The Transport System IB topic 6.2

The transport system Mammals have a closed circulation Blood is pumped by the heart and circulated in a continuous system of arteries, veins, and capillaries Under pressure The heart has four chambers The heart is divided into right and left sides Blood flows from the right side of the heart to the lungs, then back to the left side of the heart From here, it is pumped around the rest of the body and back to the right side of the heart Blood passes twice through the heart in every single circulation of the body (double circulation)

Features of the circulatory system Advantages in mammalian circulation: Simultaneous high pressure delivery of oxygenated blood to all regions of the body Oxygenated blood reaches respiring tissues

Blood Blood is tissue Consists of: Liquid medium called plasma Erythrocytes (RBC) Involved in transport of respiratory gases (O2, CO2) Leucocytes (WBC) Combat infection Lymphocytes Form antibodies Phagocytes Ingest bacteria or cell fragments Platelets Blood clotting mechanism

Blood break-down Blood is: 55% plasma 45% cells Plasma is: 90% water 10% dissolved substances (proteins, salts, lipids) 45% cells RBC, WBC, platelets

Blood transports … Nutrients Oxygen Carbon dioxide Hormones Antibodies Urea Heat

The plumbing of the circulation system There are three types of vessels: Arteries: carry blood away from the heart Veins: carry blood back to the heart Capillaries: fine networks linking arteries and veins Both arteries and veins have strong, elastic walls Arteries are very much thicker and stronger Strength: collagen Elastic: smooth muscle fibers Capillaries Endothelium (inner layer) Branch No cell is far from a capillary

Why the differences? Blood leaving the heart is under high pressure Thick arteries By the time blood reaches the capillaries , the pressure has decreased greatly Thinner capillaries and veins Also, low pressure may mean backflow, which is why veins have valves Valves are opened by blood pressure from behind

Differences Capillary – site of exchange Artery – carries blood away from heart under high pressure Vein – carries blood back to heart under low pressure Outer Layer (collagen) Absent Present Middle Layer (elastic fibers and involuntary muscle fibers) Thick layer Thin layer Inner layer (or endothelium) Valves

The arrangement of arteries and veins The right side Pumps deoxygenated blood to the lungs Arteries, veins, capillaries = pulmonary circulation The left side Pumps oxygenated blood to the rest of the body Arteries, veins, capillaries = systemic circulation Aorta (artery)

Process The branching sequence of circulation: Aorta  artery  arteriole  capillary  venule  vein  vena cava Vena cava carries blood back to the heart

The Heart About the size of a clenched fist

The heart as a pump Divided into 4 chambers Upper: thin walled atria (atrium = singular) Receive blood into the heart Lower: thick walled ventricles The left is much thicker than the right The volumes are identical Pump blood out of the heart You should know the flow of blood

The heart as a pump Coronary arteries supply the walls of the heart with oxygenated blood Valves prevent backflow Atrio-ventricular valves prevent backflow from ventricles to atria Right side: tricuspid valve Left side: bicuspid or mitral valve Tendons are attached to prevent folding back Semi-lunar valves separates the ventricles from pulmonary artery (right side) and aorta (left side)

Animations http://www.nhlbi.nih.gov/health/health-topics/topics/hhw/contraction.html Penn health cardiology and cardiac surgery http://www.pennhealth.com/health_info/animationplayer/