Embryology Flashcards
What are the developmental phased before birth ?
Pre-embryonic 0-3 weeks, embryonic 4-8 weeks, foetal phase 9-40 weeks
What are the stages after birth?
Post-natal, childhood, adolescence
At what day heart stars beating?
rudimentary heart starts beating at day 24
What does surround oogonium?
Follicle that secretes hormones to support the cell
Describe the process of fertilisation?
Pronucleus of sperm fuses with pronucleus of ovum forming diploid zygote
What is the first cell in human body?
Zygote, in week one, pre-embyinoc stage
What is blastocyst?
group of cells with blastocyst cavity, the division happens as it moves through uterine tube to reach uterine cavity, day 5-6
What is morula?
A solid mass of cells
State the sequence of stages
Zygote, morula, blastula
Give an example of mitochondrial inherited disease?
Levers hereditary optic neuropathy
Name the parts of blastocyst
Blastocystic cavity, inner cell mass, outer lining trophoblast
By which day blastocyst is formed?
By day 5
Each successive mitosis happens faster, true or false?
true
What is ectopic pregnancy?
Implantation of zygote in uterine tube, this happens to due faulty cilia
What is formed from trophoblast after day 6?
Chorion and chorionic villi that will penetrate to endometrium and form part of placenta
Where is human chorionic gonadotrophin secreted?
From chorionic villi
What is the role of human groin gonadotrophin hormone?
It stimulates ovary to produce oestrogen and progesterone to maintain the endometrium
What does stimulate endometrium formation before implantation?
Oestrogen and progesterone produced by follicle
What happens around day 7 ?
Blastocyst burrows to the endometrium, endometrium is now called decidua
What is decidua?
endometrium where is blastocyst implanted
What is decidua basalis?
Part of endometrium rich in maternal blood vessels
What forms from the inner cell mass?
Bilaminar disk, epiblast (top) and hypoblast (bottom)
What are the two cavities formed in bilaminar disk?
Amniotic cavity at the top, yolk cavity at the bottom
What is the role of yolk sack?
It provides nutrition, it gets smaller as embryo grows
What is allantoic cavity?
Allantoic cavity is for waste products, it gets bigger as embryo grows
Does maternal and foetal blood mix?
No, all exchanges happen by diffusion
Describe the surfaces of the placenta
Maternal surface is rough, decidua basalis with maternal blood vessels, foetal surface is smooth, with foetal blood in umbilical cord, covered in amniotic membrane
What is the function of placenta ?
Nutrition, transport of gases and wastes, immunity
When does the levels of human chorion gonadotrophin hormones peak?
About week 12
When does placenta mature?
Week 18-20
What are the two types of twins?
Fraternal/dizygotic - 2 ova and 2 placentas, identical/monozygotic - 1 ova only, divides into two cells that each develop to different foetus
What does begin in week 3 ?
Gastrulation process, 3 germ layers develop and neurulation process
What is primate streak and how is it formed ?
Group of cells from the midline of epiblast that are formed by dipping, they are very active and rapidly divide, form axis of the embryo, go between epiblast and hypoblast and replace hypoblast cells
What is the end product of gastrulation?
trilaminar disk, consists of ectoderm, mesoderm, endoderm, cells have now become specialised
What is notochord and hoc it is formed?
A solid tube formed from rapidly dividing epiblast cells that sunk down to the space between mesoderm and endoderm
What is the role to notochord?
It signals to the ectoderm to form neural tube, many signalling pathways, sonic hedgehog is one of them, ectoderm first thickens forming neural plate and then sinks down to the space between ectoderm and mesoderm forming neural plate
What is the name of the process whereby neural tube is formed?
Neurulation
What does happen to mesoderm after neural tube is formed?
Mesoderm thickens and divides into three parts -paraxial mesoderm (somites), intermediate (urinogenital and kidneys) lateral mesoderm (body cavities and coverings)
What happens to each somite and how many are there?
there are 43 somites, they divide into three parts, 1 is dermatome (dermis of skin), 2. myotome (muscles) 3 sclerotome (bones)
What happens to lateral mesoderm?
Splits into somatic and splanchnic mesoderm, space in between is intraembryonic coelom
In week 4 what happens to neural tube?
Neural tube develops to forebrain, midbrain, hindbrain, spinal cord
What developmental processes happen at week 4?
Gut formation from endoderm, urinogenital formation from intermediate mesoderm, body cavities from lateral mesoderm, somites from paraxial mesoderm, limb buds and neck development pharyngeal arches
What is lateral folding?
Folding al the three layers and the the lateral mesoderm is heavy, somatic and splanchnic mesoderm join together creating a cavity in the middle, somatic is on the outside, splanchnic on the inside, cavity if formed in the middle
What is formed from somatic and splanchnic mesoderm?
Parietal membrane from the somatic mesoderm, visceral membrane from the splanchnic mesoderm
What happens around week 6?
Another folding as neural tube is growing rapidly
What does form from ectoderm?
Epidermis of the skin, neural tube
What does from from endoderm?
gut and respiratory
What are teratogens?
Environmetal factors that cause abnormal development
When there is the highest risk of premature death?
weeks 1-2
When is the embryo most sensitive to teratogens?
weeks 3-8
What are the diagnostic tests for malformations?
Blood alpha -fetoprotein (marker for spinal bifida, encelopahty), ultrasoun scans, invasive test chorion villus sampling, amniocentesis
