Lecture: Introduction of cardiovascular system

PPT : Lecture Introduction of cardiovascular system

1. Lecture 37: Introduction to Circulation Dr Shamshad

2. Identify the two divisions of circulation and track the pathway of the blood through both circulations. 2. Outline the various parts of circulation and identify the differences in structure, function, pressure and velocity of blood in different vessels. 3. Describe the physiological anatomy of the heart and identify its various specialized functional parts. OBJECTIVES Guyton & Hall Textbook of Physiology - 12th ed. P. 157-159 & 101-102

3. Veins- Deoxygenated blood towards heart Except pulmonary veins. Arteries- Oxygenated blood away from heart Except pulmonary arteries. Pumps blood through vessels Capillaries- location of internal respiration in all body tissues. Blood- Viscous transport medium. Heart Vascular system Overview of the Cardiovascular System

4. Supplies the tissues nutrients like: O 2 ,carbohydrates,aminoacids, fats, hormones, and immunological agents. Removes wastes products of tissue metabolism: CO 2 , lactic acids. Control blood flow to the skin & limbs: Heat loss to the environment :regulate body temperature. Body defense mechanisms : Transportation of antibodies/platelets/WBCs.. Functions of Circulatory System

5. Functions of Heart Generating blood pressure. Ensuring one-way blood flow: with help of valves Routing blood: separates pulmonary and systemic circulations. Regulating blood supply according to the need of the body [increase in exercise & pregnancy..].

6. P ulmonary Circuit Lesser circulation Systemic Circuit Greater/Peripheral circulation . DOUBLE PUMP

7. Function of blood vessels layers 1.Tunica intima Tunica media Tunica externa Reduces friction b/w vessel walls & blood. Controls vasoconstriction & vasodilation of the vessel. Protects, reinforces, & anchors the vessel to surrounding structures.

8. Types of blood vessels based on functions 1. Windkessel /Distensible vessels 3. Exchange vessels 4. Capacitance vessels 2. Resistance vessels 5. Shunts vessels

9. Windkessel /Distensible vessels Highly elastic vessels Ex : Aorta, pulmonary artery & other larger arteries. Function: Pressure & blood flow is pulsatile in nature due to effect of heart contraction and relaxation. Applied Aspects: Degeneration of the T.media lead to loss of Windkessel effect.

10. 2. Resistance vessels Vessels offer resistance to blood flow towards the capillaries Ex: Arterioles, metarterioles , and pre capillary sphincters Arterioles/peripheral resistance vessels. Function: Decrease the hydrostatic pressure within capillaries Resistance to blood flow is inversely proportional to the 4th power of radius of arterioles Show efficient myogenic control of their own radius.

11. 3. Exchange vessels Allow the exchange of gases and nutritive substances and others Single layer of endothelial cells Large surface area Millions of capillaries At rest only 25% active Vital organs posses dense capillary network Not controlled by nervous or metabolic factors Determined by pre-capillary sphincters

12. Structure of capillaries network Types Site Functions Continuous Common Allow passage of fluids & small solutes Fenestrated Kidneys More permeable to fluids & solutes Sinusoidal Liver Leaky capillaries that allow large molecules to pass b/w the blood & surrounding tissues

13. 4. Capacitance vessels Vessels which accommodated large vol of blood by change in their luminal shape without change in trans mural pressure Ex: Venules , venous compartments Function: Myogenic tone under control of sympathetic constrictor nerves Collapsible in nature.

14. 5. Shunts vessels Vessels bypass the capillaries network/ Aterio-venous shunts Ex : Skin ear lobes, palms, fingers, legs, toes lips… Walls are strong muscular coated Supplied by sympathetic nerves Function: Help rapid blood flow Exposure to heat dilates these vessels increase blood flow to veins and promote heat loss and body temp regulation.

15. Arteries Arterioles Capillaries Venules Veins Vessel Wall strong strong muscular thin & minute capillary pores thin thin Function transport blood under high pressure to the tissues act as control conduits through which blood is released into the capillaries. exchange fluid, nutrients.. b/w the blood & the interstitial fluid collect blood from the capillaries conduits for transport of blood from the venules back to the heart serve as a major reservoir of extra blood Mode of action blood flows at a high velocity capability of vastly altering blood flow in each tissue in response to its needs pressure very low

16. Pressure and Volume of blood in different blood vessels A B

17. Velocity and cross sectional areas of different blood vessels

18. Heart has 4 chambers Two thin atria separated by interatrial septum Two thick ventricles separated by interventrucular septum Atria: Functions : Produces low pressure when they contract. Acts as Blood reservoirs. Pumping 30% of venous return into the ventricles by contraction of the atrial muscle. locates SAN and AVN. Right atrium contains receptors of many cardiac reflexes Secretes Atrial Natriuretic Peptide (ANP) ,regulates ABP.

19. Ventricles: left : right ventricle ::3:1 thickness Structure: Has 4 groups of spirally arranged fibers That run from base to apex in three layers: inner, outer & intermediate layers. The middle is thick and transverse . A valve is attached to each ring to direct the flow of blood . Functions: Receive blood from atria and eject into great vessels.

20. Cardiac Muscle 5. Short branched cells 4. T-tubules larger & over z-discs 2. Uninucleate 3. Intercalated discs 1. Striated

21. Intercalated disc : The cell membranes fuse with one another to form permeable “communicating” junctions (gap junctions ). Function: Allow rapid diffusion of ions. Cardiac muscle: Syncytium of many heart muscle cells Function: when one cell gets excited, the action potential rapidly spreads to all of cardiac cells. Two syncytiums: Atrial syncytium [the walls of the two atria] Ventricular syncytium [ two ventricles]. Purpose of syncytiums: Allows the atria to contract a short time ahead of ventricular contraction, which is important for effectiveness of heart pumping.

22. Cardiac Valves Atrioventricular Valves Semilunar Valves Mitral/Bicuspid : Left atrium & left ventricle. Lt Ventricles & aorta Tricuspid : Rt atrium & Rt ventricle Rt Ventricles & pulmonary trunk Prevent backflow to the atria from ventricles during ventricular systole Prevent backflow into ventricles from gr vessels. Adapted to withstand extra stress. Prolapse is prevented by the chordae tendinae Tensioned by the papillary muscles Applied : weakness of papillary muscle lead to regurgitation.

23. The Conduction System of the Heart

24. SA N AVN Bundle of His/AV Bundle Purkinje fibers Site Superior Posterolateral wall of rt atrium. At junction of SVC with Rt atrium posterior wall of the right atrium immediately behind the tricuspid valve From AVN Continue in IV septum From terminal divisions of right and left brance of bundle of His Size 15*3*1mm 1*3*5mm 20*4mm 10-46*70-80Um Structure Primitive, highly vascular-cells abundant glycogen less mitochondria Contain P cells Same as SAN Divide into rt & lt branches Primitive, granular cytoplasm, multinucleated Rich in glycogen

25. SA N AVN Bundle of His/AV Bundle Purkinje fibers Innervation Rt Vagus Sympathetic nerve fibers from rt side Left vagus N Sympathetic supply from left Function Cardiac pacemaker Determine HR Pacemaker secondary to SAN connection between the atria and ventricles. Transmit fast impulse throughout ventricles Rate 60/min 40/min 25-40/min 25-40/min