The Circulatory System Section 33.1

Functions of the Circulatory System Needed because the body has millions of cells. Transports nutrients, oxygen, wastes, other substances.

The Heart: Structure The heart consists of – 4 chambers – Numerous valves – A muscle (cardiac) – Hollow – Septum separates right from left. In the walls of the heart, 2 thin layers of connective and epithelial tissue sandwich a muscle called the myocardium. Myocardium contracts and pumps blood through circulatory system.

The Heart: Structure Diagram

The Heart: Blood Flow Superior/Inferior Vena Cava Right Atrium Tricuspid Valve Right Ventricle Pulmonary Valve Pulmonary Artery Lungs Pulmonary Veins Left Atrium Mitral Valve Left Ventricle Aortic Valve Aorta

The Heart: Blood Supply Coronary Arteries give blood to heart’s tissue. – Branch from aorta – Run through heart tissue – Narrow – If blocked, tissue may die=heart attack.

The Heart: Circulation Pulmonary – Right side of heart pumps to lungs. – Gas exchange occurs – Oxygen rich blood returns to left side of heart. Systemic – Blood pumped from left side of heart to body. – Cells use oxygen – Oxygen poor blood comes back to right side of heart.

The Heart: Heartbeat 1. Atria Contract – Starts in right atrium – In a small muscle group, sinoatrial node (SA). AKA pacemaker. – When SA node fires, electrical impulse spreads and muscle contracts. 2. Ventricles Contract – Impulse from SA picked up by atrioventricular (AV) node. – Impulse delayed. – AV node produces impulses that spread through ventricles. – They contract.

The Heart: Heart Rate Varies depending on.. – Activity level – Oxygen need Not directly controlled by nervous system. – Is influenced though

Blood Vessels: Arteries Oxygen rich blood to the tissues of the body and usually flow with gravity Large (superhighways) Thick walled…highly pressurized Consist of connective tissue, smooth muscle, endothelium.

Blood Vessels: Capillaries Smallest vessels Narrow, blood cells move single file Thin walls

Blood Vessels: Veins Blood flows against gravity Large veins near skeletal muscles, push blood towards heart. Veins contain valves Consist of connective tissue, smooth muscle, endothelium.

Blood Pressure System always under pressure due to arterial walls. Pressure needed to make blood flow. Blood pressure regulated by the nervous system, also kidneys.