The external female genitalia are collectively called the vulva. The vagina is the pathway into and out of the uterus. The man’s penis is inserted into the vagina to deliver sperm, and the baby exits the uterus through the vagina during childbirth.
The ovaries produce oocytes, the female gametes, in a process called oogenesis. As with spermatogenesis, meiosis produces the haploid gamete (in this case, an ovum); however, it is completed only in an oocyte that has been penetrated by a sperm. In the ovary, an oocyte surrounded by supporting cells is called a follicle. In folliculogenesis, primordial follicles develop into primary, secondary, and tertiary follicles. Early tertiary follicles with their fluid-filled antrum will be stimulated by an increase in FSH, a gonadotropin produced by the anterior pituitary, to grow in the 28-day ovarian cycle. Supporting granulosa and theca cells in the growing follicles produce estrogens, until the level of estrogen in the bloodstream is high enough that it triggers negative feedback at the hypothalamus and pituitary. This results in a reduction of FSH and LH, and most tertiary follicles in the ovary undergo atresia (they die). One follicle, usually the one with the most FSH receptors, survives this period and is now called the dominant follicle. The dominant follicle produces more estrogen, triggering positive feedback and the LH surge that will induce ovulation. Following ovulation, the granulosa cells of the empty follicle luteinize and transform into the progesterone-producing corpus luteum. The ovulated oocyte with its surrounding granulosa cells is picked up by the infundibulum of the uterine tube, and beating cilia help to transport it through the tube toward the uterus. Fertilization occurs within the uterine tube, and the final stage of meiosis is completed.
The uterus has three regions: the fundus, the body, and the cervix. It has three layers: the outer perimetrium, the muscular myometrium, and the inner endometrium. The endometrium responds to estrogen released by the follicles during the menstrual cycle and grows thicker with an increase in blood vessels in preparation for pregnancy. If the egg is not fertilized, no signal is sent to extend the life of the corpus luteum, and it degrades, stopping progesterone production. This decline in progesterone results in the sloughing of the inner portion of the endometrium in a process called menses, or menstruation.
The breasts are accessory sexual organs that are utilized after the birth of a child to produce milk in a process called lactation. Birth control pills provide constant levels of estrogen and progesterone to negatively feed back on the hypothalamus and pituitary, and suppress the release of FSH and LH, which inhibits ovulation and prevents pregnancy.
alveoli
(of the breast) milk-secreting cells in the mammary gland
ampulla
(of the uterine tube) middle portion of the uterine tube in which fertilization often occurs
antrum
fluid-filled chamber that characterizes a mature tertiary (antral) follicle
areola
highly pigmented, circular area surrounding the raised nipple and containing areolar glands that secrete fluid important for lubrication during suckling
Bartholin’s glands
(also, greater vestibular glands) glands that produce a thick mucus that maintains moisture in the vulva area; also referred to as the greater vestibular glands
body of uterus
middle section of the uterus
broad ligament
wide ligament that supports the uterus by attaching laterally to both sides of the uterus and pelvic wall
cervix
elongate inferior end of the uterus where it connects to the vagina
clitoris
(also, glans clitoris) nerve-rich area of the vulva that contributes to sexual sensation during intercourse
corpus albicans
nonfunctional structure remaining in the ovarian stroma following structural and functional regression of the corpus luteum
corpus luteum
transformed follicle after ovulation that secretes progesterone
endometrium
inner lining of the uterus, part of which builds up during the secretory phase of the menstrual cycle and then sheds with menses
fimbriae
fingerlike projections on the distal uterine tubes
follicle
ovarian structure of one oocyte and surrounding granulosa (and later theca) cells
folliculogenesis
development of ovarian follicles from primordial to tertiary under the stimulation of gonadotropins
fundus
(of the uterus) domed portion of the uterus that is superior to the uterine tubes
granulosa cells
supportive cells in the ovarian follicle that produce estrogen
hymen
membrane that covers part of the opening of the vagina
infundibulum
(of the uterine tube) wide, distal portion of the uterine tube terminating in fimbriae
isthmus
narrow, medial portion of the uterine tube that joins the uterus
labia majora
hair-covered folds of skin located behind the mons pubis
labia minora
thin, pigmented, hairless flaps of skin located medial and deep to the labia majora
lactiferous ducts
ducts that connect the mammary glands to the nipple and allow for the transport of milk
lactiferous sinus
area of milk collection between alveoli and lactiferous duct
mammary glands
glands inside the breast that secrete milk
menarche
first menstruation in a pubertal female
menses
shedding of the inner portion of the endometrium out though the vagina; also referred to as menstruation
menses phase
phase of the menstrual cycle in which the endometrial lining is shed
menstrual cycle
approximately 28-day cycle of changes in the uterus consisting of a menses phase, a proliferative phase, and a secretory phase
mons pubis
mound of fatty tissue located at the front of the vulva
myometrium
smooth muscle layer of uterus that allows for uterine contractions during labor and expulsion of menstrual blood
oocyte
cell that results from the division of the oogonium and undergoes meiosis I at the LH surge and meiosis II at fertilization to become a haploid ovum
oogenesis
process by which oogonia divide by mitosis to primary oocytes, which undergo meiosis to produce the secondary oocyte and, upon fertilization, the ovum
oogonia
