Large
Intestine
Jejunum terminates at caecum. Caecum is small saclike evagination, important
in some animals as a repository for bacteria/other organisms able to digest
cellulose. A blind ending appendix may give trouble (appendicitis) if
infected. The large intestine has three longitudinal muscle bands (taenia
coli) with bulges in the wall (haustra) between them. These may evaginate
in the elderly to become diverticuli and infected in diverticulitis.
The large intestine resorbs water then eliminates drier residues as faeces.
Regions recognised are the ascending colon, from appendix in right groin
up to a flexure at the liver, transverse colon, liver to spleen, descending
colon, spleen to left groin, then sigmoid (S-shaped) colon back to midline
and anus. Anus has voluntary and involuntary sphincter and ability to
distinguish whether contents are gas or solid. No villi in large intestine,
but many goblet cells secreting lubricative mucus.