Lecture 14: Anatomy

Question 1

The greater omentum is attached to which part of the large intestine?

Answer 1

Transverse colon

Question 2

Describe the attachments of the greater omentum?

Answer 2

• Its a double sheet of peritoneum (ie. made up of 4 layers in total)
• It descends from the greater curvature of the stomach
• Hangs freely over the intestines.
• Double backs and attaches to the anterior surface of the transverse colon

Question 3

Describe the Transverse mesocolon?

Answer 3

Broad, meso-fold of peritoneum, which connects the transverse colon to the posterior wall of the abdomen

Question 4

Name these parts?

Answer 4

1. Greater omentum (turned up)
2. Transverse colon (turned up)
3. Right colic (hepatic) flexure
4. Small intestine (jejunum and ileum)
5. Ascending colon
6. Cecum
7. Urinary bladder

Question 5

Which parts of the large intestine have mesentery?

Answer 5

Appendix: mesentery is called mesoappendix

Transverse colon: mesentery is called transverse mesocolon

Sigmoid colon: mesentery is called sigmoid mesocolon

Question 6

Describe how the greater omentum attaches the stomach to the posterior abdominal wall?

Answer 6

• The greater omentum descends from the greater curvature of the stomach.
• Hangs over the intestine and folds back posteriorly attaching to the anterior suface of the transverse colon.
• The transverse colon has the transverse mesocolon attached (a fold of peritoneum), that attached it to the posterior wall of the abdomen.
• Hence the indirect attachment of the stomach to the posterior wall

Question 7

Which parts of the large intestine is retroperitoneal?

Answer 7

All the parts, except caecum, that does not contain mesentry.

Retroperitoneal: Ascending colon, descending colon, rectum and anal canal.

Question 8

The cecum does not have its own mesentery but is covered in all aspects by?

Answer 8

Peritoneum

Question 9

The peritoneum is comprised of which epithelium?

Answer 9

Simple squamous epithelial cells called mesothelium.

Question 10

Mnemonic SAD PUCKER is used to recall which abdominal viscera are retroperitoneal.

What does SAD PUCKER stand for

Answer 10

Suprarenal (adrenal) glands

Aorta

Duodenum (except the initial part)

Pancreas (Except the tail)

Ureters

Colon (ascending, descending)

Kidneys

Esophagus (oesphagus)

Rectum and anal canal

Question 11

What are the intraperitoneal organs?

Answer 11

Use the mnemonic:

Sick Individuals Judge The Seriously Supportive Dads.

Spleen

Ileum

Jejunum

Transverse colon

Stomach

Sigmoid colon

Duodenum (proximal part)

Question 12

How long is the small intestine and why does it appear longer in dissection?

Answer 12

3 metres in length

The SI is relaxed in dissection so may be longer

Question 13

Describe “The mesentry”?

Answer 13

The mesentry is the mesentry of the small intestine

(REMEMBER the “THE” part)

Double fold of peritoneal tissue that suspends the small intestine from the posterior wall

Fans out from the posterior wall to the small intestine.

Carries vessels to support the small intestine

Question 14

What indicates the start of the large intestine?

Answer 14

The ileocecal valve

Sphincter muscle that separates the small intestine and the large intestine

Question 15

What are the two flexures of the large intestine?

Answer 15

Right colic flexure also known as the hepatic flexure.

Left colic flexure aka the splenic flexure

Sharp bend of the large intestine

Question 16

Describe the right colic flexure?

Answer 16

• Also known as the hepatic flexure (due to its close proximity to the liver)
• Sharp bend between the ascending colon and the transverse colon
• Lies in the right hypochondrium region

Question 17

Describe the left colic flexure?

Answer 17

• Also known as the splenic flexure (due to its close proximity to the spleen)
• Sharp bend between the transverse colon and the descending colon
• Lies in the left hypochondrium region

Question 18

Describe the direction of the transverse colon

Answer 18

After the hepatic flexure, the large intestine crosses to the left hand side of the body and also moves superiorly.

Towards the spleen, it then has a sharp bend and becomes the descending colon

Question 19

At what point of the large intestine does it leave the abdominal cavity?

Answer 19

At the sigmoid colon level

Question 20

What are the different parts of the large intestine

Answer 20

Caecum

Ascending colon

Transverse colon

Descending colon

Sigmoid colon

Rectum

Question 21

Name these parts of the large intestine?

Answer 21

Question 22

Explain how the ascending, descending colon and rectum are retroperitoneum despite that these anatomical regions are very anterior

Answer 22

The peritoneum buldges forward over these regions and then returns back.

Question 23

What are the differences between the lumen of the large and small intesitne?

Answer 23

The lumen tends to be larger in the large intestine however can vary considerably and be as small as the small intestine.

Question 24

What are the 3 anatomical characteristics of the large intestine (that distinguish it from the small intestine)?

Answer 24

• Appendices epeploicae
• Haustrations
• Taenia coli

Question 25

Describe appendices epeploicae?

Answer 25

* Unique anatomical characteristic of the large intestine * They are little fatty tags along the large intestine that are covered with peritoneum.

