spermatogenesis

• spermatogenesis is the production of spermatozoa within the testes
• Occurs in seminiferous tubules which is lined with immature cells called spermatogonia.
• spermatogonia contains a diploid number of chromosomes and begins dividing through mitosis at puberty to provide a continuous source of new cells
• some daughter cells of spermatogonia are pushed in towards the lumen of the tubule, where they undergo a period of growth. the enlarged cells are called primary spermatocytes. they are diploid cells and undergo the first stage of meiosis to produce secondary spermatocytes
• second meiotic division divides secondary spermatocyte into two spermatids
• Spermatids mature into spermatozoa (sperm), during this time, much of the cytoplasm is lost and the tail containing contractile material forms. while maturing they are nourished by special cells extending from outer portion of seminiferous tubule into centre 
• part of a spermatozoa :

  • head
  • neck
  • middle
  • tail
• the head is almost entirely nuclear material. it contains a fluid-filled tip called the acrosome. the fluid contains enzymes which are important if the sperm reaches the egg. the enzyme breaks down the layer of cells surrounding the egg for fertilisation
• the neck is between head and middle piece 
• the middle contains mitochondria which is where respiration takes place to provide energy for movement. around the mitochondria is a thin layer of cytoplasm. because there is only a little amount of cytoplasm, spermatozoa have a short survival period and receive nourishment from semen
• the tail is capable of contractile motion to propel the cell forward