26-10-21 - Reproductive System Flashcards
What are the arteries and veins that supply/drain the testes?
Where is the penis positioned in relation to the bladder, prostate, and anus?
- Testicular arteries arise from the abdominal aorta, with each teste having its own independent blood supply that is not connected to the others
- The right teste drains into the inferior vena cava
- The left teste drains into the renal vein
- The penis is Inferior to the bladder and prostate
- The penis is anterior to the anus
Where are the testes suspended?
What are they surrounded by?
What is the skin and muscle like here?
How is it divided?
Why are the testes suspended here?
- Each teste is suspended outside the body in the scrotum, and is surrounded by tunica albuginea
- The skin is rugose (crinkled) and contains dartos (smooth muscle)
- The scrotum has a midline raphe, and is the divided by the septum
- The testes are suspended outside of the body in order to keep cool (2-3C below core temperature)
What do the male gonads produce?
What process is this known as?
Where does this process occur?
What are the 2 cells in this structure?
What are they for?
What are they separated by?
- The male gonads produce sperm/gametes via spermatogenesis
- This occurs in the seminiferous tubules
- There are 2 cell types within the seminiferous tubules:
- Leydig cells – site of steroid synthesis and located outside of the basement membrane
- Sertoli cells – nurse cells for sperm, and located within the basement membrane
- The basement membrane divides Leydig cells and capillaries from Sertoli cells
What are the 3 gonadal hormones?
What are they produced by?
What is their purpose?
• The 3 gonadal hormones:
1) Follicle stimulating hormone (FSH) – produce by anterior pituitary gonadotropic cells – FSH is important for the development of sperm in the seminiferous tubules
2) Luteinizing hormone (LH) - produce by anterior pituitary gonadotropic cells – LH stimulates Leydig cells to produce testosterone
3) Testosterone (steroid) – Produced by Leydig cells – production is regulated by FSH and LH (purpose in later flashcard)
What do sperm develop?
What do they arise from?
Describe the 3 steps of spermatogenesis
• Sperm cells develop at the basement membrane of seminiferous tubules from progenitor cells called spermatogonium
1) Sertoli cells act as support cells and aid in the development of the sperm. Sertoli cells have tight junctions between them, which are broken down and built up to allow the spermatogonium to make its way from the basement membrane to the lumen of the seminiferous tubule
2) As the spermatogonium moves towards the lumen, they develop, and the tight junctions are sealed up behind them.
3) Once reaching the lumen, the spermatogonia have developed into mature spermatozoa
What is the process of developed sperm being stored?
How is sperm then ejaculated?
What are the 2 accessory organs?
What are their functions?
- After sperm have developed and matured, they then move from the seminiferous tubules into the rete testis
- They then move into the epididymis via efferent ductulus, where they are stored.
- When ejaculation is about to occur, the sperm will move through the vas deferens and joins the urethra where the vas deferens come through the back of the bladder, to the prostate, and join the urethra.
- There are 2 accessory organs called the seminal vesicle and the bulbourethral gland
- These accessory organs add fluid and nutrients to semen, which sperm require to survive and generate the energy needed to move the flagella
What are the 4 stages of sperm before they are spermatozoa?
How long does this whole process take?
What 3 changes occur in the last stage?
What is this process regulated by?
How is this process different from menstruation?
1) Spermatogonia
2) Primary spermatocytes
3) Secondary spermatocytes
4) Spermatids
5) Spermatozoa
- This process takes 72 days
- From spermatids to spermatozoa, the spermatids lose their cytoplasm
- Their DNA is gathered in a specialized area called the head
- Flagella is developed to allow the sperm to move
- This process is regulated by FSH from the anterior pituitary gland and testosterone from the testes
- This process can occur from puberty until death, unlike menstruation, where there is a finite number of ova (plural for egg)
What are the 3 parts of the sperm?
What do they each contain?
- Head
- Acrosome (lysosome-related organelle) that contains proteolytic enzyme (like hyaluronidase and acrosin) that allow the sperm to penetrate the ovum (singular egg)
- The head has a nucleus that contains genetic material which combines with DNA from the female
- Midpiece
- Contains mitochondria around filamentous core
- Provides energy for the tail (engine room of sperm)
- Tail
- Specialised flagellum that propels the sperm forward
Where are the testicular endocrine functions found?
How is testosterone produced?
What can testosterone then do?
What can FSH do?
What can FSH and testosterone do in conjunction with one another?
What can Sertoli cells do in Leydig cells?
How do they do this?
