Digestion and Absorption Class 11 Notes CBSE Biology Chapter 16 (Free PDF Download)

Section–A (1 Mark Questions)

1. Name the anterior and posterior openings of alimentary canal.

Ans. The anterior opening of alimentary canal is mouth. Its posterior end is anus.

2. Which structure prevents the entry of food into respiratory tract?

Ans. Epiglottis prevents food items from entering the trachea or the airway.

3. What are the irregular folds formed by mucosa layer of the stomach wall?

Ans. In stomach the mucosa forms irregular folds called rugae.

4. Which enzyme is activated by bile salts?

Ans. Bile salts activate the enzyme lipase and also increase the surface area accessible to these lipid hydrolysing enzymes. 

5. Where is vomit canter located in medulla?

Ans. The vomit centre is located in the medulla. 

Section–B (2 Mark Questions)

6. Answer the following questions:

(i) Name the structural and functional units of liver.

(ii) How many salivary glands are present in humans?

Ans. (i) Hepatic lobules are the structural and functional units of the liver.

(ii) There are three pairs of salivary glands present in human body.

7. Explain the dental formula in an adult human.

Ans. The dental formula in an adult human is 2,1,2,3/2,1,2,3. Here, in the upper half jaw 2 represents the two incisors present in front of the mouth next to which is a single sharp tooth called canine. After canine is broad premolars and molars which are 2 and 3 in number respectively.

8. What is indigestion? 

Ans. Indigestion, is a type of a functional disorder, caused by the abnormal functioning of the digestive system or gastrointestinal organs. In this condition, the food is not properly digested leading to a feeling of fullness. The causes of indigestion are inadequate enzyme secretion, anxiety, food poisoning, overeating, and spicy food.

9. Write a short note on vermiform appendix.

Ans. The vermiform appendix is part of the alimentary canal. The vermiform appendix is also known as the caecal appendix. It is a finger-like, blind-ended tubular projection connected to the caecum. Therefore, it is a part of the large intestine. It is a vestigial organ which is closed at one end and attached to caecum at the other end. It can get infected and lead to a disease known as appendicitis.

10. Answer the following question in one word:

(i) End product of protein digestion

(ii) Site from where the carbohydrate digestion begins

Ans. (i) End product of protein digestion is amino acids.

(ii) Carbohydrate digestion begins in oral cavity. 

11. In the complete absence of enterokinase, digestion of chyme proteins is not possible. Why?

Ans. In the complete absence of enterokinase, the duodenal digestion of chyme proteins is not possible. Enterokinase converts proenzyme trypsinogen into trypsin, which in turn activates the other enzymes in the pancreatic juice and digest proteins.

PDF Summary - Class 11 Biology Digestion and Absorption (Chapter 16)

Human Physiology is the branch of biology that helps in the study of various life processes. Various life processes include digestion, respiration, blood circulation, excretion, locomotion and movement, neural control and coordination, etc. William Harvey is known as the father of modern physiology. 

Food is an important source of nutrients and helps in providing energy for the growth, development, maintenance, and activities of the body in an organism. Nutrients are the chemicals found in food while the process of obtaining food is called nutrition. 

Constituents of food include fats, carbohydrates, proteins, vitamins, minerals, etc. Water is also an important source for performing various metabolic functions of the body and prevents dehydration in the body. 

Digestion is the process of converting complex food particles into simpler food particles or compounds that are easily soluble and can be absorbed. The process of digestion includes two processes that are mechanical processes and biochemical processes. The mechanical processes involve the breakdown of complex food particles into simple food particles that include tearing, cutting, chewing, crushing, rolling, pressing, etc while the biochemical processes involve the breakdown of covalent bonds of the inorganic food molecules and convert it into the simple food molecules by the process of hydrolysis. 

16.1 Digestive system: The human digestive system is composed of various organs that include the well-developed alimentary canal, and associated glands.

16.1.1 Alimentary canal: It is a long, muscular coiled tube that is about 6m to 9 m in length and runs from the mouth to the anus. Its inner walls are lined by glandular epithelium extending from mouth to anus. It is lined by glandular epithelium and is composed of various organs staging from the mouth, oral cavity or buccal cavity, pharynx, esophagus, stomach, small intestine, large intestine, and lastly the anus. The important glands are associated with the alimentary canal by a series of ducts. These glands include salivary glands, gastric glands, liver, pancreas, gallbladder, and intestinal glands. 

