Lecture 15 Flashcards
Ovarian Cycle
- Follicular phase
- Ovulation
- Luteal phase
Follicular phase
Days 1-14
Batch of primary follicles develop in response to FSH •Stimulates growth and release of estradiol
By time antrums begin to develop (in secondary follicles) one follicle in particular is selected to become mature follicle•In response to estradiol, dominant follicle upregulates FSH and LH receptors
High estradiol levels cause anterior pituitary to secrete less FSH (causing all follicles except for dominant to undergo atresia) and more LH, leading to Ovulation
Ovulation
Rupture of the mature follicle and ejection of secondary oocyte polar body.
Surge of LH causes completion of mitosis I
Luteal phase
Luteal phase begins with hemorrhaging of ruptured follicle
Epithelial cells lining follicle fill in the lumen and form corpus luteum (CL)(endocrine)
Progesterone and estrogen released from (CL) prepare uterus for implantation of embryo
Inhibin released from the corpus luteum also inhibits gonadotropin release
If fertilization does not occur, corpus luteum degenerates and is filled in with connective tissue
•Structure known as corpus albicans
List several things that the female reproductive system does that the male system does not.
Produces oocytes. Hoses and nourishes the developing embrio/fetus/baby
Androgynous embryonic structures
- Genital tubercle becomes clitoral glans
- Urogenital folds turn into labia minora
- Labioscrotal folds turn into labia majora
Female External Genitalia
Clitoris
Labia majora
Labia minora
Internal Genitalia
Ovaries
Uterine tubes
Uterus
Vagina
What are the functions of the ovaries?
- Female gonads•Main functions are production of secondary oocytes (gametes) and secretion of female sex hormones
- Paired, lumpy, shaped like almonds, and about twice the size of
- Like the testes, covered and protected by tunica albuginea
- Has cortex and medulla
- Oocytes produced in cortex
- Medulla is connective tissue and contains blood vessels and nerves
What are the regions of the ovaries?
- Has cortex(Outer) and medulla(Middle)
- Oocytes produced in cortex
- Medulla is connective tissue and contains blood vessels and nerves for nourishment
What important structures are contained within the suspensory ligaments of the female pelvic cavity?
Contain ovarian artery, vein, lymphatics, and nerves. Important for nourishment
Define folliculogenesis:
•Development of the follicles surrounding the gametes
FSH triggers the follicular cells to produce more estrogen progesterone and inhibin.
LH triggers completion
Female secondary sex characteristics and hormone responsible.
Estrogen: Sex organs, skeletal growth, increased pelvic width, fat deposition, breast development.
Thelarche
First sign of female puberty
Pubarche
- Appearance of pubic and axillary hair, along with apocrine gland activity
- Produced as a result of androgens from adrenal cortex and ovaries
Menarche
- Usually around age 12
- Minimum of 17-22% body fat required for menstruation
- Amenorrhea below 17%
- Low levels of leptin in blood suppresses gonadotropin release
Why do females finish puberty first?
Because they do not ovulate for the first year and male finish about when they start to ovulate.
Oogenesis
- Egg production –ovum is mature gamete
- Cyclical and results in production of one egg per month
- Many aspects of female reproductive physiology and behavior have evolved as a result of this
- In fifth or sixth week of embryonic development, oogonia (female germ cells) migrate to gonadal ridges
- Oogonia undergo mitosis until fifth month of fetal development to produce 6 or 7 million oogonia
- Go into state of arrested development until shortly before birth
- By time of birth, all oogonia have differentiated into primary oocytes, and are arrested in meiosis I
What event of oogenesis typically occurs between the birth of the female and the onset of puberty?
- By the time puberty is reached, most primary oocytes have degenerated
- Known as atresia
- 2 million remain at birth, and 200,000 remain by puberty
Primordial follicle
Cluster together in “egg nests”
Stuck in arrested meiosis I
Single layer of follicular cells surround primary oocyte
Early primary follicle
Primary follicles also contain a primary oocyte
•The single layer of cells are now cuboidal and are called granulosa cells
Late primary follicle
Primary oocyte
multiple layers of granulosa cells
•Stratified cuboidal
Secondary follicle
stratified cuboidal epithelium surrounding a primary oocyte
•Cells secrete glycoprotein layer around oocyte called zona pellucida
•Thecal cells form around follicle
•LH and insulin cause thecal cells to absorb cholesterol from blood
•Used to synthesize androgens
•Androgens move to granulosa cells, which convert it to estrogen
Mature follicle
Also called: Tertiary, vesicular, antral, or Graafian
•Antrum is much larger and crescent shaped
- Cumulus oophorus is a collection of granulosa cells that surrounds oocyte
* Forms bridge between follicle wall and oocyte - Protective layer of cells closest to oocyte called corona radiata
* Acts as blood-oocyte barrier - Secondary oocyte produced just prior to ovulation
* Completion of meiosis I in response to which hormone?
