The Mammalian Circulatory System (Circulation)
The pulmonary circulation
The cardiac circulation
The systemic circulation
The Mammalian Circulatory System (Components)
Fluid Tissue
Transport vessels
Pumping Mechanism
Blood
Arteries, Veins, arterioles,
venules & Capillaries
Heart
Transport vessels
 Arteries
• Structure
 Tunica intima (endothelium)
 Tunica media
 Tunica adventitia
 Tunica intima (endothelium): A single layer of endothelial cells
 Ttunica media: Alternating circular smooth muscle fibres and bands
of elastic fibres
 Tunica adventitia: Mainly connective tissue and few elastic fibres
Transport vessels
 Veins
• Structure
 Tunica intima (endothelium)
 Tunica media
 Tunica adventitia
valve
* Veins cannot contract behind the blood to keep it moving
towards the heart however they are equipped with valves that
prevent the blood from flowing backward
The “muscle pump” helping to return venous blood to the heart
Transport vessels
 Capillaries
• Structure
 Tunica intima (endothelium): One cell in thickness
Blood
Accidents
The Transport Medium
(Blood)
Platelets
R.B.Cs (Erythrocytes)
Plasma
White Blood Cells (leucocytes)
%
55 %
%
44 %
%
1%
R.B.Cs, White Blood Cells, and Platelets are called the formed elements of the
blood.
The Transport Medium
(Blood)
Blood cells
R.B.Cs (Erythrocytes)
White Blood Cells (leukocytes)
Agranulocytes
Granulocytes
Eosinophils
Basophils
Neutrophils
Lymphocytes
B - lymphocytes
Monocytes
T - lymphocytes
Red Blood Cells
Oxygen Pick-up and release factors
What are the factors that affect oxygen pick-up and release by the respiratory
pigment?
These factors are
The concentration of oxygen
The acidity of the surrounding fluid
Temperature
•• The
The concentration
concentration of
of oxygen
oxygen isis usually
usually measured
measured in
in kPa.
kPa.
•• Since
Since oxygen
oxygen makes
makes up
up about
about 21%
21% of
of the
the atmospheric
atmospheric pressure,
pressure, and
and the
the air
air
pressure is 101 kPa at sea level, then oxygen partial pressure in the lungs should
be: 0.21 x 101 kPa = 21.21 kPa
What is the effect of a low oxygen partial pressure?
• When oxygen partial pressure is low, the bond that links oxygen to the haem group
weakens, and oxygen will be released easily.
• Similarly an increase in the acidity will loosen the bond and lead to the release of
oxygen.
• The increase in the acidity of the blood results from the increase in the
concentration of carbon dioxide
• Another factor that influences the rate at which oxygen dissociates from
haemoglobin is the temperature.
In cooler temperatures, haemoglobin releases oxygen more slowly.
What is the significance of the effect of temperature?
* This is no problem for warm-blooded animals, whose body temperature remains
constant, however it is an important factor in determining the activity level of coldblooded animals like amphibians and reptiles.
Carbon dioxide Pick-up
Who are the players?
Plasma
RBCs
About 20% bind to
haemoglobin to form
carbaminohaemoglobin
Water in the plasma (90%)
About 10% are carried
by the blood plasma
The blood plasma buffer system
H2O + CO2
H2CO3
KHb + H+
K+ + H Hb
H+ + HCO3-
The rest of the 70%
combines with water to
form carbonic acid
White Blood Cells
Why are “White Blood Cells” called so?
• In contrast to RBCs , White blood cells are nucleated and colourless, hence the
name “White Blood Cells”
What are the different types of white blood cells?
• There are several types of white blood cells, two of the most important diseasefighting cells are macrophages and lymphocytes.
What is the role of macrophages in fighting disease?
Macrophages are phagocytic cells that can pass through the walls of capillaries to
engulf and digest pathogens.
Macrophages are part of the body’s innate immune response, which is the body’s
generalized response to infection.
What is the role of lymphocytes in fighting disease?
• Lymphocytes are non phagocytic cells that play a role in
the body’s acquired immune response.
• This is the response that allows the body to fend against
specific pathogens (Viruses).
• There are two types of lymphocytes: T lymphocytes
which mature in the thymus gland, and B lymphocytes
which arise from the bone marrow
What are the types of lymphocytes?
Types of lymphocytes
T lymphocytes
Helper T cells
Bind to the antigen
The reaction triggers the
multiplication of
T cells
B lymphocytes
Cytotoxic T cells
destroy virally
infected cells and
tumor cells
Plasma B cells
Memory B cells
Produce antibodies at a
rate of 2000 per second
These cells persist for a long
time after an infection has
resolved and can respond
quickly following a second
exposure to the same antigen
Antibodies are antigen
specific they have constant
regions and variable
regions, these variable
regions act like a (lock) for
the antigens (key) to bind.
