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The Reproductive System

Male Reproductive System

Male Reproductive System
• The male gonads (testes) produce sperm and lie
within the scrotum
• Sperm are delivered to the exterior through a
system of ducts: epididymis  ductus deferens
 ejaculatory duct urethra
• Accessory sex glands:
– Empty their secretions into the ducts during
ejaculation
– Include the seminal vesicles, prostate gland, and
bulbourethral glands

The Scrotum

Figure 27
...

• Spermatic Cord: enclose nerves and blood
vessels
• The Testes are kept 3C lower than core body
temperature (needed for sperm production)
controlled by:
• Cremaster muscle
– When it is cold it contracts pulling
the testes up toward the core of the
body
...


The Testes

Seminiferous Tubules
– Produce the sperm
– Surrounding the
seminiferous tubules
are interstitial cells that
produce Testosterone

The Epididymis
– Sperm enter the epididymis were excess testicular
fluid is absorbed and nutrients are provided to the
sperm to enable them become motile
– Upon ejaculation the epididymis contracts, expelling
sperm into the ductus (VAS) deferens
...

Penile arteries dilate which causes the erectile
tissue corpora cavernosa to compress the
penile veins draining the penis
...
Muscles of the pelvic floor
and accessory glands(seminal vesicles,
prostate gland, bulbourethral glands) contract
secreting the contents out the urethra as
semen
...

They functions to:
– and secrete 60% of the volume of semen
– Semen – viscous alkaline fluid containing:
• fructose: fuel for the road trip
• prostaglandins which stimulate reverse peristalsis
in the uterus
• ascorbic acid

Accessory Glands
• Prostate Gland
– Doughnut-shaped gland that encircles part of the
urethra inferior to the bladder
– Plays a major role in the activation of sperm
– accounts for one-third of the semen volume
– Its milky, slightly acid fluid, which contains citrate,
enzymes, and prostate-specific antigen (PSA),
• Acts as a anticoagulant for sperm
...
The following are associated with elevated levels:
– Prostate cancer, prostatitis and BPH

• Bulbourethral Glands (Cowper’s Glands)
– Pea-sized glands inferior to the prostate
– Produce thick, clear mucus prior to ejaculation that neutralizes
traces of acidic urine in the urethra

Hormonal Regulation of
Testicular Function
• The hypothalamus releases gonadotropin-releasing
hormone (GnRH)
• GnRH stimulates the anterior pituitary to secrete FSH and
LH
– FSH causes sustentacular cells ( Nurse) to release androgenbinding protein (ABP) and inhibin
...


Additional Effects of Testosterone
• Prostate – converts Testosterone into dihydrotestosterone (DHT) before it
can bind within the nucleus
...

• Symptoms of testosterone deficiency:
• Increased risk of insulin resistance and DM:
• Increased visceral obesity: increases activity of the enzyme
aromatase which can convert testosterone into estrogen
...

• Extending from the
cervix to the exterior of
the body
...


Uterus
• Hollow, thick-walled
organ located in the
pelvis anterior to the
rectum and
posterosuperior to the
bladder
• Body – major portion of
the uterus
• Fundus – rounded
region superior to the
entrance of the uterine
tubes
• Cervix- distal tip
contacts the vagina
...

• Expand distally around
the ovary forming the
ampulla
• The ampulla ends in the
funnel-shaped, ciliated
infundibulum containing
fingerlike projections
called fimbriae
...

• Located within the pelvic cavity on either side of the uterus
• Each ovary contains primordial follicles consisting of an oocyte
and follicular cells
...

These hormones collectively stimulate the growth and
maturation of the oocyte within the follicle
...

– LH stimulates estrogen secretion promoting the growth of the
endometrium and development of the fluid filled antrum characteristic in
a mature graafian follicle
...

If pregnancy does occur, the corpus luteum will continue to produce these
hormones until the placenta takes over at about 3 months
...

• Will increase in size during the
first half of the menstrual cycle
...

• Cleavage – a series of mitotic divisions occur for 3 days after
fertilization forming a morula stage (solid ball of cells)
• Zona pellucida disintegrates to release a fluid-filled hollow sphere
called a Blastocyst
– outer cells (trophoblast) helps to form placenta
– inner cell mass develops into embryo
• Ectoderm – forms structures of the nervous system and
skin epidermis
...

• Mesoderm – forms muscles and various connective tissues
• Implantation of Blastocyst occurs around day 6
...
17

Lactation
• During pregnancy estrogen and progesterone high levels
stimulate the hypothalamus to secrete prolactinreleasing hormone (PRH) which targets the anterior
pituitary
...
(autosomes)
• Sex cells (gametes) from the ova and the sperm
each has 1 chromosome that determine the sex
• Sperm and egg contain only 23 chromosomes n (
haploid)
– fertilized egg has diploid number of
chromosomes

Sex Determination of Offspring

Karyotype of What Sex ?

Questions???



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