The World Health Organization (WHO) has published criteria for evaluating sperm morphology and identifying abnormal forms.
Parameters:
(1) head shape
(2) head size
(3) acrosome size
(4) head – others
(5) neck and midpiece
(6) tail
Parameter
Normal Features
shape
oval with smooth margin
length
4 – 5 microns
width
2.5 – 3.5 microns
ratio of length to width
1.5 – 1.75
acrosome (distal clear zone)
40- 70% of head
cytoplasmic droplets
small (see below)
width neck and midpoint
neck just under 1 micron, straight
neck insertion
one of the long axial tips of the head
tail
straight, about 45 microns in length
Number of heads:
(1) double
Head shape:
(1) round
(2) tapered
(3) amorphous
(4) piriform (pear shaped)
Head size:
(1) small
(2) large
Acrosome:
(1) absent
(2) < 40%
(3) > 70%
(4) irregular
(5) vacuolated
Neck and midpoint:
(1) thin
(2) thick
(3) irregular debris
(4) large cytoplasmic droplets (the WHO manual says normal is < 50% of head diameter but says abnormal is > 33% in Figure 2.8, page 20)
(5) eccentric insertion into head
(6) bent
(7) short
Tail:
(2) coiled
(3) bent
(4) short
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Specialty: Urology, Clinical Laboratory
ICD-10: ,