Digestive System

AKA G-I Tract Alimentary Canal

Overview Consists of Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus About 30’ in length Accessory Organs Teeth, tongue, gall bladder, salivary glands, liver and pancreas Glands secrete saliva, bile and enzymes

GI System

Process Includes Ingestion Mechanical – chewing, churning Propulsion – swallowing and peristalsis Chemical – breakdown via enzymes Absorption – transport of end products into blood Defecation – elimination as feces

GI Process

Peritoneum and cavity Parietal peritoneum surrounds cavity, lines body wall Visceral surrounds organ Serous membrane allows organs to glide/expand Retroperitoneal refers to organs in the dorsal region Peritonitis = inflammation of peritoneum Perforation = infection

Peritoneum

Quadrants

Regions

Regions

Mesentery Double layer of peritoneum, holds organs in place Omentums - protection Lesser = fatty skin, superficial near the stomach Greater = deeper, made of connective tissue, significant fat Three layers of fascia – Skin, Fascia, mesentary

Messentery

Messentary

Omentum

Greater Omentum

Histology Smooth muscle - peristalsis Glands with ducts Nerves, arteries and veins

Histology

Mouth Point of Origin Oral cavity Tongue Soft and hard palate Uvula Oropharynx Epiglottis Larynx/pharynx Esophagus

Mouth Anatomy

Mouth Anatomy

Salivary glands Produce saliva, a mixture of water, ions, mucous, and enzymes Dissolve food Wets food to help bind it to become a bolus Neutralizes acids, helps growth of beneficial bacteria Intrinsic –in tongue, palate, lips and cheeks Extrinsic = outside mouth Parotids Submandibular Sublingual

Salivary Glands

Pharynx Oso Laryngopharynx Lined with epithelial cells for protection

Pharynx

Esophagus Muscular tube Propels swallowed food to stomach Passes through diaphragm (esophageal hiatus) into abdomen Join the stomach at cardiac orifice Cardiac sphincter prevents reflux or regurgitation of acid

Esophagus

Esophagus

Esophagus

Stomach Food churned into chyme; a paste Secretes pepsin – a protein digesting enzyme and HCl Waters, electrolytes, some drugs absorbed through stomach Anatomy Cardiac orifice, fundus, lesser and greater curvature, pylorus Rugae = numerous longitudinal folds of mucosa which flatten as stomach fills, allows expand

Stomach

Stomach

Stomach

Junction

Stomach

Small Intestine Longest part of alimentary canal Most enzymes involved in small intestine come from pancreas Three divisions – each approximately Duodenum – 5% Jejunum – 40% Ileum – almost 50%

Duodenum Receives digestive enzymes from pancreas Bile from gall bladder and liver Almost all nutrients are absorbed in small intestine Large surface area, great length

Small Intestine

Small Intestine

Duodenum

Gall Bladder Cystic duct Bile duct – empties into small cystic duct Secrete bile for duodenum digestion Bile – Right and Left hepatic ducts to common cystic duct to Gall bladder for storage From GB to bile duct to duodenum

Gall Bladder

Pancreas Exocrine gland – produces most enzymes for digestion in small intestine Endocrine function = produce hormones that regulate levels of sugar in the blood Main pancreatic duct

Gall Bladder and Pancreas

Pancreas

Large Intestine Most material has been digested by the time it reaches LI 12-24 hours in large bowel Little breakdown Performs some absorption, especially water Components Ascending colon Transverse colon Descending colon Sigmoid to rectum and anus

Large Intestine

Large Intestine

Cecum and appendix Cecum is a small sac (blind pouch) Valve prevents a back up of fecal matter to ileum Appendix Lymph tissue neutralizes bacteria Diverticulosus – a small outward herniation of colon, especially sigmoid Diverticulitis – infection with leaks into peritoneal cavity may lead to peritonitis

Anal Canal ANS balance between defecation or not PNS = increase movement SNS = decrease Voluntary control via external sphincter muscles

Anal Canal

Defecation

Liver Largest gland in the body (1.4 kg – 3 lbs.) Produces bile Stored in GB Emulsifies fats Involved in metabolism Diaphramatic and visceral surface Right and left lobes Porta hepatis = major vessels and nerves Right and left hepatic ducts, common bile, common

Liver

Liver

Liver

Liver