Reproductive System Flashcards
What is a gonad?
An organ that produces gametes
What makes up the male gonad?
Testis and epididymis
Where are the testis found and what are they surrounded by?
In the scrotum (to keep cool)
Tunica vaginalis
What route does the sperm take in the testis?
Sperm passes from the seminiferous tubules to the epidimysis
Describe the structure of the scrotum
- Skin is rugose
- Has a midline raphe
- Contains dartos (smooth) muscle and is divided by a septum
List the female genital organs
Ovary Uterine Tube Uterus Fundus of uterus Cervix Vagina
Where is the ovary located?
Lateral pelvic wall
Where does ovulation occur?
In the peritoneal cavity, where the ovum is picked up by the fimbriated end of the uterine (/Fallopian) tube aka fimbrae
What is ectopic pregnancy and why does it occur?
The egg is not picked up by the fimbrae and is embedded onto other parts of the abdomen
6 weeks into pregnancy, it grows big enough to damage the internal organs
Where is the blood supply of the ovary coming from?
Its blood supply is linked to the back of the abdomen
What is the function of the uterus?
A pelvic organ for implantation of the fertilised ovum and growth of the foetus
How is the uterus tethered in place?
By supportive uterine ligaments - connecting the uterus and cervix to the sacrum, pubis and lateral pelvic walls
What do female gonads produce and by what process?
Oocytes (eggs) by oogenesis
What do male gonads produce and by what process?
Sperm by spermatogenesis
What are the gonadal hormones involved in?
- Gamete production
- Supporting conception, pregnancy and lactation
What controls gonads?
Hypothalamic-pituitary-gonadal axis
What is the Hypothalamic-Pituitary-Gonadal axis made up of?
Hypothalamic signalling hormone and Pituitary hormones
What is the Hypothalamic signalling hormone?
Gondadotropin-releasing hormone (GnRH) (peptide hormone)
What are the Pituitary hormones?
- Luteinising hormone (LH)
- Follicle stimulating hormone (FSH)
What happens when ovaries are targeted by LH and FSH?
An ovum is released monthly, and oestrogens/oestodiol and progestins/progesterone are secreted
What are the main hypothalamic areas involved in ovarian control?
Preoptic nucleus and Supraoptic nucleus
Describe the production of the peptide hormone GnRH
- Production is by Preoptic nucleus neurons and Supraoptic nucleus neurons
- Produced as prohormone, then modified to active form
- Secreted into hypophyseal portal system
Describe the release of the peptide hormone GnRH (Gonadotropin-releasing hormone)
Release is pulsatile/not constant
- Requires less energy
- Does not desensitise target tissue receptors
- Stress can influence secretion (and therefore the menstrual cycle too)
Describe the delivery of GnRH
Delivered via the hypophyseal portal circulation to the anterior pituitary gonadotropes; these then result in the production of FSH and LH, which target the gonads
Summarise how the GnRH controls the ovaries
- GnRH is produced from prohormones, made active, and is then secreted
- GnRH is released by pulsations
- GnRH is delivered to the anterior pituitary gonadotropes
- Gonadotropes secrete FSH and LH
- FSH and LH target the gonads
Describe the follicles of the ovary
The ovary contains follicles of various stages (e.g. primordial, primary, secondary, tertiary, Graafian), but the most important is Graafian follicles in the endocrine ovaries
Made up of the primary oocyte, antrum, theca cells and granulosa cells
Describe the cells making up the Graafian follicle
Theca cells
- Outer layer of cells
- Can be externa or interna
- Have LH receptors
- Convert cholesterol into prenenolone, then produce the hormones androstenedione and testosterone
Granulosa cells
- Inner layer of cells
- Have LH and FSH receptors
- Convert cholesterol into prenenolone and activate aromatase, then produce androstenedione, testosterone and oestradiol (the oestrogen hormone)
Describe the beginning and end of oogenesis
Starts in the embryo for females
- Premordial germ cells (oogonia) increase in number, and many mature into oocytes
At 20 weeks of pregnancy, oocyte numbers reach maximum numbers
- from then on, oocyte numbers start declining until exhausted (menopause)
What are the three main oestrogens?
- Oestradiol
- Oestrone
- Oestriol
Describe the secretion/feedback regulation of oestrogens
Feedback shifts from -ve to +ve, then shifts back to -ve
This is because:
- Oestrogen levels increase
- Results in upregulation of receptors (Eg. GnRH in anterior pituitary)
- Results in increased production of LH and FSH prior to ovulation
Describe progestins
- Progesterone
- Produced in theca and granulosa cells
- Has a short half-life in circulation (5 minutes)
- Secretion regulation is intrinsically linked to oestrogen secretion
Summarise up the hormonal behaviour of the reproductive system
Start of the ovarian cycles (takes 14 days)
- Hypothalamus produces sex hormone GnRH about once a month
- GnRH stimulates the anterior pituitary and the production of LH and FSH
- FSH stimulates the growth of one single follicle
- That follicle secretes its own oestrogen that simulates it even more to grow faster
- The secretes oestrogen stimulates the anterior pituitary to secrete LH to finish the job
- Oocyte matures and leaves the follicle
- Damaged follicle becomes the corpus luteum and secretes progesterone to stop the secretion of FSH and LH
