BSI 2 LEC 56: Male Reproductive System
Terms in this set (48)
The testosterone surge necessary to express the ♂sexual organs/♂phenotype during pregnancy is due to the placenta secreting ____ ____ _____.
Human Chorionic Gonadotrophin, (hCG), which acts like LH on the Leydig cells of the fetal testes causing them to produce testosterone.
Sperm which are the ♂ gametes are produced in the ________ tubules of the testes.
What is the pathway of sperm?
From the seminiferous tubules the sperm → epididymis which is ~ 6 meters long → Vas deferens/Ampulla of vas deferens → ejaculatory duct → urethra.
What is the importance of the prostate, seminal vesicles and bulbourethral, (Cowper's glands) in sperm maturation?
They add their necessary secretions so ensuring viability of the sperm.
Spermatogenesis is the production of the ♂ ________ sperm.
T or F? In the embryo, primordial germ cells migrate into the testes and develop into spermatogonia in the outer layers of the seminiferous tubules where they begin to develop into sperm.
False, they remain there until puberty when they complete meiosis due to the stimulation by the anterior pituitary gonadotropic hormones FSH and LH.
Describe the steps in spermatogenesis.
The entire spermatogenesis process takes ~ ___ days and now each sperm carries either an "X" or "Y" chromosome which will determine the gender of the offspring.
T or F? The "head" contains the diploid ♂ DNA and the acrosome which aids egg penetration, the "midpiece" principally mitochondria for ATP production to power the flagellum, ("tail").
False, haploid not diploid.
the acrosome which is formed from the Golgi apparatus and contains lysosomal-like enzymes including ____ and _______ necessary for egg penetration.
LH from the anterior pituitary, (controlled by GnRH [+] secretion by the hypothalamus), is required to stimulate what cells to produce testosterone?
from the interstitial Leydig cells
between the seminiferous tubules
is essential for growth and development of spermatogonia at what stage of spermatogenesis?
The first stage of spermatogenesis.
FSH from the anterior pituitary, (again controlled by GnRH [+] secretion by the hypothalamus), is required to activate the ______ _____ for the final stage of spermatogenesis when spermatids → sperm.
Estrogens formed from _____ by the Sertoli cells also due to FSH secretion are probably also essential to complete spermatogenesis.
_____ is necessary for the correct metabolic environment particularly during the early stages of spermatogenesis.
c. GH (Growth Hormone)
What is important for sperm motility?
as found in the ejaculated fluid
y*: acidic pH's ↓activity or even kill sperm (must neutralize the vagina's antibacterial ↓pH also).
Why are the testes outside of the body?
a. Increase the shelf-life of sperm
c. To differentiate between sexes
d. To increase motility of sperm
e. Study for drug mech
a. Increase the shelf-life of sperm. [An ↑temperature also ↑activity but consequently shortens the viable life of the sperm, (exhaustion)]
Seminal vesicles are composed of
cells that secrete a mucoid fluid containing what?
Fructose, citric acid, and other nutrients
plus significant quantities of
PG's and fibrinogen
: during ejaculation the seminal vesicles secrete into the ejaculatory duct immediately after the sperm.
How does PG's aid in fertilization?
1. Reacting with cervical mucus to aid sperm movement and penetration.
2. Causing reverse peristaltic waves, (normally "outwards"), in the uterus and fallopian tubes so helping the sperm reach the egg.
What gland secretes a milky fluid containing
Ca2+, citrate, phosphate, clotting factor and profibrinolysin
and why is it important?
The prostate gland. This secretion helps by ↑pH of both the ejaculated fluid and the vagina which normally has an acidic pH.
How do the Bulbourethral glands (Cowper's) contribute to the ejaculant?
Only contribute ~5% of ejaculant, principally mucoproteins for lubrication and to ↑pH.
T or F? Majority of the semen ejaculated is composed of the sperm and fluid from the vas deferens.
False. The semen ejaculated is composed of the sperm and fluid from the vas deferens, (~ 10% of total), seminal vesicle secretions, (~ 60%), prostate secretions, (~ 30%), plus a small quantity of mucus:
bulk of fluid is from the seminal vesicles
helps wash the sperm out of the ejaculatory duct and urethra.
What is the significance of the clotting factor and the fibrinogen in semen?
They cause weak coagulation of fluid to hold the sperm in the vagina; after ~ 15-30 minutes this dissolves due to the action of the fibrinolysin.
What is capacitation?
The changes undergone by sperm in the female reproductive tract that enables them to penetrate and fertilize an egg.
