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Identify the two divisions of circulation and track the pathway of the blood through both circulations. Outline the various parts of circulation and identify the differences in structure, function, pressure and velocity of blood in different vessels. Describe the physiological anatomy of the heart and identify its various specialized functional parts. OBJECTIVES

Circulatory System Function:

Circulatory System Function Move circulatory fluid (blood) around body Gas Transport Nutrient Transport Excretory Product Transport Cell Signal Transport Distribute secretions of endocrine glands, Production/Synthesis Hydraulic Force Heat Conductance Immunity

Functions of the Heart:

Functions of the Heart Generating blood pressure Routing blood : separates pulmonary and systemic circulations Ensuring one-way blood flow: valves Regulating blood supply -Changes in contraction rate and force match blood delivery to changing metabolic needs

Overview of the Cardiovascular System:

Overview of the Cardiovascular System 3. basic components: 1. Heart serves as the pump that imparts pressure 2. B lood vessels serve as the passageways 3. Blood is the transport medium

Pathway of Blood:

Pathway of Blood Pulmonary Circuit Blood flow between the lungs and heart Supplied by the Right side of the heart Systemic Circuit Blood flow between the rest of the body and heart Supplied by the Left side of the heart


Divisions of the circulation figure “8.” Systemic circulation / greater circulation / peripheral circulation.


Divisions of the circulation


Human life span, heart contracts about 3 billion times , heart beats about 100,000 times every day Within 3 weeks after conception, the heart of the developing embryo starts to function . First organ to become functional. At this time the human embryo is only a few mm long, about the size of a capital letter on this page


1.Muscular organ (pump) situated in middle slightly to left side of the thoracic cavity partly behind the sternum. 2.Closed fist. 12 cm long, 9 cm, 6 cm.) thick, 300 g males 250 g females The Heart Cardiology ( cardio= heart; -logy = study of).


The heart is enclosed into a fibrous sac called “pericardium” which is formed of 2 layers: 1) A superficial, fibrous, layer which lines the thorathic cavity. 2) A serous layer which is a double ( parietal +visceral) the latter covers the outer surface of the heart and known as epicardium .


Functions of pericardium : Prevent sudden overdistension of the heart. Support the heart and prevents pulling of the great vessels. Accumulation of fluid in the pericardial sac is called “pericardial effusion”. This limits expansion of the hear to receive blood.


Functional anatomy Structure of Blood Vessel Walls except the smallest consist of three layers: 1.Tunica intima reduces friction between the vessel walls and blood; 2. Tunica media controls vasoconstriction and vasodilation of the vessel; 3. Tunica externa protects, reinforces, and anchors the vessel to surrounding structures

Functional classification of blood vessels :

Functional classification of blood vessels Distributing   vessels, including arteries;   Resistance   vessels, including arterioles and precapillary sphincters; Exchange   vessels, including capillaries, sinusoids, and postcapillary venules ;   Reservoir ( capacitance)   vessels, including larger venules and veins; and   Shunts , including various types of anastomoses

Venous return :

Venous return is aided by both structural modifications and functional adaptations. Structural -Large lumen -Valves - present mostly in extremities, none in ventral body cavity 2. Functional -Respiratory Pump -Muscular Pump -Smooth muscle layer under sympathetic control


CLASSIFICATION OF ARTEIES Elastic - e.g. (Aorta & its Major branches) Muscular -e.g.(Renal, Testicular, Radial, Tibial etc.) Arterioles (<0.1 mm) Terminal arterioles Meta-arterioles Thoroughfare channel/ preferred Capillaries (5-8 micron)




Aorta 33 cm/sec – Capill , 0.3 mm/sec. length 0.3 -1 mm - blood remains1 -3 sec..


Basic Principles of Circulatory Function Rate of blood flow to each tissue is controlled in relation to tissue need. CO is controlled = sum of all the local tissue flows. BP regulation is independent of either local blood flow or CO control BP for entire CVS is maintained by tension at the end of the arteriol es

Functional Anatomy of the Heart Chambers:

Functional Anatomy of the Heart Chambers 4 chambers 2 Atria 2 Ventricles 2 systems Pulmonary Systemic A trial and ventricular types of muscle contract in much the same way as skeletal muscle, except that the duration of contraction is much longer .


The inside cavity of the heart is lined by the endocardium . An intermediate muscular layer lying between the epicardium and the endocardium known as the myocardium . The myocardium is composed of three major types of cardiac muscle fibers, they are: Nodal fibers, Specialized conducting fibers and Contractile muscle fibers.


figure 8


The specialized excitatory and conductive fibers, contract weaker because they contain few contractile fibrils; instead they, produce automatic rhythmical electrical discharge in the form of action potentials or Conduct the action potentials through the heart. SPECIALIZED FIBER s

Functional Anatomy of the Heart Cardiac Muscle:

Functional Anatomy of the Heart Cardiac Muscle Characteristics Striated Short branched cells Uninucleate Intercalated discs T-tubules larger and over z-discs

Functional Anatomy of the Heart Valves:

Functional Anatomy of the Heart Valves Function is to prevent backflow Atrioventricular Valves Prevent backflow to the atria Prolapse is prevented by the chordae tendinae Tensioned by the papillary muscles Semilunar Valves Prevent backflow into ventricles

Conduction System of the Heart:

Conduction System of the Heart Conduction pathways Depolarization spreads throughout the heart very rapidly facilitating a coordinated contraction pattern Intercalated disks Form junctions between adjacent cardiac muscle fibers Contain a high concentration of gap junctions for rapid transmission of the action potential

Myocardial Physiology Contractile Cells:

Myocardial Physiology Contractile Cells Plateau phase prevents summation due to the elongated refractory period No summation capacity = no tetanus (Which would be fatal)

Myocardial Physiology Autorhythmic Cells (Pacemaker Cells):

Myocardial Physiology Autorhythmic Cells (Pacemaker Cells) Altering Activity of Pacemaker Cells Sympathetic activity NE and E increase I f channel activity Binds to β 1 adrenergic receptors which activate cAMP and increase I f channel open time Causes more rapid pacemaker potential and faster rate of action potentials Sympathetic Activity Summary: increased chronotropic effects  heart rate increased dromotropic effects  conduction of APs increased inotropic effects  contractility

Myocardial Physiology Autorhythmic Cells (Pacemaker Cells):

Myocardial Physiology Autorhythmic Cells (Pacemaker Cells) Altering Activity of Pacemaker Cells Parasympathetic activity ACh binds to muscarinic receptors Increases K + permeability and decreases Ca 2+ permeability = hyperpolarizing the membrane Longer time to threshold = slower rate of action potentials Parasympathetic Activity Summary: decreased chronotropic effects  heart rate decreased dromotropic effects  conduction of APs decreased inotropic effects  contractility

Aging and the CVS:

Aging and the CVS Changes occur in the blood, heart, and BVs Blood changes – HCT ; thrombi and emboli form more easily; blood pools in leg Heart changes – efficiency and elasticity; atherosclerosis of coronary vessels; scar tissue forms Blood vessel changes – loss of elasticity; calcium deposits damage vessel walls Gradual changes in heart function, minor under resting condition, more significant during exercise Hypertrophy of L ventricle Maximum heart rate decreases tendency for v alves to function abnormally and arrhythmias to occur O 2 consumption required to pump same amount of blood

Artificial Heart:

Chapter 18, Cardiovascular System 40 Artificial Heart



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