Reproductive embryology Flashcards

1
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3
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4
Q

What does the intermediate plate mesoderm form?

A

The urogenital system

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5
Q

What does the inner cell mass differentiate into?

A

3 layers- Ectoderm, mesoderm and endoderm

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6
Q

What are the names for the 3 kidneys that develop?

A

Pronephros – cervical region – vestigial

Mesonephros – thoracolumbar region – briefly functional

Metanephros – pelvic region – functional

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7
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9
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10
Q

When does the genital ridge form?

A

At about 6 weeks mesonephros forms a long ovoid structure in association with thoracic and upper lumbar vertebrae

Medial part of mesonephric ridge becomes thickened to form a genital/ gonadal ridge.

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11
Q

What do germ cells migrate into genital ridge to make?

A

Indifferent gonad

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12
Q

What happens in week 6 of embryology to the germ cells?

A
  • Germ cells migrate from yolk sac, via dorsal mesentery, and embed into primitive sex cords (formed from mesenchyme of genital ridges
  • This structure is known as the indifferent gonad (why?)
  • No migration of germ cells - no gonads
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13
Q

What is the paramesonephric duct?

A

Epithelium of the mesonephros invaginates to form a tube.

This tube becomes the para-mesonephric duct

Develops lateral to developing gonads and mesonephric duct

Funnel shaped cranial end opens into peritoneal cavity

Caudally, cross ventral to mesonephric ducts

This projects into dorsal wall of urogenital sinus

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14
Q

What do the indifferentated gonad become>

A

Mesonpehric duct- Wolffian duct

Then paramesonephric duct- Mullerian duct

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15
Q

What happens in the males to form differentiated gonads?

A
  1. Gonad forms testis
  2. Mesonephric duct develops into epididymis, vas deferens, seminal vesicle,
  3. Paramesonephric duct degenerates
  4. Urogenital sinus forms bladder, urethra; and prostate
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16
Q

What happens in the females to form differentiated gonads?

A
  1. Gonad forms the ovary
  2. Mesonephric duct degenerates
  3. Paramesonephric duct forms fallopian tube, uterus, cervix part of vagina
  4. Urogenital sinus forms bladder and lower part of vagina
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17
Q

How does the indifferent gonad know whether to develop into a testis or an ovary?

A
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18
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19
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20
Q

How does the testis develop? From week 5 to 7

A

Wk 5 – primary sex cords, medulla and cortex

Wk 6 primordial germ cells incorporated into primary sex cords

Wk 7 – TDF stimulates primary sex cords à extend into medullaà seminiferous cordsà tubules

21
Q

How does my seniferous cords branch?

A

Ends anastomose to make rete testis of medulla

22
Q

When is the surface epithelium lost?

A

When thick capsule forms (tunica albuginea of adult testis)

23
Q

What gives rise to intersitial cells of leydig?

A

Mesenchyme

24
Q

What happens to testis developement at week 8?

A

Leydig cells produce testosterone and other hormones which stimulate masculine differentiation of mesonephric ducts and external genitalia

In males, paramesonephric duct degenerates

25
Q

Which of these is an image of the testis prepubertal and which is post pubertal

A
26
Q

What are the male sex glands?

A

Seminal vesciles- Outgrowth from caudal end of mesonephric duct

Prostate- Outgrowth(s) from urethra (from urogenital sinus)

Male genitalia is formed under the influence of testosterone

27
Q
A
28
Q

What is involved in development of the gonad?

A

Indifferent stage

In the presence of TDF- gonad develops into a testis

In its absence gonad develops into an ovary (by default)

29
Q

What is differences in a female foetus from a male foetus?

A

No SRY region

No TDF

By default the indifferent gonad develops into an ovary

30
Q

What is involved in development of the ovary?

A

Primary sex cords degenerate (leaving the primordial germ cells)

By 10 weeks secondary sex cords develop from surface epithelium

Primordial germ cells become incorporated into them

Primordial germ cells then bud off with single surrounding layer of cortical cord cells to form primordial follicles (from ~16 weeks)

Active mitosis of these early primordial follicles to form additional follicles

By 7th month all follicles have formed

Oocytes enter meiosis and arrested in prophase 1st meiotic division

Some follicular atresia by birth

31
Q

What is the postnatal ovarian development?

A

~2 million primordial follicles at birth

Many follicles become atretic before puberty

After puberty, hormonal influences stimulate 12-15 follicles, per 28 day cycle, to develop

Only one follicle (normally) reaches maturity and ovulation

Continues until the menopause

32
Q

What kind of ovary is each?

A
33
Q

Where do the tubular components of the female reproductive system come from?

A

Absence of testosterone causes degeneration of mesonephros and mesonephric duct

Paramesonephric ducts develop to give rise to female genital tract

34
Q

What is the origin of female genital tract?

A

Cranial (open funnel) end of paramesonephric duct becomes associated with ovary

Caudal end of paramesonephric duct (uterovaginal primordium) becomes uterus and superior part of vagina

Inferior part of vagina from urogenital sinus

(Mesonephric duct degenerates)

35
Q

Where do gonads initally form?

A

In lumbar region, so positional changes occur as development takes place

36
Q

How do the testis develop?

A
  • Week 7 – Level of T10 (Diaphragm undescended)
  • Week 12 – Level of deep inguinal ring (remains until 7th month)
  • Enters scrotum just prior to birth (39 weeks)
37
Q

How do the ovaries develop?

A
  • Week 7 – Level of T10
  • Week 12 – Broad ligament
  • Round ligament drawn through inguinal canal to attach to labrum majorum
38
Q

What is the fibrous cord called?

A

Gubernaculum

39
Q

Understnad this diagram

A
40
Q

The following aspects are linked to the descent of the gonads:

A
  1. Formation of the larger inguinal canal in males
  2. In the female – the presence of the round ligament and its passage through the inguinal canal
41
Q
A
42
Q

What is cryptochordisism?

A

Hidden testis

43
Q

What are the types of cryptorchodism?

A

Undescended

Ectopic

Retractile testes

Absent testes

44
Q

What are the complications of undescended testis?

A
  1. Infertility
  2. Malignant transformation (germ cell tumours)
  3. Testicular torsion
45
Q

What is shown in blue and if it does not degenerate in women wjhat can it form?

A

Mesonephric duct is in blue

May not degerate so may forms cysts

These can have an impact on fertility of the women

46
Q

What anomaly is this?

A

Complete duplication

47
Q

What anomaly is this?

A

Bicornuate uterus

48
Q

What anomaly is this?

A

Septate uterus

49
Q

What anomaly is this?

A

Arcurate uterus