Digestive System PDF

Mouth cavity The mouth opens to the outside at the lips and empties into the throat at the rear; its boundaries are defined by the lips, cheeks, hard and soft palates, and glottis. It is divided into two sections: the vestibule, the area between the cheeks and the teeth, and the oral cavity prop...

Mouth cavity The mouth opens to the outside at the lips and empties into the throat at the rear; its boundaries are defined by the lips, cheeks, hard and soft palates, and glottis. It is divided into two sections: the vestibule, the area between the cheeks and the teeth, and the oral cavity proper. The latter section is mostly filled by the tongue Tongue : it is a large muscle firmly anchored to the floor of the mouth by the frenulum linguae. the tongue, which positions and mixes food and also carries sensory receptors for taste;, In addition to its primary role in the intake and initial digestion of food, the mouth and its structures are essential in humans to the formation of speech : Teeth The chief structures of the mouth are the teeth, which tear and grind ingested food into small pieces that are ;suitable for digestion types of teeth 2 A. milk teeth, 20 in number (2 incisors , 1 canine and 2 molars in each side of upper and lower jaws ) B. permanent teeth, 32 in number (2 incisors , 1 canine ,2 premolar and 3 molar in each side of upper and lower jaws) Palate : separates the mouth from the nasal cavity,.allowing separate passages for air and for food All these structures, along with the lips, are involved in the formation of speech sounds by modifying the.passage of air through the mouth , Salivary glands : 3 pairs of glands parotid gland , below ear its duct opens.1. in vestibule of mouth.sublingual gland.2 submandibular.3 : Pharynx It is a firomuscular tube starts at a base of skull and ends below level of C5 It lies behind nose and mouth : Parts nasopharynx , found between the base of the skull and the soft palate. It is continuous with the nasal cavity and performs a respiratory function by conditioning inspired air.and propagating it into the larynx Oropharynxthe , middle part of the pharynx, located between the soft palate and the superior border of the ,.epiglottis Laryngopharynx , The most distal part of the pharynx, it is located between the superior border of the epiglottis and inferior border of the cricoid cartilage (C6). It is continuous inferiorly with the oesophagus : Esophagus it is a fibromuscular tube, approximately 25cm in length, that transports food from the pharynx to the stomach , It originates at the inferior border of the cricoid cartilage (C6) and pierces the diaphragm at level of T10 ,then extends to the cardiac orifice of the stomach.(T11) , It has 3 constrictions at its junction with pharynx (upper.1 esophageal sphincter) where it is crossed by aortic arch and left.2. main bronchus at it pierces diaphragm (lower.3 esophageal sphincter) : Stomach It is the most distendable part of GIT The stomach, is an intraperitoneal digestive organ located between.the oesophagus and the duodenum It has a ‘J’ shape, and features a lesser and greater curvature. The anterior and posterior surfaces are smoothly rounded.with a peritoneal covering The stomach has four main anatomical divisions; the cardia, fundus, body and :pylorus Cardia – surrounds the superior opening of.the stomach at the T11 level Fundus – the rounded, often gas filled.portion superior to and left of the cardia Body – the large central portion inferior to.the fundus Pylorus – This area connects the stomach to.the duodenum : Relations Superior. Esophagus ,left dome of diaphragm Anterior. Liver , gall bladder ,anterior abdominal wall , diaphragm , greater omentum Posterior. left kidney , left suprarenal gland , spleen , splenic artery , pancreas : Small intestine It is approximately 6m in the average person and assists in the digestion and.absorption of ingested food It extends from the pylorus of the stomach to the ileocaecal junction, where it meets the large intestine at the ileocaecal valve. Anatomically, the small bowel can be divided into three parts: the duodenum,.jejunum, and ileum : Duodenum The most proximal portion of the small intestine is the duodenum. Its name is derived from the Latin ‘duodenum digitorum’, meaning twelve fingers length. It runs from the pylorus of the stomach to the.duodenojejunal junction The duodenum can be divided into four parts: superior, descending, inferior and ascending. Together these parts form a ‘C’ shape, that is around 25cm long, and which wraps around the head of the.pancreas In middle part it receives opening of common bile duct and pancreatic duct : Jejunum and ileum The jejunum and ileum are the distal two parts of the small intestine (jejunum 2/5 , ileum 3/5). In contrast to the.duodenum, they are intraperitoneal They are attached to the posterior abdominal wall.by mesentery (a double layer of peritoneum).The jejunum begins at the duodenojejunal flexure.The ileum ends at the ileocaecal junction. At this junction, the ileum invaginates into the cecum to form the ileocecal valve. Although it is not developed enough to control movement of material from the ileum to the cecum, it can prevent reflux of material back into the