The Circulatory System Biology 1-2

The Circulatory System The circulatory system carries blood and lymph throughout the body. Blood carries gases, nutrients and wastes. Lymph is water and things that leaked from the blood vessels. Includes the heart, blood vessels and lymph nodes.

Blood Vessels Five types of blood vessels: Artery-carries blood from the heart. Thick wall of smooth muscle to pump blood. Arteriole-small artery. Vein-carries blood to the heart. Thin, lack the smooth muscle of the arteries. Usually buried in muscle; when muscle contracts, it squeezes the blood back toward the heart. Venule-small vein.

Blood Vessels cont’d Capillary-connect arterioles to venules. Where exchange between the blood and tissues takes place. Oxygen/nutrients are dropped off, carbon dioxide/wastes are picked up.

Blood Blood is made of: Plasma-straw-colored, mostly water includes: proteins, salts, other dissolved things. Red blood cells-carry oxygen. White blood cells-fight infections.

Blood cont’d Platelets are cell pieces in the blood used to close cuts. Platelets stick together, forming a plug to stop blood loss. The protein fibrin forms a net, strengthening the platelet plug. New cells (mitosis) fill in and replace the plug. Scars form when collagen fills in, not original tissue.

The Heart and Circulation Oxygen-poor blood enters the heart through the right atrium. Blood from the head/shoulders enters the right atrium through the superior vena cava. Blood from the rest of the body enters from the inferior vena cava.

The Heart cont’d The right atrium pumps blood to the right ventricle. Right ventricle pushes blood to the lungs through the pulmonary artery.

The Heart cont’d Blood picks up oxygen at the lungs and returns through the pulmonary vein. Enters the heart through the left atrium. Left atrium pumps blood to the left ventricle.

The Heart cont’d Blood leaves the left atrium through the aorta to deliver oxygen-rich blood to the rest of the body.

The Heart cont’d The cardiac cycle is the contraction and relaxation of the heart. During relaxation (diastole) blood fills the atria and ventricles. During contraction (systole) blood is pumped into/out of the ventricles.

The Heart cont’d Blood pressure is the force that blood exerts on the walls of the blood vessels. Created when the left ventricle contracts. Increased pressure (systolic pressure) stretches the arterial wall. Pulse-rhythmic stretching of the arteries. During diastole, the heart relaxes and the pressure on the arteries is at its lowest (diastolic pressure).

The Lymphatic System Consists of: Lymph Lymph vessels-carry lymph and are found near blood vessels. Lymph nodes-produce cells found in lymph that fight infections. Filter fluids before they go back into the blood.

Lymphatic System cont’d The lymphatic system does three things. Returns lost fluids to the blood. Carries fat from the small intestine to the liver. Produces cells to fight infections.