Spermatogenesis- Lecture 7 Flashcards
Spermatogenic wave
The distribution of the stages along the length of the tubule in the wave, if the whole length of the seminiferous tubule is viewed at an given time.
Sperm cell head morphology
Top to bottom: Apical segment, principal segment, equatorial segment, postacrosomal region. Inside-out: plasma membrane, outter acrosomal membrane, acrosomal contents, inner acrosomal membrane, nuclear membrane, nucleus.
Endocrine regulation of testis function
Secretion of GnRH from the hypothalamus. FSH and LH secret from anterior pituitary. Testosterone produced by leydig cells. Inhibin and activin produced by sertoli cells. Loads of negative feedback!
The acrosomal phase
Spermatid nucleus begins to elongate and acrosome covers the majority of anterior nucleus. Manchette forms in caudal nucleus and extends toward flagellum. The neck and annulus become a juncture between the middle and principal piece.
Spermatocytogenesis (proliferation)
Mitotic divisions involving proliferation and maintenance of spermatogonia.
Spermatogenesis
Formation of spermatozoa from spermatogonia. (Spermatocytogenesis + meiosis + spermiogenesis)
Size difference between male and female gametes
A female gamete is much larger than a males gamete
Spermiogenesis (differentiation)
Morphologic transformation of spherical spermatids into spermatozoa.
The cap phase
The distal centriole forms the axoneme or flagellum that projects toward lumen of seminiferous tubule. The acrosomic vesicle flattens and begins to form a cap consisting of an outter and inner acrosomal membrane and acrosomal contents.
Relationship between GnRH, LH and FSH in males
GnRH causes a release of LH and FSH. When LH is lower it’s due to inhibin secreated by sertoli cells.
Spermatogenic cycle
A complete series of stages in one seminiferous tubule
Maturation phase
Mitochondria form a spiral assembly and around the flagellum that defines the middle piece. The postnuclear cap is formed from the manchette mucrotubules. The annulus forms the junction between the middle and principal piece.
Typical concentrations of blood LH and testosterone in a male
Pulses. LH is elevated for a period of .5 to 1.25 hours, while the testosterone episode lasts for .5 to 1.5 hours.
The golgi phase of spermatid differentiation
New spermatid is spherical and has a developed golgi apparatus. The small vesicles of golgi fuse giving rise t pro-acrosomic granules. The centrioles move opposite of acrosomic vesicle. The proximal centriole is an attachment point of the tail, The distal centriole gives rise to axoneme.
Typical sequence of spermatogenesis
Spermatogonia (A1-A4 and B) undergo a series of mitotic divisions the last giving rise to primary spermatocytes that then enter meiosis. This process allows of continual replacement of A1 spermatogonia. After meiosis, haploid spherical spermatids differentiate into spermatozoa (in adluminal compartment). Each generation divides in synch with cohorts.
