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70 Cards in this Set

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the tissue in between the ectoderm and endoderm of the pharyngeal arches is made by what?
mesoderm, neural crest cells, and mesenchyme
In between each ipsilateral pharyngeal arch are what structures (where gills would be on fish)?
pharyngeal cleft laterally and the pharyngeal puch medially
what is the space located between each column of pharyngeal arches?
the pharynx
Where do neural crest cells originate from?
neural ectoderm
what do the three non overlapping streams of neural crest cells to the head, face, and pharyngeal arch mesoderm become?
cranial nerve ganglion and mesenchyme (forms CT and skeletal tissue in this area). These streams also provide axonal guidance
the homeobox genes and other genes in the neural crest cells are regulated by what? what growth and patterning proteins have a role in the proliferation of neural crest cells in the arches?
? retinoic acid. sonic hedgehog and FGF8.
mesenchyme derived from where will produce the bones for the anterior skull and face? Posterior (parietal on...)?
neural crest cells. paraxial mesoderm
pair the arches with their associated arteries.
. Left side: carotid is 3rd, aorta is 4th and ductus arteriosus is 6th. Right: carotid is 3rd, right subclavian is 4th, and pulmonary is 6th
why does the recurrent laryngeal loop around the subclavian?
? it originally loops around the 6th arch artery which will regress on the right and thus the nerve will ascend.
what nerves are associated with what arches?
the trigem with 1. the facial with 2. glossopharyngeal with 3. vagus with 4 and 6.
What cartilages are associated with what arches?
1st is meckel’s, 2nd is reichert’s, 3rd is hyoid bone, 4th and 6th are larynx.
The incus, malleus, and mandible develop from what arch?
1st
What bones develop from from the second arch?
Stapes, styloid process, lesser horn of hyoid.
All skeletal muscle is derived from what germ layer?
The mesoderm
Where do the myoblasts migrate from to form the extrinsic eye muscles? Pharyngeal arch muscles? Tongue muscles? Neck muscles?
Somitomeres. Somitomeres and occipital somites. Occipital somites. Occipital and cervical somites
Induction of what by the notochord and then the paraxial mesoderm results in the formation of the inner ear?
Induction of the surface ectoderm forming the otic placode (later becomes otic vesicle)
The middle and external ear develop from what?
From pharyngeal cleft and pouch of the 1st arch
Of what germ layers is the tympanic membrane composed?
Ectoderm, mesoderm, and endoderm.
What arches make up the auricle?
1 and 2.
Infection with rubella during weeks 7 and 8 may do what?
Defects in the inner ear organ of corti which result in permanent congenital deafness. also may cause congenital cataracts in developing lens
What are the effects of auricular defects and accessory auricular nodules?
Nothing really, easily removed, but check for deafness due to atresia of external auditory meatus which is repairable
Characterize first arch syndrome and give an example of it.
Usually craniofacial dysostoses (like hypoplasia of mandible and maxilla). Treacher Collin’s syndrome is an example as well as agnathia in which the lower jaw fails to form (extreme case).
Pouch 1 develops into what? Pouch 2?
Auditory tube and middle ear cavity. Tonsillar epithelium (note that the tonsil itself is derived from mesoderm).
Pouch 3 develops into what? Pouch 4?
Thymus and inferior parathyroid. Superior parathyroids and the ultimobranchial body (gives the thyroid gland calcitonin secreting C cells).
Characterize DiGeorge Syndrome.
Neural crest deficiency characterized by 1st arch syndrome plus failure of thymus and parathyroids to differentiate from pouches 3 and 4, thus immune deficiencies and hypocalcemia. Usually chrom mutation, but can be caused by diabetes or alcohol.
The pharyngeal floor gives rise to what structures?
The trachea, lung bud, tongue, thyroid gland, and rathke’s pouch (dorsal ectodermal outpocket from the oral cavity which merges with the neuroectoderm of the hypothalamus to form the anterior lobe of the pituitary).
What arches will give rise to the tongue (say which gives the most and what portion)?
All 4. The 1st arch makes up the anterior 2/3 of the tongue by knocking the 2nd arch back. The root or posterior 1/3 is from the third arch while the epiglottic portion is from the 4th.
