all about the heart

• Right side of the heart takes in oxygen-poor blood from body tissues and then pumps this blood to the lungs to pick up oxygen and get rid of carbon dioxide
• left side of the heart receives oxygenated blood and then pumps it through the body to supply tissues with nutrients and oxygen
• heart is about the size of a fist, hallow, cone-shaped and has a mass of 250-350 grams
• the heart rests on the superior surface of the diaphragm, the hearts lies anterior to the vertebral column and posterior to the sternum
• pericardium: double walled sac that encloses the heart
• fibrous pericardium: dense, connective tissue layer that loosely fits:

  • protects the heart
  • anchors it to surrounding structures
  • prevents heart overflowing with blood
• under the fibrous pericardium is the serous pericardium:

  • thin, slippery, two-layer serous membrane that forms a closed sac around the heart
• pericardial cavity: a slitlike space that contains a film of serous fluid

  • the fluid allows membranes to glide smoothly, allowing the heart to work without friction
• epicardium: visceral layer of the serous pericardium

  • also part of covering of heart
  • infiltrated with fat especially in older people
• myocardium: bulk of the heart

  • composed mainly of cardiac muscle
  • layer that contracts
• fibrous cardiac skeleton: reinforces the myocardium internally and connects the cardiac muscle fibers

  • collagen and elastic fibers are thicker in places where more support is needed
  • since this tissue is not electrically excitable this limits action potentials to specific pathways in heart
• In places where the great vessels come out of the heart and in the heart valves connective tissue makes sure that they don't become stretched out due to the stress of pushing blood out and in
• endocardium: sheet of squamous endothelium on a thin connective tissue layer

  • lines the heart chambers and covers the fibrous skeleton of valves
  • continuous with linings of blood vessels entering and leaving the heart
• Internal features of the heart:

  • Four chambers
  • two superior atria
  • two inferior ventricles
  • Interatrial septum: separates atria
  • Fossa ovalis: remnant of foramen ovale of fetal heart
  • Interventricular septum: separates ventricles
• Atria: the receiving chambers

  Small, thin-walled chambers; contribute little to propulsion of blood

  Auricles: appendages that increase atrial volume
• Right atrium: has a smooth walled posterior and an anterior part with ridges formed by muscle bundles called pectinate muscles

  • the posterior and anterior parts are separated by C-shaped ridge called the crista terminalis
• left atrium: mostly smooth and pectinate muscles are only found in the auricle

  • four pulmonary veins enter left atrium
  • these veins transport blood from the lungs back to the heart
• Blood enters the right atrium through

  • superior vena cava: returns blood from body regions superior to the diaphragm
  • inferior vena cava: returns blood from body areas below the diaphragm
  • coronary sinus: collects blood draining from the myocardium
• Right ventricle: forms most of heart's anterior

  left ventricle: dominates its posteroinferior surface
• Ventricles: discharging chambers of the heart

  • thicker walls because they actually pump blood out of the heart
  • propel blood out of the heart
  • right: into pulmonary trunk, takes blood to lungs
  • left: into aorta, largest artery in body
• blood flows from atria to the ventricles and out the great arteries leaving the superior part of the heart
• atrioventricular valves: one located in each atrioventricular junction to prevent blood from flowing back into the atria when the ventricles contract.
• tricuspid valve: the right valve has three flexible cusps, flaps of endocardium reinforced by connective tissue cores

  • between left ventricle and atria
• mitral valve or bicuspid valve: the left valve has two cusps and is between the left ventricle and atria
• each AV valve flap has chordae tendineae(little strings) that attach them to the papillary muscles

  • helps them stay closed so no blood goes into atria and so they don't go up into the atria
• • AV valves hang in down in the ventricles, when relaxed
  • when blood rushes through then the intraventricular pressure rises and pushes blood superiorly against these flaps, closing them shut
• semilunar, SL: aortic and pulmonary valves that prevent blood from going back into the ventricles

  • three pocket-like cusps, that are shaped almost like a half moon
• When ventricles contract the intraventricular pressure rises forcing the SL valves open and then when the ventricles relax the blood rushes back down and closes the valves.
• No valves guarding the entrances to venae cavae and pulmonary veins so blood does sprut back into these vessels but the backflow is minimal

  • why?: the inertia of the blood and when it contracts the atrial myocardium compresses these entry points
• pathway of a spurt of blood

  A) superior vena cava

  B) right atrium

  C) tricuspid valve

  D) right ventricle

  E) pulmonary semilunar valve

  F) pulmonary trunk

  G) pulmonary arteries

  H) to lungs

  I) pulmonary capillaries

  J) to heart

  K) pulmonary veins

  L) left atrium

  M) mitral valve

  N) left ventricle

  O) aortic semilunar valve

  P) aorta

  Q) to body

  R) systemic capillaries

  S) to heart

  T) inferior vena cava

  
• In relation to the heart veins carry oxygen-poor blood to the heart and the arteries carry oxygen-rich from the heart.
• • Left coronary artery supplies interventricular septum, anterior ventricular walls, left atrium, and posterior wall of left ventricle; has two branches:
  • Anterior interventricular artery
  • Circumflex artery
• • Right coronary artery supplies right atrium and most of right ventricle; has two branches:
  • Right marginal artery
  • Posterior interventricular artery
• Branching of coronary arteries is different for some people
• There are many anastomoses between the arteries but they could not supply the heart
• Heart requires 1/20 of body's blood supply and left side requires most of that
• Cardiac veins collect blood from capillaries veins:

  • great cardiac vein: in anterior interventricular sulcus
  • middle cardiac vein: in posterior interventricular sulcus
  • small cardiac vein: runs along the heart's right inferior margin
  • honorable mention: anterior cardiac veins dump into the right atrium, coronary sinus does this for those three branches
• trabeculae carneae


  irregular ridges of muscle marks on walls
• papillary muscles 


  muscle bundles that play a role in valve function