The lateral parts of the

occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobe ...

(also called the exoccipitals) are situated at the sides of the

foramen magnum The foramen magnum ( la, 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 oblon ...

; on their under surfaces are the

condyle A condyle (;Entry "condyle"
in
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Description

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

. The articular surfaces of the condyles are convex from before backward and from side to side, and look downward and lateralward. To their margins are attached the capsules of the atlantoöccipital articulations, and on the medial side of each is a rough impression or tubercle for the

alar ligament In anatomy, the alar ligaments are ligaments which connect the dens (a bony protrusion on the second cervical vertebra) to tubercles on the medial side of the occipital condyle. They are short, tough, fibrous cords that attach on the skull an ...

. At the base of either condyle the bone is tunnelled by a short canal, the

hypoglossal canal The hypoglossal canal is a foramen in the occipital bone of the skull. It is hidden medially and superiorly to each occipital condyle. It transmits the hypoglossal nerve. Structure The hypoglossal canal lies in the epiphyseal junction between ...

(anterior condyloid foramen). This begins on the cranial surface of the bone immediately above the

, and is directed lateralward and forward above the condyle. It may be partially or completely divided into two by a spicule of bone; it gives exit to the

hypoglossal The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or simply CN XII, is a cranial nerve that innervates all the extrinsic and intrinsic muscles of the tongue except for the palatoglossus, which is innervated by ...

or twelfth cerebral nerve, and entrance to a meningeal branch of the

ascending pharyngeal artery The ascending pharyngeal artery is an artery in the neck that supplies the pharynx, developing from the proximal part of the embryonic second aortic arch. It is the smallest branch of the external carotid and is a long, slender vessel, deeply sea ...

. Behind either condyle is a depression, the

condyloid fossa Behind either condyle of the lateral parts of occipital bone is a depression, the condyloid fossa (or condylar fossa), which receives the posterior margin of the superior facet of the atlas when the head is bent backward; the floor of this fossa is ...

, which receives the posterior margin of the superior facet of the

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when the head is bent backward; the floor of this fossa is sometimes perforated by the

condyloid canal The condylar canal (or condyloid canal) is a canal in the condyloid fossa of the lateral parts of occipital bone behind the occipital condyle. Resection of the rectus capitis posterior major and minor muscles reveals the bony recess leading to ...

, through which an emissary vein passes from the

transverse sinus The transverse sinuses (left and right lateral sinuses), within the human head, are two areas beneath the brain which allow blood to drain from the back of the head. They run laterally in a groove along the interior surface of the occipital bone. ...

. Extending lateralward from the posterior half of the condyle is a quadrilateral plate of bone, the

jugular process The jugular process is a quadrilateral or triangular bony plate projecting lateralward from the posterior half of the occipital condyle; it is a part of the lateral part of the occipital bone. The jugular process is excavated in front by the jugu ...

, excavated in front by the

jugular notch The suprasternal notch, also known as the fossa jugularis sternalis, jugular notch, or Plender gap, is a large, visible dip in between the neck in humans, between the clavicles, and above the manubrium of the sternum. Structure The suprasternal ...

, which, in the articulated skull, forms the posterior part of the

jugular foramen A jugular foramen is one of the two (left and right) large foramina (openings) in the base of the skull, located behind the carotid canal. It is formed by the temporal bone and the occipital bone. It allows many structures to pass, including the ...

. The jugular notch may be divided into two by a bony

spicule Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

, the intrajugular process, which projects lateralward above the hypoglossal canal. The under surface of the jugular process is rough, and gives attachment to the

Rectus capitis lateralis The rectus capitis lateralis, a short, flat muscle, arises from the upper surface of the transverse process of the atlas, and is inserted into the under surface of the jugular process of the occipital bone. Additional images File:Rectus capitis ...

muscle and the

lateral atlanto-occipital ligament Lateral is a geometric term of location which may refer to: Healthcare * Lateral (anatomy), an anatomical direction *Lateral cricoarytenoid muscle *Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral co ...

; from this surface an eminence, the paramastoid process, sometimes projects downward, and may be of sufficient length to reach, and articulate with, the transverse process of the

. Laterally the

presents a rough quadrilateral or triangular area which is joined to the jugular surface of the temporal bone by a plate of cartilage; after the age of twenty-five this plate tends to

ossify Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...

. The upper surface of the lateral part presents an oval eminence, the

jugular tubercle The jugular tubercle is an oval eminence on the superior surface of the lateral parts of occipital bone. It overlies the hypoglossal canal and is sometimes crossed by an oblique groove for the glossopharyngeal, vagus, and accessory nerve The a ...

, which overlies the

and is sometimes crossed by an oblique groove for the

glossopharyngeal The glossopharyngeal nerve (), also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper Medulla oblongata, medulla, just anterior (closer to the nose) to t ...

vagus The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right v ...

, and

accessory nerve The accessory nerve, also known as the eleventh cranial nerve, cranial nerve XI, or simply CN XI, is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is classified as the eleventh of twelve pairs of cranial nerv ...

s. On the upper surface of the jugular process is a deep groove which curves medialward and forward and is continuous with the

. This groove lodges the terminal part of the transverse sinus, and opening into it, close to its medial margin, is the orifice of the

Additional images

File:Lateral parts of occipital bone - animation06.gif, Human cranium seen from below. Lateral parts of occipital bone shown in red. File:Lateral parts of occipital bone - animation01.gif,

Occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobe ...

. Lateral parts shown in red. File:Gray131 Lateral parts of occipital bone.png,

at birth, outer surface. (Lateral parts shown in yellow.) File:Gray130.png, Occipital bone, inner surface.

References

{{Authority control Bones of the head and neck