Large intestine and anal canal

Flashcards about the large intestine, anal canal, blood and nerve supply of the Gl

What are the three main functions of the large intestine?

Absorption of electrolytes and water, absorption and production of vitamins, formation and storage of semisolid stool and elimination of the stool as a waste product of digestion

What are the components of the large intestine?

Cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal and anus

What is the Tenia coli?

Condensation of longitudinal muscle fibers into prominent longitudinal bands

What is the Haustra?

Saccular formations that allow segmental contraction in the colon wall

What are Omental appendices?

Small fatty projections on the large intestine.

What parts of the large intestine are intraperitoneal?

Appendix, cecum, transverse colon, sigmoid colon

What parts of the large intestine are retroperitoneal?

Ascending colon, descending colon, rectum

Where is the Cecum located?

It lies in the right iliac fossa and is enveloped in the visceral peritoneum.

Where is the base of the appendix located?

The base of the appendix lies at McBurney’s point, 1/3 of the line connecting ASIS and umbilicus.

Where do Afferent nerve fibres from the appendix travel?

Afferent nerve fibres from the appendix accompany sympathetic nerves to the T10 segment of the spinal cord.

Where does the ascending colon turn?

The ascending colon turns to the left at the right colic flexure (hepatic flexure).

How is the transverse colon suspended?

The transverse colon is suspended to the posterior abdominal wall by the transverse mesocolon.

Where does the descending colon start and end?

It commences at the left (splenic) colic flexure and runs down to the left iliac fossa where continues as a sigmoid colon. It is secondary retroperitoneal.

What is Diverticulosis?

Outpouching of the wall (diverticulum) found predominantly in the descending and sigmoid colon.

What are the divisions of the pelvis?

Greater (false) pelvis and lesser (true) pelvis

What flexures does the rectum make in the sagittal section?

Sacral flexure and anorectal flexure

What peritoneal pouches are found in the female pelvis?

Vesicouterine pouch and rectouterine pouch

What peritoneal pouch is found in the male pelvis?

Rectovesical pouch

How long is the anal canal?

2. 5-3.5 cm long

What indicates the junction between hindgut derivative (above the line) and somatic derived from embryonic proctodeum (below the pectinate line)?

Dentate (pectinate) line

What are the anal sphincters?

Internal anal sphincter and external anal sphincter.

What triggers the defecation reflex?

Distention of the wall of the rectum

What arteries supply the rectum and anal canal?

Superior rectal artery, middle rectal arteries, and inferior rectal arteries

What veins drain the rectum and anus?

Superior, middle, and inferior rectal veins

What is the nerve supply of the upper half of the anal canal?

Supplied by the autonomic hypogastric plexuses, sensitive to stretch.

What is the nerve supply of the lower part of the anal canal?

Nerve supply is by somatic nerves (branches of the pudendal nerve), sensitive to pain, touch, pressure.

What are the three main branches of the celiac trunk?

Left gastric, splenic, and hepatic artery proper

What are the main branches of the superior mesenteric artery?

Inferior pancreatico-duodenal, middle colic, jejunal branches, ileal branches, ileocolic, and right colic

What are the three main branches of the inferior mesenteric artery?

Left colic, sigmoid branches, and superior rectal artery

What are the intrinsic and extrinsic sets of nerves that regulate the GI tract?

Enteric nervous system and autonomic nervous system (parasympathetic and sympathetic)

What are the two major types of sensory receptors in the wall of the GI tract?

Myenteric plexus (Auerbach’s plexus) and Submucosal plexus (Meissner’s plexus)

What is the level of Sympathetic innervation?

Spinal level T5 – L2

What is the level of Parasympathetic innervation?

Vagus nerve (CNX) and S2 –S4 spinal cord level

What are the Abdominopelvic splanchnic nerves?

Greater splanchnic nerve (T5 – T9), lesser splanchnic nerve (T10 and T11), and least splanchnic nerve (T12)

What nerve cells initiate the sensation of pain?

Nociceptors

How is Visceral pain described?

Poorly localized and dull

How is Somatic pain described?

Sharp, well localized