Arches Flashcards
When does the development of the pharyngeal arches occur?
Week 4-5
Neck develops from
Primitive pharynx
Pharyngeal apparatus are similar to…
Gills
Branchi = Greek for gill
Pharyngeal Apparatus consists of
Pharyngeal arches
Pharyngeal punches
Pharyngeal grooves
Pharyngeal membrane
Pharyngeal arches
Mesoderm and ectoderm neural crest cells
Pharyngeal pouches
Endodermal tissue (inside)
Pharyngeal grooves
Ectoderm outside
Pharyngeal membrane
Pouch on the inside and grooves on the outside
Mesenchymal tissue in arches
Multi potent stem cells that can move around are derived form neural crest cells
They can eventually become mesoderm and ectoderm
When do pharyngeal arches form?
Fourth week
What starts the formation of pharyngeal arches ?
Neural crest cells migrate into the head and neck region
The first arch will form as
Elevations lateral to the devloping pharynx
Develop in cranial caudal fashion
Neural crest cells form from
Developing neural plate ( which formed from the notochord)
Neural crest cells migrate from
Posterior neural tube region to the anterior
What do neural crest cells carry
Genetic code for development
Day 24
Rapid proliferation mesenchyme begin to form prominences
Stomodaeum
Mouth
Formed by ectoderm invagination
Oral cavity (periodontum, enamel, etc.) develop from
Ectoderm
Stomodaum and primitive pharynx separated by
Buccopharyngeal membrane
Buccopharyngeal membrane will
Ruptures via apoptosis and create the opening to the oropharynx
Another name for pharyngeal arches
Branchial arches
Bars of mesenchyme aggregates and form
Arches
Clefts/grooves
Internal pouches
The first pharyngeal arch develops
(Mandibular arch)
Develops maxillary and mandibular prominences
The second pharyngeal arch develops into
(Hyoid arch)
Contributes to the formation of the hyoid bone
Arches made of
Mesenchyme encased in external ectoderm and internal endoderm
Arches contains a
Nerve
Artery
Cartilage (bone precursor)
Muscle group
Arches 3rd week-
Arches 4-6weeks-
Bulges are mesenchyme (3rd)
Neural crest cells (4-6)
How many arches are there ?
6 arches
1,2,3,4,6
Arch I contains
Maxillary and mandibular prominences
Arch V and Arch VI are
Do not form visible prominences
Arch V
Degenerates
Arch I arteries
Maxillary Artery
Arch II arteries
Stapedial artery (embryonic) then Corticotympanic artery (adult).
Arch III arteries
Carotid artery
Arch IV arteries
Part of aorta
Right subclavian artery
Arch VI arteries
Pulmonary Artery roots
Arch I Cartilage
Maxillary and mandibular (meckel’s) cartilage
Malleus and incus
Arch II Cartilage
Reichert's cartilage forms: Stapes Styloid process Stylohyoid ligament Lesser horn of the hyoid
Arch III Cartilage
Greater horn of the hyoid
Arch IV Cartilage
Thyroid cartilage
Arch VI Cartilage
Cricoid cartilage
Arch I Nerves
Trigeminal Nerve V
Maxillary branch 2
Mandibular branch 3
Arch II Nerves
Facial Nerve VII
Arch III nerves
Glossopharyngeal Nerve IX
Tongue
Arch IV Nerves
Vagus Nerve X
Arch VI Nerves
Vagus Nerve X
Ectodermal invagination from epibranchial Placodes form
Nerve ganglion of
cranial nerves V, VII, IX, X
Arch I muscle
Mastication muscles
Arch II Muscle
Stapedius Stylohyoid Posterior belly of digastric Auricular Muscles of facial expression
Arch III muscles
Stylopharyngeus
elevates larynx and pharynx for swallowing
Arch IV Muscles
(Facilitates swallowing)
Cricothyroid
Levator Veli Palatini
Constrictors of Pharynx
Arch VI Muscles
(Sound production)
Intrinsic muscles of the larynx
Derivatives
Formations originating from:
Clefts/grooves (external ectoderm)
Pouches (internal endoderm)
Which derivatives are more complex
Pouches
Celft I
Formed from arch 1
Cleft 1 forms external auditory meatus
Pharyngeal arch 2 becomes
Rapid proliferation of mesenchyme grows over remaining clefts
Clefts 2-4
Form the cervical sinus that normally resorbs
Cervical cysts
always on the lateral edge of neck
Anterior to sternocliedomastiod
Can be isolated or externally fistulated (leakage of material)
Pharyngeal Pouch 1
Derivatives
Pharyngotympanic tube
Enlarges and gets close to cleft 1
ear related
Pharyngeal Pouch 2
Derivatives
Palatine tonsil
Pharyngeal Pouch 3
Derivatives
Inferior parathyroid gland (dorsal)
Thymus (ventral)
Pharyngeal Pouch 4
Derivatives
Superior parathyroid gland (dorsal)
Ultimo branchial body ( ventral/superior)
What contribute c cells
Ultimo brachial body
Cleft are
Pouches are
Outside
Internal
Pouches
Internal endoderm forms
Outline for future oropharynx
Pouches form around oropharynx called
Pharyngeal pouches that will form pharyngeal derivatives
Inferior parathyroid gland border
Pouch 3
Joins the inferior posterior border of the thyroid
Thymus descends …
Pouch 3
Foregut
Superior parathyroid gland borders
Pouch 4
Joins the superior border of the thyroid
Ultimobranchial body joins
Pouch 4
The thyroid and forms follicular c cells that produce calcitonin
Which pouch will grow faster 3 or 4?
Pouch 3
Thyroid migrates from
Foramen cecum to bellow the cricoid
Migration of thyroid forms
Thyroglossal duct (tongue thyroid)
Cleft of poor thyroid migration
Can form thyroglossal duct cyst
Primitive thyroid forms at
Midline of the pharynx below the tuberculum impar
Thyroid can start functioning as early as
The 10th week
When and where is the final portion of the thyroid in position
Week 7
Two thyroid lobes inferior to the cricoid cartilage
Thyroglossal duct
Where the thyroid primordium descends through the neck
Degenerates at end of 5th week
Problems that arise with the Thyroglossal duct
Portion of the duct persists as a cyst or sinus on the neck
Fragment of thyroid breaks off during descent and form ectopic tyriod tissue
Thyroglossal duct cyst
Thyroid migration issue
Always midline of the neck
Cysts can be confined or fistulated through the oral duct ( can cause obstruction of the airway)
Which two arches are associated with tounge development ?
Arch 1 and 2
When does tounge development occur?
Around week 4
What starts the formation of the the tounge ?
Proliferation of mesenchyme resulting in the formation of several swelling
Oral part (anterior 2/3) develops from the fusion of:
Lateral lingual swellings
Median tongue bud ( tuberculum impar)
Pharyngeal part/root of the tounge (posterior 1/3) develops from:
Copula/hypobranchial eminence
Forms from the 2nd, 3rd, and 4th branchial arteries
Muscles of the tounge arise from
Occipital Somites which migrate into the tongue area
Primary defect in arch 1
Facial clefting
Micrognathia
Defect in arch 1
Small mouth
Hemifacial microstomia
Defect in arch 2
When one half of the face is underdeveloped or doesn’t grow normally
Digerorge syndrome
Defect in arch 3 and 4
Infant has seizures
Ventricular septal defect
Small mandible
Defect in arch 4
Heart issues