Liver Anatomy, Sonography, and Function Review

Comprehensive practice flashcards covering liver anatomy, sonographic landmarks, Couinaud segmentation, vascular structures, and clinical liver function concepts from Chapter 1 to Chapter 9.

Why is the liver classified as the largest gland in the human body?

Because it performs a wide variety of metabolic functions and major secretion features.

What anatomical structure serves as the outer margin of the liver during ultrasound scanning?

The diaphragm.

What is Riedel's lobe?

An anatomical variation where an extra piece of the right liver lobe extends inferiorly down toward the hip bone, commonly seen in tall, thin individuals.

What is a beaver tail liver?

An anatomical variation where part of the left lobe extends fully across the upper abdomen and wraps around the spleen.

What are the standard approximate dimensions of the liver in sagittal and transverse planes?

Sagittal dimension is $13\text{ to }17.5\,cm$ and transverse is $21\text{ to }22.5\,cm$, with $15\,cm$ generally used as the standard cutoff for upper normal size.

What is the normal sonographic texture and echogenicity of healthy liver parenchyma?

Homogenous with a mid-level gray shade evenly distributed from top to bottom.

How does the relative size of the right lobe compare to the left lobe in adults versus infants?

In adults, the right lobe exceeds the left lobe in size by a ratio of $6:1$, whereas in infants, the left lobe is initially the largest.

Which region of the liver is called the bare area and why?

The bare area is the superior and posterior surface around the IVC that is not covered by the peritoneal membrane.

What three major anatomical fossas are located on the liver?

The porta hepatis fossa, the gallbladder fossa, and the IVC fossa.

Where is the caudate lobe situated relative to the left lobe of the liver?

On the posterior and superior surface of the left lobe.

What anatomical landmark separates the caudate lobe from the left lobe?

The ligamentum venosum.

What is the current classification of the former quadrate lobe in modern hepatic anatomy?

It is no longer considered a separate lobe and is classified as part of the medial segment of the left lobe.

Why is the caudate lobe frequently spared from systemic liver diseases like cirrhosis or hepatitis?

Because it possesses its own separate venous drainage system and distinct blood supply.

How do hepatic veins and portal veins course relative to one another inside the liver?

Hepatic veins course longitudinally through the body, while portal veins course transversely.

According to Couinaud's segmental anatomy, how many functional segments exist in the liver?

Eight functional segments, each with its own vascular feeder vessels and biliary system.

Which Couinaud segment number is assigned to the caudate lobe?

Segment 1.

Which Couinaud segments comprise the left lateral and left medial lobes?

Segments 2 (superior) and 3 (inferior) comprise the left lateral lobe; Segments 4a (superior) and 4b (inferior) comprise the left medial lobe.

Which Couinaud segments comprise the right lobe of the liver?

Segments 5 (anterior inferior), 6 (posterior inferior), 7 (posterior superior), and 8 (anterior superior).

What sonographic structure connects the neck of the gallbladder to the main portal vein?

The main lobar fissure (MLF).

What structure is wrapped inside the falciform ligament?

The ligamentum teres, which is the obliterated remnant of the fetal umbilical vein.

What fetal structure gives rise to the ligamentum venosum?

The ductus venosus.

Which vessels join behind the neck of the pancreas to form the main portal vein?

The splenic vein and the superior mesenteric vein (SMV).

What are the two primary branches of the right portal vein?

The anterior right portal vein and the posterior right portal vein.

What are the two primary branches of the left portal vein?

The medial left portal vein and the lateral left portal vein.

How can portal veins be distinguished from hepatic veins on ultrasound?

Portal veins have echogenic, bright walls due to a thick collagenous sheath and decrease in caliber away from the hilum; hepatic veins lack bright walls (unless imaged at a $90^\circ$ angle) and enlarge as they approach the IVC.

Which three structures form the portal triad (Mickey Mouse sign) at the porta hepatis?

The main portal vein (head), the common bile duct (right ear), and the hepatic artery (left ear).

In the Mickey Mouse view of the porta hepatis, which structure represents the right ear?

The common bile duct (CBD).

What are the respective physiological roles of the portal vein, hepatic artery, and hepatic veins?

The portal vein carries nutrient-rich blood from the intestines to the liver, the hepatic artery supplies oxygenated blood, and the hepatic veins drain deoxygenated blood and waste into the IVC.

How does color Doppler help differentiate the common bile duct from adjacent hepatic vessels?

The common bile duct shows no color Doppler flow because bile velocity is too low, whereas the hepatic artery and portal vein display active blood flow signals.

How do hepatocellular liver diseases differ from obstructive liver diseases in management?

Hepatocellular disease involves direct hepatocyte damage and is managed medically, whereas obstructive disease involves blockage of bile ducts or mass lesions and requires surgical management.

Which three primary enzymes are evaluated in liver function tests (LFTs)?

Aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (Alk Phos).

How does end-stage liver failure lead to elevated ammonia levels and hepatic encephalopathy?

Damaged hepatocytes cannot convert toxic ammonia (derived from protein/nitrogen breakdown) into urea, causing ammonia to accumulate in the bloodstream and cross into the brain.

What happens to Blood Urea Nitrogen (BUN) levels in acute or chronic liver failure?

BUN levels drop significantly because the failing liver cannot convert ammonia into urea.