Thursday, April 14, 2011

Objective 71 & 72: How sperm move and evolutionary fitness

Objective 71: Explore how spermatozoa move through the female reproductive tract
Objective 72: Evaluate fertilization in terms of evolutionary fitness

I know us woman really hate to admit it, but the sperm is a pretty amazing thing. The textbook was what I referred to figure out how spermatozoa moved through the female reproductive tract, but it really didn't do me any justice. I was able to find a picture on another site that shows the path of the sperm as it traveled through the female reproductive tract and that was pretty simple and to the point. What the textbook did inform me of was the structure of the sperm that allows it to make this incredible journey to fertilization. Spermatozoa consists of a head, mid piece, and tail. The head of the sperm contains compacted DNA and an outer helmet like layer called the acrosome that helps pierce the egg for fertilization. The mid piece contains the mitochondria, which provides the ATP needed for the movements of the tail to propel the sperm along. The tail allows the sperm to move easily and help it reach the egg.

But wait, there's more! Every sperm is perfectly equipped to make that long journey to fertilization, but not every sperm will reach the egg. This is where evolutionary fitness comes into play. Basically, only the "strongest" and "fastest" swimmer will make it to the egg. So, I see it as natural selection out of millions of sperm trying to reach that one "goal". The book gives a very good description on how the sperm adapts to the enviroment of the female reproductive system. Sperm is transported in semen that activates the sperm, helps their movement and protects them. The alkalinity of semen helps neutralize the acid enviroment of the male's urethra and the female's vagina. This protects the sperms and enhances their motility. Without the special structure of the sperm and the amazing adaptations of the body, the sperm would not be fit enough to make it to fertilization.

Here's a little photo I was sent a couple years ago. It made me laugh, and I believe it ties in very well with this subject.

1 comment:

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