Applied Embryology Flashcards
Where does the process of fertilisation occur?
Fallopian tube
What happens once one sperm has entered the oocyte?
Oocyte becomes impenetrable to other sperm
What are the four steps in inplantattion?
Hatching
Apposition
Adhesion
Invasion
Briefly describe what happens in the apposition step of implantation.
First connection between blastocyst and endometrium.
Apposes to pinopodes (microvilli like structure) expressed on the receptive endometrium
Briefly describe what happens in the adhesion step of implantation.
Trophoblast of the blastocyst adheres to epithelial layer of endometrium
Embryonic tissue starts to secrete hCG
Briefly describe what happens in the hatching step of implantation.
Trophectoderm cells produce protease to dissolve the zona in preparation for the implantation
Briefly describe what happens in the invasion step of implantation.
Trophoblast proliferation, differentiation, crossing of the epithelial basement membrane and invasion of endometrial stroma to form placenta
->don’t get too hung up on this but could come up idk, depends on wording and stuff. I guess they could give five stages and ask ‘which of the following is NOT a step in the implantation process?’
Endometrium?
Lining of the uterus
After which stage of implantation would a pregnancy test show positive?
Adhesion
->due to secretion of hCG
What would happen if there was an inability for the blastocyst to hatch during implantation?
Infertility
What happens in the endometrium as it prepares to receive the embryo?
Stromal cell differentiation into decidual cells
Angiogenesis- new blood vessel formation
Increased macrophages, lymphocytes and decidual leukocytes (uterine NKC) for maternal immune tolerance
->these changes transform the endometrium to a vascular receptive tissue for the invasion of blastocysts
Is the placenta derived from foetal or mother tissues?
Fully developed from foetal tissues
Functions of the placenta?
Immunological barrier
Gas exchange
Nutrient exchange
Waste excretion
Endocrine functions*
->secretes hCG which maintains the pregnancy
What name is given to the changes in the endometrium as it prepares from the foetus?
Decidualization
Embryogenesis?
First eight weeks of embryo development post fertilisation
Briefly describe what happens in week 2-3 of embryogenesis.
Formation of bilaminar disc
Development of amniotic sac, yolk sac, extraembryonic mesoderm and chorionic cavity
Briefly describe what happens in week 3-4 of embryogenesis.
Bilaminar disc -> three germ layers (endoderm, mesoderm, ectoderm) through the process of gastrulation and neural tube formation
Briefly describe what happens in week 5-8 of embryogenesis.
Organogenesis
Two layers of the bilaminar disc?
Epiblast
Hypoblast
What does the epiblast go onto form?
Three germ layers
What does the hypoblast go onto form?
Extraembryonic mesoderm
List the derivatives of the ectoderm.
Epidermis
Central Nervous System
Peripheral Nervous System
Hair
Nails
Neuroendocrine organs (adrenal medulla, pituitary gland)
Enamel of teeth
List the derivatives of the mesoderm.
Dermis
MSK structures
Cardiovascular system
Kidneys
Ureters
Trigone of bladder
Gonads
Adrenal cortex
List the derivatives of the endoderm.
Lining of GIT
Parenchyma of liver
Pancreas
Thyroid
Parathyroid
Tonsils
Thymus
Bladder (excluding the trigone)
Urethra
The mesoderm divides into three major subunits. Name them.
Paraxial mesoderm
Intermediate mesoderm
Lateral plate mesoderm
Which part of the mesoderm does the urinary and repro system develop from?
Intermediate mesoderm
What are the two reasons why multiple pregnancies might occur (twins etc)?
Dizygotic- two or megs fertilising and implanting
Monozygotic- one embryo splitting
Which type of twins WON’T be identical?
Dizygotic
->two separate eggs being fertilised. In monozygotic, the twins will be identical as one egg is splitting
Is it more common to have identical twins or non-identical twins?
Non-identical twins
Are twins more likely in natural conception or fertility treatment e.g. IVF?
