6.2 The Blood System

The Heart Transport system consists of the heart and associated blood vessels Heart pumps blood to pulmonary circuit (lungs) for gas exchange The heart consists of 4 chambers 2 atria which are on the top (right and left) 2 ventricles which are on the b (right and left)

Flow of Blood Heart Blood enters right atrium from vena cava Goes through the Tricuspid valve Move to the right ventricle Pumped through the pulmonary valve (pulmonary artery) To the lungs (gas exchange)(pulmonary veins) To the left atrium Through the Bicuspid valve To the left ventricle Through the aortic valve and out of the heart

Two Circulatory Paths Systemic: blood flows from the heart to the body (out the aorta and back through the vena cava) Pulmonary: blood flows from the heart to the lungs (out through the pulmonary artery to the lungs and back to the heart through the pulmonary vein)

Coronary Arteries Located outside of the heart and supply the heart cells with nutrients and clear metabolic waste products Can become blocked which can lead to a heart attack

Actions of the Heart Atria receive blood from body (right) and from the lungs (left) Ventricles are more powerful: pump blood a greater distance When AV valves are closed (atrioventricular) then the semilunar valves are open and vica versa Valves control the direction of blood flow

Control of the Heart Myogenic muscle contraction - Signal for heartbeat comes from the heart not the brain - Signal originates in the Sinoatrial Node (SA) signal is then sent to the AV node - SA is a specialized set of cardiac cells that generate an electric impulse - The impluse spreads across the atria at a speed of approx 1m per sec., causing the atria to contract

SA node and Bundle of His

Influences to heart rate Heart beat set by SA node Nervous system can influence heart rate by impulses delivered by medulla oblongata Increase or decrease if there is a need for oxygen Endocrine system also influences heart rate Increase or decrease by releasing adrenalin

Blood flow through arteries, veins and capillaries Heart  arteries  arterioles  capillaries  venules  veins  heart

Arteries Largest circulatory vessels Take blood away from the heart Have high pressure Aorta is the largest artery in the body Most carry oxygenated blood except the pulmonary artery Have muscle cells surrounding Assist in maintaining blood pressure between pump cycles

Veins Bring blood back to the heart Carry most deoxygenated blood (except the pulmonary vein) Superior and inferior vena cava (top and bottom) bring blood back to the heart Some veins have valves to ensure circulation and prevent backflow

Capillaries Most numerous of all blood vessels Contain only endothelium(permeable walls) One cell thick Carry out exchange of materials between blood and body cells(tissues)

Vessel Tissue Size Function Artery Endothelium, Smooth muscle, connective tissue (with elastic fibers) Largest (thick layer of smooth muscle and connective tissue) Takes blood away from the heart and helps maintain blood pressure (pumps blood) Vein Second largest (thin layer of smooth muscle & connective tissue) Brings blood back to heart and helps maintain blood pressure (pumps blood) Capillary Endothelium only Thinnest and most numerous Allows exchange of material with body cells

Composition of Blood Cell fragments called… Platelets A straw-coloured liquid called… Plasma Red Blood Cells White Blood Cells Carries dissolved substances: CO2 Other wastes Hormones Food molecules Carry oxygen Fight Infection Help with blood clotting