Embryology Flashcards
What is the name of the protein coat that surrounds the oocyte that dissapears by blastocyst stage to allow it to penetrate the endometrial wall?
Zena Pellucida
3 Components of an early blastocyst?
Outer layer of trophoblasts
Inner cell mass
Blastoceale - cavity
The trophoblasts will give rise to what and secrete what after implantation?
Placenta, secrete HCG
The inner cell mass will form a bilaminar disc composed of which two layers?
Epiblasts and hypoblasts
What is the process which includes the differentiation of this bilaminar disc to a trilaminar disc, and when does it occur?
Gastrulation. Begins immediately after implantation trilaminar disc is formed by 4 weeks.
Main steps of gastrulation?
Epiblasts invaginate through primitive streak
Bury into hypoblasts layer and differentiate
3rd middle layer formed –> mesoderm.
Epiblasts –> ectoderm
Hypoblasts –> endoderm.
After gastrulation is complete what process begins?
Nuerolation
In neurulation cells of the Mesoderm differentiate to form ____A____ and the Ectoderm thickens to form ___B___?
A. Notocord
B. Nueral plate
How does the nueral tube form from the nural plate?
Nueral groove (of plate) invaginates (dives towards notocord) and then seals as a tube in mesoderm
Ectoderm will become…?
Epidermis & Nervous system
Endoderm will become?
Lining of - gut, RT, bladder and urethra
Mesoderm differentiates into which 3 groups either side of notochord?
(from medial to lateral)
Paraxial
Intermediate
Lateral
Visceral mesoderm laterally folds to form?
Gut tube
Somatic mesoderm folds laterally and zips anterior to form?
Somatic body
Space inbetween these that gives rise to pericardium, plueral cavity and peritoneal cavity is called?
Intra-embryonic coeleum
Urogenital system arises from which group of mesoderm?
Intermediate mesoderm.
During weeks 4-6 what migrates to teh intermediate mesoderm to start the sexual gonadal development?
PGCs - Primordial germ cells.
coelemic epithelium (covers intermediate mesoderm) thickens and gives rise to?
genital ridges
Which cells are formed during proliferation of coelomic epithelium which surround primordial germ cells?
Somatic support cells.
The ambisexual phase gives rise to the development of which two ducts?
Wollfian duct & Mullerian.
Where do these ducts connect?
Posterior abdominal wall
Sexual differentiation occurs from which week onwards?
Week 7
Which part of the Y chromosome is sex defining?
SRY region. –> male development.
The PGCs mirgrate to intermnediate mesoderm and become enveloped in somatic supporting cells with proliferating epithelium around it this is now referred to as?
Primitive sex cords. - become either testis cords or cortical cords in female.
In males somatic support cells develop into?
Sertoli cells
what connects the mesonephric tubules to the testis cords?
Rete testis
what is the name given to the thickened layer of connective tissue that forms between the coelomic epithelium and the testis cords (white coat over testes)?
Tunica albuginae
what 2 things occur as a result of the sertoli cells that ensure internal MALE genital tract develops?
- AMH produced –> degeneration of mullerian (female duct)
2. Stimulation of leydig cell formation. Leydig cells secrete testosterone.
How will those with persistant mullerian duct syndrome present?
Internal genital tract develops femal - Uterus, vagina and uterine tubes.
Testes in ovarian location
Male external genitalia
What hormone must be secreted for
A) internal male genitalia
B) external male genitalia
???
A) AMH
B) DHT
Testosterone acts on mesonephric (wollfian duct )to form which 3 structures? /
- Epididymis
- Vas deferans
- seminal vesicles
Testes develop at which thoracic level?
10th
Muscle layer which doesnt contribute to spermatic cord?
transverse abdominus.
Name given to undescended testes?
cryptorchidism
Which 3 accessory glands arise near junction of wollfian duct and urethra?
- Prostate
Bulbourethral
Seminal Vesicle
Female development occurs in the absence of ?
SRY transcription factor
In female development somatic support cells differentiate into?
Granulosa cells.
Granulosa cells secrete oestrogen which stimulates devlepment of mullerian ducts into ?
Uterine tubes
Uterus
Superior vagina
3 parts of mullerian duct?
- Cranial
- Caudal
- Horizontal
which portion of the mullerian duct opens into developing peritoneal cavity?
Cranial
What is hypospadius?
External urethral opening lies abnormally along ventral aspect of penis.
