Topic 8) Transport in mammals

Circulatory Systems Overview

• Mammals possess a closed double circulatory system.

• Blood circulates through the heart twice during each complete circuit:

  • Pulmonary circulation: Transports deoxygenated blood from the heart to the lungs for gas exchange.

  • Systemic circulation: Delivers oxygenated blood from the heart to the rest of the body.

Major Blood Vessels

• Pulmonary Artery: Carries deoxygenated blood from the right ventricle to the lungs.

• Pulmonary Vein: Transports oxygenated blood from the lungs to the left atrium.

• Aorta: Distributes oxygenated blood from the left ventricle to the body.

• Vena Cava: Returns deoxygenated blood from the body to the right atrium

Blood Vessels and Their Functions

• Arteries: Carry blood away from the heart under high pressure.

• Arterioles: Smaller branches of arteries leading to capillaries.

• Capillaries: Microscopic vessels where exchange of gases, nutrients, and wastes occurs.

• Venules: Small vessels that collect blood from capillaries.

• Veins: Return blood to the heart under low pressure; contain valves to prevent backflow.

Tissue Fluid and Lymph

• Tissue fluid surrounds cells, providing a medium for exchange.

• Formed from blood plasma that leaks out of capillaries.

• Excess tissue fluid is collected by the lymphatic system and returned to the bloodstream.

Heart Structure

• A muscular organ located in the thoracic cavity.

• Divided into four chambers:

  • Right Atrium: Receives deoxygenated blood from the body.

  • Left Atrium: Receives oxygenated blood from the lungs.

  • Right Ventricle: Pumps deoxygenated blood to the lungs.

  • Left Ventricle: Pumps oxygenated blood to the body.

Valves of the Heart

• Atrioventricular Valves:

  • Tricuspid Valve: Between the right atrium and ventricle.

  • Bicuspid (Mitral) Valve: Between the left atrium and ventricle.

• Semilunar Valves:

  • Pulmonary Valve: At the base of the pulmonary artery.

  • Aortic Valve: At the base of the aorta.

• Valves ensure unidirectional blood flow and prevent backflow.

Cardiac Muscle

• Specialized muscle tissue capable of continuous contraction.

• Composed of myocytes connected by intercalated discs, allowing synchronized contraction.

Cardiac Cycle

• Systole: Contraction phase where blood is pumped out of the heart.

• Diastole: Relaxation phase where the heart chambers fill with blood.

• The cycle ensures efficient blood flow through the heart and to the lungs and body.

Electrical Conduction System

• Sinoatrial (SA) Node: Pacemaker initiating the heartbeat.

• Atrioventricular (AV) Node: Delays impulse before it passes to the ventricles.

• Bundle of His: Conducts impulses to the ventricles.

• Purkinje Fibers: Distribute impulses throughout the ventricles.

Coronary Circulation

• The heart muscle itself is supplied with blood by the coronary arteries.

• Blockage in these arteries can lead to myocardial infarction (heart attack).