What structure seperates the root and body of the tongue?
The foramen cecum.
Where does the thyroid gland originate from? What is usually left over from this migration, but can cause what congenital effects?
From the endothelium of the foramen cecum in the tongue and descends via the thyroglossal duct to the anterior portion. Leaves the pyramidal lobe of the thyroid gland, but the duct maybe left over forming a midline thyrocervical duct sinus, cyst, or accessory thyroid gland.
Overgrowth of the 2nd pharyngeal arch over the 3rd and 4th arch will result in what?
a space called a cervical sinus which may develop into cervical sinus cysts and/or fistulas in the neck. Note they are located anterior to the sternocleidomastoid. They also may open internally into the palatine tonsillar area or externally into the skin.
what layer is the lens epithelium taken from and what structure causes this invagination?
the ectoderm is induced to form the lens placcode by the developing optic cup.
how is the central artery of the retina formed?
the choroid fissure forms in the optic stalk and cup and is penetrated by the hyaloid artery that becomes the central artery of the retina
what occurs if the choroid fissure in the optic cup fails to close?
unclosed iris AKA coloboma iris
what parts of the eye arise from neuroectoderm? mesenchyme? surface ectoderm?
retina, pigment layer, iris, ciliary body. choroid layer, vitreous body, sclera, and corneal connective tissue. corneal epi and lens
how does olfactory epithelium develop?
ectoderm from the olfactory placode area migrates through the olfactory pit at the base of the skull
what congenital defect is associated with olfactory development?
for some reason the migrating ectoderm cells that become nasla epi also migrate to the hypothal to make gonadotropin releasing hormone. Failure of this results in Kallman syndrome characterized by anosmia and hypogonadism.
the medial nasal processes form what structures upon fusion?
philtrum of lip, 4 upper incisors, and the primary palate (area anterior to the incisive foramen).
what marks the point of fusion between the primary and secondary palates?
incisive foramen.
what processes fuse to form the palate? what also must fuse with the palate at this time?
the medial palatal process and the lateral palatal shelves. the nasal septum
cleft lips and palates are generally due to what?
insufficient number of neural crest cells due to a number of genes and teratogens
what results from a failure of the maxillary process to merge with the medial nasal process?
cleft lip and primary palate
failure of the two lateral palatal shelves and the nasal septum to fuse results in what?
cleft palate
failure of fusion of the maxillary process and the lateral nasal process results in what?
oblique facial cleft with an exposed nasolacrimal duct
what results from failure of fusion of the maxillary process and the mandible?
transverse cleft or macrostomia (wide mouth)
what happens to the teeth in a cleft palate or lip situation? why?
misaligned teeth since they are derived from oral ectoderm and from mesenchyme which comes from neural crests
failure of the medial nasal processes to merge results in what? what classification of defect is this and what is a common cause of these defects?
midline cleft which is a holoprosencephalic defect ususally due to sonic hedgehog mutation (determines embryonic midline) and may result in brain damage due improper CNS development
what results from an excess of tissue production in the frontonasal prominence and hypertelorism?
frontonasal dysplasia
describe primary neurulation.
formation of neural tube by infolding of cervical neural plate first then proceeding in both directions giving rise to two neuropores at each end which maybe involved in defects if they do not close.
describe secondary neurulation and what it gives rise to.
a cell mass called the caudal eminence (not part of the neural plate) appears caudally to the neural tube and fuses with it as it enlarges giving rise to the sacral and coccygeal segments of the spinal cord.
malformations caused by failure of the neuropores to close is called what?
dysraphic defects
what are caused by failure of anterior neuropore closure?
anencephaly, encephalocele, and arnold chiari malformation
in an encephalocele, what is the most common site of the opening?
the squamous part of the occipital bone
describe the three types of encephaloceles.
meningocele only has meninges buldge through. meningoencephalocele includes meninges and part of brain. meningohydroencephalocele includes meninges, part of brain, and part of the ventricles
describe arnold chiari malformations...
