Embryology Flashcards
What are the 3 major step in fertilisation
1) capacitation of the sperm
2) stem binding to the zona pellucida and releases nucleus. Lysosomal enzymes from cortical granules inactivate receptors
3) egg pronucleus and sperm pronucleus fuse
What happens to the egg when it fuses with the sperms pronucleus
Undergoes meiosis 2 to from a zygote
What are the specialisation of an egg
- mitchondria
- nucleus
- acrosome
- flagellum
What is cleavage
Zygote forms a morula
How many cells does a morula have
16
When does cleavage occur
After the zygote has formed
What happens when a morula is formed
The cells of the morula line to form a blastocyst
What is a blastocyst made of
- trophoblast
- embryoblast
What are the 3 layers of the uterus wall
- endometrium
- myometrium
- perimetrium
What happens to the endometrium uterus wall
1) proliferative : estrogen levels are high
2) secretory : corpus leteum produce progesterone to produce compact, basal spongy layer and implantation occur
3) menstrual
What happens to the trophoblast at implantation
Differentiates into
- cytotrophoblast
- synctiotrophoblast
What happens to the embryoblast at implantation
Differentiates into
- hypoblast
- epiblast
What happens to the syncitium when the egg has become implanted
Vacuoles appar called lacunae and blood inverts into it
What does the cytotrophoblast do to the synctiotrophoblast
Create villus structures of primary, secondary and tertiary
What does the hypoblast form
The primitive yolk sac
What hormones does the synctiotrophoblast secrete when implantated
- hcg
- progesterone
- hPL
Take the role of the corpus leteum until birth
What are the 4 placental barriers
- endothelium of villus
- synctiotrophoblast
- cytotrophoblast
- Loose connective tissue surrounding endothelium
If there is a malignant tumour how can this be identified
It will show high levels of HCG
What is gastrulation
The formation of the trilaminar disc
How does gastrulation occur
- epiblast forms a primitive streak
- cells from the epiblast migrate underneath the primitive streak to form endoderm mesoderm
- remaining epiblast cells form ectoderm
What occurs after gastrulation
Neuralation
What is neuralation
The formation of the neural tube
What happens at neuralation
Ectodermal cells migrate through primitive pit to from notochord
Notochord releases growth factor and ectoderm proliferate to from neural plate
Neural plate fold to from neural tube
Neural crest remain on top of the notochord
When the notochord is formed which layer is it found at
The mesoderm
What is the 4 role of the neural crest
1) form dorsal root ganglion
2) form neuro-endocrine cells e.g adrenal gland
3) melanocytes for skin colour
4) fascial mesenchyme
How does the mesoderm develop
Split into 3 regions
- paraxial
- intermediate
- lateral
What does the paraxial mesoderm develop into
42-44 somites
Muscles
What does the intermediate mesoderm develop into
Urogenital system
What does the lateral mesoderm plate develop into
Heart
What does the somites do
Form the vertebral column around the neural tube and notochord when sclerotome migrate
Spinal nerves migrate out laterally to from the vertebral column
How does the intermediate mesoderm form the urogenital sytem
Intermediate grow into
- pronephros : this degrades
- mesoneprhros: grows
- metanephros: kidney develop here
Gonads are form when germ cells migrate onto the intermediate mesoderm to from gonadal ridge which give gonads
How does the action at the mesoderm differ in females and males
Male has mesonephric remains to form testis
Female has paramesonephric to form vagina
What physical form does the lateral mesoderm split into
- somatic
- splanchnic
What dos the splanchnic mesoderm develop into
The heart
How is the heart derived
The progenitor cells of the splanchnic mesoderm from endocardial tubes
Endorcardial tubes fuse together
This forms the Ventura, atrium , ventricle, bulbous cordis and truncus ateriousus
What happens to the atrium and the heart in further development
Portion into 2 chambers each
If the heart does not portion out what can be a consequence of this
A hole in the heart
Does the anterior or posterior plate form the heart
Anterior
How does the heart get to its correct location in the body
By sagitall folding when the head and tail bend
What are the two types of embryonic folding
- lateral
- sagitall
What occurs when lateral folding takes place
- the gut tube forms
How is the gut tube formed at lateral folding
The amniotic cavity folds laterally
The yolk sac is pinched off to from the gut tube
Body cavity is formed by the lateral plates
How does the gut tube develop
Separates into 3 regions to derive
- foregut: oesophageal and stomach
- midgut : small intestine
- hindgut : large intestine
By what process does the neural tube develop
Vasiculation
What does the neural tube develop into
The CNS
What happens at vasciculation
Forebrain:
- telencephalon
- diencephalon
Midbrain:
- mesencephalon
Hindbrain:
- metencephalon
- myelencephalon
What does the telencephalon derive into further
Olfactory lobes
Hippocampus
Cerebrum
What does the diencephalon develop into
Optic vesicle
Epithalamus
Thalamus hypothalmus
What does the mesencephalon develop into
Mid brain
What does the metencephalon develop into
Cerebellum
Pons
What does the myelencephalon divide into
Medulla
What are the 3 major neural tube defects of the brain
Hydrocephalus
Microcephaly
Anencephaly
What is hydrocephalus
Water on the brain creates narrow slylvious and prevent blood blow to the blood vessels
What is microcephaly
Small brain due to lack of forebrain induction
What is anencephaly
Most of the brain absent due to from end of neural tube failing
How can you identify neural tube defects
Look at high levels of alpha Fetoprotein
What are the 3 main types of Spina bifida
Occulta
Meningocele
Meyelocoele
What does Spina bidifa occur
As a result of not folding fully when the neural plates fold to create the neural tube
At which structure does the future bladder develop from
Allantois
How many pharyngeal pouches are there
4
What does the first pouch give
Middle ear
Pharygontympanic tube
What does the second pouch give
Palatine tonsil
What does the third pitch give
Parathyroid gland (inferior) Thymus
What does the 4th pouch give
Superior parathyroid
Small part of thyroid gland
