Large Intestine Structure and Function Flashcards
how long is the colon?
1.5-1.8m
what are the four parts of large colon?
ascending, transverse, descending, sigmoid
what is involved in the large intestine?
Ileum ileocaecal valve caecum (blind sac) vermiform (worm-like) appendix – lymph nodes
which layers or the large intestine are complete and incomplete?
circular muscle is complete
longitudinal muscle is incomplete
what type of epithelium is the mucosa of large intestine
simple columnar
what function does goblet cells have that are attached to crypts
lubrication of faeces
what type of tube is the rectum?
straight, muscular
between sigmoid colon and anal canal
what type of epithelium is mucosa of the rectum?
simple columnar
where is the anal canal?
2-3 cm between distal rectum and anus
what type of muscle is the external anal sphincter?
skeletal muscle
what type of epithelium is the anal canal?
simple columnar to stratified squamous
what is the tenia coli?
The taeniae coli (also teniae coli or tenia coli) are three separate longitudinal ribbons (taeniae meaning ribbon in latin) of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons
what is the function of the colon?
Actively transports sodium from lumen into blood -> osmotic absorption of water -> dehydration of chyme -> solid faecal pellets
what is the colonic microflora?
10^14 bacteria
what is a result of long residence time in the colon?
bacterial colonisation
what nervous system control defaecation reflex?
parasympathetic via splanchnic nerves
what happens in the defaecation reflex
Contraction of rectum
Relaxation of internal and contraction of external anal sphincters
Increased peristaltic activity in colon
Pressure on external anal sphincter - relaxes under voluntary control expulsion of faeces
Voluntary delay of defaecation - descending pathways
what is constipation?
No absorption of toxins from faecal material following long periods of retention
what are symptoms associated with constipation?
Headaches
Nausea
Loss of appetite
Abdominal distension
due to distension of rectm
what is diarrhoea?
Too frequent passage of faeces which are too liquid
what are causes of diarrhoea?
pathogenic bacteria protozoans viruses toxins food first year medical exams…
what are examples of enterotoxigenic bacteria?
Vibrio cholerae, Escherichia coli
what is the result if enteroxoigenic bacteria?
Produce protein enterotoxins which maximally turn on intestinal chloride secretion from crypt cells
H2O secretion
Act by elevating intracellular second messengers:
cAMP
cGMP
calcium
H2O secretion swamps absorptive capacity of villus cells profuse watery diarrhoea (25 litres per day for cholera)
what is the treatment of secretory diarrhoea?
Enterotoxins don’t damage villus cells
Give sodium/glucose solution
Drive H2O absorption rehydration
Secretion still going wash away infection
Oral rehydration therapy
