heart anatomy

the anatomical location of the heart

• Adult heart is the size of a closed fist

• Located obliquely in the mediastinum: midline partition of the thoracic cavity

• Apex: blunt, rounded point of the heart

  • Apex directed anteriorly and slightly inferiorly

  • Directed to the left

  • Located deep to the fifth intercostal space

• Base: larger, flat part at the superior end of the heart

  • Base directed posteriorly and slightly superiorly

  • Located deep to the sternum and extends to the second intercostal space

• Heartbeat: never hear the valves open, only close

  • First noise: AVs close

  • Second noise: SLs close

visceral pericardium (same thing as epicardium)

- deepest layer

- Percardial fluid (pericardial cavity) exists inbetween the visceral and parietal percardial; serves as protective lubricant, reduces friction

parietal pericardium

Middle layer

• Can accommodate changes in heart size by enlarging

• Can increase in volume to hold more pericardial fluid

fibrous pericardium

- Outermost layer

- connects the heart to surrounding tissues

- Restricts the heart from stretching too much: the heart becoming too big from stretching can be pathologically deficient as now an increased amount of blood will always leave the heart (can happen in athletes)

Epicardium

- Same thing as visceral pericardium

- outermost layer

- Superficially contains a layer of simple squamous as it touches fluid

- Contains adipose from protecting

- simple squamous -> loose CT -> adipose

Myocardium

- Middle layer

- Muscle

- Makes up most of the mass of the heart

- loops around the chambers: makes them smaller which pushes blood out

Endocardium

- Deepest layer

- Lines the entire inside of heart

- Contains layer of simple squamous on inside as it touches fluid

Right side = much _______ than the left side

- Right side = much smaller than the left side

- This is because the lungs are very close to the heart, meaning blood leaving the right ventricle does not have very far to travel

- Meanwhile, the blood going throughout the body from the left ventricle has a long ways to travel, meaning this side needs more muscle volume for additional force

- Congestive heart failure: the left side of the heart gets too weak (but the right doesn't); blood pools in the lungs and the body is deprived of oxygenated blood

Heart Chambers

- Right and left ventricles

- Right and left atria

Auricles

flap-like extensions that allow the atria to get larger

Blood leaving the heart

pulmonary trunk, aorta

Aorta

- Blood leaves left ventricle and enters aorta

- Carries blood from left ventricle to the body

- Behind the pulmonary trunk

- Branches off into aortic arteries: brachiocephalic artery, left common carotid artery, left subclavian artery

Pulmonary trunk

- Blood leaves right ventricle into pulmonary trunk

- Carries blood to the lungs

- Pulmonary arteries bring blood to the lungs

Blood entering the heart

superior and inferior vena cava, smaller coronary sinus, four pulmonary veins

Superior and inferior vena cava

- Bring blood from the body to the right ventricle

- Considered part of the systemic circuit because the end of the system circuit = the right atrium

smaller coronary sinus

carries blood from the walls of the heart to the right atrium

Pulmonary veins

- Bring blood from lungs to left atrium

- Enter posteriorly

Coronary sulcus

• large groove running obliquely around the heart → separates atria from the ventricles

• Division between left and right ventricles

  • Anterior interventricular sulcus: anterior surface of the heart → extends from coronary sulcus to the apex

  • Posterior interventricular sulcus: posterior surface of the heart → extends from coronary sulcus to the apex

Pulmonary arteries

-Bring blood from right ventricle to lungs

- Anterior

Right marginal artery

supply blood to the lateral wall of the right ventricle

Posterior interventricular artery

supplies blood to the posterior and inferior part of the heart

• Lies in the posterior interventricular sulcus

Left coronary artery

• has 3 branches

  • Anterior interventricular artery: supplies blood to most of the anterior part of the heart

    • Extends inferiorly in the anterior interventricular sulcus

  • Left marginal artery: supplies blood to the lateral wall of the left ventricle

  • Circumflex artery: supply blood to most of the posterior wall of the heart

    • Extends around to the posterior side of the heart in the coronary sulcus

Anastomosi

direct connections between the arteries

• Blockage will not impede blood flow

Major veins that carry blood from the heart wall to the atrium

Great cardiac vein: drains blood from the left side of the heart

Small cardiac vein: drains blood from the right margin of the heart

• Converge near the posterior part of the coronary sulcus

  • Enter into a large venous cavity → coronary sinus → then empties into the right atrium

Atrioventricular valve

• located in each atrioventricular canal → composed of flaps

  • Ensures one-way flow of blood from the atria to the ventricle

  • Blood flows into ventricles by pushing on the valve

Tricuspid valve

•  between right atrium and right ventricle

  • 3 cusps

Bicuspid valve

• between left atrium and left ventricle

  • 2 cusps

Papillary muscles

• muscle found in each ventricle

  • Attached to the valves by CT strings → chordae tendineae 

  • Ventricles contract → pull on strings to prevent valves from opening

Left Semilunar/aortic valve

- In-between aorta and left ventricle

- Stop blood from going back into left ventricle from aorta when ventricles are relaxed

Right semilunar/pulmonary valve

Stops blood from going back into heart from pulmonary valve

Aortic semilunar valve

Stops blood from going back into the heart from aorta

Atrioventricular valve (AV)

- Between atria and ventricles

- Closed when the ventricle is contracting to prevent blood from going back into the atrium

- The papillary muscle contracts which pulls on the chordae tendineae attached to the valve to close it during ventricle contraction

- Heart murmur = the valve doesn't close correctly

Trabeculae carneae

muscle woven into the wall of the heart to make it stronger

Circuits start at the ________, and end at the _______

Circuits start at the ventricles, and end at the atria

Pulmonary circuit

Right ventricle -> pulmonary trunk -> pulmonary arteries -> lungs -> pulmonary veins -> left atrium

Systemic circuit

Left ventricle -> aorta -> aortic arteries (brachiocephalic, left common carotid, left subclavian) -> body -> superior and inferior vena cava -> right atrium

characteristic of cardiac muscle

- Branched, short, and interconnected fibers

- Striated

- Cardiac muscle fibers are functionally connected

- Intercalated discs = cardiac muscle gap junctions

- Electrical current is generated at the pacemaker cell, and is then spread cell to cell via the intercalated discs

- Anchoring desmosomes

- Entire myocardium acts as a single unit

Pulmonary circulation

carries deoxygenated blood from heart to the lungs, then returns oxygenated blood to the heart

Systemic circulation

carries oxygenated blood from the heart to the body, returns deoxygenated blood back to the heart