Development of Male and Female

Question 1

What are the three layers of the embryo?

Answer 1

• endoderm
• mesoderm
• ectoderm

Question 2

Which organs/systems develop from the ectoderm?

Answer 2

• vagina and vestibule
• penis and clitoris
• mammary glands
• nervous system

Question 3

Which organs/systems develop from the mesoderm?

Answer 3

• gonads
• uterus, cervix, cranial vagina
• epididymis, ductus deferens
• accessory sex glands

Question 4

What are the three fetal membranes?

Answer 4

• amnion (inner)
• allantois
• chorion (outer)

Question 5

Which is the first organ to develop?

Answer 5

brain

- then heart and liver

Question 6

What is Schistomus reflexus? What are the morphologic problems?

Answer 6

• fatal congenital disorder
• spinal inversion
• exposure of abdominal viscera due to fissure of the ventral abdominal wall
• limb ankylosis
• positioning of the limbs adjacent to the skull
• lung and diaphragm hypoplasia

Question 7

What events occur in the 1st trimester?

Answer 7

• migration of primordial germ cells from yolk sac

- sex cords develop in gonad, paramesonephric ducts develop

Question 8

In what trimester does formation of the broad ligament occur?

Answer 8

2nd

Question 9

In what trimester does testicular descent occur?

Answer 9

2nd - bull and ram

3rd - boar and colt

Question 10

When is development of the ducts and testes/ovaries?

Answer 10

between 1st and 2nd trimesters

Question 11

What is karyotype?

Answer 11

the chromosomal complement of an organism

- number of chromosomes followed by XX or XY

Question 12

What is genotype?

Answer 12

the allele genetic constitution of an individual

Question 13

What is phenotype?

Answer 13

observed characteristics of an individual

- morphology, development, blood type, and behavior

Question 14

What is a chimera?

Answer 14

• single organism composed of genetically distinct cells

- produced by fusion of two different zygotes in a single embryo

Question 15

What is a mosaic?

Answer 15

an individual with two different cell lines that originated from that same individual

Question 16

How is chromosomal sex determined?

Answer 16

determined at fertilization by the type of sex chromosome contributed by the sperm

Question 17

How is gonadal sex determined?

Answer 17

determined by “sex determining region” of the Y chromosome

- SRY gene

Question 18

How is phenotypic sex determined?

Answer 18

determined by substances produced in male testes to cause regression of female tract and formation of male tract

Question 19

What is the mesonephros, and what happens to it in the male and female?

Answer 19

• intermediate kidney
• forms efferent ducts in the male
• regresses in the female

Question 20

What happens to the mesonephric/Wolffian ducts in the male and female?

Answer 20

• forms epididymis and ductus deferen in the male

- regresses in the female

Question 21

What happens to the paramesonephrics/Mullerian ducts in the male and female?

Answer 21

• regresses in the male

- forms uterus oviducts, and cranial vagina in the female

Question 22

What is formed by the primitive sex cords in the male and female?

Answer 22

• forms seminferous tubules in the male

- regresses and forms primitive follicular cells in the female

Question 23

Describe the determination of physical sex organ characteristics in a male

Answer 23

• testis determining factor (TDF) and SRY genes on the Y chromosome cause development of testes and testosterone
• anti-mullerian hormone causes degeneration of paramesonephric ducts and causes leydig cells to differentiate
• dihydrotestosterone causes development of penis, scrotum, and accessory sex glands