10 important points to remember while studying Digestion & Absorption
Preparing for NEET 2019? Click to know the 10 important points you must remember while studying Human Physiology-Digestion & Absorption by our experts.
We hope your preparation is now in the 5th gear, as you are very close to your destination.
In this article, we’ll be talking about Human Physiology: Digestion and absorption. This topic is quite sorted if you read it with utmost strategy. You should know what to read and what not. The questions asked in this chapter are repetitive. There are only a few topics of which the questions are asked. Out of this huge chapter, we’ll be sorting out important topics from which the questions have popped in previous years. This topic generally holds 16+ marks in NEET exam and is equally important for AIIMS/JIPMER.
Here when we are discussing this topic with you we’ll also be explaining in short some of the terms for quick revision purpose. But you all will have to go through these terms and terminology in detail for your preparation.
Now we’ll be discussing the 10 important topics from Digestion and Absorption from NEET point of view.
1. Oral Cavity and Dental Formulae
Questions are asked every alternate year from this topic. Example- About various papillae of the tongue, internal structure of teeth, dental formulae, types of salivary glands. The questions are very simple but often we tend to ignore those simple things for more complex topics. So, we should at least give this a read before attempting our NEET paper.
The important subtopics are-
- It is attached to the floor of the mouth by a fold called lingual frenulum.
- 4 papillae- Vallate papillae, Filiform papillae, Fungiform papillae, Foliate papillae.
- Helps in chewing, acts as brush, aids in swallowing, helps in speech, organ of taste.
- Diphyodont, Thecodont, Heterodont.
- 4 types Incisors, canines, Pre-molars, Molars
- Dental formulae (2123/2123)X2=32
- Structure: Enamel is the hardest substance of the human body. Enamel covers the Dentin which has fine canaliculi passing through. Dentin closes the pulp cavity which has a mass of cells, blood vessels, and nerves which constitute the pulp. Narrow extensions of pulp cavity called root canals.
2. Digestion in Stomach
This topic has quite a popularity amongst the paper setters. The various parts from which the questions are asked generally are listed down below.
- Widest organ of alimentary canal; J- shaped organ
- The lesser curvature is on the posterior side of the stomach and the greater curvature is on the anterior side of the stomach.
- 4 parts-
- Cardiac part (Cardia)- The cardiac sphincter lies in oesophagus and stomach. It's not a valve but a functional sphincter.
- Fundus- Its filled with air or gas.
- Body- Main part
- Pyloric part- Posterior part of the stomach.
- Digestion of Proteins
Pepsinogen ---HCl--------⇒ Pepsin
Proteins ---Pepsin---------⇒ Peptones and peptides
- The stomach normally stores the food for 4-5 hrs. The gastric glands of the stomach secrete gastric juice (hydrochloric acid, pepsinogen).
- The thick acidic mixture of gastric juice and semi-digested food is called
- Sometimes chyme is squeezed into the oesophagus. This causes burning of some cells, called heart burn= pyrosis= hyperacidity.
- Microscopic, tubular glands formed by the epithelium of the stomach.
- 3 major types-
- Chief cells/ peptic cells- Secrete gastric digestive enzymes such as proenzymes* (pepsinogen or prorenin). Also, produce the small amount of gastric amylase and lipase.
- Oxyntic cells/ Parietal cells- They secrete HCl and Castle’s intrinsic gastric factor which helps in the absorption of Vitamin B12.
- Mucous cells/ Goblet cells- Secrete mucus.
3. Digestion in Intestine
Few times questions have been asked from the topic of digestion in the intestine. You need to know the function of all parts of the intestine. The enzyme and their functions acting in the small intestine.
- 3 parts-
- Duodenum- C- shaped. The hepatopancreatic ampulla opens into the duodenum. This ampulla receives both bile duct from liver and juices from the pancreas.
- Jejunum- Thick walls and more muscular.
- Ileum- Longest part of the small intestine
- Digestion of carbohydrates-
Maltose -----Maltase-⇒ Glucose
Lactose -----Lactase---⇒ Glucose+Galctose
- Digestion of proteins-
Trypsinogen ----Enterokinase--⇒ Trypsin
Proteins+ Peptones ----- Trypsin-⇒Dipeptides
- Digestion of nucleic acids-
Nucleotides -----Nucleotidases--⇒ Nucleosides + iP
Nucleosides -----Nucleosidases-⇒ Nitrogenous bases + Pentose sugar
PYQ: In the absence of enterokinase, the digestion of ____________ would be affected in our intestine.
- Albumin b) starch c) maltose d) amino acids
4. Enzymes of Digestive Gland
You need to know the function of important enzymes which help in the process of digestion. Questions asked on this topic are very frequent and very direct. You just need to know the simple functions of each enzyme.
- Proteases and peptidases split proteins into small peptides and amino acids.
- Lipases split fat into three fatty acids and a glycerol
- Amylases split carbohydrates such as starch and sugars into simple sugars such as glucose.
- Nucleases split nucleic acids into nucleotides.
Study the function of particular enzymes like- pepsin, Intrinsic factor, Gastrin, Gastric lipase, Trypsinogen, CCK, Erepsin, Maltase, Lactase etc.
PYQ: Which one of the following enzymes carries out the initial step in the digestion of milk in humans?
- Pepsin b) renin c) lipase d) trypsin
PYQ: The salivary amylase shows maximum digestive action at pH _____
- 6 b) 6.8 c) 7.5 d) 8.5
5. Function of Bile
Functions of Bile are important as a question like, is/is not a function of bile might come. The functions of bile juice are-
- Neutralization of HCl- It neutralizes the HCl of the chyme.
- Emulsification- breaks large food droplets into smaller ones.
- Absorption of Fats and fat-soluble vitamins
- Stimulates peristalsis- increases peristalsis in the intestine.
- Activation of lipase- contains NO enzyme but activates lipase.
6. Pancreas- Detail
The detailed study of the pancreas is important as the histology of pancreas is the most important topic of this chapter. The different cells of pancreas secreting different hormones like- insulin, glucagon etc. It is the endocrine organ/gland.
7. Neural Regulation
In this topic, you need to know about two things- Enteric neural system, extrinsic innervation. Although this topic has not been asked in last 5 years, it can be raised in the upcoming exam.
8. Absorption of Monomers
Repeatedly questions have been asked on this topic say, the absorption of monosaccharide in the large intestine, absorption of amino acids, fatty acids, water, salts etc.
PYQ: Select the correct match of the digested products in humans given in column 1 with their absorption site and mechanism in column 2
Column I Column II
1) Glycine, glucose Small intestine, active absorption
2) Fructose, Na+ Small intestine, passive absorption
3) Glycerol, fatty acids Duodenum, move as chylomicrons
4) Cholesterol, maltose Large intestine, active absorption
PYQ: Fructose is absorbed into the blood through mucosa cells of intestine by the process called
a)Active transport b) facilitated transport c) simple diffusion d) co-transport mechanism
9. Nutritional Requirements of Humans|Balance Diet
This topic is not mentioned elaborately in your NCERT but has been asked in NEET/AIIMS twice simultaneously. So take a brief idea about this from reference books.
Questions are put up from disorders they are very simple and direct questions so you need not worry much about it. Just give a quick read to the following list-
- Kwashiorkor- growth retardation, usually observed in children age 1-5.
- Xerophthalmia or Night Blindness- Deficiency of Vitamin A.
- Jaundice- excess production of bilirubin, congenital liver disease, blockage of bile drainage.
- Diarrhoea- increase in frequency, volume and fluid content of faeces caused by increased motility of and decreased absorption by the intestine.
- Malnutrition- not getting enough food or right kind of food.