The pharyngeal arches appear around the 4th to 5th week of development and develop into structures of the head and neck. They are bars of mesoderm tissue forming around the pharynx and demarcated internally by the pharyngeal pouches (grooves on the endoderm) and externally by the corresponding pharyngeal clefts (grooves on the ectoderm). There are six arches, but only five are considered as the 5th … Continue reading Pharyngeal arches
During development, bones of the skull base ossify in cartilage (i.e. endochondral ossification). They include the basioccipital, basisphenoid, petrous temporal and ethmoid bones. The skeletal capsules that house and protect the special sense organs also contribute to the skull base: the olfactory capsule contributes to the ethmoid bone, the optic capsule to the sphenoid bone and the otic capsule to the petrous temporal bone. The … Continue reading Skull development
Face The external face forms between the 4th and 6th weeks of embryonic development. It initially involves degeneration of the oropharyngeal membrane that divides the primitive mouth and pharynx. The face is then completed by fusion of five neural crest-filled swellings of ectoderm: the unpaired medial frontonasal process which is divided into lateral and medial nasal processes on each side by the future nostrils. The … Continue reading Face & palate development
The vocal cords are formed by the vocal ligaments (free superior edge of the cricothyroid membrane) that are covered in mucous membrane. Although crucial for phonation, the vocal folds are constantly held open at other times by the posterior cricoarytenoids for breathing. Only when speaking do the vocal folds intermittently close, vibrating and causing sound waves as air is pushed out. When closed for phonation, … Continue reading Vocal cords
The laryngeal cavity starts as the the laryngeal inlet, and ends at the cricoid cartilage which is continous with the trachea below. The larynx is divided at the vocal folds into the vestibule (supraglottic cavity) above and infraglottic cavity below. The two vocal folds form the glottis, with the space in between being known as the rima glottidis. The vestibule is supplied by the superior … Continue reading Laryngeal cavity
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