The Digestive System (Unit Test)

The Digestive Tract

• In humans, the digestive tract includes:

  • Mouth

  • Esophagus

  • Stomach

  • Small and large intestine

  • Anus

• Accessory organs include (not part of but support digestive tract):

  • Liver

  • Gallbladder

  • Pancreas

• The digestive tract is lined with epithelial tissue (goblet cells) that secrete mucus

• Mucus serves two purposes:

  • It protects the digestive tube from digestive enzymes

  • Allow food to pass through smoothly

• Your digestive tube also contains layers of muscle tissues and nerves.

  • If you eat spoiled food, your body recognizes the toxins and the digestive tract will get rid of it by vomiting or diarrhea

1. The Mouth

   1. Starts the breakdown of food:

      • Physically → teeth and tongue

      • Chemically → enzymes break down food

   2. The mouth adds saliva (a mixture of water and enzymes) to the food

   3. Once the food is broken up and softened by saliva, it is swallowed and passed into the esophagus

   4. This process is called Machanical Digestion

      • Digestion begins in the mouth where food is broken down by the teeth.

      • Small parts of food are mixed with saliva and swallowed

   5. Salivary Glands

      1. Why Is Mucus Important?

         • The epithelial cells that line the digestive tract secrete mucus

         • Mucus is important because it protects the digestive tract from being damaged by digestive enzymes

         • Mucus also helps food pass easily through the tract

   6. The Breakdown of Carbohydrates

      1. The foods you eat made up of 3 major groups of nutrients:

         • Proteins

         • Carbohydrates

         • Fats

      2. The chemical breakdown of carbohydrates begins when saliva mixes with the food as you chew.

      3. The starchy taste soon becomes sweet!

2. The Esophagus

   • A muscular tube that connects the mouth to the stomach

   • It is made up of smooth muscle tissue that can contract and expand

   • This movement is controlled by nerve tissue and slowly pushes food along the digestive tract (peristalsis)

3. The Stomach

   • Main function is to hold food and churn it → continues the digestive process

   • The stomach lining is made up of cells that release digestive enzymes and acids

   • The smooth muscle cells contract to mix the contents

   • Contains nerve cells that send a signal to your brain when you have had enough to eat

4. The Large and Small Intestines

   • Between the stomach and the anus lies the small and large intestines.

   • Smooth muscle cells contract and relax, pushing food through the intestines.

   • Mucus is also produced by the cells lining the intestines (goblet cells)

   1. The Small Intestines

      • 6 m in length, relatively narrow and the area where most digestion occurs

      • Nutrients diffuse through the wall of the small intestine and into the bloodstream

   2. The Large Intestines

      • A.k.a. The Colon

      • 1.5 m long but larger in diameter than the small intestine

      • Water absorption occurs in the large intestine

      • The remaining waste (feces) is excreted via the anus

   • From the stomach, food enters the small intestine where digestion is completed and the small digested food molecules are absorbed into the bloodstream.

   1. Colitis

      • When the epithelial tissues lining the colon become inflamed and stop working properly

      • Causes include: viruses, bacteria, narrowed blood vessels, and failure of the body’s disease fighting mechanism

   2. Crohn

      • Crohn’s disease is a type of inflammatory bowel disease (IBD) that causes your digestive tract to become swollen and irritated. If you have Crohn’s, you might experience symptoms like abdominal pain, diarrhea, weight loss and rectal bleeding

Accessory Organs

• The liver, pancreas, and gall bladder all aid in digestion by supplying digestive enzymes

• The liver → produces bile which helps break down fats

• The pancreas → produces insulin which regulates the concentration of sugar in the blood

The Pancreas and Diabetes

• Diabetes is a disease in which the pancreas produces too much or too little insulin

• People with diabetes experience weakness and dizziness due to their inability to control their blood glucose levels

Peristalsis