Development of the Genital System | B2, WK5

Question 1

Which develops first: External or internal genitals?

Answer 1

Internal (External takes longer)

Question 2

The urinary and genital systems are derived from _______________________-

Answer 2

intermediate mesoderm (intermediate mesenchyme)

Question 3

Intermediate mesoderm forms a _______________ ________________ (2 words), which differentiates into what 2 structures?

Answer 3

Urogenital ridge
1. nephrogenic cord
2. genital ridge

Question 4

T/F: Up until week 6, the genital system develops differently for Male/Female, regardless of chromosomal composition of the embryo

Answer 4

False
Up until week 6, the genital system develops similar for Male/Female, regardless of chromosomal composition of the embryo

Question 5

What is genotypic sex?

Answer 5

Sex of individual based on chromosomes
46 XX, 46 XY
[don’t forget about 45X (turner syndrome) and 47 XXY [Klinfelter syndrome]

Question 6

What is phenotypic sex?

Answer 6

Based on the appearance of internal/external genitalia (i.e., phenotype = physical)

Question 7

How is phenotypic sex first determined? (list/describe the process)

Answer 7

Y chromosomes have SRY genes. These genes produce SRY protein (or testis determining factor)
1. SRY protein produced in developing gonad
2. SRY protein starts cascade of factors that initiate male-like phenotypic sex development

Question 8

What happens (in terms of phenotypic sex) when an embryo has XX chromosomal pattern OR the Y chromosome does not contain the SRY gene

Answer 8

Female-like phenotypic sex will be produced

Question 9

Genital (gonadal) ridges form _____________ to mesonephros and are initially at level of _______ vert.

Answer 9

Medial
T10

Question 10

During the 5th-6th week, what cells migrate from the yolk sac to the genital ridges? What happens if these cells don’t migrate?

Answer 10

Primordial germ cells [oocytes/sperm]
If they don’t migrate - gonads will NOT form

Question 11

What is the outer part of the gonad? inner part?

Answer 11

Outter: cortex
Inner: medulla

Question 12

The ____________________________ (3 words) are found in the medulla of developing gonad.

Answer 12

Primitive (primary) sex cords

Question 13

By the 6th week - What two duct systems form?

Answer 13

1. Mesonephric (wolffian) ducts
2. Paramesonephric

Question 14

What are Mesonephric (wolffian) ducts?

Answer 14

Form most of the phenotypic-male duct system

Question 15

What are Paramesonephric (Mullerian) ducts?

Answer 15

Form most of the phenotypic female duct system

Question 16

SRY protein starts its work at week 7 - what does this do/mean?

Answer 16

Differentiation of genitalia during Wk 7 – SRY protein influences the gonad to become a testis

Question 17

Under influence of SRY protein, medullary portions of _______________________ develop

Answer 17

Primitive sex cords (testis cords)

Question 18

What does the testis cord form?

Answer 18

Seminiferous tubules & rete testis

Question 19

What do sustentacular (sertoli) cells secrete?

Answer 19

Anti-mullerian hormone (AMH) [or Mullerian Inhibiting Substance (MIS)]

Question 20

What does AMH (MIS) induce?

Answer 20

degeneration of paramesonephric ducts

Question 21

The paramesonephric ducts degenerate, but what about the mesonephric duct?

Answer 21

This duct remains, will form most of the reproductive duct system associated w/ the testis

Question 22

How does the prostate and bulbourethral glands form?

Answer 22

Form from endodermal ‘buds’ off of urethra

Question 23

What pulls the testis down from its lumbar placement into the scrotum?

Answer 23

Gubernaculum!

Question 24

3rd - 7th month of development - where are the testes located?

Answer 24

Testis at level of deep inguinal ring

Question 25

9th month of development - where are the testes located?

Answer 25

Testis pulled into scrotum

Question 26

What gets "pulled" with the testis as it descends?

Answer 26

Its innervation (T10/T11)

Question 27

The kidneys _________________ while the testes start to ________________.

Answer 27

Kidneys: ascend Testes: descend

Question 28

T/F: The descent of the testes occurs throughout entire fetal period

Answer 28

TRUE

Question 29

What is cryptorchidism?

Answer 29

"Hidden testis" -Undescended testis

Question 30

Why does cryptorchidism occur more commonly in preemies?

Answer 30

Born before 9th month, so it has not descended yet

Question 31

What other increased risks are associated with cryptochidism?

Answer 31

Testicular cancer Fertility problems (b/c of temp regulation that is needed)

Question 32

What is testicular Hydrocele?

