Embryology Flashcards
Phases of human development
0-3 weeks, pre-embryonic phase
4-8 weeks, embryonic phase
9-40 weeks, foetal phase
Pre sperm cell
Spermatogonium
Pre egg cell
Oogonium
Zygote
Product of fertilisation
Morula
Solid ball of cells
Blastocyst
Group of cells with inner cell mass, blastocyst cavity and trophoblast outer lining of cells
Cell division timings
Decrease as more divisions occur
Abnormal cilia function
Can result in ectopic pregnancy
When does placenta develop
Day 6
Bilaminar disc
Shape the pre embryonic cells form
Chorion
Trophoblast has villi to implant in epithelium. Secretes Human Chorionoic Godatrophin which is used in pregnancy tests
Decidua basalis
Part of the endometrium deep to the implanted conceptus (with maternal blood vessels)
Myometrium
Smooth muscle around uterus
Bilaminar disc cavities
Amniotic above epiblasts, yolk sac below hypoblasts
Allantoic cavity
Waste products
Main functions of the placenta
Foetal nutrition, transport of waste and gases, immune
Foetal part and surface of placenta
Smooth with foetal blood vessels and end of umbilical cord
Maternal part of placenta
Decidua basalis of endometrium. Rough, with maternal blood vessels
Placenta facts
Matures by 18-20 weeks. Weighs 1/6 of the foetus
what happens in Week 3
Gastrulation (formation of germ layers), neuralation, development of somites and early development of cardiovascular system
Primitive streak
Formed in midline of epiblast, forms axis
Trilaminar disc formation
Epiblast cells migration and displace hypoblast, 3 germ layers formed: ectoderm, mesoderm, endoderm. Cells are now specialised
Notochord formation
Ectoderm sinks down, separates a bit into a solid tube of cells
Neural tube formation
Again ectoderm sinks to form neural plate, this folds to form neural tube
Mesoderm separation
Into paraxial mesoderm, intermediate plate mesoderm, lateral plate mesoderm (which splits into a v)
What does the paraxial mesoderm form
Somites
What does the intermediate plate mesoderm form
Urogenital system (kidneys and reproductive)
What does the lateral plate mesoderm form
Body cavity and coverings
Somites
Ridges/segments in paraxial mesoderm
Lateral folding of embryo
Ectoderm surrounds. Endoderm forms inner tube(gut). Lateral plate mesoderm forms squashed semicircular tube
Head and tail fold when will they be formed
By week 6
Further somite development into 3 categories
Dermatome(skin), myotome(muscle), sclerotome(bone)
Dermatome- compartment of somite turns into
Dermis of skin
Myotome, a somite section that turns into..
Muscles
Sclerotome, a somite that turns into..
Bones including vertebrae
What will ectoderm form
Epidermis of skin and neural tube (and notochord which forms the nucleus pulposes)
What will endoderm form
Gut and respiratory
What will mesoderm form
Dermis, muscles, bones, urogenital, peritoneum, pleura, body cavities
Teratology
Study of when things go wrong in pregnancy
Congenital rubella syndrome
German measles
Risk of teratogenesis
1-2 low risk as death risk is high, 3-8 high sensitivity to teratogens, weeks 9-38 decreasing sensitivity to teratogens
Diagnosis of prenatal malformations
Blood - AFP
Ultrasound at 12 weeks
Invasive eg Chorionoic sampling amniocentesis
Diagnosis of postnatal malformations
Hip stability
Testes descent
Fingers and toes
Hearing
When does respiratory system start and end developing
Tracheal buds form in 4th week, lobes are formed at 8 weeks
Foregut (oesophagus) buds to lungs
Laryngeal groove starts on ventral side which forms trachea from respiratory diverticulum then lung buds. Oesophagotracheal septum forms to separate them
Where do lung buds invaginate
Pleural cavities (splanchnic mesoderm) laterally forming the 2 layers like a squashed balloon
What forms the gut tube
Endoderm (foregut, midgut and hindgut) from embryo folding in week 3
Tracheoeosophageal fistula
When the trachea and oesophagus are accidentally connected
Atresia
An orifice or passage is abnormally closed or absent
The initial gaps between the parietal and visceral pleura
Pleuroperitoneal canals between somatic mesoderm and visceral mesoderm
What separates the pleural and pericardial cavities
Pleuropericardial folds
Embryonic phase
0-7 weeks
Pseudoglandular phase in respiratory
7-17 weeks, the pulmonary structures are all set up except those used for gas exchange
Canalicular phase in respiratory
17-27 weeks, terminal bronchioles make tubes for respiratory part of lung and type 1/2 pnuemocytes are differentiated
Saccular stage in respiratory
27-40 weeks, alveolar sacs are formed which divide and divide into alveoli
Alveolar stage in respiratory
32 weeks to 8 years, alveoli form and enlarge and number of respiratory bronchioles increase
RDS
Caused by lack of surfactant, a mixture of phospholipids and proteins
Respiratory congenital conditions
Accessory lobes, lobe of azygous vein, agenesis of lung (missing lung)
Hiatus hernia types
Sliding or paraesophageal/rolling (to the side)
