Anterior boundary of the anterior triangle of the neck
Midline of neck
Posterior border of the anterior triangle of the neck
Anterior border of sternocleidomastoid
Superior border of the anterior triangle of the neck
Inferior border of the body of mandible
What are the muscle groups of the anterior triangle of the neck?
- infrahyoid muscles
- suprahyoid muscles
- anterior vertebral muscles
Infrahyoid muscles
Thin, strap-like muscles
- sternohyoid
- sternothyroid
- thyrohyoid
- omohyoid
Where is the sternohyoid located?
Supercially, medial to superior belly of omohyoid
Origin of sternohyoid
Posterior surfaces of manubirum of sternum and eternal end of clavicle
Insertion of sternohyoid
Body of hyoid
Nerve supply of sternohyoid
Ansa cervicalis (C1-C3)
Action of sternohyoid
Depresses hyoid bone
Where is sternothyroid located?
Deep to sternohyoid
Origin of sternothyroid
Posterior surface of manubrium of sternum
Insertion of sternothyroid
Oblique line of thyroid cartilage
Nerve supply of sternothyroid
Ansa cervicalis (C1-C3)
Action of sternothyroid
Depresses larynx
Thyrohyoid
Upward continuation of sternothyroid
Origin of thyrohyoid
Oblique line of thyroid cartilage
Insertion of thyrohyoid
Runs superiorly over thyrohyoid membrane, inserts into greater horn and body of hyoid
Nerve supply for thyrohyoid
C1 fibers via hypoglossal nerve
Action of thyrohyoid
Depresses hyoid bone or elevates larynx
Ansa Cervicalis
-nerve loop that contains fibers from ventral rami of C1 to C3 spinal nerves
Lower root of ansa cervicalis
Direct branch of cervical plexus
- contains fibers from ventral rami of C2 and C3
- passes superficial (or deep) to internal vein
- joins upper root to form ansa
Upper root of ansa cervicalis
- appears to originate from hypoglossal nerve, but contains no hypoglossal fibers
- consists of C1 fibers that join CN XII and travel with it for a distance
- separate from CN XII and form upper root of ansa cervicalis
- joins lower root to form ansa
What does ansa cervicalis give branches to?
Sternohyoid
Sternothyroid
Both bellies of omohyoid
Some C1 fibers of ansa cervicalis do what?
Continue with CN XII (after it has given off upper root) and supply thyrohyoid and geniohyoid muscles
Suprahyoid muscles
- digastric
- stylohyoid
- mylohyoid
- geniohyloid
Digastric muscle
Consists of posterior and anterior bellies connected by an intermediate tendon
Posterior belly of digastric muscle
Attaches to digastric (mastoid) notch (medial to mastoid process), runs anteriorly and inferiorly, then becomes continuous with intermediate tendon
Intermediate tendon of digastric muscle
Pierces stylohyoid and runs in fibrous sling connected to body and greater horn of hyoid, then become continuous with anterior belly
Anterior belly of digastric muscle
Runs anteriorly and superiorly, then attaches to digastric fossa of mandible
Nerve supply of posterior belly of digastric muscle
Facial nerve
Nerve supply of anterior belly of digastric muscle
Nerve to mylohyoid (branch of inferior alveolar nerve, from V3)
Action of digastric muscle
Depresses mandible and elevates hyoid bone
Origin of stylohyoid
Styloid process
Insertion of stylohyoid
Passes anteriorly and inferiorly, along superior border of posterior belly of digastric, then inserts into hyoid bone at junction of body and greater horn
Where is the stylohyoid pierced
Near its insertion by intermediate tendon of digastric
Nerve supply to stylohyoid
Facial nerve
Action of stylohyoid
Elevates hyoid bone and dares it backward
Mylohyoid
- Lies superior to anterior belly of digastric
- two mylohyoid muscles fro muscular floor of oral cavity
Origin of mylohyoid muscle
Mylohyoid line of mandible
Insertion of mylohyoid
Most posterior fibers attach to body of body of hyoid bone, rest of fibers terminate in midline raphe extending from mandible to hyoid
Nerve supply yo mylohyoid
Nerve to mylohyoid (really that’s what its called)
Actions of mylohyoid
Elevates floor of mouth during swallowing, elevates hyoid bone depresses mandible
Geniohyloid
Narrow muscle that lies above mylohyoid, in contact with corresponding opposite side