Mouth and Oral cavity: The first part of the alimentary canal is the transverse slit-like opening called the mouth and around which two lips are present. The mouth consists of the oral cavity while the roof of the mouth is called the palate. The oral cavity consists of a pair of jaws called the upper maxilla (upper jaw) and lower mandible (lower jaw). The lateral walls of the oral cavity are found in the cheeks. At the hind region of the roof, there is a small extension which is finger-shaped called uvula, while the stratified squamous epithelium is found in the buccal cavity that helps in secreting the mucous resulting in the lubrication of the cavity. 

At the floor of the oral cavity there lies a muscular tongue which is attached with the help of the thin fold of the frenulum. They perform various functions that include ingestion, swallowing, and chewing of food materials and also constitute of taste buds that help in recognizing mainly four types of tastes that include sweet, sour, bitter, and salt, in the undigested food materials. The sensation of taste occurs when the moist food comes in contact with the taste buds.

Teeth: The specialized cells are responsible for the masticatory apparatus in the skin that covers the jaw. The number of teeth present, their arrangement, and shapes together dentition. In humans, the dentition found is of three types that include thecodont, heterodont and diphyodont. The thecodont dentition includes the presence of teeth sockets (cavities) in the upper and lower jawbones. There are 32 teeth present in the mouth of an adult human being arranged 16 in each jaw. 

The teeth are of four types according to the functions they perform which include Incisors, Canines, Premolars, and Molars. The condition where there is the presence of various types of teeth is called heterodont dentition.

Incisors: They are responsible for the cutting of food into smaller pieces. They are chisel-shaped having sharp cutting edges.

Canines: They are responsible for tearing food and are found to be dagger-shaped. 

Premolars and molars are strong teeth present at the end of the jaws and are responsible for crushing and grinding the food. 

In the case of the man, the last four molars, two each from the upper and the lower jaws will appear only after the person has reached the age of 17 or 18. These four molar teeth are known as the wisdom teeth.

In the whole life of man, there are two sets of teeth that appear, they are the milk teeth and permanent teeth. This condition is called diphyodont dentition. 

Milk teeth appear in childhood, they are temporary and weak. They do not have molars and premolars are 20 in number, each jaw contains 10 teeth. The arrangement of teeth in the jaws and their number comes under the dental formula. 

I - 2/2 C - 1/1 P - 2/2 M - 3/3 = 16 x 2 = 32 

For milk dentition, the dental formula is 

I - 2/2 C - 1/1 P - 0/0 M - 2/2= 10 x 2 = 20 

The teeth are covered by enamel which is made up of calcium salts and is a non-living substance. The enamel is the hardest bone of the body are is composed of calcium, calcium carbonate, and phosphate. The teeth present in the buccal cavity helps in the mastication of food. 

Pharynx: The muscular passage which is funnel-shaped and helps in both the process of respiration and digestion. The buccal cavity is extended into a pharynx while the nasal cavity from above opens into it. Then it will open into the esophagus and trachea posteriorly. The glottis is the opening of the pharynx into the trachea and is always open during the process of respiration. The glottis is covered by the flap-like structure called epiglottis which helps in preventing the food particles to move into the windpipe while swallowing instead of the food pipe and it closes by uvula into the nasal cavity.

Esophagus: The esophagus is a long tube made up of muscles that are about 30 cm long and helps in connecting the pharynx to the stomach. This tube passes from the neck, thorax and pierce the diaphragm (it is a muscular wall that partitions the thorax from the abdomen). The contraction and relaxation of the esophagus in a wave-like manner is called peristalsis which helps the food to reach the stomach. The opening of the esophagus in the stomach occurs with the help of the gastro-oesophageal sphincter muscles. 

Stomach: It is the biggest part of the alimentary canal having a C-shaped structure that is present in the upper region of the abdominal cavity below the diaphragm. It consists of three parts that include fundus, cardiac, and pylorus. 

