Embryology

Question 1

What are the structures that make up the male internal genitalia?

Answer 1

TestisDuct system- Epididymis- Ductus deferens/ vas deferens- UrethraSeminal vesiclesProstate glandBulbo-urethral glands

Question 2

What are the structures that make up the male external genitalia?

Answer 2

Penis and Scrotum

Question 3

What are the structures that make up the female internal genitalia?

Answer 3

OvariesDuct system- Fallopian tubes- Uterus- Cervix - Upper Part of the Vagina

Question 4

What are the structures that make up the female external genitalia?

Answer 4

ClitorisLabia minoraLabia majoraVagina Vestibule

Question 5

What are the male secondary sexual characteristics?

Answer 5

Increased body size compared to femalesCoarser skin and hair Different body composition and fat distributionFacial hair and male pattern baldnessCentral nervous effectsSmell

Question 6

What are the female secondary sexual characteristics?

Answer 6

Decreased body size in comparison to malesSubcutaneous fat distributionHair Breast developmentCentral nervous effects

Question 7

How is the development of the reproducive system similar initially?

Answer 7

Development gives rise to an indeifferent stage, producing a gonad and duct system which are idnetical. From here, hormones regulate the development into one of the two sexes.

Question 8

What are the difference between structural and functional development?

Answer 8

Structural development occurs in utero whilst functional development and maturity occurs after birth at puberty, along with the development of the secondary sexual characteristics.

Question 9

What is the gonad derived from?

Answer 9

The urogenital ridge which is a part of the intermediate mesoderm

Question 10

What are primordial germ cells?

Answer 10

Cell which arise from an area near the allantois, which will migrate from the wall of the yolk sac, into the developing body of the embryo.

Question 11

How do primordial germ cells move?

Answer 11

Start near the allantois, move retroperitoneally along the dorsal mesentery into the urogenital ridge and therefore the gonad. These will form the gametes for the next generation.

Question 12

What gene is always expressed in males?

Answer 12

SRY gene– sex-determining region Y

Question 13

What part of the gonad does the male genitalia develop from?

Answer 13

From the medulla

Question 14

What does the medulla develop into in the male?

Answer 14

Horseshoe shaped testis cords (future seminiferous tubules) and a thick tunica albuginea.

Question 15

What does the gonad develop into in females?

Answer 15

The gonad will then develop into an ovary and the duct system will form the fallopian tubes and the uterus and also the female external genitalia.

Question 16

What part of the gonad do the ovaries develop from?

Answer 16

The cortex

Question 17

What if the fate of the mesonephric ducts in males?

Answer 17

1. Mesonephric ducts reach the urogenital sinus2. Ureteric buds develop from the mesonephric ducts and smooth musculature being to appear in the wall of the urogenital sinus which also begins to expand3. Both the ureteric buds and mesonephric ducts form separate openings in the urogenital sinus and the mesonephric ducts sat open due to the influence of male hormones as they will form the duct system of the male reproductive tract. 4. The prostate and prostatic urethra are formed again under the influence of male hormones from the Wolffian/mesonephric ducts.

Question 18

Why do the mesonephric ducts stay open in males?

Answer 18

They give rise to the duct system (seminal vesicles, vas deferens, epididymis) and testosterone produced by the testes mean that they will remain open.

Question 19

What is the fate of the mesonephric dicts in females?

Answer 19

1. Mesonephric ducts reach the urogenital sinus (gives rise to bladder and the urethra)2. Ureteric buds develop from the mesonephric ducts and smooth musculature being to appear in the wall of the urogenital sinus which also begins to expand3. The mesonephric ducts begin to regress, because they are not needed as a part of the urinary system and the male sex hormones (androgens) are not present, so they regress. 4. The ureteric buds open into the urogenital sinus and the bladder and ureters continue to develop.

Question 20

Why do the paramesonephric ducts have that name?

