4 - Head & Neck - Development (Pharyngeal arches) Flashcards
After how many weeks after fertilisation do the pharyngeal arches appear?
~ 4 weeks
What type of tissue covers the external surface of the pharyngeal arches?
Ectoderm
What type of tissue covers the internal surface of the pharygeal arches?
Endoderm
What type of tissue/cells form the ‘filling’ of the pharyngeal arches? (between the ectoderm and endoderm)
- Mesenchyme tissue (mesoderm)
- Neural crest cells (originate from neuroectoderm)
What happens to the pharygeal clefts between the arches (outer surface)?
The 2nd arch grows down and obliterates the other clefts, such that only the 1st cleft (between arches 1+2) remains
What is the name given to the grooves between the pharyngeal arches on the outer surface (ectoderm)?
Pharyngeal clefts
What is the name given to the grooves between the pharyngeal arches on the inner surface (endoderm)?
Pharyngeal pouches
Which pharyngeal arch is the biggest?
1st arch (has 2 prominences)
How many pharyngeal arches do we have?
Theoretically 6, but the 5th does not form in humans. They are numbered 1-4, 6.
Which arteries are associated with pharyngeal arches 1-3?
- Common carotid
- External carotid
- Internal carotid
+ Branches
The common, external and internal carotid arteries are associated with which pharyngeal arches?
1-3
Which arteries are associated with the 4th pharyngeal arch?
- Aortic arch on L
- Subclavian artery on R
Which arteries are associated with the 6th pharyngeal arch?
- Pulmonary arteries
Which cranial nerves are the pharyngeal arches associated with?
- CN V Trigeminal
- CN VII Facial
- CN IX Glossopharyngeal
- CN X Vagus
Which cranial nerve is associated with the 4th and 6th pharyngeal arches?
CN X Vagus
6th arch = Recurrent laryngeal branch
What structures are each pharyngeal arch associated with?
- Aortic arch
- Vein
- Cranial nerve
- Cartilage bar
Name the cartilage bar which develops from the 1st pharyngeal arch. What are its derivatives?
- Meckels cartilage
- Mandible, Malleus, Incus
What are the derivatives of the cartilage bars which form from the 4th and 6th pharyngeal arches?
- Epiglottis
- Thyroid
- Arytenoids
- Cricoid
From which pharyngeal arch do the muscles of mastication and the digastric muscle derive?
1st pharyngeal arch
From which pharyngeal arch do the muscles of facial expression derive?
2nd pharyngeal arch
From which pharyngeal arch do the intrinsic muscles of the larynx derive?
6th pharyngeal arch
What is the derivative of the 1st pharyngeal cleft?
External auditory meatus
If remnants of pharyngeal clefts other than the 1st one remain, cysts and fistulae may develop along the border of which muscle?
Anterior border of Sternocleidomastoid
What is the derivative of the 1st pharyngeal pouch?
Eustachian tube and middle ear cavity
