Head and Neck Embryology Flashcards
RECAP- what happens after the sperm fertilises the egg?
Zygote divides to form blastocyst
RECAP- the blastocyst flattens. What does this form?
Bilateral disc which then develops into three layers = trilaminar disc
RECAP- name the three layers of the trilaminar disc.
Ectoderm
Mesoderm
Endoderm
RECAP- name the space above the ectoderm/.
Amniotic cavity
RECAP- name the space below the endoderm.
Yolk sac
RECAP- the notochord forms in the trilaminar disc. This is the axis for many developments. However, the notochord does not fully extend from the very top of trilaminar disc to the very bottom.
What happens in these sections?
No mesoderm so ectoderm and endoderm fuse.
There are two areas with no mesoderm and these form the mouth and the anus.
RECAP- describe the development of the neural tube.
Notochord releases chemicals which causing thickening of ectoderm epithelium. This forms neural crests.
The ends of the neural crests come together and closes, forming the neural tuber which then sinks down away from the ectoderm.
->if you don’[t understand this, watch the Part 1 of Head and Neck Embryology, goes over a recap of what we know so far and might be useful before exam!
RECAP- what forms from the neural tube?
Brain and spinal cord
RECAP- in the process of neural tube formation, what else is produced?
Neural crest cells which migrate and give rise to many different structures.
RECAP- what comes from the paraxial mesoderm?
Somites
What do somites go onto develop?
Axial skeleton
Muscles
RECAP- how many somites are formed in human embryos?
33
RECAP- what does the ectoderm develop into?
Skin
->think, the ectoderm goes around everything
RECAP- what does the mesoderm develop into?
Muscle, connective tissue
RECAP- what does the endoderm develop into?
Gut tube
RECAP- where does the respiratory tract develop from?
Foregut regions
What are the pharyngeal/brachial arches?
Series of arches which develop around the future mouth and pharynx.
When in the process of embryological development do the pharyngeal/branchial arches develop?
Late week 4- week 6
How many branchial arches develop?
5
->six start to develop but no.5 disappears leaving us with 1,2,3,4,6
What makes up the branchial arches?
Ectoderm- makes outside
Mesoderm- bulky middle section + neural crest cells
Endoderm- lines inside of arch
Which structures develop in the mesoderm of the branchial arches?
Blood vessels
Nerves
Skeletal elements
(think about what arises from mesoderm in general)
What else can the ectoderm form in the branchial arches as well as forming the outer layer?
Forms clefts between the arches
These clefts can develop into structure like the tongue
What else can the endoderm form in the branchial arches as well as forming the inner layer?
Forms pouches between the arches
Cranial nerves form from the branchial arches.
Which nerve develops from the first branchial arch?
IMPORTANT TO REMEMBER, COMMON EXAM QUESTION
Mandibular branch of Trigeminal nerve (CN V3).
Cranial nerves form from the branchial arches.
Which nerve develops from the second branchial arch?
IMPORTANT TO REMEMBER, COMMON EXAM QUESTION
Facial nerve (CN VII)
Cranial nerves form from the branchial arches.
Which nerve develops from the third branchial arch?
IMPORTANT TO REMEMBER, COMMON EXAM QUESTION
Glossopharyngeal nerve (CN IX).
Cranial nerves form from the branchial arches.
Which nerve develops from the fourth branchial arch?
IMPORTANT TO REMEMBER, COMMON EXAM QUESTION
Superior laryngeal branch of the Vagus nerve (CN X)
Cranial nerves form from the branchial arches.
Which nerve develops from the sixth branchial arch?
IMPORTANT TO REMEMBER, COMMON EXAM QUESTION
Recurrent laryngeal branch of the Vagus nerve (CN X)
Which nerve innervates all the muscles of face expression of the face?
Facial nerve (CN VII)
Therefore, which branchial arch does nerve supplying the face come from?
Second branchial arch