Heart Anatomy and Functionality Quiz

Study Notes

The human heart has four chambers.
Other mammals, birds, reptiles, amphibians, and fishes have different numbers of chambers.
Human heart has two atria (right atrium, left atrium) and two ventricles (right ventricle, left ventricle).
The right-side of the heart is considered weaker than the left-side.

The heart's two pumps work in unison and are synchronized.
The heart has four one-way valves to prevent backflow of blood as the heart fills and empties.

Tricuspid valve is between the right atrium and right ventricle.
Bicuspid valve is located between the left atrium and left ventricle.
These two valves are collectively known as atrioventricular valves (AV valves).
Pulmonary valve is at the boundary between the right ventricle and the pulmonary trunk.

Blood flow through AV valves: 70% is passive, the final 30% is pushed by the atrial wall contraction.

Heart valves are passive structures, meaning they open and close based on blood pressure differences.
Their primary function is to prevent the backflow of blood.
Approximately 70% of blood flow occurs during diastole (heart relaxation).
Semilunar valves are a type of heart valve with three cusps.

The heart wall consists of three distinct layers: the epicardium, myocardium, and endocardium.
Epicardium (Outer Layer): Also known as the visceral pericardium, it's composed of mesothelial cells and connective tissue.
Myocardium (Middle Layer): The thickest layer, made up of cardiac muscle responsible for heart contractions.
Endocardium (Inner Layer): Composed of squamous epithelial cells, it lines the heart's chambers and blood vessels.

The cardiac cycle refers to the rhythmic sequence of heart contractions and relaxations, divided into three phases:
- Atrial Diastole: Relaxation of the atrial muscle fibers.
- Atrial Systole: Contraction of the atrial myocardium, pushing blood into the ventricles.
- Ventricular Systole: Contraction of the ventricular myocardium, ejecting blood into the aorta and pulmonary artery.

A syncytium is a group of cells that function as a single unit, exhibiting coordinated behavior.
In the heart, there are two distinct syncytia:
- Atrial syncytium: Coordinated contraction of the atrial muscle.
- Ventricular syncytium: Coordinated contraction of the ventricular muscle.

The cardiac conduction system is a specialized network of nodes and fibers, modifying heart muscle cells.
It regulates heartbeat and ensures the coordinated function of the atrial and ventricular syncytia.
Key components of the conduction system include:
- SA Node (Sinoatrial Node): Primary pacemaker of the heart, initiating the electrical impulse.
- AV Node (Atrioventricular Node): Delays the impulse to allow ventricular filling.
- Purkinje Fibers: Rapidly transmit the impulse throughout the ventricles, initiating contraction.

The heart possesses inherent rhythmicity, meaning it can beat independently of the nervous system.
While autonomous, heart rhythm is still regulated by the autonomic nervous system (ANS).