Pharyngeal Arch Development (Exam 1) Flashcards
What are the anatomical boundaries of the adult head?
Head: Extends from the top of the skull to lower jaw
What are the anatomical boundaries of the adult neck?
Extends from inferior border of the jaw to the clavicle and sternum
What is the Frontonasal Process (FN)?
Anatomical boundary: Midline region which includes; forehead, nose, and philtrum of lip
Develops as functional unit along with the pharyngeal arch region to form the face
What is the Pharyngeal/Breachial arch (PA) region?
Anatomical boundary: Extends from the upper and lower jaws down to level of the cricoid cartilage (C6)
What is the Oropharyngeal Region?
The Oropharyngeal region is formed by the Pharyngeal arch region. It includes:
- upper/lower jaw
- Palate
- Oral cavity
- Pharynx/Larynx (to the vertebral level of c6)
Describe the Pharyngeal arches
Initially there are 6 pharyngeal arches that from in a cranial to caudal sequence. However the 5th arch degenerates, leaving only 1, 2, 3, 4, and 6.
Note: 4 Bilateral arches are visible on surface of the embryo; 4th merges with 6th
Each arch is a proliferation of tissue located bilaterally in region of jaw or neck
The Maxillary and mandibular processes are located in which arch?
Pharyngeal arch 1
What forms the Orofacial Region?
the Orofacial region is formed from Pharyngeal arches 1 (bilateral maxillary and mandibular processes) and single frontonasal process
This region is composed of the Face (includes the forehead, nose, cheeks, palate, jaws, and lips) and the Oral Cavity Proper
What is the Oral cavity Proper?
Boundary of oral cavity formed by PA1 and FN Process. Developmentally the future oral cavity is known as Stomodeum– lined with ectoderm
Which arches form the future pharyngeal/laryngeal region?
2, 3, 4, and 6
Describe the Pharynx:
A muscular tube that extends from base of skull to the cricoid cartilage C6. Tube is supported by bone, cartilage, CT and divided into 3 regions:
- Nasopharynx,
- Oropharynx,
- Laryngopharynx/hypopharynx
What are the Adult derivatives of pharyngeal arches?
Blood vessels, Facial bones of skull, cartilage, CT, Skeletal muscle of jaws, Face, Palate, lips and neck, mucosa covering the oral cavity, tongue, cheek, lips, thyroid salivary glad
What are Adult derivatives?
Check
Accessory Glands that develop from epithelium derived from endoderm. Endoderm lines pharynx and forms outpocketings (pouches) of wall: Pouch derivates include thymus, tonsils parathyroid
Head/Pharyngeal (Brachiomeric) Mesoderm:
mixture of mainly paraxial+some lateral plate in region near heart
Ectomesenchym germ layer
Mixture of neural crest+ Mesoderm derived tissue
Describe the structural arrangement of each arch:
Externally: Ectodermal lines outside surface and cleft/groove that separates each arch
Internally: Endodermal lines pharyngeal tube and lines pouches that separate each arch * each push sits opposite the corresponding cleft
Central Core: Mesoderm and ectomesenchyme
The central core of each arch contains a specific:
- Artery (Lateral Plate
- Carilage/CT/and/or bones
(Ectomesenchyme= NC+ Mesoderm) - Skeletal Muscle group ( Head/ Branchiomeric mesoderm-considered paraxial)
- Cranial Nerve (Carries both motor and sensory nerves– Neurons= Neuroectoder min CNS and Neural crest ganglia respectively)
Ectoderm lines the?
Stomodeum/ oral cavity proper
Endoderm lines the?
Pharynx and Gut tube
What is the boundary between Ectoderm and Endoderm called?
