Head Anatomy

Description

Anatomy illustration of the human skull

A, Lateral aspect of cranium. B, Superior aspect of cranial base.

Main facial expression muscles of face and key facial areas division

Muscles of mastication

Tongue muscles

Extra occular muscles

The Temporomandibular Joint

Anatomy of cranial nerves. a Pathways of cranial nerves to various innervated tissues of the body

Primary and permanent dentition

Definition

• Head refers to the upper most part of the human body
• Includes the skull, brain, bones, sensory organs, muscles, neurovascular

Areas of the Head

• Scalp
  • Overlies the skull
  • Consists of 5 layers: skin, connective tissue (dense), aponeurosis, loose connective tissue and the periosteum
  • Aponeurosis acts like a tendon with the Frontalis and Occipitalis muscles
  • Receives a rich arterial supply from the external carotid artery
  • Innervation comes the Trigeminal nerve and other cranial nerves
• Infratemporal Fossa
  • Complex area located at the base of the skull
  • It is deep to the masseter muscles
  • Provides a conduit for neurovascular structures entering/leaving the cranium
  • Key structures: mandibular nerve, chorda tympani, otic ganglion, maxillary artery, pterygoid venous plexus, maxillary vein, middle meningeal artery
  • Muscles: lateral pterygoid, medial pterygoid
• Pterygopalantina Fossa
  • Deep to the infratemporal fossa
  • Extends to the nasal cavity
  • Contents: maxillary nerve and its branches, the pterygopalatine ganglion, as well as the maxillary artery and its branches
• Cranial Fossa
  • Can be broken down to anterior, middle, posterior
  • Each accomodates/supports different parts of the brain and transmits neurovascular structures
  • Anterior: frontal lobes, the olfactory bulb, and the anterior and posterior ethmoidal neurovascular structures
  • Middle: pituitary glands, temporal lobes, optic canals, neurovascular structures pass through the supraorbital fissure, foramen rotundum, foramen ovale and foramen spinosum
  • Posterior: brainstem, cerebellum

Bones of the Skull

• There are 22 bones which can be divided into the cranium and facial skeleton
• The cranium encloses and protects the brain
• The facial bones support the soft tissue of the face
• Cranial roof
  • Bones: frontal, occipital, two parietal bones
  • Also known as the calvarium
• Cranial base
  • Bones: frontal, sphenoid, ethmoid, occipital, parietal, and temporal bones
  • Articulate with 1st cervical vertebra (atlas), the facial bones, and the mandible (jaw)
• Facial Bones
  • Zygomatic (2)
  • Lacrimal (2)
  • Nasal (2)
  • Inferior nasal conchae (2)
  • Palatine (2)
  • Maxilla (2)
  • Mandible (jaw)

Muscles of the Head

• Muscles of Facial Expression
  • Scalp/Forehead: Frontalis, Occipitalis
  • Eyes/Eyelids: Orbicularis oculi, Corrugator supercilii, Levator palpebrae superioris
  • Nose: Nasalis, Procerus, Depressor Septi Nasi
  • Mouth/Lips: Orbicularis oris, Buccinator, Risorius, Zygomaticus major, Zygomaticus minor, Levator labii superioris, Levator anguli oris, Depressor anguli oris, Depressor labii inferioris, Mentalis
  • Neck: Platysma
• Muscles of Mastication
  • Masseter
  • Temporalis
  • Medial Pterygoid
  • Lateral Pterygoid
• Muscles of the Tongue
  • Intrinsic: superior longitudinal, inferior longitudinal, transverse and vertical muscles of the tongue
  • Extrinsic: Genioglossus, Hyoglossus, Styloglossus, Palatoglossus
• Extra Ocular Muscles
  • Rectus: Superior rectus, Inferior rectus, Medial rectus, Lateral rectus
  • Accessory Muscle: Levator palpebrae superioris

Nerves of the Head

• Sympathetic Innervation
  • Begins in the spinal cord, enter the sympathetic chain of the cervical ganglion
  • Hitch hike into the neck with other nerves and arteries
  • Responsible for "fight or flight" response
• Parasympathetic Innervation
  • Originate in 4 nuclei located in the brainstem
  • 4 key ganglion: ciliary, otic, pterygopalatine and submandibular
  • Responsible for "rest and digest" response
• Trigeminal nerve
  • Major sensory nerve of the face, also muscles of mastication
  • Ophthalmic (V1): upper forehead and eyelid
  • Maxillary (v2): lower eyelid to upper palate
  • Mandibular (V3): lower third of face and jaw, muscles of mastication

Organs of the Head

• Ears
  • External ear: captures and directs sound to the inner ear
  • Middle ear: tympanic membrane separates external from middle, transmits vibrations via the auditory ossicles
  • Inner ear: vibrations cause movements of ossicles, transmitted to inner ear through oval window
• Eyes
  • Responsible for vision
  • Light enters through pupil, controlled by ciliary muscles
  • Rods/cones, detect light and pass the signal through the retina to optic nerve
• Nose/Sinuses
  • External nose: opens the nasal cavity through nostrils
  • Inner nose: 3 pairs of turbinates which humidify inspired air
  • Nasal cavity drains into 4 pairs of paranasal sinuses (frontal, sphenoid, ethmoid, maxillary)
• Salivary Glands
  • Located in the mouth with 3 pairs of exocrine glands
  • Parotid, submandibular, subinguinal
• Oral Cavity
  • Marks the start of the gastrointestinal tract
  • Major functions: digestion, communication, breathing
  • Roof: hard/soft palates
  • Floor: tongue, salivary glands, hyoid muscles

Joints of the Head

• Temporomandibular Joint: formed by the articulation of the mandible and temporal bones
• Primary joint for communication and mastication

Cranial Nerves

• 12 paired nerves that arise directly from the brain
• Provide majority of motor/sensory innervations of the head

Child and Adult Dentition

• Composed of two sets of teeth, primary (child) and permanent (adult)
• Organized into two opposing arches: maxillary (upper) and mandibular (lower)
• Can be further divided into left and right halves
• Positioned in alveolar sockets, connected to bone by periodontal ligament

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See Also

• HEENT Anatomy Main
• Anatomy Main
• HEENT Main

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