CHAPTER 12: THE CARDIOVASCULAR

SYSTEM—THE HEART

Cells depend on interstitial fluid for survival

The circulatory system balances the contents of the interstitial fluid (gas exchange, nutrients, waste, etc…)

The heart provides the mechanical “pumping” necessary for blood to circulate

Two circuits: Pulmonary (b/t heart & lungs) Systemic (b/t heart & body)

FUNCTION OF THE HEART

Size: 5” x 3.5” (~fist)Shape: blunt cone

Apex: pointed end Base: uppermost part

Location: center of thorax, behind the sternum (mediastinum)

4 Chambers Right atrium Right ventricle Left atrium Left ventricle

ANATOMY OF THE HEART

PERICARDIAL CAVITY (FIG. 12-2)

Pericardium encloses the heart (fist in balloon) and has 2 layersVisceral (epicardium): inner layer closest to the surface of the heart

Parietal: outer layerPericardial fluid

fills the cavity (lubricant)

Auricle: outer flap of deflated atriumCoronary Sulcus: groove between atria and ventriclesAnterior/Posterior Interventricular Sulci: boundary b/t

lft. and rt. ventricles

SURFACE ANATOMY OF THE HEART (FIG. 12-3)

Three layers Epicardium: outermost layer (serous) Myocardium: cardiac muscular layer; concentric wrapping Endocardium: innermost layer, continuous with vessel linings

THE HEART WALL (FIG. 12-4)

Interatrial Septum: separates left/right atriaInterventricular septum: separates left/right

ventriclesLeft/Right Atrioventricular (AV) valve

Bicuspid: left AV has 2 cusps, aka mitral valveTricuspid right AV has 3 cusps

Superior Vena Cava: blood from head, neck, upper limbs, and chest

Inferior Vena Cava: blood from rest of the trunk, viscera, and lower limbs

Coronary Sinus: opens into right atrium, receives blood from coronary veins

INTERNAL ANATOMY OF THE HEART

Chordae Tendineae: connects cusps to papillary muscles

Pulmonary semilunar valve: b/t right ventricle and pulmonary arteries

Aortic semilunar valve: b/t left ventricle and aorta

Aorta: start of systemic circuitPulmonary trunk: start of pulmonary circuitLeft/Right Pulmonary veins: receives

deoxygenated blood from lungs

INTERNAL ANATOMY OF THE HEART

Left/Right AVVentricles relaxed chordae tendineae loose & papillary muscles relaxed

Ventricles contracted chordae tendineae tense & papillary muscles contracted

Pulmonary/Aortic SemilunarNo need for supportive fibers since arterial walls do not contract

Cusps of valve act like a tripod

HEART VALVES (FIG. 12-6)

Abnormalities in valve shape can prevent the valves from closing completely

Regurgitation (backflow) of blood occurs creating a soft sound (heart murmur)

Treatments: most not necessary; surgery and medication

CLINICAL NOTE: MITRAL VALVE PROLAPSE

Coronary circulation: blood supply to the heart muscles

Coronary arteries Origin at the aorta (aortic

sinuses) Left (LCA) & Right (RCA)

Coronary veins Great, Middle & Small veins Drain into the coronary

sinus (right atrium)Myocardial infarctions

(heart attacks) result from blocks in these vessels

CARDIAC BLOOD SUPPLY

Contractile Cells99% of cardiac

muscle cellsAction potential in

cardiac muscle Rapid depolarization:

Na+ in The plateau:

extracellular Ca2+ in Repolarization: K+ and

Ca2+ out Longer contraction and

refractory than skeletal muscle

Conducting SystemAutomaticity of heart

contractions controlled by non-contracting cardiac muscle cells that initiate and distribute electrical impulses Sinoatrial (SA) &

Atrioventricular (AV) nodes contain nodal cells (pacemaker cells @ SA node)

AV bundle, bundle branches & Purkinje fibers contain conducting cells

THE HEARTBEAT

Bradycardia: slow heart rate (<60bpm)

Tachycardia: fast heart rate (>100 bpm)

Arrhythmias: abnormal patterns of cardiac activitySevere cases can be treated with defibrillator

CLINICAL NOTE: ABNORMAL HEART RATE

The period between the start of one heartbeat and the start of the next

Systole: chamber contracts

Diastole: chamber relaxes, fi lls with blood and prepares for next contraction

Since blood flows from high to low pressure, ventricles are ~70% fi lled before atrial systole

Heart Sounds: Lubb: AV valves close &

semilunar valves open Dupp: ventricles relax

and semilunar valves close

ECG (EKG): recording of electrical impulses in the heart P wave: atria depolarize QRS complex: ventricles

depolarize T wave: ventricles

repolarize

THE CARDIAC CYCLE

ELECTROCARDIOGRAM

Each one of the figures

represents an ECG pattern

displaying three types of

abnormal rhythms: Tachycardia,

Bradycardia, and Arrhythmia.  

 

Identify each.

ECG ANALYSIS