The oropharyngeal membrane
Every arch has:
Ectoderm and Cleft;
Ectoderm covers the external surface of each arch; lies external to the ectomesenchyme/mesoderm structures
Lines cleft (surface invaginination of ectoderm between each arch)
Adult derivative of external surface (Ectoderm) of pharyngeal arches:
Forms epidermis of jaw, and neck; part epithelial lining oral cavity, and dorsal surface of tongue
Describe the Internal surface of pharyngeal arches:
Made up of Endoderm:
- lines the internal surface of the pharynx
- lines the pharyngeal pouches ( Pouches are out-pocketing from the pharyngeal tube lined with endodermal tissue– Pouches are located between each pharyngeal arch)
Adult derivates of the internal surface of pharyngeal arches:
Epithelial lining of walls of pharynx; floor of mouth, ventral portion of tongue, thyroid gland, sublingual and submandibular glands, some minor salivary glands
Adult derivatives of pouches:
Endoderm of pouches contributes to epithelium of auditory tube, palatine tonsils, thymus, parathyroid
Describe the Central portion of pharyngeal arches (Describe Ectomesenchyme):
Ectomesenchyme: Neural crest cells mixed with mesoderm
- Forms part of the central core (middle layer) of arch; arises from neural crest cells that migrate into region of each arch to form ectomesencyme
- Adult derivatives: Forms bone/cartilage/CT of jaw and neck region for arches 1-3*
- Forms CT supporting the thyroid, tonsil, thymus and parathyroid glands
- Each arch has specific ectomesenchyme derivatives
Describe the Lateral Plate of the Central portion of the pharyngeal arches:
Forms all blood vessel: branches come off aortic arch, subclavian and common carotid-> external and internal
Adult Structures:
1st: Maxillary Art– Br off external carotid
2nd: Stapedial Art: Very small
3rd: Common carotid Art
4th: Subclavian; Aortic arch
6th: Pulmonary trunk
*Note: Neural crest cells migrating to region of the 6th PA contribute to formation and separation of aorta and pulmonary trunks
Forms CT/Cartilage of laryngeal region: corresponds to region of arches 4 and 6 (I.e thyroid and laryngeal cartilages)
What is the Head Pharyngeal Mesoderm?
It forms past of the central core (middle layer); Arises from migration of cranial/head mesoderm into region
What are the adult derivatives of Head pharyngeal mesoderm?
All skeletal muscle of face, jaw, palate, pharynx, and larynx *excludes tongue muscles– tongue muscles are from somites behind head (paraxial mesoderm)
Describe the first arch related to Cranial head mesoderm.
Muscles of Mastication: Temporalis, Masseter, Lateral Pterygoid, Medial Pterygoid. (All bilateral).
Plus: Mylohoid, Anterior belly of digastric; tensor tympani, tensor vela palatini
Describe the 2nd arch related to Cranial head mesoderm.
Muscles of facial expression: (Orbicularis iris, orbiculares oculi; rigorous, platysma, buccinator; auricular, front-occipitalis, platysma, etc)
Plus: Stapedus, Stylohoid muscle; posterior belly of digastric
Describe the 3rd arch related to Cranial head mesoderm.
The Stylopharyngeus muscle
Describe the 4th arch related to Cranial head mesoderm.
Palatal and Pharyngeal muscles: Have palatal, pharyngeal or uvula in name
Superior middle inferior pharyngeal constrictors, salpingopharyngeus, palatopharyngeus, palatoglossus, cricothyroid, levator veli palatini, musculus uvulae
Describe the 6th arch related to Cranial head mesoderm.
Intrinsic laryngeal muscles: Have arytenoid or vocal in name
posterior cricoarytenoid, lateral cricoarytenoid, transverse and oblique arytenoid, thyroarytenoid, vocalist
Name the Cranial nerves that innervate each arch
PA 1 = Trigeminal (CN V)- (V2 and V3 only)
PA2= Facial N (CN VII)
PA 3= Glossopharyngeal (CN IX)
PA 4/6= Vagus (CN X)
Describe the Cranial nerve that innervates the 1st Arch
The Trigeminal CN (V): Has three divisions; Mandibular (V3), Maxillary (V2), Ophthalmic (V1), (FN region).
