Download General plan of the mammalian circulatory system

21.4.2 Mammalian Circulatory System
The flow of blood is maintained in 3 ways:
1 The pumping action of the heart
 arteries and capillaries
2 Contraction of skeletal muscles
 veins (aided by valves)
3 Inspiratory movements
 draws blood into the heart by the reduced
pressure
General plan
of the
mammalian
circulatory
system
How blood flows:
the circulatory
system
The mammalian
circulatory plan
How blood flows:
the circulatory
system
Complete
circulation
consists of two
pathways:
pulmonary (lung)
circulation &
systemic (body)
circulation
How blood flows:
the circulatory
system
heart: coronary
arteries & veins
kidney: renal
arteries & veins
liver: hepatic artery
& vein;
hepatic portal
vein (from gut)
How blood flows:
the circulatory
system
aorta: aortic arch
& dorsal aorta
venae cavae:
superior (from head)
& inferior (from body)
Usually arteries
are oxygenated,
veins are
deoxygenated
Structure of the mammalian heart
Foetal circulation
The mammalian heart
lung
heart
liver
stomach
Our hearts are protected by our rib cages
The mammalian heart
superior
vena cava
aorta
pulmonary
artery
pulmonary
veins
left auricle
right
auricle
right
ventricle
inferior
vena cava
coronary
artery
coronary vein
left
ventricle
21.5 Heart Structure & Action
21.5.1 Structure of the Mammalian Heart
- Pericardium: membrane of the heart
- Cardiac muscles works (contracts) for 24 hours without
rest
- Coronary artery provides nutrients & oxygen to cardiac
muscles
Coronary veins carry away wastes and carbon dioxide
from heart muscles
- Interventricular septum divides the heart into right and
left halves
- The heart is divided into 4 chambers:
- The left & right auricles (atria) and
- The left & right ventricles
Auricles
- Left & right auricles receive blood from veins
and drain blood into the ventricles;
- have thinner walls than ventricles
- Right auricle receives deoxygenated blood
from venae cavae (superior & inferior)
- Left auricle receives oxygenated blood from
pulmonary veins
Ventricles
- pumps blood to all parts of the body;
have thicker, more muscular walls than the auricles
- Right ventricle pumps deoxygenated blood to the lungs
through the pulmonary artery
- Left ventricle pumps oxygenated blood into the aorta to
deliver blood around the body (except the lungs)
- Left ventricle has thicker wall than right ventricle
because it has to pump blood all around the body,
while the right ventricle only pumps blood to the lungs
which are very close to the heart
Valves
- enable blood to flow in only one direction:
1.Tricuspid valve: between right auricle and right
ventricle
2.Bicuspid valve: between left auricle and left ventricle
Both are attached by heart tendon to the muscular
walls of ventricles in order to prevent the valves from
being turned inside out
3.Semilunar valves: prevents blood flowing back from
aorta and pulmonary artery
tendon
valve
21.5.2 Control of Heart Beat (Cardiac Cycle)
All vertebrates are myogenic, i.e. the heart beat is
initiated from within the heart muscle itself
rather than a nerve impulse out it.
Neurogenic means the heart beat is initiated by
nerves, e.g. in insects.
The electronic heart
pacemaker (SA node)
Nucleus
Connective
tissue
Cardiac muscle (LS)
Fibre
with
striations
Sino-atrial node (SA node)
- located in wall of R A near the vena cava
'pace-maker' which determines the basic rate of
heart beat:
- wave of contraction from SA node
 both atria
 atrio-ventricular (AV) node
 Purkinje fibres (bundle of His)
 apex of ventricles
 contraction from ventricular apex upwards

Cardiac Cycle
Cardiac Cycle
 Systole - heart contraction
 Diastole - heart relaxation

