The circulatory system consists of the heart, blood, and blood vessels. The heart pumps blood through two circuits - the pulmonary circuit, which pumps blood to the lungs to receive oxygen and remove carbon dioxide, and the systemic circuit, which pumps oxygenated blood to the rest of the body. Blood flows from the heart through arteries, then to capillaries where gas exchange occurs, then through veins back to the heart. The circulatory system transports oxygen, nutrients, hormones and waste products throughout the body.
2. CIRCULATORY SYSTEM
The circulatory or cardiovascular system consists of
•The Heart
•The Blood
•Blood vessels
Together with the Lymphatic System, the Circulatory
System:
•Delivers oxygen and nutrients to cells
•Removes waste from cells
•Maintains the balance of water in the body.
WEBSITE:
The Heart: An online Exploration
http://www.sin.fi.ed/biosci/biosci.html
3. BLOOD
A specialised type of connective tissue
It is a thick liquid with a metallic taste
Blood accounts for about 8% of our total body weight
Blood volume in a healthy adult:
Male 5 – 6 L Female 4 – 5 L
Functions:
Blood performs a number of specialised functions:
Transports nutrients, oxygen, carbon dioxide, waste products and
hormones to cells and organs around the body
Protects us from bleeding to death, via clotting, and from disease, by
destroying invasive micro-organisms and toxic substances
Acts as a regulator of temperature (vessels constrict to conserve heat or
dilate to release heat to the surface for cooling), the water content in cells
and body pH.
4. Composition of blood:
1. Solid component (Blood cells)
45% of total volume
Red blood cells (erythrocytes), white blood cells
(leukocytes), or platelets (thrombocytes)
2. Liquid Component (Blood plasma)
55% of total blood volume
Composed of 91.5% water and 8.5% of nutrients, waste
products, proteins, enzymes and hormones
Straw coloured or yellowy solution
Nutrients from the small intestine is absorbed into the
plasma and transported around the body
5. RED BLOOD CELLS
Contains an oxygen carrying pigment called Haemoglobin (Hb).
This gives blood its red colour.
Oxygen (O2) is carried by Hb and transported from the lungs to all
cells. This reaction forms oxyhaemoglobin (aided by iron molecules)
Carbon dioxide (CO2) is also transported this way. Formation is
called carbaminohemoglobin
Life cycle is approximately 120 days and they are replaced at the rate
of 2 million per second
They are produced in red bone marrow from stem cells
Red blood cells function is to transport O2 and CO2 around the
body
6. PLATELETS
Small colour-less bodies that usually appear as
irregular spindles or discs that are much smaller than
RBC and WBC
Produced in red bone marrow
Life cycle is approximately 5 to 9 days
Platelets are involved in the process of clotting and
they help to repair slightly damaged blood vessels
7. WHITE BLOOD CELLS
Slightly larger than red blood cells
Classified according to the presence or absence of granules in
their cytoplasm
Life cycle is from a few hours to a few days
Produced in bone marrow and lymph tissue
They move to areas of infection or disease to engulf invading
bodies (puss is the accumulation of WBC)
9. ARTERIE
S
Carry blood away from the heart to tissues
Thick elastic walls as blood is pumped through them at high pressure in surges
Three layers
- endothelium lining
- involuntary muscle
- tough fibrous tissue
Surges are called heart beats
Pressure decreases as distance from the heart increases. Blood passes through
small vessels called arterioles
10. VEIN
S
Carry blood from tissues back to the heart
Thinner walls and less elastic as pressure decreases as the blood gets closer to
the heart
The contraction and relaxation of muscles assists the blood to stream back
steadily to the heart
Valves prevent the blood from flowing back the wrong way against a force of
gravity. After standing for a long time, legs can feel heavy and swollen. Blood pools
in the lower legs because of gravity and lack of movement. Once moving, the
muscles squeeze the blood up through the veins toward the heart.
