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auditory ossicles

three small bones located in the middle ear that fit together to send sound waves from the tympanic membrane to the inner ear. In humans, these bones include the malleus (hammer), incus (anvil), and stapes (stirrup)

axial skeleton

portion of a human skeleton that is comprised of the body's longitudinal axis, or center, ranging from the skull, auditory ossicles, and hyoid bone to the vertebral column, the thoracic (rib) cage, and sternum


region at the top of the spine that includes the seven vertebrae in the neck, numbered C1–C7


triangular-shaped, bottommost region of the vertebral column

cranial cavity

space within the skull that holds the brain and meninges and relies on cerebrospinal fluids to cushion the brain from impacts


upper portion of the skull, forming a protective covering over the brain.


any of several fibrous membranes that connect an infant's developing cranial bones and cover spaces between the bones. The fontanels are gradually replaced by bone

foramen (plural, foramina)

opening or passageway that allows muscle tissues, nerves, and blood vessels to pass from one area of the body to another


single U-shaped bone that supports and anchors the tongue and provides places for muscle attachment

intervertebral disc

flattened structure that sits between and cushions vertebrae. Disks are composed of a fibrocartilage ring, the annulus fibrosus, surrounding a gelatinous center, the nucleus pulposus.


abnormal spinal curvature that takes the form of an exaggerated concave bend in the vertebral column's thoracic region, resulting in a hunched back


abnormal, pronounced curvature of the vertebral column's lumbar region


region of the spine that consists of five vertebrae in the lower back, numbered L1–L5

occipital condyle

each of two large, convex processes that allow attachment of the spine to the skull by articulating with the first cervical vertebra of the spine

paranasal sinus

space or cavity within a nasal cavity bone. Each paranasal sinus opens into the nasal cavity.


markings, which are growths of tissues, such as those found on the cranium


region of the vertebral column that lies between the hip bones and is made up of fused vertebrae


common condition of curvature of the spine, producing a lateral, or sideways, bend in the vertebral column


air space within the skull and facial bones that are associated with the nose and throat and are found in the forehead, cheekbones, and behind the nose


seam that forms a joint between skull bones

thoracic cavity

area of a human's body from the neck to the abdomen, including the area within the ribs, breastbone, and dorsal vertebrae and containing the heart, lungs, and associated blood vessels

thoracic region

region of the spine in the chest that consists of 12 vertebrae, numbered T1–T12

vertebral column

part of the axial skeleton, consisting of vertebrae, intervertebral discs, nerves, and spinal fluid; functions to protect the spinal cord

vertebral foramen

triangular opening in each vertebra that forms the passageway for the spinal cord in the vertebral column