Variable regions
Constant region
Platelets
What are platelets?
Platelets are fragments of cells that were created when larger cells in
the bone marrow broke apart, each platelet lasts about a week to 10
days.
What is the main function of platelets?
The important role of blood platelets is blood clotting, therefore
preventing the body from excessive blood loss.
What are the steps of blood clotting?
Substances released
by a broken blood
vessel attract platelets
to the site of the
broken vessel
Platelets collect
and rupture
releasing
chemicals
Thromboplastin + Prothrombin + Ca+
Thrombin + Fibrinogen
Chemicals from the
platelets + clotting
agents from the
plasma produce the
enzyme
thromboplastin
Thrombin
Fibrin
* Fibrin is an insoluble material that forms a mesh of strands around the area of
injury, trapping blood cells and forming the clot.
Blood Plasma
Composition of plasma
Water
Blood proteins Fibrinogen
Serum albumin Serum globulin
92 %
7%
Organic substances
e.g. Urea
0.14 %
Inorganic ions
- Calcium
- Chlorine
- Magnesium
- Potassium
- Sodium
- Bicarbonates
- Carbonates
- Phosphates
0.93 %
Blood Plasma
What is serum?
When the fibrinogen and other clotting agents are removed from the blood, the
straw coloured liquid that remains is called serum.
What is the composition of serum?
Serum contains hormones, electrolytes, enzymes, antibodies and waste materials.
What is anti sera?
Serum from an immune animal or a person to a particular disease can be injected
into a patient to provide temporary immunity from the disease.
Blood Groups
Blood Type
Protein markers
Serum antibodies
A
A
anti-B
B
B
anti-A
O
neither
AB
both A and B
anti-A and anti-B
neither
Blood Types Determine Blood Compatibility
Rhesus factor and blood compatibility
• People who carry the Rh protein are called Rh – positive, while
people without the protein are called Rh – negative.
• Unlike the A and B antibodies, the anti – Rh antibody is not always
present in the blood, it is manufactured by the body only after the
exposure to the Rh protein marker.
Rh factor and the possible pregnancy complications:
This becomes a problem when an Rh-positive father and an Rhnegative mother conceive a child who is Rh-positive, and red blood
cells leak across the placenta into the mother’s circulatory system
initiating an immune response and the production of anti-Rh
antibodies, this will destroy all the foetus red blood cells and put all
the subsequent pregnancies at risk.
This is overcome by giving the mother anti-Rh antibodies midway
through her first pregnancy or no later than 72 hours after giving
birth. This will result in the destruction of any of the baby’s red
blood cells that have crossed the placenta before the mother’s
immune system starts producing antibodies.
The Cardiac Circulation
The Heart
How is the control of the heartbeat?
The regulation of the heartbeat comes from within the
heart itself, the impulse that triggers the heartbeat
originates from a specialized muscle tissue in the wall of
the right atrium, stimulating the muscle fibres to contract
and relax rhythmically, this tissue is called the sinoatrial
node (S-A) node.
The sinoatrial node is more commonly known as the
pacemaker.
What is the atrioventricular node (A-V node) ?
As the atria contract the impulse reaches another node
called the atrioventricular node (A-V node), this node is
located near the atria on the partition between the two
ventricles, it transmits the electrical impulse all over the
walls of the ventricles to start their contraction.
The electrical signals can be measured using a device called
the electrocardiogram (ECG), the tracing produced is called
the electrocardiograph.
Cardiac Conduction
• SA node: cardiac
pacemaker
• AV node: relay
impulse
• AV bundle and
Purkinje fibers:
carry impulse to
ventricles
Electrocardiograms (ECG)
• Three formations
– P wave: impulse across atria
– QRS complex: spread of impulse down septum,
around ventricles in Purkinje fibers
– T wave: end of electrical activity in ventricles
Electrocardiograms (ECG)
Regular pattern
Irregularly irregular,
no set pattern
Chemical regulation of the heart rate
Increasing the heart rate
CO2 increases
Receptors in the blood vessel
transmit the information to the
medulla oblongata
Medulla oblongata sends impulses to
release noradrenaline that makes the
node fire rapidly.
Decreasing the heart rate
Increased heart rate means
increased blood pressure
Receptors in the blood vessels sense the
increase in the blood pressure and
transmit the information to the medulla
oblongata
Medulla oblongata sends impulses to
release acetylcholine that makes the
node fire slowly.
