Embryology Flashcards
What are the pharyngeal arches?
Series of arches which develop around the future mouth and pharynx
What structures develop from the pharyngeal arches?
Face and neck
How many branchial arches are there in humans?
5 - 6 start to develop but arch number 5 disappears
What lines the outside of the branchial arches?
Ectoderm
Ectoderm also forms
the clefts in between the pharyngeal arches
Mesoderm lines and forms
lines the middle of the pharyngeal arches and forms cartilage and muscles
Endoderm lines and forms
lines inside of pharyngeal arches and forms pouches in between the arches
What arches does the digastric muscle develop from?
First (anterior belly) and second (posterior belly) pharyngeal arches
Other important structures that develop from the pharyngeal arches
Tongue
Thyroid gland
Parathyroid gland
Part of pituitary gland
From what processes does the face develop?
Frontonasal
Two maxillary processes
Two mandibular processes
How is the nostril formed?
Ectodermal thickening, pushes inwards to form nasal pit which develops into the nostril
What happens in stage 1 of development of the palate?
Medial nasal process grows downwards and forms philtrum
What happens in stage 2 of the development of the palate?
Two palatine shelves grow inwards from the maxillary processes
What happens in stage 3 of development of the palate?
Palatine shelves meet in the midline to form secondary palate
How are the flat bones of the skull formed?
Membranous ossification
How are the irregular bones of the base of the skull formed?
Endochondral ossification
How is the viscerocranium formed?
Partly from pharyngeal arches and partly from sensory capsules
Mesenchyme is derived from
mesoderm that lies above the surface of the developing brain
Why are the sutures between the skull bones soft at birth?
Allows deformation during passage through the birth canal
What nerve supplies the first pharyngeal arch?
Mandibular branch of trigeminal
What nerve supplies the second pharyngeal arch?
Facial nerve
What nerve supplies the third pharyngeal arch?
Glossopharyngeal
What nerve supplies the fourth pharyngeal arch?
Superior laryngeal branch of vagus
What nerve supplies the sixth pharyngeal nerve?
Recurrent laryngeal
What is craniosynostosis?
Premature fusion of the cranial bones
Sensory capsules are derived from
mesoderm of somites in the head and neck region
What is the function of sensory capsules?
Preform cartilage and ossify to form bones around the sense organs and form part of the base of skull and viscerocranium
To form the base of the skull, bone is laid down by
endochondral ossification
Treacher-Collins syndrome is a result of an abnormality of which pharyngeal arch?
First
