Occipital bone

Consists of 4 parts:

• occipital scales ( lat. squama occital );
• lateral masses, or condyles ( lat. partes laterales );
• body (basilar part, basion) ( lat. pars basilaris ).

At the junction of the four parts, there is a large occipital foramen ( lat. Foramen occipitale magnum ), which connects the cranial cavity with the vertebral canal.

Scales

It is a flat plate of spherical shape, with an outer (convex) and inner (concave) surface.

On the outer surface there is:

• Outer occipital protrusion (inion) - palpable elevation in the center of the occipital scales;
• Occipital area - part of the scales above inion;
• The highest nuch line - starts from the top edge of the inion;
• Upper nuchal line - at the level of the occipital protrusion between the highest and lower nuchal line;
• The lower left line is between the upper left line and the large occipital foramen;
• Outer occipital ridge - goes vertically from inion to BSO.

On the inner surface there are:

• Cross elevation - elevation on the inner surface of the occipital bone, in the place of the intersection of the internal occipital crest and furrows of the upper sagittal and transverse sinuses.
• Internal occipital protrusion - corresponds to the place of confluence of the venous sinuses;
• Internal occipital crest;
• Furrow of the upper sagittal sinus;
• Two transverse sinus furrows;
• Base - conditional point corresponding to the middle of the front edge of the large occipital foramen;
• Opision is the identification point corresponding to the middle of the posterior edge of the large occipital foramen.

The relief of the inner surface is due to the shape of the brain and its membranes adjacent to it.

Lateral masses

Limit the large occipital foramen with lateral edges. On the outer surface there are condyles for connecting the articular surfaces of the first cervical vertebra (atlanta).

In the composition of the lateral masses are distinguished:

• Jugular shoots - limit the jugular opening from the sides, correspond to the transverse processes of the vertebra;
• The hypoglossal nerve canal (hypoglossal canal) is located in front of and to the side of the large opening. Contains the XII cranial nerve;
• Condylar channel - located behind the condyle, contains the emissary vein;
• Jugular tubercle - located above the hyoid channel.

Body

The most front part. Mowed front and top. It distinguishes:

• The lower surface - carries the pharyngeal tubercle, the place of attachment of the throat suture;
• The two outer edges are connected to the pyramids of the temporal bone ;
• The upper surface (slope) - facing the cavity of the skull.
• The groove of the lower stony sinus runs along the lateral edge.

Forms joints with the bones of the arch and base of the skull. It is the link between the skull and the spine.

• With a sphenoid bone: the front surface of the body of the occipital bone is connected to the back surface of the sphenoid bone. Synchondrosis compound.
• With parietal bone: occipital-parietal suture. The superior anterior margin of the occipital bone joins the posterior margin of the parietal. At the junction of the dark and occipital-parietal seams is the conditional point "lambda". Sometimes in the lambda region there is an intertimen bone formed from the upper half of the occipital scales, separated from it by a transverse suture.
• From the temporal:

1. Occipital-mastoid suture: the mastoid margin of the occipital bone joins the posterior low surface of the temporal bone;
2. Petro-jugular suture: the jugular process of the occipital bone joins the jugular notch of the temporal bone;
3. The petrobasilar suture - the lateral edge of the base of the occipital bone joins the pyramid of the temporal bone. Schindylosis compound.

• With the first cervical vertebra: the condyles of the occipital bone are connected to the concave surfaces of the atlas with their convex lower surface. Joint type diarthrosis (there is cartilage, capsule, ligaments, synovia).

Attaching Bundles

• Anterior Atlanto-occipital membrane: stretched between the front arc of Atlanta and the base of the occipital bone;
• Posterior atlanto-occipital membrane: between the posterior arc of the atlas and the posterior part of the greater occipital foramen. Included in the posterior wall of the spinal canal;
• Lateral atlanto-occipital ligament: connects the transverse process of the atlas with the jugular process of the occipital bone;
• Tooth ligament: from the top of the tooth (process of the second cervical vertebra) to the front edge of the large opening;
• Pterygoid ligaments of the tooth: to the lateral edges of the large opening;
• The integumentary membrane: continuation of the posterior longitudinal ligament in the direction of the anterior edge of the large opening, passes into the periosteum of the bones of the skull base;
• Surface aponeurosis: attached along the upper line;
• Deep aponeurosis: attached to the base of the occipital bone.

Muscle Attachment

• To the highest occipital line: occipital abdomen of the skull;
• To the upper occipital line: occipital , trapezoid , sternocleidomastoid , belt ;
• To the lower occipital line: small posterior rectus muscle of the head (to the spinous process of Atlanta), large posterior rectus (to the spinous process of the second cervical vertebra), upper oblique muscle of the head (to the transverse process of the second cervical vertebra).

Dura mater

• Cerebellar mark : attached at the edges of the transverse occipital sulcus;
• Sickle of the brain : attached by the back to the edges of the furrow of the superior sagittal sinus;
• Sickle of cerebellum: to the internal occipital ridge.

Nerves

• Pass through the jugular foramen: IX (glossopharyngeal), X (wandering), XI (additional) pairs of cranial nerves;
• Through the hypoglossal nerve canal at the level of the condyles: XII pair (hypoglossal);
• The spinal roots of the XI pair pass through the large occipital foramen.

Vessels

• At the level of the internal occipital eminence is the place of the confluence of the sinuses ( lat. Confluens sinuum ), where the transverse, lower occipital, upper sagittal and straight sinuses flow;
• The lower occipital sinus passes through the internal occipital ridge;
• Upper sagittal sinus - in the same furrow;
• The transverse sinuses - in the furrows of the same name;
• Internal jugular vein: passes through the jugular foramen;
• Lower rocky sine: in the groove between the pyramids of the temporal bone and the lateral masses of the occipital;
• Vertebral arteries: pass into the cranial cavity through the large occipital foramen. Meningeal branches supply blood to the bones of the skull and TMO of the cerebellum;
• Posterior meningeal artery (branch of the external carotid): penetrates the skull through the jugular foramen, supplies the TMT of the posterior cranial fossa.

Prenatal Period

The occipital bone consists of two parts:

• Mezhtemennaya scales - part of the bone above the upper nuchal line, has a membranous origin with two points of ossification;
• Occiput - the rest of the bone below the superior nuchal line is of cartilaginous origin with six ossification centers. It consists of supraocciput (scales below the superior nuchal line) with two cores of ossification, infraoccyptum (condyles and base of the bone) with four cores of ossification. At the level of the hypoglossal nerve canal, the condyles are divided into anterior 1/3 and posterior 2/3. At the level of the upper nuchal line, there passes the hinge of Boudin separating the membranous part of the bone from the cartilaginous.

Birth Period

The occipital bone consists of six parts separated by cartilage:

• Scale;
• A pair of posterior 2/3 condyles;
• Pair of anterior 1/3 condyles;
• Base.

After birth

The merger of the supra and infraocciput occurs in 5 years. The fusion of the anterior and posterior parts of the condyle and the base ends by age 7.

• Posterior cranial fossa
• Base of skull

• Occipital bone // Brockhaus and Efron Encyclopedic Dictionary : 86 tons (82 tons and 4 extra). - SPb. , 1890-1907.
• Hants Fenish. Pocket atlas of human anatomy. - Minsk: Higher School, 1996.
• Kravchenko T. I., Kuznetsova M. A. Cranial osteopathy. - SPb :, 2004. - p. 23-31.