Reproductive System Flashcards
What are the two gonads?
Female- ovaries
Male-testes
Describe the male gonad?
male gonad.
1- Testes
2- Each testis is surrounded by the tunica vaginalis
3- Suspended in scrotum to keep cooler than body temperature, usually at ~35C
4- Sperm passes through the seminiferous tubules to the epididymis
5- Scrotum is rugose (wrinkled) and contains dartos (smooth) muscle. It is divided by septum.
Describe the female gonad
1- Ovaries (and uterus)
2- Each ovary lies on a lateral pelvic wall
3- During ovulation, the ovum is picked up by the fimbriated end of the uterine or Fallopian tube
4- When fertilized, the ovum is implanted in the uterus and grows there
5- The uterus is a pear-shaped, central pelvic organ where the fetus grows
6- Uterine ligaments pass from the uterus and cervix to the sacrum
What do male gonads produce and how?
Sperm by spermatogenesis
What do female gonads produce and how?
Oocytes by oogenesis
What is the hypothalamic-pituitary-gonadal axis?
GnRH, LH and FSH target ovaries and Leydig cells to release progesterone/oestradiol and testosterone respectively
What two groups of hormones do ovaries release?`
1- Progestins
2- Oestrogens
What are the main hypothalamic areas involved in ovarian control?
1- Preoptic nucleus neurons
2- Supraoptic nucleus
What is GnRH?
1- Gonadotrophin-releasing hormone
2- Released from preoptic nucleus neurons and supraoptic nucleus neurons
3- Produced as a prohormone which is later on modified into its active form
4- Secreted into hypophyseal portal system
Where is GnRH released into?
1- Hypophyseal portal system
2- To anterior pituitary gonadotrobes
Why is GnRH release pulsatile (burst-like manner)?
1- Requires less energy
2- Does not desensitise target tissue receptors
3- Can be influenced by stress and other inputs
What is the role of anterior pituitary gonadotrobes?
1- Receive GnRH from hypophyseal portal system
2- Secrete LH and FSH to targer the gonads
What are the five different stages of development of oocytes?
1- Primordial 2- Primary 3- Secondary 4- Tertiary 5- Graafian follicles
Where are ovarian endocrine functions found?
1- Theca cells
2- Granulosa cells
What are theca cells?
1- Superficial layer of the follicle
2- Contain LH receptors
3- Convert cholesterol to prenenelone
4- Produce androstenedione and testosterone
What are granulosa cells?
1- Layer deeper to theca cell
2- Increases in size during primary to secondary follicle development
3- Contain LH and FSH receptors
4- Convert cholesterol to prenenelone
5- When FSH is received, activates aromatase which facilitates formation of oestradiol
6- Produce and oestradiol
When do thecal and granulosa cells interact?
Thecal cells donate testosterone androstenedione to granulosa cells so they can produce estradiol which is released into circulation
When does oogenesis begin?
1- Fetal stage of female
2- Primordial germ cells, or oogonia, increase in number
3- Many oogonia mature into oocytes
When do oocyte numbers reach their maximum?
~20 weeks gestation
What are the three main oestrogens?
1- Oestradiol
2- Oestrone
3- Oestriol
What is the effect of oestrogens on bone?
Increase bone growth via osteoblasts
What is the effect of oestrogens on the endocrine system?
Increase progesterone responses
What is the effect of oestrogens on the liver?
1- Increase clotting factors
2- Increase steroid-binding proteins
3- Decrease LDL
4- Increase HDL
What is the effect of oestrogens on the reproductive organs?
1- Increase uterine growth
2- Increase vaginal and fallopian tube growth
3- Increase breast growth
4- Increase cervical mucus secretion
5- Increase LH receptors on granulosa cells
What are interrelated feedback loops?
Mechanism which provides negative feedback until midcycle, where it switches to positive feedback
What causes the mid-cycle shift of negative feedback to positive feedback?
1- Receptors, such as GnRH receptors in the anterior pituitary, increase in number and are regulated in response to increased oestrogen levels
What comes as a result of the mid-cycle shift of negative feedback to positive feedback?
LH and FSH surge prior to ovulation
What are the two main types of progestins?
