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The human eye is a sensory organ whose primary function is vision. They eye has a spheroidal shape and is structured in 3 layers: a supporting outer fibrous layer, a middle vascular layer, and an inner neural layer. The eye can also be subdivided into 3 compartments: the anterior, posterior, and vitreous chambers. Surrounding the eyeball itself are the extraocular muscles, the lacrimal apparatus, various nerves and vessels, and the bony structure of the orbit. Light travels through the compartments of the eye to focus on the retina, which is the location where photoreceptors convert the stimulus into a neural impulse that is carried by the optic nerve to the brain.

Salivary Glands

The salivary glands are exocrine glands positioned in and around the oral cavity. These glands are responsible for secreting saliva into the mouth, which aids in digestion. Saliva helps keep the oral mucosa lubricated, and it provides antimicrobial protection. There are 3 major paired salivary glands: the sublingual, submandibular, and parotid glands. There are also hundreds of minor salivary glands found in patches around the oral cavity.

Muscles of the Neck

The muscles of the neck can be divided into 3 groups: anterior, lateral, and posterior neck muscles. Each of the groups is subdivided according to function and the precise location of the muscles. The muscles of the neck are mainly responsible for the movements of the head (i.e., extension, flexion, lateral flexion-extension, and rotation), but the deep muscles also contribute to more intricate functions (i.e., speaking and swallowing).

Triangles of the Neck

The neck is considered to be quadrangular. This shape is the basis to study various components of the neck and their relations. The boundaries of the quadrangular shape include the mandible, upper border of the clavicle, midline of the neck, and anterior margin of the trapezius. The quadrangular shape is divided into an anterior and posterior triangle by the sternocleidomastoid muscle (SCM). The anterior and posterior triangles are the 2 primary subdivisions and are delineated by easily recognized anatomic structures. Each triangle houses muscles, nerves, vasculature, lymphatics, and adipose tissue.

Anatomy of the Ear

The ear is a sensory organ responsible for the sense of hearing and balance. Anatomically, the ear can be divided into 3 parts: the outer ear, the middle ear, and the inner ear. The outer ear consists of the auricle and ear canal. The middle ear houses the tympanic structures and ossicles, which are responsible for the detection and initial transmission of sound. Finally, the inner ear contains the bony labyrinth, along with other structures essential for spatial orientation, hearing, and balance.

Olfaction

Olfaction represents an ancient, evolutionarily critical physiologic system. Humans have the ability to detect and discriminate at least 10,000 different odorants. The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction is responsible for the detection of hazards, pheromones, and food.

Oral Cavity: Palate

The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. The palate is formed between weeks 7 and 10 of gestation, and deformities of this structure (cleft palate) are usually relevant because of its role in feeding, especially in infants.

Pharynx

The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. The muscles of the pharynx receive innervation from the vagus and glossopharyngeal nerve to propel food from the oral cavity into the esophagus.

Nose and Nasal Cavity: Anatomy

The nose is the human body's primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. There are 12 cranial bones that contribute to the structure of the nose's walls and nasal conchae.

The Visual Pathway and Related Disorders

The primary visual pathway consists of a relay system, beginning at the retina, whose ganglion cell axons form the optic nerve. The optic nerve fibers from each eye hemidecussate in the optic chiasm (OC), with nasal fibers joining the temporal fibers of the contralateral nerve. The nasal fibers continue as the optic tract on each side, synapsing with the lateral geniculate nucleus (LGN) of the thalamus. Signals are then transmitted to the primary visual cortex of the occipital lobe. The right and left visual fields are processed by opposite hemispheres. Lesions along the pathway result in vision loss or visual field deficits. Based on the type of presentation, the location of the lesion in the pathway can be ascertained.

Vertebral Column

The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. The vertebral column is the foundation for the trunk, provides an attachment for muscles and ligaments, and protects the spinal cord and nerve roots.

Head and Neck Examination

The head and neck examination is the portion of the physical examination done to observe for signs of head and neck disease or illness. The head and neck examination consists of inspection, palpation, and auscultation. The information gathered from the physical examination of the head and neck, along with the information from the history, is used by the physician to generate a differential diagnosis and treatment plan for the patient.

