Sem 1 - M - Midgut & Hindgut - Jejunum/ileum/caecum/appendix/ascending-transverse-descending-sigmoid colon/rectum

Question 1

What are the organs of the foregut?

Answer 1

Distal oesophagus Stomach Liver Gallbladder Spleen Mid duodenum 1/2 of pancreas

Question 2

What are the organs of the midgut?

Answer 2

Distal 1/2 of duodenum 1/2 of pancreas Jejunum Ileum Caecum and appendix Ascendingn colon 2/3rds of the transverse colon

Question 3

What are the organs of the hindgut?

Answer 3

Distal 1/3rd of the transverse colon Desscending colon Sigmoid colon Rectum Proximal 1/2 of anal canal

Question 4

The midgut contains both the small and large intestine (part of it) What branch of the abdominal aorta supplies the midgut? WHat branch of the abdominal aorta supplies the hindgut?

Answer 4

Coeliac trunk branch of the abdominal aorta at T12 supplies the foregut Superior mesenteric branch of the abdominal aorta at L1 supplies the midgut Inferior mesenteric branch of the abdominal aorta at L3 supplies the hindgut

Question 5

What is the actual length of the small intestine? What are the parts of the small intestine?

Answer 5

The actual length of the small intestine is 6m long The small intestine consists of the duodenum (dual supply - from coeliac trunk and SMA), jejunum and ileum

Question 6

Jejunum begins at the duodeno-jejunal junction * How long is the duodenum? * What proportion of the small intestine is from duodeno-jejunal junction to ileum? * What proportion of the small intestine is from the ileum to the ileo-caecal junction?

Answer 6

The duodenum is approximately 25 cm long The proximal 2/5ths of the small intestine runs from the duodeno-jejunal junction to the ileum The distal 3/5ths of the small intestine runs from the ileum to the ileocaecal junction

Question 7

What is the fan shaped fold of peritoneum that encloses the gut tube known as? It allows for the ingress/egress of vessels lymph and nerves

Answer 7

This would be the mesentery The mesentery suspends the small intestine from the posterior abdominal wall

Question 8

In gross anatomy, it is not that easy to tell the difference between the jejunum and ileum There are differences in the individuals between the appearance, the wall, the bore (lumen), mesenteric vessels, adipose tissue and lymphoid tissue Describe the differences between the jejunum and ileum in terms of appearance, the wall and the bore?

Answer 8

Jejunum Upper part of the small intestine and is red Thicker &has more plicae circularis - intestinal folds Has a wider bore

Ileum Lower part of the small intestine and is pale Thinner and has less plicae circularis Narrow bore

Question 9

Describe the differences between the jejunum and ileum in terms of mesenteric vessel aracades and the branches to the intestinal wall

Answer 9

The arterial arcades are a series of anastomosing arterial arches between the arterial branches of the jejunum and ileum. Mesenteric vessels The jejenum has 1 or 2 arcades with long branches to the intestinal wall The ileum has 3or4 arcades with short branches to the intestinal wall

Question 10

Describe the difference between jejunum and ileum in terms of adipose and lymphoid tissue

Answer 10

Jejenum - most of the adipose tissue is near the root of the mesentery small amount of lymphoid tissue Ileum The adipose tissue is all throguh the mesentery There are numerous lymphoid Peyer’s patches

Question 11

Describe the differences between jejunum and ileum * Appearance * Wall * Bore * Mesenteric vessels * Adipose tissue * Lymphoid tissue

Answer 11

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Question 12

What are the branches of the superior mesenteric artery that supply the small intestine? Do they branch off the left side of the SMA or the right hand side?

Answer 12

These would be the jejunal and ileal branches of the SMA They branch off the left side of the SMA The arterial branches coming from the right side of the SMA are the branches supplying the large intestine

Question 13

The jejunal and ileal arteries anastamose to form arcades What are the lower parts of the ileum also supplied by? Where is the venous drainage of the midgut?

Answer 13

Lower parts of the ileum also supplied by the ileocolic arteries Venous drainage of the midgut is to the superior mesenteric vein

Question 14

What is the lymph drainage of the small intestine? What is the ANS supply to the small intestine?

Answer 14

Lymph drainage is to the mesenteric nodes and then to the pre-aortic superior mesenteric nodes at L1 ANS supply is form superior mesenteic plexus and pain is to the umbilical region

Question 15

Once the lymph is drained from the mesenteric nodes to the superior mesenteric nodes, where does it go?

Answer 15

The lymph then drains to the intestinal lymph trunk which opens into the cisterna chyli which continues into the thoracic duct

Question 16

What is the function of the large intestine?

Answer 16

The function off the large intestine aka the colon, is too absorb water and electrolytes as well as to store undigested material until expelled from the body

Question 17

What is the longitudinal muscle layer of the large intestine that is collected into three bands known as?

Answer 17

This is the teniae coli The teniae coli is a smooth muscle layer continous from the small intestines

Question 18

The three distinct bands of smooth muscle that run longitudinally in the large intestine are known as the teniae coli The teniae coli run the length of the large intestine and contract lengthwise to produce sacculations in the large intestine known as what?

