VGO 511: Veterinary Andrology and Reproductive Techniques (1+1)

Structure of spermatozoa

SPERMATOZOA

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The head of spermatozoa has a shape characteristic for each species.

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• Chromatin is compact.
• Anterior 2/3^rd of the nucleus is covered by acrosome which is a membrane bound lysosome that contains hydrolytic enzymes such as acrosin, hyaluronidase, zonalysin, esterases and acid hydrolases which are required for penetration of cellular investments and zona pellucida.
• The tail composed of capitulum, middle piece, the principal piece and the terminal piece
• The capitulum fits into the implantation socket, a depression in the posterior nucleus
• Anterior portion of the tail consists of laminated columns – gives neck region flexibility
• Axonemal components of tail originate from the distal centriole consists of 9 pairs of microtubules arranged radically around 2 central filaments. Surrounding this 9+9+2 arrangement are 9 dense fibres that are unique to the flagellum of spermatozoa.
• The mitochondrial sheath is arranged in a helical pattern around the outer dense fibre of the tail and contributes to the middle piece
• The middle piece terminates at annulus which demarcates junction between it and principal piece
• Principal piece makes up majority of tail
• Continues and connects the terminal piece.

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Biometry of spermatozoa in different species

Species	Head (µ)		Mid piece (µ)		Tail (µ)		Total length (µ)
	Length	Width	Length	Width	Length	Width
Cattle	9.05	4.25	14.84	0.67	45.50	0.51	69.59
Buffalo	7.50	4.70	11.95	0.62	42.50	0.50	61.95
Ram	8.20	4.25	14.00	0.80	40.45	0.50	62.65
Buck	8.14	4.30	12.52	0.72	42.77	-	63.43
Boar	8.05	4.18	11.55	0.55	32.94	-	52.54
Stallion	7.00	3.91	9.83	-	42.30	-	59.13
Poultry	12.5	-	4.00	-	80.00	-	96.50
Dog	5.5-7.0	2.0-4.0	7.0-13.0	1.0	40.0-45.0

• The nucleus is oval and flattened and is surrounded by nuclear membrane.

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