DIGESTIVE SYSTEM OF HUMAN BEING
· Digestion is a biochemical process that occurs in the alimentary canal where complex foodstuff is converted into simple and soluble forms by the action of enzymes secreted by various digestive glands.
· Digestive system of the human being consists of the alimentary canal and associated digestive glands.
· Alimentary canal is about 6-9 meters long, coiled and complex muscular tube that runs from mouth to anus.
· The accessory digestive glands like salivary glands, liver and pancreas pour their secretions into the alimentary canal through their ducts.
· Different regions of the alimentary canal have specialized structures and are modified accordingly to perform different functions.
· Human alimentary canal consists of the following distinct regions:
(i) Mouth and buccal cavity
(ii) Pharynx
(iii) Oesophagus (food tube)
(iv) Stomach
(v) Small intestine
(vi) Large intestine
(vii) Anus
1. Mouth and Buccal cavity
· Mouth is a small transverse aperture, lying below the nose, through which food materials enter the buccal cavity.
· It is anteriorly surrounded by upper and lower lips and laterally by cheeks.
· The lips are fleshy, soft and movable structures used for opening and closing of the mouth, holding the food and also for speaking.
· The mouth leads into a narrow, vertical, slit-like aperture called the vestibule which is externally surrounded by lips and cheeks and internally by teeth and teeth gums.
· The vestibule leads into the buccal cavity which is a spacious chamber situated between the upper and lower jaw.
· The roof of the buccal cavity is formed by the bony palate anteriorly and soft palate posteriorly.
· ‘Palatal ridge’ at the inferior of hard palate helps to keep the food in the cavity during mastication.
· A curved fold of muscle covered with mucous membrane, hanging down from the middle of the free border of the soft palate is called the uvula.
· The lips are fleshy, soft and movable structures used for opening and closing of the mouth, holding the food and also for speaking.
· The mouth leads into a narrow, vertical, slit-like aperture called the vestibule which is externally surrounded by lips and cheeks and internally by teeth and teeth gums.
· The vestibule leads into the buccal cavity which is a spacious chamber situated between the upper and lower jaw.
· The roof of the buccal cavity is formed by the bony palate anteriorly and soft palate posteriorly.
· ‘Palatal ridge’ at the inferior of hard palate helps to keep the food in the cavity during mastication.
· A curved fold of muscle covered with mucous membrane, hanging down from the middle of the free border of the soft palate is called the uvula.
· It closes internal nostrils during swallowing and protects from regurgitation of food towards the nose.
· Oral cavity is internally lined with stratified squamous epithelium and mucous secreting glands.
· Oral cavity is internally lined with stratified squamous epithelium and mucous secreting glands.
· The tongue is a mobile, muscular and triangular structure present on the floor of the buccal cavity. It has roots, body and apex.
· The root is attached to the hyoid bone.
· Dorsal surface of the tongue is rough and consists of the lingual papilla.
· Dorsal surface of the tongue is rough and consists of the lingual papilla.
· It consists of vallate or circumvallate papillae (largest with taste buds), filiform papillae (smallest and sensory), fungiform papillae (with taste buds).
· ‘Frenulum’ connects the inferior of the tongue with the floor of the mouth.
Human TEETH
· Four types of teeth present in adults differ in shape and function.
· Man has 32 permanent teeth set in 2 jaws.
· Each jaw contains 16 teeth.
· Deciduous or temporary teeth [I,C,P,M; 2,1,0,2]
· Deciduous or temporary teeth [I,C,P,M; 2,1,0,2]
· Permanent teeth [I,C,P,M; 2,1,2,3]
· Incisor teeth (I)- Flat, cutting and biting the food.
· Canine teeth (C)- Pointed, tearing and piercing.
· Premolar and molars- Many cusps, crushing, grinding and mastication.
· Incisor teeth (I)- Flat, cutting and biting the food.
