Lecture 3 - Development Of The Reproductive Tracts

Question 1

What are the 3 stages of development before birth?

Answer 1

Pre-embryonic period
Embryonic period
Fetal period

Question 2

What is the time period for the pre-embryonic period?

What happens in this time period?

Answer 2

Conception to week 2

Fertilised ovum to blastocyst

Question 3

What is the time period for the embryonic period?

What happens in this time period?

Answer 3

2nd to 8th week

Germ layers and placenta develop and main body systems form

Question 4

What is the time period of the fetal period?

What are the main events that happen in the fetal period?

Answer 4

8 weeks onwards to birth

Further growth and development of organs

Locomotor system becomes functional

Question 5

What does the inner cell mass of the blastocyst form?

Answer 5

Embryo

Question 6

What does the outer cell mass of the blastocyst become?

Answer 6

Placenta

Question 7

What week does the bilaminar disc form?

Answer 7

Week 2

Question 8

What forms the bilaminar disc?

Answer 8

Embryoblast

Question 9

What 2 layers does the embryonic disc/bilaminar disc consist of?

Answer 9

Epiblast and Hypoblast

Question 10

What is gastrulation and what week does it occur?

Answer 10

When the bilaminar embryonic disc is converted into a trilaminar embryonic disc via the formation of a primitive streak

Week 3

Question 11

What are the 3 layers of the trilaminar disc?

Answer 11

Ectoderm
Mesoderm
Endoderm

Question 12

What is derived from ectoderm?

Answer 12

CNS
Epidermis of skin and glands
Pituitary gland

Question 13

What is derived from the mesoderm?

Answer 13

Uroogential tract (Repro tract)
MSK
Blood
Heart
Kidneys
Dermis of skin

Question 14

What is derived from endoderm?

Answer 14

Epithelium lining resp, GI, repro and urinary tract

Liver
Para thyroid and thyroid
Thymus
Pancreas

Question 15

What part of the mesoderm is the urogenital tract derived from?

Answer 15

Intermediate mesoderm

Question 16

Where do primordial germ cells originate from and where do they migrate to in the developing urogential tract?

Answer 16

Originates from yolk sac (epiblast layer) and migrates to the genital ridge

Question 17

What determines the chromosomal sex of an embryo?

What is the default development?

Answer 17

Determined by what type of sperm fertilises the oocyte (sperm either X or Y)

Question 18

What occurs in the indifferent stage (initial step) of embryological development?

Answer 18

Primordial germ cells migrate along the retroperitoneum to the urogential ridge

Question 19

What are primordial germ cells? (indifferent stage)

Where do they originate from?

Answer 19

Precursors of gametes that originate in the endoderm of the yolk sac and migrate to the genital ridge

Question 20

What are the primitive sex cords?

What forms them?

Answer 20

The epithelium of the genital ridges proliferate and penetrates the intermediate mesoderm forming the primitive sex cords

Question 21

In the indifferent stag, what forms the indifferent gonad?

Answer 21

Combo of germ cells and primitive sex cords can develop into either testes or ovaries

Question 22

What chromosome determines whether thhe testes or ovary develops?

What gene is responsible for this?

Answer 22

Y chromosome

SRY gene

Question 23

What affect does presence of the SRY gene have on development?

What if its absent?

Answer 23

Means testis determining factor is made so male development occurs

Means testis determine factor is absent so by default female development occurs

Question 24

What week of development does the germ cells migrate to the urogential ridge?

Answer 24

4 weeks

Question 25

What are the 2 types of primitive sex cord that can form? Which one is for males? Which one is for females?

Answer 25

Males = medullary cords Females =primitive sex cord degenerates and doesn’t form the testis cord (forms cortical cords)

Question 26

If the SRY gene is present (male), what does this cause the medullary cords to go onto form?

Answer 26

Seminiferous tubules

Question 27

What are the 2 types of cells that make up the seminferous tubules from the medullary cord in the testes?

Answer 27

Germ cells Sertoli cells

Question 28

What is the function of the germ cells in the seminiferous tubules?

Answer 28

Become sperm cells later on (spermatogenesis)

Question 29

What is the function of the Sertoli cells in the seminferous tubules?

Answer 29

Supports spermatogenesis by providing nutrients to the germ cells They are derived from the surface epithelium of the gland

Question 30

What are the cells between the medullary cords?

Answer 30

Leydig cells

Question 31

What is the function of leydig cells?

Answer 31

Produce testosterone

Question 32

What is the tunica albiginuea?

Answer 32

Thick fibrous layer around the testes

Question 33

What happens with the primitive sex cords to form the ovary?

Answer 33

The degenerate and do not form the testis cord

Question 34

What happens to the epithelium of the gonad in the ovary?

Answer 34

Contiues to proliferate making the cortical cords which go onto surround the germ cells forming the primordial follicle

Question 35

In men what cords form in gonad differentiation? What do these cords form?

Answer 35

Medullary cords Seminferous tubules (contain germ cells and Sertoli cell, around them tubes are leydig cells) Testosterone then made

Question 36

In women what cords form in gonad differentiation? What cells are involved in this?

