Digestive System Full Information, Alimentary Canal and Accessory Organs, digestive system diseases, digestive system for kids, digestive system organs, digestive system parts, digestive system process, digestive system anatomy,
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Digestive System : Your digestive system is made up of the gastrointestinal tract and your liver, pancreas, and gallbladder. The gastrointestinal tract is a series of hollow organs that are interconnected from your mouth to your anus.
The organs that make up your gastrointestinal tract. The order in which they are connected include your mouth, esophagus, stomach, small intestine, large intestine, and anus.
It takes about 24 hours for your food to make its way through the nine-meter-long digestive system. In its journey, it is mixed with acids and digestive juices, and then squeezed and squeezed until all the nutrients needed by the body are absorbed. Then, the smelly residue, along with billions of dead bacteria, are ready to be passed out of the body.
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Introduction Digestive System :
It is also called gastro intestinal tract or alimentary canal with some accessory glands. The digestive system is formed by the alimentary (muscular) canal, digestive glands and accessory organs.
Digestive System Organs :
- The Alimentary Canal
- Accessory Organs and Glands
The Alimentary Canal : It is made up of the mouth (with tongue and teeth) and the salivary gland pharynx (throat), esophagus (food pipe), stomach, small intestine, large intestine, rectum and anal canal. The alimentary canal is made up of smooth muscles that begins at the mouth and ends at the anus. The layers of the alimentary canal are mucous, muscular, sub-mucosa and peritoneum.
Accessory Organs and Glands : These include the tongue, teeth, salivary glands, liver, pancreas, gall bladder, and bile path. All the above organs work together as they are physically and physically linked together. It helps in effective digestion and absorption of food.
Layers of The Alimentary Canal :
- Sub mucosa
- Muscle Layers
Mucosa – It is composed of squamous or columnar epithelium in different parts of the canal. Loose connective tissue beneath the epithelium supports the blood and lymph vessels and nerve fibers. It contains goblet cells secreting mucus that lubricate the wall of the alimentary canal. specialized glands Which secrete various digestive juices into the lumen of the tract (canal). Digestive juices include………..
- 1) Saliva.
- 2) Gastric Juice.
- 3) Bile Juice.
- 4) Pancreas Juice.
- 5) Intestinal Juice.
Sub mucosa – It is made up of loose connective tissue containing blood vessels, lymph vessels, nerves and lymphoid tissues.
Muscle Layers – This layer is made up of smooth (involuntary) muscles. The outer layer is made up of longitudinal muscles and the inner layer is made up of circular muscles. Muscles are supplied by blood vessels, lymphatic vessels, and both sympathetic and parasympathetic nerves. contraction and The relaxation of this muscle produces peristalsis which helps in mixing the food with the digestive juices as well as pushing it forward.
Peritoneum : Digestive System
It is a serous membrane composed of two layers of loose connective tissues lined by simple squamous epithelium. The two layers are 1) The parietal layer lines the abdominal wall 2) The visceral layer that covers the organs of the digestive system within the abdominal and pelvic cavities. The visceral peritoneum is arranged in such a way that it covers the organs from above, behind and below. The parts covered are as follows.
- The pelvic organs are covered only better.
- The stomach and intestines are covered from behind by a double layer of peritoneum (called the mesentery). The stomach and intestine are connected to the back wall of the abdomen by the mesentery. The part of the peritoneum that extends beyond the greater curvature of the abdomen is called the greater omentum.
- Pancreas, spleen, kidney adrenal glands are covered from the anterior side hence they are retro-peritoneal organs. The peritoneum covers the liver from above and is attached to the lower surface of the diaphragm.
- The main blood vessels and nerves are close to the back wall of the abdomen. They send branches to the organs between the layers of the peritoneum.
Nerve Supply to the Alimentary Canal and Other Organs of Digestion :
Parasympathetic – This is a pair of cranial nerves called the vagus. The terminal part of the system is supplied by the sacral nerve. The stimulation causes the secretion of digestive juices.
Sympathetic – It is supplied by the thoracic and lumbar spinal nerves. The secretion of juice decreases due to stimulation. The secretion of digestive juices and peristalsis are controlled by the sympathetic and parasympathetic nerves.
Blood Supply of Digestive System :
The arteries are the esophageal, celiac, superior mesenteric, inferior mesenteric, superior and inferior rectal arteries. The above arteries begin with the aorta or its branches. The veins carry the esophageal, portal hepatic and internal iliac veins. Blood from the digestive organs and finally they join the inferior vena cava.
Accessory Organs of The Digestive :
Mouth or Oral Cavity – The walls of the oral cavity are formed by.
- a) Anterior – lips and teeth
- b) Posterior – pharynx (throat)
- c) Superior – hard palate
- d) Inferior – tongue and soft tissues
- e) Lateral – muscles of the cheeks and teeth
Cells in the oral cavity are stratified squamous epithelium. Mucous secreting glands are also present in the mucous membrane. The palate forms the roof, in which the front is hard and the back is soft. The uvula is a fold of muscular and mucous membrane between the free posterior border of the palate.
Tongue – It is made up of voluntary muscle and is attached to the hyoid bone at the base. Taste buds are present all over the tongue.
