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

MouthPoint 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