- Testicular endocrine functions are in the Leydig and Sertoli cells
- Leydig cells have an LH (luteinizing hormone) receptor that when bound, produces testosterone
- Testosterone can diffuse across the basement membrane into Sertoli cells and regulate spermatogenesis
- FSH can also bind to its receptor on Sertoli cells and stimulate spermatogenesis
- Testosterone increase + stimulation of Sertoli cells by FSH leads to an increase in spermatogenesis
- Sertoli cells can regulate gene expression in Leydig cells and reduce testosterone production
- Sertoli cells can use the enzyme aromatase to convert testosterone into oestradiol (type of oestrogen)
- Oestradiol can diffuse back across the basement membrane into Leydig cells and has an inhibiting effect on the production of testosterone
What is GnRH?
Where is it released from in men?
How does it travel?
Where does it go?
What is the function of GnRH in gonadotropic cells in men?
How is the amount of GnRH regulated in men?
What does this impact?
What is this system known as?
What 2 ways does this process differ in males from females?
- GnRH is gonadotropin releasing hormone, which is a peptide hormone
- It is release from particular neurons, such as the preoptic and acuate nucleus of the hypothalamus
- It moves into capillaries of the pituitary stock, and flows from the hypothalamic regions to the anterior pituitary gonadotropes
- GnRH diffuses into these gonadotropic cells, and stimulates them to release LH, which targets Leydig cells to produce testosterone, and FSH, which targets Sertoli cells to produce inhibin B
- Testosterone and Inhibin B have negative feedback mechanisms, so can inhibit anterior pituitary gonadotropic cells and hypothalamic cells in order to regulate GnRH levels
- This impacts LH and FSH levels, which has a direct effect on spermatogenesis.
- This system is known as the Hypothalamic-Pituitary-Testicular Axis (HPT)
- In males, there is only 1 primary hormone instead of 2 (testosterone vs oestrogen and progestins)
- In the male system, no role for activins has been established.
1) What physiological effects does testosterone have on: • Bone (1 effect) • Muscle (1 effect) • Reproductive organs (4 effects) • Skin (1 effect)
What is the uterus?
What 2 things is it used for?
How does it sit in relation to the cervix?
How does the uterus sit in relation to the entry of the vagina?
Where does the uterus sit in relation to the small intestine?
- The uterus is a pear-shaped, central pelvic organ for the implantation of a fertilised ovum and growth of a foetus
- The uterus is anteflexed between the cervix and body – displacement forward of an organ so its axis its bent upon itself
- The uterus is anteverted at entry to the vagina – tilted towards the front of the abdomen
- The uterus is anterior to the small intestine
Where are the ovaries suspended?
What are they suspended by?
When does ovulation typically start in the menstruation cycle?
Describe the 5 steps in the process of fertilization.
- The ovaries are suspended in the body cavity on the lateral pelvic wall by the ligament of the ovary
- Ovulation usually occurs 10-16 days before the period starts
1) The ovaries release 1 egg a month (alternates sides each month)
2) The fimbriae generate waves of contraction that catches the egg and gets it into the fallopian tubes
3) The egg moves through fallopian tubes to the ampulla, which is where the sperm will meet the egg and fertilization occurs.
4) The fertilized egg (zygote) continues down the fallopian tube into the uterine cavity, then implants on the uterine wall
5) If implantation is successful, pregnancy develops
What is the female equivalent of the male gonads?
What do they produce?
What is this process called?
Where does this occur in the ovaries?
What releases the egg?
How often does this happen?
What are the cells that make up this structure?
What is the function of these cells?
- The female gonads are called ovaries, and produce oocytes (immature ovum) via oogenesis
- Oogenesis occurs in the follicles as they mature, with the mature egg being released by a mature (graafian) follicle, which occurs monthly.
- Similarly, to seminiferous tubules, follicles consist of Theca cells outside a basement membrane, and Granulosa cells within the basement membrane
- Theca cells outside of the basement membrane – produces androgens
- Granulosa cells inside of the basement membrane – produce steroids oestrogen and progestin
What are the 4 female gonadal hormones?
What are they produced by?
What are their functions?
• The 4 female gonadal hormones:
1) Follicle stimulating hormone (FSH) – produce by anterior pituitary gonadotropic cells – FSH is important for the development of follicles
2) Luteinizing hormone (LH) - produce by anterior pituitary gonadotropic cells – LH is important for the production of progestins and oestrogen in granulosa cells
3) Oestrogen and progestins (steroids) – Produced by granulosa cells of follicles – production is regulated by FSH and LH – Bring about the female menstrual cycle
What are the equivalent cells in male and female seminiferous tubules and follicles?
What are their functions?
