Large Intestine Flashcards
what are the functions of the large intestine?
- to convert undigested material into feces by removing water and adding mucus
- store and transport feces
- largest microbial presence
- slower motility to allow for water and solute absorption
what is the widest part of the colon and most prone to perforation
cecum
what transitions to the transverse colon at the hepatic flexure
ascending colon
what marks the transition from transverse colon to descending colon
splenic flexure
what is the narrowest part of LI and most mobile
sigmoid colon
what runs anterior to rectum and separates it from prostate and seminal vesicles or vagina
Denonvilliers’ fascia/rectovaginal fascia
what supports the lower portion of the rectum and provide scaffold for blood vessels and nerves
lateral ligament
the rectum is innervated by ?
parasympathetic NS;pelvic splanchnic nerves
the anal canal connects ? to ?
rectum to anal opening
the internal anal sphincter is ?
involuntary; circular layer of smooth muscle
the external anal sphincter is ?
voluntary; skeletal muscle
Does the large intestines mucosa have any folds or villi?
no folds or villi
the muscularis externa of the large intestine has ?
teniae coli
what is teniae coli?
3 thick longitudinal bands of smooth muscle in the outer layer with thin layer of smooth muscles between the bands
what is the teardrop-shaped adipose-filled outpockets within the serosa throughout the colon
Appendices epiploicae
what are the 3 types of movement in the large intestine?
segmentation
peristalsis
mass action contraction
what is Hirschsprung Disease
a congenital disorder where ganglions are absent in myenteric and submucosal plexuses in distal colon resulting in lack of peristalsis and defecation rate of 1 every 3 weeks
what is the gastroileal reflex
Food leaving the stomach allows the cecum to relax which allows the ileocecal valve to relax and chyme to pass from SI to LI
what is the gastrocolic reflex
Large waves of peristalsis are stimulated by presence of food in the stomach after a meal
what causes distention of the rectum which initiates a reflex contraction of the rectal muscles and communicates to the CNS a desire to defecate
the presence of feces
what is involuntarily relaxed in response to inhibitory signals from sacral parasympathetic NS and distention
internal anal sphincter
what can voluntarily relax and expulsion of feces may occur unaided if enough pressure has been reached or supported by contraction of abdominal muscles
external anal sphincter
what innervates the external anal sphincter
pudendal nerve
what are the 3 components of inhibition of defecation
○ Both sphincters are tonically active
○ Puborectalis muscle maintains contraction
- Angle between rectum an anus is 90 degrees
what is the most common functional gastrointestinal disorder
Irritable Bowel Syndrome
what is visceral hypersensitivity?
increased pain sensation in the bowel; normal amount of distention causes atypical amount of pain
what is low-grade mucosal inflammation
Greater amount of immune cells infiltrating the colonic mucosa compared to healthy controls
- increased release of inflammatory cytokines
Crohn’s Disease includes ? which are ?
Discontinuous pattern - areas of healthy tissue between spots of ulceration
ulcerative colitis typically involves ?
rectum
what are small bulges or pockets within the lining of the large intestine
diverticula
what is inflammation or infection of the diverticula called
diverticulitis
what is the theory of sliding anal canal lining
Disintegration of supporting connective tissues surrounding the hemorrhoid allows for downward displacement of anal cushions and subsequent venous dilation
what is the clinical presentation of hemorrhoids
bright red blood on toilet tissue or surface of stool
will there be pain on defecation for hemorrhoids
yes for external hemorrhoids and no for internal hemorrhoids