Answer 32

Fluid-build up in either tunica vaginalis or part of patent process vaginalis

Question 33

T/F: Testicular hydrocele typically occurs in 3-5 yr olds and needs medical attention, as it will not regress on its own

Answer 33

FALSE: typically occurs in 1 yr olds AND typically regresses on its own (emphasis on typically)

Question 34

Absence of the Y-chromosome and SRY gene will yield

Answer 34

Female-like development

Question 35

During the 7th week, the testis cords of gonads degenerate and a secondary set of cords called ______________________ develop in the __________________ [differentiation of ovaries]

Answer 35

cortical cords ; cortex

Question 36

Cortical cords form what?

Answer 36

Follicular cells of ovarian follice

Question 37

Does the medulla of the ovary have sex cells? {Think about gross anatomy and histo}

Answer 37

NO

Question 38

In female development, absence of AMH yields

Answer 38

-degeneration of mesonephric ducts -development of paramesonephric ducts

Question 39

What forms the uterus and superior part of the vagina?

Answer 39

Inferior (caudal) ends of paramesonephric ducts that fuse (during 2nd trimester)

Question 40

What forms the uterine tubes?

Answer 40

Unfused superior forms of paramesonephric ducts

Question 41

The inferior part of the vagina is formed from?

Answer 41

Sinovaginal bulbs (off of UG sinus) that fuse -- OUTGROWTH of urethra

Question 42

The vagina separates from the bladder when?

Answer 42

When the inferior part of the vagina forms

Question 43

Where do the ovaries descend from?

Answer 43

T10 region --> to pelvic cavity (posterior to broad ligament)

Question 44

What are uterine malformations typically caused by?

Answer 44

Partial atresia of one of the paramesonephric ducts (atresia: a body part that is tubular in nature does not have a normal opening, or lacks the ability to allow material to pass through it.)

Question 45

What is uterus didelphys?

Answer 45

Double uterus & double cervix -- fundus malformation

Question 46

What does this pic show?

Answer 46

Bicornuate Uterus

Question 47

Why are uterine malformations (such as uterus didelphys) harmful?

Answer 47

Causes issues for the development of offspring (i.e., uterus can't expand as fetus grows)

Question 48

What occurs when sinovaginal bulbs fail to form?

Answer 48

Vaginal Atresia

Question 49

Vaginal atresia is when...

Answer 49

The superior vagina forms but the inferior part does not (so, no connection to the outside body)

Question 50

External genitalia are undifferentiated until about week ____. They are phenotypically differentiated by about week _____.

Answer 50

12 20

Question 51

What are the three sets of primordia (external genitalia) found at week 6?

Answer 51

1. Urethral (urogenital folds) 2. Labioscrotal swellings 3. Gentical tubercle (phallus)

Question 52

Under the influence of testosterone - what happens to the following? -Genital tubercle -Urethral folds -Labioscrotal folds

Answer 52

-Genital tubercle: enlarges, forms the glans of penis -Urethral folds: fuse to form the ventral surface of the penis (encloses penile urethra) -Labioscrotal folds: fuse to form the scrotum

Question 53

In the absence of testosterone (or lack of tissue response to testosterone), the embryonic folds remain

Answer 53

Unfused

Question 54

Under NO influence of testosterone - what happens to the following? -Genital tubercle -Urethral folds -Labioscrotal folds

Answer 54

-Genital tubercle: becomes clitoris -Urethral folds: becomes labia minora -Labioscrotal folds: labia majora

Question 55

What is hypospadias?

Answer 55

Disorder where irethra found on inferior (ventral) surface of penis instead of glands

Question 56

What causes hypospadias?

Answer 56

Incomplete fusion of urethral folds

Question 57

What is epispadias?

Answer 57

Disorder when urethral opening is on the DORSUM of penis

Question 58

What is epispadias usually associated with?

Answer 58

Bladder exstrophy (Ventral body defect - bladder inside out, sticks out of abdominal wall)

Question 59

What is 46 XY DSD?

Answer 59

XY genotype w/ ambiguous external genitalia or variable phenotypic female-like external genitalia Testicular tissue may be present

Question 60

What usually causes 46 XY DSD?

Answer 60

A reduction in male hormones in development OR Tissues don't respond to androgens (insensitivity)

Question 61

What is 46 XX DSD?

Answer 61

XX genotype Ambiguous or phenotypic male-like external genitalia

Question 62

What are the phenotypic characteristics of 46 XX DSD?

Answer 62

Clitoris may be enlarged Labia may be partially or completely fused

Question 63

What is 46 XX DSD due to exposure of XX fetus to excessive androgens?

Answer 63

-Occurs when pregnant individuals produce or are exposed to abnormal amounts of androgens

Question 64

What is Conginital adrenal hyperplasia (CAH)?

Answer 64

Fetal adrenal gland produces EXCESSIVE amounts of androgens (most common cause of 46 XX intersex)