Large intestine, rectum, anus Flashcards
Name the structures through this sagittal section of the abdomen
Structure of LI
- What are teniae coli
- where do they begin
- How do they terminate
- What do they form when they contract lengthwise
- 3 distinct bands of SM that run longitudinally
- Begin at the appendix
- Terminate by merging together at the rectosigmoid junction
- Contract lengthwise to form haustra
What are omental appendices
What are they also known as
Small fatty projections that are only found on the colon
epiploic appendages/appendices epiploicae
How do the haustrations and sacculations form
Wall becomes baggy and gathered
What are haustra
- Contraction of the teniae coli results in the shortening of the intestinal wall
- Sacculations form as the wall becomes “baggy” and gathered
- Visible on external surface
What are semilunar folds
- Haustra are internally separated by prominent ridges of mucosa
- Visible on the internal surface
- also PLICAE SEMILUNARIS
Peristalsis
Ripple-like wave of circular and longitudinal muscular contractions forcing material to propel forwards
Segmentation
Circular muscular contractions that mix and churn material forwards and backwards
Ileocecal junction
Marks junction between SI and LI when the ileum empties content into cecum via ileocecal valve
Ileocecal valve
- Formed by 2 semilunar shaped flaps that surround a slit-like orifice
- Located approximately 2cm above the opening of the appendix
- Acts to prevent REFLUX of chyme from the cecum back into ileum when digested material is acting against gravity to be propelled up the ascending colon
- Ileocolic lips create a passive flap valve that remains closed with tonic contractions
What is the cecum in relation to the ascending colon
First part of LI and is continuous with the ascending colon
Where is the cecum located
Right lower quadrant (RLQ)
Is the cecum intraperitoneal or retroperitoneal
Intraperitoneal as it can be lifted relatively freely and is entirely covered in a visceral layer of peritoneum
How is the cecum bound to the posterior abdominal wall
By cecal folds instead of having its own mesentery
Arterial supply of the cecum
Ileocolic artery (from the superior mesenteric)
What is the appendix
A 6-10cm blind intestinal diverticulum, containing masses of lymphoid tissue
Where is the appendix located
Right lower quadrant (RLQ)
McBurney’s point pain
Is the appendix intraperitoneal or retroperitoneal
INTRAPERITONEAL
How is the appendix held in place
By a short, triangular mesentery called the MESOAPPENDIX, arising from the posteromedial aspect of the cecum