Waldeyer's ring is a ring of lymphoid tissue located in the nasopharynx and oropharynx at the entrance to the aerodigestive tract.
The structures composing this ring are:
palatine tonsils (also called the faucial tonsils)
adenoid tonsils (nasopharyngeal tonsils)
the lateral ba...
Warthin tumors, also known as lymphomatous papillary cystadenomas, are benign, sharply demarcated tumors of the salivary gland. They are of lymphoid origin and most commonly arise from parotid gland tail. They may be bilateral or multifocal in up to 20% of cases and are the most common neoplasti...
The World Health Organization (WHO) classification of head and neck tumors is the most widely used pathologic classification system for such disorders. The current revision, part of the 4th edition of the WHO series, was published in 2017 and is reflected in the article below 1.
Widening of the diploic space refers to expansion of the spongy or cancellous bone between the inner and outer tables of the calvarium. The diploic space is the medullary cavity of the skull, and a location of normal physiologic hematopoiesis in adults. Thus, expansion of this structure most com...
Widow's peak hair anomaly refers to a frontal hairline projection.
Prominent V-shaped hairline projection. Ocular hypertelorism might be...
Williams syndrome (WS) is characterized by some or all or the following features:
craniofacial dysmorphism (e.g. elfin facies)
short stature (50% of cases)
mild to moderate mental retardation
supravalvular aortic stenosis 2
pulmonary artery stenosis 3
Wolff-Chaikoff effect is an autoregulatory phenomenon, whereby a large amount of ingested iodine acutely inhibits thyroid hormone synthesis within the follicular cells, irrespective of the serum level of thyroid-stimulating hormone (TSH) 1.
The Wolff-Chaikoff effect is thought to be...
Woodruff plexus is a venous plexus located in the posterior end of the inferior meatus 1. It accounts for between 5-10% of epistaxis and are associated with hypertension. These bleeds typically do not respond to anterior nasal packing.
Wormian bones (a.k.a. intrasutural bones) is the name given to the additional small bones sometimes found between the cranial sutures of the bones of the skull vault, most commonly in relation to the lambdoid suture. Some reserve the term Wormian bones to just the intrasutural bones proximate to...
Xerostomia is the medical term for a dry mouth, and is most commonly due to hyposalivation.
Xerostomia is the most frequently observed salivary abnormality in clinical practice 1.
dryness of the mouth
vocalisation difficulties: to...
Young syndrome shares similar clinical and radiological findings to primary ciliary dyskinesia and cystic fibrosis, however, the underlying pathogenesis is yet to be fully elucidated. Obstructive azoospermia at the level of the epididymis is thought to be the cause of infertility. The commonly r...
Zenker diverticulum, also known as a pharyngeal pouch, is a posterior outpouching of the hypopharynx, just proximal to the upper esophageal sphincter through a weakness in the muscle layer called the Killian dehiscence.
More than 50% of the affected patients present in 60-80 years...
Zimmerman-Laband syndrome is a rare congenital syndrome, characterized primarily by gingival hypertrophy and skeletal abnormalities.
The molecular basis of the syndrome is currently unknown. An autosomal dominant mutation with high mutation rate and rare instances of germinal mosaic...
Zuckerkandl tubercles are the projections of normal thyroid tissue from the posterior or posteromedial margin of the thyroid gland that extend posterior to the tracheoesophageal groove. They are present in most patients and occur more commonly on the right and in the longitudinal center 50% of t...
The zygoma (also known as zygomatic bone or malar bone) is an important facial bone which forms the prominence of the cheek. It is roughly quadrangular in shape.
Zygoma has three surfaces, five borders, and two processes.
anterolateral surface is convex, pierced at its...
The zygomatic arch is formed by the union of the temporal process of the zygomatic bone and the zygomatic process of the temporal bone at the zygomaticotemporal suture.
Le Fort type 3 fracture
zygomaticomaxillary complex fracture
The zygomatic nerve is a main branch of the maxillary division of the trigeminal nerve. It should not be confused with the zygomatic branch of the facial nerve.
The zygomatic nerve divides off the maxillary division just after emerging from the foramen rotundum to enter the ptery...
The zygomaticofacial foramen is a small foramen in the mid lateral surface of the zygomatic bone that transmits the zygomaticofacial nerve (a branch of the zygomatic nerve from the maxillary division of the trigeminal nerve) and zygomaticofacial vessels.
The zygomaticofacial nerve is the smaller of the two branches of the zygomatic nerve, from the maxillary division of the trigeminal nerve. It is sometimes referred to as the malar branch of the zygomatic nerve. It leaves the inferolateral aspect of the extraconal space of the orbit through the z...
Zygomaticomaxillary complex (ZMC) fractures, also known as tripod, tetrapod, quadripod, malar or trimalar fractures, are seen in the setting of traumatic injury to the face. They comprise fractures of the:
inferior orbital rim, and anterior and posterior maxillary sinus walls
The zygomaticomaxillary suture is between the zygomatic process of the maxilla and the maxillary process of the zygomatic bone. They are often involved in zygomaticomaxillary complex (ZMC) fractures.
The zygomaticotemporal foramen is a small foramen in the anteromediall surface of the zygomatic bone that transmits the zygomaticotemporal nerve (a branch of the zygomatic nerve from the maxillary division of the trigeminal nerve) and zygomaticotemporal vessels.
The zygomaticotemporal nerve is the larger of the two branches of the zygomatic nerve, from the maxillary division of the trigeminal nerve. It is primarily sensory but also relays parasympathetic fibers to the lacrimal nerve from the pterygopalatine ganglion which reach the lacrimal gland. It le...
Zygomaticus major is a member of the buccolabial muscle group of the upper lip1. It joins with the fibers of levator anguli oris, orbicularis oris and the more deeply placed muscular bands to move the side of the mouth upwards and sideways during facial movements such as laughing.
Zygomaticus minor is a member of the buccolabial muscle group. Together with levator labii superioris alaeque nasi and levator labii superioris it is one of the main elevators of the lip, exposing the maxillary teeth 1. Along with its other action of deepening and elevating the nasolabial furro...