atrioventricular node development

Definition

Target type: biologicalprocess

The process whose specific outcome is the progression of the atrioventricular (AV) node over time, from its formation to the mature structure. The AV node is part of the cardiac conduction system that controls the timing of ventricle contraction by receiving electrical signals from the sinoatrial (SA) node and relaying them to the His-Purkinje system. [GOC:mtg_heart]

The atrioventricular (AV) node is a crucial component of the heart's electrical conduction system, ensuring synchronized contraction of the atria and ventricles. Its development is a complex process involving coordinated interactions between various cell types, signaling pathways, and transcription factors.

**1. Specification of AV Node Progenitors:**

* During early heart development, the first heart field forms the primitive heart tube, a simple structure with a single chamber.
* Within this tube, a region called the second heart field (SHF) emerges, contributing to the formation of the AV canal, the precursor to the AV node.
* SHF cells express specific transcription factors, including Tbx2, Tbx3, and Nkx2.5, which are essential for their specification as AV node progenitors.

**2. Differentiation and Maturation:**

* AV node progenitors undergo differentiation, acquiring specialized characteristics and properties that define the AV node's function.
* This process involves downregulation of genes associated with contractile function and upregulation of genes involved in electrical conduction.
* Key transcription factors involved in this process include Shox2, Gata4, and Pitx2.
* The AV node also develops unique features, including a slower conduction velocity and a smaller size compared to other cardiac cells, contributing to its role in delaying electrical signals.

**3. Electrical Conduction Properties:**

* The AV node develops specialized ion channels that regulate the flow of ions across cell membranes, contributing to its electrical properties.
* These channels, including HCN channels, L-type calcium channels, and potassium channels, ensure a controlled and delayed transmission of electrical impulses.

**4. Interactions with Surrounding Tissues:**

* The development of the AV node is influenced by interactions with surrounding tissues, including the atria and ventricles.
* Signaling molecules, such as fibroblast growth factors (FGFs) and Wnt proteins, play a role in guiding the formation and proper placement of the AV node.

**5. Morphological Features:**

* The AV node is a small, compact structure located at the junction between the atria and ventricles.
* It consists of specialized cells, including nodal cells and transitional cells, arranged in a network that facilitates electrical conduction.
* The AV node has a characteristic morphology, with a dense network of capillaries and a unique arrangement of cells, which contribute to its function.'
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