150 BICD Summer 2011
Mo
Week 3: Handout #3
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Material Covered: Male Reproduction
Lobby
Ni
OH: Tuesday 1-2pm Peterson Hall
Male Reproduction
Gross Anatomy:
The male external genitalia consist of: _________________________________________________________________
The male accessory structures consist of: _______________________________________________________________
Mechanism of erection:
Acetylcholine targets endothelial cells
Microscopic Anatomy:
The testes contain two types of cells:
- Leydig cells
o Targeted by _______
o Secretes: _________________
- Sertoli cells
o Targeted by _______
o Secretes:
_________________________
_________________________
Gametogenesis
Embryonic State/Pre-puberty:
- Spermatogonium (diploid) undergoes mitotic division to make more spermatogonia
Puberty and Later:
- Spermatogonia continue to undergo mitotic division
- Some of these spermatogonia undergo DNA replication and crossing-over of sister chromatids to make primary
spermatocytes (diploid + duplicated)
- First meiotic division results in secondary spermatocytes (haploid + duplicated).
- Then, these secondary spermatocytes undergo the second meiotic division, which results in spermatids (haploid)
- These spermatids then mature into haploid sperms.
Androgens
Synthesis:
- Precursor for all androgens: _____________________. This is transported into the mitochondrial matrix via transporter
called __________
- Once in the matrix, cholesterol is converted to __________________________, which can go through a variety of pathways
to make other androgens.
DHEA (dehydroepiandrosterone) weak androgen that is also synthesized in adrenal glands by both males and females.
- Oxidation results in synthesis of androstenedione, which is the precursor for testosterone
Testosterone consists of the majority of (95%) androgens produced
- Testosterone is responsible for the development of the ______________ duct into male accessory structures.
- In addition, testosterone is also responsible for the secondary male sexual characteristics (e.g. hair growth, larynx/vocal cord
growth, muscle mass, etc.)
- Testosterone can be converted to the more potent _____________________________ via enzyme __________________.
This hormone is what is responsible for the primary male sexual characteristics (e.g. external genitalia).
If one abuses anabolic steroids, one of the signs is infertility. Why?
Sexual Development
The process:
-
Early embryos are in the bipotential stage, and the gonads contain both a cortex and a medulla. Sex is determined
by presence or absence of SRY gene (usually found on Y chromosome).
- The presence of SRY gene will allow the medulla to develop into testes.
o In the testes, there are two types of cells: leydig and sertoli.
o The leydig cell secretes testosterone, which is responsible for development of Wolffian duct into
accessory structures.
o In addition, testosterone may be converted to DHT via enzyme 5- -reductase. DHT is responsible for
development of male external genitalia.
o The sertoli cell secretes anti-Mullerian hormone, which degrades the Mullerian duct.
- The absence of SRY gene will allow the cortex to develop into ovaries.
o In the ovaries there are also two types of cells: theca and granulosa.
o The theca cell is equivalent to the leydig cell in males and secretes androgens (such as testosterone,
DHEA, and androstenedione).
o The granulosa cell contains the enzyme aromatase, which is used to convert androgens into
estradiol/estrogen.
What would happen if a XY embryo were missing 5--reductase?
What would happen if a XY embryo had nonfunctional androgen receptors?