Embryology 1 and 2 Flashcards
What are the three periods of human development in the womb?
- Pre-embryonic (weeks 0-3)
- Embryonic (weeks 4-8)
- Foetal (weeks 9-40)
What cells does gametes arise from?
Spermatogonium and oogonium
Describe the genetics of gametes?
Genetically distinct
Describe the process of fertilisation?
Pronuclei of gametes form one diploid cells called a zygote
What happens to the zygote after its formed?
Divides to form zygote, moves through uterine tube to uterine cavity
What does the zygote develop into?
A solid ball of cells (morula) then into a blastocyst
Which parent passes on mitochondrial disease?
Mother
What does Leber’s Hereditary Optic Neuropathy cause?
Blindness
Why does the morula develop into a blastocyst?
As the morula gets larger, distribution of nutrients gets harder - - therefore the blastocystic cavity develops
Describe the structure of the blastocyst?
- Cells accumulated at one end - called an inner mass
- The outer lining of cells is called the trophoblast
Where is the pre-embryonic material at the stage of being a zygote, morula and blastocysts respectively?
Zygote - Fallopian tube
Morula and blastocyst - Uterine cavity
What structures are required to transport the morula through thebFallopian tube? How can malfunction of this structure lead to pathology?
Healthy ciliated epithelium - malfunction can cause ectopic pregnancy
What are the key features of the second week of pregnancy?
- Implantation of morula in the endometrial wall
- Cells from the embryo form bilaminar disc
- Sacs, membranes and cord to nourish the human conceptus develop
Approx. at what day of pregnancy does implantation occur?
7
What layer of the uterus does the blastocyst implant into?
Endometrium
What structure plays a key role in implantation?
Chorion - the outermost membrane surrounding the blastocyst
How does the formation of the chorion arise?
The trophoblast of the blastocysts divides several times to form the chorion
What does the chorion do?
- Implantation
- Forms part of the placenta
- Secretes HCG
What layer of the uterus is deep to the endometrium?
Myometrium
What is the purpose of HCG?
Maintains the endometrium
The inner cell mass of the blastocyst splits into two layers; what is this called? What is its function?
Bilaminar disc - Epiblast and Hypoblast
Separate amniotic and yolk sac
What are the three functions of the placenta?
- Foetal nutrition
- Transport of waste and gas
- Immune etc
How long does it take for the placenta to mature:
18-20 weeks
What are the different kind of twins that occur? What are the developmental differences?
Fraternal (dizygotic) and Identical (monoygotic)
What four things occur during the third week of pregnancy?
Gastrulation, neurulation, development of somites and early development of cardiovascular system
What feature of the epiblast determines the axis of the embryo?
The primitive streak (invagination of the epiblastic layer of cells)
Describe the formation of the three germ layers?
Epiblastic cells migrate ito space between hypoblast and epiblast - formation of trilaminar disc
From what germ layer does the notochord arise?
Ectoderm (primitive notch of of epiblast)
What induces the ectoderm to form a neural tube?
Notochord - neural plate arises from ectoderm and sinks down to form the neural tube
What does the neural tube induce?
Thickening and segmentation of the mesoderm
What three parts does the mesoderm split into?
Paraxial, Intermediate plate and lateral plate
How does the lateral plate mesoderm further divide?
Into the somatic and splanchnic mesoderm
What is the space between the splanchnic and somatic mesoderm called?
Intra-Embryonic coelom
What do each parts of the mesoderm develop into?
Paraxial mesoderm - somites
Intermediate - urogenital system
- Lateral plate - body coverings and cavities q
After the process of gastrulation, what happens?
Folding of embryo (lateral)
How does the paraxial mesoderm differentiate?
Into dermatomes, myotomes and sclerotomes
What is teratology?
The study of when things go wrong during development
What is the cause of 60% of all developmental abnormalities?
Unknown causes
What environmental factors can effect development?
Drugs - prescription/other
Alcohol/ tobacco
Infectious agents
Others e.g. radiation
What infectious agents can transfer through the placenta?
ToRCH
Toxoplasma, Rubella, Cytomegalovirus, Herpes
What genetic factors can cause developmental issues?
Too many/few chromosomes
Structural changes
How is the diagnosis of malformations aided?
Prenatal and postnatal test
- Blood -AFP
- Ultrasound (12 week anomaly)
- Invasive tests e.g. chroionic vilus sampling and amniocentesis
- Hip stability
- Testes (descent)
- Fingers and toes
- Hearing