The fundus region is located near the cardiac region where the esophagus opens. It helps in taking air into the stomach while swallowing food. 

The cardiac is the middle region that helps in storing food. 

Pylorus or antrum is the narrow, posterior region that opens into the small intestine with the help of an opening called a pyloric orifice that is surrounded by the pyloric sphincter which is a ring-shaped muscle. The relaxation of the sphincter will lead the food to the small intestine. There are various gastric glands present in the wall of the stomach that help in the secretion of gastric juices. When the stomach is empty, then the mucous membrane surrounding it will become folded resulting in the structure called rugae that leads to the lumen of the stomach. 

Small Intestine: It is the longest part of the alimentary canal and is found to be coiled, narrow, and tubular situated in the abdominal region.

The length of the small intestine is about 7 to 9 m while its diameter is about 2.4 cm. The small intestine is divided into three parts, duodenum, jejunum, and ileum. 

Duodenum: It is the first region of the small intestine which is U-shaped. In includes, the common opening of the liver and pancreas. 

Jejunum: It is the region after the duodenum and is found to be much longer than that. Ileum: It is the last and the longest region of the small intestine. Its length is about 7m while its diameter is about 2 to 3 cm. This region is highly coiled and opens into the lower right region of the abdominal cavity of the large intestine. The jejunum and ileum together constitute the mesenteric part of the small intestine. The small intestine is responsible for most of the digestion and absorption.

Large intestine: The small intestine is then followed by the large intestine. It is shorter but wider than the small intestine, having 2 m in length. It is divided into three regions- Caecum, colon, and rectum. 

The caecum is a small pouch present in the case of humans while in the case of horses and ass it is very large.  In the caecum, a finger-like shape is found which is termed the vermiform appendix that is found to be non-functional and thus comes under the category the vestigial organ. 

The colon is the largest part of the large intestine. 

The colon is further divided into the ascending colon (running upwards), transverse colon (running across the abdomen), and descending colon (running downwards). 

The descending colon is then followed by the rectum that helps in the storage of feces and is then opened via the anus which is surrounded by the voluntary sphincter muscle.

Histology of the human alimentary canal: The wall of the human alimentary canal that runs from the esophagus to the rectum is composed of 4 major layers:

(i) Serosa 

(ii) Muscularis 

(iii) Submucosa 

(iv) Mucosa. 

Serosa is made up of fibers and composes the outermost layer of the alimentary canal. It is made up of thin mesothelium along with some connective tissue. 

Muscularis is the layer that is found outside the submucosa. It is made up of two layers that include an inner layer of circular muscles and an outer layer of longitudinal muscles while in some regions an oblique muscle layer is observed. 

Submucosa: This layer is found outer to the mucosa and is made up of the loose connective tissue layer along with the blood and lymph vessels where nerves are also present. In the submucosal region, the duodenal glands are also found. 

Mucosa: It lines in the innermost layer of the lumen of the alimentary canal that provides moisture and is friction-resistant. The epithelium consists of the secretory cells and the absorptive cells. The epithelium consists of the goblet that helps in the secretion of the mucous acting as a lubricant and results in the protection of the epithelium from damage and digestion. The rugae are present in the stomach that are made up of the mucosa and submucosa folded together when the stomach is empty. These folds will help the stomach to stretch and then disappear when the food reaches the stomach. In the mucosal region of the small intestine, there are a number of finger-like projections present in their surface called villi. 

Structure of the villi: In the mucosal region of the small intestine, there are a number of finger-like projections present in their surface called villi. Each villus is composed of a network of blood capillaries, a network of lymph vessels, and an outer layer of columnar epithelial cells. 

A large central lymph vessel is found at the center of each villus called a lacteal. The epithelial cells of the villi consist of short protoplasmic bristle-like projections that are around 2000 to 3000 called microvilli or brush borders. The main function of villi is to increase the surface area of the intestinal mucosa and thus results in increasing the rate of absorption of nutrients. The small intestine has a total surface area of about 200 sq.m. The walls of the epithelial cells of the villi help in absorbing the digested food.

16.1.2 Digestive glands: The digestive glands include those glands that are the part of the alimentary canal and help in the process of digestion of food materials. These glands are salivary glands, liver, and pancreas.