Answer 18

The sacculations in the large intestine are known as the haustra

Question 19

What are the little fatty tags of the large intestine known as? Do they exist on the small intestine?

Answer 19

These small fatty tags are known as appendices epiploicae - these are small fatty stores The appendices epiploicae do not exist on the small intestine

Question 20

The dark areas in the barium contrast are gas/air Where does the small intestine become the large intestine? What region of the abdomen is this found in? What continues from the first part of the large intestine?

Answer 20

The small intestine becomes the large intestine at the ileocaecal junction - where the ileum enters the caecum The caecum is found in the right iliac fossa The ascending colon is continous with the caecum

Question 21

What does the ileocaecal valve act to prevent? What forms the action of the sphincter?

Answer 21

The ileocaecal valves acts to prevent the reflux of colonic contents from the large intestine into the small intestine The circular layer of the ileum (one of the layers of the muscularis externa) forms the action of the sphincter

Question 22

What muscles does the caecum sit on top off? What is the arterial supply to the caecum?

Answer 22

The caecum sits anterior to the psoas major and iliacus muscles which form the iliopsoas muscle - a powerful flexor of the hip The caecum is supplied by the (anterior and posterior) caecal branches of the ileocolic artery - a branch of the superior mesenteric artery

Question 23

What is the venous and lymphatic drainage of the caecum? Where does the nerve supply to the caecum come from? What is the caecum’s mesentery known as?

Answer 23

Drains blood from veins to the superior mesenteric Drains lymph to the pre-aortic superior mesenteric nodes at L1 Nerves - ANS comes from the superior mesenteric plexus The caecum does not have its own mesentery but is covered in all aspects by peritoneum

Question 24

What does the length of the appendix range from? What is the full name of the appendix? (named after its worm like structure) What is the theorized function of the appendix?

Answer 24

Length of the appendix -anything from 2-20cm in length Its full name is the vermiform appendix Theorized function is an immune and bacterial store

Question 25

What region of the abdomen is appendix found? Where does the appendix sit in relation to the caecum?

Answer 25

The appendix is found in the right iliac fossa - usually 1/3rd along a line drawn from ASIS to umbilicus (McBurney’s point) The appendix often sits retro-caecally

Question 26

The appendix, tranverse colon and sigmoid colon all have their own mesentery, what is this known as?

Answer 26

Appendix mesentery - mesoappendix mesentery Transverse colon mesentery - transverse mesocolon Sigmoid mesentery - sigmoid mesocolon

Question 27

As said, the vermiform appendix has a small mesoappendix mesentery What is the blood supply to the appendix?

Answer 27

The blood supply to the appendix is via the appendicular artery - a branch of the ileocolic artery branch of the SMA

Question 28

The lymphatic drainage and nerve supply to the caecum is the appendix is the same as the caecum How does the appendix drain to the superior mesenteric vein? Where is pain from the appendix felt?

Answer 28

The appendix drains to the superior mesenteric vein via the posterior caecal vein Pain from the appendix is felt in the umbilical region - T10 dermatome

Question 29

What length is the ascending and descending colon? Why is the ascending colon usually a little shorter than the descending colon?

Answer 29

The ascending colon is approx 15cm in length The descending colon is approx 25cm in length The difference in length between ascending and descending colon is due to the presence of the liver at the right hypochondrium

Question 30

Which parts of the colon inta, retro and infraperitoneal?

Answer 30

Intraperitoneal - caecum, appendix, transverse and sigmoid colon Retroperitoneal - ascending and descending colon and upper 2/3rds of rectum Infraperitoneal - lower 1/3rd of rectum and anal canal

Question 31

The ascending colon has relations to the small intestine, greater omentum, iliacus, quadratus lumborum, right kidney, ilioinguinal and iliohypogastric nerves What is the arterial supply to the ascending colon?

Answer 31

The ileocolic artery from the superior mesenteric artery will supply the proximal ascending colon The right colic artery will supply the distal ascending colon and the hepatic flexure (Right colic flexure)

Question 32

What is the venous and lymphatic drainage of the ascending colon? What is the nerve supply to the ascending colon?

Answer 32

Veins drain to the superior mesenteric vein Lymph drains to the superior mesenteric nodes at L1 Ascending colon nerve supply comes form the superior mesenteric plexus

Question 33

The transverse colon is the junction from foregut to midgut What is the approximate length of the transverse colon? STATE AGAIN THE LENGTHS OF THE ASCENDING AND DESCENDING COLON What hangs over the anterior surface of the transverse colon? What attaches the transverse colon to the posterior body wall?

Answer 33

• Transverse colon is approx (~) 38 cm in length
• Ascending colon is ~ 15 cm
• Descending colon is~ 25cm
• The greater omentum hangs over the anterior surface of the transverse colon
• The transverse colon is attached to the posterior body wall via the transverse mesocolon

Question 34

As the transverse colon traverses the midgut and hindgut, it will have a dual blood supply and venous/lymph drainage What is the blood supply, venous drainage and lymph drainage to/from the transverse colon?

