AGR 506 Endocrinology of the Male and Spermatogenesis

What is the range for intratesticular testosterone concentrations compared to systemic blood?

Testosterone is 100-500x's higher than systemic blood

Why is testosterone concentration important?

High testosterone concentration is required for normal spermatogenesis

What is the function of Leydig cells?

Produce testosterone in response to LH

What is the function of the Sertoli cells?

Convert testosterone to estradiol

Secrete inhibin

What does successful testis and spermatozoa production function require?

-Pulsatile GnRH secretion (every 3-6 hours)

-High concentrations of testosterone in the seminiferous tubule

-Low concentrations of testosterone in systemic blood

-Adequate LH receptors in Leydig cells

Where does spermatogenesis occur?

Entirely within the seminiferous tubules

What are the 3 spermatogenesis phases?

-Proliferation

-Meiosis

-Differentiation

What is the first phase of spermatogenesis and its function?

Proliferation

All mitotic divisions of spermatogonia

Generates spermatogonia that are committed to become more advanced cell types

What is the first second of spermatogenesis and its function?

Meiotic

Guarantees DNA replication and crossing over during production of secondary spermatocytes

Produces haploid spermatids

What is the third phase of spermatogenesis and its function?

Differentiation

Spherical undifferentiated spermatid undergo transformation results in production of a fully differentiated, highly specialized spermatozoon containing the head, flagellum and principle piece

What are the 4 phases of the Differentiation Phase of Spermatogenesis?

-Golgi Phase

-Cap Phase

-Acrosomal Phase

-Maturation Phase

What happens during Golgi phase in differentiation of spermatogenesis?

Acrosomic vesicle formation

What happens during Cap phase in differentiation of spermatogenesis?

Acrosomic vesicle spreading over the nucleus

What happens during Acrosomal phase in differentiation of spermatogenesis?

Nuclear and cytoplasmic elongation; spermatids become embedded in Sertoli cells with tails protruding toward seminiferous tubules

What happens during Maturation phase in differentiation of spermatogenesis?

Final assembly that forms a spermatozoon

What are the two main parts of Spermatozoa?

-Head

-Tail

What are the components of the head for the spermatozoa?

-Nucleus

-Acrosome

-Postnuclear cap

What are the components of the tail for the spermatozoa?

-Middle Piece

-Principal Piece

-Terminal Piece

What is the Acrosome and its function?

Membrane-bound lysosome that contains enzymes that covers 2/3 of the nucleus

Required for penetration of the ovulated oocyte

True or False: The Tail of the spermatozoa is a self-powered flagellum

True

What is Daily sperm production?

Total number of spermatozoa produced per day by both testicles of the male

What is daily sperm production dependent on?

The number of Sertoli cells populating the testes

What is Efficiency of sperm production?

Number of spermatozoa produced per day per gram of testicular parenchyma

What does it mean when there is greater testicular circumference?

Greater producing capabilities

Why do we use scrotal width or length in boars and stallions when estimating sperm production?

They have a non-pendular scrotum

What is motility?

The ability of sperm to swim progressively forward

Why is Spermatozoal Viability important?

Even though a male can produce high numbers of spermatozoa, it is important that they are alive and highly motile

What is the purpose of seminal extenders?

Used to dilute and preserve sperm

Extend both sperm viability and numbers

What makes a good extender?

-Isotonic

-Good buffers

-Minimize cold damage or cold shock

-Provide appropriate nutrients

-Prevent microbial growth

-Maintain viability

-Relatively low in cost

How is the sex determined?

Sperm

True or False: Endocrine control in the male and female are very different.

True

True or False: Leydig cells are analogous to cells of the granulosal cells of follicles in the ovary.

False

True or False: Sertoli cells convert testosterone to estradiol and secrete inhibin.

True

True or False: Intratesticular concentrations of testosterone are 100-500x's higher than that of systemic blood.

True

True or False: There is no delay in effects of deleterious events that can be observed by monitoring changes in ejaculated sperm, they happen instantly.

False