Pericardium and Heart
- Describe the morphology of the pericardium
The pericardium is a fibroserous sac that encloses the heart. It consists of two layers: the fibrous pericardium and the serous pericardium. The fibrous pericardium is a tough, fibrous layer that surrounds the heart. The serous pericardium is a thin, smooth layer that lines the fibrous pericardium and produces pericardial fluid to reduce friction between the heart and the pericardium.
- Describe the external features of the heart
The heart is a muscular organ that is roughly the size of a fist. It is located in the thoracic cavity and is surrounded by the pericardium. The external features of the heart include:
- The base: The base of the heart is the posterior surface that rests on the diaphragm.
- The apex: The apex of the heart is the pointed lower surface that is directed to the left.
- The medial and lateral surfaces: The medial surface of the heart faces the sternum, while the lateral surface faces the lungs.
- The anterior and posterior surfaces: The anterior surface of the heart is the front surface, while the posterior surface is the back surface.
- Describe the internal features of the chambers of the heart
The heart consists of four chambers: the right and left atria, and the right and left ventricles. The internal features of the chambers of the heart include:
- Atria:
- Right atrium: Receives oxygen-depleted blood from the body via the superior and inferior vena cava.
- Left atrium: Receives oxygen-rich blood from the lungs via the pulmonary veins.
- Ventricles:
- Right ventricle: Pumps oxygen-depleted blood to the lungs via the pulmonary artery.
- Left ventricle: Pumps oxygen-rich blood to the body via the aorta.
- Describe the applied anatomy
Applied anatomy refers to the practical application of anatomical knowledge to clinical situations. In the context of the pericardium and heart, applied anatomy includes:
- Cardiac tamponade: A condition where fluid accumulates in the pericardial sac, compressing the heart and impeding its function.
- Pericardial effusion: A condition where fluid accumulates in the pericardial sac, which can be a sign of various cardiac and non-cardiac conditions.
- Cardiac surgery: Anatomical knowledge of the pericardium and heart is essential for cardiac surgeons to perform procedures such as coronary artery bypass grafting and heart transplantation.
Developmental Process
The development of the pericardium and heart involves the following steps:
- Gastrulation → formation of the cardiac mesoderm → formation of the heart tube → looping of the heart tube → formation of the atrial and ventricular chambers → septation of the atrial and ventricular chambers → development of the pericardium
Nerve Supply
The nerve supply to the pericardium and heart includes:
- Sympathetic nervous system: Stimulates the heart and increases heart rate.
- Parasympathetic nervous system: Inhibits the heart and decreases heart rate.
Blood Supply
The blood supply to the pericardium and heart includes:
- Coronary arteries: Supply oxygenated blood to the myocardium.
- Coronary veins: Drain deoxygenated blood from the myocardium.
- Thebesian veins: Drain deoxygenated blood from the myocardium directly into the ventricles.
Lymph Drainage
The lymph drainage from the pericardium and heart includes:
- Lymphatic vessels: Drain lymph from the pericardium and myocardium.
- Lymph nodes: Filter lymph and remove pathogens and waste products.
Muscle Action Sequence
The muscle action sequence of the heart involves the following steps:
- Depolarization of the atrial muscle → contraction of the atria → depolarization of the ventricular muscle → contraction of the ventricles → relaxation of the ventricles → relaxation of the atria
Stepwise Anatomical Mechanism
The stepwise anatomical mechanism of the heart involves the following steps:
- Blood enters the right atrium via the superior and inferior vena cava → blood flows through the tricuspid valve into the right ventricle → blood is pumped through the pulmonary valve into the pulmonary artery → blood is oxygenated in the lungs and returns to the left atrium via the pulmonary veins → blood flows through the mitral valve into the left ventricle → blood is pumped through the aortic valve into the aorta