Reproductive System Flashcards
Number of eggs at birth
About 7 million
Number of eggs ovulated in a lifetime
About 400
Neurohypophysis
Posterior pituitary
Adrenohypophysis
Anterior pituitary
Sperm produced per second per testis
1500
4 water soluble hormones
GnRH
LH
FSH
Oxytocin
3 lipid soluble hormone classes
Androgens
Oestrogens
Progestagens
2 androgens
Testosterone
5 alpha dihydrotestosterone
3 oestrogens
Oestradiol
Oestriol
Oestrone
The main progestagen
Progesterone
Describe how hormones are released from the posterior pituitary
Neurosecretory neurons are aggregated into nuclei and possess long axons that pass into the posterior pituitary
Neurosecretory peptide hormones are synthesised in the hypothalamus and travel bound to carrier proteins down the axon terminals to be stored in secretory vesicles
Nerve impulses travel down the axon to trigger exocytosis of the secretory vesicles releasing the peptide hormones
Describe how hormones are released from the anterior pituitary
Neurosecretory neurons synthesise releasing and inhibiting hormones which travel to the axon terminus
Neurosecretory peptide hormones are secreted in response to nerve impulses into linking hypophyseal portal vessels
Hormones act on specific anterior pituitary secretory cells arranged in clumps at the termini of the portal blood vessel
Pulsatile release
Hypothalamic secretions released in discrete bursts separated by periods of stasis
Prevents receptor desensitisation and downregulation
Vagina
Elastic muscular 7.5-9.0 cm tbue extending from cervix to external environment
Passageway for menstrual fluid elimination
Penis receiver
Sperm holder
Uterus
Small pear shaped organ hat weighs 30 - 40 g
Pathway for sperm transport
Provides mechanical protection, nutritional support and waste removal for embryo
Source of menstrual flow
Normally antiflex (90 degrees to vagina) but can be retroflex (not 90 degrees)
Stratum functionalis
Contains most of the uterine glands
During menstruation, expands, vascularises and sloughs off
Stratum basalis
Attaches endometrium to myometrium
Responsive to oxytocin by contracting
Uterine tubes
Fertilisation occurs in the ampulla
Provides a rich, nutritive environment containing lipids and glycogen for sperm, egg and embryo
Epithelial lining is ciliated and non-ciliated secretory columnar cells
Mucosa surrounded by concentric layers of smooth muscle
Fimbriae
Cilia like structures that partially cover the ovary and dray the oocyte into the uterine tube
Ovaries
Oval structures that weight 5 - 10 g
Comprised of cortex, medulla and hilum
Outer ovarian cortex
Contains developing ovarian folllicles
Central ovarian medulla
Consists of ovarian stroma and steroid producing cells
Inner hilum
Acts as a point of entry for nerves and blood vessels
McDonalds rule
A measure of normal pregnancy growth is measuring the distance from top of uterus to pubic bone
Number of cm should be roughly equal to number of weeks pregnant
Primordial follicle
The oocyte surrounded by flat follicular cells
Primary follicle
Increase in size, squamous cells convert to columnar cells
Can be one layer of granulosa cells (used to be the follicular cells) or more layers depending on maturity of follicle
Secondary follicle
Granulosa cells proliferate and produce a viscous follicular fluid that coalesces to form an antrum
Thecal cells condense and form around follicle to become the theca interna and theca externa
Any follicle that has an antrum but no stalk is considered secondary
Mature follicle
Oocyte becomes suspended in fluid as the antrum grows
It is connected to the rim of peripheral granulosa cells by a thin stalk of cells
Ovulation
Increasing size of the follicle and its position in the cortex causes it to bulge from the ovarian surface
The follicle ruptures, carrying the oocyte and its surrounding mass of cumulus cells with it outside the ovary
The fimbria sweep the sumulus mass into the uterine tube
Corpus luteum (no fertilisation)
Empty follicle
Antrum breaks down
Basement membrane between granulosa and thecal layers breaks down
Blood vessels invade
Granulosa cells form lutein cells and secrete progesterone
The white scar tissue remaining is absorbed back into the stromal tissue of the ovary over weeks to months
Corpus albicans
The white scar tissue left over from the corpus luteum after luteinisation and without fertilisation
Corpus luteum (fertilisation)
