ILA 10 - reproductive

Question 1

What is the sex determining gene?

What occurs if it is or isnt present?

Answer 1

SRY gene

Presence = Leydig cells release testosterone and so the wolffian duct develops into epididimus, vas def, seminal vesicles
Sertoli cells secrete mullerian inhibiting substance so the mullerian tube regresses

Absence of SRY = no mullerian inhibiting substance so mullerian tube develops into the fallopian tube, uterus and upper third of vagina
absence of testosterone means that the wolffian tube regresses

Question 2

What is another name for wolffian duct and mullerian tube?

Answer 2

Mesonephric = wolffian duct
paramesonephric = mullerian tube

Question 3

Which cells turn into gametes?

Answer 3

germ cells originate from the primitive streak - they migrate to the genital ridge
-12 to 20 weeks = rapid mitotic divison = 5-10 mil oocytes
at 20 weeks = rapid death so 1 mill left at birth

Question 4

Outline the mitotic and meiotic divisions that occur in female repro

Answer 4

1. Mitotic division occurs from 12-20 weeks embryologically
2. Meiosis reduction divison - begins in utero and is arrested at metaphase I
3. LH surge triggers the rest of the reaction to occur
4. Meiosis II - this is an equational division, it is arrected at metaphase II (Single chromosomes align on the metaphase plate) until division occurs after fertilization

Question 5

Describe what happens to genitals in female development

Answer 5

1. Up to 6 weeks = primitive gonads are identical
2. After 6 weeks if SRY gene is absent then the ovaries form and mullerian tube development forms fallopian tube, uterus and upper third of vagina
3. At 7-8 ovaries have formed, mullerian tube fuses forming the uterus and the urogenital sinus develops forming the urethra and lower vagina

Question 6

Describe what happens to genitals in male development

Answer 6

1. Up to 6 weeks primitive gonads are identical
2. After 6 weeks is SRY gene is present then the wolffian tube develops into epi, vas def and seminal vesicle
   mullerian- inhibiting substance results in mullerian tube regression
   Leydig cells produce testosterone, this is converted to DHT and prostate, penis and scrotum develop
3. At 7-8 weeks the epididymis and mesonephric duct (forms vas def) have formed
4. Urogenital sinus forms the urethra
5. AT birth the testes descend into scrotum (influence of androgen through the inguinal canal)

Question 7

Which glands are located in the vulva?

Answer 7

Bartholin’s glands

Question 8

What is the clitoris formed from?

Answer 8

Embryologically derived from the genital tubercle

-formed of erectile corpora cavernosa tissue (this becomes engorged during sexual stimulation)

Question 9

Describe the female repro tract from vagina to end of fallopian tube (and epithelium)

Answer 9

Vagina (strat squamous)
External Os
Cervix (part of uterus….
Internal Os
Uterus (body, fundus, cervix) - simple columnar cells thrown into gland like folds + peg cells
Fallopian tube (intermural, isthus, ampulla - fertilsation, infibrium - with fimbrae)
Ovaries - simple cubodial cells (medulla is secretory, primordial germ cells and follicles at the cortex)

Question 10

Describe the ligaments of the female repro

Answer 10

• Broad ligament (double layered)
• Uterine ligaments
• Ovarian suspensory
• Round ligaments

Question 11

Describe the blood supply and nervous supply of female repro

Answer 11

Nervous supply = T11 and T12 sensory
sympathetic = hypogastric plexus and ovarian plexus
parasym = S2,3,4 (pelvic splanic)

Uterine and Ovarian arteries anastomose
(ovarian off the abdominal aorta, supplies ovary and uterus)
(uterine off the internal iliac supplies, ovary, fallopian tube, uterus, vagina)

Question 12

What is the affect of pituitary hormones on the ovary?