- Male
- Seminiferous tubules
- Leydig cells outside of basement membrane – site of steroid synthesis
- Sertoli cells inside of the basement membrane – nurse cells for sperm
- Female
- Follicles of ovaries
- Theca cells outside of the basement membrane – produces androgens
- Granulosa cells inside of the basement membrane – produce steroids oestrogen and progestin
What is the process of the development of follicles in ovaries referred to as?
What are the 5 different stages of development of these follicles?
Why are the different stages of development important?
- The process of follicles developing in the ovaries is called folliculogenesis
- The 5 stages of development are:
1) Primordial
2) Primary
3) Secondary
4) Tertiary
5) Mature follicles (graafian follicles)
- The different stages of development allow for multiple follicles to develop simultaneously and be at different stages of development
What are theca cells located?
What is their role?
How do they do this?
What further reaction takes place?
What happens to this product?
What does binding in granulosa cells trigger?
What can these then be used for?
What then happens to this product?
What can Granulosa cells also convert?
- Theca cells are located outside of the basement membrane of follicles
- Cholesterol is taken up as LDL from the blood, which Theca cells converts to pregnenolone
- This is facilitated by LH binding to receptors on theca cells
- Pregnenolone then produces androstenedione and testosterone
- Androstenedione can then diffuse across the basement membrane into granulosa cells
- FSH hormone can then bind to receptors on granulosa cells, which stimulates the production of aromatases
- Granulosa cells can convert Androstenedione into Testosterone and Estrone using aromatases (only for estrone)
- Testosterone and estrone can be converted into Oestradiol (type of oestrogen) using aromatases Only for testosterone)
- Granulosa cells can also convert cholesterol into pregnenolone + activate aromatases
What is GnRH?
Where is it released from in woman?
How does it travel?
Where does it go?
What is the function of GnRH in gonadotropic cells?
How is the amount of GnRH regulated in woman?
What does this impact?
What is this system known as?
What 2 ways does this process differ in males from females?
- GnRH is gonadotropin releasing hormone, which is a peptide hormone
- It is released from particular neurons, such as the preoptic and supraoptic nucleus of the hypothalamus
- It moves into capillaries of the pituitary stock, and flows from the hypothalamic regions to the anterior pituitary gonadotropes
- GnRH diffuses into these gonadotropic cells, and stimulates them to release LH, which targets Theca and Granulosa cells, and FSH, which targets Granulosa cells
- LH binding causes Theca cells to produce progestins
- LH and FSH binding causes granulosa cells to produce progestins, oestrogens, inhibins, and activins
- Progestins, oestrogens and inhibins can act as part of a negative feedback mechanism, which can inhibit gonadotropic cells and hypothalamic cells
- This has an impact on LH and FSH levels, which directly effects processes such as oogenesis and folliculogenesis
- Activins can also act as a positive feedback mechanism for anterior pituitary gonadotropic cells
- This system is known as the Hypothalamic-pituitary-ovarian (HPO) axis
- In males, there is only 1 primary hormone instead of 2 (testosterone vs oestrogen and progestins)
- In the male system, no role for activins has been established.
When does ovulation occur in the menstrual cycle?
What occurs at this point?
What are the 3 steps to this happening?
What is it caused by?
What does this change lead to?
- Ovulation occurs mid-way through a 28-day menstrual cycle
- At this point, or just before, there is a shift from negative to positive feedback
1) Oestrogen levels increase as a result of stimulation from LH and FSH
2) As they increase, they reach a threshold level
3) If this threshold level is maintained for 2 days, this results in a positive feedback mechanism, which is caused by upregulation of receptors (e.g GnRH in anterior pituitary) when oestrogen levels are high
• This leads to large increases in the release of LH, which leads to the LH surge and ovulation
What is the ovarian cycle?
What is the endometrial cycle?
What regulates these cycles?
What do these 2 processes come together to make?
What are the 3 phases of the menstrual cycle?
- The ovarian cycle is the development of an immature follicle that has an egg in it
- The endometrial cycle is the development of the uterine wall in preparation of an egg being released, which will hopefully be fertilised and lead to implantation.
- The hypothalamic pituitary ovarian axis (HPO axis) regulate/controls these 2 cycles
- These ovarian and endometrial cycles come together to make the menstrual cycle
• The 3 phases of the menstrual cycle:
1) Menstrual phase
2) Proliferative phase
3) Secretory phase
What are the 2 phases of follicular development in the menstruation cycle?
When do they occur in the cycle?
What occurs at each phase?
