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 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 Present

Middle Layer (elastic fibers and involuntary muscle fibers)

Absent Thick layer Thin layer

Inner layer (or endothelium)

Present Present Present

Valves Absent Absent Present

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 pumpDivided 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/an

imationplayer/