Development of head and neck Flashcards
In week 4, what proportion of the embryo is made up of the future head and neck?
Half of it
What is the structure of the face of the embryo at week 4 of development?
No structure, completely undeveloped
What is the structure of the head and neck of the embryo in early development?
Frontonasal prominence in the head
Pharyngeal arches
Why is the frontonasal prominence named so?
At the front of the embryo
Where nose develops
Prominent because of developing brain behind it
How many pharyngeal arches are there in the embryo in early development?
5 of them
but are numbered 1, 2, 3, 4, 6
What is a pharyngeal arch made up of?
Mesenchymal proliferation
-mesoderm with some neural crest cells
Inner endoderm lining
Outer ectoderm lining
What does the mesenchyme in the pharyngeal arch develop into?
Cartilage bar
Muscle
Artery
What supplies a pharyngeal arch?
Each pharyngeal arch has its own blood supply
and is innervated by its own cranial nerve
Which pharyngeal arch is the biggest?
1st pharyngeal arch
How do the pharyngeal arches change in size?
Get smaller from the 1st pharyngeal arch to the 6th pharyngeal arch
How does the number of derivatives of the pharyngeal arches change? Why?
Fewer derivatives from the 1st pharyngeal arch to the 6th pharyngeal arch
because they get smaller
What are the parts of the 1st pharyngeal arch?
Maxillary zone
Mandibular zone
Which cranial nerves innervate the pharyngeal arches?
CNs 5, 7, 9, 10
Which cranial nerve innervates the 1st pharyngeal arch?
CN5 trigeminal nerve
Which cranial nerve innervates the 2nd pharyngeal arch?
CN7 facial nerve
Which cranial nerve innervates the 3rd pharyngeal arch?
CN9 glossopharyngeal nerve
Which cranial nerve innervates the 4th pharyngeal arch?
CN10 vagus nerve
Which cranial nerve innervates the 6th pharyngeal arch?
CN10 vagus nerve
Which muscles does the 1st pharyngeal arch give rise to?
Muscles of mastication
Which muscles does the 2nd pharyngeal arch give rise to?
Muscles of facial expression
Which muscles does the 3rd pharyngeal arch give rise to?
Stylopharyngeus
Which muscles does the 4th pharyngeal arch give rise to?
Pharyngeal muscles
Which muscles does the 6th pharyngeal arch give rise to?
Laryngeal muscles
What is the cartilage bar of the 1st pharyngeal arch called?
Meckel’s cartilage
What bones does Meckel’s cartilage develop into?
Malleus, incus
Template for mandible
What is the cartilage bar of the 2nd pharyngeal arch called?
Reichert’s cartilage
What bones does Riechert’s cartilage develop into?
Stapes
Upper part of hyoid bone
Styloid process
What bones does the cartilage bar of the 3rd pharyngeal arch develop into?
Rest of hyoid bone
What does the cartilage bar of the 4th pharyngeal arch develop into?
Larynx cartilages
- thyroid
- cricoid
- aretynoid
What does the cartilage bar of the 6th pharyngeal arch develop into?
Larynx cartilages
- thyroid
- cricoid
- aretynoid
What is the blood supply of the 3rd pharyngeal arch?
Internal carotid artery
What is the blood supply of the 4th pharyngeal arch?
Left side gives aortic arch
Right side gives brachiocephalic trunk
What is the blood supply of the 6th pharyngeal arch?
Pulmonary trunk
What happens to the blood supply of the 1st and 2nd pharyngeal arches?
Disappear
What is the name of the dent between pharyngeal arches in the endoderm?
Pharyngeal pouch
What do the pharyngeal pouches develop into?
Glands of head and neck
Which pharyngeal pouch is the biggest?
1st pharyngeal pouch
between the 1st and 2nd pharyngeal arches
What does the 1st pharyngeal pouch develop into?
Eustachian tube
Middle ear
What does the second pharyngeal pouch develop into?
Palatine tonsils
What do the third and fourth pharyngeal pouches develop into?
Third - inferior parathyroid gland, thymus gland
Fourth - superior parathyroid gland
What is the name of the dent between pharyngeal arches in the ectoderm?
Pharyngeal cleft
What does the 1st pharyngeal cleft develop into?
External acoustic meatus
What happens to the 2nd-6th pharyngeal clefts?
2nd pharyngeal cleft grows larger and downwards to cover and close up all the other clefts
What is a branchial cyst?
Fluid-filled sac in the neck
How do branchial cysts form?
2nd pharyngeal cleft grew larger and downwards to cover all the other clefts
but didn’t fully close them up
What is a branchial fistula?
Opening into neck
How do branchial fistulas form?
2nd arch pharyngeal cleft grew larger and donwards
but didn’t fully cover all the other clefts
gives opening into neck
How do branchial cysts present?
Swelling in neck
Where are branchial cysts and fistulas located in the neck?
Anterior to the sternocleidomastoid muscle
Where are pharyngeal arches located in the embryo?
Lateral walls of pharynx
How does the development of the blood supply of the head and neck relate to the recurrent laryngeal nerve?
Explains why the right one turns under the right subclavian
and why the left one turns under the aortic arch
