Hy Embryology 09

Front 1

When is the genotype of an embryo established?

Back 1

At fertilization

Front 2

Describe sexual development of the embryo during weeks 1-6

Back 2

The embryo remains in a sexually indifferent or undifferentiated stage. This means that genetically female embryos and genetically male embryos are phenotypically indistinguishable

Front 3

Describe sexual development of the embryo during week 7

Back 3

The indifferent embryo begins phenotypic sexual differentiation

Front 4

Describe sexual development of the embryo by week 12

Back 4

Female or male characteristics of the external genitalia can be recognized

Front 5

Describe sexual development of the embryo by wee 20

Back 5

Phenotypic differentiation is complete

Front 6

What gene determines phenotypic sexual differentiation?

Back 6

Sry gene

Front 7

Describe the Sry gene

Back 7

1. Phenotypic sexual differentiation is determined by the Sry gene located on the short arm of the Y chromosome and result in individuals with a female phenotype, an intersex phenotype, or a male phenotype

2. The Sry gene encodes for a protein called testes-determining factor (TDF)

Front 8

Where is the Sry gene located?

Back 8

The short arm of the Y chromosome

Front 9

What protein does the Sry gene encode for?

Back 9

Testes-determining factor (TDF)

Front 10

What gene encodes for the testes-determining factor?

Back 10

Sry

Front 11

Describe the development of testes

Back 11

As the indifferent gonad develops into the testes, Leydig cells and Sertoli cells differentiate to produce testosterone and Mullerian inhibiting factor, respectively

Front 12

What testicular cells produce testosterone?

Back 12

Leydig cells

Front 13

What testicular cells produce Mullerian inhibiting factor?

Back 13

Sertoli cells

Front 14

What is the effect of testes-determining factor (TDF) on the indifferent embryo?

Back 14

1. In the presence of TDF, testosterone, and MID, the indifferent embryo will be directed to the male phenotype

2. In the absence of TDF, testosterone, and MIF, the indifferent embryo will be directed to the female phenotype

Front 15

Describe the development of the intermediate mesoderm

Back 15

The intermediate mesoderm forms a longitudinal elevation along the dorsal body wall called the urogenital ridge, which later forms the gonadal ridge

Front 16

Describe the development of the gonadal ridge

Back 16

The intermediate mesoderm forms a longitudinal elevation along the dorsal body wall called the urogenital ridge, which later forms the gonadal ridge

Front 17

Describe the development of primary sex cords

Back 17

1. Primary sex cords develop from the gonadal ridge and incorporate primordial germ cells (XX genotype), which migrate into the gonad from the wall of the yolk sac

2. Primary sex cords extend into the medulla and develop into the rete ovarii, which eventually degenerates

Front 18

Describe the development of secondary sex cords

Back 18

1. Secondary sex cords develop and incorporate primordial germ cells as a thing tunica albuginia forms

2. Secondary sex cords break apart and form isolated cell clusters called primordial follicles, which contain primary oocytes surrounded by a layer of simple squamous cells

Front 19

Describe the relative descent of the ovaries

Back 19

1. The ovaries originally develop within the abdomen but later undergo a relative descent into the pelvis as a result of disproportionate growth

2. The gubernaculum may also play a role. The gubernaculum is a band of fibrous tissue along the posterior wall that extends from the medial pole of the ovary to the uterus at the junction of the uterine tubes, forming the ovarian ligament.

3. The gubernaculum then continues into the labia majora, forming the round ligament of the uterus

Front 20

Describe the gubernaculum

Back 20

1. The gubernaculum may also play a role. The gubernaculum is a band of fibrous tissue along the posterior wall that extends from the medial pole of the ovary to the uterus at the junction of the uterine tubes, forming the ovarian ligament.

2. The gubernaculum then continues into the labia majora, forming the round ligament of the uterus

Front 21

What structure forms the round ligament of the uterus?

Back 21

The gubernaculum

Front 22

What structure forms the ovarian ligament?

Back 22

The gubernaculum

Front 23

Describe the development of the paramesonephric (Mullerian) ducts

Back 23

1. The cranial portions of the paramesonephric ducts develop into the uterine tubes

2. The caudal portions of the paramesonephric ducts fuse in the midline to form the uterovaginal primordium and thereby bring together two peritoneal folds called the broad ligament

3. The uterovaginal primordium develops into the uterus, cervix, and superior one third of the vagina

4. The paramesonephric ducts project into the dorsal wall of the cloaca and induce the formation of the sinovaginal bulbs. The sinovaginal bulbs fuse to form the solid vaginal plate, which canalizes and develops into the inferior two thirds of the vagina

5. Vestigial remnants of the paramesonephric duct may be found in the adult female and are called the hydatid of Morgagni

Front 24

Describe the development of the uterine tubes

Back 24

Develop from the cranial portions of the paramesonephric duct

Front 25

What develops from the cranial portion of the mesonephric duct?

Back 25

The uterine tubes

Front 26

Describe the development of the broad ligament

Back 26

The caudal portions of the paramesonephric ducts fuse in the midline to form the uterovaginal primordium and thereby bring together two peritoneal folds called the broad ligament

Front 27

What develops from the caudal portion of the mesonephric duct?

Back 27

The caudal portions of the paramesonephric ducts fuse in the midline to form the uterovaginal primordium and thereby bring together two peritoneal folds called the broad ligament

Front 28

Describe the development of the uterus

Back 28

The uterovaginal primordium develops into the uterus, cervix, and superior one third of the vagina

Front 29

Describe the development of the cervix

Back 29

The uterovaginal primordium develops into the uterus, cervix, and superior one third of the vagina

Front 30

Describe the development of the superior one third of the vagina

Back 30

The uterovaginal primordium develops into the uterus, cervix, and superior one third of the vagina

Front 31

What develops from the uterovaginal primordium?

Back 31

The uterovaginal primordium develops into the uterus, cervix, and superior one third of the vagina

Front 32

Describe the development of the sinovaginal bulbs

Back 32

The paramesonephric ducts project into the dorsal wall of the cloaca and induce the formation of the sinovaginal bulbs

Front 33

Describe the sinovaginal bulbs

Back 33

1. The paramesonephric ducts project into the dorsal wall of the cloaca and induce the formation of the sinovaginal bulbs

2. The sinovaginal bulbs fuse to form the solid vaginal plate, which canalizes and develops into the inferior two thirds of the vagina

Front 34

Describe the development of the inferior two thirds of the vagina

Back 34

The sinovaginal bulbs fuse to form the solid vaginal plate, which canalizes and develops into the inferior two thirds of the vagina

Front 35

Describe the hydatid of Morgagni

Back 35

The vestigial remnants of the paramesonephric duct may be found in the adult female and are called the hydatid of Morgagni