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103 Cards in this Set
- Front
- Back
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What is a head fold?
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It is the ventral "swing" of heart and oropharyngeal membrane
AND closure of foregut |
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How do neural crest cells form the branchial apparatus?
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- invade head and neck lateral to rostral foregut.
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The neural crest cells are the source of what?
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- ALL connective tissues including skeletal components
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What is the source of all skeletal muscle?
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Cephalic paraxial mesoderm
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How many branchial arches form?
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6 arches form
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Which arch is rudimentary?
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5th arch
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What is the first arch separated into?
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two prominences:
1. maxillary prominence (upper jaw) 2. mandibular prominence (lower jaw) |
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What does the first arch primarily form?
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the face
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What is the stomodeum?
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an ectodermal lined depression
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What separates the stomodeum and the foregut?
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Oropharyngeal membrane
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What does the stomodeum eventually form?
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Anterior 2/3 of oral cavity
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What will make the posterior 1/3 of oral cavity?
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Pharynx
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What are branchial grooves?
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FOUR external grooves separating each arch
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What are pharyngeal pouches?
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FOUR internal evaginations of endoderm separating each arch
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What is the branchial membrane?
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It is the meeting of ectoderm of branchial groove with endoderm of pharyngeal pouch
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What are the structural components of a typical branchial arch?
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1. ectodermal outer covering (epidermis)
2. Endodermal inner lining (mucosal) 3. Mesenchymal core (branchiomeric mesenchyme) |
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What makes up the mesenchymal core?
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1. blood vessels
2. cartilaginous bar 3. muscular component 4. cranial nerve |
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What are blood vessels in the mesenchymal core formed from?
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Endothelium of an aortic arch
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What are the cartilaginous bars in the mesenchymal core formed from?
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Neural crest cells
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What is the muscular component of the mesenchymal core formed from?
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cephalic paraxial mesoderm (somitomeres)
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How are cranial nerves formed?
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Cranial nerves follow neural crest cells & paraxial mesoderm
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What does the ectodermal epithelium of branchial groove 1 become?
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External acoustic canal (ear)
--> between arch 1&2 |
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What does the ectodermal epithelium of branchial groove 2&3 become?
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Forms cervical sinus and will regress
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What cartilage does the mandibular prominence of branchial arch 1 form?
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Meckel's cartilage
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What does the dorsal part of the mandibular prominence (branchial arch 1) form and how?
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Malleus and incus by ENDOCHONDRAL ossification
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What happens to the ventral part of the mandibular prominence?
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It regresses to form the mandible by INTRAMEMBRANEOUS ossification.
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What cartilage does branchial arch 2 form?
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Reichert's cartilage
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What does the branchial arch 2 form and how?
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stapes, styloid process, and upper 1/2 of hyoid bone by ENDOCHONDRAL ossification
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What does the branchial arch 3 form and how?
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lower 1/2 of hyoid bone by ENDOCHONDRAL ossification.
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What does branchial arches 4 & 6 form?
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cartilages of larynx except epiglottis
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What cranial nerves come out of branchial arch 1?
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maxillary and mandibular divisions of trigeminal nerve (CN V)
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What cranial nerve comes out of branchial arch 2?
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Facial nerve (CN VII)
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What cranial nerve comes out of branchial arch 3?
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glossopharyngeal nerve (CN IX)
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What cranial nerve comes out of branchial arches 4 & 6?
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superior and recurrent larygneal branches of vagus nerve (CN X)
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What are branchial muscles innervated by?
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efferent branches of cranial nerves to branchial arches
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What muscles come out of branchial arch 1?
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- Muscles of mastication
- mylohyoid - Anterior belly of digastric muscle - tensor tympani - tensor veli palatini |
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What nerve innervates muscles of branchial arch 1?
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mandibular division of trigeminal nerve (V)
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What muscles come out of branchial arch 2?
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- Muscles of facial expression
- Stylohyoid - Posterior belly of digastric muscle - Stapedius |
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What nerve innervates muscles of branchial arch 2?
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motor portion of facial n (VII)
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What muscles come out of branchial arch 3?
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stylopharyngeus
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What nerve innervates the stylopharyngeus of branchial arch 3?
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Glossopharyngeal nerve (IX)
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What muscles come out of branchial arch 4?
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- Cricothyroid
- levator veli palatini - constrictors of pharynx - palatoglossus |
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What nerve innervates the muscles of branchial arch 4?
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superior laryngeal branch of vagus (X)
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What muscles come from branchial arch 6?
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intrinsic muscles of larynx (vocalization)
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What nerve innervates the muscles of branchial arch 6?
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recurrent branch of vagus n. (X)
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What does pharyngeal pouch 1 form?
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Tubotympanic recess which will form the pharyngotympanic canal and cavity of middle ear
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What does the first branchial membrane form?
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Tympanic membrane
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What does pharyngeal pouch 2 form?
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epithelium of palatine tonsil and tonsilar crypts
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What does the dorsal portion of pharyngeal pouch 3 form?
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inferior parathyroid glands
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What does the ventral portion of pharyngeal pouch 3 form?
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eptihelial reticulum of thymus gland
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What does the dorsal portion of pharyngeal pouch 4 form?
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superior parathyroid glands
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What does the ventral portion of pharyngeal pouch 4 form?
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Ultimobranchial body
and associated neural crest cells form c-cells of thyroid gland. |
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What is the thyroid diverticulum?
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endodermal - lined evagination just caudal to median tongue bud; will move caudally
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How does the thyroid diverticulum stay in conatct with the foramen cecum?
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Thyroglossal duct
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What is the foramen cecum?
