Embryology VI Flashcards
What 3 groups of mesoderm fall through the primative streak?
- Laterally Migrating Mesoderm
- Cardiogenic Mesoderm
- Pharyngeal Arch Mesoderm
What are the 3 subgroups of laterally migrating mesoderm?
- Paraxial
- Intermediate
- Lateral Plate Mesoderm
Explain were each of the following migrate after going through the primative streak.
- Laterally Migrating Mesoderm
- Cardiogenic Mesoderm
- Pharyngeal Arch Mesoderm
Laterally Migrating Mesoderm:
Laterally
Cardiogenic Mesoderm:
Most Cranial of all Mesoderms
(to the oropharyngeal membrane)
Pharyngeal Arch Mesoderm:
More caudal then cardiogenic mesoderm (stops short of the oropharyngeal membrane)
What are the 3 components of the pharyngeal apparatus?
- Pharyngeal arches (6)
- Pharyngeal Grooves (4)
* *covers OUTSIDE of the apparatus - Pharyngeal Pouches (4)
* *covers the INSIDE of the apparatus
What embryologic cell types are associated with:
- Pharyngeal Arches
- Pharyngeal Pouches
- Pharyngeal Grooves
Pharyngeal Arches:
Pharyngeal Arch Mesoderm
Pharyngeal Groove (Outer): Ectoderm
Pharyngeal Pouches (inner): Endoderm
T or F: neural crest cells migrate to the pharyngeal arches
True
What 3 components make up each of the pharyngeal arches?
- Arch Cartilage
- Aortic Arch
- Mesoderm the forms head and neck muscles (BE mesoderm)
*Cranial Nerves are also there but they are not derived from the arch
What is arch cartilage?
- what does it give rise to?
- Essential Cells?
- Pre-cartilagenous mesenchyme that gives rise to bone/cartilage/CT
**Migration of Neural Crest = essential to formation
T or F: the cranial nerve associated with each pharyngeal arch is derived from neural crest cells
False, it is derived from neuroectoderm
*Bones/cartilage/CT of pharyngeal arches depends on migration of neural crest cells
What are somites and what are they derived from?
- Mesodermal blocks on each side of the midline
- Mesoderm => Lateral Migrating Mesoderm => Paraxial (somite) Mesoderm
What are the most cranial somites that start to thin out?
- what do they give rise to?
- Occiptal Somites
Give rise to:
- SKELETAL muscles of the tongue
- 7 extraocular muscles
What type of innervation is supplied to occiptal somites and what nerves do this?
- GSE innervation (not BE because these don’t come from the pharyngeal arches)
- CN: 3, 4, 6, 12
Besides occipital somites, what gives rise to the skeletal muscles of the head?
- Pharyngeal Arches (from pharyngeal apparatus)
Nerve associated with each arch?
- V3 (mandibular n.)
- VII
- IX
4/6. X
T or F: 1st and 2nd aortic arches do not form any major systems and the 5th arch never developed anything.
True
What do the R and L sides of the 3rd aortic arch give rise to?
- Major Arterial System of the Neck
- R and L common carotid
- MOST of R and L internal carotid
What is contained in the core of each pharyngeal arch?
- Central Rod of Pre-cartilaginous mesenchyme that gives rise to skeletal structures (bond/cart/CT)
**Developement driven by neural crest cells
Failure of NC cells to migrate to pharyngeal arches leads to defects affecting what general area?
- examples
- Anterior face Development Affected
- Cleft Lip and Cleft Palate both result from this
What is derived from the pharyngeal mesoderm component of each arch?
- Skeletal Muscle
- Aortic Arch Derivatives
**NC cells do skeleton/CT stuff
T or F: each cranial nerve associated with a particular arch is derived from the arch itself.
FALSE, they are derived from neuroectoderm that is only associated with the arch
What bones does Arch 1 give rise to?
- note any cartilaginous intermediates
Anterior Face Bones:
- mandible
- maxilla
- zygomatic bones
Middle Ear Bones (from MECKELs Cartilage):
- Malleus
- Incus
What Muscles are derived from Arch 1?
MAST-MATT
Masication:
- massester
- temporalis
- lateral pterygoid
- medial pterygoid
Matt:
- Mylohyoid
- Anterior Digastric
- Tensor Tympani
- Tensor Veli Palatine
If you have an issue in development of arch 1, what will be the likely results?
- Facial Abnormalities
- Difficulty Chewing
What Bones does the 2nd pharyngeal arch give rise to?
- Cells responsible?
- PARTS HYOID BONE
- styloid process of Temporal bone
- STAPES of Middle Ear
**As always NC cells are responsible for the bony and cartilaginous components
T or F: all 3 bones that are important in sound conduction in the middle ear are associated with the 1st pharyngeal arch?
False, malleus and incus are 1st pharyngeal arch stapes is 2nd pharyngeal arch
Why would you expect hearing loss with developmental issues in the 1st and 2nd pharyngeal arches?
Because they make up all 3 bones of the middle ear
What muscles does the 2nd arch give rise to?
- Cells involved?
