Physiology of Large Intestine Flashcards
Longitudinal muscle in caecum and colon divided into 3 strands called
taeniae coli
Longitudinal muscle encircles what
anus and rectum
Where does smooth muscle become thickened
internal anal sphincter
skeletal muscle encircles what
external anal sphincter
Taeniae coli and circular muscle create
Haustra
What comes from taeniae coli
Appendices
What does the caecum receive
1-2l of undigested material, unabsorbed fluid, unabsorbed biliary contents from the terminal ileum via ileocaecal valve
What stimulates the opening of the ileoecaecal valve
CCK and gastrin
The gastroileal reflex is influenced by
distention of the stomach –> open
distention of the ascending colon –> close
hormones, parasympathetic, sympathetic, enteric neurones
What is the appendix
Blind ended tube with extensive lymphoid tissue
How does the appendix attach to the caecum
via appendicael orofice
What may cause the appendix to become obstructed leading to appendicitis
faecalith
Primary functions of colon
Absorption of sodium, calcium, water = condenses ileoceacal material into solid/semi-solid stool
Fermentes undigested carbohydrates into short chain fatty acids by colonic material
Secretions K, HCO3 and mucus
Reservoir - storage
Periodic elimination of faeces
Fluid reabsorption and bacterial elimination occurs till
Distal end of transverse colon
Final drying and storage
Descending colon and rectum
Periodic elimination of faeces is voluntary or involuntarty
Usually voluntary after early childhood
WHat is faeces made up of
100g/100ml = H20 50g = bilirubin, little salt, bacteria, cellulose
mucosa of the large intestine lacks what
villi
Mucosa of the small intestine possesses
circular folds, crypts and microvilli which increase SA
Surface epithelial colonocytes
mediate electrolyte absorption
osmosis driven by H2O absorption
Crypts
ion secretion
Goblet cells
Mucus
Protein defense
Na/K absorption increased by
aldosterone
significant loss of what in faeces in secretory diarrhoea
Potassium
Haustration
non propulsive movement alternating contraction to circular muscle
When do haustra appear and disappear
Appear after mass movement
How often does haustration occur
very slowly between 16 and 48 hours to allow for absorption
A mass movement involves
large secretions of circular and transverse colon powerfully drives faeces into distal region
A mass movement occurs
1-3 times per day
What is a mass movement normally stimulated by
Gastroileal response after a meal
Mass movement in distal region propels faces into what
Rectum
In a mass movement the rectum fills with faeces. What does this activate
Faecal stretch receptors
Contraction of the smooth muscle of sigmoid colon and rectum (internal anal sphincter) can cause
Relaxation of skeletal muscle of external anal sphincter = ASSITS DEFECATION
Contraction of skeletal muscle of external anal sphincter = DELAYED DEFECATION
The colon contains about 500-1000 bacteria the most are beneficial to the gut what are their main functions
Increase intestinal immunity
Promote motility
Synthesise vit K2 and free fatty acids
activate some IBD treatment
As well as faeces what else does the anus permit expulsion of
Intestinal gas - flatus
Flatus is a result of
swallowed air
some carbohydrates require certain bacteria to be absorbed
internal and external anal sphincters contract and leave. a narrow exit which doesn’t permit solid matter to pass through
How does Irritable Bowel Syndrome Present
bouts of diarrhoea, constipation and abdo pain
What is the treatment of Irritable Bowel Syndrome
modification of diet
anti-diarrhoeals
anti-spasmodics
laxatives
Explain the use of linaclotide
Peptide drug used for the treatment of moderate to severe IBS with constipation in adults
How does linaclotide work
Increases secretion of Chloride and bicarbonate
Increases intestinal transmit
What is the benefit of linaclotide
Improves bowel movement and alleviates discomfort
What are the side effects of linaclotide
diarrhoea
Unlicensed low doses of amitriptyline are used for
Abdo pain
Inflammatory Bowel Disease is an overarching term for
Crohn’s - Entire gut
UC - Colon
Acute IBD treatment
Glucocorticoids e.g. prednisolone
Prolonged use –> adrenal suppression
Aminosalicylcates include
Sulfasalazine
Aminosalicylates are used to
Decrease inflammation in maintenance and mild UC
