W10 L 83
Microcephaly
abnormally small head
Hydrocephalus
accumulation of fluid in the spaces of the brain
Placodes
areas of ectoderm found located at developing special sense organs on embryo Rounded areas of specialized thickened ectoderm found at the location of developing special sense organs Areas of ectoderm found at location of developing special sense organs on the embryo
Pharyngeal membranes
ectoderm of the grooves on the outside of pharyngeal wall make contact with the endoderm of the pouches on the inside to form the pharyngeal membranes. The first membrane gives rise to the tympanic membrane of the ear. All the other membranes disappear points of contact of ectoderm and endoderm between pharyngeal clefts areas between arches where the ectoderm and endoderm meet
Cleft 1
external auditory meatus
Frontonasal prominence: forms
forehead bridge of nose medial & lateral nasal prominences
pharyngeal pouches
paired structures in the throat region small outpockets of the anterior digestive tract in developing chordates, the paired openings found in the area between the mouth and digestive tube
pouch 2
palatine tonsil
CN IX is associated with _________________
special visceral efferent only
thyroglossal duct
the embryonic duct that is located from the base of the tongue to the midportion of the anterior neck\ •The thyroglossal duct degenerates and the opening of the tyroglossal duct persist as a small pit on the tongue as the foramen cecum.
Craniosynostosis
the premature fusing of the skull bones
otic placode what nerve
thickening of ectoderm on each side of the hindbrain from which the otic vesicle and subsequently the membranous labyrinth of the inner ear develop •The otic placode will form the vestibular and cochlear parts of the ear.
pouch 1
tympanic cavity and auditory tube
Membrane 1
tympanic membrane
Branchiomeric cranial nerves (SVE):
•): V, VII, IX, X provide motor innervation to muscles formed from somitomeres that form arches. So knowing which muscles form from each arch will let you know which muscles these cranial nerves innervate.
anterior 2/3 of tongue posterior 1/3 of the tongue.
•Arch 1 forms mucosa of anterior 2/3 of the tongue. Arch 3 and 4 form mucosa of posterior 1/3 of the tongue •Arch 2 is overgrown by arch 3 but provides taste innervation to anterior 2/3.
: from downgrowth of floor of diencephalon (neurohypophyseal bud).
•Both anterior and posterior lobes are ectodermal in origin because diencephalon is ectoderm-derived.
from upgrowth of ectodermal roof of the mouth (hypophyseal pouch).
•Both anterior and posterior lobes are ectodermal in origin because diencephalon is ectoderm-derived.
: (intra)membranous bone to the sides and tops of braincase; forms the calvaria •frontal, occipital, parietal
•Chondrocranium (cartilaginous part of the neurocranium): forms the base of the neurocranium and most of occipital bone. •Desmocranium: forms the calvaria = skull cap, which includes the superior portion of occipital. •Viscerocranium: these bones that make up the face and are derived from neural crest cells (discussed at the end ot the presentation). •
: derived from pharyngeal arches via membranous ossification. •temporal (squamous part), maxilla, zygomatic, mandible
•Chondrocranium (cartilaginous part of the neurocranium): forms the base of the neurocranium and most of occipital bone. •Desmocranium: forms the calvaria = skull cap, which includes the superior portion of occipital. •Viscerocranium: these bones that make up the face and are derived from neural crest cells (discussed at the end ot the presentation). •
: endochondral cranial base that later ossifies •occipital, sphenoid, ethmoid, temporal (petrous part)
•Chondrocranium (cartilaginous part of the neurocranium): forms the base of the neurocranium and most of occipital bone. •Desmocranium: forms the calvaria = skull cap, which includes the superior portion of occipital. •Viscerocranium: these bones that make up the face and are derived from neural crest cells (discussed at the end ot the presentation). •
•Ectoderm-derived but forms secondary mesenchyme (mesectoderm) to form "mesoderm"-derived structures. •Migrates all over the body to turn into cartilage and bone, teeth, skin, melanocytes, smooth muscles, glands, adipose tissue, neurons, glia, adrenal medulla, etc. •Responsible for most of the connective and skeletal tissue of the head, nerves, and pigment cells
•Posterior skull is mostly from primary mesoderm (not NCC-derived mesectoderm). •Muscles in the head and neck come from primary mesenchyme/mesoderm, so not NCC-derived but interacts with NCC in the sense that NCC guide the migration and formation of the cranial and cervical muscles in their proper location. •In the eye: NCC are implicated in the formation of the choroids, sphincter pupillae muscle, dilator pupillae muscle, ciliary muscle
Tensor tympani- Tensor veli palatini
-the muscle attached to the malleus; tensing the tensor tympani decreases vibration •Tensor tympani: pulls on the malleus to tighten the eardrum to dampen oscillation, which may help us discriminate sounds better (not completely known). •Tensor veli palatini: tightens soft palate together with its elevation so that food doesn't not go into nasopharynx. Pharyngeal Arch 1: "Mandibular"
•Thyroid originates from a single outpouching of endoderm on the ventral side between arch ______________. This is called thyroid diverticulum (outpocketing) or primordium.
1 and 2 in the primordial pharynx
•In early stage embryos, arteries are highly segmented according to the arches but arches ____________ disappear and change shape so the segmented configuration is not obvious by late fetus.
1, 2, and 5 mostly
Each pharyngeal arch has 4 derivative structures:
1.Bone & Cartilage 2.Artery 3.Nerve 4.Muscle (from mesoderm)
A toddler has a hearing defect. MRI scans show that the toddler has developmental defects in the auditory (Eustachian) tube and tympanic cavity. Which pharyngeal apparatus component mostly likely developed abnormally? A.Pharyngeal Arch 1 ("Mandibular" arch) B.Pharyngeal Pouch 1 C.Pharyngeal Cleft 1 D.Pharyngeal Arch 2 ("Hyoid" arch) E.Pharyngeal Pouch 2 ●
Answer: B, pharyngeal pouch 1 which form the tympanic cavity and Eustachian tube.