Question 26

Name these unique characteristics of the large intestine?

Answer 26

Question 27

Describe haustrations?

Answer 27

* Singular haustra * Also known as sacculations * Unique characteristic of the large intestine * These are the small pouches caused by sacculation * The sacculations are caused by the contraction of taeniae coli

Question 28

Describe how the taenia coli forms the sacculation of the large intestine?

Answer 28

The taenia coli run the length of the large intestine. Because the taenia coli are shorter than the large bowel itself, the colon becomes sacculated, forming the haustrations

Question 29

Describe taenia coli?

Answer 29

* Three bands of smooth muscle * Thickened area of smooth muscle * Located on the outside of the ascending, transverse, descending and sigmoid colons * Can only see one ribbon of smooth muscle at the time due to the location (each located at different edges of the large intestine)

Question 30

Describe the appendix?

Answer 30

* Not involved in digestion * Contains a small amount of mucosa-associated lymphoid tissue which gives it an undetermined role in immunity * Most often it hangs freely from the abdominal cavity * Sometimes it can be retrocecal (localized behind the cecum)

Question 31

The ascending colon includes?

Answer 31

The caecum and appendix

Question 32

What are paracolic gutters?

Answer 32

Spaces between the colon and the abdominal wall

Question 33

What is a key histological characteristic of the appendix?

Answer 33

Large number of lymph tissue (due to its undetermined role in immunity)

Question 34

If the appendix burst, where does the fecal material tend to go in bed-bound patients?

Answer 34

Tend to go into the pelvic cavity

Question 35

Describe the Morison's pouch?

Answer 35

* Also known as the hepatorenal recess * Deepest recess in the abdominal cavity * Potential space that separates the liver from the right kidney * Normal physiological conditions, it is not filled with fluid

Question 36

When the appendix burst, where does the faecal matter run towards in patients lying down?

Answer 36

Towards the hepatorenal recess and rectrouterine pouch. These are the two deepest recesses of the abdominal cavity.

Question 37

Describe the Rectouterine pouch?

Answer 37

* Also known as the Pouch of Douglas * An extension of the peritoneal cavity between the rectum and back wall of the uterus (in the **female** body) * Note the rectouterine pouch is deeper than the vesicouterine pounch (space between bladder and uterus)

Question 38

What is the significancy of the paracolic gutters in a burst appendix patient?

Answer 38

The fecal material can run down the **right** **paracolic** **gutter** and run into deeper recesses.

Question 39

Describe the superior mesenteric artery?

Answer 39

* Major artery of the abdomen. * It arises from the abdominal aorta, and supplies arterial blood to the organs of the midgut * which spans from the major duodenal papilla (of the duodenum) to the proximal 2/3 of the transverse colon. * Arises immediately inferior to the origin of the coeliac trunk

Question 40

What are the three major anterior branches of the abdominal aorta?

Answer 40

Superior mesenteric artery Inferior mesenteric artery Coeliac trunk

Question 41

Name these branches of the superior mesenteric artery?

Answer 41

The inferior pancreatoduodenal artery arises more proximally, and is not visible on this illustration

Question 42

Describe the Inferior Pancreaticoduodenal Artery

Answer 42

* First branch of the superior mesenteric artery * Forms anterior and posterior vessels * Anastomose with branches of the superior pancreaticoduodenal artery

Question 43

Describe the jejunal and ileal arteries branches?

Answer 43

* Numerous arteries that supply the jejunum and ileum. * The arteries pass between the layers of the mesentery and form anastomotic arcades * from which smaller, straight arteries arise to supply the organs

Question 44

Describe the differences between the ileal and jejunal arteries (branches from the superior mesenteric artery)

Answer 44

The _jejunal_ blood supply is characterised by a **smaller** **number of arterial arcades, but longer vasa recta**. In contrast, the _ileal_ blood supply is marked by **more arterial arcades with shorter vasa recta**

Question 45

Describe anastomotic arcades?

Answer 45

Arcades are a series of anastomosing arterial arches between the arterial branches of the jejunum and ileum More in the ilieal branches than the jejunal branches.

Question 46

What does the Middle colic artery supply?

Answer 46

Supplies the transverse colon

Question 47

What does the right colic artery supply?

Answer 47

Ascending colon

Question 48

Describe the vasa recta?

Answer 48

the straight arterioles coming off from arcades in the mesentery of the jejunum and ileum, and heading toward the intestines

Question 49

What does the ileocolic artery supply?

Answer 49

It is the final major branch of the superior mesenteric artery. It passes inferiorly and to the right, giving rise to branches to the ascending colon, appendix, cecum, and ileum

Question 50

Describe the blood supply to the splenic flexure?

Answer 50

Dual blood supply from the terminal branches of the superior mesenteric artery and the inferior mesenteric artery Prone to ischemic damage in cases of low blood pressure because it does not have its own primary source of blood

Question 51

The superior rectal artery is a continuation of which artery?

Answer 51

Inferior mesenteric artery

Question 52

The superior rectal artery supplies which areas of the GI tract?

Answer 52

Rectum and anal canal