Circulatory System: Heart Study Notes

Expected Learning Outcomes:
- Define and distinguish between the pulmonary circuit and systemic circuit.
- Describe the general location, size, and shape of the heart.
- Describe the pericardium that encloses the heart.

Cardiology: The study of the heart and its disorders.
Components:
- The cardiovascular system consists of the heart and blood vessels.
- Heart: Acts as a pump to maintain blood flow through the vessels.
- Blood Vessels: Deliver blood to body tissues and return it to the heart.
  - Arteries: Vessels that carry blood away from the heart.
  - Veins: Vessels that carry blood towards the heart.
  - Capillaries: Microscopic vessels connecting smallest arteries and veins.
- The circulatory system is also used to refer to the heart, vessels, and blood.

Two Major Divisions:
1. Pulmonary Circuit:
- Carries blood to the lungs for gas exchange and returns it to the heart (right side of the heart).
1. Systemic Circuit:
- Supplies oxygenated blood to all tissues of the body and returns it to the heart (left side of the heart).
Process of Blood Circulation:
- Right Side of the Heart:
- Receives oxygen-poor blood from body tissues.
- Sends blood to the lungs via the pulmonary trunk → pulmonary arteries → alveolar capillaries (oxygen uptake and carbon dioxide release) → Returns oxygenated blood to the heart via pulmonary veins.
- Left Side of the Heart:
- Receives fully oxygenated blood from the lungs.
- Sends blood to body tissues via the aorta (which branches into smaller arteries).
- Delivers oxygen to tissues and picks up carbon dioxide, returning deoxygenated blood via the superior and inferior vena cava (great vessels).

Location: Found in the mediastinum, the space between the lungs.
Shape:
- Base: The wide, superior portion of the heart where large vessels connect.
- Apex: The tapered inferior end tilted to the left.
Size of the Heart:
- Adult heart approximately weighs 10 ounces, measures 3.5 inches wide at the base, and 5 inches from base to apex.
- Generally, the size is comparable to that of a person's fist.

Diaphragm: Base located superior to this muscle; important for respiratory function.

Function:
- Provides a double-walled sac that allows the heart to beat without friction, provides room to expand, but resists excessive expansion.
- Anchored inferiorly to the diaphragm and anteriorly to the sternum.
Structure:
- Fibrous Pericardium: Outermost layer, tough, fibrous sac.
- Serous Pericardium:
- Two layers:
  - Outer Parietal Layer: Lines the fibrous pericardium.
  - Inner Visceral Layer (Epicardium): Adheres to heart surface and is the outermost layer of the heart itself.
- Pericardial Cavity: The space between the parietal and visceral layers, typically filled with 5 to 30 mL of pericardial fluid.
- Pericarditis: Inflammation of the pericardium, possibly resulting in a friction rub with each heartbeat.

Expected Learning Outcomes:
- Describe the three layers of the heart wall.
- Identify the four chambers of the heart.
- Identify surface features of the heart associated with its internal anatomy.
- Identify the four heart valves.
- Trace the flow of blood through the heart chambers and adjacent blood vessels.
- Describe the arteries nourishing the myocardium and the veins draining it.

Three Layers:
1. Epicardium (Visceral Layer of Serous Pericardium):
- Serous membrane covering the heart; has adipose tissue in thick layers in some areas.
- Coronary blood vessels travel through this layer.
1. Myocardium:
- Composed of cardiac muscle; thickness varies proportional to workload.
- Muscle fibers spiral around the heart, forming a structure known as the