Digestive System - Alimentary Tract 1 Flashcards
Describe the structure and function of the oral cavity.
Formed;
Superiorly by the hard and soft palate
Inferiorly by the tongue - skeletal muscle running in 3 directions
Laterally by the cheeks
Begins process of mechanical and chemical digestion - salivary glands
Important for defence against infection - tonsils
Describe the structure and function of the pharynx.
Consist of 3 parts - nasopharynx, oropharynx and laryngopharynx
Sits behind oral and nasal cavities
Continuous with respiratory system at larynx
Continuous with digestive system at oesophagus
Only oropharynx and laryngopharynx transmit food
Describe the structure and function of the oesophagus.
Structure;
Mucosa - innermost layer,
Submucosa - glands secreting mucous
Muscularis mucosa - inner circular layer and outer longtitudinal layer
Adventitia - CT
Functions;
Peristalsis - rhythmic contraction and relaxation of the esophageal muscles that propels the food bolus toward the stomach
Protection - mucous lining of the esophagus provides protection against the abrasive action of swallowed food and liquids and the corrosive effects of gastric acid reflux from the stomach
Describe the structure and function of the small intestine.
Made of 3 portions - duodenum, jejunum and ileum
Extends from pyloric sphincter to ileocecal junction
Completes digestion and absorbs nutrients
Digestive activity and absorption diminishes from the proximal to distal end of the small intestine
Duodenum;
C-shaped and encloses the pancreas
Receives bile from the gall bladder via bile duct and digestive enzymes from pancreas via pancreatic duct
Ileocecal valve;
Sphincter muscle valve that separates the small and large intestine
Function is to limit the reflux of colonic contents into the ileum
Jejenum - characterized by a rich blood supply and prominent circular folds (plicae circulares) in its mucosal lining, which increase the surface area for nutrient absorption
Ileum - contains specialized lymphoid tissue called Peyer’s patches, which play a role in immune defense
What is the appendix?
Appendix is a narrow, blind-ended tube attached to the posteromedial end of the cecum
Position of the appendix is highly variable.
Describe the structure and function of the liver.
Divided into 4 lobes, largest internal organ
Functions
Nutrients absorbed in the digestive tract are transported via hepatic portal vein, then processed and stored in the liver
Liver produces bile which has an exocrine function important for digestion
Metabolises toxic substances
Modifies the actions of hormones released by other organs - endocrine like function.
Describe the structure and function of the gall bladder.
Pear-shaped sac located on posterior surface of liver
Mucosa - innermost layer, lined with epithelial cells
Muscularis mucosa - smooth muscle that contracts to expel bile from the gallbladder
Serosa - outermost layer, CT
Functions;
Bile storage
Bile release - cholecystokinin (CCK), causes the release of stored bile into the small intestine through the common bile duct
Digestion - bile emulsifies large fat globules into smaller droplets
Describe the structure and function of the pancreas.
Structure:
Head, body and tail
Pancreatic ducts
Islets of Langerhans
Lies posterior to the stomach
Endocrine function - regulation of blood glucose levels through the secretion of hormones such as insulin and glucagon
Exocrine function - production and secretion of digestive enzymes and bicarbonate ions into the duodenum to aid in the digestion of carbohydrates, proteins, and fats in the small intestine
What is the peritoneum?
Membrane lining surface of body wall and internal organs
Visceral peritoneum - lines organs
Parietal peritoneum - lines abdominal wall
Between these 2 layers is peritoneal cavity - contains serous fluid aiding movement of abdominal organs
Mesentery - double layered fold of visceral peritoneum
Retroperitoneal - posterior abdominal wall .
Describe the greater omentum.
4 layered parietal fold
Forms large sheet that lies over and protects intestines
Can wrap around organs to localise inflammation and prevent peritoneal adhesions
Describe the lesser omentum.
Double layered peritoneal fold
Contains the hepatic artery, portal vein and common bile duct.
Describe briefly the stomach
J-shaped organ that hangs inferior to diaphragm
Storage tank where food is mechanically broken down into chyme by acid and enzymes
Thick folds (rugae) disappear when stomach distended
What are the different regions of the stomach?
Cardia - shallow pits, long coiled glands, mostly mucous cells, some parietal cells
Fundus and body - branched tubular straight glands, chief cells
Pylorus - long deep pits, short coiled glands, mucous and enteroendocrine cells
