Male Repro Physiology Flashcards
What is meant by the bipotential gonad?
Has both Wolffian ducts (male) and Mullerian ducts (female).
Activation of SRY causes Wolffian differentiation.
Descrive the differential development of the reproductive axes
At 7 weeks gestation, SRY gene activation
SRY controls testis differentiation through Sertoli and Leydig cells.
- Sertoli cells secrete AMH (causes female repro structures to regress)
- Leydig cells secrete testosterone (development of Wolffian duct system → vas def/epididymis/sex accessory glands
No SRY activation (no Y chromosome) = primite gonad develops into ovary.
What regulates puberty?
H-P-G axis
Hypothalamus induces secretion of GnRH → FSH and LH
Ovaries produce oestrogen, testes produce testosterone.
Describe testosterone feedback control
Testosterone powerfully inhibits both GnRH and LH secretion.
Sertoli cell function
Provide blood-testes barrier to allow HIGH concentration of testosterone and prevent it from diffusing out into blood (to cause negative feedback)
Where is sperm formed?
What types of cells can be found in there?
Sperm is formed in seminiferous tubules.
Cells:
- Germ cells: Spermatogonia mature into spermatozoa
- Myofibroblasts: Contractile, move sperm
- Sertoli cells: Nourish germ cells
- Leydig cells
Describe the structure of spermatozoa
Head:
- Contain haploid genome X or Y.
- Acrosome: Hyaluronidase and proteolytic enzymes to allow ovum penetration
Tail:
- Mitochondria for power
- Motile flagella
How do sperm cells mature as they travel?
Testicular spermatozoa are incapable of fertilisation.
Maturation is achieved at distal corpus/cauda:
- Acquire motility
- Acquire acrosome reaction capability
What are the three accessory glands in sperm production and their purpose?
Prostate: Secretes alkaline fluid that digest seminal fluids (PSA - prostate specific antigen) to allow sperm to swim easily
Seminal vesicles: Slows sperm down to allow it to mature
Bulbourethral glands: Lubricate area for sperm movement
Describe the process of erection.
Include parasympathetic activation
Increased arterial blood flow to corpora cavernosa - turgor compresses veins, preventing loss of blood and maintaining erection.
Corpus spongiosum remains pliable, as it houses the urethra.
Parasympathetic nerves release ACh and VIP (cause vasodilation) and NO (acts on cGMP to cause vasodilation)
Briefly describe pharmacological treatment of ED
NO acts on cGMP to cause vasodilation.
cGMP is degraded, and erection is lost.
Phosphodiesterase inhibitors prevent cGMP degradation.
Describe the 2 parts of ejaculation
2 part spinal reflex under sympathetic control
- EMission
- Vas def contraction moves sperm forward
- Prostate, seminal vesicle contraction moves seminal fluid forward
- Ejaculation
* Contraction of bulbospongiosus shoots out the sperm
How do sperm find their way to the egg?
Chemotaxis (progesterone) and thermotaxis (2 degree different between oviduct and ampulla)
Describe the acrosome reaction
Hyaluronidase and proteolytic enzymes digest proteins in ovum
Sperm reaches zona pellucida - binds ZP3, acrosome dissolves and creates pathway for passge of sperm
Why does only 1 sperm enter the oocyte most of the time?
Cortical reaction
- Sperm entry causes Ca2+ release, triggering the cortical reaction
- Proteases severe ZP3 receptors
- Hyalin forms impenetrable layer
