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- Gastrointestinal Tract or GI Tract
- 6-9 meters long tube where food processing takes place to bring nutrients into the body. Transported through the lumen of the tube from the mouth to the anus
Four Layers to the Digestive System
- Mucosa: the epithelial lining that faces the lumen of the gut
- Submucosa: layer of connective tissue containing blood and lymph vessels plus nerve networks
- Smooth muscle layer: (longitudinal and circuclar muscle layers) lies outside the submucosa
- Sphincters: circular arrays of smooth muscle, close off a passageway to control forward movement of the tract's contents
Describe the parts of the digestive system. What occurs in each part?
- The Mouth (oral cavity): Start of digestive system. food is chewed mositened, polysaccharide digestion begins. Teeth (32 in adults , 20 in children) chewing and swallowing is the beginning
- Salivary Glands: Secrete a fluid called saliva into the mouth. Paratoid glands just in front of the ear; submandibular glands in lower jaw; sublinguals under the tounge.
- Pharynx: Enterence to tublar parts of digestive and respiratory systems. The throat. The tongue and the palate of the roof of the mouth are use to aid in"mixing" of the food then the muscle contractons force the bolus into the pharynx. Swallowing is vountary and involuntary.
- Esophagus: Mucscular tube, moistened by saliva, that moves food from pharynx to stomach
- Stomach: Food storage, digestion and more. Muscular sac that stores and mixes food, secretes substances to dissolve and degrade food, and controls the rate at which food enters the small intestine. gastric fluids destroys many microbes. stretches.
- Small Intestine: The first part receives secretions from the liver, gallbladder and pancreas. The second part is where vast majority of the nutrients are absorbed here. The last part delivers unabsorbed material to colon. the key to the ability to absorb is in the structure of the wall. Mucosa has extensive circular folds, Villi, Microvilli
- Large Intestine: begins as a blind, cupshaped pouch (cecum) where it joins the small intestine. contains the colon. ends in the sigmoid colon which connects with the rectum.
- -Colon (asending, transverse, and descending) - stores feces
- Liver: One of the largest organsin the body. Processes mutrient0daledn blood from the small intestine; blood enters the liver via the heptatic pertal vein. Functions of the liver include
- - converst glucose to glycogen, a storage form
- - produces plasma proteins
- - forms urea
- - makes bile, which is useful in fat emulsification
- - detoxifies harmful substances
- - aids in the immune respone by removing foreign particles
- - absorbs and stores factors needed for red blood cell production
- Gallbladder: small sac that stores bile produced by the liver. bile is emptied into the small intestine when food is present to aid in the digestion and absorption of fats
- Pancreas: produces a variety of digestive enzymes (carbohydrates, proteins, lipids, and nucleic acids). lies near the stomach, contains exocrine and endocrine glands. Produces the hormones that regulate blood sugar and bicarbonate to neutralize the pH of chyme
- Rectum: Distension triggers expulsion of feces
Describe the enzymes involved in digestion of the biomolecules and what their substrate is (what they break down)
- Salivary Amylase: is in saliva to begin carbonhydrate digestion, bicarbonate to neutralize acids, and mucins to help form the food into bolus
- Pepsin: (active) begins the digestion of proteins
What is peristalisis?
Peristalis is when the muscles contract along the esphogus squeezing the bolus to move food along the tract to the stomach.
What is a peptic ulcer?
A peptic ulcer is when a bacteruim (Helicobacter pyclori) can interfere with mucus production and the stomach lining is no longer protected by mucus and bicarbonate ions.
What is the function of villi and microvilli?
- Villi: absorbtion surface of the small instestine is increased by these finglike projections of the lining.
- Microvilli: inside the villi, even smaller, giving each cell a "brush border"
What is the function of bicarbonate in the digestive system?
What is appendicitis?
Appendicitis is when feces becomes trapped in the appendix causing inflammation.
Discuss the hormones that regulate digestion
- Gastrin: source is the stomach. the effect on the digestive system is the increase of acid secretion by the stomach
- Secretin: source is the small intestine. the effect is the increase of bicarbonate secretion by pacreas and slows contractions in the small intestine.
What causes diverticulitis and diverticulosis?
What is an essential amino acid?