Embryological Development (pharyngeal Arches) Flashcards
Describe the structure of a pharyngeal arch in a transverse/cross sectional image:
Ectoderm lines the outside
Endoderm lines the inside
Cartilage bar in the core of the arch (between ectoderm and endoderm)
Cranial nerve coming from the neural tube
Go to the last slide of the Embryological development and label the cross sectional image of the pharyngeal arch:
1 = endoderm
2 = ectoderm
3 = cartilage bar
4 = neural tube
5 = cranial nerve
6 = artery
What is derived from the ectoderm in the pharyngeal arch?
Skin overlying head and neck
Glands
GI
Resp
Covers superficial surface of arch
What is derived from the endoderm of the pharyngeal arch?
Epithelial lining of the GI and resp (pharynx)
Endocrine glands
Covering deeep aspect of arch
What is the function of the cartilage bar in the pharyngeal arch?
Supports the arch
Has muscles associated with it
What embryological layer is the cartilage bar of the pharyngeal arch derived from?
Mesoderm
Describe the general rule for cranial nerve supply and arterial supply to the pharyngeal arches:
Each arch has a different cranial nerve and branch of the aortic arch supplying it
What muscles does the cranial nerve in the pharyngeal arch supply?
The muscles associated with the cartilage bar
How many pharyngeal arches are there?
5
How are the pharyngeal arches numbered?
Ordered from rostral to caudal
Arches, I, II, III, IV and VI (no V)
What nerve and branch of the aorta supplies the 1st pharyngeal arch?
Trigeminal nerve (V)
Aortic arch I
What muscles are associated with/derived from the cartilage bar in pharyngeal arch 1?
What skeletal elements are derived from pharyngeal arch 1?
Muscles of mastication:
-medial + lateral pterygoids
-Temporalis
-masseter
Mandible
structures of middle ear (malleus and incus)
What nerve and branch of the aorta supplies the 2nd pharyngeal arch?
Facial nerve (VII)
2nd aortic arch
What muscles are associated with/derived from the cartilage bar in pharyngeal arch 2?
What skeletal elements are derived from pharyngeal arch 2?
Muscles of facial expression:
-occipitofrontalis
-Orbicularis oculi
-orbicularis oris
-Buccinator
-Zygomaticus major
Stapes (middle ear bone) + superior part of hyoid
What muscle attaches to stapes pulling on it?
Stapedis
Damage to what nerve can lead to hearing problems and why?
Facial nerve (VII)
Muscles like stapedis supplied by it so if it gets damage doesn’t pull on stapes leading to hearing problems
What nerve and branch of the aorta supplies the 3rd pharyngeal arch?
Glossopharyngeal (IX)
3rd aortic arch
What muscles are associated with/derived from the cartilage bar in pharyngeal arch 3?
What skeletal elements are derived from pharyngeal arch 3?
Stylopharyngeus
Inferior part of hyoid
What nerve and branch of the aorta supplies the 4th and 6th pharyngeal arch?
Vagus nerve (X) supplies both the 4th and 6th pharyngeal arch
Aortic arch 4+6 respectively
What muscles are associated with/derived from the cartilage bar in pharyngeal arch 4+6?
What skeletal elements are derived from pharyngeal arch 4+6?
Pharyngeal and laryngeal muscles
Laryngeal cartilages
What is a pharyngeal cleft?
Invagination in the ectoderm of the pharyngeal arch
(Invagination on the outside)
What is a pharyngeal pouch?
Invagination of the endoderm around the pharyngeal arch
(Invagination on the side)
Which one is superficial and which one is deep, the Pharyngeal cleft or the pharyngeal pouch?
Pharyngeal cleft = superficial
Pharyngeal pouch = deep
What develops from the First pharyngeal pouch+cleft?
Ear
What develops from the Second pharyngeal pouch+cleft?
Palatine tonsils
What develops from the third and forth pharyngeal pouch+cleft?
Thymus gland
Parathyroids
What is formed when the first pharyngeal pouch and the first pharyngeal cleft come into contact?
Thin membrane called Tympanic membrane
What structure does the first pharyngeal pouch form?
Eustachian tube
What structure does the first pharyngeal cleft form?
External acoustic meatus
What structures does the Eustachian tube connect?
Ear with the pharynx
What is significant about the growth of the second pharyngeal arch?
It grows downwards destroying the clefts from the 2nd pharyngeal cleft onwards
What are the 3 types of disorders that can form as a result of the incorrect obliteration of the pharyngeal clefts by the second pharyngeal arch’s downward growth?
Branchial cysts
Branchial sinuses
Branchial fistulas
What is a Branchial cyst?
An enclosed cyst filled with fluid
(Growth of second pharyngeal arch left an enclosed space)
Where is the lump located with a Branchial cyst?
In the anterior triangle anterior to Sternocleidomastoid
What is a Branchial sinus?
When the space left by the incomplete obliteration of the pharyngeal clefts are open to the skin (hole in skin)
What is a Branchial fistula?
When the pharyngeal cleft that has failed to obliterate connects with the pharynx
Its an abnormal connection with the ectoderm and the endoderm
