The Reproductive System
The Reproductive System
Gonads are the primary sex organs
Testes in males
Ovaries in females
We start of life as bipotential (the ability to form male and/or female genitalia)
1 Gene: SRY Gee determines male or female
Default is female
Gonads produces gametes (sex cells) and secrete hormones (makes gonads endocrine glands)
Sperm are the male gametes
Ova( Eggs are the female gametes)
Determinants for male or female: If there is a smaller gamete, than it is male. If it is female, it
will produce larger gametes.
If one starts by creating larger gametes which takes more time, this one will start with the
Sexual reproduction involves the fusion of gametes from two parents resulting in genetic
variation among offspring
Takes time to find a mate
Also chance of failure
May enhance reproductive success in changing environments
Allow for variety of phenotypes
Both sexes in human
Have a set of gonads where gametes are produced Have ducts for delivery of the gonads and structures for copopulation
Male Reproductive System
Ductus (vas) deferens
External Genitalia – makes males vulnerable. External Genitalia allows processes to happen at
Covering of the testes
TunicaAlbuginea is the capsule that surrounds each testis
Septa are the extensions of the capsule that extend into the testis and divide it into lobules
Each lobule contains one to four seminiferous tubules
Tightly coiled structures
Sperm producing factors Empty sperm into rete testis (first part of the duct system)
Sperm travels through the rete testis to the epididymis
Interstitial cells in the seminiferous tubules produce androgens as testosterone
Females also produce testosterone
Ductus Deferens (Vas deferens)
Carries sperm from the epididymis to the ejaculatory duct
Passes through the inguinal canal and over the bladder
Moves sperm by peristalsis
Spermatic cord includes the ductus deferens, blood vessels, and nerves in a connective tissue
Ends in the ejaculatory duct which unites with the urethra
Expanded end in called the ampulla
Ejaculation is the smooth muscle is the walls of the ductus deferens create peristaltic waves to
squeeze sperm forward
Vasectomy occurs by cutting of the ductus deferens at the level of the testes to prevent
Extends from the base to the urinary bladder to the tip of the penis
Carries both urine and sperm
Helps because it saves space
Sperm enters from the ejaculatory duct
Regions of the urethra
Prostatic urethra – surrounded by prostate
Membranous urethra – from prostatic urethra to penis Spongy (penile) urethra – run the length of the penis
Accessory Organs help produce Semen
Semen is a mixture of sperm and accessory gland secretions from:
Located at the base of the bladder
Produces a thick, alkaline yellowish secretion (60% of semen)
Vitamin C, a potent antioxidant
Prevent free radicals
Antioxidant undoes the processes of free radicals
Protects semen from mutation
Prostaglandins promote smooth muscle contraction
Might cause worse environment
Other substances that nourish and activate sperm
Encircles the upper part of the urethra
Secretes milky fluid
Help to activate Semen Fluid enters the urethra through several small ducts
Pea-sized gland inferior to the prostate
Produces a thick, clear mucus known as pre-ejaculate
Cleanses the urethra of acidic urine
Serves as a lubricant during sexual intercourse
Secreted into the penile urethra
Divided sac of skin outside the abdomen
Maintains testes at ~3 degrees celcius lower than normal body temperature to protext sperm
Delivers sperm into the female reproductive tract
Regions of the penis
Glans penis (enlarged tip)
Prepuce (foreskin) folded cuff of skin around proximal end that may be removed by circumcision
Aboys’s testes normally develop in the abrdomen
Before birth at round 32-36 weeks, they normally descend through a flexiblte tube, called the
inguinal canal, and end up in the scrotum
Undescended testes can occur in premature boys and may be corrected with surger. External Genitalia
Internally there are three areas of spongy erectile tissue around the urethra
Erections occurs when the erectile tissue fills with blood during sexual excitement
Production of sperm cells
Begins at puberty and continues throughout life.
Occurs in the seminiferous tubules
Spermatogonia (stem cells) undergo rapid mitosis to produce more stem cells before puberty
Disadvantage: we need another set of chromosomes for a birth because we give half and the mate
gives the other half.