The blood supply – The tongue is supplied by – The lingual artery which is a branch of the external carotid artery. The lingual vein joins the internal jugular vein.
Nerve supply – The hypoglossal nerve (12th cranial nerve) is for voluntary movements. The mandibular nerve is responsible for general sensations such as pain, temperature, and touch. The fascial and glaso-pharyngeal nerves (cranial) are for special taste senses.
Functions – Mastication, Deglutition, Speech and Taste.
Teeth : Digestive System
The teeth are fixed (embedded) in the sockets (alveoli) of the maxilla and mandible. There are ten to 20 temporary teeth in each jaw. This tooth is completed in 24 months. The number of permanent teeth erupting at the age of six is 32 and it is Dentistry is completed by the 24th year.
There are four different types of teeth which have different functions like chopping, biting the pieces of food. are premolars and molars
Used for grinding and cleaning purpose.
Salivary Glands :
There are three pairs of salivary glands namely parotid, sub mandible and sub-lingual glands. These glands put their secretion into the oral cavity.
The parotid glands are located just below the external auditory canal on each side. The duct carrying saliva from these glands opens into the mouth cavity at the level of the upper second molar teeth.
The sub mandibular glands are located one on each side below the angle of the jaw. The duct coming out of these glands opens at the floor of the mouth.
The sublingual glands are located in front of the sublingual glands under the mucous membrane of the floor of the mouth. From these glands are many small ducts that open into the floor of the mouth.
Nerve Supply – parasympathetic stimulation increases the secretion of the gland. That sympathetic stimulation reduces the secretion of saliva.
Blood Supply – Arterial blood supply comes from branches of the external carotid artery and venous drainage into the external jugular veins.
Composition of saliva – Saliva is made of water. Mucus, enzymes, mineral salts, lysozymes, blood-clotting factors and immune-globulins.
Functions of Saliva : Digestive System Function
- Digestion of carbohydrates.
- Salivary amylase will break down complex polysaccharidesinto maltose.
- Lubrication of food.
- Cleansing and lubricating.
- Non specific defence by lysozyme, immune-globulins.
- Taste – When the dry foods get mixed with saliva then only there will be a sense of taste.
Pharynx (Throat) – It is divided into three parts nasopharynx, oropharynx and larynx. Important in naso-pharyngeal respiration. The oropharynx and larynx are common for respiration and digestion.
The mucosa is composed of stratified squamous epithelium, with fibrous connectives in the middle layer Tissue and blood vessels in it are lymphatic vessels and nerves. The outer layer contains involuntary muscles that help with swallowing. Nerve supply comes from the vagus nerve and the glossopharyngeal nerve (parasympathetic) and from the cervical ganglia (sympathetic).
Esophagus (Food Pipe) :
Esophagus (Food Pipe) – This tubular organ is 25 cm long and 2 cm in diameter. In the thorax it is located in the midline in front of the vertebral column and behind the trachea and heart. It passes through the diaphragm at the level of the tenth thoracic vertebra. It ends in the stomach at the heart orifice of the stomach. The esophagus has the same four layers that are seen elsewhere in the alimentary canal. layers on the outside……..
- Fibrous outer layer composed of fibrous connective tissue.
- Muscular layer is made up of outer longitudinal and inner circular.
- Sub-mucosa areolar tissue with blood vessels, lymphatic vessels and nerves.
- Mucosa – The mucous membrane secretes mucus.
The upper two-thirds of the esophagus is made up of striated voluntary muscles and the lower one-third by involuntary smooth muscles. The vagus nerve supplies nerve fibers to the esophagus. The dilation is followed by contraction in peristalsis (muscle movement) that takes 9 seconds to pass the bolus of food from the pharynx to the stomach.
Functions of esophagus, pharynx and mouth :
- Bolus formation.
- Devolution (swallowing).
- Transport of food.
Digestive System of Human Stomach :
The stomach is a ‘J’ shaped organ located in the epigastric navel and hypochondriac region. There are two holes in the stomach, the proximal one is called the heart and the distal one is called the pyloric.
The ‘J’ shaped limb has two curvatures, less curvature on the right border and more curvature on the left. The stomach is divided into three parts, the upper part is called the fundus, the middle part is called the body and the lower part is called the pylorus. The stomach capacity in an adult is 1500ml. The important organs associated with stomach are..
- Anterior – Liver and abdominal wall.
- Posterior – Aorta, pancreas, left adrenal, Spleen, kidney (Lt).
- Superior – Diaphragm
- Inferior – Transverse colon and small intestine.
- To the left – Diaphragm and spleen.
- To the right – Liver and Duodenum.
Wall of the stomach – It is formed by four layers like other organs in alimentary canal.
Muscle Layer –
- Inner – Oblique.
- Middle – Circular.
- Outer – Longitudinal.
Mucosa – This layer contains two types of gastric glands. When the stomach is empty they secrete enzymes and hydrochloric acid; the mucous membranes are thrown into folds called rugae.
Sub-Mucosa – It is made up of loose connective tissues.
Peritoneum – The outermost layer is made up of loose fibrous connective tissues.
