[EMB] Development of The Heart

Cardiogenic field

Development of the heart starts in the _________ which is composed of a cluster of horseshoe-shaped cells

infolding of the embryo

Horseshoe-shaped cells form endothelial-lined tubes because of the

heart tube

The tubes eventually fuse at the midline to form the ______ that contains different parts and derivatives

Smooth wall of right atrium, coronary sinus

Part of heart tube and future structure

• Sinus venosus

Left and right auricles

Part of heart tube and future structure

• Primordial atrium

Left ventricle

Part of heart tube and future structure

• Primordial ventricle

Trabeculated part of right ventricle

Part of heart tube and future structure

• Bulbus cordis

Outflow tract of both ventricles

Part of heart tube and future structure

• Conus cordis

Roots and proximal portion of the aorta and pulmonary trunk

Part of heart tube and future structure

• Truncus arteriosus

3rd week of development

Around the __________, the embryo can no longer rely on diffusion of nutrients alone

Primary Heart Field

Coincides with the formation of the notochord (Day 16-18)

visceral layer of lateral plate mesoderm

These cells of primary heart field are horseshoe-shaped and are located in the visceral layer of lateral plate mesoderm

CRANIAL

Initially, the cardiogenic field is established ______ to the developing brain

thoracic area

Due to infolding of embryo, cardiogenic field will later on be located in the

cardiac myoblast and blood islands

Once the primary heart field is established, the progenitor cells are induced by pharyngeal endoderm to form that surround the endothelial-lined tube

Cardiac myoblast:

forms the myocardium

Blood islands

form blood cells and vessels by virtue of vasculogenesis

atria and LEFT ventricle

The primary heart field forms the

visceral mesoderm

Secondary heart field lies on

arterial and venous poles of the heart

Secondary heart cells are responsible for lengthening the

RIGHT ventricle, conus cordis, and truncus arteriosus

The secondary heart field forms the

serotonin

The key substance in the development of laterality is

Dextrocardia

• Apex is directed to the RIGHT, the aorta is on the RIGHT while the vena cavae are on the LEFT

• Associated with other congenital defects

Double Outlet Right Ventricle

• Incomplete closure of the ventricle

• Aorta is placed to the RIGHT of the midline, and hence, it also drains the right ventricle aside from the left ventricle

Transposition of the Great Arteries

• Aorta drains the RIGHT ventricle whereas the pulmonary artery

  drains the LEFT ventricle

• Normally, it should be the OTHER WAY AROUND

anterior to neural plate → thoracic cavity → pericardial cavity → final loc

Formation of heart tube sequence

endocardial tube

Simultaneous lateral folding of the embryo will bring together the __________ forming a single tube

myocardial mantle

Endocardial heart tube is initially surrounded by ________, which becomes the myocardium

dorsal mesocardium

Initially, the heart tube remains connected to the dorsal side of the pericardial cavity via the ________ which is derived from the secondary heart field

pulmonary veins

The dorsal mesocardium will be incorporated into the posterior part of the heart to become the pulmonary veins

Endocardium

This layer is formed by endothelial lining of the heart tube

Myocardium

This layer is formed by:

• Myoblasts

• Myocardium thickens and secretes a layer of extracellular matrix rich in hyaluronic acid called cardiac jelly which separates it from the endothelial lining

This layer is formed by:

• Mesenchymal cells coming from the caudal part of the dorsal mesocardium

• Brings about the formation of the coronary arteries and endothelial lining and smooth muscles of the arteries of the heart