Internal Structure of the Heart

Question 1

Layers

Answer 1

3 layers:
- outer epicardium
- middle mesocardium
- inner endocardium

Question 2

Chambers

Answer 2

• 3 chambered: 2 auricles and 1 ventricle

Question 3

Auricle

Answer 3

• divided into left and right by a longitudinal inter-auricular septum
• right is larger than left

Question 4

Right auricle

Answer 4

• Close to the septum, there is a transverse oval opening called sino-auricular aperture
• Blood enters into the ventricle from sinus venosus through it
• This aperture is guarded by two lip like sinu-auricular valves
• One valve arises from dorsal edge and the other from ventral edge
• These valves allow free flow of blood and prevent the backflow of it.

Question 5

Left auricle

Answer 5

• Slight close to the inter-auricular septum, there is a small opening of the pulmonary vein which has no valves.
• The pressure caused by contraction of auricles serves to close this opening and thus, preventing the back flow of blood into the pulmonary vein.

Question 6

Ventricle Opening

Answer 6

• The 2 auricles open into a single ventricle by a horizontal auriculo-ventricular aperture.
• It is provided with 2 pairs of auriculo-ventricular valves
• One arises from dorsal edge and the other from the ventral edge of this aperture.
• Both valves are provided with fibrous chordae tendiane.
• The chordae tendiane joins the valve to the wall of ventricle in order to prevent backflow of flood into the auricle.

Question 7

Ventricle

Answer 7

• most conspicuous and prominent part of the heart which is triangular in shape
• very thick muscular walls having ridges or columnae carnae
• contain deep pockets between them which prevents the mixing of blood from the two auricles to some extent
• from the right anterior side of the ventricle, a tubular trunk called truncus arteriosus arises whose openings are directed towards the lumen of the truncus

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