Heart - LO 4
4. Identify the unique structures of the right atrium.
Auricle (appendage): muscular pouch which projects anteriorly
Remnant of the embryonic atrium
Internally, has some pectinate muscles
Sinus venarum (venous part)
Smooth posterior wall of the internal R. atrium
The openings for the superior vena cava, inferior cava, and coronary sinus are located on this wall
Sulcus terminalis
External groove on R. atrium
Serves to demarcate where the division between the smooth sinus venarum and atrium proper are located internally - corresponds with the internal crista terminalis
Crista terminalis
Internal ridge of muscle that divides the smooth sinus venarum from the rest of the atrium (muscular pectinate part)
Corresponds with the external sulcus terminalis
The sinu(sino)-atrial node is located in the superior portion of the crista terminalis
Pectinate muscle
Pectinate muscle is only located in atria
Extend from the crista terminalis
Interatrial septum
Wall between the R. and L. atrium
Has a small depression, fossa ovalis
Located left, superior to the opening of the inferior vena cava
This is a remnant of the foramen ovale:
In utero, allowed the flow of oxygenated blood from the placenta (through the umbilical v.) to be directed toward the L. atrium through a flap-like valve (preventing any left to right flow of blood)
The foramen ovale typically closes at birth
In some individuals, a small opening (patent foramen ovale) is located in the upper portion of the fossa, which is typically subclinical
R. atrioventricular (tricuspid) valve orifice
The R. AV valve is located between the R. atrium and R. ventricle
The orifice is usually best observed from the atrial side