Download HUMAN TRANSPORT SYSTEM ( lesson 3 )

HUMAN TRANSPORT SYSTEM
Composed of two systems :
The closed circulatory system ( The blood
vascular system ) : consists of :
Heart and Blood Vessels through which the
blood flows .
2) The lymphatic system : consists of :
Lymph nodes and lymph vessels through
which the lymph flows .
CIRCULATORY SYSTEM
HEART :
- hollow muscular organ , lies nearly in
the middle of the chest cavity
- encloses in Pericardium which protects
the heart + facilitates its pumping action
- the heart divided into 4 chambers :
Upper 2 Atria ( Auricles ) , thin walls ,
receive blood from veins and pumped
to ventricles Lower 2 Ventricles , thick
walls , receive blood from Atria and pumped
it through arteries
- the heart divided longitudinally by
muscular walls into right and left sides .
- each atrium connected to its ventricle
by opening guarded by valve :
- Right valve is the Tricuspid ( 3 flaps )
- Left valve is the Bicuspid or the Mitral
valve ( 2 flaps ) each valve consists of
thin flaps whose free edges attached by
tendons to the ventricle wall so it prevent
the flaps from turning inside ,permitting
flow of blood in one direction , from
atrium to ventricle , not the reverse
direction
- there are Semilunar valves :
Aortic valve at the connection between
heart and Aorta
Pulmonary valve at the connection between
heart and Pulmonary artery
G.R ... Walls of Atria are less thick than
walls of Ventricles
because Ventricles pump blood to a longer
distance than Atria .
G.R ... Walls of left ventricle is thicker
than walls of right ventricle
because left ventricle pump the blood to a
longer distance than right ventricle
Blood Vessels
:
A) Arteries :
wide vessels , carry blood from heart to
body organs , usually buried between
muscles ,pulsating , consist of 3 layers :
- outer layer ( connective tissue coat )
- middle layer ( thick involuntary muscles
contract and relax by nerve fibers )
- inner layer ( endothelium ) , one row of
epithelial cells , with elastic fibers to
give elasticity during ventricular
contractions .
All Arteries carry Oxygenated blood except
Pulmonary artery which carries
Deoxygenated blood from right ventricle to
the lungs .
B) Veins :
narrow vessels , carry blood from body
organs to the heart , usually under the
skin , thinner than arteries , not
pulsating , there walls formed of 3 layers
but less elastic fibers and the middle
layer is less thick .
some veins contain internal valves , to
prevent back flow of blood + direct the
blood towards the heart .
All Veins carry Deoxygenated blood except
the 4 Pulmonary veins which carry
Oxygenatedblood from lungs to left atrium .
C) Capillaries :
tiny microscopic blood vessels ,
connecting arterioles to venules , diameter
7 - 10 micron ,thin wall , one row of
epithelial cells with tiny pores , its wall
0.001 micron to facilitate the quick
exchange of substances between blood
and tissue cells .
HEART BEATS
Rhythmic heart beats are spontaneous as
they originated from Cardiac tissue itself
It has proved that the heart continues
beating regularly even after it has been
disconnected from the body and Cardiac
nerves ( sympathetic + vagus nerves ) .
Source of Regular Rhythm of heart beats :
A) Sino-atrial node : S-A node : Pace-maker
of the heart : specialized cardiac muscular
bundle buried in right atrial wall near
connection between right auricle and large
veins , it sends impulses continuously
stimulating atrial contraction .
B) Atrio-Ventricular node : A-V node : at
the junction between Atria and Ventricles:
when electrical impulse reach A-V node ,
impulses spread through interventricular
septum causing ventricular contraction .
S-A node beats regularly throughout life ,
70 beats / minutes in normal age = 5 liters
of blood / minutes which is equal all the
blood of the body .
Heart beats change according to the
physical and psychological state of the
body .
- it is lowered during sleep and gradually
increases after waking up
- it is lowered during grief and increases
in state of joy
- it increases with sever physical effort
S-A node connected to 2 nerves " Cardiac
Nerves " .....
Vagus nerve lowers heart rate
Sympathetic nerve increases heart rate
Heart Sound :
First Heart Sound (Lubb) which is Low
pitched and due to closure of 2 valves
between Atria and Ventricles during
ventricular contraction
WHILE
Second Heart Sound (DUPP) is High pitched
and due to closure of Pulmonary and Aortic
valves during ventricular relaxation