Paranasal Sinuses

The 4 pair of paranasal sinuses include the maxillary, ethmoid, sphenoid, and frontal sinuses. The sinuses are a group of air-filled cavities located within the facial and cranial skeleton; all are connected to the main nasal cavity and nasopharynx. Functions include contributing to voice resonance, reducing the skull weight to facilitate an upright head position, conditioning (warming and humidifying) inhaled air, and maximizing the surface of the nasal mucosa.

Overview of the Cranial Nerves

There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. Some CNs are involved in special senses, like vision, hearing, and taste, and others are involved in muscle control of the face. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain.

Muscles of the Face

The facial muscles (also called mimetic muscles) control facial expression and are supplied by the facial nerve. Most of them originate from the skull and attach to the skin around the facial openings, which serve as a method to group or classify them. Also located within the face are the masticatory muscles, which move the temporomandibular joint, allowing for mastication and the initial stages of digestion.

Oral Cavity: Lips and Tongue

The lips are the soft and movable most external parts of the oral cavity. The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. Together, these structures play an important role in each of these vital processes. The blood supply of the lips and tongue originates from the external carotid artery, and the innervation is through cranial nerves.

Skull

The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. The neurocranium is further subdivided into the calvarium (the skullcap) and the base of the skull (the cranial fossa).

Teeth

Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are located within the alveolar processes and are held in position by the periodontal ligament. Teeth are composed of enamel, dentin, and dental cement.

Cerebrovascular System

Blood supply to the brain can be divided into an anterior and a posterior circulation, which interconnect to form the circle of Willis. The anterior circulation is derived from the internal carotid arteries and consists mainly of the anterior and middle cerebral arteries. The posterior circulation is derived from the vertebral arteries and consists primarily of the cerebellar and posterior cerebral arteries. The primary venous drainage of the brain occurs via the internal jugular vein.

Larynx

The larynx, also commonly called the voice box, is a cylindrical space located in the neck at the level of the C3–C6 vertebrae. The larynx is continuous superiorly with the oropharynx and inferiorly with the trachea. This structure is made up of 9 cartilages that are connected by membranes, ligaments, and muscles and that house the vocal cords. The major structures forming the framework of the larynx are the thyroid cartilage, cricoid cartilage, and epiglottis. The larynx serves to produce sound (phonation), conducts air to the trachea, and prevents large molecules from reaching the lungs.

The Orbit and Extraocular Muscles

The orbit is the cavity of the skull in which the eye and its appendages are situated. The orbit is composed of 7 bones and has a pyramidal shape, with its apex pointed posteromedially. The orbital contents comprise the eye; orbital and retrobulbar fascia; extraocular muscles; cranial nerves II, III, IV, V, and VI; blood vessels; fat; lacrimal gland with its sac and nasolacrimal duct; eyelids; palpebral and suspensory ligaments; ciliary ganglion; and short ciliary nerves.

Skull 00:51 h / 14 videos 3 free

Skull 1 concept page 1 free

Skull 33 quiz questions 6 free
Muscles of the Head 00:13 h / 3 videos

Muscles of the Head 1 concept page 1 free

Muscles of the Head 10 quiz questions 0 free
Upper Aerodigestive Tract 00:50 h / 10 videos 2 free

Upper Aerodigestive Tract 7 concept pages 7 free

Upper Aerodigestive Tract 33 quiz questions 6 free
Special Senses 00:59 h / 10 videos 2 free

Special Senses 4 concept pages 4 free

Special Senses 38 quiz questions 5 free
Neurovasculature of the Head 00:22 h / 16 videos 3 free

Neurovasculature of the Head 3 concept pages 3 free

Neurovasculature of the Head 22 quiz questions 4 free
Neck Anatomy 00:26 h / 7 videos 1 free

Neck Anatomy 2 concept pages 2 free

Neck Anatomy 19 quiz questions 3 free

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Head and Neck Anatomy

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Your Educators of course Head and Neck Anatomy

Darren Salmi, MD, MS

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