L4 lower GI Flashcards
what is the function of the small intestine
complete digestion of food (with assistance of the liver and pancreatic secretion) and to absorb of nutrients and minerals into the body
what is the overall length of the SI
6-7m, but contracts to 2-4m
what is the length of each part of the SI
duodenum = 0.25m
jejunum = 2.5m
ileum = 3.6m
what is the two types of motility of the SI
segmentation and peristalsis
what is segmentation
segmentation of the chyme helps to mix the chyme, initiated by the pacemaker cells. this is done by alternating rings of contraction and relaxation, moving food forwards and backwards (bi-directional)
what is peristalsis
contraction of circular and longitudinal smooth muscles in coordination to move food along
what does the duodenum release that causes gastric emptying
motilin
what is MMC
migrating motor complex, tummy rumble.
where does MMC originate
the stomach and duodenum
what does MMC do
it helps to move indigestibles
how does the ileocaecal valve open (valve between SI and LI
gastroileal reflex and the gastrin (released by parietal cells in the stomach)
sympathetic innervation of the SI
from thoracic splanchnic nerves
parasympathetic innervation of SI
from vagus nerve
where is the blood supply of the SI from
superior mesenteric artery
where does the blood from the SI drain to
superior mesenteric vein then through hepatic portal vein
when does blood flow in SI increase
during parasympathetic excitation (after feeding)
when does blood flow decrease in SI
during sympathetic excitation
what is intestinal blood flow controlled by
local hormones, glucose, and fatty acids
what is the duodenum
the shortest and straightest section of the small intestine. it begins from pyloric sphincter to duodenal-jejunal junction. it is retroperitoneal and relatively static
what is the duodenum connected to
hepatopancreatic ampulla (bile duct and pancreatic duct)
how does the duodenum connect to the liver
via the lesser omentum
what is an autoimmune disease related to the duodenum
coeliac disease
what causes coeliac disease
a reaction to gliadin (gluten protein)
what are symptoms of coeliac disease
grey, loose, greasy, large stools., fatigue, anaemia, failure to thrive, diarrhea/ constipation, lactose intolerance development
what is the difference between wheat allergy and coeliac disease
coeliac is autoimmune whilst wheat allergy is an immune response
what are the functions of jejunum and ileum
specialised for absorption
what are the jejunum and ileum
SI segment that is suspended in loops from the posterior abdominal wall. they are intraperitoneal
how is the SA of the SI increased
circular folds, villi, microvilli
what is the lacteal
lymphatic vessel in the villi
what is the goblet cell
cells that produce mucus on the villi
what is an enterocyte
absorptive cells on the villi, possesses microvilli
what is the intestinal crypt
tubular glands on the villi
what is the function of a tubular crypt
secretes intestinal juice of pH 7.4-7.8
what is carried in the intestinal juice that the intestinal crypt secretes
molecular digestive products for absorption
what stimulates the release of intestinal juice
acidic/ hypertonic chyme
what is secreted by the enteroendocrine cell
enterogastrone hormones and T cells
what is the function of the paneth cells
secretes antimicrobial peptides and protein (lysozymes and defensins), allowing some bacterias to die, and some to colonise
how does the small intestine renew?
stem cells
what do the stem cells differentiate to
goblet cells, absorptive cells, enteroendocrine cells, paneth cells.
how do old cells get removed
apoptosis
what is peyer’s patches
aggregated lymphoid nodules that keep the intestinal flora at appropriate levels and the pathogens at bay, thus preventing a large number of infections.
where are peyer’s patches located
more numerous in distal SI.
what is duodenal glands (brunner’s glands)
produces alkaline mucus (containing bicarbonate) to neutralize stomach acid
where is the duodenal/ brunner’s glands located
submucosa of duodenum
what is the function of the large intestine (3)
- reabsorb water from indigestible food
- absorb metabolites produced by bacteria
- eliminate feces from body
what is the length and width of the large intestine
1.5m and 7cm
what are the blood supply of the large intestine
superior mesenteric artery and inferior mesenteric artery
where does the large intestine blood drain to
inferior mesenteric vein, then to splenic vein. superior mesenteric vein and then to hepatic portal vein
how long is the rectum
12cm
what is the function of the function of the rectum
temporary storage of feces
what happens when no defecation occurs
feces returned to colon and more water reabsorbed, leading to constipation
what is the apparent function of the vermiform appendix
contains lymphoid tissue that may contain a reservoir for healthy gut bacteria to allow the body to replenish after an infection or illness.
what is appendicitis
acute inflammation of the appendix, caused by infectious bacteria trapped within
symptoms of appendicitis
abdominal pain, nausea, vomiting, appetite loss
what happens when appendix ruptures
peritonitis
treatment of appendicitis
immediate appendectomy
what is the mucosa of the LI
simple columnar epithelium in colon and rectum. no circular fold, villi, or enzymatic secretory cell. thick mucosa, deep crypts, and many goblet cells
three types of epithelium in the anal canal
simple columnar, stratified squamous, stratified keratinized.
what is the flora of the LI and their functions
10 million types of bacteria are present in the LI
their functions include synthesizing vitamin B and K, metabolizing secreted compounds eg mucin, heparin, hyaluronic acid., and fermenting carbohydrates.
how are feces formed
food residue present in the large intestine for 12-24 hours and enters the ileocaecal valve, becoming feces.
what is contained in feces
undigestibles (fibre)
bacteria
waste from erythrocyte breakdown
mucus
epithelial cells
water
why are feces brown
stercobilin (bile pigment), end product of breakdown of hemoglobin
motility of LI
mass movement: is long, slow, and powerful, peristalsis, dietary fibre aids motility
what is haustral contractions
occurs when distention occurs, is slow and short. segmentation (mixing) aids water reabsorption, occurs in ascending and transverse colon
what is the defecation reflex
parasympathetic and mediated by spinal cord.
has voluntary and involuntary aspects
aided by voluntarily increasing into-abdominal pressure and contracting levitator ani muscle
diarrhea causes
- cholera – increase in active secretion (secretory diarrhea)
- coeliac, excess fructose/ sorbital – osmotic diarrhea
- crohn’s, e coli – exudative diarrhea
- ibs, bacterial infection – inflammatory
