Spermatogenesis Flashcards
Know how GnRH, LH, and FSH work together to cause spermatogenesis (including the cell types that secrete the, the cell types that have receptors for them and where feedback occurs).
-GnRH: Secreted from tonic center, Target the gonadotropic cells in the anterior pituitary, Feedback occurs in Hypothalamus
-LH: Secreted from the anterior pituitary, Acts on Leydig cells in the testes, Feedback occurs in Anterior lobe and Hypothalamus
-FSH: Secreted from the anterior lobe, Acts on sertoli cells, Feedback occurs in Anterior pituitary and Hypothalamus
GnRH
-Frequent, intermittent bursts: Lasts a couple of minutes
-Cause release of LH: Lasts 10-20 mins, Occurs 4-8 times a day
FSH
-Lower concentrations & longer durations: Constant secretion of inhibin and Longer half-life of FSH
-Received by Leydig cells: Progesterone is synthesized (Most is converted to testosterone)
LH
-Prevents Leydig cells from becoming unresponsive (reduced receptors)
~low testosterone levels occur
~LH pulses cannot be too long: Excess of testosterone, Intense negative feedback, Reduced testosterone (in long run)
-Too much testosterone
~FSH reduction: From negative feedback
~Sertoli cell function compromised
Know the different forms of the male germ cell.
-Spermatogonia
-Primary Spermatocytes
-Secondary Spermatocytes
-Spermatids
-Spermatozoa
Spermatogonia
-A1-A4, I, & B
-Specialized diploid cells
-Can revert back to less mature space
-Basal seminiferous epithelium
Primary Spermatocytes
-Haploid cells
-Adluminal seminiferous epithelium
Secondary Spermatocytes
-Haploid cells: “Crossed Over” chromosomes
-Adluminal seminiferous epithelium
Spermatids
-Haploid
-Spherical
-Adluminal compartment
Spermatozoa
-Highly condensed nucleus
-Acrosome is formed
-Motility achieved: Development of a flagellum and development of mitochondrial helix
-Lumen
What are between cytoplasmic bridges?
Daughter cells
Know how the divisions of Spermatogenesis progress.
-Spermatocytogenesis: Mitosis, A1-A4, I, & B Spermatogonia, Stem cells left over, and Last division produces Primary Spermatocytes
-First Meiosis: Produces Secondary Spermatocytes
-Second Meiosis: Produces Round Spermatids
-Spermiogenesis: Transformation into sperm-like shape (Golgi phase, Cap phase, Acrosomal phase, and Maturation phase)
-Spermiation: Separation of formed Spermatozoa from seminiferous epithelium
What is the order of the maturation phases of sperm development.
-Golgi
-Cap
-Acrosomal
-Maturation
Golgi phase
-Development of acrosome
-Migration of centrioles
Cap phase
-Acrosome development continues
-Flagellum elongates
Acrosomal phase
-Acrosome development finishes
-Manchette development: Series of microtubules, Associated with nuclear elongation
-Elongation progression
Maturation phase
-Manchette disappears
-Mitochondria migrate
-Dense fibers form
Spermatogenesis
The whole process of sperm production
Spermiogenesis
Differentiation of Spermatids
Spermiation
Separation of formed Spermatozoa from seminiferous epithelium
Know why stem cell renewal is important.
-Stem cell renewal
-Replenish testis: Injury, Trauma, and High heat
-Keep Spermatogenesis going indefinitely
Stem cell renewal
-process of renewing early mitotic cells to always have cells that are dividing to produce sperm.
-A2, A3, A4: Can revert back to less mature space, Can be maintained as a stem cell (Produce more sperm)
Stage of spermatogenesis
-Designation applied to a given cross section of a seminiferous tubule.
-Each seminiferous tubule can be at a different stage in any given cross section.
-Based on the degree of maturation of the cells closest to the lumen.
Cycle of spermatogenesis
-Time it takes the same cross section to complete all established stages
-Species dependent
-Multiple cycles needed for the whole development process
-All about TIME.
Wave of spermatogenesis
-Spermiation only occurs at certain sites.
-During a wave seminiferous epithelium progresses through stages.
-Causes spermiation to occur at different sites along the seminiferous tubule: creates a wave of sperm cell release.
-Provides a relatively constant rate of spermatozoa to the epididymis.
-Distance between the same stage is a wave.
-Think DISTANCE.
Know relative cycle length and duration of spermatogenesis for the boar, bull, and stallion.
Boar
~Cycle: 8.3 days
~Spermatogenesis: 39 days
Bull:
~Cycle: 13.5 days
~Spermatogenesis: 61 days
Stallion:
~Cycle: 12.2 days
~Spermatogenesis: 57 days
Know relative cycle length and duration of spermatogenesis for the ram and man.
Ram:
~Cycle: 10.4 days
~Spermatogenesis: 47 days
Human:
~Cycle:16 days
~Spermatogenesis: 75 days
Know what factors cause variation in sperm production.
-Testis size
-Efficiency of spermatogenesis: Mitotic division and Degeneration of germ cells
-Length of spermatogenesis
Know how many germ cells are present in the sertoli cells of stallions.
-Primary spermatocytes: 3.0 +/- 0.2
-Round spermatids: 10.9 +/- 0.9
-Max. Potential spermatids: 64
Know how many germ cells are present in the sertoli cells of bulls.
-Primary spermatocytes: 1.2 +/- 0.1
-Round spermatids: 5.2 +/- 0.6
-Max potential spermatids: 64
Know how many germ cells are present in the sertoli cells of men.
-Primary spermatocytes: 1.3 +/- 0.1
-Round spermatids: 4.2 +/- 0.2
-Max potential spermatids: 16
Know what factors might increase apoptosis.
-Normal: Typical part of spermatogenesis
-Abnormal:
~Seasonal factors
~Disease
~Trauma
~Heat
~Hormone levels
~Age
