Digestive system Flashcards
What are the parts of digestive system?
- mouth (oral cavity)
- tongue
- Salivary glands (parotid, sublingual, submandibular)
- Pharynx
- Esophagus
- Stomach
- Pancreas
- Liver
- Gallbladder
- Small intestine (duodenum, jejunum, ileum)
- Large intestine (Transverse colon, Descending colon, ascending colon, cecum, sigmoid colon, rectum, appendix, anal canal, anus)
What are the accessory organs to the GI tract?
- Salivary glands
- Liver
- Pancreas
- gallbladder
What is the function of the GI tract?
To move electrolytes water and nutrients from digestive tract to blood, and eventually to cells.
What are the major functions of the mouth and its associated accessory organs?
- Ingestion: food voluntarily placed into oral cavity
- Propultion: voluntary (buccal) phase of deglutition initiated by the tongue; propels food into pharynx
- Mechanical breakdown: mastication by teeth and mixing movements of the tongue
- Digestion: Salivary amylase in saliva, produced by salivary glands begins the chemical breakdown of starch.
* The mouth serves as a receptacle; most functions preformed by acessory glands. mucus in saliva helps to dissolve foods so they can be tasted and moistens food so that the tongue can impact it into a bolus that can be swallowed. Saliva clenses and lubricates the oral cavity anf teeth.
What are the major functions of the pharynx and esophagus?
- Propulsion: perstaltic waves move food bolus to stomach, thusaccomplishing involuntary (pharyngeal-esophageal) phase of degultition
* Primarily food chutes; mucus produced helps to lubricate food passage ways.
What are the major functions of the stomach?
- Mechanical breakdown and propulsion: peristaltic waves mix food with gastric juice and propel it into the duodenum.
- Digestion: pepsin begins the digestion of proteins.
- Absorption: Absorbes a few fat soluble substances (asprin, alcohol and some drugs)
*Also stores food until it can be moved into the duodenum.Hydrochloric acid produced is a bacteriostatic agent and activates protein digesting enzymes. Mucus produced helps lubricate and protect the stomach from self digestion. Intrinsic factor produced is required intestinal absorption of vitamin
B12
What is the function of the small intestine and its acessory organs ( liver, galbladder and pancreas)?
- Mechanical breakdown and propulsion: segmentation by smooth muscle of the small intestine continually mixes contents with digestive juices and, along with short-distance peristaltic waves, moves food along the tract, allowing suffecint time for digestion and absorption.
- Digestion: Digesive enzymes delivered from pancreas and brush boarder enzymes atached to microvilli membranes complete digestion of all classes of food.
- Absorption: Breakdown products of carbohydrate proteins, fat and nucleic acid digestion. Plus vitamins, electrolytes and water are absorbed by passive and active mechanisms.
* The small intestine is highly modified for digestion and absorption. Alkaline mucus produced by intestinal glands and bicarbonate rich juice ducted in from the pancreas helps to neutralized acidic chyme and provide the proper enviorment for enzymatic activity. Bile produced by the liver emulsifies fats and inhances fat digestion and fatty acid absorption (monoglycerides, cholesterol, phospholipids and fat soluable vitamins. The gallbladder stores and concentrates bile, releasing it into the small intestine in response to hormonal signals.
What is the function of the large intestine?
- Digestion: some remaining food residues are digested by enteric bacteria (which also produce vitamin K and some B vitamins)
- Absorption: absorbs most remaining water, electrolytes (largely NaCl) and vitamins produced by the bacteria.
- Propulsion: Propels feces toward rectum by haustral churning and mass movements.
- Defecation: reflex triggered by rectal distention; eliminates feces from the body.
*Temporarily stores and concentrates residues until defecation can occur. copious mucus produced by goblets cells helps to ease the passage of feces through the colon.
Where does ingestion occur?
at the mouth/oral cavity
Where in the GI tract does propultion occur?
Through out the GI tract
Where does mechanical breakdown occur in the digestive tract?
- Mouth; chewing
- Stomach; churning
- Small intestine; segmentation
Where does digestion take place in the GI tract?
- Mouth; salivary amylase
- Stomach; pepsin
- Small intestine; enzymes finally digest all classes of food.
- Large intestine: bacteria digest remaining food residues, and make vitamin K and B
Where does absorption take place in the digestive tract? where do the nutrients go?
- Stomach; absorbs a few fat soluablr substances (asprin, alcohol and some drugs)
- Small intestine; breakdown products of carb, protein, fat nucleic acid digestion. Water vitamins and elecrolytes are absorbed by passive or active mechanisms.
- Large intestine; absorbs most of the remaining water, electrolytes mostly NaCl, and vitamins produced by the bacteria.
- Everything gets absorbed intoo the lymph and blood vessels.
Where does defecation occur?
- In the large intestine; reflex triggered by rectal distention, eliminates feces from the body.
Mucous neck cells
scattered in the neck and more basal regionsof the glands, they produce a thin, soluble mucus , different than the mucus secreted by the mucous cells of the surface epithelium. Their function is still not understood.
