The cardiovascular system consists of the heart and blood vessels. The heart pumps blood through a closed system of arteries, veins, and capillaries. Blood carries oxygen, nutrients, hormones and more to tissues and removes waste. The three main components are the heart, blood, and blood vessels. The heart has four chambers and pumps blood through a double circulatory pathway. Blood contains red blood cells, white blood cells, platelets, and plasma which each have important functions. Blood vessels include arteries, veins and capillaries which transport blood and facilitate gas and nutrient exchange.

1. Cardiovascular System
Biology (Case 1)
Block 3
PBL G5

2. The Objectives :
Define the cardiovascular system and explain its general function
2- Identify the three components of the cardiovascular system .
3- Describe the Anatomy of the heart
4- Describe the histology of the heart
5- Identify the component of the blood and distinguish its different function .
6- Describe the function and the histology of the three types of blood vessels .
7- Explain the Physiology of Circulation .
8- Describe the circulation pathway .
9- Describe the cardiovascular diseases and explain the causes and the treatments.

3. Introduction to Cardiovascular System
The cardiovascular system is sometimes called the blood-vascular,
or simply the circulatory system.
It consists of the heart, which is a muscular pumping device, and a
closed system of vessels called arteries, veins, and capillaries. As
the name implies, blood contained in the circulatory system is
pumped by the heart around a closed circle or circuit of vessels as it
passes again and again through the various "circulations" of the
body.

4. Introduction to Cardiovascular System
As in the adult, survival of the developing embryo depends on the
circulation of blood to maintain homeostasis and a favorable
cellular environment. In response to this need, the cardiovascular
system makes its appearance early in development and reaches a
functional state long before any other major organ system.
Incredible as it seems, the primitive heart begins to beat regularly
early in the fourth week following fertilization.

5. The vital role of the cardiovascular system in maintaining
homeostasis depends on the continuous and controlled movement
of blood through the thousands of miles of capillaries that
permeate every tissue and reach every cell in the body.
It is in the microscopic capillaries that blood performs its ultimate
transport function. Nutrients and other essential materials pass
from capillary blood into fluids surrounding the cells as waste
products are removed.

6. Numerous control mechanisms help to regulate and integrate the
diverse functions and component parts of the cardiovascular system
in order to supply blood to specific body areas according to need.
These mechanisms ensure a constant internal environment
surrounding each body cell regardless of differing demands for
nutrients or production of waste products.

7. THE HEART ANATOMY
The heart weighs between 7 and 15 ounces
(200 to 425 grams) and is a little larger than the
size of your fist. By the end of a long life, a
person's heart may have beat (expanded and
contracted) more than 3.5 billion times. In fact,
each day, the average heart beats 100,000
times, pumping about 2,000 gallons (7,571
liters) of blood.

8. Your heart is located between your lungs in the
middle of your chest, behind and slightly to the left
of your breastbone (sternum). A double-layered
membrane called the pericardium surrounds your
heart like a sac. The outer layer of the pericardium
surrounds the roots of your heart's major blood
vessels and is attached by ligaments to your spinal
column, diaphragm, and other parts of your body.
The inner layer of the pericardium is attached to the
heart muscle. A coating of fluid separates the two
layers of membrane, letting the heart move as it
beats.

9. Your heart has 4 chambers. The upper
chambers are called the left and right atria,
and the lower chambers are called the left
and right ventricles. A wall of muscle called
the septum separates the left and right atria
and the left and right ventricles. The left
ventricle is the largest and strongest
chamber in your heart. The left ventricle's
chamber walls are only about a half-inch
thick, but they have enough force to push
blood through the aortic valve and into your
body.

10. Histology of the heart
The Heart Wall:
Consist of three-layered structure.
Inner layer = endocardium
Middle Layer = myocardium
Outer layer = epicardium (also called the pericardium)
A fundamental characteristic of the heart wall is that its thickness varies from location to
location

11. Epicardium ( Pericardium)
The outer layer of the heart and consists of a connective tissue region covered by a
mesothelium( simple squamous epithelium)on its outer surface.
Composed of connective tissue with nerves, vessels, adipocytes
Supports the blood vessels and nerves that supply the heart.
It Covers and protects the heart
The space between the linings is called the pericardial cavity

12. Myocardium
The largest of the three layers, and contains cardiac muscles
is thickest in the left ventricle, since the left ventricle is responsible for pumping blood
throughout the systemic circulation.
Consist of cardiac muscle cells (myocytes) :Different from smooth or skeletal muscle cells
due to placement of nuclei, cross striations, and intercalated disks

