Download 6.2 The Blood System

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
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
2 atria which are on the top (right and left)
2 ventricles which are on the b (right and
left)
Flow of Blood Heart
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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
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- SA is a specialized set of cardiac cells that
generate an electric impulse
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- 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
rate

system also influences heart
Increase or decrease by releasing
adrenalin
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
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
Capillaries
 Most
numerous of all blood vessels
 Contain only endothelium
 One cell thick
 Carry out exchange of materials between
blood and body cells
Blood flow through arteries, veins and
capillaries
Heart  arteries  arterioles  capillaries 
venules  veins  heart
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
Endothelium,
Smooth
muscle,
connective
tissue (with
elastic fibers)
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
Red Blood
Cells
Carry
oxygen
White Blood
Cells
Fight
Infection
Cell
fragments
called…
Help with
blood clotting
A strawcoloured
liquid
called…
Plasma
Carries
dissolved
substances:
CO2
Other wastes
Hormones
Food molecules