Cardiovascular System

Basic Overview of Blood Vessels

MAIN FUNCTION: Transport O2, CO2, and nutrients around the body

• Arteries and arterioles (carry blood away from the heart)

• Veins and venules (carry blood towards the heart)

• Capillaries (where nutrients and O2 diffuse into your body tissues and cells)

The Chambers of the Heart

• Consists of 4 chambers• Pumping chambers are the

ventricles:- Right ventricle pumps blood to lungs- Left vent. pumps blood to rest of body

• Receiving chambers are the atria -right atrium receives O2

poor blood from the body- left atrium receives O2 rich

blood from lungs

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The Valves of the Heart

• Consists of 4 main valves to prevent the backflow of blood

• Semi-lunar valves are where blood is pumped out of the heart into major arteries

- Pulmonary semilunar valve (right side)- Aortic semilunar valve (left side)

• AV valves between atria and ventricles (tricuspid on right, mitral (aka bicuspid) on the left)

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Coronary Blood Vessels

• Coronary arteries supply myocardium (heart muscle) with oxygen and nutrients

• Heart attacks occur when a blockage occurs in a coronary artery

Anatomy of Blood VesselsContain three layers (tunics):• Tunica interna (intima) - inner layer

in contact with blood which contains the endothelium that lines the interior of all vessels

• Tunica media - muscular layer (smooth) responsible for vasodilation and vasoconstriction

• Tunica externa (adventitia) - mostly collagen (also elastin) to reinforce vessel (nerves and lymphatic vessels also invade this layer)

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Blood Pressure

Definition: The force exerted on a vessel wall by the bloodstream.

• Usually refers to pressure in arteries closest to the heart

• Pressure is higher during systole (contraction of ventricles) and lower during diastole (relexation of ventricles)

• Typical pressure 120/80 (systolic/diastolic)

Some Factors Affecting Blood Pressure

• Cardiac Output: amount of blood pumped from the ventricles per minute

• Peripheral Resistance: opposition to blood flow in blood vessels away from the heart (blood viscosity, blood vessel length and diameter affect resistance)

• Blood volume: amount of fluid in the blood stream at any given time

*Baroreceptors (sensory neurons) in arterial walls monitor blood pressure and send signals to the vasomotor centers in the medulla to regulate changes in BP (see figure 19.8 on pg. 727)

Hypertension (high blood pressure)

Why is it dangerous?• Heart must work harder to

pump against a greater resistance (can lead to heart failure - weakening of the left ventricle)

• More peripheral resistance damages endothelium (inner walls) of arteries and can damage small blood vessels in many organs (kidneys, eyes for ex.)

• Chronic HBP: 140/90 or greater

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Atherosclerosis

• Disease of the arterial wall caused by the formation of plaques

• Cholesterol is deposited by LDL particles in areas of damaged endothelium (1st step in plaque formation)

• When plaques rupture, blood clots form leading to blockage of small arteries

Lipoproteins and Cholesterol• Lipoproteins are molecules that

carry cholesterol to and from tissues (are produced in the liver)

• LDL (low density - BAD) particles carry cholesterol to the tissues (excess cholesterol ends up in arterial walls forming plaque)

• HDL (high density - GOOD) particles take cholesterol from tissues and blood vessels and bring it to the liver for disposal

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Conduction System of Heart

• SA node (pacemaker of heart) in right atrium

• Sends signals to AV node (also in right atrial wall)

• Signals travel down septum of heart via Bundle of His

• Signal then travels to ventricular walls via Purkinje fibers

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ECG (electrocardiogram) a.k.a EKG

• Shows electrical excitation of cardiac conduction system

• P wave - atrial depolarization

• QRS wave - ventricular depolarization

• T wave - ventricular repolarization

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The Blood

Blood Composition

• Blood consists of:1) Plasma - mostly

water, soluble proteins

2) Erythrocytes (red blood cells)

3) Buffy coat (Leukocytes (white blood cells), platelets)

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The Three Formed Elements

• Erythrocytes (Red Blood Cells) - transports O2 and CO2 in the blood

• Leukocytes (White Blood Cells) - help to defend the body against foreign invaders and cancer cells

• Platelets - function in hemostasis (coagulation or clotting of blood)

* All are produced during hematopoiesis in red bone marrow

Erythrocytes (RBC)• Carry respiratory gases (oxygen and CO2) in

the blood• Hemoglobin protein binds O2 (see figure 17.4)• Live about 120 days - old RBCs are broken

down in liver, spleen and bone marrow• Contribute to blood viscosity (more RBC

means “thicker” blood)• Erythropoietin (hormone released by

kidneys) stimulates RBC production or erythropoiesis (see figure 17.6 in book)

Blood antigens and antibodies• Antigens (also called agglutinogens) are

proteins on cell membranes that identify the cell as belonging to that person

• Antibodies, or agglutinins (proteins that can attach to antigens) also circulate in the blood

• A, B, and Rh antigens are used in blood typing and transfusions

• Transfusion of the wrong blood type results in agglutination (clumping of blood cells as they are attacked by antibodies) and hemolysis (destruction of erythrocytes)

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Table 17.4 pg 668

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