Wk 2 - Anatomy: The Liver Flashcards
Where is the liver (usually) located?
- Usually located in right hypochondrium, epigastrium and left hypochondrium (not all go into left)
- Mostly protected by ribs
- Attached to inferior surface of diaphragm
Describe the movement of the liver during ventilation.
- Usually situated between 5th and 10th intercostal space at normal respiratory position
- Because of its reflections ie peritoneum - the liver moves during respiration
- Full expiration - can go up to 4th intercostal space, above nipple in males
Explain the surfaces of the liver.
Liver has two main surfaces
- Diaphragmatic surface: the anterosuperior surface of the liver.
- Smooth and convex, fitting snugly beneath the curvature of the diaphragm.
- Posterior aspect of the diaphragmatic surface is not covered by visceral peritoneum, and is in direct contact with the diaphragm itself (known as the ‘bare area’ of the liver).
- Visceral surface: the posteroinferior surface of the liver.
- With the exception of the fossa of the gallbladder and porta hepatis, it is covered with peritoneum.
- Moulded by the shape of the surrounding organs, making it irregular and flat.
- Lies in contact with the right kidney, right adrenal gland, right colic flexure, transverse colon, first part of the duodenum, gallbladder, oesophagus and the stomach.
What are the two main lobes?
- Right lobe
- Left lobe
There are two further (smaller) lobes in the liver. What are they?
- Caudate lobe (meaning tail-like here)
- Quadrate lobe (this is the more inferior one)
Describe the key anatomical relations of the liver.
- Superior: diaphragm
- Anterior: ribs 7-11 (varies), anterior abdominal wall
- Posteroinferior: oesophagus, right kidney, right adrenal gland, right colic flexure, lesser omentum, duodenum, gallbladder, stomach
What is the lesser omentum?
- A double layer of visceral peritoneum, and is considerably smaller than the greater
- Attaches from the lesser curvature of the stomach and the proximal part of the duodenum to the liver
- It consists of two parts:
- Hepatogastric ligament (the flat, broad sheet)
- Hepatoduodenal ligament (the free edge, containing the portal triad).
The ________, or _______, appears as an outgrowth of _______ between the layers of ________ (by 3rd week).
The hepatic diverticulum, or liver bud, appears as an outgrowth of distal foregut between the layers of ventral mesentery (3rd week).
Connection between _______ and _______ narrows to form ______; ventral outgrowth of ________ gives rise to ______ and _______.
Connection between liver bud and duodenum narrows to form bile duct; ventral outgrowth of bile duct gives rise to gallbladder and cystic duct.
List the peritoneal ligaments of the liver and their attachments.
- Falciform ligament attaches liver to diaphragm and anterior abdominal wall
- Lesser omentum attaches liver to stomach and duodenum
- Bare area = no peritoneum and therefore liver in direct contact with diaphragm
What is the ‘bare area’ of the liver?
- Area not covered by visceral peritoneum.
- Where liver is in contact with the diaphragm.
- Lies between the anterior and posterior folds of the coronary ligament.
What is the ‘porta hepatis’?
The porta hepatis is the central intraperitoneal fissure of the liver that separates the caudate and the quadrate lobes. It is the entrance and the exit for several important vessels including the portal vein, the hepatic artery, the hepatic nervous plexus, the hepatic ducts and the lymphatic vessels.
The ________ of the ________ encloses structures passing to/from the porta hepatis.
The free margin of the lesser omentum encloses structures passing to/from the porta hepatis.
What is the portal triad?
- Bile duct
- Hepatic artery proper (smallest lumen of the three)
- Portal vein (has much larger lumen)
What is the umbilical vein and the ductus venosus?
They are embryological features of the liver.
What is the function of the umbilical vein?
It carries nutrient and oxygen-rich blood from the placenta to the fetus
What is the function of the ductus venosus?
It shunts blood from the umbilical vein to the IVC.
What happens to the umbilical vein and the ductus venosus after birth?
The umbilical vessels regress after birth to become remanents on the liver (ligamentum venosum - ductus venosum and round ligament - umbilical vein)
What is the fibrous remanent of the umbilical vein called?
Round ligament
What is the fibrous remanent of the ductus venosus called?