· Canine teeth (C)- Pointed, tearing and piercing.
· Premolar and molars- Many cusps, crushing, grinding and mastication.
· The dental formula of milk teeth is:
· Human teeth are thecodont (teeth embedded in jaw sockets), diphyodont (2 times eruption) and heterodont (different in shapes and sizes).
· Milk teeth begin to erupt from 6 months and the eruption is completed by the end of two years.
· Permanent teeth are being replaced by about 6 years and the eruption is completed by the end of 25 years.
· The wisdom teeth are erupted at last from 20-35 years.
· Teeth are formed from epidermis and dermis i.e. enamel is derived from embryonic ectoderm and dentine from mesoderm.
· A typical tooth has three parts:
(a) The crown: the part above the gums.
(b) The neck: the part enclosed by the gums (the region between crown and root)
(c) The root: the part embedded in the socket of jawbones.
· The bulk of the tooth is made up of hard dentine.
· Pulp cavity lies inside the dentine and is lined by a layer of odontoblast cells. It consists of connective tissues, blood vessels and nerve endings.
· Dentine contains many fine canaliculi.
· The crown is covered by enamel and root by cementum.
· Enamel is the hardest substance in the human body.
· Gum strengthens the attachment of teeth on jawbones.
· Blood vessels and nerves pass to the tooth through a small foramen present at the apex of each root.
· Number of roots varies in different teeth, one in incisor and canine, two in premolars and four in molars.
· Teeth are formed from epidermis and dermis i.e. enamel is derived from embryonic ectoderm and dentine from mesoderm.
· A typical tooth has three parts:
(a) The crown: the part above the gums.
(b) The neck: the part enclosed by the gums (the region between crown and root)
(c) The root: the part embedded in the socket of jawbones.
· The bulk of the tooth is made up of hard dentine.
· Pulp cavity lies inside the dentine and is lined by a layer of odontoblast cells. It consists of connective tissues, blood vessels and nerve endings.
· Dentine contains many fine canaliculi.
· The crown is covered by enamel and root by cementum.
· Enamel is the hardest substance in the human body.
· Gum strengthens the attachment of teeth on jawbones.
· Blood vessels and nerves pass to the tooth through a small foramen present at the apex of each root.
· Number of roots varies in different teeth, one in incisor and canine, two in premolars and four in molars.
· Besides the mouth cavity, six other openings open into it.
· These are two openings from the internal ear called Eustachian tubes, two openings from nasal cavities called internal nares, one opening is called glottis leading into the trachea (windpipe) and one opening called gullet (food pipe) leading into the oesophagus.
· It is a wide opening at the back of the mouth. Posteriorly, it leads into two tubes: gullet (food pipe) and glottis (windpipe).
· Epiglottis, present in front of the glottis, closes the nasal cavity during swallowing.
· It is a wide opening at the back of the mouth. Posteriorly, it leads into two tubes: gullet (food pipe) and glottis (windpipe).
· Epiglottis, present in front of the glottis, closes the nasal cavity during swallowing.
· The pharynx consists of three parts i.e. nasopharynx (behind the nose), the oropharynx (behind the mouth) and the laryngopharynx (behind the larynx).
· The nasopharynx is connected with the middle ear by the eustachian tubes.
· The laryngopharynx is communicated with the larynx through the glottis.
· The laryngopharynx is communicated with the larynx through the glottis.
3. Oesophagus
· It is a long, narrow and muscular tube that connects the mouth to the stomach.
· It measures about 25 cm in length.
· It pierces the diaphragm and leads into the stomach.
· The upper end of the oesophagus is closed by the cricopharyngeal sphincter and the lower end by the oesophageal sphincter.
· The upper end of the oesophagus is closed by the cricopharyngeal sphincter and the lower end by the oesophageal sphincter.
· The upper sphincter prevents entry of air while the lower prevents the reflux of gastric contents into the oesophagus.
