6.1 Embryonic Development of GONADS

Question 1

UROGENITAL SYSTEM develops from the..

Answer 1

INTERMEDIATE MESODERM

Question 2

GONADAL DIFFERENTIATION is determined by..

Answer 2

the SEX DETERMINING REGION of Y CHROMOSOME (SRY)

/ PRESENCE/ABSENCE of TESTIS DETERMINING REGION

Question 3

consequence of presence or absence of Y CHROMOSOME

Answer 3

XY: TESTES form

XX (no Y): OVARIES form

Question 4

presence of Y CHROMOSOME means presence of TESTES which produce which hormones

Answer 4

TESTOSTERONE and ANTIMULLERIAN HORMONE

• determine the internal and external ANATOMY and GONADAL DESCENT

Testosterone absence or presence can have an effect on the way the BRAIN develops

Question 5

when do GONADS start to APPEAR and when do they start to DIFFERENTIATE

Answer 5

5 WEEKS
differentiate at 6 WEEKS

Question 6

3 ORIGINS of GONADS

Answer 6

• MESOTHELIUM (mesodermal epithelium)
  lining the posterior abdominal wall / coelom
• UNDERLYING MESENCHYME (embryonic connective tissue)
  middle layer
• PRIMORDIAL GERM CELLS
  (earliest undifferentiated sex cells that will become oocytes and sperm)

Question 7

what migrate into the GONADS from the YOLK SAC

Answer 7

PRIMORDIAL GERM CELLS

Question 8

what forms the CORTEX

Answer 8

LINING of the COELOM

Question 9

what forms of central part / MEDULLA

Answer 9

MESENCYHME (medial mesonephros) projecting into the COELOM as a ridge

Question 10

MESOTHELIUM projects into the MESENCHYME and forms

Answer 10

finger-like projections

Question 11

GONADAL RIDGE becomes
(6 weeks)

Answer 11

OVARIES / TESTES

Question 12

GERM CELLS become
(6 weeks)

Answer 12

SPERMATOCYTES / OOCYTES

Question 13

PATHWAY from INDIFFERENT GONAD (with Cortex and Medulla) when Y CHROMOSOME is present

Answer 13

increase TESTICULAR DETERMINING FACTOR

stimulates DEVELOPMENT of MEDULLA (regression of Cortex)

SERTOLI CELLS and LEYDIG CELLS produced

SERTOLI cells secrete ANTIMULLERIAN HORMONE (AMH)
- SUPPRESSES FORMATION of MULLERIAN DUCTS

LEYDIG cells secrete TESTOSTERONE
- supports development of WOLFIAN DUCTS, EPIDYMIS, VAS DEFERENS, SEMINAL VESICLE, EJACULATORY DUCT

& PROTATE, BULBOURETHRAL GLANDS, PENIS, SCROTUM, BRAIN is MASCULANISED

Question 14

presence of Y CHROMOSOME INCREASES what

Answer 14

TDF
- TESTICULAR DETERMINING FACTOR

Question 15

result of TDF INCREASE

Answer 15

DEVELOPMENT of MEDULLA

CORTEX REGRESSES

Question 16

result of MEDULLA DEVELOPMENT in GONADS

Answer 16

LEYDIG and SARTOLI CELLS produced

Question 17

SARTOLI CELLS produce what HORMONE and what does it do

Answer 17

AMH
ANTIMULLERIAN HORMONE

• SUPPRESSES DEVELOPMENT of MULLERIAN DUCTS (female)

Question 18

LEYDIG CELLS produce what HORMONE

Answer 18

TESTOSTERONE

Question 19

EFFECT of TDF of PRIMORDIAL GERM CELLS

Answer 19

DIFFERENTIATE into SPERMATOGONIA

(-> SPERMATOZOA at puberty)

Question 20

2 effects of TDF (TESTICULAR DETERMINING FACTOR)

Answer 20

• MEDULLA DEVELOPMENT
• primordial germ cells become SPERMATOGONIA which become SPERMATOZOA

Question 21

PATHWAY of INDIFFERENT GONADS with NO Y CHROMOSOME (female)