ileum : Large intestine Parts. Cecum , vermiform appendix , ascending colon , transverse colon , descending colon , sigmoid colon , rectum ,.anal canal Function. Absorption of water and electrolytes storage of undigested materials until it can be expelled as feces It is about 150cm length : Liver The liver is the second largest (after the skin) organ in the human body and the largest gland (weighing an average of 1500 g). It lies under the diaphragm in the right upper abdomen and midabdomen and extends to the left upper abdomen(right hypochondriac & epigastric regions). The liver has the general shape of a wedge, with its base to the right and its apex to the left. It is pinkish brown in color, with a soft consistency, and is highly vascular and easily.friable : Liver has 4 lobes Right lobe Left lobe Caudate lobe Quadrate lobe Separating the caudate and quadrate lobes is a deep, transverse fissure – known as the porta hepatis. It transmits all the vessels, nerves and ducts entering or leaving the liver with the exception of the hepatic.veins : Liver surfaces The external surfaces of the liver are described by their location and adjacent structures. There are two liver surfaces – the diaphragmatic and :visceral Diaphragmatic surface – the anterosuperior.surface of the liver It is smooth and convex, fitting snugly beneath –.the curvature of the diaphragm. Visceral surface – the posteroinferior.surface of the liver It is moulded by the shape of the – surrounding organs, making it.irregular and flat It lies in contact with the – right kidney, right adrenal gland, right colic flexure, transverse colon, first part of the duodenum, gallbladder, oesophagus and the stomach : Ligaments of liver There are a number of ligaments that attach the liver to the surrounding structures. These are formed by a double ,layer of peritoneum. They include falciform ligament.1 coronary ligament.2 triangular ligament.3 lesser omentum.4 :Blood supply :The liver has a unique dual blood supply Hepatic artery proper (25%) – supplies the non- parenchymal structures of the liver with arterial blood. It is.derived from the coeliac trunk Hepatic portal vein (75%) – supplies the liver with partially deoxygenated blood, carrying nutrients absorbed from the small intestine. This is the dominant blood supply to the liver parenchyma, and allows the liver to perform its gut-.related functions, such as detoxification Venous drainage of the liver is achieved through hepatic veins. The central veins of the hepatic lobule form collecting veins which then combine to form hepatic veins. These hepatic veins then open into the inferior vena cava :Biliary system (gall bladder & ducts) : Gall bladder it is a gastrointestinal organ located within the right hypochondrial region of the abdomen. This intraperitoneal, pear-shaped sac lies within a fossa formed between the inferior aspects of the right and.quadrate lobes of the liver The primary function of the gallbladder is to concentrate and store bile which is produced by the liver. the stored bile is then released from the gallbladder in response to.cholecystokinin Parts.fundus ,body , neck : Biliary tree biliary tree is a series of gastrointestinal ducts allowing newly synthesised bile from the liver to be concentrated and stored in.the gallbladder (prior to release into the duodenum) Bile is initially secreted from hepatocytes and drains from both lobes of the liver via cTheanaliculi, intralobular ducts and collecting ducts into the left and right hepatic ducts. These ducts amalgamate to form the common hepatic duct, which.runs alongside the hepatic vein As the common hepatic duct descends, it is joined by the cystic duct – which allows bile to flow in and out of the gallbladder for storage and release. At this point, the common hepatic duct and cystic duct combine to form the common bile.duct The common bile duct descends and passes to the first part of the duodenum and head of the pancreas. Here, it is joined by the main pancreatic duct, forming the hepatopancreatic ampulla (commonly known as the ampulla of Vater) – which then empties into the duodenum via the major duodenal papilla. This papilla is regulated by a muscular valve, the sphincter of Oddi : Pancreas The pancreas is an abdominal glandular organ with both digestive (exocrine) and hormonal (endocrine) functions located deep within the upper abdomen in the epigastrium and left hypochondrium regions in concavity of duodenum and.posterior to stomach.Parts. Head , neck , body and tail : Spleen The spleen is a large lymphoid organ located in the upper left abdomen (left hypchondrium), and is roughly the size of a clenched fist. In the adult, the spleen functions mainly as a blood filter, removing old red blood cells. It also plays a role in both cell-mediated and humoral immune.responses by production of lymphocytes It is located in the upper left quadrant of the abdomen, under cover of the diaphragm and the ribcage (left 9 , 10 ,11 ribs)– and therefore cannot normally be palpated on clinical.examination (except when enlarged) The outer surface of the spleen can be :anatomically divided into two Diaphragmatic surface – in contact with.diaphragm and ribcage Visceral surface – in contact with the.other abdominal viscera