How many lobes does a rat's liver have? - briefly
A rat’s liver is divided into four distinct lobes. These are typically identified as the left lateral, median, right, and caudate lobes.
How many lobes does a rat's liver have? - in detail
The liver of the common laboratory rat (Rattus norvegicus) is organized into four principal lobes. These are the left lateral lobe, the median (or central) lobe, the right lobe, and the caudate lobe. Occasionally a small accessory lobe, the papillary process, is observed extending from the caudate region, but it is not considered a separate major lobe in most anatomical descriptions.
- Left lateral lobe – situated on the animal’s left side, it occupies the majority of the ventral surface and receives blood from the left hepatic artery and portal vein branch.
- Median lobe – located centrally, it connects the left and right lobes and is supplied by branches of both hepatic arteries.
- Right lobe – forms the rightmost portion of the organ, receiving its own vascular branches and draining into the right hepatic vein.
- Caudate lobe – positioned posteriorly near the diaphragm, it includes the papillary process in some specimens and is fed by the caudate branch of the portal vein.
Key anatomical details:
- The total liver mass in an adult rat typically ranges from 10 to 15 g, representing about 3–4 % of body weight.
- Each lobe possesses an independent portal triad (portal vein, hepatic artery, bile duct) that allows separate functional assessment in experimental studies.
- The lobes are demarcated by connective tissue septa; however, the boundaries are not as rigid as in larger mammals, permitting some inter‑lobe communication.
- Histologically, all lobes share the classic hepatic architecture of hepatocyte plates radiating from central veins, but the caudate lobe often shows a higher concentration of bile ducts.
Comparative notes:
- In mice, the liver is similarly divided but may display a fifth, the quadrate lobe, which is rarely distinguished in rats.
- Larger rodents, such as guinea pigs, possess a more complex lobation pattern, including distinct left, right, median, and caudate lobes plus accessory lobes.
The four‑lobe configuration is a standard reference point for surgical manipulation, toxicology testing, and physiological measurements in rat models.