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Where do the gonads develop from? What type of embryonic tissues are involved?

The urogenital ridge (intermediate mesoderm) and primordial germ cells (from the yoke sac)

1

How is male female differentiation determined in the gonads?

Males have SRY gene expressed in primordial germ cells
Triggers degeneration of the cortex and development of the medulla
Releases androgens which maintain mesonephric duct and mullarian inhibiting substance degrading the paramesonephric

Females lack SRY in no primordial germ cells
Cortex develops and medulla degrades
Lack of androgens results in degradation of mesonephric duct, lack of mullarian inhibiting substance results in persistence of paramesonephric duct.

2

What is the embryonic origin of the female internal genitalia?

Paramesonephric ducts fuse, and the (uterine) septum between them breaks down forming the uterus, cervix and upper vagina. The urogenital sinus (external) begins to cavitate forming the sinovaginal bulb then the lower vagina.

3

What are the parts of the indifferent genetalia? What do they form in males and females?

Genital tubercle - glans penis / clitoris
Genital folds - shaft, spongy urethra / labia minora, urethra, vagina
Genital swellings - scrotum / labia majora

4

How do the testis anchored to the abdomen? How do they descend?

Urogenital mesentery becomes caudal genital ligament attaching to posterior abdo
Gubernaculum descends from caudal testis to inguinal region.
Testis starts to descend down route of gubernaculum
Gubernaculum extends to scrotum
Outpouching of peritoneum follows anteriorly (processus vaginalis)

5

Why does the ovary stop descending?

Mechanical obstruction by mullarian duct

6

What forms the ligaments of the ovary?

Cranial genital ligament - suspensory lig. of ovary
Caudal genital ligament - ovarian lig. and round lig. of uterus
Parietal lateral plate mesoderm - broad ligament of uterus

7

Describe female gamete formation

Primordial germ cells
Replicate to 7million then die to 2 million
Oogonia
Enter meiosis then arrest at prophase 1
Primary oocyte
Surrounded by flat follicular cells
Primordial follicle
BIRTH
Most primordial follicles die leaving 40000
PUBERTY
1/12 20 primordial follicles start to mature
Follicular cells thicken and become cuboidal with multiple layers (granulosa). Secrete zona pellucidia. Connective tissue shell (theca)
Pre antral follicle
Fluid collects in granulosa
Antral follicle
Theca differentiates into theca interna and theca externa. Antrum expands
Mature (graffian) follicle.
Meiosis progresses to prophase 2
Primary oocyte to secondary oocyte and polar body
Ovulation

8

What are the stages of the menstrual cycle with rough times?

Follicular / proliferative - 0 to 12 days (some variability)
Ovulation - 12 to 14 days
Luteal / secretory - 14 to 28 days (fixed)

9

Describe spermatogenesis

Primordial germ cells on sex cords
Spermatagonia
BIRTH
PUBERTY
Sex cords hollow forming seminiferous tubules
Spermatagonia cluster around the edge
Some spermatagonia differentiate to a1 spermatagonia
Undergo a fixed number of mitotic divisions all remaining joined by cytoplasm
Spermatocytes
Meiosis
Spermatids
Release into tubules
Maturation
Spermatozoa

10

What are hormones that influence levels of other hormones called?

Trophic

11

Describe the release of GnRH

Released into hypophesal portal circulation from hypothalamus median eminence. Pulsetile, slightly more frequent in the morning.

12

What characteristics are required of male sex hormone production to meet their reproductive needs?

Steady hormone concentration to ensure continuos sperm production. Slightly raised levels in early morning. Slightly raised levels when stimulated and reduced when stressed.

13

What do LH and FSH do in male gonads?

LH acts on laydig cells to release testosterone
FSH acts on sertoli cells to stimulate spermatogenesis and also releases inhibin

14

What do testosterone and inhibin do in males?