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proximal opening of thyroglossal duct
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What is the thyroglossal duct?
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duct that keeps communication between the thyroid and foramen cecum
during the descent of thyroid gland into neck |
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What are characteristics of thyroid gland?
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- midline structure
- most anterior structure ***Does NOT come from pharyngeal pouch |
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What are congenital malformations that are related to the thyroid gland?
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- thyroglossal duct cyst (can become infected)
- thyroglossal duct sinus (if cyst contacts surface) - ectopic thyroid gland |
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Why do congenital malformations of the thyroid gland occur?
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- Because the thyroglossal duct does not correctly regress, there are remnants of the duct along the path of migration of the thyroid.
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How does the ectopic thyroid gland occur?
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When the thyroid gland does not migrate caudally and remnants are left in the pathway.
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What are the types of ectopic thyroid glands?
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-lingual thyroid (fail to migrate at all)
-cervical thyroid (found in more cranial part of neck) -accessory thyroid |
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What are the different types of branchial malformations and what is their characteristic?
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branchial sinus, cyst (if infected), or fistula (opening to exterior; occassionally will open into pharynx)
- NOT midline |
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Why do branchial malformation occur?
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remnant of cervical sinus (branchial groove 2-4 does not regress)
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what is the most common congenital cause of a neck mass in children (20%)?
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Branchial cleft cysts
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What is the first arch syndrome?
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It is the malformations of the ear, mandible, zygoma, and palate.
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Why does the first arch syndrome form?
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Insufficient migration of neural crest cells into the first branchial arch.
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What is the DiGeorge Syndrome?
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Lack of parathyroid glands, thymus glands
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What physical abnormalities occur in DiGeorge Syndrome?
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Facial abnormalities: low-set ears, small mouth
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What defects are related to DiGeorge Syndrome?
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Defects in outflow tract of heart and great vessels
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What is the development of all the organs involved in DiGeorge Syndrome dependent on?
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Migration of neural crest cells to the region of pharyngeal pouches.
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Why is diGeorge Syndrome called CATCH-22?
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C = cardiac defects
A = abnormal face formation T C = cleft palate H = hypocalcemia (due to parathyroid involvement) 22 = involves mutations on chromosome 22 |
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What is Rathke's pouch (hypophysial diverticulum)?
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anterior lobe of pituitary gland (formed from the stomodeum)
- ectoderm-lined |
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What are the 5 facial primordia?
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1. frontonasal prominence
2. maxillary prominence (2) 3. mandibular prominence (2) |
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How are the 5 facial prominences formed?
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proliferation and migration of neural crest cells
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The neural crest cells are a major source for what kind of components in the face and oral regions?
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it is a major source of connnective tissue, including cartilage, bone, and ligaments in the face and oral regions
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What is nasal placodes (olfactory mucosa)?
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It is the thickening of nasal ectoderm on the frontonasal prominence.
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What will the nasal placodes form?
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They will evaginate to form the nasal pit.
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What will form around the nasal pits?
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medial and lateral nasal prominences
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What is the nasolacrimal groove?
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it forms between the lateral nasal prominence and the adjacent maxillary prominence
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What does the nasolacrimal groove become?
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nasolacrimal duct - drains tears from medial aspect of eye into nasal cavity (that's why when you cry, your nose runs)
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What is the intermaxillary segment formed by?
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It is formed by the fusion of paired medial nasal prominences?
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What does the intermaxillary segment eventually form (4)?
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1. philtrum of lip
2. fleshy nasal septum 3. premaxillary part of maxilla (upper jaw holds 4 incisors) 4. primary palate ***Forms internally into nasal cavity |
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What provides cutaneous sensory innervation to the frontonasal prominence?
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V1 - opthalmic division of trigeminal nerve
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What provides cutaneous sensory innervation to the maxillary prominence?
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V2 - maxillary division of trigeminal nerve
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What provides cutaneous sensory innervation to the mandibular prominence?
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V3 - mandibular division of trigeminal nerve
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what do nasal cavities develop from?
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Nasal pits and sacs - ectoderm-lined depressions
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What is the oronasal membrane?
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Originally separated the nasal and oral cavity, but eventually ruptures so that there is a continuity between the nasal and oral cavity.
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What does the primary palate form from?
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intermaxillary segment
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What does the secondary palate form as?
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paired shelves (lateral palatine processes) that lift from the maxillary prominences
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What two things fuse to form the secondary palate?
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1. paired lateral palatine processes
2. nasal septum |
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The palate separates the oral and nasal cavities, except in what region?
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The region of the pharynx
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what is the landmark between the primary and secondary palate?
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Incisive foramen
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What results from an anterior cleft malformation?
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cleft lip
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How does an anterior cleft malformation occur?
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incomplete fusion of maxillary prominence with medial nasal prominence
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What results from a posterior cleft malformation?
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cleft palate
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What causes a posterior cleft malformation?
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incomplete fusion of lateral palatine processes and nasal septum
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Cleft lip occurs more frequently in which sex?
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Males (80%)
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What factor correlates with an increased incidence of cleft lip?
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maternal age (slightly)
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Cleft lip occurs in 1 in how many births?
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1000
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Cleft palate occurs in 1 in how many people?
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2500
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What sex does cleft palate occur more frequently?
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Females (67%)
**palatal shelves fuse 1 week later in females than in males |
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What increases risk of cleft lip and cleft palate?
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anticonvulsant drugs during pregnancy
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What are the causes of cleft palate?
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- smallness of palatal shelves
- failure of shevles to elevate - inhibition of the fusion process itself - failure of the tongue to drop between the shelves because of microagnathia. |