Salivary glands: They are the digestive glands that result in the secretion of the saliva and are found in the oral cavity. In humans, salivary glands are three in pairs:

(i) Parotid glands 

(ii) Sublingual gland

(iii) Submandibular or submaxillary glands. 

Parotid glands are large and are found just below and in front of the ears. 

Sublingual glands are located on the floor of the mouth, below the tongue. 

Submandibular glands or submaxillary glands located below the angles of the lower jaw bone.

These glands are responsible for the secretion of the saliva and through the salivary ducts, it reaches the oral cavity. The saliva is a clear watery fluid and in humans, it is secreted per day to about 1.5 liters. It is alkaline in nature and is composed of water 99.5% and other substances 0.5% that include the digestive enzymes, electrolytes, mucin, and inorganic salts. In man, starch digesting enzymes are present in the saliva called the salivary amylase along with an antimicrobial agent known as lysozyme. The role of salivary amylase is to digest the starch and glycogen and convert them into the maltose. It is not found in the case of cows, buffalo, goats, tigers, lions, etc. The electrolytes like Na+, K-, Cl-, HCO3, etc are found in the saliva that are formed from the blood plasma, serous fluid, and mucous. 

Functions of saliva are: 

(i) It prevents those activities in the oral cavity that leads to deterioration. 

(ii) It removes the pathogenic bacteria.

(iii) Saliva contains thiocyanate ions and Proteolytic enzymes that help in destroying bacteria found in the oral cavity.

(iv) The proteins present in the saliva help in destroying bacteria found in the oral cavity that leads to dental caries. 

Liver: It is the largest gland in the human body whose weight is about 1.2 to 1.5Kg in adult men having a dark chocolate color. It is found in the abdominal region at the right upper part that is just below the diaphragm. The liver is bilobed having two lobes that are small left lobe and a large right lobe. The lobules make the structure of the liver and perform functions. They are surrounded by a capsule called Glisson’s capsule. The lobules consist of the Hepatic cells, Kupffer cells, and blood-filled spaces called sinusoids. Hepatic cells result in the secretion of bile. Kuppffer’s cells help in the digestion of bacteria, damaged blood cells, foreign particles, etc. The liver secretes bile juice that is greenish in color, the alkaline in nature, consisting of various substances that include pigments, mucin, cholesterol, phospholipids, water, and bile salts. Bile pigments are of two types: Biliverdin and bilirubin.

Biliverdin is a green pigment while bilirubin is a reddish yellow pigment.

Bile salts include sodium taurocholate and sodium glycocholate that help them in digesting the fats and also absorbing the fat-soluble vitamins A, D, E, and K. 

In bile enzymes are absent. It then passed into the hepatic ducts. The gallbladder results in the formation of the cystic. The hepatic and the cystic duct together form a common bile duct and then join with the pancreatic duct that results in the formation of the common hepatopancreatic duct. The sphincter that surrounds the common duct is called the Sphincter of Oddi.

Pancreas: They are the part of the digestive gland that are elongated and are found in the bend of the duodenal loop. It is the second-largest gland in the human body after the liver and is about 12-15 cm long having a reddish-yellow color. They help in the secretion of the pancreatic juice which is a clear, watery, alkaline fluid consisting of a large number of enzymes that help in the digestion of the starch, proteins, lipids, and nucleic acids. The pancreatic juice is then passed into the pancreatic duct or Duct of Wirsung that later combines with the common bile duct and results in the formation of the hepatopancreatic duct which opens into the duodenal loop. The pancreas is composed of parts: the Endocrine and exocrine parts. The exocrine part is composed of glandular chambers called acini or alveoli that help in the secretion of the alkaline pancreatic juice having enzymes. 

The endocrine part is composed of Islets of Langerhans that are scattered patches of cells and result in the secretion of the hormones insulin and glucagon. 

It is composed of three types of cells:

(i) Alpha cells-secrete glucagon 

(ii) Beta cells secrete insulin 

(iii) Delta cells secrete somatostatin. 