13. Intercalated disks
–Junctional complexes that contain fascia
adherens, desmosomes, and gap junction to
provide connection and communication.
–Bind myocytes and allow ion exchange to
facilitate electrical impulses to pass

14. Endocardium
The inner layer of the heart. blood vessels. and itself is layered.
By inner layer Simple squamous epithelium (Endothelium)
The middle layer is (Connective Tissue and Smooth Muscle)
The outer layer (Subendocardial Layer)

15. Cardiac Valves
Composed of connective tissue layers covered by
endothelium on each side;
3 layers
–Spongiosum: loose collagen
–Fibrosa: dense core of connective tissue
–Ventricularis: dense connective tissue with many
elastic and collagen fibers

16. Blood
● Blood is a fluid that circulates within the cardiovascular system
● It provide a vehicle for the distribution of respiratory gases , nutrients, water,
electrolytes,hormones and heat throughout the body.
● It is composed of cellular elements which are suspended in blood plasma.
● The cellular elements are :
1. Red blood cells.
2. White blood cells
3. Platelets

17. Red blood cells.
● Red blood cells are disked shaped anucleate
cells,and are 7-8 micrometer in diameter .
● The mature red cells lack nuclei and organelles.
● The cytoskeleton of red cells cause them to
extremely pliable and allow them to pass
through circulation.

18. ● Red blood cells have hemoglobin which is essential for transport of respiratory gases.
● In blood vessels the red blood cells pick up oxygen from inhaled air and carry it
through the bloodstream to all parts of the body.
● The cells need oxygen for metabolism ,which also creates carbon dioxide as a waste
product.Red blood cells pick up carbon dioxide and send it back to the lungs.
Function

19. White blood cells.
● White blood cells play an important role in immune
system , they defend the body from invaders.
● They have a cell nucleus and do not contain
hemoglobin.
● White blood cells are made inside the bone marrow
and stored in blood and lymphatic tissues.
● They flow through bloodstream to destroy viruses,
bacteria, and other foreign invaders that threaten
health.

20. ● They form two main groups both with defensive functions:
1. phagocytosis : which engulf and destroy bacteria and other
foreign matter
2. lymphocytes : the effector cell of the imune system .
● White blood cells have 5 types which develop in bone
marrow :
1. Neutrophills. (digest bacteria,fungi)
2. Monocytes (bacteria)
3. Eosinophills (bacteria,parasite,cancer cells)
4. Basophills (infection)
5. lymphocytes (antibodies)

21. Platlets
Platelets are needed to prevent and/or
stop bleeding. Not uncommonly,
trauma victims, whose platelets are
lost due to bleeding and related
processes, require platelet
transfusions.

22. Platelets transfusions are often critically
needed by:
Heart surgery patients also are frequently transfused with this product owing to
treatment-related loss, damage, and/or destruction of their platelets. Also patients battling
leukemia and other cancers – especially if they undergo transplantation with bone marrow
(or related stem cell sources) – will require transfusions to make up for their platelets that
are destroyed by chemotherapy and/or radiation. Because platelets last for only 5 days
after they are donated, a constant supply is vitally needed.

23. Blood plasma
Plasma is the liquid portion of blood. It's what
suspends red blood cells, platelets, and other cells
within our bloodstream. It also contains thousands
of different proteins and other substances
(electrolytes for example) that are needed for our
bodies to function normally.

24. Plasma transfusions are often critically
needed by:
● Burn and trauma victims
● Some organ transplant recipients
● People with certain rare blood disorders
Plasma donations can be frozen for up to one year prior to their transfusion into recipients.
They also may be used to create a variety of medicines – such as albumin, clotting factors,
and immune globulins – needed to treat patients with medical conditions including massive
blood loss, blood clotting abnormalities (such as hemophilia), and immunodeficiency
disorders.

25. Summary of blood

26. Blood Vessels
Blood vessels form a closed circuit of tubes that carry blood throughout the body.
The five main types of blood vessels are arteries, arterioles, capillaries, venules, and veins.
Except for capillaries, the walls of blood vessels have three layers or tunics.
The three structural layers of a generalized blood vessel from innermost to outermost are;
● The tunica interna (intima),
● Tunica media,
● Tunica externa (adventitia)
Aorta-Arteries-Arterioles-Capillaries-Venules-Veins-Vena Cava

27. Arteries
Arteries are muscular blood vessels that carry oxygenated blood away from the heart to the
body.
Arteries have a thick wall that consists of three layers.
The artery walls are thick so that when blood enters under pressure the walls can expand.
Aorta is the largest artery
Pulmonary artery is the only artery carrying deoxygenated blood

28. Arterioles
An arteriole is a small artery that extends and leads to capillaries. Arterioles have thick
smooth muscular walls.
These smooth muscles are able to contract (causing vessel constriction) and relax (causing
vessel dilation). This contracting and relaxing affects blood pressure; the higher number of
vessels dilated, the lower blood pressure will be.
Arterioles are just visible to the naked eye.

