The Reproductive System
Dr. Anderson
GCIT
Asexual vs. Sexual Reproduction
• Many organisms clone themselves to produce
more offspring (progeny) and therefore have no
need for the exchange of gametes (sex cells)
• However, many organisms (including humans)
have evolved to reproduce sexually
• What are the advantages of each form of
reproduction?
Reproductive System
• Only system that is broadly different between
genders
• Also the only system whose anatomy is meant
to compliment that of the opposite gender
• Male – largely external
• Female – largely internal
Reproductive System - Function
• To produce, maintain and deliver gametes to
the uterus where they can combine for
fertilization
Male vs. Female Anatomy
Tissue Type
Male
Female
Gametes
Sperm
Egg
Gonads
Testes
Ovaries
Copulatory
Organ
Accessory
Organs
Penis
Vagina
Mammary
Glands
Male Anatomy
Male Anatomy
• Much of the male
anatomy, including the
gamete-producing
organs are outside of
the body
– Why?
Male Anatomy
• Testes –
– produce sperm via
meiosis
– Also secrete the hormone
testosterone
• Protected by the scrotum
– Cremaster muscle
regulates the tension and
therefore temperature of
scrotum
– Why is this important?
The Testes
• Consist of
spermatogenic cells
(sperm producing cells)
in tubules called the
seminiferous tubules
• Once-produced, sperm
migrate to the
epididymis, where they
are stored until
ejaculation
Testis Anatomy
Spermatic Cord –
contains nerve,
blood vessels, and
efferent ducts that
serve the cells of
the testes
Vas Deferens
• During ejaculation, sperm
are released from the
epididymis via the vas
deferens
– Vas deferens is cut during
a vasectomy
• The vas deferens empties
into the urethra to give
passage to sperm
Prostate
• Gland in which the vas
deferens and urethra
combine
• Add alkaline fluid to
semen prior to
ejaculation
– Why?
• One of the most
common cancers in
older men
Accessory Glands
• Seminal Vesicles – paired
exocrine glands that empty
into each vas deferens
• Add a variety of compounds
to semen
– Vitamin C
– Fructose
– Proteins
– Why?
Penis
• Copulatory organ in males
• Composed mainly of spongy tissue that fills
with blood to produce an erection during sex
Flaccid vs.Erect
• Parasympathetic
nerves relax during
sexual stimulation,
allowing blood to
expand arterioles and
erectile tissue
– Corpora cavernosa
Semen
• A mixture of
– Sperm
– Accessory gland secretions
• Stimulates reverse peristalsis of the uterus
• Slightly alkaline
• Immunosupressive
– Adaptive?
Ejaculation
• Spinal reflex
• Bladder sphincter contracts
• Accessory glands and ducts and the penis
muscles contract, propelling semen out
Spermatogenesis
• End product of meiosis!
Body (somatic) cells
Sperm (or egg) cells
Spermatogenesis
• Spermatocyte cells go through mieosis to produce immature 4
sperm cells (spermatids)
• Flagella are produced and much of the cytoplasm is lost
• Sperm are “streamlined” for their trip to meet the egg
The Female Anatomy
Function
• The female
reproductive system is
more complex than
the male system
because:
– Used for copulation
– Must support the
growth and
development of the
baby for 9 months!
Internal Anatomy
Ovaries
• Ovaries
– paired organs that flank either side of the uterus
– produce one (usually) egg per month (~28 days)
• Ovaries also regulate the menstrual cycle via
hormone release
– Progesterone
– Estrogen
Ovarian Follicles
• Egg cells (oocytes) are formed in the ovarian
cortex
• The follicles mature (eggs “ripen”) in each
follicle over time
• Eventually one follicle ejects its oocyte,
leaving behind a “corpus luteum”, which
produces hormones (progesterone and
estrogen)
Oocyte Development
Ovulation
• Eggs are released into the
peritoneal (abdominal) cavity
• The ampullae of the fallopian
tubes collect the newly
released egg
– Where fertilization most often
occurs
• The brush-like fimbriae bear
cilia which sweep the egg into
the fallopian tube (most times)
Fallopian Tubes
• Transport egg from the ovary to the uterus
– Ciliated cells
– Smooth muscle contractions (peristalsis)
Ectopic Pregnancy
• Sometimes, a
fertilized egg will
implant in the wall of
the fallopian tube and
an embryo will start
to grow
– Generally results in
loss of pregnancy
(either naturally or
with surgery)
Pelvic Inflammatory Disease (PID)
• Fallopian tubes are open
superiorly
• Therefore, bacteria
(Gonorrhea) may get
swept into the peritoneal
cavity
– Scarring of fallopian tubes
– Major cause of female
sterility
Uterus
• Anterior to rectum and posterior to bladder, about the size of a pear
• From where it connects with the vagina, it flexes anteriorly
(anteverted)
Uterus
• Rounded superior region (fundus)
• Cervix – joins the uterus with the vagina
Uterine Wall
• Three layers
– Perimetrium – outermost layer
– Myometrium – Muscular layer (smooth muscle)
– Endometrium – internal, epithelial layer
• Sloughed off during menstruation
• Tissue that accepts the fertilized egg (zygote)
Cervix
• The inferior opening to
the uterus
• Secretes viscous mucus
which serves as a barrier
to pathogens and sperm
– Viscosity greatly decreases
peri-ovulation
HPV – Cervical Cancer
• Human Papilloma virus – 60
subtypes
• At least four (probably more)
of these are known to be
associated with cervical
cancer
HPV and Cervical Cancer
• How women can protect themselves
– Gardasil
– Regular visits to gynecologist if sexually active to
check for abnormal cervical cells
• Pap smear
Vagina (Internal)
• 3-4 inches long, very thin,
flexible tissue
• Also three layers
– Elastic outer layer
– Smooth muscle (muscularis)
– Inner mucosal layer
• Acidic due to glycogen
release
Vagina (External)
• Hymen – forms
incomplete partition over
vaginal orifice (in virgins)
• Labia – skin folds that
flank and protect the
vaginal opening
• Clitoris – nerve-filled,
erectile structure; primary
organ of sexual sensation
Mammary Glands
• Milk producing glands
that develop at puberty
• 15-25 exocrine lobes
produce milk soon after
birth of a child (prolactin
is secreted)
• Negative feedback loop
limits milk production
– Disuse halts production
Breast Cancer
• Risks
–
–
–
–
Early menstruation (menarche)
No or late pregnancies
No or reduced breast feeding
Family history
• Possessing the BRCA1 or BRCA2 genes (10% of American women)
Breast Cancer Prevention
• Self-examination –
palpating the breast
tissue for tumors
(lumps)
• Mammogram – x-ray
of breast tissue
• Genetic screening –
testing for BRCA1 or
BRCA2 genes