- More complex animals have complete digestive tracts (alimentary canals), which are one way digestive tubes that begin with the mouth at one end of the terminate in the anus at the other.
- Complete vs. gastrovascular -complete has an advantage of having specialized regions.
- 4 Types of Organs: Mouth, esophagus, stomach, small intestine
Step By Step of the Human Digestive System
- When food is in the mouth, or oral cavity, a nervous reflexoccurs which causes saliva to be secreted into the mouth. Saliva lubricates the food and contains the enzyeme Salivary Amylase, which hydrolyzes starch and glycogen (polysaccrides-complex carbohydrates) into smaller polysaccridesand the disaccharide maltose. This is typically the 1st type of macromolecule to be enzematically attacked.
- During chewing, food is shaped into a ball called a bolus. After being swallowed, the bolus enters the pharynx - a junction thta opens to the esophagus and the trachea. During swallowing, the epiglottis (a flap made of cartiledge) moves to cover the trachea. This will divert the foodto go down the esophagus.
- The esophagus moves food from the pharynx down to the stomach though peristalsis-rhymic waves if contraction by smooth muscle in the walls of the esophagus. (also occurs in the alimentary canal)
- The stomach is in the upper abdominal cavity, and it's functions include storing food and secreting gastric juice.
- Gastric Juice contains hydrocholic acid, which is very acidic (pH of about 2). Gastric juice breaks down the extracellular matrix of meat and plant materials, and it also kills most of the bacteria ingested with the food.
- Gastrin is a hormone produced by the epitheial lining of the stomach.
- Chyme is a soupy mixture of acids and food particles in your stomach.
- Pepsin is an enzyme in gastic juice that begins to hydrolyze proteins into smaller polypeptides. Pepsin secreted in an inactive form called pepsinogen, which is activated by the hydroclhloric acid in the stomach.
- The result of digestion in the stomach is a substance called acid chyme. The acid chyme is shunted from the end of the stomach into the beginning of the small intestine via the pyloric sphincler.
- Rugae is the inner linings of the stomach ---> more surface area
- The small intestine (final breakdown) is the longest, 6m, section of the alimentary canal. The beginning of the small intestine is the site of most of the hydrolosis of macromolecules, and the rest of the small intestine is responsible for the absorbtion of nutrients into the blood.
- The 1st section of the small intestine is known as the duodenum. In the duodenum, the acid chyme mixes with sections from the pancreas (bicarbonate, which acts as a buffer against acid chyme), the liver (bile, which contains bile salts-detergents that aid in digestions and help stabilize fat emulsions), the gall bladder, and the intestinal itself.
- REMEMBER: Bile is produced in the liver and stored in the gall bladder. (That is why the gall bladder is green)
- The gal bladder has no digestive secretions.
QUESTIONS:
1. Which of the answers is not considered one of the main organs?
A. Pepsin
B. Mouth
C. Esophagus
D. Small Intestine
2. Where is bile produced?
A. Gallbladder
B. Liver
C. Stomach
D. Pharynx
3.What is an example of a complex carbohydrate?
A. Gastric juice
B. Polypeptides
C. Salivary Amylase
D. Glycogen
ANSWERS: 1. A, 2. B, 3. D
Pictures:
http://www.gallstoneinformation.com/wp-content/uploads/2009/03/ency4beta_getimageaspx.jpg
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