Ligamentum venosum
What is the anatomical division of the lobes?
Right and left lobes
What is the functional division of the liver?
- Divided into sectors and segments
- Functional lobes
- Left lobe: left lateral and left medial sectors
- Right lobe: right lateral and right medial sectors
- Hepatic segments
- Eight segments (I-VIII), with the fourth one being divided into (a) and (b) parts (IVa, IVb)
On what basis is the liver divided into its functional unit?
By its blood supply and biliary drainage
What are the landmarks that divide the liver into functional lobes and segments?
Line through the midline of the gallbladder and inferior vena cava
What landmark divides the liver into its anatomical lobes?
The falciform ligament and ligament teres
Describe the blood supply of the liver.
- The liver receives arterial blood from the coeliac trunk via the hepatic arteries - common hepatic artery and hepatic artery proper (20%)
- All venous blood from the gut drains to the liver via the hepatic portal vein (80%)
Does the liver receive most of its blood supply from arteries or veins?
Veins (hepatic portal vein) nb the vein has 40% more O2 compared to IVC
Describe the blood supply to the 8 different segments of the liver.
Each segment is:
- Supplied by a tertiary branch of the hepatic artery proper and hepatic portal vein
- Drained by a tertiary tributary of the common hepatic duct (conveying bile)
Where do hepatic veins drain into?
The IVC
Describe the lymphatic drainage of the liver (anterior and posterior aspects have different drainage).
- The lymphatic vessels of the anterior aspect of the liver drain into hepatic lymph nodes. These lie along the hepatic vessels and ducts in the lesser omentum, and empty in the colic lymph nodes which in turn, drain into the cisterna chyli, then drains into the thoracic duct.
- Lymphatics from the posterior aspect of the liver drain into phrenic and posterior mediastinal nodes, and then drain to either the right lymphatic or the thoracic duct.
- The liver is a huge lymph producing organ!
- V important re cancer and metasteses.
What is the structural unit of the liver?
The hepatic lobule
What lies at the angles of the lobule?
The hepatic artery, portal vein and bile duct
Blood flows between plates of hepatocytes along ______ to _____.
Blood flows between plates of hepatocytes along sinusoids to central vein.
Label the following image:
- Hepatocyte
- Hepatic stellate cell
- Kupffer cell
- Sinusoid
- Endothelial cell
- Space of disse
What is the function of hepatic stellate cells?
Stores vitamin A and major player in fibrosis
What are Kupffer cells?
‘In-house’ macrophages of the hepatocyte
What zone is most affected when a patient is in ischaemic condition?
Zone III of the liver
What is the main function of zone III?
Drug metabolism
Describe the relationship of the hepatocyte’s different zones to the central vein.
What is the difference between portal system and systemic venous system?
- They are two venous systems that drain abdominal structures.
- The portal system transports venous blood to the liver for processing.
- The systemic venous system returns blood to the right atrium of the heart.
What is a porto-systemic anastomosis?
A porto-systemic anastomosis is a connection between the veins of the portal venous system, and the veins of the systemic venous system.
What are the major sites of porto-systemic anastomosis?
The major sites of these anastomoses include:
- Oesophageal – Between the oesophageal branch of the left gastric vein and the oesophageal tributaries to the azygous system.
- Rectal – Between the superior rectal vein and the inferior rectal veins.
- Retroperitoneal – Between the portal tributaries of the mesenteric veins and the retroperitoneal veins.
- Paraumbilical – Between the portal veins of the liver and the veins of the anterior abdominal wall.
What happens if the portal circulation is obstructed?
If portal circulation through liver is obstructed, these collateral routes 9i.e porto-systemic anastomoses) can deliver blood back to the heart.
What could cause portal system obstruction?
Due to cirrhosis, portal vein thrombosis, or external pressure from a tumour
What does the obstruction of the portal system lead to?
Portal hypertension (which will open up the anastomoses that are usually closed off)
What could portal hypertension lead to?
- Oesophageal varices*** very dangerous, as when they rupture they lead to severe haemorrhage
- Caput medusae and ascites (ie excessive peritoneal fluid in peritoneal cavity)
- Anorectal varices
- Splenomegaly
