S7) Anatomy for Dissection — Liver, Jejunum, Ileum, Colon

Question 1

Describe the anatomical position of the liver

Answer 1

The liver is located in the right hypochondrium and epigastric areas, extending into the left hypochondrium

Question 2

There are two surfaces of the liver.

Identify them

Answer 2

• Diaphragmatic surface (anterosuperior surface of the liver)
• Visceral surface (posteroinferior surface of the liver)

Question 3

The diaphragmatic surface is the anterosuperior surface of the liver.

Describe its structure.

Answer 3

• It is smooth and convex, fitting snugly beneath the curvature of the diaphragm
• A section is not covered by visceral peritoneum (‘bare area’) of the liver

Question 4

The visceral surface is the posteroinferior surface of the liver.

Describe its structure.

Answer 4

• It is irregular and flat due to the presence of surrounding organs
• It lies in contact with the oesophagus, right kidney, right adrenal gland, right colic flexure, duodenum, gallbladder and the stomach

Question 5

Describe the superior anatomical relations of the liver

Answer 5

Superior to the liver is the diaphragm (separating the abdominal cavity from the thoracic cavity)

Question 6

Describe the anterior anatomical relations of the liver

Answer 6

Anterior to the liver is the anterior abdominal wall and ribcage

Question 7

Describe the posterior anatomical relations of the liver

Answer 7

Posterior to the liver are the oesophagus, stomach, gallbladder, first part of the duodenum (the foregut-derived organs)

Question 8

Describe the structure and function of the various ligaments of the liver

Answer 8

• Structure: formed by a double layer of peritoneum
• Function: attach the liver to the surrounding structures

Question 9

Identify the 5 ligaments of the liver

Answer 9

• Falciform ligament
• Coronary ligaments
• Triangular ligaments
• Hepatoduodenal ligament
• Hepatogastric ligament

Question 10

Describe the anatomical position of the falciform ligament

Answer 10

• Attaches the anterior surface of the liver to the anterior abdominal wall
• Its free edge contains the ligamentum teres (a remnant of the umbilical vein)

Question 11

Describe the anatomical position of the coronary ligaments

Answer 11

• Anterior and posterior folds
• Attach the superior surface of the liver to the diaphragm

Question 12

Describe the anatomical position of the triangular ligaments

Answer 12

• Left and right ligaments
• Attach the superior surface of the liver to the diaphragm

Question 13

What does the lesser omentum consist of (in relation to the liver)?

Answer 13

• Hepatoduodenal ligament attaches the liver to the duodenum
• Hepatogastric ligament attaches the liver to the stomach

Question 14

Describe the attachment of the liver to the inferior vena cava

Answer 14

The posterior surface of the liver is secured to the inferior vena cava by hepatic veins and fibrous tissue

Question 15

What is the name of the fibrous layer covering the liver?

Answer 15

Glisson’s capsule

Question 16

The liver is divided by the attachment of the falciform ligament.

Identify the individual lobes formed

Answer 16

Question 17

Two ‘accessory’ lobes that arise from the right lobe, and are located on the visceral surface of liver.

Identify them

Answer 17

• Caudate lobe
• Quadrate lobe

Question 18

Describe the anatomical position of the caudate lobe of the liver

Answer 18

• Located on the upper aspect of the visceral surface
• Lies between the inferior vena cava and a fossa produced by the ligamentum venosum (a remnant of the fetal ductus venosus)

Question 19

Describe the anatomical position of the quadrate lobe of the liver

Answer 19

• Located on the lower aspect of the visceral surface
• Lies between the gallbladder and a fossa produced by the ligamentum teres (a remnant of the fetal umbilical vein)

Question 20

What is the porta hepatis and what does it do?

Answer 20

• The porta hepatis is a deep fissure between the caudate and quadrate lobes
• It transmits almost all the vessels, nerves and ducts entering or leaving the liver

Question 21

Identify the structures in the porta hepatis

Answer 21

• Right and left hepatic ducts (bile)
• Right and left branches of hepatic artery
• Hepatic portal vein

NB. Porta hepatis doesn’t transmit the hepatic veins

Question 22

What does the hepatic artery do and where is it derived from?

Answer 22

• Hepatic artery supplies the liver with arterial blood
• It is derived from the coeliac trunk

Question 23

What does the hepatic portal vein do?

Answer 23

Hepatic portal vein is the dominant blood supply to the liver parencyma, supplying the liver with deoxygenated blood and carrying nutrients absorbed from the small intestine

Question 24

Identify the 3 main tributaries of the hepatic portal vein

Answer 24

Question 25

Where is the hepatic portal vein formed?

Answer 25

It is formed behind the upper edge of the **neck of the pancreas**

Question 26

Describe the structure, function and location of the gallbladder

Answer 26

- **Structure**: peritoneal structure, gastrointestinal organ - **Function**: stores and releases bile - **Location**: right hypochondriac region of the abdomen, lies fossa between the right lobe and quadrate lobe of the liver

Question 27

The gallbladder can usually be divided into three parts. Identify them

Answer 27

Question 28

What is the fundus of the gallbladder?

Answer 28

The **fundus** is the rounded, end portion of the gallbladder; which projects into the inferior surface of the liver

Question 29

What is the body of the gallbladder?

Answer 29

The **body** is the largest part of the gallbladder and is occasionally in contact with the transverse colon and proximal duodenum

Question 30

What is the neck of the gallbladder?

