Anatomy

Anatomy & Physiology

Part 2: Introduction to the Cardiovascular System

© 2010 Leigh Robinson

Contents

• The 3 Main Divisions of the System• Structure of Vessels• Blood• Heart Structure & Function• Circulatory Problems

Some useful facts:

Fact: A typical person has 4-5 litres of blood.

Fact: Blood transports oxygen and nutrients to the body’s cells and takes the waste products away.

Fact: Blood also carries hormones and antibodies to fight invading germs and bacteria.

Fact: Blood gives us life!

3 Divisions of the Circulatory System

The Heart:• 2 Muscular pumps left and right ventricles• The ventricles have 2 reservoirs called

atria (left and right)• Each ventricle acts to serve different

circulations

3 Divisions of the Circulatory System: The Heart

The Right Ventricle:• The right ventricle moves de-oxygenated

blood into the pulmonary circulation. Blood enters

• Blood enters the network of capillaries in the lungs and through diffusion carbon dioxide is lost and oxygen acquired

• It then returns to the left atrium

3 Divisions of the Circulatory System: The Heart

The Left Ventricle:• The left ventricle is the pump responsible

for delivering blood into the systemic circulation where it carries nutrients and oxygen to the tissues

• An exchange of nutrients and oxygen for carbon dioxide and waste takes place with the waste rich blood returning to the right atrium

The Heart with Ventricles & Atrium


Blood Vessels:• An intricate network of hollow tubes that

transport blood throughout the body

Arteries:• These blood vessels transport blood away

from the heart• Arteries are thick, muscular walled structures

that are designed to accommodate the high flow and pressure exerted by the force of the heart

• The Aorta is a more elasticated tissue that allows for expansion.


Arterioles:• Smaller diameter blood vessels with thin

muscular walls that extend and branch from artery and leads to the capillaries. These are the primary site for muscular resistance

Capillaries:• Smallest of the blood vessels. Capillaries

connect arterioles and venules• The walls of the capillaries are only one cell

thick which enables the interchange of water, oxygen, carbon dioxide, nutrients and waste products from the blood and surrounding tissue


Venules:• Small blood vessel that drains de-oxygenated

blood from the capillary beds to return to the larger blood vessels called Veins.

• Many Venules join to form a vein

Veins:• These vessels transport blood towards the

heart.• The majority of the veins carry de-oxygenated

blood except for the Pulmonary Vein which carries oxygen rich blood from the lungs to the Atrium.

Structure of Vessels

The vessel wall is constructed of 3 layers:

• Tunica Adventia• Tunica Media• Tunica Intima


Tunica Adventitia:• The tunica adventitia is the strong outer

covering of the arteries and veins• It is composed of connective tissue as well

as collagen and elastic fibres• These fibres allow the arteries and veins to

stretch and prevent overexpansion due to pressure that is exerted on the walls by blood flow

Tunica Adventitia


Tunica Media:• The Tunica Media is the middle layer of the

walls of arteries and veins• It is composed of smooth muscle and

elasticated veins

Tunica Intima:• The Tunica Intima is the inner layer of arteries

and veins• In arteries this layer is composed of an elsatic

membrane lining and smooth endothelium that is covered by elastic tissues


Note: Veins do not contain the elastic membrane lining found in arteries. In some veins the Tunica Intima layer also contains valves

Blood

• Blood is made up of many different parts including 55% Plasma, 45% Components such as Red blood cells (Erythrocytes) and White Blood cells (Leucocytes)

• Red blood cells make up 99% of the blood cells with white cells the other 1%

• Blood platelets are also present and these are called Thrombocytes

Blood

Functions of the blood:• Transportation System• Maintains body temperature• Controls Ph• Removes toxins from the body• Regulates body fluid electrolytes

Transportation

• Dissolved gases (e.g. oxygen, carbon dioxide)

• Waste products of metabolism (e.g. water, urea)

• Hormones • Enzymes • Nutrients (such as glucose, amino acids,

micro-nutrients (vitamins & minerals), fatty acids, glycerol)

• Plasma proteins (associated with defence, such as blood-clotting and anti-bodies)

• Blood cells (incl. white blood cells 'leucocytes', and red blood cells 'erythrocytes')

Maintains Body Temperature

• Moves blood away from the surface to protect vital organs when cold

• Moves blood to the surface when hot to enable cooling to take place.

Controls PH

• The pH of blood must remain in the range 6.8 to 7.4, otherwise it begins to damage cells.

Removes toxins from the body

• The kidneys filter all of the blood in the body (approx. 8 pints), 36 times every 24 hours. Toxins removed from the blood by the kidneys leave the body in the urine. (Toxins also leave the body in the form of sweat.)

Regulation of Electrolytes

• Excess salt is removed from the body in urine, which may contain around 10g salt per day (such as in the cases of people on western diets containing more salt than the body requires)

Clotting Process

• Within 20 seconds of an injury to a blood vessel the process of sealing this injury site begins. This process is termed coagulation. The stages of coagulation are as follows:

• The blood vessel releases an enzyme called thrombokinase

• The released thrombokinase starts the conversion of an inactive enzyme prothrombin into thrombin

• Thrombin initiates a reaction to convert a another protein fibrinogen, which is present in plasma, to fibrin.

• Fibrin in turn forms a type of net over the injury site which then captures red blood cells and creates a seal. The clot then dries forming what we know as a scab

Heart Structure & Function

Heart Structure & Function

• The heart is a sort of upside down cone shape with blunted edges. On the outside there is a layer of fat, and across its surface are a network of veins and arteries, known as the coronary vessels, which keep the muscle supplied with blood.

• The heart's job is to pump blood around the body to where it is needed. Consequently, the heart is made up of cardiac muscle, which can contract often without tiring.

Heart Structure & Functions

• The left and right sides of the heart are separated by the septum, a wall of muscle and cardiac tissue.

• The valves, which stop the blood flowing back from the ventricles to the atria, are known as the atrio-ventricular (AV) valves. On the left are the Bicuspid and on the right the Tricuspid. There are also valves, which stop the blood from the arteries flowing back into the ventricles. These are called semi-lunar valves.

Circulatory Problems

Peripheral artery disease:• Peripheral artery disease (PAD) is a

condition where fatty deposits build up in the inner linings of the artery walls. The narrowing restricts blood circulation, mainly in arteries leading to the kidneys, stomach, arms, legs and feet.

• Early symptoms are cramping, fatigue or numbness in the legs and buttocks that occurs during moderate exercise or simple walking. The cramping usually stops as and when the person stands still. This is called "claudication."

• Treatment for these patients include the following:

• Diabetic control• Low cholesterol diet• Blood pressure medication• Angioplasty to widen the narrowed arteries• In severe cases the patient may have to

under go a bypass operation so blood can pass freely to the affected part

Circulatory Problems

• Those with the fatty deposits also run a higher risk of developing a stroke or a myocardial infarct, this can lead to death. People at risk of PAD are those that have Diabetes, Hypertension, High Cholesterol and smokers.

Treatment for patients

• Diabetic control• Low cholesterol diet• Blood pressure medication• Angioplasty to widen the narrowed arteries• In severe cases the patient may have to

under go a bypass operation so blood can pass freely to the affected part

Questions, Problems, Queries?

Anatomy

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