May 2, 2013 Warm-Up: Use 10 min. for quiet study. You abuse it, you LOSE it!

May 2, 2013

Warm-Up:

Use 10 min. for quiet study.

You abuse it, you LOSE it!

Cardiovascular System

(bicuspid)

Function: Transportation

• Transport medium: blood

• Destination: (oxygen, nutrients, cell wastes, hormones and other substances) carried to and from the cells

• The heart provides the force to move the blood around the body

• The cardiovascular system includes the heart, blood and blood vessels

Anatomy of the Heart

• Location – thoracic cavity; flanked by the lungs on each side

• Size – the same as a person’s fist

Covering and Walls

• 1. Pericardium – surrounds heart; secretes fluid to reduce friction as heart beats– Pericarditis – inflammation of pericardium

• 2. Myocardium – bundles of heart muscle; contractile layer

• 3. Endocardium – inner layer; forms the skeleton of the heart

Chambers of the Heart

• Four hollow chambers:– Two atria – receiving chambers

• Right and left atrium

– Two ventricles – lower chambers; thick walled pumps

• Right and left ventricles

• The heart is twisted – right ventricle is anterior; left ventricle forms the apex

Great Vessels

• The right side of the heart forms the pulmonary circuit– The right atrium receives blood from the vena

cava– The right ventricle pumps blood into the

pulmonary artery which carries blood to the lungs

– There, carbon dioxide is unloaded and oxygen is picked up

• The left side of the heart forms the systemic circuit– The left atrium receives blood from the

pulmonary vein (oxygenated blood-exception)– The left ventricle pumps blood into the aorta

• The aorta branches out to serve the tissues of the body

• Oxygen is delivered; carbon dioxide is picked up

Valves

• Allow blood to flow in only one direction

• Four valves:– 1. Bicuspid valve (mitral valve) – separates

left atrium from left ventricle– 2. Tricuspid valve – separates right atrium

from right ventricle– 3. Pulmonary semilunar valve – in

pulmonary artery– 4. Aortic semilunar valve – in aorta

Cardiac Circulation

• Right and left coronary arteries – supply oxygen and nutrients to the heart

• The coronary arteries branch from the base of the aorta and encircle the heart

• Angina pectoris – heart tissue is deprived of oxygen because of restricted blood flow in coronary arteries

• Myocardial infarction – heart attack; death of cardiac cells

Figure 12-15 Acute myocardial infarct, predominantly of the posterolateral left ventricle, demonstrated histochemically by a lack of staining by the triphenyltetrazolium chloride (TTC) stain in areas of necrosis (arrow). The staining defect is due to the enzyme leakage that follows cell death. Note the myocardial hemorrhage at one edge of the infarct that was associated with cardiac rupture, and the anterior scar (arrowhead), indicative of old infarct. (Specimen the oriented with the posterior wall at the

top.)

Downloaded from: Robbins & Cotran Pathologic Basis of Disease (on 25 April 2005 02:48 PM)

© 2005 Elsevier

Physiology of the Heart

• Cardiac muscle cells don’t require a nerve impulse to contract – they contract spontaneously and independently

Two types of control systems regulate heart activity:

• Extrinsic conduction:– autonomic nervous system

• sympathetic (fight or flight): speed up the heart by releasing epinephrine

• parasympathetic: slows the heart

• Intrinsic conduction – build into heart tissue– Sinoatrial node (SA) – located in right atrium

• Pacemaker – starts each heartbeat and sets the pace for the whole heart

– Atrioventricular node (AV) – located at junction of atria and ventricles

• Receives impulse from SA node, causing atria to contract

• Bundle of His and Purkinje fibers– Receive impulse from AV node, causing

ventricles to contract

• Impulse conduction through the heart:

• SA AV His Purkinje

Conduction Disorders

• Fibrillation– Rapid uncoordinated shuddering of heart

muscle– Major cause of death from heart attack

• Tachycardia – rapid heart rate– Greater than 100/min

• Bradycardia – slow heart rate– Slower than 60/min

Cardiac Cycle

• Cardiac cycle – events of one complete heartbeat – both atria and ventricles contract and then relax– Systole – ventricular contraction– Diastole – ventricular relaxation

• Heart rate – average 75 beats/min

• Heart Sounds – two can be heard during each cardiac cycle– “Lub” – closing of bicuspid and tricuspid

valves– “Dup” – closing of semilunar valves at end of

systole (ventricular contraction)

• Murmurs – abnormal heart sounds– May indicate valve problems

Blood Pressure

• The pressure the blood exerts against the internal walls of the large arteries near the heart.– The pressure drops throughout the pathway, reaching

zero at the vena cava.– Because pressure is low, veins depend on valves and

skeletal muscle to move blood along.– Blood flow depends on the stretchiness of the larger

arteries and their ability to contract and keep the pressure on the blood as it moves into circulation.