Before ejaculation, the acrosomal membrane is quite tough due to extra _________ being incorporated: once in the ♀ this is also lost and the weakening of this membrane helps in penetration.
cholesterol. [additionally, this membrane develops an
↑Ca2+ permeability which in turn ↑activity of the flagellum
so enhancing motility: the
↑[Ca2+]i triggers the release of acrosomal enzymes necessary for egg penetration
What the processes of fusion between the sperm and egg?
What does the sperm have to get pass in order to penetrate the egg?
The corona radiata composed of granulosa cells, the Zona pellucida (glycoprotein layer) that surrounds the egg itself:.
What happens when the sperm reaches the Zona pellucida?
Specific binding occurs, (similar to "cell-cell" contact/remember "Notch" signaling: see previously), which
triggers the release of all acrosomal enzymes which create a pathway for the sperm head
What are some causes of Abnormal Spermatogenesis?
● Damaged seminiferous tubule epithelium:
, (testicular infection)
mumps, Scarlet fever, or Pneumonia
● Cryptorchidism is the failure of the testes to descend into the scrotum just prior to birth.
● Sometimes men are infertile despite normal sperm counts and this is often due to abnormal sperm.
What causes vasodilation of the penile arteries and subsequent engorgement of the large sinuses in the penis such as the Corpus cavernosum causing an erection
PNS nerves, (visceral motor), release principally Nitric Oxide.
The "money shot" is primarily due to SNS activity
and the contractions of which associated glands?
Vas deferens and urethra so propelling the semen out.
Androgens are any steroid that a masculinizing effect are synthesized from __________________ and is secreted on demand..
T or F? Testosterone and dihydrotestosterone are synthesized from Leydig cells.
False, only Testosterone is. Most, however, is converted to the
more active Dihydrotestosterone
in target tissues,
What are androgens bound to in circulation?
They are bound to plasma proteins,
beta-globulin sex hormone-binding globulin.
What happens to unbound testosterone?
They are rapidly
metabolized by the liver
androsterone and dehydroepiandrosterone
conjugated to either glucuronide or sulfate
via bile or the kidneys
T or F? Virtually no testosterone is produced in prepubescents.
False, virtually non-existent during childhood but a significant number are present in newborns, secreting sufficient testosterone for the development of the ♂ sexual organs.
What causes secretion or inhibition of testoterone in males?
T or F? LH and FSH are steroids that affect the gonads to produce testosterone.
False, LH and FSH are peptides acting on mech 2 via cAMP.
What is Inhibin and when is it produced?
If spermatogenesis is proceeding too fast, Sertoli cells produce the hormone Inhibin which
strongly and specifically
inhibits the anterior pituitary to
selectively ↓FSH secretion
How are secretion of GnRH affected?
Affected by behavioral factors especially from the limbic system: stress in particular ↓function, (cortisol).
What gene causes differentiation of Sertoli and Leydig cells
Expression of the ♂ phenotype depends on the presence/expression of the SRY gene on the Y chromosome
T or F? Testosterone causes the so-called Wolffian ducts to transform into the testes, penis, scrotum and prostate.
Testosterone causes the so-called Wolffian ducts to transform into the testes
penis, scrotum and prostate also develop but under the influence of dihydrotestosterone
formed from testosterone.
Most of testosterone's actions are due to _____ _______.
How is testosterone converted to dihydrotestosterone?
Testosterone is converted → dihydrotestosterone by the enzyme 5alpha-reductase in the prostate intracellularly.
What can cause Abnormalities of ♂ Sexual Function?
: benign fibroadenomas, actual prostate cancer
Mutated Androgen Receptors
of Leydig Cells
of germinal epithelium
________ occurs if the testes are non-functional and do not secrete testosterone: neither ♂sex organs or characteristics form but instead ♀sex organs develop, ("default" gender: ♂genotype but ♀phenotype.
Hypogonadism. This can also be caused by the inherited
inability of the hypothalamus to secrete GnRH
Isolated GnRH Deficiency (IGD)
Testicular tumors/tumors of the Leydig cells can occur and secrete enormous amounts of testosterone. What can this cause?
In adolescents: ↓height due to premature epiphyses fusion. ↑sex organs, skeletal muscle, and 2o sexual characteristics.
Tumors of the _____ _______can develop into almost any type of tissue including placental and typically form a mass called a
which sometimes secretes significant amounts of hCG occasionally these tumors secrete estrogens causing the condition Gynecomastia.