Development of the Head and Neck pt. 1 Flashcards
Manyt head and neck structures form from the mesoderm-mesenchyme found in and near five bilateral pairs of
Pharyngeal (branchial) Arches
These 5 pharyngeal arches appear during the
Fourth week of prenatal development
The five pharyngeal arches appear during the 4th week of prenatal development and are numbered
1, 2, 3, 4, and 6 (the 5th quickly disappears)
Precursor cells in pharyngeal arches and in regions rostral to pharyngeal arches are derived from
Mesoderm and Neural crest
Each pharyngeal arch is a bar of mesoderm-mesenchyme that is separated by
Folds of surface ectoderm (pharyngeal clefts/grooves) and folds of endoderm (pharyngeal pouches)
Contains its own specific nerve, artery, muscle, and connective tissure
Ech pharyngeal arch
Cranial nerves extend from the developing brainstem into
Pharyngeal arches
Conversely, pharyngeal arch mesoderm and neural crest gives rise to
Aortic arches, skeletal muscles, and connective tissues
Pharyngeal arch 1 is comprised of which two prominences?
Maxillary prominence and mandibular prominence
What is the cranial nerve that is associated with the 1st pharyngeal arch?
Trigeminal nerve
What is the aortic arch of the 1st pharyngeal arch?
I (maxillary)
From the mesoderm, the mandibular prominence of the 1st pharyngeal arch has which skeletal muscles?
Mastication muscles, tensors, anterior digastric, mylohyoid
The maxilla, zygomatic bone, squamous temporal bone, palatine, and volmer are the connective tissues (derived from neural crest) associated with the
Maxillary prominence of 1st pharyngeal arch
What is the nerual crest connective tissue associated with the mandibular prominance of the 1st pharyngeal arch?
Mandible, malleus, and incus
What is the cranial nerve of the second pharyngeal arch?
Facial nerve (VII)
What is the aortic arch of the 2nd pharyngeal arch?
II (stapedial)
What are the mesodermal skeletal muscles of the 2nd pharyngeal arch?
Facial expression muscles, stapedius, posterior digastric, and stylohyoid
The stapes, styloid process, lesser hgorn of hyoid bone, and upper body are neural crest connective tissues of the
2nd pharyngeal arch
What is the cranial nerve of the 3rd pharyngeal arch?
Glossopharyngeal nerve (IX)
What is the aortic arch of the 3rd pharyngeal arch?
III (part of internal carotid)
What is the mesodermal skeletal muscle of the 3rd pharyngeal arch?
Stylopharyngeus
What are the neural crest derived connective tissues of the 3rd pharyngeal arch?
Greater hgorn of hyoid and lower body
What is the cranial nerve of the 4th pharyngeal arch?
X (Superior lingual of vagus)
What is the aortic arch of the 4th pharyngeal arch?
IV (parts of right subclavian and aortic arch)
The soft palate muscles (except tensor) and the pharyngeal muscles (except stylopharyngeus and cricothyroid) are the mesodermal skeletal muscles of the
4th pharyngeal arch
What is the neural crest derived connective tissue of the 4th pharyngeal arch?
Laryngeal cartilage
What is the cranial nerve of the 6th pharyngeal arch?
X (recurrent laryngeal nerve of vagus)
What is the aortic arch of the 6th pharyngeal arch?
VI (Ductus arteriosis and pulmonary)
What are the mesodermal skeletal muscles of the 6th pharyngeal arch?
Intrinsic laryngeal (except cricothyroid) and esophageal muscles
What are the neural crest derived connective tissues of the 6th pharyngeal arch?
Laryngeal cartilage
The stomodeum (primitive mouth) and pharynx meet at the oropharyngeal/buccopharyngeal membrane where the
Ectoderm meets endoderm without intervenin mesoderm
The oropharyngeal membrane disintegrates, which allows for a continuouslumen between the
- ) Ectoderm lined?
- ) Endoderm lined?
