Manual of basic techniques for a health laboratory - libdoc.who.int

212 Manual of basic techniques for a health laboratory5.7.2 MethodCollection of specimensThe semen is collected by the patient in a clean, dry bottle and is brought to thelaboratory as soon as possible after collection, preferably within 30 minutes. Itcannot be examined immediately as semen is a highly viscous fluid and must“liquefy”. It does this within 15–30 minutes and should be examined as soon aspossible after liquefaction has taken place.Preparation of slidesAfter liquefaction has taken place, make a thin smear of semen on a slide (similar toa blood smear), let it dry in the air and then heat it very gently to fix. Remove themucus (which will interfere with staining) by washing the slide with semen dilutingfluid (see above). Then wash the slide gently with buffered distilled water.Stain the sperm with Leishman stain or Giemsa stain (see section 9.10.3, page303–304).5.7.3 Macroscopic examinationVolumeMeasure the volume in a small graduated cylinder — the amount varies from onlya few drops up to 10ml. The normal volume is 4–5ml. Less than 1.5ml is consideredabnormal.ViscosityFreshly ejaculated semen should be completely liquefied within 30 minutes.Absence of liquefaction may interfere with sperm motility and fertilization.ColourSemen is normally an opaque grey colour. After an extended period of abstinencefrom sexual activity it may appear slightly yellow.pHThe pH is usually noted though it is of little significance. Semen is always alkaline,with an average pH of about 7.6 (range 7.2–8.9).5.7.4 Microscopic examinationNormal spermatozoa are 50–70mm in length, with a large oval head, a small neckand a long slender tail; the tail takes up about 90% of the total length (Fig. 5.27).The head is 3–6mm ¥ 2–3mm.Fig. 5.27 Normal spermatozoaSource: Image House Medical, Sperm MORPHsystem. Used with permission.