29. Tunica Intima:
● Forms the innermost lining, surrounding the lumen
● It is made of a layer of endothelium resting on basement membrane.
● The Endothelium is made of squamous epithelial cells and the basement membrane of
collagen.
● The basement membrane provides great tensile strength as well as the ability to
stretch and recoil
● Between tunica intima and tunica media is the Internal Elastic Lamina made of elastic
fibres.
Histological structure of Arteries.

30. Tunica Media:
● It is the middle layer made of muscle (smooth muscle cells) and connective tissue
layer(elastic fibres).
● It shows the greatest variation among different types of blood vessels
● Arteries have have a thick tunica media. Hence, due to plentiful elastic fibres they can
easily stretch in response to small increase in pressure.
● The smooth muscle cells regulate the diameter of the lumen

31. ● When the sympathetic stimulation increases, it causes arteries to contract; a term
called vasoconstriction
● When the sympathetic stimulation decreases, the smooth muscles relax causing the
arteries to dilate; a term known as vasodilation.
● Between the tunica media and tunica externa is a network of elastic fibres called
External Elastic Lamina.

32. Tunica Externa
● It is the outermost covering
consisting of elastic and
collagen fibres.
● It consist of numerous nerves
● It’s thickness is different in
different blood vessels.

33. Structure of Arterioles
● They have a thin tunica intima.
● The tunica media consist of 1 or 2 layers of smooth muscle cells
● The terminal of arterioles is called metarteriole which tapers towards capillary
junction.
● At the metarteriole-capillary junction, muscle cells form precapillary sphincter which
monitors blood flow into capillary.
● The tunica externa consist of connective tissue and many unmyelinated sympathetic
nerves.

34. Capillaries
● Capillaries connect arterioles to venules.
They allow the exchange of nutrients and
wastes between the blood and the tissue
cells.
● Despite their small size and easy
permeability, capillaries are quite strong.
● composed only of the tunica intima.

35. ● The thinness of the capillaries helps efficient exchange between the lumen of
the capillary and the surrounding tissue.
● Capillaries deliver nutrients and oxygen to tissues and remove the
byproducts of cellular reactions, such as carbon dioxide and water.
● Capillaries are much thinner than arteries and veins, because their walls are
made up of only a single layer of endothelial cells, the flat cells that line all
blood vessels.

36. There are three types of capillary:-
❖ continuous
❖ fenestrated
❖ discontinuous

37. Continuous capillary
Tight junctions of the endothelium to make
them highly impermeable to anything but the
smallest molecules.
Their pores are so tiny that only water and small
ions can pass through.

38. This type is found in areas of the body such as the central nervous
system, skeletal muscles, and skin.
Brain capillaries are continuous capillaries.
The nucleus of one cell bulges into the lumen of the capillary. The
nucleus of the other cell cannot be seen.

39. Fenestrated capillaries
● These are found in some tissues where there is extensive
molecular exchange with the blood such as the small
intestine, endocrine glands and the kidney. The
'fenestrations' are pores that will allow larger molecules
though.
● have numerous pores of various sizes. Small intestine
walls have fenestrated capillaries to allow digested food
molecules to be carried into the blood.

40. Discontinuous Capillaries
Wide pores in their cell walls and large spaces between cell layers to allow large
molecules to pass through.
Discontinuous capillaries are found primarily in the liver, which produces a
number of different proteins that need the larger space to pass through into the
body. so only found in the liver.

41. Sinusoids
are a special type of capillary that have a wide diameter. These are
found in the liver, spleen, lymph nodes, bone marrow and some
endocrine glands. They can be continuous, fenestrated, or
discontinuous.

