Reproductive Physiology Basics (Parts 1-6) Flashcards
Describe the structure of ovaries
surface, cortex, medulla
- surface: connective tissue capsule covered with layer of simple cuboidal epithelium.
- cortex: peripheral part, connective tissue containing ovarian follicles (one oocyte surrounded by single layer of cells).
- medulla: central part, connective tissue with blood vessels.
what are the functions of ovaries?
- oocyte production
- steroid hormone production: estrogen develops secondary sexual characteristics, progesterone prepares endometrium for implantation, 50% of testosterone produced by ovaries before menopause
outline the process of oogenesis
- primordial germ cell mitosis in fetal life only and primotdial follicles arrested in the stage of 1st meiotic division until puberty.
- first meiotic division complete and second division starts after puberty and leads to release of one secondary oocyte in a menstrual cycle which is capable of fertilisation.
- second meiotic division completes after fertilisation of oocyte with sperm.
describe primordial follicles
primary oocyte arrested in first meiotic division surrounded by one layer of squamous pre granulosa cells
describe a primary follicle
oocyte surrounded by zona and cuboidal granulosa cells
describe a secondary follicle
increased oocyte diameter and multiple layer of granulosa cells, resumption of first meiotic division
describe tertiary/graffian follicles
Tertiary follicles, also known as Graafian follicles, are large, fluid-filled follicles in the ovaries that prepare to release an egg.
Structure
Antrum: A fluid-filled space within the follicle
Theca: A two-layered structure around the antrum, consisting of theca interna and theca externa
Zona pellucida: A thick covering around the secondary oocyte
Cumulus oophorus: A mound of granulosa cells that projects into the antrum and surrounds the oocyte
Corona radiata: A thin ring of granulosa cells that surrounds the oocyte
what are the four phases of the ovarian cycle?
- follicular phase
- ovulation
- luteal phase
- menstruation
what happens during the follicular phase of ovarian cycle?
- FSH causes follicle to mature and produce oestrogen (inhibiting development of other follicles)
what happens during the ovulation phase of ovarian cycle?
- an LH surge causes ovulation (follicle ruptures and releases a secondary oocyte).
what happens during the luteal phase of ovarian cycle?
- ruptured follicle forms a corpus luteum and secretes progesterone (and some oestrogen).
what happens during the menstruation phase of ovarian cycle?
- when the corpus luteum degenerates (forms a corpus albicans), a new ovarian cycle can begin.
what problems can cause amenorrhoea (no periods)?
- problem with regulating hormones
- problem with ovarian function
- problem with uterus or outflow tract
which conditions/drugs can cause ameorrhoea due to a problem with regulating hormones?
- functional: excessive weight loss or gain, over exercising, stress
- chronic medical conditions: diabtetes, sarcoidosis, renal disease, TB
- intracranial space occupying lesion: prolactinoma, tumours, cysts
- infection or trauma: meningitis, intracranial bleed, Sheehan’s
- drugs: glucocorticoids, anabolic steroids, opiates
- genetic: Kallmann’s syndrome
List some problems with ovarian function that can cause amenorrhoea
- hypergonadotropic hypogonadism: high or normal FSH,LH
- genetic: Turner’s syndrome (46X), fragile X
- ageing: steep decline in ovarian function past 35 years
- primary ovarian insufficiency
- chronic illness: autoimmune disease
- radiotherapy or chemotherapy
- infection: tuberculosis, mumps oophoritis
list some problems with the uterus or outflow tract which can cause amenorrhoea
Congenital:
- absent uterus, vagina- lack of Mullerian duct development (MRKH syndrome)
- transverse vaginal septum or imperforate hymen- Mullerian duct fail to canalise
- androgen insensitivity syndrome
Iatrogenic:
- uterine adhesions or synechiae (Asherman syndrome)
- radiotherapy (pelvic or cervical)
list the three types of cells within the seminiferous tubules and their function
- germ cells produce- produce sperm
- sertoli/sustenacular cells- support sperm producing cell, induce inhibin
- interstitial (Leydig) cells- produce testosterone
what are the functions of the testes?
- sperm production
- testosterone production- male secondary secual characteristics, controls spermatogenesis
how do pituitary hormones interact with testes hormones?
LH and FSH stimulate spermatogenesis and testosterone secretion by the testes.
how do testes hormones interact with pituitary hormones?
Testosterone and inhibin inhibit the secretion of GnRH by the hypothalamus and LH and FSH by the pituitary (negative feedback)
describe spermatogenesis
- Sperm production from the primordial germ cells.
- Average cycle of spermatogenesis is 64 days in which the germ cells pass through different developmental stages
Two distinct phases during the development:
- Spermatocytogenesis- Clonal expansion and maturation through mitotic and meiotic process
- Spermiogenesis- Differentiation into mature sperm cells
Process starts at puberty and continues lifelong
describe the chromosomal division during spermatogenesis
One mitotic division- Spermatogonium to primary spermatocyte-duplication, diploid chromosomes number(46)
First meiotic division- primary spermatocyte to secondary spermatocyte, two cells with haploid chromosome number(23)
Second meiotic division- secondary spermatocyte to spermatid, two cells with haploid chromosome number(23)
Spermiogenesis- maturation of spermatids into functional sperm cells
list some pretesticular medical factors affecting spermatogenesis
problem with hormonal control
- Functional- excessive weight loss, gain
- Intracranial tumours, cysts, bleed
- Prolactinoma
- Medications- opiates, external testosterone, steroids(body building)
- Genetic- Kallmann’s syndrome
list some testicular medical factors affecting spermatogenesis
problem at the site of production
- surgery: orchidectomy, orchidopexy
- STI
- mumps orchitis
- testicular trauma or torsion
- radiotherapy or chemotherapy
- genetic: Klinefelters (46 XXY), Y- chromosome microdeletion
list some steps to reduce the impact of factors affecting fertility
- improve lifestyle: normal BMI, stop smoking, alcohol limitation, healthy diet, exercise, adjustments to occupational exposure
- optimise underlying medical condition
- stop medications or switch to alternative pregnancy compatible medications
- reduce STI risk and treat promptly if diagnosed
- fertility preservation - sperm freezing prior to surgery or cancer treatment
