Reproductive Embryology

Question 1

Give a brief summary of development from 1-9 weeks

Answer 1

Week 1 and 2 - implantation and cell proliferation

Week 3 - gastrulation, neuralation and somite formation

Week 4-8 - organogenesis

Week 9 onwards - maturation of organ systems

Question 2

How is reproductive organogenesis different fro normal embryology?

Answer 2

It extends beyond 8 weeks and even the post-natal period

Question 3

Urinary recap:

What three sets of kidneys form during foetal development?

Answer 3

Pronephros

Mesonephros

Metanephros

Question 4

Urinary recap:

Describe the location of each sets of kidneys and their functionality during development

Answer 4

Pronephros - cervical region - vestigial (not functional)

Mesonephros - thoracic-lumbar region - briefly functional

Metanephros - pelvic region (functional)

Question 5

Urinary recap:

What is the predecessor structure to the metanephros?

Answer 5

Ureteric bud

Question 6

What is the cloaca?

Answer 6

The terminal part of the foetal gut tube

Question 7

The cloaca divides to outline what two cavities

Answer 7

Anteriorly: urogenital sinus

Posteriorly: rectum

Question 8

Where does the cloaca drain?

Answer 8

Maternal systemic circulation

Question 9

What duct drains into the urogenital sinus?

Answer 9

Mesonephric duct

Question 10

What week does genital development begin?

Answer 10

5th-6th

Question 11

What happens to the mesonephros to kick off genital development?

Answer 11

Long ovoid structure (mesonephric ridge develops) - the medial part of this becomes thickened into the genital/gonadal ridge

Question 12

Describe the epithelium of the gonadal ridge; what structure does it form

Answer 12

Formed from intermediate mesoderm and forms the primary sex cords

Question 13

What type of cells migrate into genital ridge to form the indifferent gonad?

Answer 13

Germ cells from the yolk sac (itself formed from outer lining of the blastocyst and therefore undifferentiated)

Question 14

The epithelium of what structure invaginate to form a tube?

Answer 14

Mesonephros

Question 15

What structure is formed from the invagination of the mesonephric duct?

Answer 15

Paramesonephric duct

Question 16

What are the alternative names for the paramesonephric and mesonephric ducts?

Answer 16

PMN duct = Mullerian duct

MN duct = Wolffian duct

Question 17

The PMN duct develops on what side of the gonads/MN duct

Answer 17

Lateral

Question 18

The funnel shaped cranial end of the PMN duct opens into what cavity?

Answer 18

Peritoneal cavity

Question 19

The PMN duct crosses the MN duct on what side and drains into the dorsal wall of what cavity?

Answer 19

Ventrally crosses the MN ducts and projects into the urogenital sinus

Question 20

In males the gonads form what?

Answer 20

Testes

Question 21

In males, what are the fates of the MN duct, PMN ducts and urogenital sinus

Answer 21

MN duct - epididymus, vas deferens and seminal vesicles

PMN duct - degenerates

Urogenital sinus - bladder, urethra and prostate

Question 22

In females what do the gonads form?

Answer 22

Ovaries

Question 23

In famles, what are the fates of the MN duct, PMN duct and the urogenital sinus?

Answer 23

MN duct - degenerates

PMN duct - fallopian tubes, uterus, cervix

Urogenital sinus - bladder and lower vagina

Question 24

OSPE help:

If there is a pin in the interstitium of the testes, what is the answer?

Answer 24

Leydig cells (testosterone producing)

Question 25

How does the indifferent gonad know to develop into testes?

Answer 25

Y chromosome SRY codes for TDF (testis determining factor)

Question 26

What other sex determining functions does SRY code for?

Answer 26

Primordial supporting cells express SRY Transforms them into Sertoli cells S cells secrete MIS (Mullerian-inhibiting-substance) - further develops male genitalia

Question 27

What are the functions of MIS?

Answer 27

Cause PMN duct to degenerate and transforms mesenchymal cells between sex cords into Leydig cells

Question 28

What gestational week are gonads differentiated in the male foetus?

Answer 28

7th week

Question 29

What is the action of TDF?

Answer 29

Stimulates primary sex cords which extend into the medulla and form seminiferous tubules branching into the rete testes

Question 30

What are the rete testes?

Answer 30

The rete testis is an anastomosing network of delicate tubules located in the hilum of the testicle

Question 31

Describe the change of epithelium in the developing testis

Answer 31

Surface epithelium (mesothelium) is lost when thick capsule forms (tunica albuginea)

Question 32

What are the three male sex glands?

Answer 32

Seminal vesicles, prostate, external male genitalia

Question 33

How are seminal vesicles formed?

Answer 33

Outgrowth from caudal end of the MN duct

Question 34

How is the prostate formed?

Answer 34

Outgrowths from urethra from urogenital sinus

Question 35

What substance causes the external male genitalia to be developed?

Answer 35

Formed under the influence of testosterone

Question 36

How does female gonadal development differential from male development?

Answer 36

No Y chromosome, no SRY region therefore no TDF and gonads develop into ovaries

Question 37

What are the two distinct phases of development of the ovaries?

Answer 37

Pre-natal and Pubertal

Question 38

Outline the pre-natal ovaries development

Answer 38

Primary sex cords degenerate and primary germ cells remain Secondary sex cords develop and are incorporated around the germ cells Meiosis is arrested and waits for puberty

Question 39

Approx how many follicles is a woman born with?

Answer 39

Approx. 2 million

Question 40

What is the fate of many of a woman follicles before puberty?

Answer 40

Many become atretic

Question 41

After puberty, what happens to these follicles?

Answer 41

Hormonal influences causes maturation of 12-15 of these follicles per 28 day cycle

Question 42

How many of the stimulated follicles are ovulated?

Answer 42

One (normally)

Question 43

Outline the development of the tubular components to the female reproductive system

Answer 43

Absence of testosterone causes degeneration fo MN and MN duct PMN duct develop into female genital tract

Question 44

What is the fate of the cranial end of the PMN duct?

Answer 44

Open funnel end becomes associated with the ovary

Question 45

What is the fate of the caudal end of the PMN duct?

Answer 45

Otherwise known as the uterovaginal primoridium, becomes the uterus and superior part of the vagina

Question 46

Outline the descent of the testes

Answer 46

Week 7 - T10 (diaphragm undescended) Week 12 - level of deep inguinal ring (remains until 7th month) Enters scrotum just prior to birth (39 weeks)

Question 47

Outline the descent of the ovaries

Answer 47

Week 7 - T10 Week 12 - Broad ligament forms Round ligament drawn through inguinal canal to attach to the labrum majorum

Question 48

What is cryptorchidism?

Answer 48

Absence of testis in the scrotum

Question 49

What are the causes of cryptorchidism?

Answer 49

1. Undescended 2. Ectopic 3. Retractile testes 4. Absent testes

Question 50

What are the complications of cryptorchidism?

Answer 50

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

Question 51

List some anomalies of the female reproductive tract

Answer 51

1. Complete duplication 2. Septate uterus 3. Bicornuate uterus 4. Arcurate uterus