Face, Development, and Pharyngeal Arches Flashcards
What cell type are the cartilage elements of pharyngeal arches 1,2, and 3 made of?
Neural crest cells of the mid and hind brain
What cell type are the cartilage elements of pharyngeal arches 4 and 6 made of?
Lateral plate mesoderm
All bones that are derived from pharyngeal cartilages are formed by___________.
Endochondral formation
What are the names of the cartilages that are derived from the 1st pharyngeal arche?
-meckel’s cartilage
What cartillage arises from the mandibular swelling?
Meckel’s cartilage
What is the name of the cartilage of the second arche?
Reichert’s cartilage
The laryngeal cartilages are derived from which pharyngeal arch(es)?
Arches 4 and 6
The laryngeal cartilages consists of which 5 cartilages?
- *-thyroid cartilage
- cricoid cartilage**
- arytenoid cartilage
- corniculate cartilage
- cuneiform cartilage
What cell type are the laryngeal cartilages of arches 4 and 6 derived from?
Lateral plate mesoderm
What bones arise from the first pharyngeal arche?
- incus
- malleus
- Alisphenoid
- premaxilla
- maxilla
- zygomatic bone
- Squamous part of temporal bone
Which bones are derived from meckel’s cartilage?
Incus and malleus
What bones arise from the second pharyngeal arche?
- stapes
- lesser horn of the hyoid bone
- upper portion of the body of the hyoid bone
What bones arise from the 3rd pharyngeal arche?
- lower portion of body of the hyoid bone
- greater horn of the hyoid bone
What bones arise from the 4 and 6th pharyngeal arche?
None
TRICK QUESTION
What are the rest of the facial bones formed from and how are they formed?
- neural crest cells
- intramembranous ossification
The anterior ligament of the malleus and the sphenomandibular ligament are derived from which arche?
Arch 1
The stylohyoid ligament is derived from which arche?
Arch 2
What nerve innervates the 1st pharyngeal arche?
CNV- Trigeminal N. (maxillary and mandibular division)
What nerve innervates the 2nd pharyngeal arche?
CNVII-facial N.
What nerve innervates the 3rd pharyngeal arche?
CNIX- Glossopharyngeal nerve
What nerve innervates the 4th and 6th pharyngeal arche?
CNX-Vagus N/ CN XI-Accessory n.
What tissue are the muscles of the pharyngeal arches mainly derived from?
Paraxial mesoderm derived from cranial somitomere and occipital somites
What muscles are derived from the first pharyngeal arche?
- Muscles of mastication
- mylohyoid mm.
- anterior belly of the digastric mm.
- tensor tympani mm.
- tensor veil palatini mm.
The muscles that are derived from the 1st pharyngeal arche come from which cranial somitomere?
4th cranial somitomere
What muscles are derived from the 2nd pharyngeal arche?
- muscles of facial expression
- posterior belly of the digastric mm.
- stylohyoid mm.
- stapedius mm.
The muscles that are derived from the 2nd pharyngeal arche come from which cranial somitomere?
6th cranial sometomere
What muscles are derived from the 3rd pharyngeal arche?
-stylopharyngeus mm.
The muscles that are derived from the 3rd pharyngeal arche come from which cranial somitomere?
7th somitomere
What muscles are derived from the 4th pharyngeal arche?
- cricothyroid mm
- Cricopharyngeus m.
The muscles that are derived from the 4th pharyngeal arche come from which occipital somites?
Occipital somites 2-4
What muscles are derived from the 6th pharyngeal arche?
- Laryngeal muscles (except cricothyroid- 4 arch)
- Skeletal muscles of esophagus
What tissue covers the exterior of the pharyngeal arches?
Ectodermal epithelium
What tissue is found within the pharyngeal arches?
Mesenchymal tissue
What tissue is found on the interior surface of the pharyngeal arches?
Endodermal epithelium
How many clefts are there in the embryo at week 5?
4 clefts
What happens to the first cleft during development?
