Physiology Flashcards
- Describe the process of sperm production and its hormonal control
- Understanding of factors affecting spermatogenesis
- List the major actions of sex steroids in the male
- Understand the process of oogenesis
- List the major actions of the sex steroids in females
- Describe the hormonal control of ovarian and menstrual cycle
- Understand the factors affecting oogenesis
Structure of the testis
Process of spermatogenesis
Endocrine control of testicular function and factors affecting spermatogenesis
Structure of the ovary
Process of oogenesis
Endocrine control of follicular development (ovarian cycle)
Endocrine control of the menstrual cycle
What process produces gametes (i.e. gametogenesis [oogenesis or spermatogenesis)
Meiosis
What is meiosis
Sex cell division that reduces the number of chromosomes in the parent cell by half and produces four haploid gamete cells, in 2 rounds of division
Process of oogenesis
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- Diploid oogonium go through mitosis until one develops into a primary oocyte, which will begin the first meiotic division, but then arrest until later in life when it will finish this division in a developing follicle
- The primary oocyte undergoes meiosis I, giving rise to a haploid secondary oocyte and a smaller polar body, then arrests until time of fertilisation when it will undergo meiosis II to release a mature ovum and another polar body
At the time of birth, all future eggs are in the prophase phase and have only undergone this first stage of meiosis
When does the second round of meiosis kick in
At adolescence, anterior pituitary hormones cause the development of a number of follicles in an ovary. This results in the primary oocyte finishing the first meiotic division
The cell divides unequally, with most of the cellular material and organelles going to the secondary oocyte, and only one set of chromosomes and a small amount of cytoplasm going to the polar body (usually dies)
What happens during ovulation
+ second meiotic division isn’t completed until…
A secondary oocyte will be released and travel toward the uterus through the oviduct (uterine tube)
If the secondary oocyte is fertilised, the cell continues through meiosis II, completing meiosis
Females develop millions of primordial follicles in utero
Most degrade by the time of birth
What happens to these primordial follicles with each menstrual cycle
A few mature with each cycle and rupture to release an egg into the uterus
Primordial follicle –> … –> … –> …
Primary follicle –> mature (graffian) follicle –> ovulation
2 phases of the ovarian cycle
Follicular phase (primary follicle –> mature follicle)
Luteal phase (degeneration of mature egg)
The follicular phase of the menstrual cycle requires a surge of what hormone from the pituitary to mature a primary follicle into a graafian follicle ready for ovulation
Luteinizing hormone
A natural increase in what ovarian hormone during the menstrual cycle causes an egg to mature and be released
What ovarian hormone is high during the secretory phase when eggs degenerate if they’re not fertilised
Oestrogen
Progesterone
3 phases of the uterine cycle (occurs parallel to the 2 phases of the ovarian cycle)
Parallel to follicular phase of ovarian cycle
- Menses (period)
- Proliferative
Parallel to luteal phase of ovarian cycle
-Secretory - mature eggs can implant into uterus
Main female reproductive hormones (5)
GnRH FSH LH Oestradiol Progesterone
Function of GnRH in terms of female reproductive system
Stimulate LH and FSH secretion from anterior pituitary
Function of FSH from anterior pituitary in terms of female reproductive system
Stimulate follicular recruitment and development
Functions of LH from anterior pituitary in terms of female reproductive system (3)
Maintain dominant follicle
Induce follicular maturation and ovulation
Stimulate corpus luteum function
Functions of oestradiol (main oestrogen - made by ovaries in premenopausal women) (3)
Supports female secondary sexual characteristics and reproductive organs
Negative feedback for LH and GnRH BUT in late follicular phase, it is positive control for LH surge
Stimulates proliferative phase to repair endometrial lining after bleeding
Functions of progesterone produced by corpus luteum
Maintenance of secretory endometrium
Negative feedback control of HPO
By age 35, what % of eggs do you have left
5%
Major actions of oestrogens (sex steroid) (5)
Protein metabolism Carbohydrate metabolism Lipid (fat) metabolism Water and electrolyte balance Blood clotting
Name all the structures that produce semen + which pf these produce the majority of it
Testes and epididymis –> Prostate –> Seminal vesicles (majority) –> Bulbourethral gland
Structure of the testes
Consist of a series of lobules, each containing seminiferous tubules supported by interstitial tissue.