Follicle-stimulating hormone (FSH) modulates spermatogonia division
One cell produced is a steam cell, called a typeAdaughter cell
The other cell produced becomes a primary spermatocyte, called a type B daughter cell.
Primary Spermatocytes undergo meiosis
One primary spermatocyte produces four haploids spermatids
Spermatids have 23 chromosomes (half as much material as other body cells)
Late spermatids are produced with distinct regions: Head, midpiece, tail
Tail Sperm cells result in maturing of spermatids
Spermatogenesis ( Entire process, including spermatogenesis, the final stages) Takes 65-75 days.
Males are at any given phase at all time. It takes 65 days but every single one is one day apart.
Anatomy of the mature Sperm Cells
The only flagellated cell Head
Acrosome is a “helmet” protecting the nucleus, similar to a large lysosome which breaks down
and releases enzymes to help the sperm penetrate an egg
Midpiece wrapped by mitochondria forATP generation
Tail allows for motion, contains mitochondrion.
The more important hormones of tests
Produced by interstitial cells
During puberty, luteinizing hormone (LH) activates the interstitial cells
In turn, testosterone is produced
Function of testosterone
Stimulates reproducing organ development
Underlies sex drive
Causes secondary sex characteristics
Deepening of voice
Increased hair growth
Enlargement of skeletal muscles
Thickening of bones
If taking Anabolic Steroids
This tells your pituitary gland to stop making your own testosterone so the gonads shrink and
stop making hormones. Testes will shrink.
Your muscle growth outpaces bone growth so bone breakages occur often
Female Reproductive System:
Awoman’s ovaries contain follicles in the ovaries that nurture eggs and produce sex hormones
Oviduct (Fallopian tubes convey eggs to the uterus)
The uterus opens into vagina which receives the penis during intercourse and forms the birth
Makes sex pleasurable so that the biological standard (having the most children) can be reached
Wave of Contraction: Propel sperm in the proper direction
Role of female duct work is to accept gametes and nurture a child.
Males: Donators. Females:Acceptors
Viral Infections – linked to cancer.
Viruses are linked to uncontrolled cell growth which leads to cancer
Vaccinations are the best way to prevent viruses
Fertilization takes place in oviduct
Each follicle consist of Oocyte (immature egg)
Follicular cells surround the oocyte.
Day 1: Follicle: Cells that surround the egg.
Follicle Stimulating Hormone: Picks an egg at random from FSH
If 2 eggs are selected, they wil be known as fraternal twins Cells around the egg will grow and secrete hormones.
More Cells: More hormones to release
This leads to more estrogen to being released.
Brain sends luteinizing hormones:
Time to ovulate.
Some cells stay behind and become the corpus leutuem.
These secrete progesterone.
They are waiting fertilization and implantation.
If there is no fertilized egg: It degeneratus where the letuem degenerates
Uterine Tubes (Fallopian Tubes)
Receive the ovulated oocyte
Provide a site for fertilization
Attach to the uterus
Little or no contact between Ovaries and uterine tubues
Supported and enclosed by the broad ligament.
Because the ovaries are not connected to the fallopian tubues, fertilized eggs are possible outside
of the uterus.
Located between the Urinary Bladder and rectum
Functions of the uterus Recieves a fertilized Egg
Retains the fertilized egg
Nourishes the fertilized egg
Uterine Tube and Uterus
Fimbriae are finger-like projections at the distal end of the uterine tube that receive the oocyte
from the ovary
Cilia are located inside the uterine tube and slowly move the oocyte towards the uterus (takes 3-4
Cervix is the narrow outlet that protrudes into the vagina
Becomes vasulatized during pregnancy
Walls of the Uterus
Endometrium: Inner layer
Allows for implantation of a fertilized egg
Sloughs off if no pregnancy occurs (menses)
Endometriosis: Condition in which the tissue that behaves like the cells lining the uterus
(endometrium) grow in other areas of the body, causing pain, irregular bleeding, and possible
Changes it’s shape throughout the 28 day cycle
Myometrium is the middle layer of smooth muscle
Perimetrium (visceral peritoneum) is the outermost serous layer of the uterus.
