Transport in Animals: Circulatory Systems

Transport in Animals

• Circulatory System: A system of blood vessels, a pump (heart), and valves that ensures one-way blood flow.
• Fish Circulation: Fish have a two-chambered heart and single circulation, meaning blood passes through the heart only once per circuit of the body.
• Mammalian Circulation (Double Circulation): Mammals have a four-chambered heart and a double circulatory system. Blood passes through the heart twice for each circuit of the body. The right side pumps deoxygenated blood to the lungs for oxygenation, and the left side pumps oxygenated blood to the rest of the body.
• Heart Structure: The heart has four chambers (two atria and two ventricles). The ventricles have thicker walls because of the higher pressure needed to pump blood throughout the body. The septum separates the left and right sides of the heart, preventing mixing of oxygenated and deoxygenated blood. Coronary arteries supply blood to deliver oxygen and nutrients to the heart muscle.
• Heart Valves: Atrioventricular valves between atria and ventricles and semilunar valves at the artery exits prevent backflow of blood.
• Heart Disease: Coronary heart disease occurs when coronary arteries become partially or completely blocked by fatty deposits (plaques) - reducing the elasticity of the arteries and the flow of blood. This can lead to angina (chest pain) or a heart attack.
• Risk Factors for Coronary Heart Disease: Poor diet (high in saturated fat), stress, smoking, genetic predisposition, and age.
• Treatment for Coronary Heart Disease: Angioplasty (inserting a balloon into a blocked artery to flatten the plaque and insert a stent) and coronary bypass surgery (creating a new pathway for blood using a vessel from another part of the body) are two surgical interventions.
• Blood Vessels: Arteries carry oxygenated blood away from the heart with thick muscular walls that withstand higher pressure. Veins carry deoxygenated blood toward the heart with thin walls to accommodate lower pressure. Capillaries connect arteries and veins with thin walls (one cell thick) ideal for gas exchange. Blood flows in arterioles to capillaries and into venules. Shunt vessels are found in some vascular systems that can open or close to control blood flow to different parts of the body.
• Lymph Fluid: Excess tissue fluid leaks out of capillaries and enters the lymphatic vessels, becoming lymph. Lymph contains water, dissolved nutrients and minerals, and waste products. The lymphatic system returns lymph to the bloodstream—also helping to combat infection.

Blood

• Components: Blood is made up of plasma (liquid portion), red blood cells (carry oxygen), white blood cells (fight infection), and platelets (blood clotting).
• Red Blood Cells (Erythrocytes): Biconcave discs that contain hemoglobin facilitating oxygen transport.
• White Blood Cells (Leukocytes): Various types with different functions in the immune system. Phagocytes ingest pathogens and lymphocytes produce antibodies.
• Platelets: Cell fragments important for blood clotting.
• Plasma: Straw-colored liquid containing water, salts, proteins, glucose, hormones, and cellular waste products. It transports various substances throughout the body.
• Blood Clotting: A process preventing excessive blood loss. Damaged blood vessels initiate a cascade of reactions, causing fibrinogen (soluble protein in the plasma) to convert to fibrin (insoluble protein). Fibrin forms a mesh, trapping red blood cells, platelets, and other substances to form a clot.