Answer 36

Cortical cords Granulosa cells Thecal cells

Question 37

What are the 2 possible ducts that can develop in humans?

Answer 37

Mesonephric duct (Wolffian duct) Paramesonephric duct (Mullerian duct)

Question 38

What ducts develop in men?

Answer 38

Mesonephric duct (Wolffian duct)

Question 39

What ducts develop in women?

Answer 39

Paramesonephric duct (Müllerian duct)

Question 40

What 2 things do the testis produce (when SRY gene present on Y chromosome) to support the development of the male internal genitalia (Mesonephric duct)?

Answer 40

Mullerian inhibiting hormone (MIH) Androgens

Question 41

What is the function of Mullerian Inhibiting Hormone (MIH)?

Answer 41

Suppresses the development of the Paramesonephric / Müllerian duct

Question 42

What is the function of androgens?

Answer 42

Supports the development of the Wolffian duct

Question 43

If theres no functioning testes what ducts develop and why?

Answer 43

Female ducts (Paramesonephric ducts/Müllerian ducts) No MIH made so Müllerian duct not suppressed No androgens made so Mesonephric/Wolffian duct not supported so it regresses

Question 44

What does testosterone produced by the leydig cells stimulate the Wolffian duct to form?

Answer 44

Epididymis Vas/ductus deferens Seminal vesicles Ejaculatory duct

Question 45

What does DHT/androgens stimulate the development of?

Answer 45

Forms the external genitalia Prostate Penis Scrotum Bulbourethral glands

Question 46

What does the Müllerian ducts in women give rise to?

Answer 46

Uterus Vagina Cervix Oviducts

Question 47

What structures develop when theres no testosterone?

Answer 47

Clitoris Labia majora Labia minora

Question 48

What are the 3 general stages of Paramesonephric duct development?

Answer 48

Formation/elongation Fusion Resorption

Question 49

What happens in the elongation stage of Paramesonephric duct (mullerian) development?

Answer 49

Duct elongates toward the sinovagnial bowl

Question 50

What happens in the fusion stage of Paramesonephric duct (mullerian) development?

Answer 50

Ducts fuse together and with sinovaginal bowl

Question 51

What happens in the resorption stage of Paramesonephric duct (mullerian) development?

Answer 51

The duct walls that fused together resorb and part of the sinovaginal bowl resorb

Question 52

What are the 3 key components of the external genitalia in the indifferent stage?

Answer 52

Genital tubercle Genital folds Genital swellings

Question 53

Which is the structure in the middle in the indifferent stage, the genital fold or genital swelling?

Answer 53

Genital fold is in middle Genital swelling is around the genital fold

Question 54

In the indifferent stage, where is the urogenital sinus?

Answer 54

In the centre of the genital fold

Question 55

What does the genital tubercle become: In the man? In the woman?

Answer 55

Man = glans penis Woman = clitoris

Question 56

What does the genital fold become: In the man? In the woman?

Answer 56

Man = spongy urethra/shaft of penis Woman = labium minora

Question 57

What does the genital swelling become: In the man? In the woman?

Answer 57

Man = scrotum Woman = labium majora

Question 58

What leads to the development of the external genitalia?

Answer 58

Androgen hormones (DHT dihydrotestosterone)

Question 59

Why does no fusion occur in the development of the female genitalia?

Answer 59

No testis derived androgens (DHT)

Question 60

How do the gonads descend?

Answer 60

Testis descend from posterior abdominal wall down to the scrotum Ovaries descends from the posterior abdominal wall to the pelvis

Question 61

What is the connective tissue that guides the testis and ovaries down to their location?

Answer 61

Gubernaculum

Question 62

In the female, what is the remnant of the gubernaculum called that’s left behind?

Answer 62

Round ligament

Question 63

What is Turner syndrome? Genotype? Phenotype? What reproductive ducts develop? What external genitalia develop?

Answer 63

Genotype = 45XO So are phenotypically female (external genitalia) since no testosterone or androgens made Ovaries end up degenerating (gonadal dysgenesis)

Question 64

What is Klinefelter syndrome? Genotype? Phenotype? What duct develops and why?

Answer 64

47XXY Phenotypically male (male external genitalia) But lack of secondary characteristics like pubic and axillary hair and small testis (hypogonadism) Mesonephric/Wolffian duct since MIH and androgens made

Question 65

What duct system develops in an individual with the karyotype 46XX with Congenital Adrenal Hyperplasia? What would the external genitalia be?

Answer 65

Lots of androgens made so external genitalia looks more male since more fusion happens Paramesonephric duct (Müllerian duct) develops since theres no Y chromosome so no MIH produced

Question 66

What ducts develop with a girl that has the genotype 46XY with complete androgen insensitivity syndrome?

Answer 66

Testis develop since Y chromosome present MIH made so Paramesonephric duct not made But they are insensitive to androgens so the mesonephric ducts dont develop either so no ducts develop

Question 67

What tissue do the gonads develop from?

Answer 67

Intermediate mesoderm in abdomen