Fertility treatments
Monochorionic?
Twins share one placenta
Monoamniotic?
Twins share one smniotic sac
->this occurs is >5% of twin cases
Dichorionic?
Diamniotic?
Separate placenta
Separate amniotic sacs
What is the most common combo of placenta/amniotic sacs in twins?
Monochorionic
Diamniotic
->one placenta, two amniotic sacs, this occurs when the early embryo implants in the womb and then splits. If it splits before implanting in the womb, the two foetus have their own placenta.
Okay recap
Monozygotic vs dizygotic?
Monozygotic- one zygote splits, identical twins
Dizygotic- two zygotes, non-identical twins
Part of the urinary system (kidney and ureter) and reproductive system develop from what part of the intermediate mesoderm?
Urogenital ridge
Which develops first, urinary or repro system?
Urinary
Where do the gonads develop from?
Gondadal ridge
->gonads are originally indifferent, develop later into a testis or ovary
What does the Y chromosome contain which determines the production of a teste rather than an ovary?
SRY- sex -determining region Y
RECAP- why does their have to be a testicular descent?
Scrotal sack needs to be at a different temperature to the rest of the body for proper spermatogenesis to take place
Name the two sets of genital ducts.
Mesonephric duct
Paramesonephric duct
The presence of what determines which genital duct develops and which recesses?
AMH
->anti- =Mullerian hormone
In males, the presence of AMH means which genital duct develops?
Mesonephric duct develops, paramesonephric duct recesses
->M=male
When the mesonephric duct develops, what name do this ducts now have?
Wolffian ducts
->forms the trigone of the bladder in males and females
What do the Wolffian ducts do?
Drain the menephros into the cloaca
What do the Wolfferian ducts forms in males?
Epididymis
Vas deferens
Seminal vesicles
->only able to form these under the effect of testosterone.
What happens as the Wolffian ducts regress in females?
Remnants might remain as opoophoron, paraophoron (small cystic structures lateral to ovary) and garters duct cyst (benign lesions on the lateral vaginal wall).
What happens to the paramesonephric duct in females?
Grow medially and fuse, forming the uterus and 2/3 of vagina
Unfused portions give rise to fallopian tubes
If the paramesonephric ducts give rise to the upper 2/3 of the vagina, what forms the lower 1/3?
Urogenital sinus
The paramesonephric ducts fuse with the urogenital sinus at the sinus tubercle to form what?
Hymen
What forms the clitoris in females?
The genital tubercle
What forms the labia minora in females?
Urogenital folds
What forms the labia majora in females?
Labioscrotal folds
Micropenis is a male reproductive tract anomaly. What has happened?
Genital tubercle does not fully elongate
Hypospadias is a male reproductive tract anomaly. What has happened?
Urethral development problem causing opening to be abnormally located
In what condition may there by absence of vas deferens in males?
Cystic fibrosis
Cryptochordism?
Absent or undescended testicles
How common are female reproductive tract anomalies?
Common, 4-7% of women
What are the three reasons why uterine anomalies can happen?
Underdevelopment
Fusion defect
Resorption defect
Give examples of two uterine anomalies which can occur due to underdevelopment.
Uterine agenesis
Unicornuate uterus
Give examples of two uterine anomalies which can occur due to fusion defects.
Didelphys uterus
Bicornuate uterus
Give examples of two uterine anomalies which can occur due to resorption defects.
Separate uterus
Arcuate uterus
Which investigation is used to identify uterine anomalies?
3D Ultrasound
List some of the congenital female anomalies which aren’t to do with the uterus.
Vaginal septa
Imperforate hymen
Vaginal agenesis
Name a syndrome in which is common for their to be female reproductive anomalies.
MKRH syndrome
What happens in Mullerian agenesis syndrome?
Full female reproductive tract but parts or all of the uterus or vagina will be absent
What can these reproductive anomalies have an effect on?
Fertility
Urinary function
