Embryology Flashcards
What germ layer does bones form from?
Mesoderm
What germ layer does nerves form from?
Ectoderm
What germ layers does skin and smooth muscle form from?
Ectoderm and mesoderm
What germ layer does cartilage form from?
Mesoderm
What is the fossa ovals?
Remnant of foramen ovale (petal cardiac shunt)
When do the pre-branchial arches start to form?
Week 4
What happens to the branchial arches in lat week 4?
5 arches start to from (6 starts to develop and 5 disappears)
With regards to the branchial arches, were is endoderm found?
Pouches between arches
What nerves supply the branchial arches?
- V3
- VII
- IX
- X (superior laryngeal)
- X (recurrent laryngeal)
What part of the head and neck develops from the first pharyngeal arch?
Maxilla, mandible, males and incus
What part of the head and neck develops from the second pharyngeal arch?
Stapes, soloed, part of hyoid
What part of the head and neck develops from the third pharyngeal arch?
Body and greater horn of hyoid
What part of the head and neck develops from the fourth and sixth pharyngeal arch?
Pharyngeal and laryngeal muscles and laryngeal cartilages
What does the face develop from?
5 prominences (frontal, 2 x maxillary, 2 x mandibular)
What does the philtre form from?
Medial nasal process growing downwards and laterally
How does the palate develop?
- Medial nasal process grows downwards
- From maxillary process, 2 palatine shelves grow inwards
- Palatine shelves meet in middle and form secondary palate
What does not fuse correctly during development resulting in cleft lip and palate?
Maxillary process
Medial nasal process
How do the skull bones form?
Vault = membranous ossification Base = endochondrial ossification Viscerocranium = mostly from branchial arches
When does the anterior fontanelle close?
1.5 years
What is the clinical significance of 6 membrane covered fontanelles?
Can feel raised ICP, indications for meningitis or hydration status etc
What is the term used for when bones fuse before they should causing other structures to protrude?
Craniosynostosis
Name a 1st pharyngeal arch abnormality.
Treachor Collins Syndrome
What germ layer forms the GI tract?
Endoderm
When is the foregut formed?
4th week
When does the spleen form and what is it derived from?
5th week from mesodermal derivative
When does the pancreas form and from what?
5th week when ventral and dorsal buds fuse.
Name two foregut anomalies.
Oesophageal atresia and trachea-oesophageal fistula
Annular pancreas
What are the two parts of the midgut formed during development?
Cephalic part
Caudal part
What must the midgut undergo during week 6?
Rotation and herniation
During which week does the herniated intestinal loop move from the umbilical cord back into the abdominal cavity?
Week 10
Name 3 midgut abnormalities.
Omphalocele
Meckel’s diverticulum
Gastroschisis
When is the handout formed?
End of week 7
Name 4 handout anomalies.
Urorectal fistula
Rectoanal fistula
Rectovaginal fistula
Imperforate anus
Where do the eyes develop from?
The neural tube
Where do the optical vesicles grow from?
Diencephalon
When optic vesicles reach surface ectoderm of the diencephalon, the cells of the surface thicken and form what?
Lens placode
As the optic cup is forming, blood vessels pass through a fissure in the inferior wall called what?
Choroid fissure
What forms from the telencephalon?
Cerebrum and lateral ventricles
What forms from the diencephalon?
Thalamus, hypothalamus, retina and 3rd ventricle
What forms from the mesencephalon?
Brain stem: midbrain and cerebral aqueduct
What forms from the metencephalon?
Cerebellum, brainstem: pons and 4th ventricle
What forms from the myelencephalon?
Brainstem: medulla and 4th ventricle, spinal cord
What week does brain development begin?
3
What does the nervous system for from?
Ectoderm
When does the CNS start to develop?
Week 3
What can result from failure of closure of the neural tube?
Anencephaly
Encephalocoele
Spina Bifida
What is the result of failure of the anterior neuropore to close?
Anencephaly
What is the result of failure of the posterior neuropore to close?
Encephalocoele
What results from the non-fusion of vertebral arches?
Spina Bifida
What vertebrae are most commonly affected in Spina Bifida?
L5 and 6
How is spina bifida diagnosed?
- Maternal blood screening - high levels of AFP
- Amniocentesis
- USS
What week does the 5 secondary brain vesicles start to form?
Week 5
What forms from the forebrain in week 5?
Telencephalon, diencephalon and mesencephalon
What are the ventricles formed from?
Lumen of neural tube
When does CSF form?
5th week
What do neural crest cells form?
PNS neurons and glia
What CNS cells migrate to the CNS?
All except microglia
What month does the spinal cord extend the entire length of the vertebral column?
3rd
When do the cortical folds start to develop?
26 weeks
What is the bladder and urethra formed from?
Urogenital sinus
What is the cloak divided into?
Rectum and urogenital sinus
What week doe the kidneys form?
4
What is the precursor for the meseonephric duct?
Pronephric duct
When does the pronephros degenerate around week 5, the mesonephros forms. What is it’s function?
Functions as kidney for 4 weeks (week 5-9)
What does the mesonephros become?
Developing gonad
What takes over from the mesonephros to form the kidney?
Metenephros
How does the metenephros form the kidneys?
Ureteric bud out of duct (calyces, pelvis, CDs, ureters)covered by metenephric mesoderm (kidneys)
Why do the kidneys appear to ascend?
From beside bladder up by differential growth of lower body inferiorly
When does kidney ascent stop?
Contact with adrenal glands
Name possible anomalies in the development of the kidneys.
Duplicate ureter
Aberrant renal artery
Pancake kidney
Horseshoe kidney