Answer 30

The **neck** is the tapered region which becomes continuous with the cystic duct, leading to the biliary tree

Question 31

What is the biliary tree?

Answer 31

- The **biliary tree** is the series of ducts through which bile is secreted from the gallbladder into the gastrointestinal tract - These ducts extend from the **liver**, communicating with the **gallbladder** and **pancreas**, and end at an opening into the **duodenum**

Question 32

Describe the anterosuperior, posterior, inferior anatomical relations of the gall bladder

Answer 32

- **Anteriorly and superiorly:** inferior border of the liver and anterior abdominal wall - **Posteriorly**: transverse colon and the proximal duodenum **- Inferiorly**: biliary tree and duodenum

Question 33

Describe the anatomical position of the jejunum and ileum

Answer 33

- **Distal** parts of the small intestine - **Intraperitoneal** organs (unlike duodenum) - Attached to the posterior abdominal wall by **mesentery**

Question 34

There is no clear external demarcation between the jejunum and ileum although the two parts are macroscopically different. Where do these structures start and end?

Answer 34

- The **jejunum** begins at the **duodenojejunal flexure** - The **ileum** ends at the **ileocecal junction**

Question 35

What happens at the ileocecal junction?

Answer 35

- The ileum invaginates into the cecum to form the **ileocecal valve** **-** This valve cannot control movement of material into the cecum but prevents reflux of material back into the ileum

Question 36

Distinguish between the ileum and jejunum in terms of the following characteristic features: - Position - Intestinal wall - Vasa recta - Arcades - Colour

Answer 36

Question 37

Describe the arterial supply of the jejunum and ileum

Answer 37

The arterial supply to the jejunoileum is from the **superior mesenteric artery** which arises from the aorta at the level of the L1 vertebrae

Question 38

Describe the arterial distribution to the jejunum and ileum

Answer 38

- SMA moves in between layers of mesentery, splitting into approximately 20 branches - These branches anastomose to form loops, called **arcades** - From the arcades, long and straight arteries arise, called **vasa recta**

Question 39

Describe the venous drainage of the jejunum and ileum

Answer 39

- The venous drainage is via the **superior mesenteric vein** **-** It unites with the **splenic vein** at the neck of the pancreas to form the **hepatic portal vein**

Question 40

The large intestine extends from the caecum to the anal canal. Identify the 4 different parts of the colon.

Answer 40

Question 41

Describe three features in the surface anatomy of the colon

Answer 41

- **Omental appendices** are small pouches of peritoneum, filled with fat, on the colon surface - **Teniae coli** are 3 strips of muscle running longitudinally along the surface of the large bowel - **Haustra** are sacculations produced by the contraction of the teniae coli to shorten the wall of the bowel

Question 42

Midgut-derived structures are supplied by the superior mesenteric artery, and hindgut-derived structures by the inferior mesenteric artery. Hence, describe the arterial supply of the ascending colon

Answer 42

Arterial supply via two branches of the superior mesenteric artery; the **ileocolic** and **right colic arteries**

Question 43

Midgut-derived structures are supplied by the superior mesenteric artery, and hindgut-derived structures by the inferior mesenteric artery. Hence, describe the arterial supply of the transverse colon

Answer 43

Arterial supply via branches of the superior mesenteric artery and inferior mesenteric artery: - **Right colic artery** (SMA) - **Middle colic artery** (SMA) - **Left colic artery** (IMA)

Question 44

Midgut-derived structures are supplied by the superior mesenteric artery, and hindgut-derived structures by the inferior mesenteric artery. Hence, describe the arterial supply of the descending colon

Answer 44

Arterial supply a single branch of the inferior mesenteric artery; **the left colic artery**

Question 45

Midgut-derived structures are supplied by the superior mesenteric artery, and hindgut-derived structures by the inferior mesenteric artery. Hence, describe the arterial supply of the sigmoid colon

Answer 45

Arterial supply via branches of the inferior mesenteric artery; the **sigmoid arteries**

Question 46

Describe the formation of the marginal artery

Answer 46

- Terminal vessels of the SMA & IMA split into many vessels as they approach the colon - Vessels anastomose in loops to form a continuous arterial channel along the length of the colon i.e. **the marginal artery**

Question 47

From which blood vessels do the vasa recta arise?

Answer 47

**Vasa recta** arise from the marginal artery to supply the colon

Question 48

Describe the venous drainage of the ascending colon

Answer 48

Venous drainage via **ileocolic** and **right colic veins**, which empty into the superior mesenteric vein

Question 49

Describe the venous drainage of the transverse colon

Answer 49

Venous drainage via **superior mesenteric vein**

Question 50

Describe the venous drainage of the descending colon

Answer 50

Venous drainage via **left colic vein**, which drains into the inferior mesenteric vein

Question 51

Describe the venous drainage of the sigmoid colon

Answer 51

Venous drainage via the **sigmoid veins** which drain into the inferior mesenteric vein

Question 52

Describe 5 gross anatomical differences between the small and large intestines

Answer 52

Question 53

How does the inferior mesenteric artery terminate?

Answer 53

- **Superior rectal artery** is the terminal continuation of the IMA - It crosses the left common iliac artery and descends in the mesentery of the sigmoid colon - It gives rise to branches that supply the rectum