Human Anatomy: Head & Neck

Comprehensive vocabulary flashcards covering the anatomy of the scalp, face, masticatory system, anterior/posterior neck muscles, tongue musculature, cranial nerves, and craniocervical joints.

Scalp

The soft tissue covering the skull vault, extending from the forehead and supraorbital margins anteriorly to the external occipital protuberance and superior nuchal lines posteriorly, and laterally to the superior temporal line.

Layers of the Scalp (SCALP)

Anatomical layers of the scalp represented by the mnemonic: Skin, Connective tissue (dense layer containing blood vessels and nerves), Aponeurosis (epicranial aponeurosis/galea aponeurotica), Loose areolar tissue (allows movement of superficial scalp layers), and Pericranium (periosteum of the outer skull).

Occipitofrontalis Muscle

A scalp muscle consisting of a frontal belly and an occipital belly linked by the epicranial aponeurosis; elevates the eyebrows and produces horizontal forehead wrinkles, innervated by the facial nerve (CN VII).

Layers of the Face

The four structural layers of the face from superficial to deep: 1. Skin, 2. Superficial fascia (contains muscles of facial expression, blood vessels, and nerves), 3. Deep fascia (absent except in limited parts), and 4. Facial bones.

Orbicularis Oculi Muscle

A circular facial muscle surrounding the orbital margin that closes the eye firmly and suddenly in danger; innervated by the temporal and zygomatic branches of the facial nerve (CN VII).

Buccinator Muscle

The muscle of the cheek innervated by the buccal branch of the facial nerve (CN VII); functions in blowing and whistling, while preventing food accumulation in the oral vestibule and saliva dribbling from the mouth angle.

Orbicularis Oris Muscle

The muscle of the lips that regulates lip movements and serves as a sphincter to close the mouth; innervated by the buccal and mandibular branches of the facial nerve (CN VII).

Ophthalmic Division ($V_1$)

The first and smallest division of the trigeminal nerve (CN V); a purely sensory nerve supplying the forehead, upper eyelid, cornea, and dorsum of the nose.

Maxillary Division ($V_2$)

The second division of the trigeminal nerve (CN V); a purely sensory nerve providing sensory innervation to the midface, lower eyelid, cheek, side of the nose, upper lip, and upper teeth.

Mandibular Division ($V_3$)

The third and mixed division of the trigeminal nerve (CN V); provides motor supply to the four muscles of mastication, anterior belly of digastric, mylohyoid, tensor palati, and tensor tympani, and sensory supply to the lower face, lower lip, chin, auricle, temporal region, and anterior $\frac{2}{3}$ of the tongue.

Terminal Branches of the Facial Nerve

Five motor branches arising within the parotid gland: Temporal (supplies frontalis/forehead), Zygomatic (supplies orbicularis oculi), Buccal (supplies cheek/upper lip/nose), Marginal mandibular (supplies lower lip and chin), and Cervical (supplies platysma).

Bell's Palsy

Unilateral weakness or paralysis of facial muscles due to damage to the facial nerve (CN VII); presents with loss of forehead wrinkles, inability to raise the eyebrow, difficulty closing the eye, flattened nasolabial fold, drooping corner of the mouth, and difficulty whistling or smiling.

Muscles of Mastication

A group of four muscles acting on the temporomandibular joint and innervated by the mandibular nerve ($V_3$): temporalis, masseter, lateral pterygoid, and medial pterygoid.

Temporalis Muscle

A muscle of mastication situated on the lateral surface of the skull that acts to elevate and retract the mandible.

Masseter Muscle

A muscle of mastication located on the lateral surface of the ramus of the mandible that elevates and protrudes the mandible.

Lateral Pterygoid Muscle

A muscle of mastication lying deep to the ramus of the mandible that depresses the mandible and produces side-to-side and protrusive movements.

Medial Pterygoid Muscle

A muscle of mastication located deep to the lateral pterygoid muscle that acts to elevate the mandible and assist in side-to-side movements.

Trismus

Difficulty or inability to open the mouth, commonly associated with spasm of the muscles of mastication.

Sternocleidomastoid Muscle

An oblique neck muscle originating from the manubrium and medial clavicle and inserting onto the mastoid process and superior nuchal line; innervated by the spinal accessory nerve (CN XI); unilaterally bends the head to the same side and rotates the face to the opposite side, and bilaterally flexes the neck.

Scalene Muscles

A group of three lateral neck muscles (scalenus anterior, scalenus medius, scalenus posterior) that connect cervical transverse processes to the first and second ribs; assist in deep inspiration and produce lateral flexion of the neck.

Digastric Muscle

A suprahyoid muscle featuring two bellies linked by an intermediate tendon attached to the hyoid; the anterior belly originates from the digastric fossa (supplied by nerve to mylohyoid) and the posterior belly from the mastoid process (supplied by CN VII); depresses the mandible and elevates the hyoid during swallowing.