4. Stomach
· Stomach is a J-shaped, large, muscular, elastic bag situated below the diaphragm.
· It measures about 25-30 cm in length, with a capacity of two litres.
· It is continuous with the oesophagus at the cardiac sphincter and with the duodenum at the pyloric sphincter.
· It has two curvatures - inner lesser and outer greater curvature.
· It is divided into four regions– cardia, fundus, body (corpus) and pylorus (pyloric antrum).
· Cardia: A narrow region at the gastro-oesophagal junction, 2–3 cm wide.
· Fundus: A dome-shaped structure, left of the oesophagus, frequently filled with gas.
· Body (Corpus): Largest portion, responsible for chyme formation.
· Pylorus: A funnel-shaped constricted portion, with a pyloric sphincter that is open when the stomach is inactive and closed when the stomach contains food.
· All gastric regions contain longitudinal folds of the mucosa and sub-mucosa called rugae.
· Cardia: A narrow region at the gastro-oesophagal junction, 2–3 cm wide.
· Fundus: A dome-shaped structure, left of the oesophagus, frequently filled with gas.
· Body (Corpus): Largest portion, responsible for chyme formation.
· Pylorus: A funnel-shaped constricted portion, with a pyloric sphincter that is open when the stomach is inactive and closed when the stomach contains food.
· All gastric regions contain longitudinal folds of the mucosa and sub-mucosa called rugae.
5. Small Intestine
· It is a long and coiled tube extending from the pylorus of the stomach to the ileocaecal junction.
· It is about 6.5 m in length.
· It is divided into duodenum, jejunum and ileum.
(a) Duodenum:
· It is a long and coiled tube extending from the pylorus of the stomach to the ileocaecal junction.
· It is about 6.5 m in length.
· It is divided into duodenum, jejunum and ileum.
(a) Duodenum:
· It is the upper part of the small intestine and C-shaped in structure.
· It receives pancreatic juice from the pancreas and bile juice from the liver through a hepato-pancreatic duct which is guarded by the sphincter of Oddi.
· The wall of the duodenum consists of crypts of lieberkuhn and branched Brunner's glands.
(b) Jejunum:
· Duodenum leads into the jejunum which is a middle part of the small intestine about 7 feet (2.5 m) long.
(c) Ileum:
· Jejunum leads into the ileum which is a highly coiled region of the intestine.
· It is about 15 feet (5 m) long and leads into the large intestine.
· Its wall is thrown into numerous folds called villi to increase the absorptive surface area.
6. Large Intestine
· It is much shorter than the small intestine and is involved basically for the absorption of water and for discharging the undigested wastes.
· It is much shorter than the small intestine and is involved basically for the absorption of water and for discharging the undigested wastes.
· It is subdivided into the caecum, colon and rectum.
(a) Caecum
· Caecum is a large blind sac present where the ileum joins the large intestine.
· In man, it is very small and from it extends a small finger-like vermiform appendix (about 8-10 cm in length) which gets infected during appendicitis.
(a) Caecum
· Caecum is a large blind sac present where the ileum joins the large intestine.
· In man, it is very small and from it extends a small finger-like vermiform appendix (about 8-10 cm in length) which gets infected during appendicitis.
(b) Colon
· Colon is the middle part of the large intestine and is present in the form of an inverted 'U' in the abdominal cavity.
· It has four parts, i.e. ascending, transverse, descending and sigmoid colon.
· Ascending colon passes upwards from the caecum.
· Transverse colon is the horizontal part placed transversely.
· Descending colon passes down from the left side of the abdominal cavity.
· The sigmoid colon (sigma-like) is ‘S’-shaped and continues into the rectum.
(c) Rectum:
· It is a small muscular region at the end of the large intestine.
· It absorbs water and stores undigested food till defaecation.
· It is about 20 cm in length.
7. Anus
· It is the posterior opening of the alimentary canal, about 3.8 cm long and faecal matter is passed through it.