42. A vein is a vessel that carries blood toward the heart. All of the veins except the
pulmonary veins contain deoxygenated blood. Small veins are called venules. Both arteries
and veins are macroscopic structures; that is, they can be seen without the aid of a
microscope
The average blood pressure in veins is considerably lower than in arteries.
VEINS

43. ● Veins function both as collectors and as reservoir vessels.
● They accommodate varying amounts of blood. The structural feature that allows them
to accommodate varying amounts of blood, with almost no change in blood
pressure,is their great ability to stretch.
● Transport blood away from capillaries
● Carry blood toward heart
● Have larger diameters
● Usually carry deoxygenated blood
Functions of Veins

44. Histological structure of veins
The walls of the larger blood vessels, the veins, have three layers
The innermost layer of a blood vessel is called the tunica intima.The tunica intima is made
up of endothelium that is continuous with the endothelium that lines the heart.The tunica
interna of veins is thinner than that of arteries Smooth lining with semilunar valves to ensure
one-way flow
The middle layer,the tunica media of veins is much thinner than in arteries, with relatively
little smooth muscle and elastic fibers.Allows constriction and dilation of vessels
The outermost layer is called the tunica adventitia.The tunica externa of veins is the thickest
layer and consists of collagen and elastic fibers.
Provides flexible support that resists collapse or injur

45. Type of Vessel Tunica Intima
(Endothelium)
Tunica Media
(Smooth Muscle;
Elastic Connective
Tissue)
Tunica Adventitia
(Fibrous Type of
Vessel Connective
Tissue)
Arteries Smooth lining Allows constriction
and dilation of
vessels; thicker than
in veins; muscle
innervated by
autonomic fibers
Provides flexible
support that resists
collapse or injury;
thicker than in veins;
thinner than tunica
media
Veins Smooth lining with
semilunar valves to
ensure one-way flow
Allows constriction
and dilation of
vessels; thinner than
in arteries; muscle
innervated by
autonomic fibers
Provides flexible
support that resists
collapse or injury;
thinner than in
arteries; thicker than
tunica media
Capillaries Makes up entire wall
of capillary; thinness
permits ease of
transport across
vessel wall
(Absent) (Absent)

47. Circulatory system : How it work?
The circulatory system consists of three independent systems that work together:
1 - The heart (cardiovascular).
2 - lungs (plumonary).
3 - arteries, veins, coronary and portal vessels (systemic).
*The system is responsible for the flow of blood, nutrients, oxygen and other gases, and as
well as hormones to and from cells.

48. Circulatory system : How it work?
1 - The heart : The heart is a muscular organ with four chambers, it pumps blood
through the network of arteries and veins.
2 - Lungs (Pulmonary) circulation: The circuit through the lungs where blood is
oxygenated.
3 - The systemic circulation: The network of veins, arteries and blood vessels, transports
oxygenated blood and nutrients from the heart,to the body's cells and then returns
deoxygenated blood back to the heart.

49. Circulatory system : How it work?
● Arteries: A- carry blood away from the heart.
B- carry oxygenated blood (pure blood).
● Veins: A- carry blood back to the heart.
B- carry deoxygenated blood (impure blood).

51. The Cardiovascular Pathways
➢ The blood flows in two circuits:
● The pulmonary circuit: takes blood from the heart to the lungs and back to the
heart.
● The systemic circuit: carries blood from the heart to all other organs, and then
returns blood to the heart.

52. FIRST: The Pulmonary Circuit
The steps:
1) Blood from all regions of the body collects in the right atrium and then passes
into the right ventricle (pumps the blood into the pulmonary trunk)
i) “The Pulmonary trunk is divided into the right and left pulmonary arteries”.
2) The arterioles take blood to the pulmonary capillaries (where CO2
is given off
and O2
is picked up)
3) Blood passes through the pulmonary venules which lead to the four pulmonary
veins that enter the left atrium in the heart.
★ Blood in the pulmonary arteries is O2
- poor.
★ Blood in the pulmonary veins is O2
- rich.

54. SECOND:
The Systemic Circuit

55. SECOND: The Systemic Circuit
The steps:
Left ventricle aorta common iliac artery femoral artery lower leg
capillaries lower leg veins femoral vein common iliac vein inferior
vena cavae right atrium.
★ The Superior and Inferior Venae Cavae both enter the right atrium.
★ The Superior and Inferior Venae Cavae return blood to the heart.

57. Disorders: Varicose Veins
Varicose veins are common in people who stand for long periods of time (for example,
dentists and hairdressers) and in obese (or pregnant) individuals , The common factors are the
pooling of blood in the feet and legs and inefficient venous return resulting from inactivity or
pressure on the veins.
What Causes Varicose Veins?
Varicose veins occur when your vein isn’t functioning properly. Veins have one-way valves
that prevent blood from flowing backwards. When these valves fail, blood begins to collect in
the vein rather than continuing toward your heart. Varicose veins often affect the legs because
they are the farthest from the heart and gravity makes it harder for the blood to flow upward.