Where are spermatozoa produced + they then travel to where to be concentrated + then travel to where to be stored + matured
Spermatozoa are produced in the seminiferous tubules
The developing sperm travels through the tubules, collecting in the rete testes.
Ducts known as efferent tubules transport the sperm from the rete testes to the epididymis for storage and maturation
Process of spermatogenesis
Spermatogonia are the initial pool of diploid cell that divide by mitosis to give two identical cells.
One of these cells will be used to replenish the pool of spermatogonia and the other will replicate by mitosis several times to form identical diploid cells to form PRIMARY SPERMATOCYTES
Primary spermatocytes then undergo meiosis
- Meiosis I produces two haploid cells known as secondary spermatocytes
- Meiosis II occurs straight after and produces four haploid cells known as spermatids
The seminiferous tubules within the the testes are lined by what cells that aid the maturation process of the spermatozoa
In the interstitial tissue between seminiferous tubules lie what cells that are responsible for testosterone production
Sertoli cells
Leydig cells
After meiosis II is complete and 4 spermatids have been formed, what process do they undergo while they travel to the epididymis
Spermiogenesis (remodelling and differentiation into mature spermatozoa)
Major actions of testosterone
- brain
- skin
- muscle
- kidney
- sexual organs
- bone
Brain - libido, mood
Skin - hair growth, sebum production
Muscle - increase in strength
Kidney - stimulate EPO production
Sexual organs - penile growth, spermatogenesis
Bone - accelerated linear growth, closure of epiphyses
Hormones involved in the female HPO axis
GnRH - from hypothalamus
FSH + LH - from AP
Steroid hormones - oestrogen (oestradiol, oestrone, oestriol), progesterone, testosterone - from ovary
Most oestrogen exhibits negative feedback on hypothalamus and AP BUT when does oestrogen exhibit positive feedback
At mid-cycle (days 12-14) to cause release of LH (LH surge)
Describe the ovarian cycle
FSH and LH stimulates a number of follicles to be recruited, beginning a new ovarian cycle
At mid cycle (days 12-14), positive feedback of oestrogen on hypothalamus and AP causes an LH surge which induces ovulation of a mature egg 36 hrs later
The rest of the follicle consisting of theca and granuloma cells go on to form the corpus luteum which produces progesterone to help maintain a suitable environment for egg implantation
If fertilisation doesn’t occur then the corpus luteum will degenerate into corpus albicans 14 days later and stop producing progesterone leading to the next cycle of menstrual bleeding; if fertilisation does occur, hCG supports surgical of the corpus luteum to keep producing progesterone until the placenta takes over for nutrition
An egg follicle contains what 2 secretory cells
Theca - secretes inhibin
Granulosa - secretes oestrogen
The menstrual cycle is under the effect of which hormone
Oestrogen
At ovulation (mid-cycle), the endometrium becomes under the effect of progesterone - why?
Enhances thickening of lining of uterus and increases vascular supply to create suitable environment for implantation
Most oestrogen exhibits negative feedback on hypothalamus and AP BUT when does oestrogen exhibit positive feedback
At mid-cycle (days 12-14) to cause release of LH (LH surge)
Hormones involved in the male reproductive system
GnRH - gonadotrophin releasing hormone (Hypothalamus)
Gonadotrophins - FSH and LH (Pituitary)
Testosterone (Testis)
Site of sperm production
Seminiferous tubules of the testis
Describe the function of the following in regards to males
- germ cells
- sertoli cells
- interstitial leydig cells
Produce sperm
Support sperm producing cell, produce inhibin
Produce testosterone
Describe how sperm travel once it’s been secreted by the testes
Travels to the epididymis to
- Mature
- Gain mitochondria
- Develop tail
Then travels through vas deferens to seminal vesicles then prostatic urethra which adds more seminal fluid, further continuing through the urethra and out of the penis
Sperm are produced from
Puberty then throughout life
Factors affecting oogenesis/spermatogenesis
Problem with the hormonal control (genetic, tumours, medications, functional), e.g. turner’s syndrome (genetic), klinefelter (genetic)
Problem at the site of production (genetic, cancer treatment induced, surgery, trauma, infections)
Predominant factor affecting female fertility
Age - decline in ovarian reserve
