Week 2: Digestion and Absorption Flashcards
(26 cards)
What is gastrointestinal tract? GI tract
flexible muscular tract that extends from the mouth, through the oesophagus, stomach, large intestine, and rectum to anus.
What is digestion?
- process by which food is broken down into absorbable units
Describe the strucutre and function of the mouth
- teeth crush food, mix with fluids+saliva to ease wallowing = mastication
- the tongue facilltiates chewing+swallowing
- food passes thru pharynx
- the epiglottis classes of air passages so no choking
- after swallowing food=bolus
Describe the strucutre and function of the oesophagus
- swallowing open upper oesophageal sphincter
- lower oesophageal sphincter at entrance closes behind the bolus so that it doesn’t go back into oesophagus, prevents reflux
Describe the strucutre and function of the stomach
- circular, longnitudinal, diagonal muscles work to force chyme down
addes and grinds to a semiliquid mass=chyme - pyloric sphincter remains closed preventing from passing to duodenum
- stomach wall releases gastric juices = chyme liquified
- release chyme thru pyloric sphincter, which opens into small intestine and closes behind chym
Describe the strucutre and function of the small intestine
chyme passes down the small intestine thru the duodenum, jejunum and ileum
- digested and abrobed macronutreitns
Describe the structure and function of the large intestine(colon)
- the chyme passes thru ileocaecal valve(begining of large intestine)
- absorbs water, vitamins and absorbable nutrients from content
- collects waste material for storage in rectum forming stool
- bacteria in colon ferment any remaining materials, prod beneficial metabolites can be reabsorbed
- the muscles of the anus and rectum hold back waste until to defecate
- the rectal muscles relax, 2 sphincters of the anus open to allows passage of water
What nutrients do not need digesting?
- minerals, vtiamins, water
- small enough to be absorbed so do not need to be broken down=digested
- fibre not broken down by human digestive enzymes
- fermented in colon by gut bacteria to help keep healthy gut
What is segmentation
- inner circular muscles in the gi tract contract and relaxwhich churns the chyme
- occurs in small and large intestine
What is peristalsis
- outer longnitudinal muscles in gi tract contract rhythmically moving chyme forward
- occurs in oesophagus
What is the salivary glands, target organ, secretion and major action?
- Mouth
- Saliva
- eases swallowing, salivary enzyme breaks down some carbs
- also protects teeth, and linings of mouth, oesophagus and stomach from subtacnes that might harm them
What is the gastric gland, target organ, secretion and major action?
- stomach
- gastric juice(h20, enzymes, HCL)
- fluid mix with bolus
- hydrochloric acid uncoils proteins
- enzyme break down protein
- mucus protects stomach cells from bacteria+acid
Function of hydrochloric acid
- prevents bacterial growth and kills msot bacteria that enters the body
What is the pancreas, target organ, secretion and major action?
- small intestine
- pancreatic juice
- bicarbnate neutralises acidic gastric juices, pancreatic enzymes break down macronutrients
What is the liver, target organ, secretion and major action?
- Gall bladder
- bile
- stored in gall bladderuntil needed
What is the gall bladder, target organ, secretion and major action?
- duodenum of smal intestine
-bile - emulsifies fat so that enzymes can have access to break it down
What is the intestinal glands, target organ, secretion and major action?
- small intestine
- intestnial juice
- break down macronutrients fragemtns,
- mucus protects intestine wall
Describe the strucutre and function of lining of small intestine
- lined with small projections called VILLI
- single villus composed of hundreds of cells , each covered w hairs called microvilli
- CRYPTS lie between villi - tubular gladns secreting intestinal juices into small intestine
-each villus is lined w thin sheet of muscle so it can move. - nutrient molecules trapped by microvilli -> drawn into cells or digested further by enzymes
- water soluble nutrients/small fat products released into bloodstream-> liver
- insoluble fats/vitamins are clustered together by intestinal cells =chylomicrons
- released into lymphatic system ->move thru lymph->enter blooddstream
What are the 2 circulatory systems that deliver nutrients where needed
vascular and lymphatic
What is absorption
- uptake of nutrients by the cells of the small intestine for transport into either the blood or lymph
Describe how nutrients are delivered thru the vascular system
- blood leaving digestive system goes thru hepatic portal vein (to liver)
-liver prepares absorbed nutrients for use by body - blood leaving liver returns to heart
Describe how nutrients are delivered thru the lymphatic system
no pump;lymph circulates between cells and collects into tiny vessils
- lymph collects in thoracic duct behind heart - lymph enter bloodstream here
What does the hormon gastrin respond to, secreted from, stimulate, its response
- food in stomach
-stomach wall
-stomach glands - hydrochloric acid secreted into the stomach to maintain an acidic pH
What does the hormon secretin respond to, secreted from, stimulate, its response
- acidic chyme in small intestine
- duodenal wall
- pancreas
- bicarbonate rich juices secreted to maintain slightly alkaline pH