16.2 Digestion of food: The process of digestion involves two processes, mechanical and chemical digestion. 

Mechanical digestion: It is the process of breaking down food into the much simpler compounds by the process of mastication, insalivation, and lastly by the peristaltic movement of the wall of the alimentary canal.

Chemical digestion: The digestion occurs with the help of various chemicals that are secreted by the mouth region, mainly saliva which gets mixed with food particles and helps in partial digestion. The saliva is composed of various substances that include mucin, thiocyanate,  lysozyme, and ptyalin that result in the complete digestion. 

Mucin is a glycoprotein that helps in providing the lubrication to the food particles and helps them in swallowing food. 

Lysozyme is bactericidal that kills the harmful bacteria. Saliva consists of Ptyalin that helps in digesting starch and converts it into the maltose. In the mouth, only 30% of starch is digested. 

Ptyalin is found in the saliva of the humans due to the food which is consumed is mainly composed of starch. The function of Ptyalin is to digest only ripe and cooked starch while the raw starch cannot be digested by it. 

The teeth and tongue are responsible for the mastication, lubrication, and adhesion of food into the bolus after mixing with the saliva and are then transferred into the pharynx by the process of swallowing or deglutition. The process of swallowing is a reflex action that occurs along with the peristaltic wave and results in the pushing of food into the various parts of the alimentary canal. 

Bolus moves to the esophagus and with the help of the peristaltic movement in the esophagus, the food then enters into the stomach via the gastro-oesophageal sphincter.

Digestion in the stomach: 

The process of digesting the food particles in the stomach is known as gastric digestion. The bolus after salivation enters the stomach and results in the straightening of its walls called rugae. These walls then crush, knead, and churns the food particles and mix them with the gastric juices that are released by the gastric juice secreted by the gastric glands. 

There are four types of cells that produce the secretion of the gastric glands and is located all over the inner region of the stomach: 

Mucous neck cells or Goblet cells: They help in secreting the mucous which is alkaline in nature and helps in protecting the epithelium from the action of the hydrochloric acid. These cells are located in the fundic, cardiac, and pyloric regions of the stomach. 

Parietal cells or oxyntic cells: they are also located in the fundic, cardiac, and pyloric regions of the stomach. They result in the secretion of the hydrochloric acid which in turn results in the activation of the pepsin enzyme from the gastric glands that helps in the digestion of proteins. Their function is to destroy the micro-organisms that have entered along with the food. 

Chief cells (Zymogenic cells or peptic cells): They help in the secretion of the pepsin enzyme that are found in the fundic region. 

G cells: They are found in the fundic, pyloric, and gastric regions of the stomach that result in the secretion of the gastrin enzyme and are responsible for the secretion of hydrochloric acid. 

The secretion of gastric glands together constitutes the gastric juices that are acidic in reaction and contains dilute HCl. The gastric juice is composed of about 99% of water and the remaining amount is of pepsinogen, gastric lipase, prorenin, mucous, bicarbonates, HCl, etc. 

Food is stored in the stomach for about 4 to 6 hours. The food will become acidic after it undergoes gastric digestion resulting in the formation of the semi-digested and paste-like form known as chyme. The chyme is then transferred through the pyloric sphincter of the stomach little by little into the duodenum of the small intestine. 

The protection and lubrication of the mucosal epithelium are due to the presence of mucus and bicarbonates in the gastric juice. They protect the mucosal epithelium from getting destroyed under the effect of the highly concentrated HCl. 

Digestion in the intestine: The chyme formed enters the small intestine where it first reaches the duodenum. In the duodenum, the process of distension occurs and it results in an increase in the osmotic pressure. The bile secreted from the liver results in the neutralization of the acidic chyme. It then passes to the alkaline part of the pancreatic juice and then the mucus is secreted by the Brunner's gland. In the jejunum and the ileum region of the small intestine, the food gets mixed with bile, mucus, and pancreatic juice along with the intestinal juice called succus entericus. Here the complete digestion occurs due to the presence of the chemical action of various digestive enzymes in the intestinal juice and also through the peristaltic and pendulous movement of the intestine. 

Intestinal glands are of two types: Crypts of Lieberkuhn and Brunner’s gland.

