OCB02-1005 Pharyngeal Arch Development Flashcards
When do pharyngeal arches appear?
4th and 5th weeks of development
what are the arches separated by on the outside?
There are clefts in the ectoderm
What are arches separated by on the inside?
There are pouches in the endoderm
What are the numbers of the 5 arches?
1, 2, 3, 4, 6
What do the arches separate?
the stomatodeum from the developing heart
What is the basic structure of each brachial arch?
Cartilage
Nerve
Artery
Where is the first arch located?
Between the stomatodeum and first pouch
What processes do the first arch form?
Maxillary process and the mandibular process
What bones are formed from the maxillary process?
Maxillary bone
Premaxillary bone
Zygomatic bone
Squamous part of the temporal bone
What cartilage is within the mandibular process?
The meckel’s cartilage, which will disappear with development, with the exception of 2 small portions which form the incus and malleus
What muscles does the first arch form?
Muscles of mastication
What is the nerve supply to the first arch?
Cranial nerve 5
What does cartilage form in the second arch?
The staples, styloid, upper part of the hyoid bone, and lesser horns
What muscles are formed from the second arch?
Muscles of facial expression
What is the nerve supply to the second arch?
Cranial nerve 7
What does the cartilage form in the third arch?
greater horns and the lower part of the hyoid bone
What muscle does the third arch form?
Stylopharyngeus muscle
What is the nerve supply to the third arch?
Cranial nerve 9
What is the nerve supply to the fourth arch?
cranial nerve 10
What muscles does the fourth arch form?
muscles of the Palate and pharynx
What is the nerve supply to the sixth arch?
Recurrent fibres of vagus nerve
Cranial nerve 10
What muscles does the sixth arch form?
Laryngeal muscles
What does cartilage form in the second arch?
The staples, styloid, upper part of the hyoid bone, and lesser horns
What muscles are formed from the second arch?
Muscles of facial expression
What is the nerve supply to the second arch?
Cranial nerve 7
What does the cartilage form in the third arch?
greater horns and the lower part of the hyoid bone
What muscle does the third arch form?
Stylopharyngeus muscle
What is the nerve supply to the third arch?
Cranial nerve 9
What is the nerve supply to the fourth arch?
cranial nerve 10
What muscles does the fourth arch form?
muscles of the Palate and pharynx
What is the nerve supply to the sixth arch?
Recurrent fibres of vagus nerve
Cranial nerve 10
What muscles does the sixth arch form?
Laryngeal muscles
What happens to the maxillary processes from the first brachial arch during the 5th and 6th weeks?
The bilateral maxillary processes derived from the first brachial arch fuse with the medial nasal process to form the upper lip, alveolus and primary palate
What separates the right and left nasal chambers?
Nasal septum
What is the secondary palate formed from?
Palatine shelves that grow medially from the maxillary prominences
When does a cleft palate occur?
When the palatal shelves fail to fuse with each other during the 7th to 10th weeks of development
What may cause a cleft palate?
Inadequate growth of palatine shelves
Failure of shelves to elevate above the tongue
Excessively wide head
Which pharyngeal clefts form a structure in adults?
1st
What does the first cleft form?
The external auditory tube
What happens to the other clefts?
They disappear because of growth of the ectoderm from the second cleft as it grows down and fuses with the sixth arch
What does the 1st pouch develop into?
Auditory tube and middle ear cavity
What does the 2nd pouch develop into?
palatine tonsil
What does the 3rd pouch develop into?
The dorsal wing and inferior parathyroid glands
What does the 4th pouch develop into?
The superior parathyroid gland
What does the 5th pouch develop into?
Ultimobranchial body, which is incorporated into the thyroid and forms the parafollicular cells of the thyroid
How many arches contribute to tongue development?
4
What does the 1st arch form of the tongue?
The anterior 2/3 of the tongue
What do the 3rd and 4th arches of the tongue form?
posterior 1/3 of the tongue
