The first part of the alimentary canal is called the mouth. It is located below the nostrils.
Function: It receives food material and passes it into the oral cavity.

The glands that digest food by secreting different types of digestive juices are called digestive glands or nutritive glands. The digestive glands of human body are salivary gland, liver gland, pancreatic gland, stomach gland and small intestine gland.

The long tube extending from the mouth to the anus is called alimentary canal. The various parts of the alimentary canal are described below.
1. Mouth: The first part of the alimentary canal is called the mouth. It is located below the nostrils.
Function: It receives food material and passes it into the oral cavity.
2. Buccal cavity: The next part of the mouth is the mouth cavity. It houses the teeth, tongue, subtongue or salivary glands. The mouth is always moist as it is covered by the mucous membrane oral mucosa. The floor of the mouth is made up of the mylohyoid muscle. At the back of the oral cavity is the soft palate which prevents food from entering the nostrils. Here the food stays for 5-30 seconds.
The tongue has 2000-8000 taste buds. There are five types of taste buds. Sweetness, saltiness, sourness or acidity, savory or umami and bitterness. Taste buds are replaced by new formations every 5-10 days. Each taste bud contains 50-100 taste receptor cells. Taste receptor cells are located in the form of papillae.
Oral function
(i) Tongue helps in tasting and swallowing food.
(ii) Teeth participate in cutting, tearing and grinding of food.
(iii) Salivary glands secrete saliva.
(iv) Lysozyme destroys bacteria.
3. Pharynx: About 12.5 cm long and funnel-shaped part after the oral cavity is called pharynx. It contains holes called gallettes.
Function: Food enters the esophagus from the pharynx through the gullet hole.
4. Esophagus: The muscular tube about 23-25 cm long after the pharynx is called esophagus.
Function: Moves food into the stomach through contractions in the process of peristalsis.
5. Stomach: The J-shaped curved fleshy sac located below the diaphragm and above the abdomen is called the stomach. Its wall is very thick and muscular. Its length is 30.5 cm and width is about 15.2 cm. Stomach consists of five parts. Cardiac stomach, fundus, body, antrum and pyloric stomach.
(i) Cardiac Stomach: The part of the stomach where the esophagus opens is called the cardiac stomach. At the junction of the esophagus and the cardiac stomach is a muscular ring called the cardiac sphincter. The ring of muscles prevents food from entering the esophagus.
(ii) Fundus: The convex part on the left side near the cardiac stomach is called fundus.
(iii) Body: The central region of the stomach posterior to the fundus is called the corpus. It contains food.
(iv) Antrum : The posterior part of the corpus is called antrum. Food is temporarily stored in the antrum before entering the intestine.
(v) Pyloric Stomach: The part of the stomach which opens into the duodenum is called pyloric stomach. At the junction of the duodenum and the pyloric stomach is a muscular ring called the pyloric sphincter. The musculature helps the food to enter the duodenum.
Stomach function
(i) Digested, fatty and partially digested food stays in the stomach for 2-24 hours. Cardiac sphincter prevents retrograde flow of food.
(ii) Oeish released from parietal cells destroys microbes, dissolves mineral salts, decalcifies bones and creates an acidic environment.
(iii) Peristalsis is the process of movement of food in the stomach after 15-20 seconds.
(iv) Food is crushed into a soft paste.
(v) Digestive juices and paste mix to form slimy mucus or chyme.
6. Small Intestine: The 6-7 meter long tube from pyelolic sphincter to ileocolic sphincter is called small intestine. Here the food stays for 3-5 hours. It is divided into three parts. Duodenum, jejunum and ileum.
(i) Duodenum: The first and U-shaped part of small intestine is called duodenum. Its length is 25-30 cm.
(ii) Jejunum: The tubular part about 2.5 meters long after duodenum is called jejunum.
Function: It digests and absorbs food.
(iii) Ileum: The posterior portion of the jejunum is called the ileum. Its length is three-fifths of the entire small intestine. At the junction of the ileum and the colon is a muscular ring called the ileocolic sphincter.
Function: It has villus like fingers. Increases villus absorption area.
7. Large intestine: About 1.5 meters long and thick part extending from the end of the ileum to the anus is called the large intestine. Here the food stays for 1.5-2.0 days. The large intestine has three parts.
Cecum, colon and rectum.
(i) Cecum: The first part of the large intestine is called the cecum. It is sac shaped. Its length is 6 cm and width is 7.5 cm. At the bottom of the caecum is a tube-like outgrowth. It is called vermiform appendix. Inflammation of the appendix caused by bacteria is called appendicitis. It is a passive organ.
(ii) Colon: The tubular portion after cecum is called colon. Its length is 101-114 cm. The colon has four parts. Ascending colon, transverse colon, descending colon and sigmoid colon.
(1) Ascending Colon: This part rises upwards from the cecum. Its length is 13 cm.
(2) Transverse Colon: This part lies transversely. Its length is 38 cm.
(3) Descending Colon: The part of the colon that is downward is called the descending colon. Its length is 25 cm.
(4) Sigmoid colon: The part of the colon connected to the rectum that forms a loop-like structure is called the sigmoid colon. Its length is 25-38 cm.
Function: Colon digests and absorbs food.
(iii) Colon: The sac-like part located at the end of the large intestine is called colon. The lower part of the rectum swells to form an ampulla. Its length is 13 cm. It contains annular sphincter or sphincter.
Functions: Faeces are produced in the large intestine, water is absorbed, food fermentation and digestion takes place.
8. Anus: The opening through which the rectum opens to the outside is called the anus. It is enclosed by two membranes called external and internal sphincters. The internal sphincter is composed of a ring of smooth muscle and contracts involuntarily. The external sphincter is made up of smooth muscle rings and contracts optionally.
Function: Opens and closes controlled by anal nerves and participates in defecation.

