L7: Anterior Cervical Triangle Flashcards
What is the pharyngeal apparatus? When does it start to develop? What are its contents?
- Early embryological structure that contributes to the formation of the head and neck, including face. - 4 week old embryo - Contents: pharyngeal arches, pharyngeal pouches, pharyngeal grooves, pharyngeal membranes
Describe embryological development of the pharyngeal arches. Explain what each arch gives rise: CN, muscle, bone.
- Pharyngeal arches develop at lateral wall of cranial end of foregut - Stomodeum = anterior end of foregut and site of future mouth - Widening at stomodeum, narrowing inferiorly to form espophagus - Oropharyngeal membrane separates primordial pharynx and foregut from amniotic cavity, ruptures at 26th day to allow communication - End 4th week, 4 pairs of arches present. 5th / 6th never develop completely, not visible exteriorly - External arches separated by pharyngeal grooves = ectoderm - Internal arches separated by pharyngeal pouches = endoderm - Arches composed of mesenchyme also, result of neural crest cells - Each arch contains: blood vessel, cartilage (precursor to skeletal/bony components), muscular component (precursor to muscles of head and neck), nerve - First arch = mandibular arch. Bones: maxilla and mandible from prominences named after them. Muscles: mastication, mylohyoid, ant. Belly of digastric, tensory tympani, tensor veli palatini. Nerve: CN V. - Second arch = hyoid arch. Bones: major contribution to hyoid bone. Muscles: facial expression, stapedius, stylohyoid, post. belly of digastric. Nerve: CN VII. - Third arch. Bone: minor contribution to hyoid bone. Muscles: stylopharyngeus muscle. Nerve: CN IX. - Fourth arch. Bone / muscles: muscles and cartilages of larynx. Nerve: CN X.
What are pharyngeal membranes?
- Ectoderm of grooves on outside of pharyngeal wall make contact with endoderm of pouches to form these membranes. First membrane gives rise to tympanic membrane of ear. All other membranes disappear.
What are the derivatives of the first pharyngeal arch?
- First arch = mandibular arch. Bones: maxilla and mandible from prominences named after them. Muscles: mastication, mylohyoid, ant. Belly of digastric, tensory tympani, tensor veli palatini. Nerve: CN V.
What are the derivatives of the second pharyngeal arch?
- Second arch = hyoid arch. Bones: major contribution to hyoid bone. Muscles: facial expression, stapedius, stylohyoid, post. belly of digastric. Nerve: CN VII.
What are the derivatives of the third pharyngeal arch?
- Third arch. Bone: minor contribution to hyoid bone. Muscles: stylopharyngeus muscle. Nerve: CN IX.
What are the derivatives of the fourth pharyngeal arch?
- Fourth arch. Bone / muscles: muscles and cartilages of larynx. Nerve: CN X.
From what does the tympanic membrane of the ear form?
- First pharyngeal membrane gives rise to this.
From what do CN X, IX, VII and V arise?
- Pharyngeal arches. - CN X from 4th arch - CN IX from 3rd arch - CN VII from 2nd arch - CN V from 1st arch
What are the boundaries of the anterior cervical triangle?
- Anterior midline of neck - Inferior border of mandible - Anterior border of SCM
What forms the base, apex, floor, roof of the triangle?
- Apex is at the jugular notch - Base is inferior border of mandible - Roof = superficial fascia, platysma and skin - Floor = mylohyoid and hyoglossal muscles
Subdivisions of anterior cervical triangle. Draw and indicate boundaries.
- Submandibular triangle - Submental triangle - Carotid triangle - Muscular triangle
What are the contents of each of the subtriangles of the anterior triangle, besides muscles?
- Submandibular: submandibular gland, salivary gland, submandidublar ganglion (PSNS ganglion next to submandibular gland), submandibular lymph nodes, hypoglossal CN XII, facial a and v - Submental: submental lymph nodes, beginning of ant jugular veins - Carotid: carotid sheath: vagus nerve (CN X), common carotid and internal carotid and internal jugular v; external carotid and branches - Muscular triangle: thyroid and parathyroid glands (C6 level)
What are the contents of the carotid sheath? Explain with directionality.
- CN X (posteriorly), common carotid (medially), internal jugular vein (laterally), internal carotid (medially superior branch)
What cervical level do the thyroid/parathyroid glands correspond to?
- C6