AN43.1-9 | Head & neck Joints, Histology, Development, Radiography & Surface marking — Glossary

Bilateral ellipsoid synovial joint between occipital condyles and atlas; permits nodding (flexion-extension) but NO rotation

Three joints (two lateral synovial + one median) allowing rotation (shaking 'no'); contributes 50% of total cervical rotation

Most important stabiliser of the atlantoaxial joint; keeps the dens against the anterior arch of atlas; rupture threatens spinal cord compression

Distance between the anterior arch of atlas and the dens on lateral cervical X-ray; normal ≤3 mm in adults, ≤5 mm in children

Six paired mesenchymal thickenings in the embryonic head (5th vestigial); each gives rise to specific skeletal, muscular, neural, and arterial derivatives

Congenital defect from failure of fusion of the maxillary process with the medial nasal process; usually paramedian, lateral to the philtrum

Congenital defect from failure of fusion of the palatine shelves with each other, the primary palate, or the nasal septum

Embryological tract from the foramen caecum to the thyroid gland passing through the hyoid body; normally obliterates; persistence causes thyroglossal cyst

Ectodermal diverticulum from the stomodeum roof giving rise to the adenohypophysis (anterior pituitary); craniopharyngioma arises from its remnants

Cells between thyroid follicles secreting calcitonin; derived from the neural crest via the ultimobranchial body (4th pharyngeal pouch)

Small dark-staining cells of the parathyroid gland that secrete parathyroid hormone (PTH) for calcium homeostasis

Larger acidophilic cells of the parathyroid gland appearing after puberty; function uncertain; rich in mitochondria

Swollen axon terminals in the posterior pituitary containing stored oxytocin and ADH (vasopressin)

Turkish saddle depression in the body of the sphenoid housing the pituitary gland; visible on lateral skull X-ray

Soft tissue anterior to the cervical vertebrae on lateral X-ray; widening (>7 mm at C2, >22 mm at C6) suggests retropharyngeal abscess or haematoma

Septic thrombosis of the cavernous sinus from facial infection spread via valveless veins; causes proptosis, ophthalmoplegia, and potentially death

Region around the nose and upper lip where infection can spread via valveless veins to the cavernous sinus

Non-traumatic atlantoaxial subluxation in children from ligamentous laxity due to head and neck infection (retropharyngeal abscess, tonsillitis)

Lax transverse ligament from connective tissue hypotonia in trisomy 21; requires cervical X-ray screening before contact sports

Ectopic thyroid tissue at the foramen caecum from failure of descent; may be the only functioning thyroid tissue

H-shaped junction of frontal, parietal, temporal, and sphenoid bones; thinnest skull point overlying the middle meningeal artery