The system through which food is taken, digested and absorbed is called the digestive system. The digestive system consists of two parts. Alimentary canal and digestive gland.

The system through which food is taken, digested and absorbed is called the digestive system. The digestive system consists of two parts. Alimentary canal and digestive gland.
Digestive tract
The long tube extending from the mouth to the anus is called alimentary canal. The various parts of the alimentary canal are described below.
1. Mouth: The first part of the alimentary canal is called the mouth. It is located below the nostrils.
Function: It receives food material and passes it into the oral cavity.
2. Buccal cavity: The next part of the mouth is the mouth cavity. It houses the teeth, tongue, subtongue or salivary glands. The mouth is always moist as it is covered by the mucous membrane oral mucosa. The floor of the mouth is made up of the mylohyoid muscle. At the back of the oral cavity is the soft palate which prevents food from entering the nostrils. Here the food stays for 5-30 seconds.
The tongue has 2000-8000 taste buds. There are five types of taste buds. Sweetness, saltiness, sourness or acidity, savory or umami and bitterness. Taste buds are replaced by new formations every 5-10 days. Each taste bud contains 50-100 taste receptor cells. Taste receptor cells are located in the form of papillae.
Oral function
(i) Tongue helps in tasting and swallowing food.
(ii) Teeth participate in cutting, tearing and grinding of food.
(iii) Salivary glands secrete saliva.
(iv) Lysozyme destroys bacteria.
3. Pharynx: About 12.5 cm long and funnel-shaped part after the oral cavity is called pharynx. It contains holes called gallettes.
Function: Food enters the esophagus from the pharynx through the gullet hole.
4. Esophagus: The muscular tube about 23-25 cm long after the pharynx is called esophagus.
Function: Moves food into the stomach through contractions in the process of peristalsis.
5. Stomach: The J-shaped curved fleshy sac located below the diaphragm and above the abdomen is called the stomach. Its wall is very thick and muscular. Its length is 30.5 cm and width is about 15.2 cm. Stomach consists of five parts. Cardiac stomach, fundus, body, antrum and pyloric stomach.
(i) Cardiac Stomach: The part of the stomach where the esophagus opens is called the cardiac stomach. At the junction of the esophagus and the cardiac stomach is a muscular ring called the cardiac sphincter. The ring of muscles prevents food from entering the esophagus.
(ii) Fundus: The convex part on the left side near the cardiac stomach is called fundus.
(iii) Body: The central region of the stomach posterior to the fundus is called the corpus. It contains food.
(iv) Antrum : The posterior part of the corpus is called antrum. Food is temporarily stored in the antrum before entering the intestine.
(v) Pyloric Stomach: The part of the stomach which opens into the duodenum is called pyloric stomach. At the junction of the duodenum and the pyloric stomach is a muscular ring called the pyloric sphincter. The musculature helps the food to enter the duodenum.
Stomach function
(i) Digested, fatty and partially digested food stays in the stomach for 2-24 hours. Cardiac sphincter prevents retrograde flow of food.
