Heart

• Pulmonary Circuit


  the right side of the heart receives oxygen-depleted blood from body tissues + then pumps this blood to the lungs to pick up oxygen + dispel CO2

  the blood vessels that carry blood to + from the lungs form the pulmonary circuit

  
• Systemic Circuit


  the left side of the heart receives the oxygenated blood returning from the lungs + pumps this blood thru out the body to supply oxygen + nutrients to body tissues

  the blood vessels that carry blood to + from all body tissues form the systemic circuit
• Location of Heart

  enclosed w in the mediastinum, the medial cavity of the thorax, the heart extends obliquely for 12-14 cm from the 2nd rib to the 5th intercostal space

  as it rests on the superior surface of the diaphragm, the heart lies anterior to the vertebral column + posterior to the sternum
• Pericardium


  the heart is enclosed in a double-walled sac = pericardium
• Fibrous Pericardium


  the loosely fitting part of this sac = fibrous pericardium

  this tough, dense connective tissue:

  protects the heart

  anchors it to surrounding structures

  prevents overfilling of the heart w blood
• Serous Pericardium


  deep to the fibrous pericardium = serous pericardium

  = a thin, slippery, two-layer serous membrane that forms a closed sac around the heart
• Parietal Layer of the Serous Pericardium

  its parietal layer lines the internal surface ofthe fibrous pericardium

  at the superior margin of the heart, the parietal layer attaches to the large arteries exiting the heart + then turn inferiorly + cont over the external heart surface as the visceral layer (epicardium) = integral part of the heart wall
• Pericardial Cavity

  between the parietal + visceral layers is the slit-like pericardial cavity, which contains a film of serous fluid

  the serous membranes, lubricated by the fluid, glide smoothly past one another, allowing the mobile heart to work in a relatively friction-free environment
• Superficial Layer of the Heart Wall

  the superificial epicardium = visceral layer of the serous pericardium

  it is often infiltrated w fat, esp in older ppl
• Medial Layer of the Heart Wall

  the medial layer, the myocardium (muscle layer)= composed mainly of cardiac muscle + forms the bulk of the heart

  = layer that contracts
• Myocardium - Branching of Muscle Cells

  the branching cardiac muscles r tethered to ne another by criscrossing connective tissue fibres + arranged in spiral/circular bundles

  these interlacing bundles effectively link all parts of the heart together + create effective pumping contractions
• Myocardium - Fibrous Cardiac Skeleton

  the connective tissue fires form a dense network, the fibrous cardaic skeleton, that reinforces the myocardium internally + anchors the cardaic muscle fibres

  this network of collagen + elastic fibres is thicker in some areas than others

  it constructs ropelike rings that provide additional support where the great vessels issue from the heart + atound the heart valves

  w out this support, the vessels + valves might eventually become stretched cos of the continous stress of blood pulsing thru them
• Purpose of Fibrous Cardiac Skeleton

  cos connective tissue isn't electrically excitable, the cardiax skeleton allow action potentials to spread only via specific pathways in the heart
• Interior Layer of the Heart Wall

  the endocardium = sheet of squamous epithelium resting on a thin connective tissue layer

  located on the inner myocardial surface, it lines the heart chambers + covers the fibrous skeleton of the valves

  the endocardium is continous w the endothelial linings of the blood vessels leaving + entering the heart
• Layers of the Heart

  structure of the heart wall

  
• Location of Heart Diagram

  boom shakka boom boom

  
• Structure of Heart


  heart

  
• The 4 Chambers of the Heart


  2 superior atria + 2 inferior ventricles

  the internal partition that divides the heart longitudinally = interatrial septum, where it separates the atria

  interventricular spetum - separates the ventricles

  right ventricle forms most of the anterior surface

  left ventricle dominates the inferoposterior aspect + forms the heart apex
• Atria


  atria = receiving chambers of blood returning to the heart from the circulation

  relatively small, thin-walled chambers cos they need to contract only minimally to push blood into the ventricles

  contribute lil to the propulsive pumping activity of the heart
• Functions of the Right Atrium


  blood enters the right atrium via 3 veins:

  superior vena cava - returns blood from body regions superior to the diaphragm

  inferior vena cava - returns bllod from body areas below the diaphragm

  coronary sinus - collects blood draining from myocardium
• Functions of the Left Atrium


  4 pulonary veins enter the left atrium, which makes up most of the heart's base

  these veins transport blood from the lungs back to the heart
• Ventricles as Discharging Chambers


  together the ventricles make up most of the vol of the heart

  the papillary muscles = muscular bundle, plays a vital role in valve function

  their cardiac walls r much larger than the atrial walls, reflecting the difference in function between the atria + ventricles

  right ventricle pumps blood into pulmonary trunl, which routes blood to lungs

  left ventricle ejects blood into aorta