Rectum, Liver, and Biliary system

Question 1

What is the function of the rectum?

Answer 1

Accumulates and temporarily stores faeces.

Question 2

Is the rectum retroperitoneal or intraperitoneal?

Answer 2

It is retroperitoneal (and subperitoneal)

Question 3

Where is the rectum located? (spinal level)

Answer 3

Extends from S3 to the anal canal.

Ends anteroinfertior to tip of coccyx as GIT pierces the pelvic diaphragm.

Question 4

Does the rectum have teniae coli?

Answer 4

No

Question 5

How is the rectovesical pouch formed in males and the rectouterine pouch in females?

Answer 5

It is formed from anterior and lateral reflections of peritoneum.

Question 6

Which arteries supple the rectum?

Answer 6

Arterial perfusion via branches of the inferior mesenteric artery and internal iliac arteries.

Question 7

Which veins drain the rectum?

Answer 7

Anastomosis between portal and systemic veins in wall of anal canal.

Superior rectal vein drains back to the inferior mesenteric vein (=> splenic => portal vein)

Middle rectal veins drain back to internal iliac veins.

Anastomosis between rectal veins.

Question 8

What provides rectum with nerve innervation?

Answer 8

Sympathetic: Lumbar splanchnic nerves

Parasympathetic: Pelvic splanchnic nerves

Visceral afferent: Rectum inferiot to pelvic pain line meaning the visceral afferent fibers follow parasympathetic innervation (Pelvic splanchnic nerves) retrogradely back to S2 - S4 spinal sensory ganglia.

Question 9

What structures can be palpated in males through the walls of the rectum?

Answer 9

Seminal vesicles

Prostate gland

Pelvic surface of sacrum and coccyx

Question 10

What structures can be palpated in females through the walls of the rectum?

Answer 10

Cervix

Pelvic surface of sacrum and coccyx

Question 11

What does the internal anal sphincter do?

Answer 11

Smooth involuntary contraction stimulated by sympathetic fibers; parasympathetic fibers from pelvic splanchnic nerves inhibit sympathetic contraction and evoke peristaltic contraction for defaecation.

Question 12

What does the external anal sphincter do?

Answer 12

Large voluntary sphincter

Question 13

What nerve supplies the external anal sphincter?

Answer 13

The pudendal nerve

Question 14

What causes external haemorrhoids?

Answer 14

Straining to pass stools

Question 15

What is an anal fissure? Why is this important?

Answer 15

An anal fissure is a cut or a tear in the thin, delicate lining of the anus. This can potentially get infected and spread infection to fat which is very hard to treat.

Question 16

What muscle creates a sling in the rectum to maintain faecal continence?

Answer 16

Puborectalis (Pubic symphysis to the rectum)

*This muscle can be stretched in mothers after giving birth

Question 17

What nerves deliver sympathetic fibers to descending and sigmoid colons?

Answer 17

Lumbar splanchnic nerves from L1 - L2/L3

Question 18

What nerves deliver parasympathetic fibers to descending and sigmoid colon?

Answer 18

Pelvic splanchnic nerves from S2 - S4

Question 19

What nerves do visceral afferent fibers follow from proximal to middle sigmoid colon?

Answer 19

Visceral afferent pain fibers follow sympathetic

Reflex fibers follow vagal parasympathetics.

Question 20

What nerves do visceral afferent fibers follow from middle to distal sigmoid colon?

Answer 20

All visceral afferent fibers retrogradely follow splanchnic nerves back to S2 - S4

Question 21

What is the largest gland in the body?

Answer 21

The liver

Question 22

Where does liver arise from?

Answer 22

Grows as an outgrowth of gut plus mesoderm

Question 23

Where is the visceral surface located? What is located on this surface?

Answer 23

Down and left. (related to stomach, duodenum, right kidney, right colonic flexure, and bears the gall bladder)

Question 24

What type of tissue are the ligaments in the peritoneal cavity?