Answer 20

Are found close to the mesonephric ducts

Question 21

What do the paramesonephric ducts give rise to?

Answer 21

The fallopian tubes, uterus, cervix and upper part of the vagina in women and they will regress in males.

Question 22

Describe the paramesonephric ducts

Answer 22

They appear as invaginations of the epithelium of the urogenital ridge, which then go on to make a tube. Caudally, they make contact with the cloaca and cranially there open into the abdominal cavity. They will grow in the absence of supporting molecules, therefore will grow in both the male and the female.

Question 23

Describe how the paramesonephric ducts develop

Answer 23

The ducts develop towards each other and they fuse together from each side of the posterior abdominal wall. They form a uterine septum, forming two chambers as such. The septum then degenerates and the UGS expands to form the vagina and fornices which are found around the cervix.

Question 24

What is the starting point for the development of the external genitalia in both men and women?

Answer 24

They both start at the indifferent stage, which is comprised of:1. Genital tubercle2. Genital folds3. Genital swellings

Question 25

Describe the development of the male external genitalia

Answer 25

The gentile tubercle elongates and the genital folds fuse to form the spongy urethra. The genital swellings fuse to form the scrotum. Both processes are determined by the dihydrotestosterone which is an androgen produced from the testes.

Question 26

Describe the development of the female external genitalia

Answer 26

Absence of fusion due to absence of dihydrotestosterone gives rise to the female external genitalia. This causes the urethra to open into the vestibule. The genital tubercle become the clitoris, the genital swelling becomes the labia majora and the genital folds become the labia minora.

Question 27

Where do the gonads develop initially?

Answer 27

High up on the posterior abdominal wall

Question 28

What is connected to both the ovaries and the testes/

Answer 28

The gubernaculum- is a ligament which connect the gonads to the genital swelling

Question 29

Describe the descent of the testes

Answer 29

The gubernaculum connect the inferior pole of the testis to the genital swelling. As the trunk of the embryo elongates, the testes is pulled down behind the peritoneum, out of the anterior abdominal wall via the deep inguinal ring, inguinal canal and superficial inguinal ring. After this, it passes behind the processus vaginalis. As it moves down, it brings its duct system down with it.

Question 30

What does the gubernaculum become in the adult male?

Answer 30

The spermatic cord

Question 31

Describe the descent of the ovaries

Answer 31

The gubernaculum attaches the inferior portion of the ovary to the labio-scrotal folds. In contrast, the ovary only descends to the pelvis as the newly formed uterus forms a barrier to the further descent.

Question 32

What does the gubernaculum become in the adult female?

Answer 32

The gubernaculum degenerates to the round ligament of the uterus which is seen in the inguinal canal and the ovarian ligament.

Question 33

What structures do the Mullerian ducts develop into in the female?

Answer 33

F - Fallopian tubesU - UterusC - CervixU - Upper part of the vagina

Question 34

What structures do the Wolffian ducts develop into in the male?

Answer 34

S - Seminal vesicaleE - EpididymisV - Vas deferens/ductus deferens

Question 35

What hormones are produced in the male to influence development?

Answer 35

Testosterone which is metabolised to dihydrotestosterone, which stimulates testes and male duct system formation. Also, Mullerian Inhibiting Substance which is secreted from the testes will cause the Mullerian ducts to regress in the male.

Question 36

What does the genital tubercle become in the male?

Answer 36

Spongy urethra/penis

Question 37

What does the genital tubercle become in the female?

Answer 37

Clitoris

Question 38

What does the genital fold become in the male?

Answer 38

Spongy urethra/penis

Question 39

What does the genital fold become in the female?

Answer 39

Labia minora

Question 40

What does the genital swelling become in the male?

Answer 40

Scrotum

Question 41

What does the genital swelling become in the female?

Answer 41

Labia majora

Question 42

What does the urogenital sinus become in the male?

Answer 42

Prostate

Question 43

What does the urogenital sinus become in the female?

Answer 43

Vagina