The cardiac output and the fitness
What is the cardiac output?
The cardiac output: is the amount of blood pumped by the heart
in one minute.
The more the cardiac output
The more the oxygen delivered to the body
The more the fitness
What is the stroke volume?
The stroke volume: is the amount of blood forced out of the
heart with each heart beat.
Cardiac output = stroke volume x heart rate
* The average person has a stroke volume of about 70 ml and a resting
heart rate of about 70 beats per minute.
The stroke volume and the fitness
The more the stroke volume
The more the fitness
The heart rate and the fitness
The lower the heart rate at rest
The more the fitness
How?
The lower heart rate is an indication to the higher stroke
volume, in elite athletes the heart rate at rest could reach
30 beats per minute, with a maximum cardiac output of 4
litres per minute.
Heart Defects
• Heart murmurs
Cause
• Abnormal sound of blood flow in a
narrow or incompetent valve
• Can be from a “hole in the heart”
between the atria or ventricles
• Mitral valve prolapse
Cause
• The flaps of the mitral valves close unevenly
Coronary artery by-pass grafting (CABG)
Reducing the Risk of Cardiovascular Disease
•
•
•
•
•
Smoking: Don’t
Blood lipids: monitor cholesterol levels
Exercise: regular and moderate
Blood pressure: treat hypertension
Weight: being overweight increases risk of
heart attack and stroke
• Stress: avoid chronic stress
Cardiac Anatomy Quiz
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
Blood Pressure:
• Is the force exerted by the blood on the walls of blood vessels
• The instrument used to measure the blood pressure is the
mercury sphygmomanometer in conjunction with the
stethoscope
• There are many factors that affect the blood pressure:
• The diet: Excess salt raised the blood pressure, as the increased
levels of Na+ ions in the blood will result in the retention of
more water and increase the volume of the blood
• Waste products: like CO2 and lactic acid result in the
vasodilatation of arterioles, which increases the blood flow
and lowers the blood pressure
• Some disease conditions: cholesterol deposits narrow blood
vessels and result in raising the blood pressure
Sphygmomanometer
Stethoscope
• Autonomic Nervous control of blood Pressure:
Autonomic Nervous System
Sympathetic n.s.
• Increases the blood pressure
• Increases the heart rate
• Increases the respiratory rate
Parasympathetic n.s
• Autonomic Nervous regulation of the blood pressure:
High blood
pressure
Lower the
Blood pressure
The blood pressure receptors in
The Aorta and the carotid arteries
Will detect the high pressure and
signal the medulla oblongata
The Medulla Oblongata will stop
the action of the Sympathetic
Nervous System and stimulate
the action of the Parasympathetic
Nervous System
• Capillary Fluid Exchange
Blood Pressure
35 mm Hg
15 mm Hg
Venous Side
Arterial Side
25 mm Hg
Osmotic Pressure
Tissue Cells
Tissue Cells
The Lymphatic System
•
The lymphatic system is the system responsible for:
1.
Returning lymph (with its content of the plasma proteins that
have leaked to the tissues) back to the blood circulation
through the Thoracic duct that pours its contents into the right
atrium. This prevents a high osmotic pressure in the tissues,
which if happens will result in tissue swelling.
Defence through the production of lymphocytes and the
filtration of blood and lymph.
2.
•
The Lymphatic System has its own vessels, which join the
circulatory system when the thoracic duct pours its contents in
the right atrium.
The lymphatic system
in relation to the
circulatory system
The Lymphatic System
Lymph
Lymph vessels
Lymph organs
1. Lymph: is a clear, watery fluid, sometimes faintly yellow, lymph
removes certain proteins from the tissues as well as bacteria, the
bacteria will be filtered by the lymph nodes while the proteins
will return back to the blood when the lymph is poured through
the thoracic duct into the right atrium and mixes with the blood
2. Lymph vessels: A net work of vessels that have a dead end
beginnings, these vessels merge until they finally form the
thoracic duct that opens in the right atrium of the heart, and this
is where lymph mixes with the blood
3. Lymph organs
Primary Lymph organs
Secondary Lymph organs
1. Red bone marrow
2. Thymus gland
1. The Spleen
2. The lymph nodes
Red bone marrow: Is the site for manufacturing both
types of lymphocytes (B-lymphocytes and T-lymphocytes)
Thymus gland: Is the site where the maturation of the
T-lymphocytes take place
The spleen: has the following functions:
1. Acts as a reservoir for the storage of blood, and in case of
emergency it can contract and push more blood to the
circulation.
2. Is an organ designed to filter blood
3. Is involved in the production of lymphocytes