Embryology Flashcards
REVIEW
What is the stage where the germ layers are formed known as?
At what gestation does this occur?
The mesoderm is organised into 3 main groups, what are they?
Gastulation
The first 3 weeks of development
Paraxial, intermediate and lateral
REVIEW
Lateral folding forms what type of section?
Cranial folding forms what type of section?
Axial section
Sagittal section
THE UROGENITAL SYSTEM
This system arises from which germ layer (be specific)?
The intermediate mesoderm
INDIFFERENT GONADS
This structure can develop into what?
At what weeks gestation are the indifferent gonads present?
It is the presence of what that causes these to develop along male lines?
Testes or ovaries
4-6 weeks
SRY gene
AMBISEXUAL PHASE
As well as the indifferent gonads, what else help form this phase of development?
From what gestation does sex differentiation occur?
The genital ducts; mesonephric (Wolffian) and paramesonephric (Mullerian)
Week 7 onwards
MALE DEVELOPMENT
This is triggered by the presence of what?
Somatic suppport cells develop into what?
What structure connects the mesonephric tubules (Wolffian duct) to the testis cords?
Between the coelemic epithelium and testis cords, a thickened layer of connective tissue forms what?
What are some remnants of the Mullerian duct?
SRY transcription factor
Sertoli cells
Rete testis
Tunica albuginea
Appendix tesis and prostatic utricle
MALE DEVELOPMENT
Sertoli cells secrete anti-Mullerian hormone - what is the purpose of this?
Sertoli cells stimulate gonadal ridge cells to form what?
To degenerate the Mullerian duct, and prevent female structures from developing
Leydig cells
MALE DEVELOPMENT
Testosterone induces the formation of what structures?
Dihydrotestosterone induces the formation of what structures?
If dihydrotestosterone is not present, what happens?
If the Mullerian duct fails to regress, what can happen?
Epididymis, vas deferens and seminal vesicles
External genitalia and prostate
Female external genitalia will be present
Can have female reproductive organs, testes in an ovarian location with male external genitalia
MALE DEVELOPMENT
Where do the testes originate?
Failure of the testes to descend is known as what?
What is the management if the testes are not descended at birth and why?
What is the role of the tunica vaginalis?
10th thoracic level
Cryptochidism
Pull down surgically in the first year, undescended testes can lead to germ cell tumours
To reduce friction when the cremasteric muscle contracts
MALE DEVELOPMENT
3 accessory glands spout near the junction of the Wolffian duct and urethra at what gestation?
What are these structures?
This development is initially controlled by hormones from where?
Once developed, what structure takes over hormonal control?
10 weeks
Prostate gland, bulbourethral gland and seminal vesicle
Placenta
Anterior pituitary
FEMALE DEVELOPMENT
This occurs in the absence of what?
This results in the bipotential gonad developing into what?
The influence of what stimulates the formation of female external genitalia and development of the Mullerian duct?
SRY transcription factor
Ovaries
Ovarian oestrogens and maternal sources
FEMALE DEVELOPMENT
The Mullerian duct gives rise to its structures at what gestation?
What structures does it give rise to?
Why does the Wolffian duct degenerate?
Week 10
Uterine tubes, uterus and superior vagina
Because there and no testes and hence no testosterone
EXTERNAL GENITALIA
At what gestation are the external genitalia indifferent?
By what time has the foreskin formed?
What is hypospadias?
What structures of the male and female external genitalia actually come from the same beginning point, the difference being that one shrinks and one grows?
Weeks 4-7
Week 12
The external urethral opening lies in an abnormal position on the ventral aspect of the penis
The clitoris and glands penis
DUCTS
In males, what does the mesonephric (Wolffian) duct go on to become?
In females, what does the paramesonephric (Mullerian) duct go on to become?
The vas deferens
The fornix of the vagina