Answer 12

1. Anterior pituitary releases LH and FSH (in response to GnRH from hypothalamus)
2. FSH acts on granulosa cells stimulating them to multiply and produce oestrogen, also stimulates enlargement of antrum
3. LH acts on the theca cells stimulating them to proliferate and produce androgens, (this diffuses into the granulosa cells and is converted to oestrogen via aromatase)
4. 1 week in one follicle becomes dominant
5. The non-dominant cells undergo atresia
6. dominant follicles begins to secrete more oestrogen due to FSH levels which acts to inhibit FSH and LH (oestrogen only inhibits at low plasma levels), FSH decreases the most
7. High plasma concs of oestrogen causes the anterior pituitary to become more sensitive to GnRH which leads to the LH surge (as well as an increase in FSH and LH)
8. LH SURGE CAUSES OVULATION
   This acts on granulosa cells;
   a) they release hormones to make the primary oocyte complete first meiotic division
   b) they produce more fluid which increases atrum size and follicle blood flow
   c) granulosa cells release progesterone and decrease oestrogen production
   d) enzymes and prostaglandins (synthesized by granulosa cells) break down the follicular-ovary membranes - they rupture and release the oocyte to the surface of the ovary = ovulation
   e) the remaining granulosa and theca cells bcome the corpus luteum - which then releases progesterone and estrogen
9. A low LH conc mantains the corpus luteum for 14 days, in a none pregnant women it release large quantities of oestrogen, progesterone and inhibin
   In the presence of oestrogen the progesterone inhibits the secretion of FSH and LH by acting on the hypothalamus
   inhibin acts to decrease FSH concs

Question 13

How does LH surge act on granulosa cells

Answer 13

8. LH SURGE CAUSES OVULATION
   This acts on granulosa cells;
   a) they release hormones to make the primary oocyte complete first meiotic division
   b) they produce more fluid which increases atrum size and follicle blood flow
   c) granulosa cells release progesterone and decrease oestrogen production
   d) enzymes and prostaglandins (synthesized by granulosa cells) break down the follicular-ovary membranes - they rupture and release the oocyte to the surface of the ovary = ovulation
   e) the remaining granulosa and theca cells bcome the corpus luteum - which then releases progesterone and oestrogen

Question 14

Describe the effect of ovarian hormones on the endometrium

Answer 14

Oestrogen = mucus is abundant, watery and clear, causes thickening of endometrium and myometrium (muscle), induces synthesis of progesterone receptors

Progesterone = secreted by corpus luteum, it converts endometrium into actively secretion tissue

• the glands coil and fill with glycogen and blood vessels lengthen and spiral
• thick and sticky mucus - forming a ‘plug’

Question 15

What occurs in the secretory phase?

Answer 15

Endometrium secretes glycogen, followed by glycoproteins and mucopolysaccharides
Mucus thickens and myometrial contractions are inhibited

• arteries thicken and become spiral
• glands become tortuous
• stromal oedema

Question 16

What occurs in the menstrual phase?

Answer 16

Corpus leteum degenerates and causes reduction in progesterone and oestrogen

• this causes constriction of blood vessels
• blood leaks into stroma = reduction of nutrients and oxygen
• smooth muscle undergoes contractions mediated by prostagladins released due to low progesterone and estrogen
• spiral arteries dilate and hemorrhage through the weakened capillary walls
• endometrium is shed!

Question 17

Explain the process of fertilation from coitus to implantation

Answer 17

1. Sperm travels (from seminiferous duct to rete testes to epididymus to vas def to (Seminal vesicles) prostate, to join urethra and ejaculatory duct to the penis
2. Ejaculation (due to semen emptying into urethra and smooth muscle contractions under symp control) occurs propelling semen into the cervix
3. Hormones in the cervix causes capitation (sperm tail is changed from wave-like to whip-like and the cell membrane is altered so it can fuse with egg cell membrane)
4. Travels to ampulla of the fallopian tube via muscular contractions and movement of flagellum
5. Egg is wafted to ampulla via cilia (frimbriae from infundibulum waft)
6. Sperm binds to receptors on zona pellucida and digests a pathway via the acrosomal reaction
7. Sperm binds to receptor on cell membrane, cell undergoes cortical reaction preventing poly spermy and sperm is drawn into the egg
8. Egg completes 2nd meiotic divsion
9. Pro nuceli combine (23 pairs plus XX or XY)
10. Egg undergoes mitotic divisons = clevage, up to 8 cells
11. morella forms and the cells float in the intrauterine fluid
12. Blastocyst forms (around 100 cells), it has a trophoblast layer(hormones and nutrients), inner cell mass (becomes embryo) and central fluid filled cavity
13. Blastocyst is implanted in the uterus around 6 days after implantation

Question 18

Explain the action of hormonal contraceptives

Answer 18

1.Progesterone and oestrogen
= inhibits ovulation, high levels of progesterone = thick mucus, endometrium is inhospitable, levels of estrogen and progesterone inhibit GnRH from hypothalamus = no LH surge = no ovulation