· It is the posterior opening of the alimentary canal, about 3.8 cm long and faecal matter is passed through it.
· The anal canal is provided with two anal sphincters-external and internal anal sphincters.
Physiology of Digestion in Human Beings
· The physiology of digestion is the entire enzymatic reactions of digestion of food in the alimentary canal.Physiology of digestion
· The foods that we intake are in form of complex, insoluble and undiffusible.
· The foods that we intake are in form of complex, insoluble and undiffusible.
· These complex and insoluble components of food can’t be utilized directly by the organisms unless they are converted into simple, soluble and diffusible forms.
· It occurs in the gastrointestinal tract or alimentary canal by hydrolysis and with the addition of enzymes called hydrolases.
· The food contains carbohydrates, proteins, fats, vitamins, minerals and water.
· The food contains carbohydrates, proteins, fats, vitamins, minerals and water.
· The complex macromolecules of food like carbohydrates, proteins and fats are converted into simple food materials like glucose, amino acids and fatty acids and glycerol respectively during digestion.
· The vitamins, minerals and water are simpler foods so they do not require digestion.
Physical or Mechanical Digestion
· In this case, large pieces of food are broken down into smaller pieces by teeth and also by the churning movement of parts of the alimentary canal.
· It occurs inside the mouth and stomach.
Chemical Digestion
· It is the breakdown of food with the help of enzymes in the mouth, stomach and small intestine.
· It is the breakdown of food with the help of enzymes in the mouth, stomach and small intestine.
1. Digestion of Carbohydrates
a. In the oral cavity
· In the oral cavity, food is mixed with saliva.
· The enzyme called salivary amylase (ptyalin) present in saliva converts starch into maltose, isomaltose and a-Dextrins.
· In response to the action of stimuli received from the vagus nerve and secretin, Brunner's glands of duodenum secrete a large amount of enzyme-free, viscous, watery and alkaline mucoid fluid.
· This secretion enables the duodenum to withstand the acidic chyme entering from the stomach until it is neutralized by the alkaline bile and pancreatic juices.
· Mucus secreted by the goblet cells protects the duodenal wall from getting digested. In the duodenum, digestion of most of the nutrients occurs under the action of various enzymes.
· Mucus secreted by the goblet cells protects the duodenal wall from getting digested. In the duodenum, digestion of most of the nutrients occurs under the action of various enzymes.
i. Action of pancreatic juice
· Pancreatic juice contains a-amylase which digests starch into maltose, isomaltose and a-Dextrins.
· Pancreatic juice contains a-amylase which digests starch into maltose, isomaltose and a-Dextrins.
· Bicarbonate of the pancreatic juice neutralizes the HCl of chyme that enters the duodenum.
ii. Action of intestinal juice
· Intestinal juice contains maltase, isomaltase, sucrase, lactase and a-Dextrinase which act as follows.
· As less lactase is produced with advancing age, lactose remains undigested and is fermented in the intestine producing gases and acids.
· Intestinal juice contains maltase, isomaltase, sucrase, lactase and a-Dextrinase which act as follows.
· It causes flatulence, intestinal cramps and diarrhoea.
· So, these persons are suggested to take yoghurt or curd as lactose is fermented into lactic acid in them so does not pose any digestive problem.
2. Digestion of Proteins
· Proteins are broken down into amino acids during digestion.
· Proteins are broken down into amino acids during digestion.
· Enzymes that hydrolyze proteins are called proteases or peptidases.
· Many of these enzymes are secreted in their inactive forms called proenzymes. They get activated only at their site of action.
· Protein digestion does not occur in the oral cavity as saliva does not contain any protein-digesting enzyme.
· Protein digestion does not occur in the oral cavity as saliva does not contain any protein-digesting enzyme.
a. In the stomach
· The action of gastric juice
· The gastric glands of the stomach secrete gastric juice.
