CARDIOVASCULAR SYSTEM
1.Introduction
1.1.Part of the circulatory system along w/ lymphatic system
2.2.Composed of the heart and blood vessels
3.3.Functions: move blood to
- 1.deliver nutrients and oxygen
- 2.remove waste
2.THE HEART
1.General
- 1.Apex--inferior pointed end, Base--superior flattened end,
- 2.located in thoracic cavity between lungs, size of clenched fist
4.2.Coverings
- 1.parietal pericardium (pericardial sac)--composed DCT and SS epithelium, protects and anchors heart
- 2.visceral pericardium (epicardium)--continuation of SS epithelium that attaches to heart
- 3.pericardial cavity--forms between two layers, contains fluid that lubricates heart
5.3.Heart Wall
- 1.epicardium --protects heart, contains fatty deposits
- 2.myocardium --cardiac muscle tissue interwoven w/ CT, propels blood
- 3.endocardium --smooth, white membrane that lines internal surfaces of heart and blood vessels
6.4.Heart Chambers
- 1.atria --receive blood, pump it to next chamber
- 1.pectinate muscles --ridges of muscle in atria
- 2.internal septum --separates atria, contains fossa ovalis
- 3.vena cava and pulmonary veins
- 2.ventricles --provide force to push blood out of heart, myocardium is much thicker than atria's
- 1.trabeculae carnae --muscle ridges lining surface
- 2.papillary muscles
- 3.interventricular septum --separates ventricles
- 4.pulmonary trunk and aorta
7.5.Heart Valves
- 1.Atrioventricular valves --between atria and ventricles
- 1.tricuspid valve --between rt. atrium and rt. ventricle, formed by three cusps that point downward into ventricle
- 2.bicuspid or mitral valve --between lt. atrium and lt. ventricle, formed by two cusps
- 3.chordae tendinea --strands of CT that connect cusps to papillary muscles, anchor valves and prevent them from everting as blood pushes against them
- 2.Semilunar valves
- 1.pulmonary valve --DCT. between rt. ventricle and pulmonary trunk, composed of three halfmoon cusps that resemble bowls
- 2.aortic valve --between lt. ventricle and aorta
8.6.Blood Flow Through the Heart
9.7.Blood Supply to the Heart
10.8.Heart Physiology
- 1.cardiac cycle --contraction of both atria followed by contraction of both ventricles is one cycle
- 1.systole --state of contraction
- 2.diastole --state of relaxation
- 2.heart sounds --"lub-dup" sounds produced by blood turbulence as valves open and close, lub indicates closing AV valve, dup indicates closing SL valve, helpful in diagnosing heart problems
- 3.heart conduction system
- 1.cardiac muscle tissue have inherent ability to contract w/o nervous input
- 2.sinoatrial (SA) node --mass of cells in wall of rt. atrium, act as pacemaker as it initiates each cardiac cycle by sending out electrical signal causing atria to contract and stimulating AV node
- 3.atrioventricular (AV) node --second mass of cells near bottom of interatrial septum, sends signal down AV bundle that extends down interventricular septum to Purkinje fibers causing ventricles to contract
- 4.delay in signal as it travels down AV bundles allows time for atria to relax and collect blood, cycle starts aver again, 100,000 times each day
- 4.electrocardiogram (ECG of EKG)
- 1.measures electrical activity of heart as currents flow though body and records it in relation to time
- 2.Normal wave pattern: P, QRS, and T waves
(1)(1)P wave - SA node fires and depolarizes atria
(2)(2)QRS complex - ventricular depolarization, large due to muscle mass
(3)(3)T wave - repolarization of ventricles
- 3.useful tool for detecting heart problems
- 5.cardiac output
- 1.measurable value representing heart activity
- 2.heart rate - duration of each cardiac cycle, how fast
- 3.stroke volume -volume ejected by ventricles
- 4.cardiac output = H.R. x S.V. (normal 75 bpm x 70 ml)
- 5.Starling's law of the heart -strength of ventricular contraction is determined by stretch of muscles when filling w/ blood, more stretch = more strength
- 6.regulation of heart activity
- 1.autonomic control via medulla oblongata reflex center
(1)(1)parasympathetic -slow heart by releasing ACh
(2)(2)sympathetic - increase heart rate by releasing norepinephrine
- 2.baroreceptors -detect changes in blood pressure, located in aorta and carotid artery
- 3.BLOOD VESSELS
1.1.Arteries and Arterioles
- 1.arteries carry blood away from heart, branch into arterioles
- 2.structure
- 1.lumen - hollow interior
- 2.tunica intima - innermost layer, endothelium and CT
- 3.tunica media - smooth muscle and elastic fibers
- 4.tunica adventitia - thin layer of CT to anchor to surroundings
- 3.properties
- 1.contractibility and elasticity provided by t. media
- 2.stimulus from sympathetic nervous system, regulates blood pressure (vasoconstriction and dilation)
2.2.Capillaries
- 1.smallest blood vessels, less than .01 mm diameter, 1 RBC at a time
- 2.wall of endothelium allows for diffusion of oxygen and nutrients into cells and removal of wastes, leaky in places
- 3.connect arterioles w/ venules via capillary beds which may contain between 10 - 100 capillaries
- 4.precapillary sphincter - band of smooth muscle that controls blood flow into cap. bed
3.3.Venules and veins
- 1.carry blood towards the heart, usually deoxygenated
- 2.composed of same three layers as arteries, only thinner w/ less elasticity, larger lumen
- 3.65% of blood contained in veins, under low pressure
- 4.contain one way valves made of t. intima
4.4.Blood Pressure
- 1.contraction of ventricles causes blood to exert force on walls of vessels
- 2.arterial BP - highest in aorta
- 1.systolic pressure - peak pressure at ventricular contraction, 120 mm Hg normal
- 2.diastolic pressure - lowest pressure at ventricular relaxation, 70 - 80 mm Hg normal
- 3.sphygmonmanometer - blood pressure cuff
- 3.factors affecting BP
- 1.cardiac output = heart rate x stroke volume
- 2.peripheral resistance
(1)(1)diameter of blood vessels (clogged arteries?)
(2)(2)viscosity of blood ( 30W or 60Woil?)
- 3.blood volume
(1)(1)plasma volume - normal 5 liters
(2)(2)hematocrit - blood cells
- 4.regulation of BP
- 1.nervous - autonomic fibers control HR, tunica media of arterioles, stimulated by baroreceptors and chemoreceptors in major vessels
- 2.hormonal - epinephrine and nor epinephrine8 cardiac output, 8per. resistance; ADH 8 water retention in kidneys
- 3.kidney control - main long term control for BP; control water retention, angiotensin produces vasoconstriction, aldosterone causes reabsorption of Na+