- Facial Expression muscles
- STAPEDIUS
- stylohyoid
- Posterior digastric
**Pharnygeal arch mesoderm is responsible for muscle development
What is the purpose of the muscles or facial expression and the stapedius?
Facial Expression mm.
- Closing mouth and eyes
Stapedius:
- Protects the ear from loud noises (along with tensor tympani)
What bones does the 3rd pharyngeal arch give rise to?
- cell type?
- The Rest of the HYOID BONE (other pts. from 2nd arch)
**As always NC cells are responsible for the bony and cartilaginous components
What muscles does the 3rd pharyngeal arch give rise to?
- cell type?
- Stylopharyngeus (needed for swallowing)
**Pharnygeal arch mesoderm = cell type
What vessels does arch 3 give rise to?
- Cell type?
- R and L Common Carotid
- R and L Internal Carotid
**cell type = pharyngeal arch mesoderm
What bony/cartilaginous structures does the 4th pharyngeal arch give rise to?
- Cell type?
- Thyroid Cartilage
**As always NC cells are responsible for the bony and cartilaginous components
What muscles doe the 4th pharyngeal arch give rise to?
- General function of muscles?
- Cell type?
**Function = Swallowing
Soft Palate Muscles:
Uvula
5 Pharynx Muscles:
- 3 constrictors (upper, middle, lower)
- Palatopharyngeus
- Salphigopharygeus
**All derived from pharyngeal arch mesoderm
What nerve is the 4th pharyngeal arch associated with? (BE innervation)
- Superior Laryngeal Branch of the Vagus n. (X)
What vascular structures develop from the 4th pharyngeal arch?
- Symmetry?
Asymmetrical:
Right:
Right Subclavian a.
Left:
Arch of the Aorta
What bony/cartilaginous structures does the 6th pharyngeal arch give rise to?
- cell type?
Laryngeal Cartilages
(Cricoid, Arytenoid, Cuneiform, Corniculate)
**As always NC cells are responsible for the bony and cartilaginous components
What muscular structures does the 6th arch give rise to?
** Muscles important in vocalization
- Larynx Muscles
- Striated Muscles of upper esophagus
What nerve supplies BE innervation to the 6th arch?
Recurrent Laryngeal branch of the Vagus n.
What vascular structures develop from the 6th pharyngeal arch?
**Asymmetrical
Right:
- Right Pulmonary a.
Left:
- Left Pulmonary a.
- Ductus Arteriosus
T or F: V3, VII, IX, and X of the pharyngeal arches are all the cranial nerves that have mixed sensory and motor function.
True
What causes First Arch Syndrome?
- Prevalence
- Cell type at fault
- abnormalities
- 2 types
- Most common arch defect
- Faulty migration of NEURAL CREST cells
- Facial Abnormalities
- Treacher Collins Syndrome and Robin Sequence
What are the characteristics of both Treacher Collins Syndrome and Pierre Robin Sequence?
- how to differentiate
Both:
-hypoplasia of the mandible
Treacher Collins:
- Underdeveloped Zygomatic arch
- Malpositioned ears
Robin:
- Cleft palate
- Posteriorly Placed Tongue
What is the cause of Treacher Collins or Robin sequence?
Treacher:
- Autosomal Dominant
- Teratogens
Robin:
- genetic
- Environmental Factors
What does the 1st pharyngeal POUCH give rise to?
Epithelial Lining of:
- Auditory Tube
- Middle ear
What does the 2nd pharyngeal POUCH give rise to?
Epithelial Lining of:
- Palatine Tonsils
What does the 3rd pharyngeal POUCH give rise to?
SECRETORY CELLS of:
- Inferior parathyroid Gland
- Thymus Gland
What does the 4th pharyngeal POUCH give rise to?
SECRETORY CELLS of:
- Superior parathyroid gland
- Ultimobranchial body (parafollicular cells of THYROID
Which of the pharyngeal POUCHES is dependent on NC cell migration?
Pouch 4
T or F: all 4 pharyngeal pouches have dorsal and ventral divisions.
False, only pouches 3 and 4 have dorsal and ventral divisions
Which pouches have structures that develop in situ then migrate to their final positions?
Arches 3 and 4
Structures:
3 - inferior parathyroid and thymus
4 - Superior parathyroid gland and ultimobracnchial body
What syndrome results from NC cells failure to migrate to pouches 3 and 4?
- Symptoms/defects
DiGeorge Anomaly
- Thymic Hypoplasia: Severe Immunodeficiency
- Absence of C cells: Defect in Ca2+ metabolism
- Cadiovascular Defects: Persisent Truncus arteriosus and tetraology of Fallot
- Facial Defects: Shorted Philtrum lip, low set ears
T or F: DiGeorge anomaly is a defect in pharyngeal arch formation so it involves mesodermal tissue and Neural crest cells
False, its a defect in pharyngeal POUCH formation, so it involves defects in ENDODERM and neural crest cells
___________ cells migrate to the _______________ to become parafollicular cells of the thyroid.
- Neural Crest
2. Ultimobranchial body
What are pharyngeal grooves/clefts?
- associated tissues
Ectoderm lined invaginations on the external surface of the lateral wall
How many of the original 4 pharyngeal grooves persist into adulthood?
