HUMAN REPRODUCTION BIOLOGY 269. Female Reproductive System. Produce hormones (estrogen and progesterone) for secondary sexual characteristics. Produce one large oocyte at regular intervals and release it in such a way that it enters the oviduct (“Fallopian tube”,“uterine tube”).
Located within pelvis, 2 to 5 cm (1 to 2 inches) lateral to the uterus
Approximately 3cm x 2cm x 1cm
Central region, or “medulla”, consists of connective tissue with many blood vessels.
Outer region, or “ ”, has all of the oocytes. One or two of these oocytes may be developing before ovulation; undeveloped ones are stored here.
Also contains the remnant from the previous cycle’s ovulation, called a
“ “ , which secretes progesterone to keep uterus ready for implantation of the embryo
During oogenesis, the oocyte is surrounded by follicular cells granulosa cells in one or more layers, forming a .
All formed before birth - hundreds in each ovary
Have not yet begun development – remain dormant until puberty
Consists of primary oocyte surrounded by a single layer
of flat follicular cells
Develop only after puberty; 3 to 4 enter this stage each cycle
No change in primary oocyte
Follicle has begun development – cells are larger
1 or 2 primary follicles progress to this stage each cycle
Primary oocyte larger, finishes first division of meiosis to become a secondary oocyte, also forming a polar body.
Follicle grows larger as follicular cells divide to form many layers; spaces begin to develop in center of follicle
Most follicles which made it to “secondary” will reach this stage
Follicle is very large; Many layers of cells surrounding fluid-filled center called antrum
Secondary oocyte covered with thick, clear membrane called zona pellucida; pushed to one side in follicle and surrounded by mass of follicular cells called cumulus oophorus
Oogenesis, as well as ovulation and many other things, is regulated by the pituitary gland, which lies just below the brain
Oogenesis and growth of the follicle in the ovary are initiated and stimulated by from the pitutitary
During this oogenesis under the stimulation of FSH, follicular cells surrounding the oocyte secrete the hormone , which stimulates the inner lining of the uterus to thicken and begin secreting mucus, getting ready for pregnancy
This estrogen from the follicular cells also inhibits the pituitary gland from secreting any more FSH.
Thus, no more follicles will be stimulated to develop until it stops.
The secondary oocyte, surrounded by the zona pellucida and cumulus oophorus, is released from the surface of the ovary, where it can be captured by the open end of the oviduct.
The cumulus oophorus now called the corona radiata.
Ovulation is triggered when the pituitary gland secretes a different hormone, called .
Luteinizing hormone also causes the follicular cells of the now empty follicle to develop into a
. This structure secretes the hormone
Before ovulation: FSH stimulates cells of follicle to secrete , which stimulates the lining of the uterus to develop.After ovulation: LH stimulates cells of the corpus luteum to secrete , which maintains the uterine lining in this “ready for pregnancy” condition
If fertilization and pregnancy occur, the placenta of the embryo secretes a hormone called , which stimulates the corpus luteum to keep secreting progesterone, which in turn keeps the lining of the uterus thick and full of blood vessels.
If fertilization and pregnancy do not occur, after a few days the corpus luteum deteriorates and stops producing progesterone. Without its stimulus, the uterus can not maintain its thick lining, so this falls off and is shed as menstruation.
When the oocyte is released from the surface of the ovary during ovulation, it is picked up by the oviduct, or Fallopian Tube, a hollow muscular tube which leads from near the uterus to the ovaries.
Lateral End: Wide opening, or , surrounds the surface of the ovary. The edge is surrounded by finger-like .
Middle Part: Wide
Medial End: Narrow
leads into uterus. Cavity of oviduct is continuous with cavity of uterus
The oviduct moves the oocyte toward the uterus
The oviduct moves sperm away from the uterus
Fertilization occurs in ampulla of oviduct, forming the zygote, which goes through repeated mitotic cell divisions to eventually form the embryo.
Oviduct moves this growing mass of pre-embryo cells toward uterus: takes 3 or 4 days.
Secretions from oviduct are necessary to keep sperm, oocyte, and embryo alive.
Anterior to rectum; Posterior & superior to bladder
Narrowed inferiorly to form cervix, which projects into vagina
Outer layer = : Thick layer of muscle
Inner layer = :Lots of glands & blood vessels
Two layers of endometrium:
: Closer to myometrium; Remains after menstruation; Regrows functional layer
: Closer to cavity; Thickens every cycle; Embryo implants here during pregnancy; Dies and falls off during menstruation
Inferior end narrows to form , which projects down into vagina
Immediately before menstruation: 100 – 150 grams
Immediately after end of menstruation: 50 – 100 grams
End of pregnancy: 1,000 – 1,500 grams
At end of pregnancy:
Uterus extends from vagina inferiorly to bottom of sternum superiorly
Lies anterior to all other abdominal organs except bladder
Inferior to uterus;
Anterior to rectum
Posterior to bladder & urethra
Receives penis and semen during sexual intercourse
Passage for delivery of fetus or menstrual flow
The vagina opens between
into a space called the
Outside of those are the
At the anterior junction of the
outer labia is the
clitoris which is visible externally
is only a small part of this organ.
Two shafts of erectile tissue
extend backwards along the
pelvic floor on either side of
the urethra and vagina.