Arteriovenous shunts in the human spleen

Area of Science:

• Anatomy
• Physiology
• Microcirculation

Background:

• The human spleen's microcirculation has been debated, with evidence supporting both open and closed circulation models.
• Understanding splenic vascular pathways is crucial for comprehending its immunological and hematological functions.

Purpose of the Study:

• To investigate the existence and characteristics of arteriovenous connections in the human spleen.
• To determine if the human spleen exhibits a
• closed
• circulatory system.

Main Methods:

• Scanning electron microscopy (SEM) of plastic corrosion casts from human spleens.
• Perfusion with sized microspheres to assess arteriovenous shunt diameters.
• Freeze-fracture and critical-point drying techniques for examining sinus wall structures.

Main Results:

• Direct vascular conduits (arteriovenous connections) were identified between splenic arterial vessels and venous sinuses.
• Arteriovenous shunts with diameters as small as 7-10 µm were observed.
• Evidence of an "open" circulation was also found, characterized by pore-patterned sinus walls facilitating blood cell movement.

Conclusions:

• The human spleen possesses both "open" and "closed" circulatory pathways.
• The presence and frequency of arteriovenous connections necessitate a re-evaluation of the functional significance of closed circulation in the spleen.