• Two arterial blood pressure measurements:– Systolic pressure – the peak of ventricular

contraction– Diastolic pressure – the ventricles relax

• Blood pressure is systolic/diastolic pressure and is usually measured at the brachial artery of the arm.

• Average blood pressure 120/80, but can vary considerably among individuals

• Hypotension – low blood pressure– Associated with physical conditioning; no ill

effects– Circulatory shock – usually caused by blood

loss; blood vessels do not contain enough blood

Hypertension

• High blood pressure (greater than 140/90)

• The heart pumps against increased resistance, usually caused by atherosclerosis

• No symptoms for 10-20 years; “silent killer”

• Strains the heart and damages blood vessels, roughing internal surfaces of vessels

• Hypertension is common in obese people because the total length of their blood vessels is greater than in thinner individuals, so the heart has to work harder.

Physiology of Circulation

• Vital Signs – pulse, blood pressure, respiratory rate and body temperature.

• Arterial Pulse – the alternating expansion and contraction of an artery that occurs with each beat of the left ventricle.– This pressure wave travels through the entire arterial

system.– Average pulse: 70-76 beats per minute.– Usually taken at the point where the radial artery

surfaces at the wrist.

Cardiovascular Pathology

• Varicose veins – valves in veins weaken and blood pools in veins, resulting in twisted and dilated veins

• Pulmonary embolism – clot detaches from vessel and lodges in the lungs

Atherosclerosis

• A narrowing of the arteries caused by thickened walls; this results in increased resistance to blood flow (hypertension)

• Fat and cholesterol collect on damaged tunica intima

• Most often affected:– Aorta– Coronary arteries

Atherosclerosis

• May be caused by:– Aging and/or lack of exercise– Carbon monoxide found in cigarette smoke– High fat and high cholesterol diet– Obesity– Genetic factors

Arteriosclerosis

• The end stage of atherosclerosis

• Vessels become hardened

• This rigidity results in hypertension.

Figure 11-9 Histologic features of atheromatous plaque in the coronary artery. A, Overall architecture demonstrating fibrous cap (F) and a central necrotic (largely lipid) core (C). The lumen (L) has been moderately narrowed. Note that a segment of the wall is plaque free (arrow). In this section, collagen has been stained blue (Masson's trichrome

stain). B, Higher-power photograph of a section of the plaque shown in A, stained for elastin (black), demonstrating that the internal and external elastic membranes are destroyed and the media of the artery is thinned under the most advanced plaque (arrow). C, Higher-magnification photomicrograph at the junction of the fibrous cap and core,

showing scattered inflammatory cells, calcification (broad arrow), and neovascularization (small arrows).

Downloaded from: Robbins & Cotran Pathologic Basis of Disease (on 14 November 2004 04:12 AM)

© 2004 Elsevier

Blood Vessels

• Blood circulates inside the blood vessels which form a closed transport system – vascular system.

• The aorta leaves the heart and branches into arteries; they branch into smaller arterioles which branch into smaller capillaries.

• Capillary beds drain into venules, which drain into larger and larger veins, which empty into the interior and superior vena cavae.

• Only the capillaries (which connect the smallest arterioles to the smallest venules) directly serve the needs of body cells – this is where exchange between blood and tissue cells takes place.

Microscopic Anatomy of Blood Vessels

• Tunica intima– Thin inner layer of blood vessel walls.

• Tunica media– Middle layer; thick in arteries, thin in veins.

• Tunica externa– Outer layer.

• The walls of arteries are thicker than the walls of veins.

• Capillaries are composed only of tunica intima.

Major Arteries of Systemic Circulation

• Aorta – largest vessel in the body.– Aortic arch – arches to the left; coronary

arteries are first branches.– Thoracic aorta – moves downward into

chest.– Abdominal aorta – moves into abdominal

cavity.

Major Veins of Systemic Circulation

• Veins are usually located more superficially than arteries.

• Superior vena cava – receives veins draining the head and neck.

• Inferior vena cava – receives veins draining lower body.

• Both drain into right atrium.

Capillary Exchange

• No substance has to move very far to enter or leave a cell.

• No cell is more than 5 cells away from a capillary.

• Substances move in and out of cells according to their concentration gradients (from higher to lower concentrations).