THE ESOPHAGUS AND STOMACH

FUNCTION OF ESOPHAGUS

• To carry food, liquid, and saliva from the mouth to the stomach
• 8 inches long and is lined by mist pink tissue called mucosa

PERISTALTIC MOVEMENT

• The contraction and relaxation of the muscles of the digestive tract to move food through the digestive system
• The function in the esophagus is to push food down into the stomach and stop it from coming back up

The esophagus is made of 3 sections:
1. The upper 1/3 or proximal esophagus- striated, skeletal muscle
2. Middle esophagus- mixed skeletal and smooth muscle
3. Distal esophagus- smooth muscle

OVERVIEW OF STOMACH

• Muscular sac between esophagus and small intestine
• J-Shaped and can expand to temporarily store food

FUNCTION

• Digestion of food
• Secretion of gastric juices as well as mucus which helps coat it's lining
• Secretion of gastric hormones
• Regulation of the rate at which partially digested food is delivered to small intestine
• Absorption of small quantities of water and dissolved substances

3 STAGES OF DIGESTION

• Cephalic phase prepares the stomach for incoming food and lasts very briefly.
• Gastric phase begins with the arrival of food, causing the secretion of the hormone gastrin, which is released along with many acids and enzymes. This phase may last for several hours.
• Intestinal phase begins with the entrance of chyme into the small intestine, causing the secretion of many hormones including secretin, CCK (cholecystokinin), and GIP (gastric inhibitory peptide).

STRUCTURES

• Pyloric Sphincter-helps regulate the rate at which gastric contents are delivered to the small intestine.
• Rugae-thick accordion-like folds within the stomach that allow it to expand during a large meal
• Vagus nerve-of the PNS (parasympathetic nervous system) innervates stomach action

GASTRIC GLANDS

• Mucus Cells- mucus cells secrete mucus to protect the lining from the potential destructiveness of the acidic gastric juices
• Chief cell-secrete digestive enzymes, mainly pepsinogen
• Parietal cells- secrete hydrochloric acid (HCl) and intrinsic factor. HCl lowers the pH of the gastric juice, kills microorganisms, breaks down the cell walls and connective tissues in food, and activates the exzymatic secretions of the chief cells.

ENZYME ACTION

• Protein breaks down into peptides when the stomach lining excretes the enzyme, pepsin
• Fat digestion continues with the help of some gastric lipase
• Food that is partially digested by chewing and the action of enzymes in the mouth and stomach is called chyme
• Food that is partially digested by chewing and the action of enzymes in the mouth and stomach is called chyme

HOW YOUR STOMACH WORKS

• http://youtu.be/KAfnIPYN0X0

Once in the stomach, metabolism of protein begins. The main stomach enzyme is pepsinogen, which is quickly converted into pepsin by the acidic stomach juices. Pepsin starts to reduce the protein in steak into smaller building blocks called amino acids and peptide fragments. However, if your stomach isn't acidic enough, less pepsin is converted and protein digestion is significantly reduced. Your stomach juices also contain some gastric lipase, which continues to metabolize the saturated fat in the steak. Steak spends much more time in the stomach, a total of about four hours, compared to grains, fruit or vegetables, which usually spend less than an hour or so.

CITATIONS

• "SEER Training Modules." SEER Training:Stomach. Web. 12 May 2015.
• "Stomach - Innvista." Innvista. Web. 12 May 2015.
• "The Stomach (Human Anatomy): Picture, Function, Definition, Conditions, and More." WebMD. WebMD. Web. 12 May 2015. .