DIGESTIVE SYSTEM

FUNCTIONS 1. Ingestion. 2. Digestion. 3. Absorption. 4. Defecation.

COMPONENTS (1) Alimentary (Gastrointestinal) tract which performs the whole digestive functions. (2) Accessory organs: assist the process of digestive break down.

ALIMENTARY CANAL (GIT) Muscular tube. Length: In the cadaver 9 m. In the living person , is shorter because of the muscle tone. Continuous, Coiled & Hollow. Winds around the ventral body cavity. Opens at both ends.

COMPONENTS OF GIT Mouth. Pharynx. Esophagus. Stomach. Small intestine. Large intestine.

ACESSORY DIGESTIVE ORGANS Salivary glands. Teeth. Liver & Gall bladder. Pancreas.

MOUTH (oral cavity) A mucous membrane lined cavity. It is the site of food entry. Boundaries : Anterior : lips (labia). Lateral : cheeks. Roof : hard and soft palates. Floor : tongue.

ORAL CAVITY Divided into : Vestibule : A space between the lips and cheeks externally and the teeth and gums internally. Oral cavity proper: : The area contained by the teeth. It contains Lymphoid tissue : Palatine tonsil and lingual tonsil.

PHARYNX Oropharynx and Laryngopharynx are parts of the alimentary tract. Food is propelled through the pharynx into the esophagus by peristalsis.

ESOPHAGUS A muscular tube 25 cm (10) inches long. Begins as a continuation of the pharynx. Terminates in the stomach. It conducts food to the stomach.

STOMACH Position : On the left side of the abdominal cavity under the liver and diaphragm. Shape : C – shaped. Length : 25 cm

PARTS 1. Cardiac region : near the heart. 2. Fundus : the expanded part lateral to the cardiac region. 3. Body : mid portion. 4. Pylorus: the terminal part of the stomach. divided into : Antrum. Pyloric canal : cavity of pylorus.

CURVATURES Greater : convex lateral surface of the stomach. Lesser : concave medial surface.

SPHINCTERS Physiological: Cardioesophageal: Where the esophagus opens into the stomach. Anatomical: Pyloric : where the stomach is continuous with the small intestine.

PERITONEUM Lesser omentum : It extends between the liver and the lesser curvature. Greater omentum : It extends between the greater curvature and the transverse colon .

SMALL INTESTINE It is the major digestive organ (2.5 -7) m in the living person. Extends: from the Pyloric sphincter to the Ileocecal valve. Divided into: Duodenum, Jujenum & Ileum.

DUODENUM The shortest part of the small intestine (nearly 5%). C-shaped. Receives the openings of the pancreatic and bile ducts.

JUJENUM & ILEUM 2. JUJENUM : Contributes nearly 40% of the small intestine. 3. ILEUM : Contributes nearly 60% of the small intestine. It joins the large intestine at the ileocecal valve.

LARGE INTESTINE Larger in diameter and Shorter in length (1.5) m than the small intestine. It frames the small intestine on three sides. It extends from the Ileocecal valve to the Anus. It dries the indigestible food residue and eliminates it out as feces.

CRITERIA (1) Teniae Coli : three bands of muscle that can be seen externally. It is formed from the longitudinal muscle layer. (2) Haustra : small pocket like sacs in the wall due to the muscle tone. (3) Appendices epiploicae: peritoneal folds full of with fat.

PARTS (a) Cecum : first part of the large intestine. (b) Appendix : A wormlike, It hangs from the cecum. It is an ideal site for bacteria to multiply and accumulate .

COLON 1. Ascending: It travels up the right side of the abdominal cavity. It makes a turn, the right colic (hepatic) flexure. 2.Transverse It travels across the abdominal cavity. It makes the left colic (splenic ) flexure.

COLON Rectum. Anal Canal and Anus. Descending It travels down the left side of the abdominal cavity and enters the pelvis. Sigmoid (pelvic) It is S- shaped and lies in the pelvis. Rectum. Anal Canal and Anus.

ANAL SPHINCTERS The anal canal has two sphincters : 1. External (voluntary) formed of skeletal muscle. 2. Internal (involuntary) formed of smooth muscle.

TEETH Deciduous (milk) teeth : They begin to appear about (6) months. The first teeth to erupt are the lower central incisors. At the age of two years they are (20) in number. The milky teeth fall out between ages (6-12) years. Permanent teeth : Fully erupted at the end of adolescence. They are 32 in number. Third molars (wisdom) Erupt later at ages (17 –25) years.

SALIVARY GLANDS Three pairs of salivary glands (1) Parotid glands They are the largest. They lie anterior to the ear. They empty their secretion into the vestibule. (2) Submandibular glands. (3) Sublingual glands. They empty their secretions into the floor of the mouth cavity proper.

LIVER The largest gland in the body (exocrine & endocrine). It lies in the right side of the body under cover of the diaphragm. It is formed of (4) lobes.

LIVER It is suspended to the diaphragm and anterior abdominal wall by the peritoneal fold (Falciform Ligament).

FUNCTIONS Exocrine gland: It produces bile. Bile leaves the liver through the common hepatic duct. Enters the duodenum through the bile duct. Bile salts are important for the metabolism of fat. Endocrine gland: Produces vitamin A, stores glycogen.

GALL BLADDER A small thin walled green sac. Lies on the inferior surface of the liver. Stores and concentrates bile. Bile enters and leave the gall bladder through the cystic duct.

PANCREAS It is a soft pink triangular gland. It is retroperitoneal. It extends from the spleen to the duodenum across the posterior abdominal wall. Functions : 1. Endocrine : production of insulin and glucagon hormones. 2. Exocrine : It produces enzymes that enter the duodenum through the pancreatic ducts.

PANCREATIC DUCTS Main pancreatic duct: Joins the bile duct to form the Hepato pancreatic ampulla. Both ducts open together through the duodenal papilla in the duodenum. Accessory pancreatic duct: Opens separately.