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3RD YEAR SYSTEMS: Repro > Embryology > Flashcards

Embryology Flashcards

1
Q

Which system forms a template for reproductive system?

A

The urinary system

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2
Q

When does the genital ridge form?

A

Week 5-6

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3
Q

What structure thickens to become the genital/gonadal ridge?

A

Medial part of the mesonephric ridge

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4
Q

What has to happen in order to produce Indifferent Gonads (not differentiated into a definitive testis or ovary yet) and in time Gonads?

A

Germ cells migrate from the yolk sac, via dorsal mesentery and embed into primitive sex cords (these are formed from proliferation of the epithelium in each Genital ridge)

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5
Q

How does the para-mesonephric duct form?

A
  • Epithelium of the mesonephros invaginates to form a tube.
  • This tube becomes the para-mesonephric duct
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6
Q

Where does the cranial end of the paramesonephric duct open into?

A

The peritoneal cavity

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7
Q

True or false: The paramesonephric duct crosses ventral (anteriorly) to the mesonephric duct

A

True

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8
Q

Where does the paramesonephric duct project into at it’s caudal end?

A

It projects into the dorsal wall of the urogenital sinus

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9
Q

What do the paramesonephric ducts devlop into in the female?

A

The genital tract:

  • Fallopian tubes
  • Uterus
  • Cervix
  • The upper one-third of the vagina.
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10
Q

What happens to the paramesonephric duct in males?

A

It degenerates

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11
Q

What does the mesonephric duct develop into in males?

A
  • Epididymis
  • Vas deferens
  • Seminal vesicle
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12
Q

In males, what structures does the urogenital sinus develop into? (3)

A
  • Bladder
  • Urethra
  • Prostate - outgrowth from the urethra
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13
Q

In females, what structures does the urogenital sinus develop into? (2)

A
  • Bladder
  • Lower part of vagina
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14
Q

What happens to the mesonephric duct in females?

A

It degenerates

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15
Q

How does the indifferent gonad (un-differentiated) know whether to develop into a testis?

A

Sex-determining Region Y (SRY) is a gene found on Y chromosomes that leads to the development of male phenotypes, such as testes.

  • The SRY encodes for a protein called TDF (testis determining factor)
  • Primordial germ cells (within the sex cords of the indifferent gonad) express the SRY
  • TDF makes the indifferent gonad develop into a testis
  • The SRY transforms the primordial cells into Sertoli cells which secrete MIS (Mullerian-inhibiting-substance)
  • Paramesonephric duct degenerates
  • MIS transforms mesenchymal cells between the sex cords to form Leydig cells
  • Leydig cells produce testosterone - male external genitalia
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16
Q

Testis development

A
17
Q

The male external genitalia are formed under the influence of what hormone?

A

Testosterone

18
Q

How does an indifferent gonad develop into an ovary?

A
  • No SRY region
  • No TDF (which results in development of testis)

So, by default the indifferent gonad develops into an ovary

19
Q

Postnatal ovarian development

A
  • There are approx 2 million primordial follicles at birth
  • Many follicles become atretic before puberty (Degenereated)
  • 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
20
Q

Absence of testosterone causes what to happen in females?

A

Degeneration of mesonephros and mesonephric duct

21
Q

During development how do the ovaries descend?

A
  • The ovaries originate on the posterior abdominal wall (T10) and move down to within the pelvis.
  • The movement is arrested by the gubernaculum (formed in development and connects the ovary to the labum majora)
  • Later in pregnancy the gubernaculum becomes the round ligament
22
Q

Descent of the testis

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)
  • The gubernaculum guides the testes through the inguinal canal into the scrotum.
23
Q

What is Gartner’s cysts?

A
  • Most common benign cystic lesions of the vagina.
  • They represent embryologic remnants of the caudal end of the mesonephric duct (should disintegrate in females)
24
Q

What is Cryptorchidism?

A

Parents notice absence of testes in scrotum (cryptorchidism). Reasons for this could be:

  • Undescended
  • Ectopic
  • Retractile testes
  • Absent testes

Managed by Orchiopexy: Surgery to move an undescended (cryptorchid) testicle into the scrotum and permanently fix it there. Orchiopexy typically also describes the surgery used to resolve testicular torsion.

25
Q

What are some complications associated with undescended testis?

A
  • Infertility
  • Malignant transformation (germ cell tumours)
  • Testicular torsion - when tissues around the testis are not attached well causing the testes to twist around the spermatic chord. This cuts off the blood flow to the testicle.
26
Q

What is Orchiopexy?

A
27
Q

What are some anomalies of the paramesonephric duct that can affect females?

A
  • Complete duplication of the uterus
  • Bicornuate uterus
  • Septate uterus (septum in the middle of the uterine cavity)
  • Arcuate uterus - the uterine anomaly that is least commonly associated with reproductive failure.

3RD YEAR SYSTEMS: Repro (34 decks)

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