1. Cardiovascular system L1
Faisal I. Mohammed, MD, PhD
Yanal A. Shafagoj, MD, PhD
University of Jordan

2. Cardiovascular System Anatomy
Main Function of heart is to pump blood….Ejection

3. Anatomy of the heart 3

4. Anatomy of the heart 4

6. Cardiac valves

7. Cardiac Valves
Open and Close
Passively

8. Importance of
Chordae Tendineae

9. Importance of
Chordae Tendineae

10. Layers of the Heart Wall
Epicardium (external layer)
Visceral layer of serous pericardium
Smooth, slippery texture to outermost surface
Myocardium
95% of heart is cardiac muscle
Endocardium (inner layer)
Smooth lining for chambers of heart, valves and continuous with lining of large blood vessels
University of Jordan

12. Internal anatomy of the heart and Cardiac valves12

13. Heart Valves and Circulation of Blood
Atrioventricular valves
Tricuspid and bicuspid valves
Atria contracts/ ventricle relaxed
AV valve opens, cusps project into ventricle
In ventricle, papillary muscles are relaxed and chordae tendinae slack
Atria relaxed/ ventricle contracts
Pressure drives cusps upward until edges meet and close opening
Papillary muscles contract tightening chordae tendinae
Prevents regurgitation
University of Jordan

14. Movement of blood in the heart14

15. Systemic and pulmonary circulation - 2 circuits in series
Systemic circuit
Left side of heart
Receives blood from lungs
Ejects blood into aorta
Systemic arteries, arterioles
Gas and nutrient exchange in systemic capillaries
Systemic venules and veins lead back to right atrium
Pulmonary circuit
Right side of heart
Receives blood from systemic circulation
Ejects blood into pulmonary trunk then pulmonary arteries
Gas exchange in pulmonary capillaries
Pulmonary veins takes blood to left atrium
University of Jordan

16. Cardiac Muscle Tissue and the Cardiac Conduction System
Histology
Shorter and less circular than skeletal muscle fibers
Branching gives “stair-step” appearance
Usually one centrally located nucleus
Ends of fibers connected by intercalated discs
Discs contain desmosomes (hold fibers together) and gap junctions (allow action potential conduction from one fiber to the next)
Mitochondria are larger and more numerous than skeletal muscle
Same arrangement of actin and myosin
University of Jordan

18. Cardiac Muscle Tissue
Cardiac muscle, like skeletal muscle, is striated. Unlike skeletal muscle, its fibers are shorter, they branch, and they have only one (usually centrally located) nucleus.
Cardiac muscle cells connect to and communicate
with neighboring cells through
gap
junctions in
intercalated
discs. 18

19. Action Potentials and Contraction
Action potential initiated by SA node spreads out to excite “working” fibers called contractile fibers
Depolarization
Plateau
Repolarization
University of Jordan

20. Action Potentials and Contraction
Depolarization – contractile fibers have stable resting membrane potential
Voltage-gated fast Na+ channels open – Na+ flows in
Then deactivate and Na+ inflow decreases
Plateau – period of maintained depolarization
Due in part to opening of voltage-gated slow Ca2+ channels – Ca2+ moves from interstitial fluid into cytosol
Ultimately triggers contraction
Depolarization sustained due to voltage-gated K+ channels balancing Ca2+ inflow with K+ outflow
University of Jordan

21. Action Potentials and Contraction
Repolarization – recovery of resting membrane potential
Resembles that in other excitable cells
Additional voltage-gated K+ channels open
Outflow K+ of restores negative resting membrane potential
Calcium channels closing
Refractory period – time interval during which second contraction cannot be triggered
Lasts longer than contraction itself
Tetanus (maintained contraction) cannot occur
Blood flow would cease
University of Jordan

22. Action Potential in a ventricular contractile fiber
Depolarization
Repolarization
Refractory period
Contraction
Membrane
potential (mV)
Repolarization due to closure
of Ca2+ channels and K+ outflow
when additional voltage-gated
K+ channels open
Rapid depolarization due to
Na+ inflow when voltage-gated
fast Na+ channels open
Plateau (maintained depolarization) due to Ca2+ inflow
when voltage-gated slow Ca2+ channels open and
K+ outflow when some K+ channels open
0.3 sec
+ 20
–20
–40
– 60
– 80
–100 2 1 3
Depolarization
Repolarization
Refractory period
Contraction
Membrane
potential (mV)
Rapid depolarization due to
Na+ inflow when voltage-gated
fast Na+ channels open
Plateau (maintained depolarization) due to Ca2+ inflow
when voltage-gated slow Ca2+ channels open and
K+ outflow when some K+ channels open
0.3 sec
+ 20
–20
–40
– 60
– 80
–100 2 1
Depolarization
Repolarization
Refractory period
Contraction
Membrane
potential (mV)
Rapid depolarization due to
Na+ inflow when voltage-gated
fast Na+ channels open
0.3 sec
+ 20
–20
–40
– 60
– 80
–100 1
University of Jordan

23. 1 2 3 4

24. University of Jordan 24