Cardiovascular System: Heart Anatomy and Physiology, Study notes of Anatomy

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CARDIOVASCULAR SYSTEM

 (^) Composed of blood, heart & blood vessels  Heart beats 100,000 times every day  Average adult – 100,000 km blood vessels  (^) CVS – ensures a continuous flow of blood to all body cells, and subjected to continuous physiological adjustments to maintain adequate blood supply

Structure/ Anatomy of the heart External anatomy Pericardium  Outermost layer/ membrane that surrounds & protects the heart  (^) Confines heart to its position in mediastenum  Consists of 2 sacs Outer sac – fibrous pericardium Inner sac – serous pericardium

Fibrous Pericardium

• (^) Composed of fibrous tissue – tough, inelastic, dense irregular connective tissue
• (^) Continues/ attaches to connective tissues of blood vessels entering & leaving heart (tunica adventitia)
• (^) Apex partly fused with diaphragm
• (^) Protects & prevents over-distension of heart Serous Pericardium
• (^) Membrane formed by single layer of endothelial cells
• Forms double layer around heart
• (^) Outer layer – parietal layer, fused with fibrous pericardium
• (^) Inner layer – visceral layer; also called epicardium – firmly attached to myocardium
• (^) Pericardial fluid – 20 ml lubricating fluid lies between the layers – heart beats without rubbing against fibrous pericardium Space between the layers – pericardial space/ pericardial cavity

• Makes up approximately 95% of heart wall
• (^) Striated, involuntary muscle
• (^) Intercalated discs/ branches – give appearance of sheet Enables whole heart to contract in coordinated & efficient manner
• Thick at apex, thin at base
• Specialised muscle cells in wall of atria secrete ANP Endocardium
• (^) Lines the chamber & valves of the heart
• Thin, smooth membrane to ensure smooth flow of blood through heart
• Consists of flattened epithelial cells
• (^) Continuous with endothelial lining of large blood vessels attached to heart

Right Ventricle

• Inside contains a series of ridges formed by raised bundles of cardiac muscle fibers – trabeculae carneae
• Cusps of tricuspid valve connected to tendon like cords – chordae tendinae, connected to cone-shaped trabecuale carneae called papillary muscles
• Right ventricle is separated from left ventricle – interventricular septum
• (^) Blood passes from right ventricle into large artery pulmonary trunk through pulmonary valve
• (^) Pulmonary trunk divides into right & left pulmonary arteries – carries blood to lungs

 Walls of ventricles are thicker than atria  (^) Right side has much smaller workload – pumps blood to shorter distance to lungs at low pressure  Left ventricle works much harder than Right ventricle  In addition to cardiac muscle tissue, heart wall also contains dense connective tissue i.e. network of fine fibers called fibrous skeleton of heart  (^) It surrounds valves of heart, fuse with one another  Prevent overstretching of valves as blood passes through them  Electric insulator between atria & ventricles

Heart Valves  (^) Valves open & close in response to pressure changes as the heart contracts & relaxes  Ensure one-way flow of blood  2 types of heart valves

1. Atrioventricular valves (AV valves)
2. Semilunar valves Atrioventricular Valves (AV valves) _3. Tricuspid valve
3. Bicuspid valve/ mitral valve_

• (^) When AV valves open – ventricles relaxed – blood moves from high pressure in atria to lower pressure in ventricles
• When ventricles relax – papillary muscles relax – valves closed