bio large intestine一問

For MAMMALS, there are a few plant eaters who need to digest cellulose. It is done in the CAECUM[or cecum], not the colon, although they are connected to each other.

圖片參考：http://upload.wikimedia.org/wikipedia/commons/thumb/8/82/Stomach_colon_rectum_diagram.svg/250px-Stomach_colon_rectum_diagram.svg.png


Most herbivores have a relatively large cecum, hosting a large number of bacteria, which aid in the enzymatic breakdown of plant materials such as cellulose.
So it DOES NOT STORE dietary fibres, only micro-organisms.
The appendix have no use at all, and some people are born without appendix, and are completely healthy otherwise. Thus it is said to be vestigial [退化的, 無用的].
OK, back to your answers:
The function of the large intestine is for keeping the micro-organisms in and letting them digest cellulose in HERBIVORES ONLY. It doesn't happen to carnivores like tigers nor omnivores like dogs, or us.
But for ALL MAMMALS, the large intestine is a place for water absorption, alongside with mineral and vitamin absorption.

哎也~wrong左la
大腸最主要ge功能係absorb water,因為digest food同absorb digested food已經俾大腸之前ge alimantary cannal做晒
雖然stomach都係用黎absorb water,but stomach吸收ge水係來自食物/飲料中ge水
而大腸吸收ge水主要係來自alimantary cannal分泌出ge液體(eg.digestive juice)

cellulose係唔能夠俾吸收ga,所以就算真係有micro-organism digest the cellulose,e個都唔係一個功能,反而將cellulose break down into simpler molecules可能係個壞處,因為cellulose在消化作用ge功用就係將d digested food整成一團野,如果cellulose變左simpler molecules,d digested food就只可以一"pac"野