58. Disorders: Varicose Veins
● Most varicose veins are only a cosmetic problem.
Occasionally they will cause pain, muscle
cramps, or itching and become a medical
problem. There are safe and effective ways to get
rid of them, so see your doctor but sometimes
there is A serious complication of varicose veins :
● Thrombophlebitis : inflammation of a vein that
results when a clot forms in a vessel with poor
circulation.

59. Hypertension
Hypertension, also known as high blood pressure, is when the pressure of the blood being
pumped through your arteries is higher than it should be. it often has no warning signs or
symptoms, and many people do not even know they have it.
Blood pressure is usually measured using a pressure cuff or an electronic device placed on
your upper arm
Types of Hypertension
•Primary/essential
Causes are indirect
❖ Smoking,obesity,hyperlipidemia and diabetes
•Secondary
Causes are direct
❖ Kidney disease and Aortic coarctation

60. What set hypertension
•Genetics - having family members with hypertension increases the likelihood that you
will too.
•Race - high blood pressure is more common in people with dark skin than in people with
pale skin.
•Age - your blood vessels become more rigid as you age, preventing them from opening as
effectively as when you were younger, which increases peripheral resistance.
• The most common risk factors include being overweight and inactive, eating a high salt
diet, and smoking.

61. How likely are you to become hypertensive?
•High blood pressure is more common in men during middle-age,
around 45 years, with women catching up after age 65.
•Worryingly, children can also become hypertensive for many of the
same reasons as adults - inactivity, unhealthy diet, and obesity
Effect on heart
Development of more muscles on the left ventricle[that pumps blood]
which may result to cardiac arrest and also left heart failure
Effect on vessels
1. Vessels become firm[not elastic any more]
2. Part of the artery wall starts to become weak leading to
hemorrhage

62. Treatments
•Lifestyle changes
1. Eating a healthy diet
2.Exercise
3.Reducing or better still quitting smoking
•Medication
1.Diuretics
2.Beta-blockers
3.Angiotensin-converting enzyme inhibitors, (ACE inhibitors)
4.Calcium channel blockers
5.Angiotensin II receptor blockers

63. Factors Affect Blood Pressure
A. Central factors, which are pertaining to the heart:
1. Cardiac output
2. Heart rate
B. Peripheral factors, which are pertaining to blood
and blood vessels:
3. Peripheral resistance

64. CENTRAL FACTOR
1.Cardiac Output
Blood pressure is directly proportional to cardiac
output. Whenever the cardiac output increases, the
Blood pressure is increased and when cardiac output
is less, the systolic pressure is reduced.

65. 2.Heart Rate
Moderate changes in heart rate do not affect arterial
blood pressure much. However, marked alteration in the
heart rate affects the blood pressure by altering cardiac output.

66. PERIPHERAL FACTORS
3.Peripheral Resistance
Peripheral resistance is the important factor, which maintains diastolic pressure.
Peripheral resistance is the resistance offered to the blood flow at the periphery.
Resistance is offered at arterioles, which are called the resistant vessels. When peripheral
resistance increases, diastolic pressure is increased and when peripheral resistance
decreases, the diastolic pressure is decreased.

67. 4- Blood Volume
Blood pressure is directly proportional to blood volume.
Blood volume maintains the blood pressure through the
venous return and cardiac output. If the blood volume
increases, there is an increase in venous return and
cardiac output, resulting in elevation of blood pressure

68. References
➢ Books:
● Human Biology Book. Sylvia S. Mader & Michael Windelspecht. 12th edition.
chapter 5.pages 91, 102 and 103.
● Essentials of human anatomy & physiology, Elaine N. Marieb, Eleventh Edition,
chapter 11 :The cardiovascular System, pages 361 and 373.
● Essential of medical physiology sixth edition Pages:604-605

69. ➢ Websites:
● http://www.bloodsource.org/Donate/What-is-Blood
● http://www.redcrossblood.org/learn-about-blood/blood-components/plasma
● http://www.healthline.com/health/varicose-veins
●
http://www.livescience.com/27585-human-body-system-circulation-infographic.htm
l
● http://www.majordifferences.com/2013/02/difference-between-artery-and-vein.html
#.WNpieG_yuUk
References