By going through these CBSE Class 11 Biology Notes Chapter 16 Digestion and Absorption, students can recall all the concepts quickly.

Digestion and Absorption Notes Class 11 Biology Chapter 16

→ The digestive system of humans consists of an alimentary canal and associated digestive glands.

→ The alimentary canal consists of the mouth, buccal cavity, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.

→ The accessory digestive glands include the salivary glands, the liver (with gall bladder) and the pancreas.

→ Inside the mouth, the teeth masticate the food, the tongue tastes the food and manipulates it for proper mastication by mixing with the saliva.

→ Saliva contains a starch digestive enzyme, salivary amylase that digests the starch and converts it into maltose (disaccharide).

→ The food then passes into the pharynx and enters the oesophagus in the form of a bolus, which is further carried down through the oesophagus by peristalsis into the stomach.

→ In the stomach mainly protein digestion takes place.

→ Absorption of simple sugars, alcohol and medicines also takes place in the stomach.

→ The chyme food enters into the duodenum portion of the small intestine and is acted on by the pancreatic juice, bile and finally by the enzymes in the succus entericus so that the digestion of carbohydrates, proteins and fats is completed.

→ The food then enters into the jejunum and ileum portions of the small intestine.

→ Carbohydrates are digested and converted into monosaccharides like glucose. Proteins are finally broken down into amino acids.

→ The fats are converted to fatty acids and glycerol.

→ The digested end products are absorbed into the body through the epithelial lining of the intestinal villi. The undigested food (faeces) enters into the caecum of the large intestine through the ileocaecal valve, which prevents the backflow of the faecal matter.

→ Most of the water is absorbed in the large intestine.

→ The undigested food becomes semi-solid in nature and then enters into the rectum, anal canal and is finally egested out through the anus.

→ Digestion: Digestive system process of conversion of complex food substances to simple absorbable forms is called digestion and is carried out by our digestive system by mechanical and biochemical methods.

→ Thecodont: The oral cavity has a number of teeth and a muscular tongue. Each tooth is embedded in a socket of the jaw bone. This type of attachment is called thecodont.

→ Diphyodont: A set of temporary milk or deciduous teeth replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont.

→ Papillae: The upper surface of the tongue has small projections called papillae, some of which bear taste buds.

→ Epiglottis: A cartilaginous flap called epiglottis prevents the entry of food into the glottis-opening of the wind pipe-during swallowing.

→ Stomach: The oesophagus is a thin long tube that extends posteriorly passing through the neck, thorax and diaphragm and enlarges into a T shaped bag-like structure called the stomach.

→ Villi: The innermost layer lining the lumen of the alimentary canal is the mucosa. This layer form irregular folds (rugae) in the stomach and small finger-like foldings called villi in the small intestine.

→ Microvilli: The cells lining the villi produce numerous microscopic projections called microvilli giving a brush border appearance.

→ Lacteal: Villi are supplied with a network of capillaries and a large lymph vessel called the lacteal.

→ Glisson’s capsule: The hepatic lobules are the structural and functional units of the liver containing hepatic cells arranged in the form of cords. Each lobule is covered by a thin connective tissue sheath called the Glisson’s capsule.

→ Chyme: The food mixes thoroughly with the acidic gastric juice of the stomach by the churning movements of its muscular wall and called the chyme.

→ Faeces: The undigested, unabsorbed substances called faeces are temporarily stored in the rectum till defaecation.

→ Micelles: Fatty acids and glycerol being insoluble, cannot be absorbed into the blood. They are first incorporated into small droplets called micelles which move into the intestinal mucosa.

→ Chylomicrons: Micelles are re-formed into very small protein-coated fat globules called the chylomicrons which are transported into the lymph vessels (lacteals) in the villi.