Answer 34

• Arterial blood supply
  
  • * Proximal 2/3rds - middle colic artery branch of SMA
  • * Distal 1/3rd - left colic artery branch of IMA
    
    • Venous drianage-
  • * Proximal 2/3rds drain to superior mesenteric vein * Distal 1/3rd drains to inferior mesenteric vein which drains to splenic vein Lymph drainage * Proximal 2/3rds to superior mesenteric nodes * Distal 1/3rd to inferior mesenteric nodes

Question 35

What is the nerve supply to the tranvserse colon?

Answer 35

ANS sympathetics from the superior and inferior mesenteric plexuses Parasympathetic nerve supply from the vagus nerve for the proximal 2/3rds Parasympathetic nerve supply from pelvic splanchnic nerves (S2-4) for the distal 1/3rd

Question 36

What does the descending colon extend from?

Answer 36

Descending colon is approx 25 cm long Extends from the left colonic flexure to the pelvic brim where it becomes the sigmoid colon

Question 37

Descending colon is Related to small intestine, greater omentum, L kidney, quadratus lumborum, psoas, femoral & iliohypogastric & ilioinguinal nerves What is its arterial supply, venous and lymphatic drainage?

Answer 37

Arterial supply Left colic and sigmoid arteries - both branches of the inferior mesenteric artery Veins drain to the inferior mesenteric vein Lymphatic drainage - to the pre-aortic inferior mesenteric nodes at L3

Question 38

What is the nerve supply to the descending colon?

Answer 38

Sympathetics from inferior mesenteric plexus an parasympathetics from pelvis (sacral nerves 2-4)

Question 39

Ascending colon - approx 15cm Transverse colon - approx 38cm Descending colon - approx 25 cm What is the approximate length of the sigmoid colon? Where does the sigmoid colon start and end?

Answer 39

The approx length of the sigmoid colon is 25-38 cm from the left external iliac artery to the 3rd sacraal vertebra

Question 40

Sigmoid colon is attached to the posterior abdominal wall by what? What are the different anatomcial relations in males and females?

Answer 40

It is attached to the posterior abdominal wall by the sigmoid mesocolon Anatomical relations Males - urinary bladder, rectum and sacrum Females - uterus, vagina, rectum and sacrum

Question 41

What is the arterial supply to the sigmoid colon? What is the venous drainage of the sigmoid colon? What is the lymph drainage? What is the nerve supply?

Answer 41

• Arterial supply - sigmoid arteries from the inferior mesenteric artery
• Venous drainage - veins drain to inferior mesenteric vein
• Lymph drainage - to pre-aoartic nodes at L3 around the inferior mesenteric artery
• Nerve supply - ANS from inferior hypogastric plexus

Question 42

Name the arterial branches of the SMA and IMA that supply the colon from right to left? Which branches form the marginal artery? (a continuous arterial circle along the inner border of the colon.)

Answer 42

SMA

• Ileocolic artery
• Right colic artery
• Middle colic artery

IMA

• Left colic artery
• Sigmoid arteries
• Superior rectal artery

Marginal artery - left colic, middle colic and right colic arteries)

Question 43

What is the length of the rectum? Where does the descending colon, sigmoid colon and rectum begin and stop?

Answer 43

Rectum - approx 13cm in length Descending colon - begins at left colic flexure and stops at pelvic brim where it becomes sigmoid colon Sigmoid colon - begins at pelvic brim (in front of left external iliac artery) and ends at 3rd sacral vertebra Rectum - begins at 3rd sacral vertbra and ends 2cm in front of tip of coccyx where it pierces the pelvic diaphragm to become the anal canal

Question 44

What is the arterial supply to the rectum?

Answer 44

Arterial supply - Superior rectal artery (from IMA) Middle rectal artery -(internal iliac artery) Inferior rectal artery (internal pudendal artery)

Question 45

What is the venous drainage of the rectum? There is an anastomoses formed by the drainage routes of the rectum, what is this anastamoses known as?

Answer 45

Superior rectum to portal system via inferior mesenteric vein but Middle and inferior rectum to internal iliac and internal pudendal vein

• This is the portal systemic anastamoses

Portal part goes to the portal vein

Systemic part goes to the IVC

Question 46

Where is lymph from the rectum drained to? What is the nerve supply to the rectum?

Answer 46

Lymph drainage - upper rectum to inferior mesenteric nodes Lower rectum to internal iliac nodes Nerve supply -ANS from the inferior hypogastric plexus

Question 47

Areas of dual blood supply in the gut are Duodenum - proximal is foregut, distal is midgut (also pancreas) Transverse colon - Proximal 2/3rds if midgut, distal 1/3rd is hindgut Rectum - upper part is hindgut, lower part is pelvis State the SPECIFIC arteries

Answer 47

• Duodenum -
  
  • * superior pancreaticoduodenal artery (branch of gastroduodenal from common hepatic from coeliac)
  • * inferior pancreaticoduodenal artery (branch of IMA)
• Transverse colon
  
  • * Middle colic (branch of SMA)
  • * Left colic (branch of IMA)
• Rectum
  
  • * Superior rectal artery (branch of IMA)
  • * Middle rectal artery (branch of internal iliac)
  • * Inferior rectal artery (branch of internal pudendal)