Ch 47,48,49

Front 1

The cardiovascular or circulatory system is composed of the heart, blood vessels, and blood.

The general functions of the system are to carry oxygen, nutrients, hormones, antibodies, and other substances to all body cells and to remove waste products of cell metabolism (CO2 and others).

The efficiency of the system depends on the heart's ability to pump blood, the patency and functions of blood vessels, and the quality and quantity of blood.

Back 1

HEART
The heart is a hollow, muscular organ that functions as a 2-sided pump to circulate 5-6 L of blood through the body every minute.

CHAMBERS
The heart has four chambers: 2 atria and 2 ventricles. The right atria (RA) chambers receive deoxygenated blood from the body via the vena cava; and from veins and sinuses w/in the heart itself.

The left atria (LA) receive oxygenated blood from the lungs through the pulmonary veins.

Then ventricles are distributing chambers.

The right ventricle (RV) is small and thin walled b/c it contracts against minimal pressure; sends deoxygenated blood through the pulmonary circulation.

The left ventricle (LV) is more muscular and thick walled b/c it contracts against high pressure pumping oxygenated blood through the systemic circulation.

The septum is a muscular wall that separates the R and L sides of the heart.

Front 2

HEART LAYERS
Endocardium is the membrane lining the heart chambers. It is continuous with the endothelial lining of blood vessels entering and leaving the heart, and it covers the heart valves.

Myocardium is the strong muscular layer of the heart that provides the pumping power for circulation of the blood.

Epicardium is the outer, serous layer of the heart.

Pericardium is the fibroserous sac enclosing the heart.

Back 2

VALVES
Heart valves funtion to maintain the one-way flow of blood and prevent backflow.

Tricuspid valve separates the RA and RV.

Mitral valve separates the LA and LV.

Pulmonic valve separates the RV and pulmonary artery.

Aortic valve separates the LV and aorta.

Front 3

CONDUCTION SYSTEM
The heart contains special (myocardial) cells that can carry electrical impulses much more rapidly than ordinary muscle fibers.

This special conduction system consists of the sinoatrial (SA) node, the AV node, bundle of His, R and L bundle branches, and Purkinje fibers.

The SA node, the normal pacemaker of the heart, generates a burst of electrical energy approx. 60-100X/min under normal circumstances.

The electrical current flows over the heart in an orderly way to produce contraction of bothe atria, then both ventricles.

A unique characteristic of the heart is that any cell in any chamber can generate its own electrical impulse to contract. (automaticity)

The heart does not require nervous stimulation to contract, but the ANS does influence HR.

Back 3

BLOOD SUPPLY
The heart receives its blood supply from the coronary arteries.

Coronary arteries originate at the base of the aorta in the aortic cusps and fill during diastole (the resting or filling phase of the cardiac cycle).

Coronary arteries branch into smaller arteries that supply specific parts of the myocardium, w/o and overlapping supply from other arterial branches.

Artery-to-artery anastomoses occur b/w many adjacent vessels. These arteries may not supply sufficient blood if a major artery is occluded, by may dilate considerably as disease processes; resulting in collateral circulation which may provide a sufficient blood supply for myocardial function, at least during rest.

Front 4

BLOOD VESSELS
3 types: arteries, veins, and capillaries.

Arteries and veins both have 3 layers.

Layers
Intima, the inner lining, is composed of a layer of endothelial cells next to the blood (to provide a smooth surface for blood circulation) and an elastic layer that joins the media.
Media is the middle layer of muscle and elastic tissue.
Adventitia is the outer layer of connective tissue.

Cells
Blood vessel walls are composed of two types of cells, smooth muscle cells and endothelial cells.
Vascular smooth muscle functions to maintain blood pressure and blood flow, contracting and relaxing in response to stimuli. Overall, regulation of tone in vascular smooth muscle depends on the intracellular (IC)concentration of calcium ions-inc IC leads to inc vascular tone.

Endothelial cells, perform 2 extremely imp funct.
Structural - the cells act as a permeability barrier and regulate passage of molecules and cells across the blood vessel wall.
Metabolic - cells secrete opposing mediators that maintain a balance b/w bleeding and clotting of blood, constriction and dilation of blood vessels, and promotion and inhibition of vascular cell growth and inflammation.

Back 4

BLOOD VESSELS

Arteries and arterioles - contain a well-developed layer of smooth muscle (the media) and are sometimes called resistance vessels.
Their efficiency depends on their patency and ability to constrict or dilate in response to various stimuli. The degree of const. or dil. (vasomotor tone) determines peripheral vascular resistance, which is a major determinant of bp.