Corpus luteum is rescued from degeneration by hCG produced by the chorion of the embryo and persists past its normal 2 week lifespan
Theca interna
Inner layer
Glandular and highly vascular
Secrete oestradiol
Theca externa
Surrounding fibrous capsule
Supportive
Describe the hormonal changes in the female reproductive cycle
Corpus luteum regresses, FSH levels increase
FSH stimulation increases follicular growth
After 6 - 7 days, dominant follicle is selected, oestradiol secreted by mature follicle
Oestradiol suppresses FSH and LH production
Oestrogen levels rise until a threshold concentration of oestradiol is exceeded (about day 12) which is maintained for 36 hours causing a switch from negative to positive feedback
The positive feedback triggers a rise in GnRH leading to LH surge
LH surge induces ovulation
Corpus luteum develops and secretes progesterone
Elevated progesterone levels inhibit GnRH leading to decreased LH and FSH levels
Corpus luteum regresses
Describe the uterine cycle in terms of its phases
Menstruation - Menstrual phase - Days 1 - 5 - Very thin stratum functionalis Proliferative phase - Preovulatory phase (days 6 - 12) - Stratum functionalis increasing in thickness - Ovulatory phase (days 13 - 15) Secretory phase - Postovulatory phase - Days 16 - 28 - Huge increase in stratum functionalis thickness - peaks around day 24
Describe how female sex differentiation occurs
The default mechanism
In the absence of testosterone, estrogens and progestagens secreted allowing Mullerian duct development and Wolffian ducts regress
Internal female genitals created
Describe how male sex differentiation occurs
Sertoli cells secrete anti-Mullerian hormone which leads to Mullerian duct regression
Leydig cells secrete testosterone which leads to Wolffian duct development which leads to internal male genitals
Describe what the urethral folds turn into
Male: Penis shaft
Female: Labia minora
Describe what the genital tubercle turns into
Male: Glans penis
Female: Clitoris
Describe what the labioscrotal swelling turns into
Male: Scrotum
Female: Labia majora
First endocrine sign of puberty
GnRH release causing an increase in plasma LH levels
Secondary sexual characteristic development in females
1) Breast development
2) Pubic hair
3) Height spurt
4) Menarche
Starts and stops by oestrogens
Secondary sexual characteristic development in males
1) Testis development
2) Pubic hair
3) Penis growth
4) Height spurt
Starts by androgens, stops by oestrogens
Describe how pubic hair begins to grow
Exposure of hair follicles to increased androgens causes increased hair growth
Describe why ovulation doesn’t start at the same time as the first menstrual bleed
Ovulation requires an oestrogen-mediated positive feedback mechanism causing an LH surge which isn’t fully developed at the time of the first bleed
Ovulation can lag behind for about a year after the first bleed
Menopausal phases
Pre-menopause - 40 years - regular menstrual cycles Menopausal transition - 46 - 52 years - end of regular cycles, some still occur - pre-menopause to post-menopause Peri-menopause - 46 - 55 years - pre-menopause to ovarian senescence Post-menopause - 52 years - no more menstruation - ovary still functioning Ovarian senescence - 55 years - no more eggs, ovary no longer functioning
Symptoms of menopause
Vasomotor - hot flushes - night sweats Genitourinary - atrophic changes - vaginal dryness Bone metabolism - osteoporosis Behavioural - depression, tension, anxiety - loss of libido
Precocious puberty
Puberty before 7 in girls and 9 in boys
GnRH dependent problem, often due to a hypothalamus tumour that increases GnRH levels
Delayed puberty
Lack of puberty at 13 in girls and 14 in boys
Gonadotrophin signals from pituitary inadequate for sex steroid hormone secretion
Seminiferous tubules
Where spermatogenesis occurs
20,000 sperm per second in a male
Stages of sperm production
Spermatogonium Primary spermatocyte Secondary spermatocyte Spermatid Spermatozoon
Spermatogenesis
At puberty, primary germ cells are reactivated - not spermatogonial stem cells
Spermatogonia divide by mitosis 6 times - 1 cell left undifferentiated each time to maintain stem cell population
Primary spermatocyte goes through meiosis I, dividing the pairs of chromosomes into separate cells
Secondary spermatocyte goes through meiosis II, dividing the pairs of chromatids into separate cells
Spermatid grows a tail and develops into spermatozoon