2. Progesterone = thick mucus, no change in hormones so no ovulation
3. Emergency = high dose of estrogen = endometrium erodes and contractions increase

Question 19

Describe hormone levels during pregnacy

Answer 19

1. Throughout pregnancy estrogen and progesterone levels continually rise
2. Ostrogen stimulates growth of uterine muscle mass
3. Progesterone inhibits uterine contractility so that the featus is not expelled prematurely
4. The corpus luetum supplies almost all progesterone and eosotrogen in first 2 months of pregnancy
5. HUMAN CHORIONIC GONADOTROPHIN HORMONE - this is the hormone that allows the corpus luteum to exist, it enters maternal blood stream and is tested in early stages of pregnancy
   - secreted by trophoblast cells, stimulates steroid secretion, peaks at 60-80 days then decreases rapidly
   - very low levels by 3 months and corpus luteum regresses
   - trophoblast cells then secrete higher levels of oestrogen and progesterone
6. maternal ovaries, adrenal glands and fetal adrenal glands secrete androgens - these diffuse to placenta and are converted to oestrogen
7. High levels of estrogen and progesterone inhibit GnRH and therefore LH and FSH
8. Trophoblast cells also secrete inhibin and human placental lactogen
9. In the last few weeks ever increasing eostrogen levels result in smooth muscles synthesizing connexins - these proteins form gap junctions between smooth muscle cells so that the myometrium can undergo contractions
10. Simultaneously the cervix becomes soft and flexible due to enzymatically mediated breakdown of collagen fibres
11. Relaxin is released - softens cartilaginous joints in the pelvis
12. Oestrogen also synthesis receptors of oxytocin - strong stimulator of uterine smooth muscle contraction

Question 20

What does HcG stand for? What secretes it, what is its function

Answer 20

Human chorionic gonadotrophin - tested in pregnancy test

secreted by trophoblast cells, allows corpus luteum to persist

Question 21

What does inhibin do

Answer 21

Suppresses FSH

Question 22

What does human placental lactogen do?

Answer 22

Mobilise fats from maternal adipose tissue and stimulates glucose production in the liver
-also stimulates lactation in breast development

Question 23

Describe the stages of paturition

Answer 23

1. Latent (dilation occurs, head causes a breach at 10cm, water breaks due to amniotic fluid)
2. Active I = contractions push baby down uterus to cervix and vagina/birth canal - contractions occur every 5 mins
3. Fetal explusions = crowning of head, rotation and delivery
4. Post-partum = after birth of placenta

Question 24

Which hormones are involved in lactogensis

Answer 24

PRF from hypothalamus stimulates prolactin release from anterior pit = secretory bursts of prolactin stimulate breast to produce more milk
Oxytocin from posterior pituitary = allows milk let down
-Dopamine inhibits prolactin release

Question 25

Describe the hormonal control of male repro

Answer 25

1. Every 90 mins hypothalamus releases GnRH
2. anterior pit releases LH and FSH
3. FSH acts on sertoli cells - they release inhibin -ve feedback to anterior pit of FSH
4. LH acts on leydig cells - they release testosterone (uptaken into testes/BTB by androgen-binding-protein) - testosterone acts on sertoli cells stimulating spermatogenesis
   Testo - inhibits LH from ant pit and GnRH from hypothalanus

Question 26

Describe the process of spermatogenesis

Answer 26

Spermatogonia (mitosis @ puberty) 
Primary spermatocytes (meiotic I) - small dense nuelci
Secondary spermatocytes (meiotic II)
Spermatids (mature...)
Spermatozoa - elongated heads

as they develop they move from basal compartent upwards…

Question 27

What is the function of Sertoli cells

Answer 27

• Form BTB
• Supportive, phagocytic
• secrete luminal fluid
• secrete inhibin (inhibits FSH)
• secretes mullerian inhibiting substance
• contains androgen-binding-protein which binds to testosterone, crosses BTB to enter tubule - maintains high tesosterone levels :)

Question 28

What does the spermatic cord do?

Answer 28

Binds the vas def, blood vessels and nerves
-Passes from the testes through inguinal canal, enters abdomen and contiunes behind bladder base, combines with seminal vesicle, through prostate to from urethra/ejuaculatory duct to the penis