Pharyngeal Arch Development (Exam 1)

Question 1

What are the anatomical boundaries of the adult head?

Answer 1

Head: Extends from the top of the skull to lower jaw

Question 2

What are the anatomical boundaries of the adult neck?

Answer 2

Extends from inferior border of the jaw to the clavicle and sternum

Question 3

What is the Frontonasal Process (FN)?

Answer 3

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

Question 4

What is the Pharyngeal/Breachial arch (PA) region?

Answer 4

Anatomical boundary: Extends from the upper and lower jaws down to level of the cricoid cartilage (C6)

Question 5

What is the Oropharyngeal Region?

Answer 5

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)

Question 6

Describe the Pharyngeal arches

Answer 6

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

Question 7

The Maxillary and mandibular processes are located in which arch?

Answer 7

Pharyngeal arch 1

Question 8

What forms the Orofacial Region?

Answer 8

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

Question 9

What is the Oral cavity Proper?

Answer 9

Boundary of oral cavity formed by PA1 and FN Process. Developmentally the future oral cavity is known as Stomodeum– lined with ectoderm

Question 10

Which arches form the future pharyngeal/laryngeal region?

Answer 10

2, 3, 4, and 6

Question 11

Describe the Pharynx:

Answer 11

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

Question 12

What are the Adult derivatives of pharyngeal arches?

Answer 12

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

Question 13

What are Adult derivatives?

Check

Answer 13

Accessory Glands that develop from epithelium derived from endoderm. Endoderm lines pharynx and forms outpocketings (pouches) of wall: Pouch derivates include thymus, tonsils parathyroid

Question 14

Head/Pharyngeal (Brachiomeric) Mesoderm:

Answer 14

mixture of mainly paraxial+some lateral plate in region near heart

Question 15

Ectomesenchym germ layer

Answer 15

Mixture of neural crest+ Mesoderm derived tissue

Question 16

Describe the structural arrangement of each arch:

Answer 16

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

Question 17

The central core of each arch contains a specific:

Answer 17

• 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)

Question 18

Ectoderm lines the?

Answer 18

Stomodeum/ oral cavity proper

Question 19

Endoderm lines the?

Answer 19

Pharynx and Gut tube

Question 20

What is the boundary between Ectoderm and Endoderm called?

Answer 20

The oropharyngeal membrane

Question 21

Every arch has:

Answer 21

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)

Question 22

Adult derivative of external surface (Ectoderm) of pharyngeal arches:

Answer 22

Forms epidermis of jaw, and neck; part epithelial lining oral cavity, and dorsal surface of tongue

Question 23

Describe the Internal surface of pharyngeal arches:

Answer 23

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)

Question 24

Adult derivates of the internal surface of pharyngeal arches:

Answer 24

Epithelial lining of walls of pharynx; floor of mouth, ventral portion of tongue, thyroid gland, sublingual and submandibular glands, some minor salivary glands

Question 25

Adult derivatives of pouches:

Answer 25

Endoderm of pouches contributes to epithelium of auditory tube, palatine tonsils, thymus, parathyroid

Question 26

Describe the Central portion of pharyngeal arches (Describe Ectomesenchyme):

Answer 26

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

Question 27

Describe the Lateral Plate of the Central portion of the pharyngeal arches:

Answer 27

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)

Question 28

What is the Head Pharyngeal Mesoderm?

Answer 28

It forms past of the central core (middle layer); Arises from migration of cranial/head mesoderm into region

Question 29

What are the adult derivatives of Head pharyngeal mesoderm?

Answer 29

All skeletal muscle of face, jaw, palate, pharynx, and larynx *excludes tongue muscles-- tongue muscles are from somites behind head (paraxial mesoderm)

Question 30

Describe the first arch related to Cranial head mesoderm.

Answer 30

Muscles of Mastication: Temporalis, Masseter, Lateral Pterygoid, Medial Pterygoid. (All bilateral). Plus: Mylohoid, Anterior belly of digastric; tensor tympani, tensor vela palatini

Question 31

Describe the 2nd arch related to Cranial head mesoderm.

Answer 31

Muscles of facial expression: (Orbicularis iris, orbiculares oculi; rigorous, platysma, buccinator; auricular, front-occipitalis, platysma, etc) Plus: Stapedus, Stylohoid muscle; posterior belly of digastric

Question 32

Describe the 3rd arch related to Cranial head mesoderm.

Answer 32

The Stylopharyngeus muscle

Question 33

Describe the 4th arch related to Cranial head mesoderm.

Answer 33

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

Question 34

Describe the 6th arch related to Cranial head mesoderm.

Answer 34

Intrinsic laryngeal muscles: Have arytenoid or vocal in name | posterior cricoarytenoid, lateral cricoarytenoid, transverse and oblique arytenoid, thyroarytenoid, vocalist

Question 35

Name the Cranial nerves that innervate each arch

Answer 35

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)

Question 36

Describe the Cranial nerve that innervates the 1st Arch

Answer 36

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

Question 37

Describe the Cranial nerve that innervates the 2nd Arch

Answer 37

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 ```

Question 38

Describe the Cranial nerve that innervates the 3rd Arch

Answer 38

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

Question 39

Describe the Cranial nerve that innervates the 4th Arch

Answer 39

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

Question 40

Describe the Cranial nerve that innervates the 6th Arch

Answer 40

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

Question 41

Describe the ectodermal clefts and pouches:

Answer 41

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

Question 42

Describe the Endodermal pouches:

Answer 42

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

Question 43

What is the tissue between the cleft and pouch; forms the tympanic membrane called?

Answer 43

The Pharyngeal membrane

Question 44

Embryonic precursor for Malleus

Answer 44

Meckel's Cartilage

Question 45

Embryonic precursor for Incus

Answer 45

Paleto-pterygoquadrate

Question 46

Malleus, Incus and inferior concha all:

Answer 46

undergo endochondral ossification and are from the 1st PA

Question 47

PA 1 is the only PA that has:

Answer 47

Pouch and Cleft

Question 48

What supplies the frontonasal region:

Answer 48

V1

Question 49

What is the artery associated with PA 2?

Answer 49

Stapedial

Question 50

What is the artery associated with PA 2?

Answer 50

Maxillary

Question 51

What is the artery associated with PA 3?

Answer 51

Common and internal carotid

Question 52

What is the artery associated with PA 4?

Answer 52

Subclavian and aorta

Question 53

Which PA's have lateral plate germ layer

Answer 53

4 & 6

Question 54

Neural crest derived pouch cells come from which PA:

Answer 54

6th Pouch (Ventral 4th) - Parafollicular cells

Question 55

What is the pouch derivative of PA 4?

Answer 55

Superior parathyroid (Doesn't migrate)