1- Progesterone
2- 17α-hydroxyprogesterone
Where are progestins produced?
1- Theca cells
2- Granulosa cells
What are progestins’ half life?
5 minutes in circulations
What regulates progestin secretion?
Oestrogen secretion
What is the effect of progestins on breasts?
1- Increased lobular development
2- Decreased milk production
What is the effect of progestins on the reproductive organs?
1- Decreased endometrial growth
2- Increased endometrial secretions
3- Mucosal secretions become thicker
What is the effect of progestins on the body temperature?
1- Increased internal temperature
What are the two parts of the menstrual cycle?
1- Ovarian cycle
2- Endometrial cycle
What are the two phases of the ovarian cycle?
1- Follicular phase
2- Luteal phase
What happens in the follicular phase?
1- Development of mature Graafian follicle
2- Development of secondary oocyte
What happens in the luteal phase?
1- Dominated by corpus luteum synthesising and secreting oestrogen and progesterone which are needed for implantation and maintenance of fertilised oocytes
2- Corpus luteum then regresses and degenerates in 10 to 12 days if no fertilisation occurs
What happens to the corpus luteum if no fertilisation occurs?
Regresses and degenerates in 10-12 days
What hormones are needed for the implantation and maintenance of a fertilised oocyte?
1- Progesterone
2- Oestrogen
What are the three phases of the endometrial cycle?
1- Proliferative phase
2- Secretory phase
3- Menstruation (if no conception)
What happens in the proliferative phase?
1- Endomertial growth is mediated by increased oestrogens levels
2- Endometrium grows from 1-2mm thick to 8-10 mm thick
3- Blood vessels and glands grow
4- End of phase is marked by ovulation
5- Progestins aid in conversion from proliferative to secretory phase
What is the role of progestins in the endometrial cycle?
1- Aid in conversion from proliferative to secretory phase
At what phase does ovulation happen?
End of proliferative phase
What happens in the secretory phase?
1- Maturation of endometrium due to decreased levels of oestrogens
2- Mucus glands develop more fully
3- Blood vessels and glands increase surface area
What happens in menstruation?
1- If no conception/fertilisation occurs, endomertrial lining is replaced
2- Spiral arteries vasoconstrict
3- Local ischaemic injury
4- Inflammatory cell infiltration
What is lactation?
Milk production and secretion
How does breast tissue undergo growth during puberty?
Female gonadal hormones
How does breast tissue undergo growth during pregnancy?
1- Oestrogens
2- Progestins
3- hCG (human chorionic gonadotrophin) from fetus
What is milk production mediated by?
Prolactin
What is milk ‘let-down’ mediated by?
Oxytocin
Where are testicular endocrine functions found?
1- Leydig cells
2- Sertoli cells
What hormones cause embryonic development of male genitals and accessory organs?
1- Testosterone
2- Dihydrotestosterone
What are Leydig cells?
1- Cells present next to seminiferous tubules
2- Produce testosterone when stimulated by LH
3- Sends testosterone to Sertoli cell
What are seminiferous tubules?
1- Coiled tubules found in the testes
2- Produce sperm
3- House Sertoli cells
What does FSH stimulate in the testes?
Activation of aromatase to produce estradiol
What is the role of estradiol in the testes?
Help regulate protein synthesis in the nucleus of Leydig cells
What are the five stages of development of sperm?
1- Spermatogonia 2- Primary spermatocytes 3- Secondary spermatocytes 4- Spermatids 5- Spermatozoa
What regulates spermatogenesis?
Testosterone
What is the effect of testosterone on bone?
1- Increased growth of bone
2- Increased growth of connective tissue
What is the effect of testosterone on muscle?
1- Increased growth of muscle
2- Increased growth of connective tissue
What is the effect of testosterone on the reproductive organs?
1- Increased growth and development of testes
2- Increased growth and development of prostate
3- Increased growth and development of seminal vesicles
4- Increased growth and development of penis
5- Increased growth of facial, axillary and pubic hair
6- Increased growth of larync
7- Increased levels of spermatogenesis
What is the effect of testosterone on skin?
1- Increased sebaceous gland size and secretions
