Evolution of the Heart and Development of Heart

By Deepash and Sultan

The heart pumps blood around the body

The heart humans have has come about after millions of years of evolution

We will talk briefly about how the heart as evolved

The Heart

Circulation system acts to transport oxygen to cells

Generalization about circulation in the different phyla and stages of evolution of the heart are possible

We will follow development from fish to mammals

Hearts of Vertebrates

Simplest vertebrate heart

Two chambers; one atrium and one ventricle

Blood is oxygenated and the passed around body

Single circulation

Fish Heart - Structure

System provides sufficient oxygen and nutrients to cells

Fish Heart - Function

Amphibian Heart - Structure

Double circulation

Made of left and right atria and single ventricle

Oxygenated and deoxygenated blood kept separate

Amphibian Heart - Function

More efficient that fish heart

Oxygen and nutrients pumped to cell more quickly

Allows for a higher metabolic rate than fish

Structurally similar to amphibian heart

Difference is that the ventricles are partially divided

Number of chambers can be disputed

Reptile Heart – Structure

System minimises the mixture of atrial and venous blood, though doesn’t stop mixing

Atrial blood is not saturated with oxygen

More efficient that amphibian heart

Reptile Heart – Function

Double circulation

Four chambers; two atria and two ventricles

Septum prevents mixing

In one heart beat, blood goes to lungs and body

Bird and Mammalian Heart - Structure

Atrial blood is saturated with oxygen

Oxygen and nutrients passed to cell quickly

Very high metabolic rate

Most efficient system of circulation

Bird and Mammalian Heart - Function

At around day 21 , the heart is a tubular structure formed from the fusion of two endothelial tubes which originated from the cardiogenic mesoderm region.

Development of the Heart

After the four chambers start to appear the heart starts bending into an ‘S’ shape . The heart starts pumping at this stage / (ineffective)

Occurs at about day 23 .

Looping of the Heart

Looping of the heart The bulbus cordis

moves inferiorly , anteriorly and to the right.

Ventricle moves to the left.

Atrium and sinus venosus moves superiorly and posteriorly.

During month 2 , the heart divides into its four chambers by the formation of the septum and valves, made from endocardial cushions , conus cushion and muscular septum.

Development of the heart -2

Septum primium grows from Endocardial cushion at day 28.

Septum secundum forms , but doesnt fuse with primum until after birth

Atrial Partitioning

Both ventricles grow and expand rapidly during week 7/8.

the walls of each ventricle grow opposing to each other giving rise to the muscular septum

Ventricular Septation

ontogeny recapitulates phylogeny

http://www.bbc.co.uk/news/health-12573922

The End