congenital herniation of cerebellar vermis through the foramen magnum. associated with syringomyelia (cavitation of cord) and syringobulbia (cavitation of medulla). It usually occurs in almost every case of spina bifida cystica and usually accompanied by hydrocephalus
what are the defects of the posterior neuropore?
myeloschisis - all the spina bifidas
describe spina bifida occulta, aperta, and cystica.
vertebral defect is covered by skin but does not involve neural tissue; usually marked by hair over affected side. skin is not closed over defect. meninges and/or neural tube with nerves protrude forming a cyst, usually no MR, include meningoceles and meningomyeloceles.
defects of secondary neurulation are called what? give a common example.
myelodysplasia, usually covered by skin but may be marked by pigment or hair. tethered cord syndrome is when the conus medularis and the filum are fixed to the defective vertebral column resulting in cord damage, loss of leg sensation, bladder issues...
neural crest cells give rise to what? help form what?
neurons of sensory ganglia (spinal and CN's) and autonomic ganglia. schwann cells, satellite cells, pia, arachnoid, cilliary and pupillary muscles, and placcodes (specialized epidermal cells in the cephalic region).
describe brain development.
begins with 3 vesicles (prosencephalon, mesencephalon, and rhombencephalon) seperated by the cephalic and cervical flexures. Then telencephalic flexure divides the prosencephalon into the telencephalon (cerebral cortex) and the diencephalon (thalmic structures). The rhombencephalon is then divided by the pontine flexure into the metancephalon (pons and cerebellum) and mylenecephalon (medulla)
the diencephalon gives rise to what?
epithal, dorsal thal, hypothal, optic nerve and retina
define holoprosencephaly and what are its two types?
failure of the prosencephalon to undergo cleavage. Alobar is characterized by a single large ventricle lacking corpus callosum, falx cerebri, and olfactory structures. Semilobar results in some seperation thus rudimentary lobes and gyri, but infants have facial malformations like cyclopia or hypertelorism
what part of the neural tube forms the ventricular system?
the lumen of the neural tube
what congenital defects are associated with ventricular malformation?
hydrocephalus due to atresia of cerebral aqueduct or Dandy-Walker syndrome in which there is an obstruction of the openings of the fourth ventricle.
What are the ventricular and marginal zones associated with CNS neuronal development? Where and how do the developing neurons migrate after their association with these zones?
ventricular is area that gives rise to the ectodermal neuroblastic cells that will form the neurons. Marginal is area along pia without neurons. Then migrate to the intermediate zone between the ventricular and marginal zones via radial glia, and once they reach this position they form dendrites and an axon with a growth cone.
describe the development of glial cells in the CNS.
originate from the glioblastic cells of the lumen of the neural tube. Three main lines: type 1 astrocyte progenitors, oligodendrocyte/type 2 astrocyte precursor, and radial glia progenitor cells. Note that radial glia progenitors serve as gilial guides before becoming astrocytes, ependymal cells, and muller cells. Microglia are derived from monocytes.
describe the development of the spinal cord.
neuroblasts migrate to form 2 pairs of plates: the alar plates give rise to the dorsal horns and the basal plates to the ventral horns. They are seperated by a sulcus limitans and the intermediate zone gives rise to the lateral horn.
describe the development of the brainstem.
alar and basal plates exist here as in the cord, but opening of 4th ventricle and formation of cerebellum results in dorsolateral rotation of the plates such that the basal plate is medial and gives rise to CN motor nuclei and the alar plate to the lateral CN sensory nuclei. The plates are seperated by the sulcus limitans
what does the cerebellum arise from and what do its two fissures seperate?
arises from the rhombic lip (part of alar plate structure that forms part of wall of 4th ventricle). primary fissure divides corpus cerebelli into the anterior and posterior lobes while the posterolateral fissure divides the plate into floculonodular lobe and the corpus cerebelli
describe the neuroblast migration that forms the cerebral cortex.
the first migrations take up the ventricular zone, but then succesive migrations force their way into the intermediate zone where most of the cortex is formed.
an infant who suffers significant cortical injury may show functional recovery ending up with few or no defects. why?
developing neurons exhibit plasticity (constant remodelling)