pinnule
anatomy
Quick Summary
A pinnule is a term used in anatomy to describe a small division or branch. It can refer to the secondary branches of a plumose organ, particularly in crinoids (sea lilies). It also denotes one of the ultimate divisions of a twice-pinnate leaf, which is common in ferns. Additionally, a pinnule can be a barb of a feather. In the context of sponges, a pinulus is a specific type of spicule with a projecting ray that develops small spines.1234
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