2015年12月13日 星期日

F4 Biology teaching notes Ch 6: NE 25

D  Digestion in the stomach (Book 1A, p. 6-13)


Ø   Functions of stomach:
n   To store food temporarily
n   To carry out partial digestion of food (proteins)

Ø   Structure of stomach:      
n   a sac-like organ formed by muscles
n   The entrance and the exit is guarded by sphincter muscles (括約肌)

(35)    Cardiac sphincter
(賁門括約肌)
(36)   Pyloric sphincter
(幽門括約肌)
l   Guard the entrance
l   Prevent the backflow of food to
(37) oesophagus
l   Guard the exit to
l   Open periodically (週期性打開) to release
digested food to (38) duodenum


n   Gastric glands (胃腺) on the stomach wall produce (39) gastric juice (胃液), which contains:
Component
Function
(40)            
Pepsin
(胃蛋白酶)
l  Catalyses the breakdown of proteins into (41) peptides
l  Works best in an (42) acidic / alkaline medium
(43)
Hydrochloric acid

(HCl, 氫氯酸)
l  Provides an (44) acdic medium for:
²  the action of pepsin
²  stopping the action of salivary amylase
l  Kills most (45) bacteria in food
(46)
Mucus

(黏液)
l  Protects the stomach wall from being:
²  digested by the (47) enzymes / pepsin
²  damaged by the (48) hydrochloric acid

Ø   Digestion of stomach:
Mechanical Digestion
Chemical Digestion
n  Peristaltic movement of muscles:
l To chun (攪動) the food into small pieces
l To mix the food with (49) gastric juice
n  Enzymes catalyse the protein digestion
Food is digested into (50) chyme (食糜) which is released into the duodenum (十二指腸)
https://www.youtube.com/watch?v=LjRK8i-KCiU (胃酸倒流 咳唔停口)
https://www.youtube.com/watch?v=vAPtndafv10 (喇舌恐傳播幽門桿菌)

https://www.youtube.com/watch?v=Wo8y3u6gZ9k (上班族辛酸事:幽門螺旋菌篇)

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