Spermatogenesis-Male Anatomy

Question

Explain the term Spermatogenesis with the help of figure.

Answer 1

Take a look at the etymology of the title of this section – sperm + genesis – or creation of sperm! The testis is about 4 cm long by 2.5 cm wide in adult men and is covered by thin fibrous capsule.  The interior is divided into compartments or lobules.  It is composed of tightly packed coils of SEMINIFEROUS TUBULES which measure about 250 metres in length! 

The entire inner surface of the seminiferous tubules is lined with SPERMATOGONIA which actually produce the sperm.  Spermatogenesis can only occur at about 95’F or 35’C and internal body temperature is 98.6’F or 37’C. And here is something totally amazing – the scrotum can control its own temperature through the use of CREMASTER muscles which pull the scrotum closer to the body if they are cold so that the 35’C is maintained!  
 
Inside the testes the seminiferous tubules empty into the RETE TESTIS which in turn empties into the EPIDIDYMIS.  This is another coiled tube that if uncoiled would stretch out to 6 ½ metres in length. The sperm spend about 10 days in the epididymis before they are mature enough to continue their journey. So although the sperm are produced in the testis – they mature in the epididymis where the acidic environment keeps the mature sperm inactive.

Let’s return to how the sperm are produced.  During spermatogenesis, spermatogonia divide to form SPERMACYTES – which then differentiate into SPERMATIDS which are immature sperm cells.  In normal body process SOMATIC cells are produced which contain 46 chromosomes – spermatids are considered HAPLOIDS since they only contain 23 chromosomes or ½ of the male parent’s DNA. The whole process of spermatogenesis takes about 70 days and once mature the sperm can live several weeks inside the male. 
 
SERTOLI CELLS nourish the developing SPERMATIDS until they are mature and they provide a barrier between the blood and the seminiferous tubules.  If immature sperm exit before they are mature they are useless.  If also protects the sperm from the blood vessels which supply the necessary hormones and nutrients for growth – if this barrier gets damaged and the sperm enter the blood vessels the body senses it is a foreign object and will produce antibodies against its own sperm!  (Another reason for infertility).