Heart

Question 1

Basic structure of circulatory system

Answer 1

1. TUNICA INTIMA
   - inner lining
   - singler layer of endothelial cells
2. TUNICA MEDIA
   - intermediate layer
   - predominantly muscular layer
3. TUNIC ADVENTITIA
   - outer supporting layer
   - sometimes contain VASA VASORUM that supplie the tunica media of large vessels e.g. aorta

Question 2

Exhibits the greates variation from one part of the circulatory system to another

Answer 2

Muscular content

Question 3

Remarks on intercalated discs

Answer 3

Composed of gap junctions and desmosomes (macula adherens)

Question 4

Remarks on gap junctions

Answer 4

Are present at the intercalated disks
Are low-resistance paths between cells that allow for rapid electricl spread of action potentials
Accout for ELECTRICAL SYNCYTIUM

Question 5

Remarks on inflammation of the heart

Answer 5

Myocarditis: most commonly viral
Pancarditis: rheumatic fever is a cause

Question 6

Remarks on endocardium

Answer 6

“The endocardium of the atria is much thicker and includes more elastic fibers [than the ventricles]”

Question 7

Where is the AV node?

Answer 7

In the medial wall of the right atrium just above the tricuspid valve ring at the base of the interatrial septum
Phase 0: interatrial septum superior to the opening of coronary sinus
SNELL: lower part of th atral septum just above the attachment of the SEPTAL CUSP of tricuspid valve

Question 8

Pathway of conduction of the heart

Answer 8

1. SA node
2. AV node
3. AV bundle of His (membranous)
4. Right and left bundle branches (muscular portion of IV septum)
5. Purkinje fibers (halfway down the interventricular septum)
   - run immediately beneath the endocardium before penetrating the myocardium

Question 9

Normal weight of the heart

Answer 9

Males: 280-340 grams
Females: 230-280 grams

Question 10

The sternocostal surface of the heart is formed primarily be the

Answer 10

Right ventricle

Question 11

Where is the apex beat

Answer 11

5th ICL L MCL

3.5 inches (9cm) from midline

Question 12

Placement of ECG leads

Answer 12

V1: 4th ICS just to the right of sternum
V2: 4th ICS just to the left of sternum
V3: midway bet V2 and V4
V4: MCL, 5th L ICS (apex)
V5: AAL, 5th ICS
V6: MAX, 5th ICS

Question 13

Remarks on the interventricular septum

Answer 13

UPPER PART
-small, thin
-membranous
-attached to the fibrous skeleton
LOWER PART
-thick
-formed of muscle

Question 14

Remarks on the skeleton of the heart

Answer 14

Fibrous rings that surround the AV, pulmonary, and aortic orifices
Continuous with the MEMBRANOUS upper part of the ventricular septum ⭐️
Prevent the valves from stretching and becoming incompetent
Forms the basis of ELECTRICAL DISCONTINUITY between the atria and ventricles

Question 15

Where is the SA node?

Answer 15

Wal of the right atrium in the upper part of the sulcus terminalis just to the RIGHT of the opening of the SVC

Question 16

Speed of conduction of the cardiac impulse trough the AV node

Answer 16

0.11 seconds (Snell)

Question 17

The only pathway of cardiac muscle that conencts the myocardium of the atria and the myocardium of the ventricles

Answer 17

AV bundle of His

• descends through the fibrous skeleton of the heart
• descends behind the septal cusp of the tricuspid valve to reac the inferior border of the membranous part of the ventricular septum