· It contains HCl, pepsinogen and prorenin.
Functions of HCl
i. It makes the food acidic.
ii. It kills harmful bacteria and other microorganisms that may be present in food.
iii. It contains inactive enzymes like pepsinogen and prorenin into active forms-pepsin and rennin respectively.
iv. It stops the action of salivary enzymes.
· Once formed pepsin changes pepsinogen into pepsin. Such activation is called an autocatalytic reaction.
Functions of HCl
i. It makes the food acidic.
ii. It kills harmful bacteria and other microorganisms that may be present in food.
iii. It contains inactive enzymes like pepsinogen and prorenin into active forms-pepsin and rennin respectively.
iv. It stops the action of salivary enzymes.
· Once formed pepsin changes pepsinogen into pepsin. Such activation is called an autocatalytic reaction.
· Gastric juice is thoroughly mixed with food until it becomes a semifluid mass called chyme.
· Various reactions in the stomach are:
i. Action of pancreatic juice
· Pancreatic juice contains protein-digesting proenzymes like trypsinogen, chymotrypsinogen, procarboxypeptidase and elastase.
· Bile provides an alkaline medium for various reactions.
· The reactions are:
· Rennin is present only in the infant's stomach. It is absent in adults.
· The invertebrates do not secrete pepsin and rennin.
· The invertebrates do not secrete pepsin and rennin.
ii. Action of intestine juice
· Intestinal juice or succus entericus contains enterokinase, aminopeptidases and dipeptidases. Enterokinase converts trypsinogen into trypsin.
· Intestinal juice or succus entericus contains enterokinase, aminopeptidases and dipeptidases. Enterokinase converts trypsinogen into trypsin.
· The action of other enzymes is listed below.
3. Digestion of Fats
· Saliva contains no lipase.
· Gastric juice contains small amounts of gastric lipase which converts some fats into monoglycerides and fatty acids. So, the digestion of fat mainly occurs in the intestine.
· Bile salts break down fat droplets into many small ones by reducing the surface tension of fat. It is called emulsification.
· Saliva contains no lipase.
· Gastric juice contains small amounts of gastric lipase which converts some fats into monoglycerides and fatty acids. So, the digestion of fat mainly occurs in the intestine.
· Bile salts break down fat droplets into many small ones by reducing the surface tension of fat. It is called emulsification.
· It increases the action of lipase on fat.
· Fat digestion occurs by pancreatic lipase and intestinal lipase.
· Fat digestion occurs by pancreatic lipase and intestinal lipase.
· The pancreatic lipase converts emulsified fats (triglyceride fats) first into diglycerides and then into monoglycerides, releasing a fatty acid at each step.
· The intestinal lipase converts the remaining fats into monoglycerides and fatty acids.
· In the end, all fats are converted into fatty acids, glycerol and monoglycerides.
Digestion of Nucleic Acids
· Nucleic acids are digested in the small intestine by the pancreatic juice and intestinal juice.
· Pancreatic juice contains two nucleases: Deoxyribonuclease (DNase) and Ribonuclease (RNase), which act as follows.
· In the end, all fats are converted into fatty acids, glycerol and monoglycerides.
· Nucleic acids are digested in the small intestine by the pancreatic juice and intestinal juice.
· Pancreatic juice contains two nucleases: Deoxyribonuclease (DNase) and Ribonuclease (RNase), which act as follows.
Accessory digestive glands
· It includes salivary glands, liver and pancreas.
· It includes salivary glands, liver and pancreas.
A. Salivary glands
· Human salivary glands are classified into two categories: major salivary glands and minor salivary glands.
a. Major salivary glands
· In man, the major salivary glands are three pairs; parotid, sublingual and submaxillary or submandibular.
(i) Parotid glands
· These are the largest salivary glands.
· They lie on the sides of the face, just below and in front of the ears.
· The parotid ducts, also called Stenson’s ducts, open into the vestibule opposite to the upper second molar teeth.
