Digestive Tract The alimentary Canal

1. Alimentary Canal – The path food takes through the body 1. Alimentary Canal – The path food takes through the body. *humans – roughly 30 feet *Covered in epithelium tissue 2. Mouth a. Teeth – mechanically break down food b. Tongue – Strong skeletal muscle for moving food, tasting food c. Salivary glands – Produce saliva to moisten food and amylase enzyme to digest carbohydrates. d. Food moves into the Pharynx to be swallowed. Epithelium tissue – Membrane layer of cells in organs that protects, secretes chemicals, acts in absorption and sensing.

3. Esophagus – Leads from the mouth to the stomach a 3. Esophagus – Leads from the mouth to the stomach a. The epiglottis keeps food from entering the trachea b. Peristalsis moves food to the stomach

4. Stomach – Muscular flexible bag with digestive juices produced in the lining to primarily break down protein. a. Cardiac sphincter – a circular muscle that keeps food in the stomach from re-entering the esophagus. (heart burn/acid reflux) b. Pyloric sphincter – a circular muscle that keeps food in the stomach until it is ready to be released into the small intestine.

4. Stomach tissue a. Serosa – “Outer layer” made up of connective tissue and epithelium. b. Smooth Muscle – “Second layer in” Smooth muscle oriented in 3 different directions to properly mix food. c. Submucosa – “Third layer in” Made of dense connective tissue that holds the mucosa layer to the smooth muscle. d. Mucosa – Inner most layer that secretes gastric juices that include mucus, hydrochloric acid and pepsin enzymes. The pH of the stomach is about 2. When food enters endocrine cells release a hormone “gastrin” into the blood which triggers the production of gastric juices!

Special assisting organs 5. Small Intestine – “Chyme” enters the sm. Intestine from the stomach at the duodenum. Special assisting organs *Liver – Makes bile, which is stored in the gall bladder. Bile emulsifies fats from the chyme…..physically separating fat into tiny fat droplets. *Pancreas – Makes many enzymes that ultimately help to break down carbohydrates, fats and protein. *Liver and pancreas release their enzymes into the duodenum. Chyme – The mixture of gastric juices and food produced by the stomach.

Small Intestine continued b Small Intestine continued b. Villi – fingerlike projections designed to increase the surface area for nutrient absorption. c. Microvilli – The villi have villi to REALLY increase food absorption. d. Brush border cells – cells that make up the microvilli, they secrete mucus, enzymes (primarily for carbs and protein) as well as hormones and lysozyme. e. Absorption – Water, salts, simple sugars, amino acids move into the blood at the brush border cells of the villi. *Fat has to go through a bit more as it becomes a triglyceride and joins with protein to become a “lipoprotein” which through lymph fluid will eventually enter the blood.

6. Cecum – A cuplike pouch where the small intestine meets the large intestine. *Absorbs water and salts as well as lubricates the chyme with a mucus. *The appendix hangs off the cecum and has no varrified function. Some scientist believe the appendix is a store house for good bacteria to help replenish the system after illness

7. Large Intestine – Waste “indigestable material, dead bacteria, mucosal cells, inorganic substances and water” all enter from the small intestine. a. Sodium is actively pumped through the lining wall into the blood, water follows. b. Feces is solidified into a compacted waste c. Over 4000 species of bacteria live here which make many vitamins that are absorbed through the lining wall.

8. Rectum – The last 10-15 cm’s of the large intestine 8. Rectum – The last 10-15 cm’s of the large intestine. Stores and compacts feces. a. When the rectum expands it triggers smooth muscle contractions that force the feces out of the body through the anus. b. This contraction can be overridden by the contraction of the anal sphincter to keep feces in.