DR KARI LOUNATMAA / SCIENCE PHOTO LIBRARY DR KARI LOUNATMAA / SCIENCE PHOTO LIBRARY
Human sperm head and neck. Transmission Electron Micrograph (TEM) of a freeze-fractured human sperm. The head (at right) and neck (lower left) of the sperm are seen. In this freeze-fracturing technique the sperm surface is seen. The outer membrane of the sperm reveals some internal structures. The large head of the sperm contains genetic material, with filamentous structures seen at right. The sperm's neck has many small energy- producing mitochondria, seen as lumps in the neck. The neck is attached to a long tail and these mitochondria enable the tail to move with a whip- lash motion. Around the sperm is seminal fluid. Magnification: x40,000 at 8x10 inch size.
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