- what do these give rise to?
- Grooves 2 - 4 get filled with other tissue and smooth over
1st pharyngeal groove:
- External Auditory Meatus
- External Auditory Canal
T or F: there is a DUAL development of the auditory canal
True, 1st pharyngeal pouch (ENDODERM) and 1st pharyngeal groove (ECTODERM) form the inside and outside of the canal respectively
What is created by covering the 2-4th grooves?
Lateral Cervical Sinus
What causes cervical cysts?
- where are they usually found?
- Lateral Cervical Sinuses fill with fluid and enlarge
- Lie along the anterior border of SCM (most commonly under the angle of the mandible)
T or F: cervical cysts can open externally to form a fistula.
True
Thyroid Gland Origin (excluding C-cells)
- Tissue
- Location
- Migration
Tissue:
Endodermal Thickening
Location:
- Origin = FORAMEN CECUM (midline floor of the developing oral cavity )
- Destination = Upper Tracheal Cartilages
Migration:
Down THYROGLOSSAL DUCT
How do thyroid follicles migrate from foramen cecum to the upper tracheal cartilages?
Thyroglossal Duct
What 2 developmental defects are associated with the thyroglossal duct?
- Ectopic Thyroid Tissue
2. Thyroglossal duct cysts
Where are Ectopic Thyroid tissues and thyroglossal cysts typically located?
- Floor of the mouth (forament cecum)
- Near the hyoid bone
- Near thyroid cartilage
What are the 3 parts of the tongue?
- Body - Anterior 2/3
- Posterior 1/3
- Root of the Tongue (epiglottic region)
What marks the boundary between the anterior 2/3 and posterior 1/3 or the tongue?
Sulcus Terminalis
What pharyngeal ARCHES are associated with the mucosa of the tongue?
Anterior 2/3:
- arches 1 and 2
Posterior 1/3:
- arch 3
Root of tongue:
- arch 4
What parts of arches 1, 2, 3, and 4 give rise to the tongue?
Anterior 2/3:
1 and some 2 - LATERAL LINGUAL SWELLINGS
Posterior 1/3:
3 - COPULA of arch 3
Root of Tongue:
4 - hypobranchial eminence
**NOTE these are only giving rise to MUCOSA not tongue muscle
Where are the muscles of the tongue derived from?
- Myoblasts from Mesoderm of Occipital Somites
What nerves convey sensory information from the anterior 2/3 of the tongue?
Arches 1 and 2, so nerves are:
V3 - General sensation: pain, temp, etc. (GSA)
XII - Taste (SA)
What nerve conveys sensory information from the posterior 1/3 of the tongue?
Arch 3 so nerve is:
IX - General Sensation (GSA) and Taste (SA)
What nerve conveys sensory information from the root of the tongue?
Arch 4 so nerve is:
X - General Sensation (GSA) and Taste (SA)
What nerve does the motor innervation to the skeletal muscle of the tongue?
CN XII GSE, (hypoglossal)
What arch gives rise to ALLL of the skeletal structure of the face?
- ARCH 1 - via Mesodermal and Neural Crest cells
What 5 facial prominences (swellings) are comprised of mesoderm and neural crest cells?
- Single Frontonasal Prominence
- R and L maxillary Prominences
- R and L Mandibular Prominences
What 2 prominences are formed by elevations of the frontonasal prominence?
- Medial and Lateral Nasal Prominences
What does the mandibular prominence give rise to?
- Lower Jaw
- Lower Lip
What does the Frontonasal Prominence give rise to?
- Forehead Cranium
- Bridge of the Nose
What does the medial nasal prominence give rise to?
- Philtrum of upper Lip
- Tip of Nose
- Intermaxillary Process
What does the lateral nasal prominence give rise to?
Ala of the nose
What does the maxillary prominence give rise to?
- Central Face
- Lower Eyelid
- Laterall Upper lip
What causes cleft lip?
Failure of maxillary prominence to fuse with medial nasal prominence
*unilateral or bilateral
T or F: cleft lip is always associated with cleft palate
FALSE
Besides forming the upper lip, what else do the maxillary and medial nasal prominences give rise to?
- Hard Palate
What parts of the hard palate are formed by the medial nasal prominences and the maxillary prominences?
Medial Nasal Prominences:
- intermaxillary segment (∆ at front of mouth)
Maxillary Prominences:
- Palatine Shelves (form the rest of the hard palate)
What causes cleft palate?
- Failure of palatine shelves to fuse with each other or with the intermaxillary segment
Why does cleft palate often occur with cleft lip?
Because they are derived from the same structures (medial nasal prominences and maxillary prominences
What is the primary palate?
- Secondary?
1º- intermaxillary segment
2º - Posterior part formed by fusion of the palatine processes of maxilla
What are the 5 different facial prominences?
Frontonasal Maxillary Medial Nasal Lateral Nasal Mandibular
What part of the hyoid is derived from the 2nd arch?
- Lesser Horn and Upper Body of Hyoid
What part of they hyoid is derived from the 3rd arch?
- Greater Horn and Lower Body
