1) Allows valves to keep certain diameter

2) Allows all muscles of heart to have attachment point (spiral attachment to squeeze heart when pumping)

3) Acts as conduction insulator between atria and ventricles

Formation of Interatrial Septum

(according to Bayer)

1) Septum primum comes from atrial roof and the endocardial cushion. Hole formed in middle is foramen primum.

2) A second perforation in the septum primum forms foramen secundum (above first one)

3) Foramen primum now closed.

4) Septum secundum forms from top & bottom on right of septum primum, overlaps with but doesn't close off the foramen secundum.

5) The top part of septum primum is gone. Bottom part of septum primum = valve of foramen ovale.

6) Hole in the septum secundum = foramen ovale.

Stoke Volume

Cardiac Output

SV = EDV - ESV

SV = 70 mL/beat

CO = HR x SV

CO = 5.25L/min

1) Preload: degree of stretch on the heart before it contracts (proportional to EDV)

2) Contractility: Forcefulness of contraction of individual muscle fibers (influx of Ca2+)

3) Afterload: Pressure ventricles must overcome before the semilunar valves open (approx. 80 mmHg in aorta)

Artery:

Intima: Endothelium, basement membrane, internal elastic lamina

Media: Smooth muscle cells, elastin & collagen, external elastic lamina

Adventitia: Loose connective tissue, vaso vasorum

Vein:

No internal/external elastic lamina

Valves to prevent blood backflow

1. Transportation - O2, CO2, metabolic wastes, nutrients, heat, hormones
2. Regulation - pH, temperatures, water content in cells
3. Protection of disease & loss of blood