The paired skulls are

In fact, the structure of the human skull is also very complex, because the skull is composed of bones of different sizes. And the bones above the human spine can be called the skull. At this time, we must pay attention to the protection of these bones to effectively avoid skull injuries. The skull bones are either paired or unpaired, so what are the paired skull bones?

The skull is located above the spine and is composed of 23 flat and irregular bones of different shapes and sizes (the three pairs of ossicles in the middle ear are not included). Except for the mandible and hyoid bone, the other bones are firmly connected to each other by sutures or cartilage, playing a role in protecting and supporting the brain, sensory organs, and the initial parts of the digestive and respiratory organs.

The skeleton of the human and vertebrate head.

The skull is divided into two parts: the brain skull and the facial skull, using the line connecting the upper edge of the orbit and the upper edge of the external auditory meatus as the dividing line. The brain skull is located at the posterior and superior part of the skull, and includes paired parietal and temporal bones, unpaired frontal bones, sphenoid bones, occipital bones and ethmoid bones, a total of 8 bones, which surround the cranial cavity and accommodate the brain. The facial skull is the anterior and lower part of the skull, which includes the paired maxillary bones, zygomatic bones, nasal bones, lacrimal bones, palatine bones and nasal concha bones, and the unpaired vomer, mandible, and hyoid bones, a total of 15 bones, which form the bony support of the orbit, nasal cavity, oral cavity and face.

The human skull is composed of 23 bones, which support and protect important organs such as the brain. Except for the mandible and hyoid bone, all other bones are connected by sutures or cartilage, which are inflexible connections. The skull can be divided into the brain skull and the facial skull. The former surrounds the cranial cavity, and the latter constitutes the bony support of the orbits, nasal cavity and oral cavity. There are a total of 8 brain skull bones, including a frontal bone in the front, an occipital bone in the back, 2 parietal bones above, a temporal bone on each side, an ethmoid bone in the front center of the skull base, and a sphenoid bone in the middle of the skull base. The facial skull is composed of 15 bones: above the mouth, there is a maxillary bone on each side, a pair of nasal bones on the upper inner side, a pair of lacrimal bones at the back, a pair of elevated zygomatic bones on the upper outside, and a pair of palatine bones at the back. On the inside, there is a pair of inferior turbinate bones extending into the nasal cavity, and the bone plate in the middle of the nasal cavity is the vomer. The mandible is a skull bone that forms a joint and is able to move. In addition, there is a free bone, the hyoid bone.

Each structure composition

The skull consists of two parts: the brain skull and the facial skull. The skull is divided into the skull cap and the skull base.

(1) The skull is composed of an outer plate, a diaphyseal plate, and an inner plate, including the frontal bone, parietal bone, occipital bone, temporal bone, part of the zygomatic bone, and greater wing of the sphenoid bone, which are connected together by the coronal suture, sagittal suture, herringbone suture, and squamous suture. The inner surface of the skull is concave, and the impressions are composed of the gyri, arachnoid granulations, venous sinuses and meningeal blood vessels.

(2) The inner surface of the skull base is uneven, and from front to back it is bounded by the sphenoid ridge and the petrous ridge, forming a three-level stepped structure, which are called the anterior, middle, and posterior cranial fossa.

The central small part of the anterior cranial fossa is the ethmoid plate, the large parts on both sides are the orbital plates of the frontal bones, and the posterior part is the lesser wing of the sphenoid bone, which accommodates the frontal lobe.

The middle cranial fossa is composed of the sphenoid body and greater wing of the sphenoid bone and is butterfly-shaped, divided into a smaller central part (sellar region) and two larger and concave lateral parts (accommodating the temporal lobes). The sella turcica is located in the center of the middle cranial fossa, above the body of the sphenoid bone. The median protrusion in front is called the tubercle sella, with the anterior clinoid processes on both sides and the chiasmatic groove and optic canal below, which is the channel for the optic nerve to exit the skull. The central depression of the sella turcica is the pituitary fossa that accommodates the pituitary gland. The upper protrusion of the posterior bone plate is called the dorsum sella, and the upper outer corners on both sides are the posterior clinoid processes. There are many bone holes and fissures in the middle cranial fossa that communicate with the outside of the skull and serve as passages for nerves and blood vessels, including: ① superior orbital fissure: through which the oculomotor nerve, trochlear nerve, abducens nerve, ophthalmic branch of the trigeminal nerve and superior ophthalmic vein pass; ② foramen rotundum, foramen ovale and foramen spinosum: arranged from front to back at the root of the greater wing of the sphenoid bone, through which the second and third branches of the trigeminal nerve and the middle meningeal artery pass respectively; ③ foramen rupture: located between the sella turcica and the petrous apex, through which the internal carotid artery and sympathetic plexus pass.

The posterior cranial fossa is mostly composed of the occipital bone, and the anterior wall on both sides is the back of the petrous bone, which accommodates the cerebellum, pons and medulla oblongata. In the center of the fossa is the foramen magnum, which is the connection between the cranial cavity and the vertebral canal. The medulla oblongata is connected to the spinal cord through it, and the vertebral artery and cervical branch of the accessory nerve pass through it. There is a slope in front of the foramen magnum, and there is a round protrusion on each side of the lower end of the slope, which is the jugular tubercle. Behind the petrous ridge is the internal auditory foramen, through which the facial nerve, auditory nerve, and labyrinthine artery and vein pass. The internal occipital protuberance is where the sinus confluence is located. The transverse sinus originates from both sides of the sinus confluence, moves to the posterior end of the upper edge of the petrous part of the temporal bone, and continues to the sigmoid sinus. The internal jugular vein, glossopharyngeal, vagus and accessory nerves pass through the jugular foramen.