The anatomy of the mammalian spermatozoon with particular reference to the guinea pig.

Abstract

A description of the guinea pig spermatozoon has been presented using descriptive terms that are applicable to mammalian spermatozoa in general. The spermatozoon consists of two principal parts, the head and the tail. The tail is further subdivided into four regions, the neck, middle-piece, principal-piece and end-piece. The principal components of the head are the acrosomal cap and the nucleus. On its posterior surface, the nucleus bears a shallow implantation fossa lined by the nuclear envelope which is locally specialized to form the basal plate. The neck contains a connecting-piece bearing an articular surface that attaches to the basal plate lining the implantation fossa. The connecting-piece is formed by the convergence and fusion of nine longitudinal segmented columns which merge caudally with nine outer dense fibers that surround the axial filament complex throughout the major part of the length of the flagellum. In the middle-piece, the core of longitudinal fibers is surrounded by a mitochondrial sheath. The end of the middle-piece is marked by the annulus, a thin dense ring to which the flagellar membrane is firmly adherent. In the principal-piece, the core of longitudinal fibers is enclosed in a fibrous sheath composed of closely spaced circumferential ribs that attach to two longitudinal columns running along opposite sides of the sheath for its entire length. It is suggested that accurate communication would be facilitated by abandonment of the terms “galea capitis”, “head cap”, “post-nuclear cap”, “implantation plates”, “thin laminated fibers”, “protoplasmic bead”, “middle-piece bead”, “ring-centriole”, “Jensen's ring”, “spiral sheath”, “tail helix”, and “tail sheath”.