(ii) Oeish released from parietal cells destroys microbes, dissolves mineral salts, decalcifies bones and creates an acidic environment.
(iii) Peristalsis is the process of movement of food in the stomach after 15-20 seconds.
(iv) Food is crushed into a soft paste.
(v) Digestive juices and paste mix to form slimy mucus or chyme.
6. Small Intestine: The 6-7 meter long tube from pyelolic sphincter to ileocolic sphincter is called small intestine. Here the food stays for 3-5 hours. It is divided into three parts. Duodenum, jejunum and ileum.
(i) Duodenum: The first and U-shaped part of small intestine is called duodenum. Its length is 25-30 cm.
(ii) Jejunum: The tubular part about 2.5 meters long after duodenum is called jejunum.
Function: It digests and absorbs food.
(iii) Ileum: The posterior portion of the jejunum is called the ileum. Its length is three-fifths of the entire small intestine. At the junction of the ileum and the colon is a muscular ring called the ileocolic sphincter.
Function: It has villus like fingers. Increases villus absorption area.
7. Large intestine: About 1.5 meters long and thick part extending from the end of the ileum to the anus is called the large intestine. Here the food stays for 1.5-2.0 days. The large intestine has three parts.
Cecum, colon and rectum.
(i) Cecum: The first part of the large intestine is called the cecum. It is sac shaped. Its length is 6 cm and width is 7.5 cm. At the bottom of the caecum is a tube-like outgrowth. It is called vermiform appendix. Inflammation of the appendix caused by bacteria is called appendicitis. It is a passive organ.
(ii) Colon: The tubular portion after cecum is called colon. Its length is 101-114 cm. The colon has four parts. Ascending colon, transverse colon, descending colon and sigmoid colon.
(1) Ascending Colon: This part rises upwards from the cecum. Its length is 13 cm.
(2) Transverse Colon: This part lies transversely. Its length is 38 cm.
(3) Descending Colon: The part of the colon that is downward is called the descending colon. Its length is 25 cm.
(4) Sigmoid colon: The part of the colon connected to the rectum that forms a loop-like structure is called the sigmoid colon. Its length is 25-38 cm.
Function: Colon digests and absorbs food.
(iii) Colon: The sac-like part located at the end of the large intestine is called colon. The lower part of the rectum swells to form an ampulla. Its length is 13 cm. It contains annular sphincter or sphincter.
Functions: Faeces are produced in the large intestine, water is absorbed, food fermentation and digestion takes place.
8. Anus: The opening through which the rectum opens to the outside is called the anus. It is enclosed by two membranes called external and internal sphincters. The internal sphincter is composed of a ring of smooth muscle and contracts involuntarily. The external sphincter is made up of smooth muscle rings and contracts optionally.
Function: Opens and closes controlled by anal nerves and participates in defecation.
B. Digestive gland
The glands that digest food by secreting different types of digestive juices are called digestive glands or nutritive glands. The digestive glands of human body are salivary gland, liver gland, pancreatic gland, stomach gland and small intestine gland.

