L2.3 Heart & pericardium

Question 1

What is the positioning of the heart

Answer 1

• Rotates during development to assume position in the mediastinum
• R directed ANT, apex towards L

Question 2

Features of the R.atrium

Answer 2

• SVC - blood from above diaphragm
• IVC - blood from below diaphragm
• Walls:
  
  • Musculi pectinati (muscular ridges)
  • Smooth wall (separates R & L) atrium
• Crista terminalis (perpendicular to musculi pectinati) → ridge b/w walls
  
  • Project outwards to become the sulcus terminalis which is the landmark for SA node
• Fossa oval → remnamt of the fossa ovali
• Coronary sinus → receives all the veins that drains the heart
  
  • Opens directly into the R.A
  • b/w IVC & R.AV orifice
• R.AV orifice - guarded by the tricuspid valve
• Auricle
  
  • Projection in front of the great vessels
  • Remnant of how heart developed

Question 3

Features of the R.Ventricle

Answer 3

• Only last 10% of ventricular filling achieved by atrium contraction, mostly from pressure difference
• Tricuspid valve
  
  • Projected downwards to the ventricle
  • Each is attached to chordae tendinae, which is anchored by papillary muscles (exaggerate trabeculae carnae)
• Trabeculae carnae (same as musculi pectinali)
• Septomarginal (moderator) band
  
  • Base of ANT pap muscles → ventricular septum
  • Conduction of heart travels through band
• Conus arteriosis (infundibulum) → conical pouch where pul trunk arise

Question 4

Features of the L.atrium

Answer 4

• R & L pulmonary veins (paired) → L.A
• L. AV orifice guarded by bicuspid valve

Question 5

Features of the L.ventricle

Answer 5

• Similar to R. V
• Difference = thicker walls
• Semi-lunar valves
  
  • Closes through gravity (no chordae ten & pap muscles)
  • Blood falls down during ventricle relaxation → close valve
• Aortic vestibule → space before aorta

Question 6

Fetal blood circulation

Answer 6

• All O2 from maternal circulation via placenta, lungs not needed for oxygenation ∴ bypass
  
  • Blood bypass via:
  • Foramen ovali
    
    • From R → L.A.
  • Ductus arteriosus
    
    • Some blood may reach pulmonary trunk
    • Bypass pul circulation through duct into aorta

Question 7

Birth blood circulation

Answer 7

• ↑pressure in atm → lungs expand
• Blood moves into lungs
• Release hormones (e.g. bradykinin) → close ductus arteriosus
  
  • Blood pressure ↑ in L.A than R.A → shuts foramen ovali
• All happens instantaneously

Question 8

Fibrous skeletal structures of the heart

Answer 8

• Connective tissue → separates atria from ventricles
• Allows separation of electrical conduction → atria & ventricles contract separately
• Figure 8 around valve in the same plane

Question 9

Nerve supply to the heart

Answer 9

• Parasym: vagus → over arch of aorta
• Sym: Pregang from T1-4
• Cardiac plexus around aortic trunk

Question 10

Pericardium

Answer 10

• Serous pericardium → double layer membrane around heart
  
  • Visceral (aka epicardium)
  • Parietal
  • Pericardial space in b/w → provides lubrication (serous fluid)
• Fibrous pericardium → surrounds serous pericardium

Question 11

N supply to the pericardium

Answer 11

• L & R phrenic N (C3,4,5)

Question 12

Pericardial sinuses

Answer 12

• Spaces inside the pericardial cavity
• Transverse
  
  • B/w aorta & pul trunk ANT & INF
  • Separates A from V
  • Important for heart transplant → able to get around roots of aorta
• Oblique
  
  • Formed by reflection onto pul V