Embryology
A) PARTS OF SPERMS AND THEIR DERIVATIVES
Manchette of sperm (Microtubule)
Head of sperm (NUCLEUS)
Acrosomal cap (GOLGI APPARATUS)
Nebenkern sheath {Spiral sheath around middle piece} (MITOCHONDRIA)
Proximal centriole and Distal centriole/Annulus (CENTROSOME- Microtubule organising center)
Residual bodies of Regaud (Cytoplasm)
Covering of Spermatozoa (Plasma membrane)
NOTE - Spermatozoa attains Full Motility during passage through Epididymis by activation of Cation channel proteins from CatSper family located in Flagellar Principal piece of sperm . CatSper channel is Ca+2 Permeable channel that is required for Hyperactivity of sperm flagellum , Chemotaxis towards egg , Capacitation , Acrosome reaction (as all of these require Calcium entry) . The presence of Inactive CatSper protein induces infertility.
Spermatogenesis
Spermatogenesis (Spermatogonia to Spermatozoa)
Spermiogenesis/Spermateleosis (Spermatids to Spermatozoa)
Spermatozoa/Sperms are produced inside Seminiferous tubules inside testes
Spermatogenesis starts at Puberty
Spermatogenesis is completed in 74 days
"CYCLE OF SEMINIFEROUS EPITHELIUM = 16 days"
Sex cords (derived from Genital ridge/Gonadal ridge) becomes Testis cords in males and Cortical cords in females
Testis cords are precursor structure to Seminiferous tubules
At Puberty Primordial stem cells (PSCs) differentiate into Spermatogonial stem cells and Spermatogonial stem cells undergo Mitosis and then give rise to Type A Spermatogonia (this marks the beginning of Spermatogenesis) and Type B Spermatogonia
Type B Spermatogonia (2n) undergoes Mitosis (Equational division) and is converted to Two Primary Spermatocyte (2n)
One Primary Spermatocyte (2n) undergoes Meiosis 1 (Reduction division) to convert to Two Secondary Spermatocytes (n)
From each Secondary Spermatocyte (n) two Spermatids (n) are produced by Meiosis 2 . Total 4 Spermatids are produced.
Each Spermatid produce 1 Sperm by differentiation (Spermiogenesis) . Total 4 Sperms are produced.
Major events in Spermiogenesis
Golgi phase (Formation of Head , Mid piece & Tail ; DNA packaging , Nuclear Morphogenesis & condensation )
Cap phase (Formation of Acrosomal Cap)
Tail phase (Tail formation by microtubule elongation and Rearrangement of organelles)
Maturation phase (Residual cytoplasm sheds off as residual body of Regaud by Phagocytosis)
#crackmbbs
image attribution and license
Attribution :
By Mariana Ruiz Villarreal - I did the diagram myself based on the one found on the book "Gray's anatomy" 36th edition, Williams & Warwick, 1980; and a diagram found of the review "Formation and organization of the mammalian sperm head" from Kiyotaka Toshimori and Chizuro Ito. (Chiba, Japan)., Public Domain, https://commons.wikimedia.org/w/index.php?curid=699220
By OpenStax College - Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=30132982