· The disease mumps is caused by a viral infection of the parotid glands, causing swelling and pain.
· Human salivary glands are classified into two categories: major salivary glands and minor salivary glands.
a. Major salivary glands
· In man, the major salivary glands are three pairs; parotid, sublingual and submaxillary or submandibular.
(i) Parotid glands
· These are the largest salivary glands.
· They lie on the sides of the face, just below and in front of the ears.
· The parotid ducts, also called Stenson’s ducts, open into the vestibule opposite to the upper second molar teeth.
· The disease mumps is caused by a viral infection of the parotid glands, causing swelling and pain.
(ii) Sublingual glands
· These are the smallest salivary glands and lie under and front part of the tongue.
· The sublingual ducts, also known as ducts of Rivinus, also open under the tongue.
· These are the smallest salivary glands and lie under and front part of the tongue.
· The sublingual ducts, also known as ducts of Rivinus, also open under the tongue.
(iii) Submaxillary or submandibular glands
· These lie at the angles of the lower jaw.
· The submaxillary ducts also called Wharton’s ducts, open under the tongue.
· The parotid salivary glands secrete much of the salivary amylase (= ptyalin).
· Sublingual and submandibular salivary glands secrete salivary amylase and mucus.
· These lie at the angles of the lower jaw.
· The submaxillary ducts also called Wharton’s ducts, open under the tongue.
· The parotid salivary glands secrete much of the salivary amylase (= ptyalin).
· Sublingual and submandibular salivary glands secrete salivary amylase and mucus.
b. Minor salivary glands
· There are numerous small glands situated in the mucus membrane of the lips (labial glands), cheeks (buccal glands), tongue (lingual glands) and palate (palatine glands).
· Some salivary gland tissues may be seen in the palatine and pharyngeal tonsils.
· The secretions of these glands help to keep the mouth moist and provide a protective and lubricant coat of mucus.
· There are numerous small glands situated in the mucus membrane of the lips (labial glands), cheeks (buccal glands), tongue (lingual glands) and palate (palatine glands).
· The secretions of these glands help to keep the mouth moist and provide a protective and lubricant coat of mucus.
B. Liver
· Liver is the largest gland located above the stomach, under the diaphragm.
· Human liver weighs about 1.4 kg in the average adult.
· Liver is the largest gland located above the stomach, under the diaphragm.
· Human liver weighs about 1.4 kg in the average adult.
· The liver of man is divided into four lobes, the right, the left, the caudate and the quadrate lobes.
· The liver of a rabbit is partly divided into five lobes: three lobes on the left side are a small Spigelian, left lateral and the left central, while the two lobes on the right side are caudate and the right central or cystic.
Functions of liver
· Liver is called the master laboratory organ of the body.
· Liver is called the master laboratory organ of the body.
· Its functions are:
(a) Production of bile: Bile is produced in the hepatocytes and is stored in the gall bladder. Gall bladder contracts and pours bile into the duodenum via. the common bile duct.
Functions of bile
i. Bile neutralizes the HCl of chyme.
ii. Sodium glycocholate and sodium taurocholate break the large fat droplets into smaller ones, called emulsification.
iii. Bile salts help in the absorption of fat and fat-soluble vitamins in the small intestine.
iv. Alkaline nature of bile prevents the decomposition of food by preventing the growth of bacteria on it.
v. Bile increases the peristalsis in the intestine.
(b) Liver is involved in glycogenesis and glycogenolysis. In glycogenesis, excess glucose is converted into glycogen in the presence of insulin. In glycogenolysis, glycogen is converted into glucose in the presence of glucagon.
(c) Synthesis of plasma proteins (prothrombin and fibrinogen) and most blood clotting factors from amino acids.
(d) Detoxification of drugs, poisons and toxic substances.
(e) Liver is the main heat-producing organ.
(f) Stores iron, copper, fat-soluble vitamins and some water-soluble vitamins.
