29. Heart – position, size, shape and external features. Surface projection on the chest wall. Cardiac atriums and chambers. The valves of the heart.

CARDIOVASCULAR SYSTEM

• The cardiovascular system, also known as circulatory system.
• Is a complex network of organs on vesseles responsible for circulating blood throughout the body.

Parts:

1. Heart: is a muscular organ located in thoracic cavity, between the lungs slightly to the left of the midline.

• Has 4 chambers (2 atrium + 2 ventricles) 4 Valves (2 atrioventricular + 2 semilunar valves)

2. Blood vessels:
3. 2.1 Arteries: carry oxygenated blood (except pulomanary artery).
4. 2.2 Veins: carry deoxygenated " (" " vein)
5. Capillaries: tiny vessels where exchange of oxygen, nutrients and waste products occurs between blood and tissue.

Circulations:

1. Systemic circulation: Oxygenated blood pumped from the left ventricle to the body tissues and returns to the right atrium.
2. Pulmonary Circulation: Deoxygenated blood " " " right ventricle " lungs " left atrium.

COLATERAL CIRCULATION

• Collateral circulation refers to the alternate or accessory network of blood vessels, that can provide a route for blood flow when the primary blood vessels are blocked.
• Some collaterals are pre-existing (Artiogenesis), while others may develop or enlarge in response to chronic ischemia or arteial blockages "new vesseles (Angiogenesis)