Blood supply to the abdomen – this is from the branches of the celiac artery and the veins flow into the portal veins.
Nerve supply – Both sympathetic nerves form the thoracic region which form the celiac plexus and parasympathetic nerves are supplied from the vagus. The stimulation results in changes in the secretion of gastric juices and muscle movements.
Small Intestine Digestive System :
The small intestine is continuous with the stomach at the pyloric sphincter and connects to the large intestine at the ileo-caecal junction. Its length is more than 5 meters. It is located in the abdominal cavity and is surrounded by the large intestine.
Chemical digestion of food and absorption of nutrients is completed in the small intestine. The small intestine is divided into three parts. It starts from the duodenum which is 25 cm long and forms a C shaped curved loop around the head of the pancreas.
Gallbladders are secretions from the pancreas is inserted into the duodenum through a common tube called the hepato-pancreatic ampulla. The central part of the small intestine is about 2 meters long. The last part is called the ilium and is about 3 meters long. It attaches to the cecum which is the initial part of the large intestine.
Structure of the Small Intestine :
The walls of the small intestine are made up of four layers that are similar to the other organs of the alimentary canal, except for some changes in the mucosa and peritoneum. The mesentery is a double layer of the peritoneum that connects the small intestine to the posterior abdominal wall. Blood vessels and nerves pass between the two layers of the mesentery.
Mucosa : Digestive System
The surface is greatly enhanced by circular folds of villi and microvilli which help in digestion and absorption of foods. Villi contain secretory cells, blood vessels, lymphatic vessels (lactiales), goblet cells, nerve fibers.
There are many lymph nodes in the mucosa at irregular intervals along the entire length of the small intestine.
Blood Supply : The blood supply of the entire small intestine is by the superior mesenteric artery and the veins drain into the superior mesenteric vein and others which join to form the portal vein. The nerve supply is by both the sympathetic (thoracic) parasympathetic nerves.
Large Intestine :
It is about 1.5 m long and is composed of four coats similar to those found elsewhere in the alimentary canal. It consists of several parts such as the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and the anal canal that ends in the anus.
The appendix is a fine tube about 13 cm long and is attached to the cecum. The lumen of the large intestine is larger than the lumen of the small intestine. The arch formed by the large intestine covers the coils of the small intestine.
The blood supply is by superior and inferior mesenteric artery, and branches from internal iliac artery. The venous drainage is mainly by the superior and inferior mesenteric vein and finally they join portal vein. The veins from rectum and anal canal join the internal iliac vein.
Nerve Supply – The colon and other parts are supplied by both sympathetic, parasympathetic (autonomous) and voluntary control on external anal opening (anus).
Pancreas Digestive System :
It is a light brown gland located in the epigastric and left hypochondriac region with a weight of about 60 grams. The gland is made up of three parts head, body and tail.
The head is located in the curve (C shape) of the duodenum. The body is behind the abdomen and the tail is close to the left kidney.
Exocrine Pancreas :
The secretory cells form alveoli. The alveoli form a large number of lobules. The pancreatic duct collects the juice from all the lobules.
The pancreatic duct joins the common bile duct to form a common tube which joins the duodenum (ampulla – first part of small intestine).
Endocrine Pancreas – It is formed by Islets of Langarhans and secretes different hormones like insulin and glucagon directly into blood stream.
Blood Supply – The splenic and mesentric artery supply the blood and veins join to form portal vein.
Nerve supply – As in alimentary canal parasympathetic stimulation increases the secretion of pancreatic juice and sympathetic stimulation reduces it.
Liver Digestive System :
Liver is the largest gland in our body. The average weight of an adult is about 1.5 kg. It is located in the upper right part of the abdomen. The front surface is smooth and curved. The back surface is irregular.
Liver is covered by capsule and peritoneum. It is divided into two lobes (right and left) on the posterior surface. The portal vein, hepatic artery and nerves enter the liver. The hepatic ducts carrying bile leave the liver. Lymphatic vessels leave the liver to join the abdominal lymph nodes.
Blood supply – The hepatic artery a branch of abdominal aorta and portal vein formed by different veins in abdomen (G. I. tract veins) enter the liver. The hepatic veins leave the liver to join inferior vena cava.
Structure of the liver – The lobes of the liver are made up of many smaller lobules. Lobules are composed of hepatocytes. The lobules are hexagonal in shape. Each lobule contains a sinusoid, a bile duct, a central vein, a branch of the portal vein, Kupffer cells, and a branch of the hepatic artery. Hepatocytes help in bile secretion and Kupffer cells destroy foreign particles. Hepatocytes are responsible for different types of food metabolism.
It is a pear shaped sac made up of body, neck, fundus and duct. The gall bladder receives bile from liver by hepatic duct and releases the bile into common bile duct which joins pancreatic and finally enter duodenum. The gall bladder has same layers elsewhere in alimentary canal. The layers are
- Mucous membrane
- Muscle layer
The blood supply is by cystic artery and vein. The nerve supply is both from sympathetic and parasympathetic nerve fibers.
Functions of Gall Bladder :
- Reservoir of bile.
- Concentration of bile by water absorption.
- Release of bile.
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