Digestive system

Composition

• Alimentary tract (passage through which food travels)

• Accessory organs (organs that help prepare food for absorption and use by the tissues of the body)

• Main functions of the digestive system are to ingest and carry food so tha absorption can occur and waste can be eliminated

Stomach

• large, hollow organ

• Main organ of digestive system

• While digestion begins in the mouth, where saliva begins to break down foods, most digestion takes place in the stomach, which secretes gastric juices that begin converting ingested foods to a form that can be absorbed and used by the body

Pancreas

• Flat, solid organ that lies inferior and posterior to stomach

• Secretes pancreatic fluids that aid in the digestion of fats, starches, and proteins

• The islets of Langerhans, located in the pancreas, produce the insulin that regulates the amount of sugar in the bloodstream

Liver

• Largest solid organ in the abdomen, lies immediately beneath diaphragm in the right upper quadrant of the abdominal cavity

• Produces bile, which aids in the digestion of fat

• Stores sugars till they are needed by body

• Produces components necessary for immune function

• Toxic substances produced by digestion → harmless

Spleen

• Solid organ located in the upper left quadrant of abdominal cavity

• It helps in the filtration of blood and, because it contains a dense network of blood vessels, serves as a reservoir of blood the body can use in an emergency such as hemorrhage.

Gallbladder

• Hollow pouch

• Part of bile dict; acts as reservoir for bile

• When food enters the small intestine, contractions are stimulated that empty the gallbladder into the small intestine, where the bile aids in the digestion of fats

The small intestine

• Made up of duedenum, jejunum, and ileum

• Received food from the stomach and secretions from the pancreas and liver

• Digestion of food continues in the small intestine, where food is completely broken down into a form that can be used by the body. Nutrients are absorbed through the walls of the small intestine and circulated through the bloodstream to all parts of the body.

Large intestine/colon

• Hollow

• The parts of food that cannot be absorbed by the body are passed as waste products from the small intestine to the large intestine.

• As these waste products move through the large intestine, their water is absorbed.

• What remains is the stool that is then passed through the rectum and the anus.

Digestive Process

• Digestion has 2 processes: mechanical and chemical.

• Mechanical digestion includes:

  • Chewing

  • Swallowing

  • Peristalsis = rhythmic movement of food through the digestive tract

  • Defecation = elimination of digestive waste

• Chemical digestion uses enzymes/digestive juices to break food into forms the body can absorb and use.

• Carbohydrates → glucose

• Fats → fatty acids

• Proteins → amino acids

Urinary or Renal System

• Urinary/renal system filters and removes waste from the blood.

• Main parts:

  • 2 kidneys → filter blood and help control fluid balance

  • 2 ureters → carry urine from kidneys to bladder

  • Bladder → stores urine

  • Urethra → carries urine out of the body

• Kidneys also help regulate:

  • Blood pressure

  • Red blood cell production

  • Water and chemical balance

  • Acid-base balance

• During urine formation:

  • Waste products are removed from the blood

  • Useful substances are returned to the blood

• Urine flow: Kidneys → ureters → bladder → urethra