Answer 24

They are peritoneal folds. (Not true ligament) They have little or no supporting function.

Question 25

What ligaments are related to the liver?

Answer 25

Ligamentum teres hepatis

Ligamentum venosum

Round ligament of the uterus

Question 26

What surface has the ligamentum teres? What other ligament is there and where do they come from?

Answer 26

The diaphragmatic surface.

Ligamentum venosum is also on this surface. Both ligaments come from embryonic hepatic artery and portal vein respectively.

Question 27

How does bile get to the duodenum?

Answer 27

Right and left hepatic ducts are joined by cystic duct to form the common bile duct.

Question 28

What does the gall bladder do?

Answer 28

Body and fundus absorb salt and water.

Gall bladder also stores bile which is released in response to cholecystokinin.

Question 29

What are signs of gall bladder problems or bile production issues?

Answer 29

Pale coloured stools and pain from adjacent areas caused by distension of gall bladder.

Jaundice can also result from backing up of bile into the liver.

Question 30

Where does the liver get its blood supply from?

Answer 30

Gets a big branch from the coeliac trunk called the common hepatic artery

Gets portal circulation

Plexus in GIT wall

Porta-systemic anastomoses

Hepatic veins

Question 31

What does the portal vein do?

Answer 31

All the blood flow that leaves the aorta in GI arteries returns via the portal vein and liver.

Question 32

How does the interior mesenteric vein get to the portal vein?

Answer 32

The inferior mesenteric vein joins the splenic vein that joins the superior mesenteric vein. All GIT blood goes in the portal vein to the liver.

Hepatic veins empty the blood from the liver into the IVC.

Question 33

Do veins in the abdomen have valves?

Answer 33

No, they only have valves in the arms and the legs because of the pressure differential.

Question 34

What are the nearest valves to the heart? What do they do?

Answer 34

Femoral, subclavian, jugular, and internal iliac.

They prevent blood from being forced out of the torso by raised intra-abdominal pressure (eg during coughing, straining, talking)

Most smaller veins of the torso also have no valves.

Question 35

What do portocaval anastomoses do?

Answer 35

They allow blood which would normally drain into the portal vein and liver to enter the venae cavae without passing through the liver.

Question 36

Where are portocaval anastomoses located?

Answer 36

Gastro-oesophageal (Oesophageal tributaries of the right gastric and oesophageal tributaries azygous vein connect)

Ano-rectal (Superior rectal beins drain to the portal but middle and inferior rectal veins drain into internal iliac and IVC but both drain same tissue)

Bare areas (Any organ that lies on the body wall has capillaries that cross from the organ to and from the body wall - these vessels can enlarge and become important)

Question 37

What is caput medusa?

Answer 37

Portal hypertension causes swelling on anterior abdominal wall visible superficially.

Question 38

Where are abdominal autonomic plexus located?

Answer 38

They surround the aorta and its branches.

Question 39

Where is the intermesenteric plexus located?

Answer 39

4 - 12 nerves on the aorta

Has renal, ovarian, and ureteric branches. (around the respective arteries)

Question 40

Where is the superior hypogastric plexus located? What plexuses does it form?

Answer 40

From lumbar sympathetic chain anterior to inferior aorta.

Forms R/L hypogastric nerves

Forms ureteric plexuses

Question 41

What does the inferior hypogastric plexus form?

Answer 41

Superior plexus on iliac arteries, uterus, bladder, and rectum.

Question 42

What provides parasympathetic innervation to the GI tract from the palatoglossus to the left colic flexure?

Answer 42

The vagus nerve (CN X)

Question 43

What provides sympathetic innervation to the superior abdomen?

Answer 43

Via greater, lesser, and least splanchnic nerves.

These nerves carry pre-synaptic fibers from IML in spinal cord to ganglia on aorta surrounding major arteries.

Post-synaptic sympathetic fibers extend from these ganglia to target organs.