Testosterone has regulatory and determinative effects.
Regulatory includes maintenance of repro tract, behaviour, promoting spermatogenesis by acting on sertoli cells alongside FSH
Determinative effects include secondary sexual characteristics
Testosterone feedback negatively on GnRH and LH + FSH (reduces secretion of GnRH and sensitivity of Gonadotrophin to GnRH).

Inhibin feeds back negatively on FSH

15

Explain the hormone changes in the proliferative / follicular phase of mensturation and the effects on the oocyte.

Initially low oestrogen and inhibin therefore uninhibited GnRH secretion.
As GnRH secretion increases increased LH and FSH
FSH causes granulosa to develop and inhibin to be released
LH causes theca to release androgens which are converted to oestrogens by granulosa
As follicle grows oestrogen and inhibin increase. Oestrogen inhibits GnRH and reduces sensitivity of gonadotrophs.
LH falls a bit but FSH falls markedly preventing further oocytes from developing. Oestrogen continues to rise as the follicle grows.

16

What is the effect of rising oestrogen during the proliferative/follicular phase on the female?

Endometrial proliferation (stratum basalis producing a new stratum functionalis. Arterioles lengthen and penetrate the new stratum functionalis)
Myometrium grows and contracts more
Cervical mucus becomes thin and alkaline
Systemic changes in hair, skin, metabolism.

17

What happens during ovulation?

Oestrogen levels climb. Switches to +ve feedback at hypothalamus and pituitary increasing LH levels +++. LH surge. LH breaks down theca externa collagen causing rupture and ovulation. This leaves the reminents of the follicle, the corpus haemorrhagicum.
As follicle ruptures oestrogen levels decrease, back to -ve feedback, LH and FSH drop.

18

What occurs in the secretory/luteal phase?

Corpus haemorrhagicum to corpus luteum.
Corpus luteum secretes oestrogen, progesterone and relaxin
Oestrogen decreases GnRH amount per pulse, progesterone decreases number of GnRH pulses and prevents any positive feedback from oestrogen.
O+P cause thickening of endometrium, thick acidic cervical mucus, increased body temp, metabolic changes, mammary changes.

19

How long does the corpus luteum last if no hCG is detected? What does it become? What happens?

14 days - becomes corpus albicans.
Decrease o+p, decrease blood supply to placenta, menses. Cycle starts again.

20

What are the strands of connective tissue that support the breast called? What causes laxity?

Suspensory ligaments
Age, strain

21

What is the structure of the glandular tissue of the breast?

Alveoli into lobules into 20 lobes
Lobes to secondary tubules to mammary duct to lactoferrous sinus to lactoferrous duct to nipple.

22

What determines breast size?

Amount of subcutaneous fat

23

What is the lymphatic drainage of the breast?

Sub areolar lymphatic plexus
Most to the axillary (pectoral), some to supra clavicular or deep cervical. Some medially to the parasternal

24

What is the histology of the ovaries?

Cortex with germ cells
Medulla connective tissue, blood vessels and nerves

25

What are the areas of the Fallopian tubes? What are their histology?

General - mucosa, lamina propria, muscular externa and serosa.

Fimbria
Infundibulum
Ampulla - heavily folded, bilayered muscle, cilliated columnar
Isthmus - lightly folded, trilayered muscle, peg cells
Intramural

26

What are the layers of the uterus?

Compact and spongy stratum functionalis (endometrium)
Stratum basalis (endometrium)
Myometrium

27

What is the histology of the cervix?

Near the internal os - simple columnar
Near the external os - non keratanized stratified squamous

Junction is the squamatocolumnar junction.

28

What makes pre puberty and puberty distinct?

The repro system could work pre puberty but GnRH secretion is low (thus low LH and low sex steroids).

29

What triggers puberty?

Unknown - something from the brain
Maybe body weight - 47kg trigger for menarch (though actually proportion of genetically expected weight) possibly signalled by leptins.
Maybe light levels producing melatonin from pineal gland