Spermatogenesis

Semen

Spermatozoa + seminal plasma, cellular suspension containing spermatozoa and secretions

Leydig cells

Male cell types with LH receptors, male equivalent of theca interna cells

Sertoli cells

Male cell types with FSH receptors, male equivalent of granulosa cells

Spermatogenesis

Process by which spermatozoa are produced that occurs in seminiferous tubules and continues throughout lifetime

Production of normal numbers of fertile spermatozoa

What requires: endocrine regulation of the testis, mitotic divisions of spermatogonia, meiotic divisions resulting in haploids, and morphological transformation into sperm

Secretion of GnRH, FSH and LH, and gonadal steroids

What are the endocrine requirements for spermatogenesis?

Leydig cells

LH dependent cells that have activation from P4 synthesis

Become refractory

When happens if LH is always chronic and high, downregulation and suppressed response to LH?

Sertoli cells

Male cells that are FSH dependent, convert T to estradiol using similar mechanism to granulosa cells

Inhibin

Hormone produced by Sertoli cells in the man, decreases FSH secretion from anterior pituitary

Androgen binding protein

Glycoprotein synthesized by sertoli cells that binds androgens to make them less lipophilic, enables spermatogenesis and sperm maturation

Successful testis function

What requires pulsatile GnRH secretion and adequate numbers of LH receptors on leydig cells

Seminiferous tubules, systemic blood

Where should the testosterone level be high? low?

Proliferation, meiosis, and differentiation

What are the three phases of spermatogenesis?

Proliferation

Phase of spermatogenesis that takes place in the basal compartment and has a continuous supply of stem cells

Spermatogonia

Most primitive cells in seminiferous tubules, all mitotic divisions, and diploid

Stem cell renewal

Important part of proliferation phase, maintains a pool of stem cells so the process can continue indefinitely

Meiosis

Phase of spermatogenesis with all meiotic divisions, DNA replication and crossing over guarantee genetic diversity

Primary spermatocyte

First meiotic division with a the longest lifespan of all male germ cells (18-19 days in the bull)

Secondary spermatocyte

Second meiotic division produces haploid spermatids

Differentiation

Stage of spermatogenesis where the spermatid turns to a spermatozoon, no further cell divisions, develop head/tail

Golgi, cap, acrosomal, and maturation

What are the four phases of differentiation in spermatogenesis?

Golgi phase

Phase of differentiation, golgi apparatus gives rise to acrosome, initial tail development, translocation of centriole

Cap phase

Phase of differentiation, acrosome vesicle flattens and forms a distinct cap, membrane forms and produces enzymes

Acrosome

Membrane-bound organelle covering a large portion of nucleus, contains enzymes to penetrate zona pellucida

Acrosomal phase

Phase of differentiation, nuclear and cytoplasmic elongation, spermatids embedded in sertoli cells

Manchette, neck, annulus

Which components form at the differentiation stage?

Maturation phase

Phase of differentiation, final assembly of spermatozoa, forms the completion of the tail and middle piece

Spermiation

Release of spermatozoa into lumen, analogous to ovulation in the female

Sperm head

Structure in sperm with nucleus, acrosome, and post-nuclear cap, tightly compact chromatin and highly keratinized

Sperm tail

Structure in sperm with middle piece, principle piece, and terminal piece for a self-powered flagellum

6-12 weeks

How many weeks are required before normal fertility is restored after an event?

Daily sperm production

Number of sperm produced each day by both testes, considerable variation in each

Testicular size

Good indicator of sertoli cell numbers/ sperm producing ability, can use a tape or caliper to determine

Motility

Ability of sperm to swim progressively, common assessment of viability

Gross motility

% of total ejaculate moving

Individual motility

% of sperm swimming in a progressive linear fashion

Morphology

Test of sperm viability, % of sperm that deviate from normal shape, should be around 5-15%

Concentration

Way to evaluate sperm viability, # of sperm per mL ejaculate

Sexed semen

Used to determine the sex of the offspring by sorting sperm cells, can use flow cytometer/cell sorter

4%

How much more DNA does an X chromosome contain than a Y chromosome?

Flow cytometry

Sorts sperm by differences in X and Y bearing sperm changing differences in intensity of fluorescent dye

90% accuracy, decreased fertility, and cost

What is the limitations of a flow cytometer?