1. Food contains carbohydrates, proteins, lipids, water, vitamins and mineral salts required by the body.
2. The body needs food for growth, development and performance. It keeps the body healthy and strong.
3. Food forms the bones, muscles and tissues of the body.
4. The body needs food to rebuild damaged cells, replace dead cells and create new cells.
5. Food provides energy to the body.

The biochemical process in which the complex food material in living cells is oxidized by the activity of various enzymes and converted into simple, soluble and absorbable material is called digestion. Food consists of 6 ingredients. Proteins, sugars, lipids, water, vitamins and mineral salts. They do not require water, vitamins and mineral salts for digestion. Proteins, lipids and carbohydrates are digested.

Super malaria is a variant of highly drug resistant malaria. It has spread rapidly to Southeast Asian countries. This germ of malaria cannot be controlled by any medicine. The virus was first identified in Cambodia in 2008. Later, the virus spread to Vietnam, Laos and Thailand through mosquitoes. Malaria bacteria in Bangladesh have become resistant to chloroquine. Plasmodium falciparum has become resistant to artemisinin.
The research team of the Oxford Tropical Medicine Research Unit in Bangkok wrote and published in the journal Lancet Infectious Diseases that the control and elimination of fast-spreading super malaria is a major challenge for people in the world today.
This superbug strain of malaria has developed resistance to all drugs. It is a major threat to public health worldwide. About 700,000 people have died worldwide due to drug-resistant bacteria. The death toll will exceed several million by 2050 unless appropriate measures are taken.

1. At the end of zygogy, the merozoites break through the red blood cell wall and come out. This results in destruction of red blood cells and anemia.
2. Liver and spleen become inflamed or swollen in a malaria patient. In this condition, the production of red blood cells in the patient’s body is inhibited. Due to this, the patient becomes anemic.
3. Analytic substance called Lysolecithin is secreted from the spleen of malaria patients. All these substances destroy red blood cells. It causes anemia.
4. The malaria parasite produces a type of antibody called Heamolysin. These antibodies destroy healthy RBCs. The patient becomes anemic.
5. The patient has displeasure and reluctance to take food. It lacks nutrients and does not produce blood cells.

1. Malaria Fever: Human red blood cells secrete toxic substances called hemogenes during the erythrocytic zygogy cycle. Hemogenes cause body temperature to rise and fever with chills. It is called malarial fever. It is a deadly disease. It can cause the death of the patient.
2. Liver cell destruction: Malaria parasite sporozoites enter human liver cells through mosquito saliva. After entering the liver cells, the sporozoites take food and grow in size and transform into cryptozoites. The nucleus of the cryptozoite divides into numerous nuclei. It’s called Saigeant. Cytoplasm accumulates around each nucleus of the zygote to form a cryptomerozoite. Cryptomerozoites break through the hepatocyte wall and come out by destroying the hepatocytes.
Each cryptomerozoite formed invades new liver cells and enlarges by consuming food. Its nucleus divides to form numerous nuclei. It’s called a saizont. Cytoplasm accumulates around each nucleus of the zygote and metamorphoses into a metacryptomerozoite. When the metacryptomerozotes metamorphose, they break through the hepatocyte wall and come out by destroying the hepatocytes. In this way, liver destruction is obtained one after the other.
3. Destruction of red blood cells: Merozoites of the malaria parasite enter human red blood cells through plasma. After entering the red blood cells, the merozoites take food and grow in size and transform into trophozoites. The signet ring is formed from the trophozoite. The shape of the signet ring changes and takes on an indefinite shape like an amoeba. It is called amoeboid trophozoite. The amoeboid trophozoite then changes shape and becomes spherical. Its nucleus divides into numerous nuclei. This condition is called cysont. Cytoplasm accumulates around each nucleus of the zygote to form a merozoite. Merozoites are released by breaking the red blood cell wall and destroying the red blood cell. Each merozoite formed attacks and destroys red blood cells again. Thus the red blood cells are destroyed.
Liver cells and red blood cells are successively destroyed by the malaria parasite, leading to anemia in the host and eventual death of the host.