Ovarian and Testicular Function Flashcards
What are the two major functions of reproductive organs?
Gametogenesis
Secretion of hormones
Which cells produce spermatozoa?
Sertoli cell in seminiferous tubules
Which cells secrete testosterone?
Leydig cells
Which cells secrete oestrogen and progesterone?
Theca and granulosa cells
What is gametogenesis?
Germ cells exist in embryonic gonad Mitotic divisions increase number of germ cells Meiosis produces - Primary gamete - Secondary gamete - Haploid gamete Timing different in males and females
Describe spermatogenesis
Spermatogonium > mitotic proliferation > - 1 daughter cells remains at outer edge of seminiferous tubule to maintain germ cell line - 1 daughter cells moves toward lumen to produce spermatozoa - Diploid Primary spermatocyte - Diploid - Undergo 1st meiotic division Secondary spermatocyte - Haploid - Undergo 2nd meiotic division Spermatids - Haploid - Mature Spermatozoa - Haploid
Describe oogenesis
Starts at foetal life
Oogonium
- Mitotic proliferation prior to birth in foetal ovaries
- Diploid
Primary oocytes
- Diploid
- Arrested in 1st meiotic division
- After puberty, 1 primary oocyte reaches maturity and ovulated per month, until menopause
- Each cycle, many primary oocytes start to develop, but only 1 finishes meiosis I
Secondary oocyte + 1st polar body
- Haploid
- 2nd meiotic division completed after fertilisation
- 2nd polar body produced
What does one oogonium eventually produce after oogenesis?
1 ovum + 3 polar bodies
What happens to the polar bodies?
Degenerate
What sex steroids does the ovary produce?
Oestrogen
Progesterone
What sex steroids does the testis produce?
Testosterone
Dihydrotestosterone (DHT)
What is the function of the hypothalamus in the hormonal regulation of reproduction, and what hormone does it secrete?
Pulse generator
Secretes gonadotropin releasing hormone
What hormones does the anterior pituitary secrete?
Luteinising hormone
Follicle stimulating hormone
What are the peptide hormones produced by the gonads?
Inhibin
Activin
What converts testosterone to oestradiol in females?
Aromatase
What converts testosterone to DHT in males?
5-alpha-reductase
Do males have a lot of aromatase?
No
What does follicle stimulating hormone stimulate in the gonads?
Gamete production
What does luteinising hormone stimulate in the gonads?
Steroid synthesis
Gamete production in females only
What is the long-loop feedback in gonadotropin release?
Steroid and peptide hormones feed back to anterior pituitary and hypothalamus
Can be negative/positive
What is the short-loop feedback in gonadotropin release?
Anterior pituitary hormones negatively feed back to hypothalamus
What are the external genitalia of the male reproductive system?
Penis
Scrotum
What are the accessory glands and ducts of the male reproductive system?
Prostate
Seminal vesicle
Bulbourethral gland
Where in the testes are sperm made?
Seminiferous tubules
Where does sperm maturation occur?
Epididymis
What delivers sperm to the urethra?
Vas deferens
Describe the cellular structure of the seminiferous tubules
Sertoli cells surround and support sperm
Spermatogonia divide and produce all sperm cells
Interstitial tissues support spermatogenesis
- Leydig cells produce testosterone
- Capillaries deliver nutrients and remove wastes
What are the effects of testosterone before birth?
Masculinises reproductive tract and external genitalia
Promotes descent of testes into scrotum
What are the effects of testosterone on sex-specific tissues?
Promotes growth and maturation of reproductive system
Spermatogenesis
What are the other reproductive effects of testosterone?
Sex drive
Control of gonadotropin secretion
What are the secondary sexual effects of testosterone?
Hair growth
Voice deepens
Muscle growth
Body configuration
What are the non-reproductive actions of testosterone?
Protein anabolic effects
Bone growth
Closure of epiphyses
Sebaceous gland secretions
What do the bulbourethral glands produce, and what are each component’s functions?
Mucus = lubricant Buffers = neutralise acidic environment of vagina
What does the prostate gland produce, and what are each component’s functions?
Buffers = neutralise acidic environment of vagina
Citric acid = nourish sperm
Enzymes = clot semen in vagina > liquefy clot
What do the seminal vesicles produce, and what are each component’s functions?
Fructose = nourish sperm
Vitamin C = nourish sperm
Enzymes = clot semen vagina > liquefy clot
Prostaglandins = smooth muscle contraction
What does the epididymis produce, and what are each component’s functions?
