Development of Heart Flashcards
First developmental system and organ
- First working unit in the developing embryo was circulatory system
- First functional organ was the heart
Why is the cardiovascular system the first to develop?
Embryo is growing and this process needs nutrients, oxygen, and removal or CO2 and metabolites
Circulatory system components
- Heart
- Arteries
- Veins
- Blood
Initial steps of cardiogenic field development
- Vertebrate heart arises from two areas of splanchnic or visceral mesoderm
- The progenitor cells in two small patches on either side of the epiblast enter the primitive streak
- Cells migrate in and then towards outer edge forming part of the new lateral plate mesoderm and therefore the heart field
**Migration results in the start of the specification of the heart field - The cells in the field are multipotent cardiac progenitor cells which separate into two regions on each side of the field
Region 1: will become the scaffold of heart tube and eventually the left ventricle of adult
Region 2: will add to both ends of heart tube and become right ventricle and inflow region of pulmonary vein and vena cava
Where do heart cell types come from?
All cell types of heart form from the two regions of the cardiogenic fields
What contributes to the septa that separates the aorta from the pulmonary tract?
The neural crest
Formation of the pericardial cavity
- Cardiogenic field is bent with embryonic folding. At the same time there is cell differentiation occurring independently on both the right and left sides of the embryo forming a horse-shoe shaped cardiac tube
- Folding results in in heart within pericardial cavity ventral to embryonic disc
What does the Horse-shoe shaped cardiac tube become?
Anterior extensions of horseshoe become 2 ventral aortae
- Posterior parts of the extension join with developing venous system
Dorsal parts of horseshoe become dorsal aortae
Lateral body folding then starts to bring the two developing tubes together in the midline of the embryo to eventually form primitive heart
Components formed by Differentiation of segmented tube
- Sinus venosus- all veins meet here
- Atrium
- Ventricle
- Bulbis cordis
- Truncus arteriosus- all arteries meet here
Outgrowing the pericardial cavity
- Growth of these indentations and dilatations leads to the heart tube trying to outgrow the pericardial cavity
- The sinus venosus and atrium are first not enclosed by pericardial cavity but with growth and bending they become enveloped (within 23 days of gestation)
Beating of heart tube
Set by pacemakers in the sinus venosus (at this time in early development)
Development of four chambered heart
Partitions form in the primitive heart to convert the pulsating heart tube into a 4 chambered organ
Formation of atrio-ventricular canal
- Septum intermedium- formed by mesenchymal endocardial cushions between endocardium and myocardium that move towards each other and fuse
- Creates left and right atrio-ventricular openings
Formation of left and right atrium
- Septum primum will arise from the dorsal wall of the common foetal atrium and move towards the endocardial cushions. A transitory foramen primum (present for access until foramen secundum is complete) is created and through apoptosis, a foramen secundum is created.
- A second membrane, the septum secundum develops from dorsal wall of right atrium
- There is an opening that remains between the free edge of the septum secundum and foramen secundum known as foramen ovale - Upper part of septum primum fuses with septum secundum while the rest becomes valve-like for foramen ovale. The bottom of the septum secundum fuses with septum intermedium.
Purpose of fusion of septum secundum and septum intermedium
Divides the blood flow returning to the heart from caudal vena cava into two streams