Gravity affects blood flow – blood above the heart flows easily
11. CAPILLARIES
A very small network of vessels
One cell wide
Lie between arterioles and venules, connecting both systems
Semipermeable membrane where O2, CO2 and nutrients are
exchanged between the blood and the cells of the body
Feeds muscles, joints, tissues and organs in clusters
12. THE HEART
Involuntary cardiac muscle
Pericardium is a triple layered bag that surrounds, anchors and protects the heart
Four hollow chambers
- 2 atria
- 2 ventricles
Atria act as receiving chambers for blood returning to the heart. Small and thin as
they only pump next door
Ventricles are large as they propel the blood from the heart into circulation around
the body
Dense connective tissue called valves, prevent the back flow of blood into the
chambers by opening and shutting when the heart contracts and relaxes. Tricuspid
and Bicuspid valves
Heart contracts and squeezes blood into arteries – systole
Heart relaxes and fills with blood – diastole
13.
14.
15. Pulmonary Artery has deoxygenated blood travelling in
it. Other arteries have oxygenated blood. Being an
artery it still travels away from the heart
Pulmonary veins have oxygenated blood. Other veins
have deoxygenated blood.
16. ANATOMY OF THE HEART
ATRIUM: the receiving chamber of the heart
VENTRICLE: the propulsion chamber of the heart
SEPTUM: separates the two ventricles and the two atrium
VENA CAVA: returns blood from the systemic system to the right atrium
PULMONARY ARTERY: carries blood from the right ventricle to the lungs via
the circulatory system
PULMONARY VEIN: carries blood from the lungs to the left atrium
AORTA: carries blood from the left ventricle to the systemic circuit
around the body
MYOCARDIUM WALLS: have different thicknesses depending on the pressure
they are under eg atrium walls are thinner because it is
easier to push blood into the ventricles
ATRIOVENTRICULAR VALVES: these are forced shut as the ventricle pressure
increases, preventing back flow of blood into the atria when
the ventricles are pumping – they are bicuspid and tricuspid
SEMILUNAR VALVES: prevent blood returning to the ventricles after they have
completed contracting
SINUATRIAL VALVE: is the pacemaker. It controls
contractions and is found in the right atria.
17. PULMONARY AND SYSTEMIC CIRCULATION
The heart is actually a double pump that serves two circulations.
Two types of blood circuits are created:
Pulmonary circuit – circulates blood from the right side of the heart to
the lungs and then back to the heart.
Systemic circuit – pumps blood from the left side of the heart out to all
body tissues and then back to the right side.
PULMONARY CIRCUIT
Deoxygenated blood from the body enters the right atrium via 3 veins,
superior vena cava, inferior vena cava and coronary sinus. From here the
blood flows into the right ventricle, which pumps it to the lungs via the left
and right pulmonary arteries. In the lungs CO2 is released and O2 is picked
up.
SYSTEMIC CIRCUIT
Oxygenated blood then enters the left atrium via 4 pulmonary veins. The
blood flows into the left ventricle, from where it is
pumped up through the aorta and out to the upper and lower
body via a number of arteries.
18. The cycle
Oxygen-poor blood from the body collects in the right atrium,
which contracts, filling up the right ventricle
Right ventricle contracts and pushes blood to the lungs
In the lungs, blood loses carbon dioxide and picks up oxygen
Oxygen-rich blood returns to the left atrium, which contracts, filling up the left
ventricle
Powerful contractions of the left ventricle, expels oxygen-rich blood in the aorta,
from where artery branches distribute blood throughout the body.
In the muscles and body organs, blood releases oxygen and nutrients, and
absorb food and water from the intestines. Liver processes nutrients, and
together with kidneys, purifies the blood
Oxygen-poor blood returns to the heart through the veins.
Another cycle begins.
19.
