Resp. Embryology Flashcards
Describe the process of fertilisation
Pronuclei of gametes form on diploid cell called a zygote
What does the zygote develop into?
A solid ball of cells (morula) and then into a blastocyst
Which parent passes on mitochondrial diseases?
Mother
What does Leber’s Hereditary Optic Neuropathy cause?
Blindness
Why does the morula develop into a blastocyst?
Too large for distribution of nutrients via diffusion
Where is 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 the Fallopian tube? How can malfunction of these structures cause pathology?
Healthy ciliated epithelia
Malfunction can cause ectopic pregnancy
What layer of the uterus is deep to the endometrium?
Myometrium
What happens to the zygote after its formed?
Divides to form the zygote, moves through uterine tube to uterine cavity
Describe the structure of the blastocyst
- Cells accumulated at one end - called an inner mass
- The outer lining of cells is called the trophoblast
What cells does gametes arise from?
Spermatogonium and oogonium
What layer of the uterus does the blastocyst implant into?
Endometrium
How does the formation of the chorion arise?
The trophoblast of the blastocysts divides several times to form the chorion
What are the different kind of twins that occur? What are the developmental differences?
Fraternal (dizygotic) and identical (monozygotic)
What structure plats a key role in implantation?
Chorion - the outermost surrounding membrane of the blastocyst
Describe the formation of the three germ layers
Epiblastic cells migrate into space between hypoblast and epiblast - forms trilaminar disc
From what germ layer does the notochord arise?
Ectoderm
How long does it take for the placenta to mature?
18-20 weeks
What four things occur during the third week of pregnancy?
Gastrulation, neurulation, development of somites and early development of the CV system
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 induces the ectoderm to form a neural tube?
Notochord - neural plate aides from ectoderm and sinks down to form neural tube
What feature of the epiblast determines the axis of the embryo?
The primitive streak (invagination of the epiblast layer of cells)
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 do each parts of the mesoderm develop into?
Paraxial mesoderm - somites
Intermediate - urogenital system
Lateral plate - body coverings and cavities
Approx. at what day of pregnancy does implantation occur?
7
What genetic factors can cause developmental issues?
Too many/few chromosomes
Structural changes
What does the real tube induce?
Thickening and segmentation of the mesoderm
What infectious agents can transfer through the placenta?
ToRCH
Toxoplasma, Rubella, Cytomegalovirus and Herpes
After the process of gastrulation, what happens?
Folding of embryo (lateral)
The inner cell mass of the blastocyst splits into two layers called what? What is their function?
Bilaminar disc - epiblast and hypoblast
Separate amniotic and yolk sac
Describe the genetics of gametes?
Genetically distinct
What are the three functions of the placenta?
- Foetal nutrition
- Transport of waste and gas
- Immune etc
What does the chorion do?
- Implantation
- Forms part of the placenta
- Secretes HCG
How does the paraxial mesoderm differentiate?
Into dermatomes, myotomes and sclerotomes
How is the diagnosis of malformations aided?
Prenantal and postnatal test
- Blood AFP
- Ultrasound (12 week anomaly)
- Invasive tests (chorionic villus sampling and amniocentesis)
- Hip stability
- Testes
- Fingers and toes
- Hearing
What environmental factors can effect development?
Drugs
Alcohol/tobacco
Infectious agents
Others including radiation etc.
What is the purpose of HCG?
Maintains endometrium
What are the key features of the second week of pregnancy?
- Implantation or morula and endometrial wall
- Cells from embryo form bilaminar disc
- Sacs, membranes nd cord to nourish human conceptus form
What three parts does the mesoderm split into?
Paraxial, intermediate and lateral plates
What are the three periods of human development in the womb?
- Pre-embryonic (weeks 0-30
- Embryonic (weeks 4-8)
- Foetal (weeks 9-40)
How is the parietal pleura formed?
From somatic mesoderm
What are the five stages of lung differentiation?
- Embryonic
- Pseudoglandular
- Canalicular
- Saccular
- Alveolar
What forms from the septum transverse?
Tendinous part of the diaphragm
What is formed from the two pleuroperitoneal membranes and peripheral body wall muscle?
Muscular part of the diaphragm
What process occurs in the third week of development and gives rise to primitive gut tube?
Folding of embryo; gut tube formed from endoderm
What is tracheosophageal fistula and atresia?
Fistula - abnormal or surgical made passage
Atresia - a condition in which an orifice is pathologically closed or absent
Where is the septum transverse initially located in the embryo?
Opposite somites C3-5 and then migrates caudally
When the septum transverse migrates caudally what structures does it bring with it?
Spinal nerves C3, 4 and 5
Where does a Bochdalek hernia occur?
Poseriolaterally on the diaphragm
Where does a Morgagni hernia occur?
Anteriorly on the abdominal diaphragm
What types of hiatal hernia are there?
Rolling (paraesophageal) and sliding
What forms from the mesentery of the oesophagus?
The crura of the diaphragm
The lung buds penetrate into which mesoderm? What does the mesoderm then turn into?
Visceral splanchnic mesoderm; visceral pleura
At what week does the diverticulum (laryngotracheal groove) appear?
4th