1.) Stomodeum (primitive mouth) 2.) Foregut
Derived from multiple pharyngeal arches and extends from the pharynx into the stomodeum
Tongue
The epithelium covering the anterior 2/3 of the tongue and the surrounding oral cavity are derived from
Ectoderm
The glandular epithelium of the parotid gland is derived from
Ectoderm
The epithelium covering the pharyngeal part fo the tongue (posterior 1/3) and surrounding oropharynx are derived from?
Endoderm
The glandular epithelium of the submandibular and sublingual glands is derived from
Endoderm
However, the supportive glandular stroma is derived from
Mesoderm-mesenchyme of associated arches
For the posterior 1/3 of the tongue, the general sensory and taste information is conveyed through the
Glossopharyngeal nerve (IX)
It should be noted that some taste information in the posterior 1/3 of the tongue is also provided by the
Vagus nerve
The somatic MOTOR innervation to all skeletal muscles of the tongue (except the palatoglossus) is conveyed through the
Hypoglossal Nerve (XII)
The Palatoglossus is innervated by the
Vagus nerve (X)
Proliferates in the midline of the ventral wall of the pharynx to form the connective tissue that contains sensory nerves of the anterior 2/3 and posterior 1/3 of the tongue
Tongue pharyngeal arch mesenchyme
Tongue skeletal muscle forms from migrating myoblasts of
Occipital somitomeres
Forms from the growth of the two lateral lingual swellings and a median lingual sweeling (tuberculum impar) in the 1st pharyngeal arch
The anterior 2/3 of the tongue
Make up most of this growth and meet in the midline of the tongue as the median lingual sulcus
Lateral lingual swellings
The lateral lingual swellings make up most of the growth of the anterior 2/3 of the tongue and meet in the midline as the
Median lingual sulcus
Failure of the lateral lingual swellings to completely fuse in the midline results in
Bifid tongue
Forms from the hypopharyngeal eminence in the 3rd and 4rth pharyngeal arches
Posterior 1/3 of the tongue
Defines the boundary between the anterior and posterior tongue
Terminal sulcus
The location of midline ventral endodermal envagination to form the thyroid gland
-at the root of the tongue
Foramen cecum (Thyroid diverticulum)
Myoblasts from occipital somitomeres migrate to the developing tongue mesenchyme and drag the
-for somatic innervation
Hypoglossal nerve
The face and palate formation begins anteriorly as 5 mesenchymal prominences (bumps) at about
4-5 weeks
These mesenchymal prominences (bumps) surround the stomodeum and are covered by
Surface ectoderm
Derived from the mesenchyme rostral to the pharyngeal arches and lies ventral to the forebrain and cranial stomodeum
The single midline Frontonasal prominence
The single midline frontonasal prominence lies
- ) Ventral to the
- ) Cranial to the
- ) forebrain
- ) stomodeum
The pair of maxillary prominences of the first pharyngeal arch lie LATERAL to the
Stomodeum
The pair of mandibular prominences of the first pharyngeal arch lie CAUDAL to the
Stomodeum
These prominences contain connective tissue-forming mesenchymal cells covered by
Epidermis-forming surface ectoderm
As these prominences proliferate and migrate towards the midline, they form the
Face and palate
Deformities of the lip and palate are described as anterior and/or posterior to the incisive foramen and may be
Unilateral or bilateral
Bilateral surface ectoderm thickenings that develop on the frontonasal prominence
Nasal placodes
Lateral and medial prominences surround each nasal placode and grow forward while the placodes remain stationary. This gives the impression of “invaginations” to form
Nasal cavities
This nasal placode ectoderm will form the epithelium lining of nasal cavities, including the olfactory epithelium that is responsible for the sense of
Smell
More specifically, surface-ectoderm nasal placodes form “pits” that become
Nasal cavities lined by nasal epithelium
Frontonasal prominence mesenchyme develop as “rises” that will form
Midline structures (nose, philtrum of upper lip, primary palate)
The “rises” surrounding the “pits” are called
Medial and lateral nasal prominences
Fusion of themedial nasal prominences creates the intermaxillary segment that develops into the
Primary palate (anterior to incisive foramen)
Proliferation of the adjacent maxillary prominences “pushes” the midline fusion of the medial nasal prominences to form the
Intermaxillary segment
The frontonasal prominence also gives rise to
Forehead and nasal septum
