Related Experiment Video
Updated: Aug 18, 2026

Non-invasive Assessment of Microvascular and Endothelial Function
Published on: January 29, 2013
Distensibility of capillaries in the bat wing
1Department of Physiology and Biophysics, University of Washington, Seattle.
Abstract:
Preliminary experiments in our laboratory have shown that the distensibility characteristics of the capillary compartment in the bat wing depended upon its location in the vascular tree. The capillaries were then divided into arteriolar, middle and venular segments (according to their proximity to precapillary sphincters or nonmuscular venules). The bat was enclosed in an airtight box, one wing protruding through a slit and extended over a glass plate for microscopic observations. Continuous recordings of the diameter of the capillary segments were obtained; after 5 min of control recordings, the box pressure was raised in steps of 25 mm Hg to a maximum of 100 mm Hg and then returned to control level. The duration of each step was 4 min. Each increase of the pressure led to the dilatation of the capillary, but its arteriolar segment appeared to be more distensible than the middle and venous ones. After shifting the box pressure, the diameter increase was gradual and capillary distensibility decreased with increasing pressure (the venular segment showed the most prominent reduction in distensibility). These findings suggest the existence of a longitudinal gradient of distensibility in the capillary compartment.
Related Concept Videos
Anatomy of the Circulatory System
Arteries and Arterioles
Autoregulation of Blood Flow
Chemical Signaling in Autoregulation
Chemical signaling operates at the precapillary sphincter level, inciting either contraction or relaxation.
Pressure Relationships in Thoracic Cavity
Breathing Mechanisms
Both intra-alveolar and intrapleural pressures rely on specific lung properties. The ability to breathe—allowing air to enter the lungs during...
External and Internal Respiration
Capillarity in Fluid
Surface tension is crucial to capillarity. It results from cohesive forces between liquid molecules at the liquid-air boundary, forming a skin that resists external forces. When the capillary tube...

