chapter 12: the cardiovascular system—the heart
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Chapter 12: The Cardiovascular System—The Heart. Function of the heart. Cells depend on interstitial fluid for survival The circulatory system balances the contents of the interstitial fluid (gas exchange, nutrients, waste, etc…) - PowerPoint PPT PresentationTRANSCRIPT
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