ovarian stem cells that undergo mitosis during female fetal development to form primary oocytes
ovarian cycle
approximately 28-day cycle of changes in the ovary consisting of a follicular phase and a luteal phase
ovaries
female gonads that produce oocytes and sex steroid hormones (notably estrogen and progesterone)
ovulation
release of a secondary oocyte and associated granulosa cells from an ovary
ovum
haploid female gamete resulting from completion of meiosis II at fertilization
perimetrium
outer epithelial layer of uterine wall
polar body
smaller cell produced during the process of meiosis in oogenesis
primary follicles
ovarian follicles with a primary oocyte and one layer of cuboidal granulosa cells
primordial follicles
least developed ovarian follicles that consist of a single oocyte and a single layer of flat (squamous) granulosa cells
proliferative phase
phase of the menstrual cycle in which the endometrium proliferates
rugae
(of the vagina) folds of skin in the vagina that allow it to stretch during intercourse and childbirth
secondary follicles
ovarian follicles with a primary oocyte and multiple layers of granulosa cells
secretory phase
phase of the menstrual cycle in which the endometrium secretes a nutrient-rich fluid in preparation for implantation of an embryo
suspensory ligaments
bands of connective tissue that suspend the breast onto the chest wall by attachment to the overlying dermis
tertiary follicles
(also, antral follicles) ovarian follicles with a primary or secondary oocyte, multiple layers of granulosa cells, and a fully formed antrum
theca cells
estrogen-producing cells in a maturing ovarian follicle
uterine tubes
(also, fallopian tubes or oviducts) ducts that facilitate transport of an ovulated oocyte to the uterus
uterus
muscular hollow organ in which a fertilized egg develops into a fetus
vagina
tunnel-like organ that provides access to the uterus for the insertion of semen and from the uterus for the birth of a baby
vulva
external female genitalia
Watch this video to observe ovulation and its initiation in response to the release of FSH and LH from the pituitary gland. What specialized structures help guide the oocyte from the ovary into the uterine tube?
The fimbriae sweep the oocyte into the uterine tube.
Watch this series of videos to look at the movement of the oocyte through the ovary. The cilia in the uterine tube promote movement of the oocyte. What would likely occur if the cilia were paralyzed at the time of ovulation?
The oocyte may not enter the tube and may enter the pelvic cavity.
1. What are the female gonads called?
A. oocytes
B. ova
C. oviducts
D. ovaries
D
2. When do the oogonia undergo mitosis?
A. before birth
B. at puberty
C. at the beginning of each menstrual cycle
D. during fertilization
A
3. From what structure does the corpus luteum originate?
A. uterine corpus
B. dominant follicle
C. fallopian tube
D. corpus albicans
B
4. Where does fertilization of the egg by the sperm typically occur?
A. vagina
B. uterus
C. uterine tube
D. ovary
C
5. Why do estrogen levels fall after menopause?
A. The ovaries degrade.
B. There are no follicles left to produce estrogen.
C. The pituitary secretes a menopause-specific hormone.
D. The cells of the endometrium degenerate.
B
6. The vulva includes the ________.
A. lactiferous duct, rugae, and hymen
B. lactiferous duct, endometrium, and bulbourethral glands
C. mons pubis, endometrium, and hymen
D. mons pubis, labia majora, and Bartholin’s glands
D
1. Follow the path of ejaculated sperm from the vagina to the oocyte. Include all structures of the female reproductive tract that the sperm must swim through to reach the egg.
The sperm must swim upward in the vagina, through the cervix, and then through the body of the uterus to one or the other of the two uterine tubes. Fertilization generally occurs in the uterine tube.
2. Identify some differences between meiosis in men and women.
Meiosis in the man results in four viable haploid sperm, whereas meiosis in the woman results in a secondary oocyte and, upon completion following fertilization by a sperm, one viable haploid ovum with abundant cytoplasm and up to three polar bodies with little cytoplasm that are destined to die.
3. Explain the hormonal regulation of the phases of the menstrual cycle.
As a result of the degradation of the corpus luteum, a decline in progesterone concentrations triggers the shedding of the endometrial lining, marking the menses phase of the menstrual cycle. Low progesterone levels also reduce the negative feedback that had been occurring at the hypothalamus and pituitary, and result in the release of GnRH and, subsequently, FSH and LH. FSH stimulates tertiary follicles to grow and granulosa and theca cells begin to produce increased amounts of estrogen. High estrogen concentrations stimulate the endometrial lining to rebuild, marking the proliferative phase of the menstrual cycle. The high estrogen concentrations will eventually lead to a decrease in FSH because of negative feedback, resulting in atresia of all but one of the developing tertiary follicles. The switch to positive feedback that occurs with elevated estrogen production from the dominant follicle stimulates the LH surge that will trigger ovulation. The luteinization of the granulosa cells of the collapsed follicle forms the progesterone-producing corpus luteum. Progesterone from the corpus luteum causes the endometrium to prepare for implantation, in part by secreting nutrient-rich fluid. This marks the secretory phase of the menstrual cycle. Finally, in a non-fertile cycle, the corpus luteum will degrade and menses will occur.
4. Endometriosis is a disorder in which endometrial cells implant and proliferate outside of the uterus—in the uterine tubes, on the ovaries, or even in the pelvic cavity. Offer a theory as to why endometriosis increases a woman’s risk of infertility.
Endometrial tissue proliferating outside of the endometrium—for example, in the uterine tubes, on the ovaries, or within the pelvic cavity—could block the passage of sperm, ovulated oocytes, or a zygote, thus reducing fertility.