Embryology of the Repro. System

Question 1

What is the name of the first set of kidneys to develop and where do they develop?

Answer 1

Pronephros - cervical region (doesn’t really function)

Question 2

What is the name of the second set of kidneys to develop and where does they develop?

Answer 2

Mesonephros - thoracolumbar (briefly functional)

Question 3

What is the name of the third set of kidneys to develop and where do they develop

Answer 3

Metanephros - pelvic region (functional)

Question 4

What occurs in genital ridge formation?

Answer 4

At roughly six weeks the mesonephros forms a long ovoid structure in association with thoracic and upper lumbar vertebrae. The medial part of the mesonephric ridge becomes thickened to form a genital/gonadal ridge

Question 5

What happens after the genital ridge is formed?

Answer 5

Germ cells migrate from the yolk sac via dorsal mesentery and embed into the primitive sex cords (formed from the mesenchyme of the genital ridges) and are then known as the indifferent gonads

Question 6

How is the paramesonephric duct formed?

Answer 6

The epithelium of the mesonephros invaginates to formn a tube

Question 7

What happens to the paramesonephric duct

Answer 7

• Funnel shaped cranial end opens into the peritoneal cavity

- Caudally it crosses ventrally to the mesonephric duct and projects into the dorsal wall of the urogenital sinus

Question 8

What happens to the embryological structures in males?

Answer 8

• Gonads form testis
• Mesonephric duct develops into the epididymis, vas deferens and seminal vesicle
• Paramesonephric duct degenerates
• Urogenital sinus forms the bladder, urethra and prostate

Question 9

What happens to the embryological structures in females?

Answer 9

• Gonad forms the ovary
• Mesonephric duct degenerates
• Paramesonephric duct forms the fallopian tube, uterus and cervical part of the vagina
• Urogenital sinus forms the bladder and lower part of the vagina

Question 10

What structure forms the interstitial cells of Leydig?

Answer 10

The mesenchyme between cords

Question 11

How do the testis descend?

Answer 11

• Week 7: Level of T10
• Week 12: level of deep inguinal ring
• Enters scrotum at approx. 39 weeks

Question 12

How do the ovaries descend?

Answer 12

• Week 7: Level 10
• Week 12: Broad ligament
• Round ligament drawn through inguinal canal to attach to labrum majorum

Question 13

What is cryptorchidsm and what are the causes?

Answer 13

• Absence of testes in the scrotum

- Undescended, ectopic, retractile and absent testes

Question 14

What are the complications of undescended testes and how is it treated?

Answer 14

• Infertility, malignant transformation and testicular torsion
• Orchiopexy

Question 15

What is a teratogen?

Answer 15

• An environmental exposure to which the mother is exposed during pregnancy
• A genetic defect passed on to offspring from either parent

Question 16

List the effects of teratogens

Answer 16

• Intrauterine death
• Structural malformations
• IUGR or growth defects
• Neurodevelopmental/ behavioural dysfunction
• Developmental delay
• Carcinogenesis

Question 17

When is a fetus most at risk from teratogens?

Answer 17

Between week 3 and 11

Question 18

Name some substances that are teratogenic

Answer 18

• Alcohol
• Smoking
• Illegal drugs
• Opiates in late pregnancy

Question 19

What is the classic triad for congenital rubella

Answer 19

• Sensorineural deafness
• Eye abnormalities
• Congenital heart disease: pulmonary artery stenosis and patent ductus arteriosus