21.5.3 Factors Modifying Heart Beat
Cardiac output:
Volume of blood pumped at heart beat x no. of
beats/unit time
- controlled by medulla oblongata by 2 centres:
cardio-acceleratory centre (sympathetic) and
cardio-inhibitory centre (parasympathetic)
During heavy exercise:
CO2   pH 
 chemoreceptor in carotid artery
 cardio-acceleratory centre
 heart beat  (to remove more CO2)
until CO2  (pH )
 detected by carotid receptors
 cardio-inhitory centre
 heart beat 
also:
stretch receptors in aorta, carotid artery stimulated
 cardio-inhibitory centre
 heart beat 
stretch receptors in vena cava stimulated
 cardio-acceleratory centre
 heart beat 
21.5.4 Maintenance & Control of Blood Pressure
vasoconstriction: blood vessels narrowed
 blood pressure 
vasodilation: blood vessels dilated
 blood pressure 
Both controlled by vaso-motor centre in medulla
oblongata  arterioles in body (constrict/dilate)
baroreceptors: pressure receptors in carotid artery
detect blood pressure changes and relay impulses
to the vaso-motor centre
examples:
blood pressure   baroreceptors
 vaso-motor centre
 sympathetic nerve
 arterioles
 vasoconstriction
 b p 
blood pressure   baroreceptors
 vaso-motor centre
 parasympathetic nerve
 arterioles
 vasodilation
 b p 
Factors causing blood pressure increases:
1. CO2  blood pressure 
 speed to deliver blood to heart 
 remove more carbon dioxide
2. Hormones, e.g. adrenaline
 raises blood pressure
Pressure changes
in the atria,
ventricles &
aorta during one
cardiac cycle
21.5.5 Heart Disease - coronary heart disease
1. Coronary thrombosis
- a blood clot blocking the coronary vessel
Wall of artery
Thrombus (clot)
Plaque on
inner wall of
artery
21.5.5 Heart Disease - coronary heart disease
1. Coronary thrombosis
- a blood clot blocking the coronary vessel
2. Atherosclerosis (hardening of the arteries)
- barrowing of the arteries due to fat,
fibrous, or salt deposits
3. Spasm
- repeated contractions of the muscles in the
coronary attery walls
Heart attack
Cholesterol,
Narrows the lumen in
arteries,
Decreases blood supply
to organs
smooth lining
blood flow restricted
artery blocked
by blood clot
fatty &
fibrous
deposits
血液中的脂肪物質如膽固醇,積聚在動脈的內壁,
便會使動脈內腔變窄,繼而使這些動脈提供給器
官的血液減少。
The human
lymphatic
system

The lymphatic system

It consists of
lymph vessels with lymph.
21.6 Lymphatic System
21.6.1 Tissue fluid and its formation
- composition same as blood but without RBCs,
platelets & proteins
because they are too large to leak out of the
capillaries
- forms a link between blood and cells, providing
a medium for exchange of materials between
blood & cells
Exchange of materials between blood & body cells
Lymph
some tissue fluid returns to capillaries by osmosis while
some (about 10%) goes into lymph capillaries;
this fluid is now called lymph
Path:
Blood  lymph capillaries
 lymph vessels
 lymph ducts
 Blood
- Lymph re-enters blood
Formation and destination of tissue fluid
At the arterial end of a capillary, liquid is
forced out as tissue fluid which is similar
to plasma in composition except its has
no plasma proteins, platelets & RBCs.
At the venous end, some fluid returns to
blood while some enters lymph vessels
which eventually join to a vein near the
heart and thus returns to blood finally.
Lymph is driven by contraction of
surrounding muscles, aided by valves which
enable one-way flow to the neck.
Lymph nodes
- filter lymph passing through;
with numerous WBCs to kill bacteria
or neutralize toxins for bodily defence
- during infection these nodes frequently swell
- major sites of lymphocytes production
Movement of lymph through the lymphatic system:
1. Hydrostatic pressure
2. Muscle contraction
3. Inspiratory movement
4.Valves to ensure one-way traffic towards the
heart
Lymphatic System
and the Circulatory
System
Functions of the lymphatic system
1 Transport of tissue fluid back into the
blood circulation
2 Transport of fat from intestinal villi
3 As a bridge for the exchange of
materials between capillaries and tissue
cells
4 As a site for body defence (lymph nodes
with WBCs)