Photoreceptor fine structure in the domestic ferret.
The morphology of the retinal photoreceptors has been studied in the domestic ferret by electron microscopy. 2 types of photoreceptor are present and are differentiated morphologically into the classical categories of rods and cones. Rods are longer, more slender and more numerous than the cones. The rod outer segment is uniform in diameter along its entire length while the cone outer segment tapers distally. Cone outer segments are short and large apical processes from the pigment epithelium extend some distance to wrap around them. Both rods and cones possess a connecting cilium and a large cross-striated fibril which begins near the ciliary basal body and extends through the outer segment to end near the external limiting membrane. Cone nuclei are more vesicular than rod nuclei. They form a single layer immediately beneath the external limiting membrane while rod nuclei form several layers beneath the cone nuclei. The synaptic region of the cone cells is larger and more elaborate than that of the rods. Synapses in both rods and cones appear to be formed by both superficial and invaginated contacts.
D000818:Animals; D002335:Carnivora / Q000033:anatomy & histology*; D002467:Cell Nucleus / Q000648:ultrastructure; D005289:Ferrets / Q000033:anatomy & histology*; D008854:Microscopy, Electron; D010786:Photoreceptor Cells / Q000648:ultrastructure*; D012374:Rod Cell Outer Segment / Q000648:ultrastructure; D013569:Synapses / Q000648:ultrastructure