Anatomy of the Skull and Head Regions

Head Regions

• The head is divided into 11 regions: frontal, parietal, occipital, temporal, orbital, nasal, infraorbital, zygomatic, buccal, oral, and mental.

Skull Bones

• The skull has two main sections: the cranium and the face.
• The cranium, composed of 8 bones, protects the brain.
• The face consists of 14 bones.

Cranium Bones

• Single bones: frontal, occipital, sphenoid, ethmoid
• Paired bones: parietal, temporal

Facial Bones (Anterior View)

• Lacrimal bone
• Nasal bone
• Vomer
• Nasal concha
• Zygomatic bone
• Maxilla
• Mandible
• Palatine bones (technically not facial)

Hyoid Bone

• The hyoid bone does not articulate with any other bone; it's suspended between the mandible and larynx.

Postnatal Development

• At birth, the cranial vault is large, while the cranial base and face are small.
• The face lacks significant vertical dimension due to unerupted teeth.
• Several skull bones fuse postnatally.
• The mandible is in two halves at birth, fusing later.

Temporomandibular Joints (TMJs)

• Located on each side of the head, allowing mandible movement for speech and chewing.
• Structure comprises the glenoid fossa, articular eminence, and condyloid process of the temporal and mandible bones.

Capsular Ligament

• Encloses the TMJ, binding the temporal bone's articular eminence and fossa to the mandibular condyle and its neck.

Articular Space

• Located between the capsular ligament and the glenoid fossa and condyle surfaces.
• Contains the articular disc (meniscus), which divides the space into upper and lower compartments.

Jaw Movement

• Hinge action: Initial phase of mouth opening, involving the lower compartment only.
• Gliding movement: Allows forward/backward jaw movement, engaging both upper and lower joint compartments. The condyle and disc glide along the articular eminence.

Temporomandibular Disorders (TMD)

• Conditions affecting one or both TMJs.
• Factors include stress, clenching, bruxism, trauma, systemic diseases, and aging.

TMD Categories

• Acute masticatory muscle complaints
• Articular disc derangement
• Extrinsic trauma
• Joint diseases
• Chronic mandibular hypermobility

TMD Symptoms

• Pain
• Joint sounds
• Limited movement

TMD Causes

• Stress
• Teeth clenching
• Bruxism
• Jaw/head/neck trauma
• Diseases (e.g., arthritis)
• Malocclusion

Muscles of the Head and Neck

• Seven major groups: neck, facial expression, mastication, floor of the mouth, tongue, soft palate, and pharynx.

Major Muscles of the Neck

• Sternocleidomastoid and Trapezius; can be painful due to improper posture during dental assisting.

Major Muscles of Facial Expression

• Orbicularis oris (closes/puckers lips)
• Buccinator (compresses cheeks, retracts mouth corner)
• Mentalis (elevates chin skin, pulls lower lip up)
• Zygomaticus major (elevates mouth corners—laughing)

Major Muscles of Mastication

• Temporalis
• Masseter
• Medial pterygoid
• Lateral pterygoid

Muscles of the Floor of the Mouth

• Digastric, mylohyoid, stylohyoid, geniohyoid

Muscles of the Tongue

• Intrinsic: shape tongue during speech, chewing, swallowing
• Extrinsic: move and position the tongue (genioglossus, hyoglossus, styloglossus, palatoglossus)

Muscles of the Soft Palate

• Palatoglossus, palatopharyngeus

Salivary Glands

• Produce saliva for lubrication, cleansing, digestion (through enzymes), and tooth remineralization.
• Classified as major or minor.

Minor Salivary Glands

• Smaller, more numerous, located in buccal, labial, lingual mucosa, soft palate, hard palate, and floor of the mouth.
• Ebner's gland is associated with large circumvallate papillae on the tongue.

Major Salivary Glands

• Parotid (Stensen's duct)
• Submandibular (Wharton's duct)
• Sublingual (Bartholin's duct)

Major Arteries of the Face and Oral Cavity

• Common carotid
• Internal carotid
• External carotid
• Facial
• Lingual
• Maxillary
• Inferior alveolar
• Pterygoid
• Pterygopalatine

Major Veins of the Face and Oral Cavity

• Maxillary vein
• Retromandibular vein
• External jugular vein
• Subclavian vein
• Facial vein
• Common facial vein
• Deep facial vein
• Lingual veins
• Internal jugular vein

Cranial Nerves

• 12 pairs, serving sensory and motor functions; named for location/function, denoted by Roman numerals.

Innervation of the Oral Cavity

• Trigeminal nerve (primary) with branches: maxillary, mandibular, ophthalmic.

Maxillary Division of the Trigeminal Nerve

• Supplies maxillary teeth, periosteum, mucous membrane, maxillary sinuses, and soft palate.
• Branches include nasopalatine, greater palatine, and superior alveolar nerves.

Mandibular Division of the Trigeminal Nerve

• Supplies buccal, lingual, inferior alveolar, mylohyoid, small dental, mental, and incisive nerves.

Lymph Nodes of the Head and Neck

• Important for extraoral examination; enlarged nodes may signal infection or cancer.
• Drain intraoral structures (teeth), eyes, ears, nasal cavity, throat.

Structure and Function of Lymph Nodes

• Small, round/oval structures in lymph vessels.
• Major sites: cervical, axillary, inguinal.
• Head lymph nodes are superficial or deep.

Superficial Lymph Nodes of the Head

• Five groups: occipital, retroauricular, anterior auricular, superficial parotid, facial.

Deep Cervical Lymph Nodes

• Located along the internal jugular vein in the neck, deep to the sternocleidomastoid muscle.

Lymphadenopathy

• Enlarged, firm lymph nodes due to increased lymphocyte size and count in lymphoid tissue, aiding disease defense.

Paranasal Sinuses

• Air-filled spaces within the skull connecting to the nasal cavity.
• Functions: produce mucus, lighten skull bones, provide resonance for sound.
• Sinuses include maxillary, frontal, ethmoid, and sphenoid.

Explore the intricate anatomy of the skull and head. This quiz covers the division of the head into regions, the bones of the cranium and face, the unique hyoid bone, and insights into postnatal skull development. Test your knowledge about these essential components of human anatomy.