Veins and venules - have a thin media and valves that assist blood flow against gravity.
They are sometimes called capacitance vessels, b/c blood may accumulate in various parts of the venous system.
Their efficiency depends on patency, competency of valves, and the contraction and relaxation action of muscles around vains.


Capillaries - the smallest blood vessels, connect the arterial and venous segments of the circulation.
They consist of a single lay er of connected endothelial cells and a few smooth muscle cells.
Gases, nutrients, cells, and waste products are exchanged between blood and extracellular fluid across capillary walls.
The endothelial lining acts as a semipermeable membrane to regulate the exchange of plasma solutes w/EC fluid. Lipid-soluble materials diffuse directly through the capillary cell membrane; water and water-soluble materials enter and leave the capillary through the junctions or gaps b.w endothelial cells.

Lymphatic vessels - composed mainly of endothelium, parallel the veins and empty into the venous system.
They drain tissue fluid that has filtered through the endothelium of capillaries and venules from the plasma.
They then carry lymphocytes, large molecules of proteina dn fat, microoorganisms, and other materials to regional lymph nodes.

Front 5

BLOOD
Blood functions to nourish and oxygenate body cells, protect the body from invading microorganisms, and initiate hemostasis when a blood vessel is injured.

Functions
* Transport O2 to cells and CO2 from cells to lungs for removal from the body
* Transports absorbed food products from the GI tract to tissues; at the same time, carries metabolic wastes from tissues to the kidneys, skin, and lungs for excretion
* Transports hormones from endocrine glands to other parts of the body
* Transports leukocytes and antibodies to sites of injury, infection, and inflammation
* Assists in regulation of body temp by transferring heat produced by cell metabolism to the skin, where it can be released.
* Transports platelets to injured areas for hemostasis

Back 5

BLOOD COMPONENTS

PLASMA-55% of total blood volume and is more than 90% water.
* Serum albumin - helps maintain blood volume by exerting colloid osmotic pressure
*Fibrinogen - which is necessary for hemostasis
*Gamma globulin - which is necessary for defense against microorganisms
*Less than 1% antibodies, nutrients, metabolic wastes, resp. gases, enzymes, and inorganic salts

SOLID PARTICLES - or cells comprise approx. 45% of total blood volume; including RBC (erythrocytes), WBC (leukocytes), platelets (thrombocytes).

Bone Marrow - produces all RBC, 60-70% of WBC, and all platelets.
Lymphatic Tissues - produce 20-30% of WBC
Reticuloendothelial Tissues - (spleen, liver, lymph nodes) produce 4-8% of WBC.

Front 6

CARDIOVASCULAR DISORDERS

CV disorders, which are common causes of morbidity and mortality, often stem from blood vessel abnormalities.
Most vascular diseases result from the malfunction on endothelial cells or smooth muscle cells.
Dysfunctional endothelium is considered a major factor in atherosclerosis, acute coronary syndromes, hypertension, and thromboembolic disorders.
The main cause of endothelial dysfunction is injury to the bv wall from trauma or disease processes.
The injury alters the normal regulatory forces and leasd to vasospasm, thrombosis, growth of the intimal layer of the bv, rupture of atherosclerotic plaque, tissue ischemia and infarction, and dysrhythmias.
Pathologic changes in the strucure of the capillary and venular endothelium also result in the accumulation of excess fluid in interstitial space (edema), a common symptom of CV and other disorders.

CV disorders may involve any structure or function of the CV system. B/c the circulatory system is a closed system, a disorder in on part of the system eventually disturbs the function of all other parts.

Back 6

DRUG THERAPY USED FOR CV DISORDERS

CV disorders usually managed w/drug therapy include atherosclerosis, HF, cardiac dysrhythmias, ischemia, MI, hypertension, hypotension, and shock.
Periperhal vascular disease and valvular disease are usually managed surgically. Blood disorders that respond to drug therapy include certain types of anemia and coagulation disorders

The goal of drug therapy in CV disorders is to restore homeostasis or physiologic balance b/w opposing factors (eg, coagulant vs. anticoagulant, vasoconstriction vs. vasodilation).
CV drugs may be given to inc. or dec. CO, BP, and HR; to alter heart rhythem; to inc or dec blood clotting; to alter the quality of blood; and to dec. chest pain of cardiac origin.
In addition, these drugs may be given for palliation of symptoms w/o alteration of the underlying disease process.