Head and Neck Anatomy

• These notes cover the anatomy, physiology, and pathology of the head, neck, and regional lymphatics.

Cranial and Facial Structures

• The cranial bones include the frontal, parietal, occipital, and temporal bones which protect the brain.
• Cranial sutures, such as the coronal, sagittal, and lambdoid sutures, are the lines where the cranial bones join.
• The facial nerve (CN VII) controls the muscles responsible for facial expression.
• The trigeminal nerve (CN V) has sensory and motor functions in the temporomandibular joint (TMJ).

Glands of the Head and Neck

• The parotid glands, the largest salivary glands, are located in the cheeks over the mandible, anterior to and below the ear, and are normally non-palpable.
• The submandibular glands are located beneath the mandible at the angle of the jaw.
• The sublingual glands are found on the floor of the mouth.
• The thyroid gland, an endocrine gland with two lobes, creates and secretes T3 and T4 hormones to regulate metabolism.
• The thyroid cartilage, also known as the Adam's apple, sits above the cricoid cartilage, which is the upper tracheal ring and isthmus of the thyroid gland.

Neck Structures

• Key structures include the vessels (such as the carotid arteries and jugular veins), muscles, nerves, lymphatics, and viscera of the respiratory and digestive systems.
• The internal carotid artery supplies blood to the brain.
• The external carotid artery supplies blood to the face, salivary glands, and superficial temporal area.
• The spinal accessory nerve (CN XI) controls the sternomastoid and trapezius muscles.
• The sternomastoid muscle enables head rotation and flexion and divides the neck into anterior and posterior triangles.

Lymphatic System

• The lymphatic system absorbs excess fluid and plasma proteins from the interstitial space, returning them to the bloodstream.
• The lymphatic system plays a role in immunity, and also absorbs lipids from the digestive tract.
• Lymph nodes are small oval clumps of lymphatic tissue along lymphatic vessels.
• The spleen, located in the left upper quadrant (LUQ), destroys old blood cells, produces antibodies, stores red blood cells (RBCs), and filters microorganisms from the blood.
• Tonsils, located at the entrance to the respiratory and gastrointestinal (GI) tracts, respond to local inflammation.
• The thymus gland, located in the upper chest, is where T cells mature.

Lymphatic System Conditions

• Acute lymphangitis involves inflammation/activation of the lymphatic system, often related to colds or allergies.
• Hodgkin's and non-Hodgkin's lymphoma are types of lymphatic cancer with symptoms similar to a cold or virus.
• The Epstein-Barr virus (EBV) causes mononucleosis.
• Streptococcal pharyngitis is strep throat.
• A retropharyngeal abscess is an emergency that can cause drooling, voice changes, and airway occlusion.
• Rheumatoid arthritis (RA) is an autoimmune disease that attacks joints.
• Cat scratch fever is a systemic infection that causes red streaks and can lead to sepsis.
• AIDS (acquired immunodeficiency syndrome) is progressed HIV with severely compromised immunity.
• Lymphedema is swelling caused by an abnormal accumulation of lymph fluid within tissues, often due to a lack of lymph nodes in the area.

Lymph Node Locations

• Preauricular nodes are located in front of the ear.
• Postauricular nodes are superficial to the mastoid process.
• Occipital nodes are at the base of the skull.
• Submental nodes are midline, behind the tip of the mandible.
• Submandibular nodes are halfway between the angle and the tip of the mandible.
• Sublingual nodes are located under the tongue.
• Retropharyngeal (tonsillar) nodes are located under the angle of the mandible.
• The anterior cervical chain is located overlying the sternomastoid muscle.
• The posterior cervical chain runs in the posterior triangle along the edge of the trapezius muscle.
• The deep cervical chain is deep under the sternomastoid muscle.
• Supraclavicular nodes are located just above and behind the clavicle, at the sternomastoid muscle, and may indicate chest/abdominal cancer or a recent vaccine.

Developmental Considerations

• Fontanels are membrane-covered soft spots that allow growth of a baby's brain during the first year, eventually ossifying.
• The triangle-shaped posterior fontanel closes by 1-2 months.
• The diamond-shaped anterior fontanel closes between 9 months and 2 years.
• Head size reaches 90% of its final size by age 6.
• Lymphoid tissue is well developed at birth and reaches adult size by age 6.
• Facial bone growth rates involve a small mandible and maxilla, and a low nasal bridge in children.
• In adolescent boys, facial hair appears, the thyroid cartilage enlarges, and the voice deepens.
• During pregnancy, the thyroid gland may enlarge slightly due to tissue hyperplasia and increased vascularity.
• In aging adults, facial bones and orbits become more prominent, skin sags due to decreased elasticity, fat, and moisture, and the lower face may decrease in size due to tooth loss.

Headaches

• Headaches are a leading cause of acute pain and decreased productivity.
• Headaches are more common in females and more prevalent among Caucasians and Hispanics.
• Headaches are classified by etiology.
• A chronic migraine is defined as having headaches more than 15 days per month.

Normal Findings

• Normocephalic describes a round, symmetrical skull appropriately related to body size.
• Facial features should always be symmetrical.
• In a normal head and neck examination, the head position is midline, accessory neck muscles are symmetrical, and the head is erect and still.
• The trachea should be midline and should not deviate, as deviation can cause respiratory distress.
• Lymph nodes are typically not palpable during infancy but may be palpable during childhood, though they should be less than 3 mm.

Examination of Aging Adults

• Temporal arteries may appear twisted or prominent.
• Mild rhythmic head tremors may be normal.
• The lower face may appear smaller due to tooth loss.
• There may increased concave curve in the neck to compensate for kyphosis.

Abnormalities

• Hydrocephalus is an excessive accumulation of cerebrospinal fluid (CSF) in the ventricles, often treated with shunts.
• Plagiocephaly is flattening or asymmetry of the head.
• Fetal alcohol syndrome involves birth defects caused by alcohol intake during pregnancy, presenting with signs and symptoms similar to Down syndrome.
• People with hypothyroidism can present with a puffy edematous face, periorbital edema, and coarse facial features, hair, and eyebrows.
• Acromegaly is characterized by enlargement of the extremities.
• Cushing syndrome involves hypersecretion of cortisol, leading to abnormalities like a moon face and buffalo hump.
• Bell's palsy is facial nerve paralysis causing drooping.
• Parkinson syndrome causes head, neck, and tongue tremors.
• Cachetic appearance includes being underweight with sunken eyes and facial features.

Explore the intricate anatomy of the head and neck, including cranial bones, facial nerves, and major glands. Learn about the functions of the parotid, submandibular, sublingual, and thyroid glands. Understand the relationships between these structures.