A six-year-old girl exhibits a swelling in the anterior part of her neck, just inferior to the hyoid bone. Which of the following may explain the swelling? A.intact cervical sinus B.obliteration of the cervical sinus C.intact thyroglossal duct D.obliteration of thyroglossal duct E.incomplete closure of palatine raphe ●
Answer: C, which is associated with thyroglossal duct cyst. If the swelling or opening was associated with lateral part of the neck, then it suggests that A is the correct answer due to branchial fistula.
Pharyngeal Arch 3
CN IX, Stylopharyngeus muscle, greater horn of the hyoid Skeletal Derivatives: Greater horn & Lower body of hyoid Muscular Derivatives: Stylopharyngeus Innervated by CN IX (glossopharyngeal)
Pharyngeal Arch 1
CN V, mandible, malleus and incus, muscles of mastication Skeletal Derivatives: Malleus, Incus, Mandible Muscles: Mastication muscles, ant. belly digastric, mylohyoid, tensor tympani, tensor veli palatini Innervated by CN V3
Pharyngeal Arch 2
CN VII, stapes and lesser horn of the hyoid; facial muscles and stapedius Skeletal Derivatives: Stapes, Styloid Process, Lesser horn/upper body of hyoid Muscular Derivatives: Stapedius, Facial Expression muscles, Posterior belly of digastric, stylohyoid Innervated by CN VII
Pouch 3
CRAINIAL PART Inferior parathyroid glands and the CAUDAL PART thymus
Pouch 4
CRANIAL PART superior parathyroid glands, CAUDAL parafollicular cells of thyroid gland
malleus, incus IN OTHER ANIMALS
Evolution of the middle ear ossicles malleus, incus evolved from jaw bones!
nasal placodes what nerve
Form in the anterior part of the frontonasal process, just superior to the stomodeum, during the fourth week. develop at the lateral margin of the frontonasal process and develop into the nose and the center of the upper jaw and lip Placodes that develop into olfactory organ for the sensation of smell located in mature nose •The nasal placode will form the mucosa of the cartilaginous nasal capsule that enclose the nasal cavity (essentially the nasal cavity).
Facial Primordia
Forms around the stomodeum 1 - frontonasal prominince - forehead and nose to mouth 2 - maxillary prominences - lateral mouth x2 3 - Mandivular - caudal mouth x 2
•. CN III, IV, and VI contain_________ because extra-ocular muscles are considered skeletal muscles, not SVE because extra-ocular muscles are not part of the pharyngeal arches (as seen in the image on the slide).
GSE fibers
•glands (except for parotid gland) & mucosae: interacts with neural crest cells.
Glands include thyroid gland, submandibular, sublingual glands (not parotid which forms from ectodermal patch in the inner cheek of the stomodeum).
pharyngeal clefts
In chordate embryos, one of the grooves that separate a series of arches along the outer surface of the pharynx and may develop into a pharyngeal slit. grooves in the pharynx that develop into slits that open to the outside of the body In chordate embryos, grooves that separate a series of pouches along the sides of the pharynx and may develop into pharyngeal slits.
Somitomeres
Organized whorls of cells within paraxial mesoderm that serve as precursors to somites.
Branchial Fistula
Persistence of 2nd groove AND 2nd pouch -Maintenance of communication between the non-obliterated sinus & the outside of neck - usually at level of thyroid gland
Pharyngeal ARCH 6
Recurrent branch of CN X Pulmonary arteries
stomodeum is
The embryonic invagination that becomes the oral cavity
Pyramidal Lobe
a normal variant of the thyroid gland in which there is a superior extension of the isthmus
Thyroglossal Duct Cyst
a palpable cystic midline mass in the neck due to incomplete closure of the thyroglossal duct. •When cyst bursts to external environment, then becomes a sinus. •Thyroglossal duct cyst = cyst in the midline of the neck from incomplete closure of thyroglossal duct. •Painless cysts progressively swell and are typically observed by age 5. If infected, could perforate the skin to form a sinus. May contain thyroid tissue (ectopic thyroid gland). •Occurs most commonly just below the hyoid bone. As the cyst gets larger, it becomes more prone to infection. •Sometimes, the cyst ruptures, creating a sinus as a result of an infection in the cyst.
lens placode what nerve
a thickening of the skin ectoderm lying over the optic vesicle that will invaginate to form the lens of the eye thickening of surface ectoderm that invaginates to form the lens vesicle •The lens placode will form the lens of the eye. The actual eye forms from evagination of the wall of the brain (neuroectoderm). Optic vesicle forms an optic cup (forms the retina, iris, and ciliary body) and optic stalk (forms optic nerve).
Pharyngeal arches
1: Mastication/Jaw, 2: Facial nerve, 3: Glossopharyngeal like taste, 4 and 6: Pharynx/Palate
pharyngeal (branchial) arches
Main components that form head and neck
Pharyngeal Arch 4
NERVE: superior laryngeal nerve from vagus MUSCLES: cricothyroid, LEVATOR VELI PALATINE, pharyngeal constrictors BONE: laryngeal cartilages Thyroid Cricoid Arytenoid Corniculate cuneiform ARTERY: Left: arch of the aorta from the left common the subclavian Right: proximal portion of the right subclavian
Ultimobranchial bodies give rise to
•parafollicular (aka C cells) in the thyroid gland that secrete calcitonin. Calcitonin acts to reduce calcium in blood, countering the effects of parathyroid hormone.