20. SYSTEMIC CIRCUIT
This circuit has 4 major areas:
1.Coronary Circulation
Coronary arteries feed the cardiac muscle
2.Portal Circulation
Blood from the stomach and intestine returns through the liver and
then to the heart
3.Muscle circulation
Circulation to the muscles
4.Skin Circulation
Circulation to the skin
Hot weather → Blood vessels dilate
Cold weather → Blood vessels constrict
21. HEART RATE
Number of beats per minute
Resting heart rate is best taken when you first wake
up in the morning. It is a good indicator of the
efficiency and strength of the heart
Heart rate increases due to fear, excitement,
exercise, food ingestion, illness, smoking, drugs,
body position, age and temperature changes
Pulse is the pressure wave of blood continuing along
the arteries
Measurement of pulse is best taken from
the radial or carotid site. Take if for 6, 10,
15, 20 or 30 seconds and then multiply by
10, 6, 4, 3 or 2 respectively, to calculate
your heart rate over a minute.
22. HEART SOUNDS
2 sounds that accompany blood movement
Blood moves in spurts rather than a constant flow
1st spurt, caused by the ventricular contraction
(systole) this increases the pressure in the ventricles
The AV (tricuspid and bicuspid) valves shut quickly
due to this pressure and this sharp closure makes the
1st sound
2nd sound occurs as the ventricle relaxes (diastole),
the atria fills and the semilunar valves shut quickly
23. HEART DISORDERS
Abnormal heart rate: a regular heart rate lower than 60 and higher
than 100 is abnormal.
Heart block: SA node fails to send impulses which tell the heart to
contract. Ventricles contract at their own rate slower than the atria.
Arteriosclerosis: Hardening and narrowing of coronary arteries. If
an artery blocks then myocardial infarction occurs (heart attack)
Myocardial Infarction: blood flow is interrupted to heart muscle.
This tissue dies. Complete rest is needed. If a large area is starved
of oxygen, death will occur
Heart muscle can become infected
Valves of the heart can become ineffective
Cardiomyopathy – virus of the heart causing
heart to enlarge and harden making it ineffective.
Death will result if the heart is not transplanted.
24. HEART RATE CONTROL
HR is controlled by the involuntary (autonomous) nervous system
Sympathetic System – heart beats faster
Parasympathetic System – returns heart to normal
Electrical impulses from these systems stimulate the atria to contract
together. The impulses travel to the ventricles, which contract 0.1
seconds after the atria. The rate at which the sinoatrial node
(pacemaker) sends impulses determines heart rate.
25. Blood flow through the body:
Use your text, notes and knowledge to arrange the following
body processes into the correct order (no.1 and No. 12 are
already done)
1. Deoxygenated blood to the right atrium
2. Right ventricle
3. Deoxygenated blood to the lungs
4. Oxygenated blood from the lungs
5. Left atrium
6. Left ventricle
7. To body via aorta, arteries and arterioles
8. To capillaries
9. To tissues, organs and muscles
10.To capillaries
11.To veins
12.Deoxygenated blood back to the right atrium
26. BLOOD PRESSURE
Blood pressure is the pressure of the blood in the arteries as the heart
pumps it around the body.
Hence it is the arteries that are mainly at risk of damage from high blood
pressure.
Blood flow and blood pressure surge each time the heart contracts. The
peak pressure is called the systolic pressure.
The pressure falls as the heart relaxes to fill. This lower pressure is called
the diastolic pressure.
Blood pressure in each individual varies the whole time according to
numerous influences such as posture (whether you are lying or
standing), emotion, pain and sleep.
For example – blood pressure may be higher the first time that you visit a
new doctor. Readings tend to become lower as the patient relaxes with
subsequent visits.
The WHO (World Health Organisation) defines the following
“Normal adult blood pressure is arbitrarily defined as a systolic
pressure equal to or less than 140mmHg together with a diastolic
equal to or below 90 mmHg. Hypertension in adults is arbitrarily
defined as a systolic pressure equal to or greater than 160 mmHg
and/or diastolic pressure equal to or greater than 95 mmHg.”
