Blog written by Laboratory Staff C.O.
The term morphology refers to the form and structure of an object or thing. Sperm morphology is the term used to describe the appearance (size and shape) of sperm. Morphologically normal human sperm will have a smooth, oval shaped head with a long tail attached at the distal aspect of the head. Sperm is described as normal if it has an oval-shaped head that is 5 to 6 micrometers long and about 3 micrometers wide with a well-defined acrosome (cap) covering 40 to 70 percent of the head. There should be no visible vacuoles in the head, midpiece or tail, and no cytoplasmic droplets larger than half the size of the sperm head.
There are many abnormalities a sperm may exhibit, such as head and tail defects including crooked or double tail. The whip like motion of the tail is what propels the sperm forward to swim through the passages of the female reproductive system towards the egg. If abnormal sperm has a defective tail it will have a very difficult time reaching the egg and fertilizing it. The egg is enclosed in a glycoprotein coat called the zona pellucida (ZP). The ZP can be viewed as a selector or filter for morphologically normal sperm because it has been shown that sperm with abnormal head morphology attach to the ZP in lower frequencies than sperm that have normal head morphology.
Stay tuned for our future blog on how morphology is determined in the laboratory.
