Download The Transport System

The Transport System
IB topic 6.2
The transport system
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Mammals have a closed circulation
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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
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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
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Advantages in mammalian circulation:
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Simultaneous high pressure delivery of
oxygenated blood to all regions of the body
Oxygenated blood reaches respiring tissues
Blood
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Blood is tissue
Consists of:
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Liquid medium called plasma
Erythrocytes (RBC)
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Involved in transport of respiratory gases (O2, CO2)
Leucocytes (WBC)
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Combat infection
 Lymphocytes
 Form antibodies
 Phagocytes
 Ingest bacteria or cell fragments
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Platelets
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Blood clotting mechanism
Blood break-down
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Blood is:
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55% plasma
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Plasma is:
 90% water
 10% dissolved substances (proteins, salts, lipids)
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45% cells
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RBC, WBC, platelets
Blood transports …
Nutrients
 Oxygen
 Carbon dioxide
 Hormones
 Antibodies
 Urea
 Heat
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The plumbing of the circulation system
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There are three types of vessels:
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Both arteries and veins have strong, elastic walls
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Arteries: carry blood away from the heart
Veins: carry blood back to the heart
Capillaries: fine networks linking arteries and veins
Arteries are very much thicker and stronger
Strength: collagen
Elastic: smooth muscle fibers
Capillaries
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Endothelium (inner layer)
Branch
No cell is far from a capillary
Why the differences?
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Blood leaving the heart is under high
pressure
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Thick arteries
By the time blood reaches the capillaries ,
the pressure has decreased greatly
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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
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The right side
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Pumps deoxygenated blood to the lungs
Arteries, veins, capillaries = pulmonary
circulation
The left side
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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
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The Heart
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About the size of a
clenched fist
The heart as a pump
Divided into 4 chambers
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Upper: thin walled atria (atrium = singular)
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Receive blood into the heart
Lower: thick walled ventricles
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The left is much thicker than the right
The volumes are identical
Pump blood out of the heart
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You should know the flow of blood
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The heart as a pump
Coronary arteries supply the walls of the
heart with oxygenated blood
 Valves prevent backflow
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Atrio-ventricular valves prevent backflow from
ventricles to atria
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Right side: tricuspid valve
Left side: bicuspid or mitral valve
 Tendons are attached to prevent folding back
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Semi-lunar valves separates the ventricles
from pulmonary artery (right side) and
aorta (left side)
Animations
http://www.nhlbi.nih.gov/health/healthtopics/topics/hhw/contraction.html
 Penn health cardiology and cardiac
surgery
 http://www.pennhealth.com/health_info/a
nimationplayer/
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