Figure 2.

Simplifications of functional glomerular compartments for volume and surface estimations. a, Model of the average intraglomerular olfactory receptor neuron axon derived from morphological studies [inset, camera lucida reconstruction from a 21-d-old rat (Klenoff and Greer, 1998)]. The initial segment of the axon undergoes successive branching as shown. Overall branch length averages 200 μm, and there are ∼25 synaptic terminals (en passant varicosities and synaptic terminals) per axon. The area spanned by the axonal tree is relatively narrow. b, Morphology of the bulbar dendrites. Top left, Mitral cell dendritic tuft (courtesy of W. R. Chen). Bottom left, Branching pattern of mitral cell dendritic tuft. Top middle, Tufted cell tuft. Scale bar, 20 μm (courtesy of W. R. Chen). Bottom middle, Branching pattern of tufted cell dendritic tuft. Top right, Confocal reconstruction of biocytin-filled PG cell. Scale bar, 25 μm (from McQuiston and Katz, 2001). Bottom right, Branching pattern of PG cell dendritic tuft. c, Glomerular vascular supply. Left, Imaging of the capillary network within a single glomerulus by two-photon microscopy (from Chaigneau et al., 2003). Middle, Freehand representation of the capillary network. Right, Formal representation of the capillary network. d, Glomerular glial compartments. Far left, Distribution of astroglial sheets (dark gray) in glomerulus derived from two-photon microscopy (from Chao et al., 1997). Medium gray, Dendrites; light gray, sensory axons. Middle left, Simplified representation of glial process compartment (freehand representation). Middle right, Representation of sheet-like astroglial processes as volume-equivalent cylindrical edges of the compartment. Far right, Formal cube representation of a glial compartment.