Carnitine = nourish sperm
Which cells in the male does follicle stimulating hormone stimulate?
Sertoli cells
To stimulate spermatogenesis
What do Sertoli cells produce in response to follicle stimulating hormone that acts as negative feedback on follicle stimulating hormone release?
Inhibin
Which cells in the male does luteinising hormone stimulate?
Leydig cells
What cell product of Sertoli cells does testosterone bind to?
Androgen-binding protein
When does the menstrual cycle start?
Puberty
When does the menstrual cycle end?
Menopause
What are the two phases of the menstrual cycle?
Follicular/proliferative
Luteal/secretory
What secondary sex characteristics are controlled by oestrogen in females?
Breast development
Distribution of body fat
What secondary sex characteristics are controlled by adrenal androgens?
Growth of pubic and axillary hair
Sex drive
What external structures protect the vagina?
Labia majora
Labia minora
What structure releases the dominant oocyte?
Mature follicle ruptures
What happens to the follicle after it releases its oocyte?
Becomes corpus luteum
What is the myometrium?
Muscular layer of uterus > contracts during labour
What part of the uterus changes drastically during the menstrual cycle and leads to bleeding during menstruation?
Endometrium
What happens during the follicular phase of the menstrual cycle?
Follicle growth in ovary
Days 0-13
What happens in ovulation?
Follicle ruptures and releases oocyte
Day 14
What happens during the secretory phase of the menstrual cycle?
Ruptured follicle becomes corpus luteum in preparation for pregnancy
Days 15-28
What happens during menses?
No pregnancy
Bleeding from uterus as endometrium shed
What happens during the proliferative phase of the uterine cycle?
New layer of endometrium in preparation of pregnancy
What happens during the secretory phase of the uterine cycle?
Conversion of endometrium to secretory structure to promote implantation
What hormone stimulates follicular development?
Follicle stimulating hormone
What does follicular development involve?
Maturation to secondary and tertiary follicle
Granulosa cells produce oestrogen
What is the effect of the oestrogen produced by the granulosa cells in the follicular phase?
Positive feedback develops follicles and increases oestrogen
Negative feedback decreases follicle stimulating hormone and luteinising hormone secretion
What cells does luteinising hormone stimulate in females?
Theca cells
What do theca cells produce?
Androgens > converted to oestrogen by aromatase in granulosa cells
What is happening in the uterus during the early follicular phase of the ovary?
Menstruation
What does high oestrogen do during ovulation?
Positive feedback on gonadotropin releasing hormone > luteinising hormone and follicle stimulating hormone surge
Primary oocyte completes meiosis I to form secondary oocyte
Luteinisation
What does high inhibin do during ovulation?
Inhibits follicle stimulating hormone and development of new follicle, because we want to fertilisation
What does low progesterone during ovulation do?
Positive feedback on gonadotropin releasing hormone and luteinising hormone
- Therefore more luteinising hormone than follicle stimulating hormone produced
What is happening in the uterus around the time of ovulation?
Oestrogen stimulates proliferation of endometrium
Progesterone receptors develop
What is happening in the cervix around the time of ovulation?
Abundant, clear non-viscous mucus
- To allow sperm to get up there
What happens to the granulosa cells during the luteal phase?
Form corpus luteum
Produce progesterone
What do high progesterone and oestrogen do during the luteal phase?
Maintain endometrium Decrease secretion of - Gonadotropin releasing hormone - Luteinising hormone - Follicle stimulating hormone
What does inhibin do during the luteal phase?
Decreases follicle development
What are the hormones secreted by the corpus luteum?
Lots of progesterone
Oestrogen
Inhibin
What is happening in the uterus during the luteal phase?
Preparing for pregnancy
Vascular
Secretory
What is happening in the cervix during the luteal phase?
Thick, sticky, viscous mucus
- Don’t want more sperm coming through
- Want to protect reproductive tract
What happens to your basal body temperature during the luteal phase?
Increases
What should you monitor if you want to get pregnant?
Length of cycle
Type of mucus produced
Basal body temperature
What happens to hormone levels if there is a pregnancy?
Maintain high hormones
What happens to hormone levels if there is no pregnancy?
Corpus luteum dies > low hormones
Loss of maintenance > menses
Removal of negative feedback > high follicle stimulating hormone and luteinising hormone > development of new follicle
What causes menopause?
Ovaries cease responding to luteinising hormone and follicle stimulating hormone
Low levels of oestrogen and progesterone
Cessation of egg development
What causes the symptoms of menopause?
Loss of oestrogen