Origin of geniohyloid
Mental spine
Insertion of geniohyoid
Anterior surface of body of hyoid
Nerve supply of geniohyoid
C1 fibers via hypoglossal nerve
Actions of geniohyoid
Elevates hyoid bone and draws it forward, depresses mandible
Anterior vertebral muscles
- longus capitis
- longus colli
- rectus capitis anterior
- rectus capitis lateralis
Origin of longus capitis
Transverse processes of C3 to C6 vertebrae
Insertion of longus capitis
Inferior surface of basilar part of occipital bone
Nerve supply of longus capitis
Branches from ventral rami of C1 to C3 spinal nerve
Action of longus capitis
Flexion of head and neck
Longus Colli
Consists of 3 parts:
- inferior oblique
- superior oblique
- vertical
Inferior oblique part of longus colli
Extends from bodies of first 2 or 3 thoracic vertebrae to transverse processes of C5 and C6 vertebrae
Superior oblique part of longus colli
Extends from transverse processes of C3 to C5 vertebrae to anterior tubercle of atlas
Vertical part of longus colli
Extends from bodies of upper 3 thoracis and lower 3 cervical vertebrae to bodies C2 to C4 vertebrae
Nerve supply to longus colli
Branches from ventral rami of C2 to C6 spinal nerves
Action of longus colli
Flexion of neck
Rectus capitis anterior
Located posterior to upper part of longus capitis
Origin of rectus capitis anterior
Anterior surface of lateral mass of atlas and root of its transverse process
Insertion of rectus capitis anterior
Inferior surface of basilar part of occipital bone, immediately anterior to occipital condyle
Nerve supply to rectus capitis anterior
Branches from loop between ventral rami of C1 and C2 spinal nerves
Action of rectus capitis anterior
Flexion of head
Origin of rectus capitis lateralis
Upper surface of transverse process of atlas
Insertion of rectus capitis lateralis
Inferior surface of jugular process of occipital bone
Nerve supply to rectus capitis lateralis
Branches from loop between ventral rami of C1 and C2 spinal nerves
Action of rectus capitis lateralis
Lateral flexion of head to same side of contracting muscle
Subdivisions of the anterior triangle
- submandibular (digastric) triangle
- carotid triangle
- muscular triangle
- submental triangle
Anterior boundaries of submandibular triangle
Anterior belly of digastric
Posterior boundary of the submandibular triangle
Psotieror belly of digastric and stylohyoid
Superior boundary of submandibular triangle
Inferior border of body of mandible
Floor boundary of submandibular triangle
Mylohyoid and hypoglossal muscles
Contents of the submandibular triangle
- submandibular gland (superficial part)
- facial vessels
- submandibular lymph nodes
- hypoglossal nerve
- mylohyoid nerve and vessels
Anterior and superior carotid triangle boundary
Posterior belly of digastric
Anterior and inferior boundary of the carotid triangle
Superior belly of the omohyoid
Posterior boundary of the carotid triangle
Anterior border of sternocleidomastoid
Arteries of the carotid triangle
- common carotid
- initial segments of external and internal carotid
- some branches of external carotid
Veins of the carotid triangle
-internal jugular vein and some of its tributaries
Nerves of the carotid triangle
- vagus
- accessory
- hypoglossal
- ansa cervicalis
- internal and external laryngeal
Lymph nodes of the carotid triangle
Deep cervical lymph nodes
Anterior boundaries of the muscular triangle
Anterior midline of the neck
Posterior and superior boundary of the muscular triangle
Superior belly of omohyoid
Posterior and superior muscular triangle
Anterior border of sternocleidomastoid
Contents of the muscular triangle
- sternohyoid and sternothyroid muscles
- viscera of the neck (thyroid and parathyroid glands, larynx, trachea)
Lateral boundary of the submental triangle
Anterior bellies of the digastric muscles
Inferior border of the submental triangle
Body of hyoid
Floor boundary of the submental triangle
Mylohyoid muscles
Contents of the submental triangle
- submental lymph nodes
- small veins that join to form anterior jugular veins
