31 Years NEET Previous Year Questions: Digestion & Absorption - 3 (Old NCERT) - NEET MCQ

A pair of parotid glands (the largest salivary glands) present in the cheeks just under the ears open in the vestibule (a narrow, groove like space which separates the gums from lips and cheeks) by the parotid ducts also known as Stensen’s duct.

A pair of submaxillary glands lie at the angles of lower jaw open by submaxillary ducts also known as Wharton’s ducts open under the tongue behind the lower incisor of its sides. These glands are present in most mammals but absent in Rabbit & Horses. They mostly secrete mucus of saliva

Cholecystokinin (in fact it is cholecystokinin - pancreozymin CCKPZ) is a hormone which is secreted by the duodenal wall. It causes the release of bile by the contraction of the gall bladder & increases the enzyme release process of pancreatic cells. The pancreatic juice enterokinase is an ‘activator enzyme’ which is present in intestinal juice (success entericus) and converts the inactive proenzyme trypsinogen to active trypsin enzyme. Secretin is also a hormone and causes the release of sodium bicarbonate in the pancreatic juice (it is said that the production of pancreatic juice is stimulated by secretin & its release is stimulated by CCK-PZ)

Pancreatic juice secretion is regulated by the hormone secretin, which is produced by the walls of the duodenum upon detection of acid food, proteins, and  fats.

Bile salts viz sodium glycocholate & sodium taurocholate (both are organic salts present in bile) reduce the surface tension of large fat globules and break them to fine minute fat droplets. This process is known as emulsification of fat.

Zymogen or chief cells are mainly found in the fundic part of the stomach. They are the most abundant among the gastric glands & secrete proenzymes, propepsin and prorenin. (They are also present in intestine but their main site is stomach).

Pancreas consists mainly of large lobules / acini / alveoli and secretes pancreatic juice. In between the acini, here and there i.e. randomly spread endocrine cells are present known as Islets of Langerhans which consist of  a, b, and F cells & secrete insulin, glucagon, pancreatic polypeptide and somatostatin hormones.

Protein digestion starts in the stomach with the action of enzyme pepsin. Then in the duodenum it is done by the action of trypsin, chymotrypsin & carboxypeptidases (all from Pancreatic Juice). Then aminopeptidases & dipeptidases, enterokinase in jejunum and then it ends in the ileum.

Pancreas produces enzymes (i) trypsinogen which is then activated by the enterokinase into active trypsin (ii) chymotrypsinogen which is again an inactive proenzyme, activated by trypsin (iii) procarboxypeptidases which are activated into carboxypeptidases by trypsin and two hormones (a) Insulin (b) Glucagon which control glucose level in the blood.

These are the tubulo-alveolar glands present in the submucosa of duodenum only. They secrete an alkaline mucus with very little enzymes & pour their secretion into crypts of Lieberkuhn.

 Enterogestrone is a hormone secreted by intestinal mucosa and it has an inhibitory effect on gastric juice from gastric glands in stomach.

Vitamin K (Phylloquinone = Nepthaquinone) also known as ‘Antihaemorrhagic factor’. This vitamin is essential for the synthesis of prothrombin in liver cells which is essential for normal blood clotting. It is also synthesized by the colon bacteria.

Although traces of fat digesting enzyme (gastric lipase) have been reported but due to its very little concentration, it is unable to start fat digestion in stomach. Fat digestion starts in duodenum with the help of bile salts & pancreatic juice but completes in small intestine.

Pellagra which is characterized by skin inflammation specially thick pigmented skin of hands and legs, swollen lips, diarrhoea & nervous disorder is caused by the deficiency of vitamin B3 which is also known as Nicotinic acid or Vitamin P.P. (Pellagra preventing vitamin)

Kupffer’s cells or stellate cells are active phagocytic cells present in the liver. They engulf the warn out and dead RBCs & break out haemoglobin. They are also infact hepatic macrophages.

The Wharton’s ducts are associated with submaxillary glands that lie at the angles of the lower jaw. These ducts open under the tongue. Ducts of Rivinus are associated with sublingual salivary gland. Stenson’s duct is associated with parotid gland. Brunner’s glands are present in the intestine.

Inhibition of gastric juice secretion is done by a hormone (secreted by the intestinal mucosa) called enterogastrone while stimulation of gastric juice secretion is done by the hormone gastrin secreted by the pyloric stomach mucosa. On the other hand pancreatic & bile secretions are controlled by a hormone complex cholecystokinin pancreozymin (CCKPZ) secreted by the intestinal mucosa.

Pellagra.

Vitamin D (Ergocalciferol or Antirachitic vitamin) which is commonly known as ‘sunshine vitamin’ regulates the absorption of calcium & phosphorus from gastrointestinal tract and hence helping in the normal growth of bones & teeth. Its deficiency disturbs the Calcium & Phosphorus absorption and hence deficiency of these minerals in the body which causes soft bones which become curved and fragile (osteomalacia) and teeth decay

The enzyme enterokinase (enteropeptidase) helps in the conversion of trypsinogen (inactive form of another enzyme) into trypsin (active form of the enzyme) for protein digestion in the intestine.

The scurvy is a disease with bleeding gums, thin bones etc. It is caused due to the deficiency of vitamin C. It can be cured by taking citrus fruits.

Vitamin K is also called anti-haemorrhagic factor or phylloquinone. Its deficiency causes delayed blood clotting. Even minor injuries in the body of those people cause profuse bleeding (haemorrhage).

 The excess of fluorine in water causes a condition called fluorosis, which is identified by mottling of teeth (yellowish streaks) and abnormal bones liable to fracture etc

A patient of high blood cholesterol is suggested to take unsaturated fats as vegetable oils. Such as ground nut oil because high intake of saturated fat causes high blood cholesterol which ultimately gets deposited in the walls of arteries causing their blockage resulting in various cardiac-disease. Ghee, butter, red meat vanaspati, they all are rich sources of saturated fats.

Beri-beri is a deficiency disease caused by the lack of vitamin B1 (Thiamine) in the diet. The deficiency of riboflavin (Vit.B2) causes ariboflavinosis. Scurvy is the result of lack of vitamin C in the diet. Deficiency of calciferol (vitamin D) in the diet causes rickets in children and osteomalacia in adults.