Mylohyoid Muscle (Diaphragma Oris)

A suprahyoid muscle originating from the entire length of the mylohyoid line of the mandible and inserting into the mylohyoid raphe and hyoid body; forms the floor of the mouth, elevates the hyoid and oral floor, depresses the mandible, and is innervated by the nerve to mylohyoid.

Intrinsic Muscles of the Tongue

Four muscles contained entirely within the tongue that act to alter its shape: superior longitudinal (shortens tongue, curls apex upward), inferior longitudinal (shortens tongue, curls apex downward), transverse (narrows and elongates tongue), and vertical (flattens and broadens tongue); innervated by CN XII.

Extrinsic Muscles of the Tongue

Four muscles originating outside the tongue that insert into it to alter its position: genioglossus, hyoglossus, styloglossus, and palatoglossus.

Genioglossus Muscle

An extrinsic tongue muscle originating from the genial tubercle of the mandible that acts to protrude and depress the tongue; innervated by the hypoglossal nerve (CN XII).

Hyoglossus Muscle

An extrinsic tongue muscle originating from the body and greater horn of the hyoid bone that acts to depress and retract the tongue; innervated by the hypoglossal nerve (CN XII).

Styloglossus Muscle

An extrinsic tongue muscle originating from the styloid process of the temporal bone that retracts and elevates the tongue; innervated by the hypoglossal nerve (CN XII).

Palatoglossus Muscle

An extrinsic tongue muscle originating from the soft palate that elevates the posterior tongue and helps close the oropharyngeal isthmus; innervated by the vagus nerve (CN X), making it the only tongue muscle not supplied by CN XII.

Infrahyoid Muscles

Four strap muscles arranged in superficial (sternohyoid, superior belly of omohyoid) and deep (sternothyroid, thyrohyoid) planes below the hyoid bone; depress the hyoid bone and thyroid cartilage during swallowing.

Ansa Cervicalis

A nerve loop in the anterior neck formed by branches of the cervical plexus ($C_1 - C_3$); provides motor innervation to the infrahyoid strap muscles, except the thyrohyoid which is supplied directly by $C_1$.

Anterior Vertebral Muscles

Prevertebral neck muscles (longus colli, longus capitis, rectus capitis anterior, rectus capitis lateralis) innervated by cervical ventral rami that primarily act to flex the head and neck.

Trapezius Muscle

The large superficial muscle constituting the first layer of the back of the neck; extends the neck/head, rotates the head, and moves the scapula; innervated by the spinal root of the accessory nerve (CN XI).

Splenius Muscles

The second layer of posterior neck muscles consisting of splenius capitis (retracts the head and rotates it to the same side) and splenius cervicis (extends the neck and rotates the cervical spine).

Suboccipital Muscles

Four short deep muscles of the posterior neck (rectus capitis posterior major, rectus capitis posterior minor, superior oblique, and inferior oblique) connecting atlas and axis to each other and the occipital bone; act to extend the head and rotate the atlas on the axis.

Glossopharyngeal Nerve (CN IX)

A mixed cranial nerve arising from the medulla; provides motor innervation to the stylopharyngeus, parasympathetic fibers to the parotid gland via the tympanic branch, and sensory/taste fibers to the posterior $\frac{1}{3}$ of the tongue.

Vagus Nerve (CN X)

The longest cranial nerve, arising from the medulla and traversing the head, neck, thorax, and abdomen; regulates swallowing, voice, pharyngeal/laryngeal musculature, and visceral parasympathetics.

Accessory Nerve (CN XI)

A motor cranial nerve with a cranial root (joins CN X to supply pharyngeal, laryngeal, and palatal muscles) and a spinal root (supplies the sternocleidomastoid and trapezius muscles).

Hypoglossal Nerve (CN XII)

A purely motor cranial nerve that supplies motor innervation to all intrinsic and extrinsic muscles of the tongue, except the palatoglossus.

Atlanto-Occipital Joint

An ellipsoid synovial joint between the occipital condyles and the superior articular facets of the atlas ($C_1$); reinforced by anterior and posterior atlanto-occipital membranes to enable flexion and extension (the 'YES' nodding movement).

Median Atlanto-Axial Joint

A pivot synovial joint between the dens (odontoid process) of $C_2$ and the anterior arch of $C_1$, secured by the transverse ligament of the atlas; facilitates axial rotation (the 'NO' head movement).

Lateral Atlanto-Axial Joints

Two plane synovial joints formed between the inferior articular facets of the lateral masses of the atlas ($C_1$) and the superior facets of the axis ($C_2$).

Transverse Ligament of the Atlas

A critical ligament arching across the atlas that secures the dens of the axis against the anterior arch of $C_1$, stabilizing the median atlanto-axial pivot joint.