27. FACTORS AFFECTING SYSTOLIC BLOOD
PRESSURE
Short term factors include –
Smoking – increases blood pressure, as the capillaries
constrict or reduce in size when the nicotine is present which
increases the resistance to blood flew. This effect lasts for about
20 minutes
Exercise – increases BP and HR (heart rate)
Fright, stress or anxiety – increases BP
Body position – affects BP due to the pull of gravity. Standing
increases BP while lying down decreases BP.
Long term factors include:
Diet – high intake of fat and salt can lead to a permanent
increase in BP into the unhealthy range. Fatty deposits narrow
the artery walls and lead to a loss of elasticity in artery walls
Stress – can cause high BP due to an imbalance in hormone
levels
Exercise – regular exercise can lead to a decrease in
blood pressure when at rest, if blood pressure has been
high
28. THE HEART
Stroke Volume (SV) – the volume of blood ejected into the aorta by
one ventricle during contraction (systole)
Cardiac Output (Q) – the total volume of blood pumped from a
ventricle per minute
Q = HR x SV
Blood pressure (BP) – it is the pressure exerted in systemic arteries by
the contraction and relaxation of the ventricles. Blood flows along a
pressure gradient from areas of higher pressure to areas of lower pressure.
BP is expressed in terms of mm of Mercury (mmHg)
Systole contraction ie 120 (Normal +/- 10)
Diastole relaxation 80 mmHg
*BP can depend on sex, age,
exercise and condition of
the cardiovascular system.
29. THE EFFECTS OF EXERCISE ON THE
HEART
During exercise, your heart rate will increase quite
rapidly in proportion to the increase in workload
intensity until a maximum point, where it levels off.
This point is called your maximum heart rate – HR
max.
To determine HR max:
220 – age = HR max
Heart rate is seen to rise with
work intensity, as anyone knows
after climbing a long flight of
stairs. But unlike cardiac output
and VO2
, the relationship between
heart rate and absolute work
intensity is variable across
individuals; like your grandmother
(Black line) and the marathon
runner (Black line).
30. For training purposes it is often recommended that people
exercise at certain percentages of their HR
•Long distance runners would tire quickly if working at
100% of HR max, therefore they train at lower
intensities of 75 – 85%.
31. CARDIAC ADAPTATIONS TO EXERCISE
Cardiac Output – increases linearly with increases in intensity up to exhaustion
SV – increases due to more blood returning to the heart. Maximal SV occurs during
sub-maximal work.
HR – increases as intensity increases up to a maximum
Systolic BP – increases linearly with increased exercise intensity due to an increase
in Q.
Blood Flow – increased blood flow to working muscles and skin, 80 – 85% →
muscles.
Blood Plasma Volume – decreases especially in hot weather due to increased
sweating.
Other Adaptations:
Increase in arteriovenous O2 difference
Increase in blood acidity (more lactic acid)
Decrease in muscle glycogen
Increase in coronary blood flow
*Over time with training, the heart undergoes other physiological changes:
- it becomes stronger and in some cases slightly larger
- resting heart rate will decrease
32. Immediate (Acute) Effects Area Long-Term (Chronic) Effects
HR increases
CO increases
SV increases
Increases coronary circulation
Maximum HR may be reached
Heart Resting HR decreases
SV increases at test and exercise
Increases blood supply to the heart muscle
at rest and work
Increased size of left ventricle
Maximum HR remains the same
Increased BP on artery walls
Capillaries and veins dilate to allow
increased blood flow
One way valves in veins help return blood
to the heart
Arteries
Capillaries
Veins
Elasticity of artery walls is maintained
Reduced build up of fatty deposits in
arteries
Decreased risk of high BP and CV disease
Increased capillary supply to heart and
skeletal muscles
Increased speed of blood flow
Increased temperature of muscles
Oxygen levels in venous blood decreases
as the body uses more oxygen for exercise
Blood is redistributed from the internal
organs to the working muscles
Blood Increased blood volume
Increased haemoglobin’ count
Increased oxygen carrying ability
SUMMARY OF THE EFFECTS OF EXERCISE