Ch 12 Digestive System

Small intestine

-Longest part of the alimentary canal

-Primary digestive organ in the body

-Coiled tube divided into: duodenum, jejunum and ileum

Chemical digestion

-Starting in the mouth, digestive secretions break down food into their chemical building blocks

-Process is completed in the small intestine

Propulsion

-Swallowing (oropharynx)

-Peristalsis (esophagus, stomach, small and large intestine)

Where does the majority of digestion and absorption occur?

Small intestine

Hard palate

-Created by maxillary and palatine bones of the skull

-Rigid shelf against which the tongue can push food

-Ends in the posterior oral cavity

Soft palate

• Made of skeletal muscle

• Can be manipulated subconsciously to yawn, swallow or sing

Uvula

-Drops down from the posterior edge of the soft palate

-Along with the soft palate, moves upward during swallowing to keep food/drinks from entering the nasal cavity 

Palatine tonsils

Clusters of lymphoid tissue protecting the pharynx

Lingual tonsils

Located at the base of the tongue

Papillae

Found on the top and sides of the tongue

Salivary glands

Exocrine glands found within the mucous membranes of the mouth and tongue

Subdivisions of the pharynx

-Nasopharynx: involved in breathing and speech

-Oropharynx: involved in breathing and digestion

-Larynxgopharynx: involved in breathing and digestion

Esophagus

-Located posterior to the trachea

-Connects the pharynx to stomach

-Penetrates the diaphragm through an opening called the esophageal hiatus to enter the abdomen

Upper esophageal sphincter

Controls movement of food from pharynx to the esophagus

Lower esophageal sphincter (LES)

Controls movement of food from esophagus to the stomach

Large intestine

• Terminal part of the alimentary canal

• Runs from the appendix to the anus

• functions include:

  • Finishes absorption of nutrients

  • Synthesizes vitamins

  • Forms and eliminates feces

• 4 main regions include: cecum, colon, rectum and anus

Ileocecal valve

Controls flow of chyme from small intestine to large intestine

Cecum

-First part of the large intestine

-Receives the contents of the ileum

Appendix / Vermiform appendix

-Winding tube that contains lymphoid tissue

-Attached to the cecum

Colon

-Blends seamlessly with the cecum

-Food first travels up the ascending colon, then the transverse colon, descending colon and finally the sigmoid colon

Liver

• Lies inferior to the diaphragm in the right upper quadrant of abdominal cavity

• Has a large right lobe and a small left lobe

Bile

A mixture secreted by the liver for emulsification (breakdown) of lipids in the small intestine

Bile pigments

Bilirubin, proteins and iron

Bilirubin

• Main bile pigment

• Waste product produced when the spleen removed old/damaged red blood cells

• Excreted in the bile, accounting for the green color

• Transformed into a brown pigment called stercobilin, giving stool its color 

Pancreas

-Lies transversely in the retroperitoneum behind the stomach

-Exocrine cells secrete pancreatic juice to the duodenum through the pancreatic duct

-Pancreatic islet cells secrete hormones into the blood

-The head of the pancreas is nestled into the “c-shaped” curvature of the duodenum

Gallbladder

• Muscular sac

• Located behind the right lobe of the liver

• Stores, concentrates and, when stimulated, propels bile into the duodenum via the common bile duct

Ingestion

Entry of food through the mouth

Mechanical digestion

• Tongue breaks food down and mix it with saliva

• Churning of food in the stomach further breaks it apart and allows for the creation of chyme

Mastication

chewing

Cholecyst

gallbladder

Gastroesophageal reflux disease

Gastric acid flows up from the stomach into the esophagus

Cholecystitis

• Inflammation of the gallbladder

• Caused by gall stone development that blocks the release of bile

Cirrhosis

-Scarring of the liver

-Life threatening condition

Ascites

Buildup of fluid in abdominal cavity

Celiac Sprue (Celiac Disease)

Immune sensitivity reaction in the small intestine when consuming gluten

Crohn’s disease

-Chronic inflammatory bowel diseases (IBD)

-Malabsorption of nutrients (most common in small intestines)

Ulcerative colitis

• Chronic inflammatory bowel diseases (IBD)

• Localized inflammation and ulcers in the colon

Hernia

Organ or fatty tissue squeezes through a weak spot in a muscle or connective tissue

Hiatal hernia

Found in the upper stomach region

Irritable bowel syndrome (IBS)

-Disorder of the large intestines

-Abdominal pain within the colon as food moves through the digestive tract

Polyps

• Found in people over age 50

• Start as a small collection of cells in the colon

• Small growth of tissue protruding out from the intestinal wall

• Harmless but may turn into a cancerous growth overtime

Omentum

• Fatty tissue that stretches over abdomen

• Plays a role in immune response and in the growth of certain cancers

Palpate

Physical examination technique

Hemorrhoids

Distended/swollen veins in the rectum and anus

Emulsification

• Breaking down fat into smaller blood cells

• Makes it easy for enzymes to function/digest food

Dysentery

Inflammation of the intestine

Adhesion

Band of scar tissue that binds anatomic surfaces to each other