3.8 Male Reproductive Systems: A* understanding for iGCSE Biology

I am slightly wary about writing about the male and female reproductive systems.  Not because I get embarrassed with this topic (5 terms of human dissection at medical school removed any squeamishness about body parts….)  But rather that I worry that the school’s internet filters might start blocking my website if the wrong words appear.  But you don’t know until you try, so here goes…..

Male Reproductive System

I will start with the male reproductive system as males are simpler than females in many, many ways… The male reproductive system has three functions:

  • to produce the male gametes, sperm cells, at a prodigious rate
  • to make the male sex hormone testosterone
  • to act as a delivery system to ensure sperm cells are carried into the female reproductive tract in conditions that will allow them to fertilise an egg

male_reproductive_organs_med

The first two functions listed above happen in the testis.  There are cells in the testis that secrete the hormone testosterone into the blood from puberty onwards.  Testosterone switches on secondary sexual characteristics in the male (body hair growth, muscle development, change in pitch of voice etc.) after puberty.  The main part of the testis is made up of very long coiled tubules called seminiferous tubules in which the sperm cells are made.

fTdncmfmBWuUzelsDXJVcA_m 02c_testis

Humans have over a hundred meters of seminiferous tubules in total in both testes and this allows sperm cells to made at a very fast rate.  Even though it takes around 75 days to make an individual sperm cell, the testes make them at a rate of around 85 million sperm cells per day.  The epididymis is found next to the testis in the scrotum and is a coiled tube in which sperm cells continue to develop and mature.  Sperm are stored here too in readiness for ejaculation.

Everyone knows that in humans the testes are found outside the body cavity in order to keep them cool.  Sperm production happens at a maximal rate 3 degrees below core body temperature and having testes outside the body keeps them at this temperature.

The vas deferens is a tube lined with smooth muscle that carries sperm cells away from the testis for ejaculation.  As you can see it loops around the back of the bladder, before joining up with the urethra just below the bladder.  The urethra is the tube that carries urine away from the bladder but can also carry semen once the vas deferens has joined with it.

There are three accessory glands in the male system (prostate gland, seminal vesicle and the Cowpersglands)  These glands produce the fluid that when mixed with the sperm cells is called semen.  Semen contains a sugar fructose to provide energy for the sperm cells to swim.  It is slightly alkaline to neutralise the acidity in the vagina and also contains mucus to make the fluid easy to move along the tubes.

The sperm cells only acquire the ability to swim when in the epididymis and only become totally mature and able to fertilise the egg right next to the egg cell in the female tract.

Figure_28_01_05

The penis is an organ that contains erectile tissue that can fill with blood to allow the penis to fit into the female vagina for ejaculation.

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