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Head and neck anatomy is a fundamental area of study for medical students, providing a comprehensive understanding of the structures and functions that are vital to our senses, communication, and overall well-being. Proficiency in head and neck anatomy is crucial for success in the United States Medical Licensing Examination (USMLE).
The skull forms the bony framework of the head, protecting the brain and supporting various structures. Muscles of the head play crucial roles in facial expression, mastication, swallowing, and speaking. The upper aerodigestive tract includes the oral cavity, pharynx, and larynx, which are involved in speech, swallowing, and respiration. Special senses, including vision, hearing, and balance, are critical for our perception of the world. Neurovasculature of the head refers to the intricate network of blood vessels and nerves supplying the brain and surrounding structures. Understanding neck anatomy is vital for evaluating conditions affecting the cervical lymph nodes, thyroid gland, and structures like the trachea, esophagus, and major blood vessels. Familiarity with neck anatomy is crucial for diagnosing and managing conditions such as neck masses, thyroid disorders, and carotid artery stenosis.
Proficiency in head and neck anatomy is essential for success in the USMLE. It enables medical students to accurately interpret clinical findings, order appropriate diagnostic tests, develop treatment plans, and communicate effectively with patients and other healthcare professionals.
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.
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.
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).
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.
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 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.
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.
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.
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 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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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 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.
Dr. Salmi is a Clinical Assistant Professor of Pathology and Surgery at Stanford University.
He obtained his M.S. in Biological Sciences from Stanford University in 2005 and his M.D. from U.C. Davis in 2010. Dr. Salmi completed his Residency in Anatomic Pathology at Stanford University. He is specifically interested in autopsy and cardiovascular pathology. Due to his outstanding lecture style, he has received numerous awards for excellence in preclinical teaching.
Within Lecturio, Dr. Salmi teaches Anatomy for medical and nursing students.
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