Anterior skull base and medial orbit wall
Explicación
The ethmoid bone is located at the anterior skull base and forms part of the medial wall of the orbit, as well as contributing to the nasal septum. It is unpaired and situated between the nasal cavity and the orbits.
Crista galli
Explicación
The crista galli projects from the cribriform plate and serves as an attachment point for the falx cerebri, a dural membrane. The other options are involved in other functions or structures of the ethmoid.
Cribriform plate, perpendicular plate, lateral masses
Explicación
The ethmoid bone comprises the cribriform plate (ethmoidal roof), perpendicular plate (forming part of the nasal septum), and the lateral masses (ethmoidal labyrinths) which contain the ethmoidal sinuses and conchae.
Houses the pituitary gland
Explicación
The sella turcica is a saddle-shaped depression in the sphenoid bone that houses the pituitary gland. It does not protect the optic chiasm or form part of the septum.
Olfactory nerves (CN I)
Explicación
The cribriform plate contains olfactory foramina through which the olfactory nerves (CN I) pass from the nasal cavity to the olfactory bulbs, enabling the sense of smell.
Mastoid process
Explicación
The mastoid process contains air cells and serves as an attachment point for neck muscles such as the sternocleidomastoid. The squama mainly forms the side of the skull, and the styloid anchors muscles of the tongue and pharynx.
Nasal septum
Explicación
The perpendicular plate of the ethmoid projects downward to form the superior part of the nasal septum, dividing the nasal cavity into two nostrils.
Lateral masses/ethmoidal labyrinth
Explicación
The ethmoidal air cells are located within the lateral masses or ethmoidal labyrinth of the ethmoid bone, contributing to the paranasal sinuses and sinus ventilation.
Ethmoidal sinuses and superior/middle conchae
Explicación
The lateral masses or ethmoidal labyrinths contain the ethmoidal air cells (sinuses) and give rise to the superior and middle nasal conchae.
Greater wings
Explicación
The greater wings form part of the lateral skull base and the orbit, while the lesser wings form part of the anterior cranial fossa and optic canal. The sphenoid body houses the sinuses and supports the skull base.
Bony ridges arising from the ethmoidal labyrinths that protrude into the nasal cavity
Explicación
The ethmoid conchae (superior, middle, and sometimes supreme) are bony ridges that are part of the ethmoidal labyrinths and project into the nasal cavity, increasing surface area.
Anchor muscles and ligaments of the tongue and pharynx
Explicación
The styloid process anchors muscles and ligaments associated with the tongue and pharynx, playing a key role in movements and stability of these structures.
Centrally at the skull base, posterior to the ethmoid
Explicación
The sphenoid bone is centrally located at the skull base, posterior to the ethmoid bone, and articulates with all other cranial bones. It acts as a keystone of the cranial floor.
Body, lesser wings, greater wings, pterygoid processes
Explicación
The sphenoid consists of the central body, two lesser wings forming the anterior boundary of the optic canal, two greater wings contributing to the skull base and lateral walls of the skull, and pterygoid processes.
Sphenoidal sinuses and sella turcica
Explicación
The sphenoid body contains the sphenoidal sinuses and the sella turcica, which houses the pituitary gland. The optic canal, however, is located within the lesser wings.
Pituitary gland
Explicación
The sella turcica is a saddle-shaped depression that contains the pituitary gland (hypophysis), suspended by the diaphragma sellae.
Optic canal
Explicación
The lesser wings of the sphenoid form the anterior boundary of the optic canal, through which the optic nerve (CN II) and ophthalmic artery pass.
Body and greater wings
Explicación
The body and greater wings of the sphenoid contribute primarily to the cranial base, forming part of the cranial floor.
Pterygoid muscles and ligaments
Explicación
The pterygoid processes serve as attachment points for the pterygoid muscles (medial and lateral pterygoids), which are involved in mastication, as well as ligaments such as the pterygomandibular ligament.
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Ethmoid bone — location?
Anterior skull base, medial orbit wall, nasal septum
Ethmoid — location?
Anterior skull base, nasal septum, medial orbit walls.
Ethmoid bone — parts?
Cribriform plate, perpendicular plate, lateral masses
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