liver morphogenesis

Definition

Target type: biologicalprocess

The process in which the anatomical structures of the liver are generated and organized. [GOC:mah]

Liver morphogenesis is a complex and highly regulated process that begins during early embryonic development and continues throughout postnatal life. It involves the coordinated interaction of multiple cell types, signaling pathways, and transcription factors to generate a functional liver organ.

**Early Embryonic Development:**

* **Specification of the Liver Bud:** The liver arises from the ventral foregut endoderm, specifically from the hepatic diverticulum. This process is initiated by inductive signals from the adjacent cardiac mesoderm.
* **Formation of the Liver Bud:** The hepatic diverticulum proliferates and expands, forming the liver bud.
* **Hepatoblast Formation:** Within the liver bud, multipotent progenitor cells called hepatoblasts arise. Hepatoblasts have the potential to differentiate into both hepatocytes (liver parenchymal cells) and cholangiocytes (bile duct cells).
* **Vascularization:** Blood vessels invade the liver bud, establishing the circulatory system.

**Hepatocyte Differentiation:**

* **Hepatoblast Maturation:** Hepatoblasts undergo a series of differentiation steps to become mature hepatocytes. This includes the acquisition of liver-specific functions, such as protein synthesis, detoxification, and bile production.
* **Cholangiocyte Differentiation:** A subset of hepatoblasts differentiates into cholangiocytes, which form the biliary tree and transport bile.
* **Formation of the Hepatic Sinusoids:** The space between hepatocytes and sinusoidal endothelial cells is established, allowing for efficient exchange of nutrients and waste products.

**Postnatal Development:**

* **Liver Growth and Maturation:** The liver continues to grow and mature after birth. This involves an increase in hepatocyte number and size, as well as the development of specialized liver functions.
* **Liver Regeneration:** The liver has a remarkable regenerative capacity. In response to injury or partial resection, hepatocytes can re-enter the cell cycle and proliferate, restoring liver mass.
* **Aging and Liver Function:** Liver function declines with age, due to factors such as oxidative stress and cellular senescence.

**Regulation of Liver Morphogenesis:**

* **Signaling Pathways:** Several signaling pathways play crucial roles in liver development, including fibroblast growth factor (FGF), Wnt, Hedgehog, and transforming growth factor beta (TGF-beta) pathways.
* **Transcription Factors:** Transcription factors, such as HNF4α, HNF1α, and FOXA2, regulate the expression of genes involved in liver development and function.
* **Extracellular Matrix:** The extracellular matrix provides structural support and influences cell signaling during liver development.

**Disorders of Liver Morphogenesis:**

* **Congenital Liver Disease:** Defects in liver development can lead to various congenital liver diseases, such as biliary atresia, Alagille syndrome, and polycystic liver disease.
* **Hepatocellular Carcinoma:** Liver cancer, including hepatocellular carcinoma, can arise from mutations in genes involved in liver development and function.'
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