6.1 Embryonic Development of GONADS Flashcards
UROGENITAL SYSTEM develops from the..
INTERMEDIATE MESODERM
GONADAL DIFFERENTIATION is determined by..
the SEX DETERMINING REGION of Y CHROMOSOME (SRY)
/ PRESENCE/ABSENCE of TESTIS DETERMINING REGION
consequence of presence or absence of Y CHROMOSOME
XY: TESTES form
XX (no Y): OVARIES form
presence of Y CHROMOSOME means presence of TESTES which produce which hormones
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
when do GONADS start to APPEAR and when do they start to DIFFERENTIATE
5 WEEKS
differentiate at 6 WEEKS
3 ORIGINS of GONADS
- 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)
what migrate into the GONADS from the YOLK SAC
PRIMORDIAL GERM CELLS
what forms the CORTEX
LINING of the COELOM
what forms of central part / MEDULLA
MESENCYHME (medial mesonephros) projecting into the COELOM as a ridge
MESOTHELIUM projects into the MESENCHYME and forms
finger-like projections
GONADAL RIDGE becomes
(6 weeks)
OVARIES / TESTES
GERM CELLS become
(6 weeks)
SPERMATOCYTES / OOCYTES
PATHWAY from INDIFFERENT GONAD (with Cortex and Medulla) when Y CHROMOSOME is present
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
presence of Y CHROMOSOME INCREASES what
TDF
- TESTICULAR DETERMINING FACTOR
result of TDF INCREASE
DEVELOPMENT of MEDULLA
CORTEX REGRESSES
result of MEDULLA DEVELOPMENT in GONADS
LEYDIG and SARTOLI CELLS produced
SARTOLI CELLS produce what HORMONE and what does it do
AMH
ANTIMULLERIAN HORMONE
- SUPPRESSES DEVELOPMENT of MULLERIAN DUCTS (female)
LEYDIG CELLS produce what HORMONE
TESTOSTERONE
EFFECT of TDF of PRIMORDIAL GERM CELLS
DIFFERENTIATE into SPERMATOGONIA
(-> SPERMATOZOA at puberty)
2 effects of TDF (TESTICULAR DETERMINING FACTOR)
- MEDULLA DEVELOPMENT
- primordial germ cells become SPERMATOGONIA which become SPERMATOZOA
PATHWAY of INDIFFERENT GONADS with NO Y CHROMOSOME (female)
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
EFFECT of NO TDF on PRIMORDIAL GERM CELLS
DIFFERENTIATE to become OOGONIA which become OOCYTES
finger-like PROJECTIONS of the EPITHELIUM (/ of the cortex into the medulla) are known as the
SEX CORDS
TESTES DEVELOPMENT
what do the SEX CORDS become
SEMINIFEROUS CORDS
(lose their connection with surface epithelium)
develop into SEMINIFEROUS TUBULES, RETE TESTIS and TUBILI RECTI
TESTES DEVELOPMENT
what are the WALLS of the SEMINIFEROUS TUBULES composed of
- SPERMATOGONIA (primordial sperm cells derived from primordial germ cells)
- SERTOLI CELLS (MOST of the seminiferous epithelium in the foetal testis)
TESTES DEVELOPMENT
SEMINIFEROUS TUBULES remain SOLID until..
they DEVELOP a LUMEN at PUBERTY
TESTES DEVELOPMENT
WHEN do the LEYDIG CELLS (BETWEEN SEMINIFEROUS TUBULES) secrete TESTOSTERONE (masculine differentiation)
WEEK 8
TESTES DEVELOPMENT
what is TESTOSTERONE PRODUCTION STIMULATED by
HUMAN CHORIONIC GONADOTROPIN
TESTES DEVELOPMENT
when does TESTOSTERONE PRODUCTION stimulated by HUMAN CHORIONIC GONADOTROPIN PEAK
8TH-12TH WEEK
TESTES DEVELOPMENT
SERTOLI CELLS produce AMH until..
PUBERTY
when do OVARIES START to DIFFERENTIATE
12 WEEKS
OVARY DEVELOPMENT
what do PRIMORIAL GERM CELLS become and what do these consist of
PRIMORDIAL FOLLICLES
consisting of OOGONIA (derived from primordial germ cells)
OVARY DEVELOPMENT
PRIMORDIAL FOLLICLES are surrounded by a LAYER of..
FOLLICULAR CELLS derived from the SURFACE EPITHELIUM
OVARY DEVELOPMENT
thick CORDS that extend from the epithelium are known as… and what do they do
CORTICAL CORDS
PUSH INTO the UNDERLYING MESENCHYME
meet PRIMORDIAL GERM CELLS
-> break up into Clusters : PRIMORDIAL FOLLICLES
OVARY DEVELOPMENT
PRIMARY/PRIMORDIAL FOLLICLES are made up of
OOGONIA
and
FOLLICULAR CELLS (derived from cortical cords/surface epithelium)
OVARY DEVELOPMENT
when do OOGONIA stop forming (mitosis)
from BIRTH
TESTES DESCENT is brought about by the
SHORTENING of the GUBERNACULUM (connects testes to scrotum) as the foetus grows
When does DESCENT of TESTIS, epididymis and gubernaculum start
WEEK 23
at what point in Gestation do the TESTES PASS OUT through the anterior abdominal wall
23-30 WEEKS
as TESTES pass OUTSIDE what FORMS
INGUINAL CANAL
when are the TESTES in their FINAL POSITION in SCROTUM
between 28-32 WEEKS
In the presence of TDF/SRY which gene is switched ON
SOX9
on chromosome 17
Which gene is ACTIVATED when XX but silenced when XY
WNT4