Extends from cervix to exterior of body
Located between bladder and rectum Serves as the birth canal
Receives the penis during sexual intercourse
The hymen partially closes the vagina until the hymen is ruptured.
Fatty area overlying the pubic Symphysis
Covered with pubic hair after puberty
Labia are skin folds
Labia are skin folds
Labia majora: Hair-covered skin folds
Labia Minora: Delicate, hair-free folds of skin.
Contains erectile tissue
Corresponds to the male penis
The clitoris is similar to the penis that it is hooded by a prepuce, composed of sensitive erectile
tissue, becomes swollen with blood during sexual excitement
Removed during female circumcisions now called female genital mutilation
Urethral orifice and vaginal orifice
Great vestibular glands (bartholin’s glands.
Diamond-shaped region between the anterior ends of the labial folds, anus posteriorly, and
ischial tuberosity laterally
2 Pound baby: low chance of survival: Not full developed 10 Pound baby (overweight) – you can’t get out which is why it affects infant mortality.
Large babies come out from C-section.
Oogenesis and the Ovarian Cycle
The total supple of eggs are present at birth
Ability to release eggs begins at puberty
Reproductive ability ends at _______
Oocytes are matured in developing ovarian follicles
Oogonia are the female stem cells found in a developing fetus and no longer active by the time of
Oogonia undergo mitosis to produce primary oocytes
Primary oocytes are surrounded by cells that form primary follicles in the ovary.
Oogenesis and the Ovarian Cycle
Primary oocytes are inactive until puberty
Follicle stimulating hormone (FSH) causes some primary follicles to mature each month
Cyclic month changes constitute the ovarian cycle
Meiosis restarts inside maturing follicle
Produces a secondary oocyte and the first polar body
Follicle Development to the stage of a vesicular follicle takes about 14 days
Ovulation of a secondary oocyte occurs with the release of luteinizing hormone (LH)
Secondary Oocyte is released and surrounded by a corona radiata and zona pellucida.
Meiosis is completed after ovulation only if sperm penetrates Ovum is produced
Two additional polar bodies may be produced
Once ovum is formed, the 23 Chromosomes can be combined with those of the sperm to form
the fertilized egg (zygote)
If the secondary oocyte is not penetrated by a sperm, it dies and does not complete meiosis to
form an ovum.
Polar Bodies: Extra chromosomes that we get rid of.
We throw away the chromosomes into the polar bodies
Females only have primary oocytes
Have meiosis 1 and forma polar body
When Meiosis II of polar Body
May or May not occur because no one has actually studied it. No one needs to study because it
has no effect on physiology.
Spermatogonium vs. Oogonium
Men: Have bunches of sperm factories. Factories always active.
Not very large. Just DNA.
No real stimulus to complete this process.
Females: Females only have primary oocytes.
One per month: Primary oocyte becomes secondary oocyte.
Polar body dumps the left over chromosomes
Second polar body forms only if you aren’t fertilized?
It disintegrates if there is fertilization
Hormones: The ovarian cycle includes changes in the ovary that occur about every 28 days
The menstrual/uterine cycle involves changes that occur in the uterus.
Spike in Luteinizing hormone means: Women will ovulate
Hormone that say we’re waiting for fertilization: Progesterone.
Keeps the uterine lining where it is.
New lining is formed by sloughing off the old ones.
Follicular Phase is similar to the proliferating phase.
Luteal Phase: Waits for the fertilized egg.
Females have difefering hormones levels while men have a steady level of testosterone.
Ovarian Follicle Stages
Primary Follicle contains an immature oocyte
Graafian (vesicular) follicle is the growing follicle with a maturing oocyte
Ovulation occurs when the egg is mature, the follicle ruptures; occurs about every 28 days.
The ruptured follicle is transformed into a corpus Luteum.
Hormonal Events before ovulation
They hypothalamus signals the anterior pituitary to secrete FSH and LH
FSH triggers thr growth of a follicle
AS the follicle grows, it