V2: (GSA) supplies sensory mucosa for entire palate; small sensory contribution to nose/maxillary sinus
V3: (SVE):
Motor (voluntary)(SVE): Mandibular(V3)
SVE motor neurons located in CNS
GSA (Pain, temp, touch): Mandibular division and maxillary division (V2). Carries these sensations to the face, jaw, teeth and to mucosa of palate, some nose, oral cavity, TMJ, mucosa ant 2/3 tongue, floor of mouth– sensory neurons in ganglia
NO SVA/ NO GVE
Describe the Cranial nerve that innervates the 2nd Arch
The Facial N (CN VII)
Motor (voluntary): Has several named branches. SVE motor neurons located in CNS
GSA: (Sensory branch) carries pain, temp touch to small area behind ear
Sensory neurons in ganglion= GENICULATE GANGION
SVA (Taste): Facial N- Chorda tympani br. carries taste ant 2/3 tongue and palate
special sensory neurons in ganglion
GVE (autonomic (visceral motor) parasympathetic): (autonomic br) carries parasympathetic fibers to lacrimal, submandibular, sublingual glands, nasal, palatal SALIVARY GLANDS Pre-ganglionic neurons in CNS Post-ganglionic neurons - Pterygopalatine ganglion -Submandibular ganglion
Describe the Cranial nerve that innervates the 3rd Arch
The Glossopharyngeal (CN IX):
SVE: Provides motor to one pharyngeal arch muscle— Stylopharyngeus
SVE motor neurons in CNS
GSA: Carries pain, temp, touch to posterior 1/3 of tongue, oropharynx— GAG reflex
Somatic generals sensory neurons form ganglion
SVA: Taste to post 1/3 of tongue
Special sensory neurons in ganglion
GVE: Carries parasympathetic fibers to parotid gland
Preganglionic neurons in CNS
Post ganglionic neurons
- Otic ganglion
Describe the Cranial nerve that innervates the 4th Arch
Vagus CN (X)- 2 Major branches associated with PA 4th
SVE: Motor branches form a plexus. It provides innervation to Palatoglossus and majority of palatal, pharyngeal and constrictor muscles. Provides motor innervation to cricothyroid muscle
GSA: Sensory branches carries sensation to root/base of tongue/epiglottis. innervates mucosa in larynx above vocal folds.
SVA: Taste branch. Carries taste to root/base of tongue/epiglottis
GVE: Vagus autonomics branch carries parasympathetic fibers to glands of pharynx and larynx. Post-ganglionic neurons in ganglia found in wall of organs
Describe the Cranial nerve that innervates the 6th Arch
Vagus (CNX): 1 Major branch associated.
SVE: Motor branch provides motor to laryngeal muscles
GSA: Sensory br. Larynx. Carries sensation to mucosa in larynx. Region below vocal folds
SVA: NONE
GVE: Vagus autonomic br. carries parasympathetic fivers to glands of larynx. Post ganglionic neurons in ganglia found in wall of organs
Describe the ectodermal clefts and pouches:
Every arch has a cleft and a pouch; cleft and pouch are located opposite each other and a membrane lies between the two structures.
Ectodermal clefts of 2,3,4 become obliterated as the muscles of pro-pharynx proliferate and the 2nd arch overgrows the region of 3, and 4. This proliferative event is regulated by cell signaling
Ectodermal cleft of arch 1 normally forms the EXTERNAL AUDIOTRY MEATUS OF EAR– only cleft to persist in adult
Describe the Endodermal pouches:
Between arch 1 and 2: Pharyngotympanic tube (auditory) (eustachian tube); and Middle ear (tympanic) cavity
Between arch 2 and 3: from epithelial (SSNK) covering surface of palatine tonsil and lining palatine tonsillar fossa: (Palatine tonsil and fossa doesn’t migrate)
Between arch 3 and 4: It’s divided into dorsal and ventral portions. Forms epithelial reticular cells of thymus (ventral part); and the epithelial cells (Chief/Oxyphil) of inferior parathyroid (dorsal part)
* The thymus and inferior parathyroid migrate together to their final adult position– thymus to the mediastinum; inferior parathyroid at inferior pole on posterior surface of parathyroid gland
Between arch 4 and 6: It’s divided into dorsal and ventral portions: Forms Chief/oxyphil cells of superior parathyroid (dorsal Part)
* Neural crest cells invade (ventral part of 4th and 6th) to form parafollicular cells that will become incorporated into thyroid gland.
ventral part forms ultimobranchial body
What is the tissue between the cleft and pouch; forms the tympanic membrane called?
The Pharyngeal membrane
Embryonic precursor for Malleus
Meckel’s Cartilage
Embryonic precursor for Incus
Paleto-pterygoquadrate
Malleus, Incus and inferior concha all:
undergo endochondral ossification and are from the 1st PA
PA 1 is the only PA that has:
Pouch and Cleft
What supplies the frontonasal region:
V1
What is the artery associated with PA 2?
Stapedial
What is the artery associated with PA 2?
Maxillary
What is the artery associated with PA 3?
Common and internal carotid
What is the artery associated with PA 4?
Subclavian and aorta
Which PA’s have lateral plate germ layer
4 & 6
Neural crest derived pouch cells come from which PA:
6th Pouch (Ventral 4th)
- Parafollicular cells
What is the pouch derivative of PA 4?
Superior parathyroid (Doesn’t migrate)