(g) Deamination of amino acids: The liver removes the nitrogenous portion from the amino acid. Urea is formed from this nitrogenous portion which is excreted in the urine. It also breaks down nucleic acids to form uric acid which is also excreted in the urine.
(h) Kupffer cells of the liver engulf harmful bacteria, dead cells and worn out RBCs by phagocytosis.
(i) Liver secretes heparin (anticoagulant).
(j) Liver produces RBCs in the embryo (haemopoietic in function).
(a) Production of bile: Bile is produced in the hepatocytes and is stored in the gall bladder. Gall bladder contracts and pours bile into the duodenum via. the common bile duct.
Functions of bile
i. Bile neutralizes the HCl of chyme.
ii. Sodium glycocholate and sodium taurocholate break the large fat droplets into smaller ones, called emulsification.
iii. Bile salts help in the absorption of fat and fat-soluble vitamins in the small intestine.
iv. Alkaline nature of bile prevents the decomposition of food by preventing the growth of bacteria on it.
v. Bile increases the peristalsis in the intestine.
(b) Liver is involved in glycogenesis and glycogenolysis. In glycogenesis, excess glucose is converted into glycogen in the presence of insulin. In glycogenolysis, glycogen is converted into glucose in the presence of glucagon.
(c) Synthesis of plasma proteins (prothrombin and fibrinogen) and most blood clotting factors from amino acids.
(d) Detoxification of drugs, poisons and toxic substances.
(e) Liver is the main heat-producing organ.
(f) Stores iron, copper, fat-soluble vitamins and some water-soluble vitamins.
(g) Deamination of amino acids: The liver removes the nitrogenous portion from the amino acid. Urea is formed from this nitrogenous portion which is excreted in the urine. It also breaks down nucleic acids to form uric acid which is also excreted in the urine.
(h) Kupffer cells of the liver engulf harmful bacteria, dead cells and worn out RBCs by phagocytosis.
(i) Liver secretes heparin (anticoagulant).
(j) Liver produces RBCs in the embryo (haemopoietic in function).
C. Pancreas
· Pancreas is the second-largest gland in the human body.
· It is an irregular, yellowish gland situated at the curvature of the stomach and duodenum.
· Exocrine part of the pancreas is formed by a large number of branching tubules called pancreatic lobules.
· Each tubule has a group of secretory cells that secrete pancreatic juice which is carried by the pancreatic duct to the duodenum. This juice is rich in enzymes like trypsinogen (to digest protein), amylase (to digest carbohydrate) and lipase (to digest fat).
· Similarly, a group of cells are found situated in between acini of the pancreas secrete insulin, glucagon and somatostatin. It constitutes the endocrine portion of the pancreas. It is called islets of Langerhans. So, the pancreas is a mixed gland i.e., both exocrine and endocrine glands.
· Pancreas is the second-largest gland in the human body.
· It is an irregular, yellowish gland situated at the curvature of the stomach and duodenum.
· Exocrine part of the pancreas is formed by a large number of branching tubules called pancreatic lobules.
· Each tubule has a group of secretory cells that secrete pancreatic juice which is carried by the pancreatic duct to the duodenum. This juice is rich in enzymes like trypsinogen (to digest protein), amylase (to digest carbohydrate) and lipase (to digest fat).
· Similarly, a group of cells are found situated in between acini of the pancreas secrete insulin, glucagon and somatostatin. It constitutes the endocrine portion of the pancreas. It is called islets of Langerhans. So, the pancreas is a mixed gland i.e., both exocrine and endocrine glands.
Also, Read our other Notes Related to HUMAN:
- Human Digestive System & Digestion
- Circulatory System
- Respiratory System
- Excretory System
- Reproductive System
- Nervous System
- Limbic System
- Human Sense Organs: EYE
- Human Sense Organs: EAR
- Body Immunity
- Human Diseases