Crypts of Lieberkuhn: They are the invaginations of the mucosa located in the small intestine in between the villi and opens at the base of the villi. They are composed of three types of secreting cells:

Goblet cells: responsible for the secrete mucus 

Paneth cells: responsible for the secrete large number of digestive enzymes 

Enterocytes: responsible for the secreted water and electrolytes. 

Brunner’s gland: They are the tubular glands located in the submucosa of the duodenum.

They result in the secretion of a viscous, alkaline, enzyme-free, and watery fluid called mucoid fluid that helps the duodenum to withstand the acidic chyme that enters through the stomach and is then neutralized by the helps of the alkaline pancreatic juice and bile. 

Both the intestinal and Brunner’s gland secretion together are called succuss entericus having a slightly straw-colored alkaline fluid along with a number of enzymes, inorganic salts, and mucus. The food after it is fully digested will form a semifluid known as chyle. From the chyle, the digested food then undergoes absorption.  

The action of pancreatic enzymes are 

Intestinal enzymatic actions are

The macromolecules break down in the duodenum region while their absorption occurs in the jejunum and ileum region of the small intestine. The food particles that remain undigested will move into the large intestine via the ileocaecal valve. 

Large intestine: 

The large intestine is the region where the absorption of liquids occurs. It involves the absorption of water and minerals while its walls secrete mucus for the process of adhering and lubrication. The food that remains undigested will result in the formation of the solid wastes called feces that are stored temporarily in another organ called the rectum and lastly, it is moved out from the anus of the body by the process of defecation. 

16.3 Absorption of digested food: The process is performed by an alimentary canal which helps in taking up the digested food products and other nutrients and transferring them into other cells or tissues of the body is called absorption. The products formed after digestion include glucose, fatty acids, amino acids, glycerol, pyrimidines, purines, mineral salts, water, vitamins, etc. The main site where the food is digested occurs in the small intestine. The major process of absorption occurs in the ileum of the small intestine. The digested products in the small intestine are absorbed with the help of the microvilli of the absorptive cells while the absorption of water occurs in the large intestine. 

The absorption of the digested food occurs via passive absorption or active absorption or by facilitated transport mechanisms. 

Simple diffusion: It helps in the absorption of amino acids, glucose, and some of the electrolytes like chloride ions. 

Facilitated diffusion occurs with the help of carrier ions like Na+ that helps in the absorption of fructose and some amino acids.

On the basis of the osmotic gradient, the transport of water occurs. 

When the transport is against the concentration gradient, it is called active transport. To transport by this method, energy is required in the form of ATP, it results in the absorption of amino acids, electrolytes like Na+, monosaccharides (glucose). The fatty acids and glycerol are found to be insoluble and cannot be absorbed by the blood. So, they first need to break down into smaller droplets called micelles which then move into the intestinal mucosa, where they are converted into the small protein-coated fat globules (Chylomicrons) and are then transferred to the lymph vessel in the villi. Then from there, it reaches the bloodstream. The absorption of food occurs in the mouth, stomach, small intestine, and large intestine while most of the absorption occurs in the small intestine. The process of transfer of absorbed food into different tissues via blood is called assimilation. The food which is undigested is stored in the form of solid waste (feces) in the rectum which is then removed out after the process of defecation which occurs as the aneural reflex. 

Table 16.1. The summary of Absorption in different parts of the digestive system

16.4 Disorders of the digestive system: 

The intestinal tracts may sometimes be infected by certain bacterias or viruses resulting in inflammation. The infections may also occur due to the presence of various parasites of the intestine that include roundworm, tapeworm, threadworm, pinworm, hookworm, etc. 

The common disorders occurring in the digestive system are vomiting, jaundice, diarrhea, indigestion, constipation, etc. 

1. Jaundice: It occurs due to the accumulation of bile pigments in the blood that will result in yellowing of the skin, eyes, and mucous membrane. 

2. Vomiting: It occurs at blockage of gut or reverse peristalsis where the contents of the stomach are ejected through the mouth. It is a reflex action that is under the control of the vomiting center present in the medulla oblongata of the brain. Vomiting occurs after the feeling of nausea arises. 

