Transcript Cardiovascular System

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).