Heart Functional Anatomy

Anatomy and Physiology II

Heart tissues

• made mostly of cardiac muscle cells by volume

  • called myocytes and cardiomyocytes

  • highly metabolic

• Contains connective tissue → fibroblasts and fat

• Epithelia → endothelium lines surfaces and blood vessels

• Nerve → autonomic nerves

  • sympathetic postganglionic termini

  • parasympathetic ganglia and termini

How does the heart develop pressure?

• shortening of myocytes decreases volume, forces blood out of pump chambers → systole

  • decrease in volume leads to increase in pressure

• Relaxation of myocytes and back-pressure refills the pump → diastole

  • increase in volume leads to decrease in pressure

• heart rate and contractile strength is modulated by the autonomic system

Anatomy of heart within the thorax.

• located in the mediastinum of the thoracic cavity within the lungs

• made of four chambers that differ in muscle wall thickness

  • 2 atria (thin) + 2 ventricles (thick)

• size of a fist and weighs 300 grams

• located in the mediastinum of the thoracic cavity

  • posterior to the sternum the

  • 2nd rib to 5th rib

  • laterally by the lungs and posterior to the spine

• anterior to vertebrae, esophagus, and large vessels

• ventricles mostly on left inferior side of mediastinum

• atria mostly on right superior side of mediastinum

Name the coverings of the heart.

• Pericardium: double-walled sac

  • Fibrous → tough, outer layer of fibrous tissue

  • Serous → made of endothelium

    • thin, inner layer with two parts:

      • outer layer attached to fibrous → parietal layer

      • pericardial cavity contains thin liquid in between

      • thin inner layer attached to heart → visceral layer

      • allows for free movement of heart within pericardium

Pericarditis

• inflammation causes this

• minor → pain in sternum + sticking of layers together limiting heart movement

• major → excess fluid accumulation in pericardial cavity limiting heart pumping

Describe the functional anatomy of the three layers of the heart.

• epicardium (outer):

  • simple squamous epithelium of visceral layer of pericardium + fat

• myocardium (middle):

  • cells arranged in a circular and spiral fashion

  • connective tissue around cells, bundles of cells and between chambers

  • responsible for pumping action

• Endocardium (inner):

  • simple squamous epithelium

  • lines chambers and valves

  • sees blood

  • thin layer between endothelium and myocardium

Anatomy of function of chambers of heart

• atria > ventricles

• septa separates left and right atria and ventricles

  • interatrial septa + interventricular septa

• Right side receives systemic blood + pumps thru pulmon circuit

• Left side receives blood from pulmon circuit + pumps thru systemic circuit

• Visible surface grooves at pump boundaries

  • coronary sulcus between atria and ventricles

  • surrounds like a crown

• Interventricular sulci between ventricles

  • anterior/posterior

Atria

• thin-walled and have appendages (flaps - auricles)

  • muscle bundles called pectinate muscles

• The right atrium receives blood from the venous great vessels → inferior and superior vena cava + coronary sinus

• The left atrium receives oxygenated blood from the pulmonary veins

  • right and left pulmonary veins

• pumps blood into respective ventricles to fill

Ventricles

• receive blood from respective atria

• pump blood into great arterial vessels

  • right ventricle pumps blood into pulmonary arteries

  • R and L pulmonary arteries

  • Left ventricle pumps blood into aorta

• Interior → not smooth

  • trabeculae carnea → ridges of muscle

  • papillary muscles → connect to valves via tendons

• L > R

Valves

• used to prevent back flow of bood into pumps

• checks to see if pressure is high enough before pumping

• cloeses when pressure lower on pump side but opens when higher on pump side → uni-directional flow

AV Valves

• endothelial CT between the atrium and ventricles

• Tricuspid: Right side; 3 flaps

• Mitral (Bicuspid): Left side; 2 flaps

  Function: Prevent backflow into atria during ventricular contraction

  Mechanism: Chordae tendineae + papillary muscles hold flaps in place

Semilunar valves (betwen ventricles and great arteries)

• pocket like flaps in the shape of a half moon

• pulmonary valve → right ventricle to pulmonary artery

• Aortic valve → left ventricle to aorta

• prevents backflow into ventricles

• open with ventricular pressure

• close with back pressure from arteries or ventricular pressure falls

Trace the path of blood through the heart

1. Systemic veins →

2. Superior/inferior vena cava, coronary sinus →

3. Right atrium →

4. Tricuspid valve →

5. Right ventricle →

6. Pulmonary valve →

7. Pulmonary arteries →

8. Lungs (gas exchange) →

9. Pulmonary veins →

10. Left atrium →

11. Mitral valve →

12. Left ventricle →

13. Aortic valve →

14. Aorta →

15. Systemic circulation

Left coronary artery

branches into + from aorta + supply heart tissue from outside in

blood is drained from the heart via coronary sinus

• LAD (left anterior descending artery)

  • along anterior interventrivcular sulcus

  • feeds interventricular septum + anterior ventricles

• Circumflex artery

  • feed left atrium + posterior left ventricule

Right coronary artery

• right marginal artery

  • feeds the lateral right side of the artery

• Posterior interventricular artery

  • along posterior interventricular sulcus

  • feeds apex + posterior ventricular walls

Cardiac muscle

• striated like skeletal

  • cells are smaller, branched and mono/binucleated

  • more mitochrondria

  • intercalated discs with gap junctions

• A-bands same length but I-band shortern and not as uniform, z-band are a bit thicker

• T-tubules at Z-lines (not A-I junction like skeletal (only 1 per sarcomere)

• Uses extracellular calcium + SR calcium for contraction

• Contracts as a functional syncytium

• Cannot undergo tetany due to long refractory period

• Relies mostly on aerobic respiration

• dyads