3. Diarrhoea: The watery feces that occur frequently are the symptoms of diarrhea that occur due to the non-proper absorption of water. This leads to the abnormal bowel movement frequency and also the liquidity of the fecal discharge and reduces the absorption of food.

4. Constipation: When the amount of water absorbed is high in the large intestine, then it will result in the formation of the fecal matter that is extremely dry and hard leading to the dry and hard muscle of the colon of the large intestine which then becomes incapable of their normal peristaltic movements and remains contracted. This leads to the storage of feces in the rectum and leads to defecation that occurs at prolonged intervals. This condition is called constipation. To avoid constipation, the food that is to be eaten must be right in cellulose fibers. There are two conditions of irregular defecation that are Constipation and diarrhea. 

5. Indigestion: The condition occurring due to improper digestion leading to the feeling of fullness. Indigestion occurs due to various factors that include inadequate enzyme, anxiety, secretion, food poisoning, spicy food, overeating, etc. 

FAST TRACK REVISION: 

Food is a substance that is made up of nutritive and nonnutritive substances and is highly useful for the process of the growth, development, maintenance, and activities of an organism. 

Digestion is the process that helps in converting the complex food materials into simple, absorbable, and soluble forms. 

The Human digestive system is composed of a well-developed alimentary canal, along with its associated glands. The alimentary canal is surrounded by the glandular epithelium and comprises a mouth, oral cavity or buccal cavity, pharynx, esophagus, stomach, small intestine, large intestine, and anus. 

In humans, the dentition in humans is described as the thecodont, heterodont, and diphyodont. 

The organ that is common in both the respiratory and digestive systems is Pharynx which is a muscular, funnel-shaped passage. 

The food enters the stomach through the process of the peristaltic movement that occurs in the walls of the esophagus. 

The wall of the stomach consists of gastric glands that help in the production of gastric juice.

The duct from the pancreas and liver opens into the duodenum of the small intestine. 

The intestinal juice called succus entericus helps in the complete digestion of the food. 

The large intestine are responsible for the absorption of water and results in the storage of undigested food in the solid form inside the rectum and then is excreted out through the anus. 

The salivary glands, liver, and pancreas are those glands that are responsible for the process of digestion. 

Revision Notes for CBSE Class 11 Biology Chapter 16 - Free PDF Download

CBSE biology class 11 chapter 16 notes are explained in simple steps here. These explanations are easily understood by us and clear all doubts at once. Class 11 biology Digestion and Absorption revision notes will make the subject interesting and fun to learn. Preparing these solved questions will help with homework and exams as well.  CBSE biology class 11, chapter 16 notes provide for easy exam preparation and completing the task. The solution provided will help to solve any question related to Economics of course 12. CBSE biology class 11, chapter 16 notes is a great chapter explaining finance and accounting basics. Class 11 biology Digestion and Absorption revision notes is an easy and scoring chapter. 

Class 11th Biology Chapter 16 Notes

The branch of biology that deals with the study of human life is called physiology. The main physiological process of human life is digestion and absorption. Locomotion, mobility, exchange of chemicals and gases, neural and chemical coordination are a part of digestion and absorption. The father of physiology is William Harvey. We consume food and various nutritional supplements every day to provide energy to our body. Food helps our body to grow and perform multiple activities. The physiological process by which the organs of our body consumes food is called nutrition. The food contains many essential fibres, proteins, carbohydrates, good fatty acids which our body requires in everyday life. Breaking down food in our stomach and absorbing all the vital nutrients is called digestion. Some of the body organs help us in this whole process of digestion and absorption. They are explained in detail in the provided notes.

Class 11 Chapter 16 Biology Revision Notes

Class 11 biology Digestion and Absorption revision notes depict that digestion and absorption include alimentary canal, a long channel starting from our mouth and ending in the anus. It consists of the oesophagus, stomach, large intestine, small intestine, parts of our mouth, salivary gland, and gallbladder. Notes of Digestion and Absorption Class 11 consist of a vivid description of all these organs and their functions and their working abilities. CBSE biology class 11 chapter 16 notes also provides a detailed description of the parts within our mouth and all the salivary glands and their importance. This chapter is nicely explained with detailed diagrams of all the organs.