbed by the lymph vessels which transport it into a blood and then it reaches the cell.

Triglycerides are emulsified by bile and hydrolyzed by the enzyme lipase, resulting in a mixture of fatty acids and monoglycerides. These then pass from the intestinal lumen into the enterocyte, where they are re-esterified to form triacylglycerol. The triacylglycerol is then combined with phospholipids, cholesterol ester, and apolipoprotein to form chylomicrons. These chylomicrons then pass into the lacteals, forming a milky substance known as chyle. The lacteals merge to form larger lymphatic vessels that transport the chyle to the thoracic duct where it is emptied into the bloodstream at the subclavian vein.

• Villi present in small intestine increase intestinal absorptive surface area providing efficient absorption of nutrients in lumen.
• Mucosa is an innermost layer of tissues seen in the small intestine and is a mucous membrane that secretes digestive enzymes and hormones.
• A submucosa layer provides blood vessels, nerves and lymphatic vessels to support mucosa on the surface to protect the wall.

• During starvation the priority of the metabolism in body is to provide sufficeint glucose to the brain and other tissues that are absolutely dependent on this fuel,. 
• However precursors of the glucose are not abundant at the time of starvation and most of the stored fatty acid is utilised at times like this.
• These fatty acid cannot be converted to glucose because acetyl CoA cannot be transformed to pyruvate.
• Therefore the fatty acid that are stored in the body are converted to acetyl CoA and are used in the metabolism to provide energy to the body in the state of starvation.
• Therefore the answer option 'Fatty acid degradation' is correct.
  

Statement (i) is incorrect because fructose is absorbed by facilitated diffusion, not simple diffusion. Statement (ii) is incorrect because the urge for defecation is initiated by stretch receptors in the rectal wall, not an endocrinal action.

All statements provided are correct descriptions of chylomicrons: they are formed in intestinal epithelial cells, contain lipids, are protein-coated, and enter lacteals.

(i) simple diffusion

Each villus has a network of capillaries and fine lymphatic vessels called lacteals close to its surface. The epithelial cells of the villi transport nutrients from the lumen of the intestine into these capillaries (amino acids and carbohydrates) and lacteals (lipids). The absorbed substances are transported via the blood vessels to different organs of the body, where they are used to build complex substances such as the proteins required by our body. The food that remains undigested and unabsorbed passes into the large intestine.