-it moves towards the first pharyngeal pouch and becomes the external auditory meatus
What happens to the last three clefts during development?
- the 2nd cleft grows and then overlaps the 3rd and 4th cleft
- they form a cavity lined with ectodermal epithelium
- it holds the cervical sinus
How many pouches are seen in an embryo?
5 pouches
What happens to the 1st pouch during development?
-it joins the first cleft to form the external auditory meatus
What happens to the 2nd pouch during development?
- becomes obliterated
- what’s left of its epithelial lining will form buds with the surrounding mesenchyme
- these will become the palatine tonsils
What happens to the 3rd pouch during development?
- it will become the parathyroid glands and the thymus
What happens to the 4th pouch during development?
What happens to the 4th pouch during development?
What happens to the 5th pouch during development?
It will become the ultimobranchial body
T/F: There can be cervical cysts and fistulas formation within the 2nd, 3rd and 4th clefts as development progresses
True
What are the steps of the development of the thyroid gland?
-develops as an epithelial proliferation in the floor of the pharyngeal gut between the tuberculin impar and the copula(foramen cecum)
-this then forms a downgrowth known as the thyroid diverticula
-As the thyroid migrates it descends to different levels:
. Anterior to hyoid bone
. Anterior to trachea
How does the thyroid gland descend to its final position?
-descends through the thyroglossal canal
What tissue is the thyroid gland made from?
Endodermal lining of the pharynx
T/F: A cyst can develope within the thyroglossal duct that the thyroid gland used to descend to its normal position
True
How is the anterior 2/3rd of the tongue formed?
-proliferation of mesoderm forms a tuberculin impar and lateral lingual swelling which forms the anterior 2/3rd of the tongue
How is the root of the tongue formed?
-caudally, the copula from the 2nd arche and hypobranchial eminance from the 3rd and 4th arche form the root of the tongue
How is the epiglottis formed?
-formed from the 4th and 6th arches
Which nerve provides general sensory to the anterior 2/3rd of the tongue?
CNV3-Mandibular N.
Which nerve innervates the taste buds on the anterior 2/3rd of the tongue?
CNVII- Facial N. (chorda tympani)
Which nerve innervates the root of the tongue?
CNIX (glossopharyngeal)
Which nerve innervates the anterior of the epiglottis?
CNX- Vagus N.
Chart of branchial arch and what they derive
Branchial arche and its structures
Picture of muscles of branchial arches
Branchial arch and its structures
Fate of clefts and pouches
Mesenchyme for formation of head region is derived from
Paraxial mesoderm (somites/somitomeres), lateral plate mesoderm, neural crest, placodes
Muscles of mastication
Temporalis, masseter, and pterygoids
Mandibulofacial dysostosis AKA
Teacher Collin’s syndrome or FIRST ARCH SYNDROME
Mandibulofacial dysostosis
Autosomal dominant w/ variable penetrance - caused by lack of migration of neural crest into pharyngeal arch 1; produces various facial anomalies (deafness due to malformation of ossicles); normal intelligence but may be mistaken due to deafness
Muscles of hyoid arch
Stapedius, stylohyoid, posterior belly of digastric, auricular, and muscles of facial expression
Adult derivatives of pharyngeal pouch 1
Epithelial lining of auditory tube and middle ear cavity; tubotympanic recess (lateral/distal = tympanic/middle ear cavity; medial/proximal = auditory/eustachian tube)
Adult derivatives of pharyngeal pouch 2
Epithelial lining of palatine tonsils crypts (medial = tonsillar fossa, surface epi of palatine tonsil; lateral = degenerates)
Adult derivatives of pharyngeal pouch 3
Inferior parathyroid gland and thymus (dorsal = inf. parathyroid; ventral = thymus); things move caudally
Adult derivatives of pharyngeal pouch 4
Superior parathyroid gland, contribute to parafollicular cells of thyroid (dorsal = parathyroid; ventral = degenrates; ultimobranchial body = C-cells/parafollicular cells); things move caudally