1) Follicular phase
• Occurs before ovulation, and is the first part of the menstrual cycle
• Follicular phase involves developing a mature graafian follicle, which releases the egg during ovulation
2) Luteal phase/secretory phase
• Occurs after ovulation and is the second part of the menstrual cycle.
• The luteal phase is dominated by the corpus luteum, which is what is left of the follicle once the egg has been released.
• It has an important role in maintaining the endometrial lining until implantation, and ultimately the development of the placenta from the uterine wall, if the fertilisation is successful
• The corpus Luteum does this by producing progesterone levels, which is what is required to maintain the endometrial lining.
What do increase oestradiol levels lead to?
• Increasing oestradiol levels leads to the switching of sensitivity in the HPO axis system to a positive feedback mechanism, which leads to the LH surge that stimulates ovulation
What is the development of the uterine wall like during ovulation?
How does this change in the secretory phase?
Why does it change like this?
- At ovulation, the development o the uterine wall is at its maximum and is fully developed.
- In the secretory phase, the uterine wall begins to change
- It starts producing fluid and blood capillaries
- This provides the right environment for the fertilised egg to implant into, and for the placenta to develop from the uterine wall
What occurs to the corpus luteum if the egg is not fertilised?
What happens to progesterone, LH, and FSH levels?
What occurs to the endometrial lining of the uterine wall?
What phase does this lead into?
- If the egg is not fertilised, the corpus luteum starts to regress and degenerate after about 10-20 days
- This results in the crash of progesterone levels, and by this point, FSH and LH levels have decreased
- The endothelial lining begins to breakdown, which leads to the menstrual phase of the reproductive cycle, where women bleed.
What are the 3 main oestrogens? What are the physiological effects of oestrogens on: • Bone (1 effect) • Endocrine (1 effect) • Liver (4 effects) • Reproductive organs (5 effects)
Why does it produce these effects?
- Oestradiol (most potent)
- Oestrone
- Oestriol (secreted during pregnancy)
- These effects are to do with proliferation and growth
What are the 2 progestins in woman’s bodies?
Where are progestins produced?
What is the half life of progestins?
What is progestin secretion regulation linked with?
What are the physiological effects of Progestins on:
• Breast (2 effects)
• Reproductive organs (3 effects)
• Temperature (1 effect)
- Progestins – Progesterone and 17αhydroxyprogesterone
- Produced in the theca and granulosa cells
- Progestins have a short half-life of about 5 minutes in circulation
- Secretion regulation of progestins linked to oestrogen secretion
- Effect changes reasoning:
- Temperature half a degree higher for ovulation
- Less endometrial growth, and increased endometrial secretions so the endometrium becomes better environment for fertilised egg
- Thicker secretion produced so less sperm can get in
What does suckling from a baby stimulate in a mother?
What do these 2 hormones do?
Where do these hormones come from?
- Suckling triggers a spinal reflex process, resulting in the production of oxytocin and prolactin
- Oxytocin causes the contraction of myoepithelial cells around duct cells in the beast tissue, which pushes milk out the nipple
- Prolactin is needed to produce milk
- Oxytocin comes from the posterior pituitary cells
- Prolactin comes from the anterior pituitary cells
What does pulsatile release and continuous administration of GnRH cause?
What is endometriosis?
What does this cause?
How can it be treated?
How can this treatment be used in IVF?
- Pulsatile release of GnRH stimulates LH and FSH secretion
- Continuous administration of GnRH causes suppression of gonadotropin secretion
- Endometriosis is a condition associated with growth of tissue outside of the uterine cavity in response to oestrogens of the menstrual cycle
- This causes pain and infertility
- GnRH analogues are potent therapeutic agents
- By continuously administering GnRH analogues, this inhibits gonadotropin secretion, which reduces oestrogen levels, leading to a decrease on endometriotic tissue formation
- GnRH analogues can be used to suppress gonadotropin secretion before a cycle of IVF
- This allows us to control the menstrual cycle, develop many follicles, and harvest many eggs which can be used in IVF
What are the 3 different types of birth control pill?
How do they work?
- 3 different types of birth control pill:
- Fixed combination OCP (oral contraceptive pill) – dosage of oestrogen and progestin is the same
- Varying dose OCP – 2 or 3 different dosages of oestrogen and progestin
- Progestin-only ‘minipill’ OCP
- Contraceptive steroids can negatively feedback and hypothalamic neurons and gonadotropin cells, and suppress LH and FSH secretion
- This prevents follicular development and the LH surge that stimulates ovulation
- Progestin causes cervical mucous thickening, which reduces uterus and oviduct motility which results in endometrial changes
- This inhibits sperm penetration and reduces chance of implantation of the zygote in the uterine wall.
