Heart Histology

Question 1

What are the three layers of the heart?

Answer 1

Layers from within outwards:

• Endocardium
• Myocardium
• Epicardium

Question 2

Describe the endocardium layer

Answer 2

The surface consists of polygonal endothelial cells in the basement membrane and are supported by subendothelial coat of fine collage and elastic fibres. This then merges with the deeper subendothelial coat which attaches the endocardium to the myocardium. It mainly consists of loose connective tissue, blood vessels and Purkinge fibres

Question 3

Describe the myocardium layer

Answer 3

It is composed of cardiac muscle with supporting connective tissue, nerves and blood vessels. The cardiac muscle consists of striated myocardial cells, which are breached and anatomising. The cardiac nuclei are centrally located and are surrounded by pale staining cytoplasmic region called the perinuclear halo where most organelles are situated. There is a connective tissue sheath called the endomysium which surrounds each muscle fibre and is thickened at points of attachment to valves or fibrous skeleton. It is electrically coupled at intercalated discs which are important for rhythmic contractibility of the myocardium.

Question 4

Describe the epicardium layer

Answer 4

It has a serous membrane which forms the visceral pericardium. It consists of a layer of loose connective tissue covered by mesothelial lining. It is also often rich in adipose tissue.