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The foramen magnum (Latin: great hole) is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull . The spinal cord , an extension of the medulla oblongata , passes through the foramen magnum as it exits the cranial cavity .
The thecal sac or dural sac is the membranous sheath (theca) or tube of dura mater that surrounds the spinal cord and the cauda equina. The thecal sac contains the cerebrospinal fluid which provides nutrients and buoyancy to the spinal cord. [1] From the skull the tube adheres to bone at the foramen magnum and extends down to the second sacral ...
From its front to the back is the basilar part, also called the basioccipital, at the sides of the foramen magnum are the lateral parts, also called the exoccipitals, and the back is named as the squamous part. The basilar part is a thick, somewhat quadrilateral piece in front of the foramen magnum and directed towards the pharynx. The squamous ...
The condyles are oval or reniform (kidney-shaped) in shape, and their anterior extremities, directed forward and medialward, are closer together than their posterior, and encroach on the basilar portion of the bone; the posterior extremities extend back to the level of the middle of the foramen magnum.
The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra.. The condyles are oval or reniform (kidney-shaped) in shape, and their anterior extremities, directed forward and medialward, are closer together than their posterior, and encroach on the basilar portion of the bone; the ...
Squamous part of occipital bone. Human skull seen from above (parietal bones removed). Squamous part is shown in red. Occipital bone at birth, seen from below. (Squamous part is top half, portion above foramen magnum, shown in yellow.) The squamous part of occipital bone is situated above and behind the foramen magnum, and is curved from above ...
Synchondrosis of these two bones forms the clivus. The clivus extends inferiorly to the foramen magnum. [3] On axial planes, it sits just posterior to the sphenoid sinuses. It is medial to the foramen lacerum (the internal carotid artery reaches the middle cranial fossa above the foramen lacerum), proximal to its anastomosis with the Circle of ...
The foramen magnum is located inferiorly under the skull, which puts much of the weight of the head behind the spine. The flat human face helps to maintain balance on the occipital condyles . Because of this, the erect position of the head is possible without the prominent supraorbital ridges and the strong muscular attachments found in, for ...