Answer 21

NO TDF

CORTEX DEVELOPS
Medulla regresses

production of THECA and GRANULOSA CELLS

ABSENCE of TESTOSTERONE

Internal: OVIDUCTS, UTERUS, CERVIX, VAGINA (part)
External: CLITORIS, LABIA M
AJORA, LABIA MINORA, BRAIN NOT MASCULANISED

also NO TDF on PRIMORDAL GERM CELLS
-> OOGONIA
-> OOCYTES

Question 22

EFFECT of NO TDF on PRIMORDIAL GERM CELLS

Answer 22

DIFFERENTIATE to become OOGONIA which become OOCYTES

Question 23

finger-like PROJECTIONS of the EPITHELIUM (/ of the cortex into the medulla) are known as the

Answer 23

SEX CORDS

Question 24

TESTES DEVELOPMENT
what do the SEX CORDS become

Answer 24

SEMINIFEROUS CORDS
(lose their connection with surface epithelium)

develop into SEMINIFEROUS TUBULES, RETE TESTIS and TUBILI RECTI

Question 25

TESTES DEVELOPMENT what are the WALLS of the SEMINIFEROUS TUBULES composed of

Answer 25

- SPERMATOGONIA (primordial sperm cells derived from primordial germ cells) - SERTOLI CELLS (MOST of the seminiferous epithelium in the foetal testis)

Question 26

TESTES DEVELOPMENT SEMINIFEROUS TUBULES remain SOLID until..

Answer 26

they DEVELOP a LUMEN at PUBERTY

Question 27

TESTES DEVELOPMENT WHEN do the LEYDIG CELLS (BETWEEN SEMINIFEROUS TUBULES) secrete TESTOSTERONE (masculine differentiation)

Answer 27

WEEK 8

Question 28

TESTES DEVELOPMENT what is TESTOSTERONE PRODUCTION STIMULATED by

Answer 28

HUMAN CHORIONIC GONADOTROPIN

Question 29

TESTES DEVELOPMENT when does TESTOSTERONE PRODUCTION stimulated by HUMAN CHORIONIC GONADOTROPIN PEAK

Answer 29

8TH-12TH WEEK

Question 30

TESTES DEVELOPMENT SERTOLI CELLS produce AMH until..

Answer 30

PUBERTY

Question 31

when do OVARIES START to DIFFERENTIATE

Answer 31

12 WEEKS

Question 32

OVARY DEVELOPMENT what do PRIMORIAL GERM CELLS become and what do these consist of

Answer 32

PRIMORDIAL FOLLICLES consisting of OOGONIA (derived from primordial germ cells)

Question 33

OVARY DEVELOPMENT PRIMORDIAL FOLLICLES are surrounded by a LAYER of..

Answer 33

FOLLICULAR CELLS derived from the SURFACE EPITHELIUM

Question 34

OVARY DEVELOPMENT thick CORDS that extend from the epithelium are known as... and what do they do

Answer 34

CORTICAL CORDS PUSH INTO the UNDERLYING MESENCHYME meet PRIMORDIAL GERM CELLS -> break up into Clusters : PRIMORDIAL FOLLICLES

Question 35

OVARY DEVELOPMENT PRIMARY/PRIMORDIAL FOLLICLES are made up of

Answer 35

OOGONIA and FOLLICULAR CELLS (derived from cortical cords/surface epithelium)

Question 36

OVARY DEVELOPMENT when do OOGONIA stop forming (mitosis)

Answer 36

from BIRTH

Question 37

TESTES DESCENT is brought about by the

Answer 37

SHORTENING of the GUBERNACULUM (connects testes to scrotum) as the foetus grows

Question 38

When does DESCENT of TESTIS, epididymis and gubernaculum start

Answer 38

WEEK 23

Question 39

at what point in Gestation do the TESTES PASS OUT through the anterior abdominal wall

Answer 39

23-30 WEEKS

Question 40

as TESTES pass OUTSIDE what FORMS

Answer 40

INGUINAL CANAL

Question 41

when are the TESTES in their FINAL POSITION in SCROTUM

Answer 41

between 28-32 WEEKS

Question 42

In the presence of TDF/SRY which gene is switched ON

Answer 42

SOX9 on chromosome 17

Question 43

Which gene is ACTIVATED when XX but silenced when XY

Answer 43

WNT4