Skull: joint of the skull bones. Types of connection of the bones of the skull

The skeleton of the head of vertebrates is called the "skull." Anatomy allows him to carry a protective function due to firmly and immovably attached to each other bones (the only exception being the mandible and the hyoid bone). The skull is a kind of box that preserves the brain and senses. It is the skeleton for the nasal and oral cavities, has a system of openings and channels in which nerve fibers, arteries and veins pass.

Development in phylogeny

Over time, in the course of natural selection, the animals developed a nervous system and appeared nervous ganglia, and later the brain. The skeleton in these places was supposed to protect the nervous tissue and sensory organs to the maximum, so the cartilaginous skull first appears in the cyclostomes. Its bones are divided according to their origin into replacing cartilage, integumentary and visceral. The skull first appears in the fish. The connection of the bones of the skull goes through the cartilage, which replaces the bone tissue. Bones located outside, appeared from ossification in the layers of the dermis.

The visceral parts of the skull of vertebrates are nothing more than altered gill arches from cartilaginous tissue, so in the process of embryogenesis early rudiments of the gill openings are laid in the process of embryogenesis. Later on this place the muscles and bones of the visceral skeleton will form.

Types of connection of bones

Numerous flat, mixed and pneumatic bones form the skull. The connection of the bones of the skull occurs through the following types of attachments: continuous (synarthrosis), discontinuous (joints or diarthrosis).

Synarthritis is distinguished by the type of connective tissue:

1. SYNDESMOSIS (from fibrous tissue) are represented by ligaments, sutures, interosseous membranes, fontanel and vkolachivaniyami (connecting the root of the tooth with the jawbone).
2. Synchondroses (from cartilaginous tissue) can be permanent throughout life or replaced with bone tissue over time.
3. Syndesmosis - are formed when the cartilaginous tissue of synchondrosis is replaced by bone.

Synchondrosis, in the thickness of which there is a cavity, is a symphysis, this kind of connection is present in the pelvis, connecting the pubic bone.

Diarthroses are common mobile joints covered with cartilaginous tissue. They are a connective tissue capsule forming a cavity with synovial fluid inside. Diarrtoses are distinguished by the shape of articular surfaces and the number of their components.

Brain skull

The skull of an adult is formed by 23 basic bones, 3 bones in the auditory process, and 32 teeth. The skull is divided into a neurocranium (cerebral) and facial (visceral).

Bones of the cerebral part of the skull :

1. Unpaired:

• Occipital (four parts);
• Wedge shaped (body, large and small wings, wing processes);
• Frontal (also has four parts)
• Latticed (has a labyrinth) - it is sometimes referred to as the facial skeleton.

2. Paired: parietal, temporal.

The temporal bone of the skull has a complex structure, because it is the channel of the auditory passage. It consists of three parts, which in the perinatal period and after birth are represented by different bones that eventually merge into one. Thus, three components are distinguished: scaly, drum and rocky parts, separated by intermediate seams.

The scaly part includes the zygomatic process, which participates in the formation of the mandibular joint. From here begins the auditory move, which passes into the tympanum (localization of the middle ear), where the auditory ossicles are located: a hammer, an anvil and a stapes, as well as a small lenticular cartilage between them. These elements are involved in trapping sound waves, transferring their vibrations to the inner ear.

Stony bone is very strong and serves as a skeleton for the organs of hearing and balance. Behind the drum cavity is a complex bone system, which is a kind of labyrinth, which is the basis of the inner ear. In addition, there is a system of openings and channels that conduct nerve fibers and blood vessels.

So, thanks to its complex device, the temporal bone of the skull performs several functions at once.

Inside the frontal bone is a cavity.

Visceral Skull

The bones of the visceral part of the skull are:

1. Unpaired: vomer, mandibular (result of fusion of paired dental bones) and sublingual (fixes the tongue, throat and larynx muscles) of the bone.

2. Paired:

• Maxillary (fused with the brain department);
• Incisors (anterior bones of the jaw);
• Palatine bones (forming the bottom of the skull);
• Pterygoid bones;
• Cheekbones (create a zygomatic arch and partly an orbit).

In the maxilla and mandible alveoli, 32 teeth are attached in adults. The facial skull is involved in the formation of the orbit.

In the maxillary bone there are sinuses, which together with those of the frontal and sphenoid ossicles, as well as the maze of the latticed bone, constitute the paranasal sinuses lined with the mucous membrane.

In the seams and fontanels, unstable bones of the skull are observed.

Structure of the bones of the skull

The skull is formed by flat bones consisting of compact matter and spongy (diploe). From the side of the brain, a plate of such a substance is very fragile and easily breaks with trauma. The poniard is attached to the bones in the seam area, forming in other areas a subperiosteal space with a loose structure. From the inside emerges a hard shell of the brain.

Types of connection of the bones of the skull

The main type of bone joints of the neurocranium is syndesmosis. Most such mergers are represented by serrated sutures; Only between the temporal and parietal bones is the scaly suture. The facial skull has flat scars. Anatomically, the seam is often referred to by the names of bones that form with the help of it, forming the skull. The connection of the bones of the skull includes one sagittal suture (by means of which the parietal parietal bone of the skull is connected), coronary (connects the parietal and frontal bones) and lambdoid (connects the occipital and parietal bones).

Also, unstable joints can occur, sometimes resulting from insufficient skull ossification.

Attachment of teeth

Types of connection of the bones of the skull include vkolachivaniya - a kind of syndesmosis, represented by the attachment of the tooth to the jaws - mandible and maxilla.

Teeth consist of the following layers: on top they are enameled, under it is a solid dentin, inside it is formed a pulp cavity containing a pulp (passing vessels and nerve). At the bottom of the root there is also cement - fibrous cloth, reinforced with lime. The tooth is attached to the alveolar process of the jaw with the help of cement and periodontal ligaments.

These mandibular processes are formed with the help of two cortical plates and a spongy substance between them. The space between the plates is divided by means of interdental partitions into separate alveoli. The roots of the tooth are surrounded by a periodontal ligament - it is a connective tissue, formed from fibers of different types and different directions, it is she who fixes the root of the tooth to the jaw.

Temporomandibular joint

The joint is paired (the two mandibular joints act together, being a complex), combined (there is an articular disc), ellipsoidal. It forms the mandible (as the mobile bone of the skull), or rather its articular head, and the processes of the temporal bone. The capsule is free, the joint has ligaments both inside and outside of it.

The joint is able to perform the following movements:

• Up and down (opening and closing the mouth);
• Lateral movements;
• Pushing the jaw forward.

Atlantoccipital joint

The skull, the anatomy of which allows it to carry a mostly protective function, can also perform various movements due to the joint connecting the occipital bone and the first vertebra (atlant). On his part, the joint is formed by the condyles of the occipital bone; It is paired (since the two condyles connect to the articular pits of the atlant) is ellipsoidal, has two membranes (anterior and posterior), and lateral ligaments.

Development of the skull in ontogenesis

Perinatal development includes three stages: membranous, cartilaginous and bone. The first phase is from two weeks, the second - from the age of two months of embryo formation. At the same time, in many parts of the skull development passes the second stage.

The skull originates from the anterior part of the chord, the mesenchyme and the rudiments of the gill arches. As the brain, nerves and blood vessels grow, it forms around them. Bones are divided into primary (originating from connective tissue) and secondary (originating from cartilage). At a certain moment, foci of ossification appear in the cartilage, which grow in depth, forming plates of compact and spongy substance.

Features of the structure of the skull in newborns

The skeleton of a newborn is very different from what can be seen in an adult. The skull is strongly developed with respect to the rest of the body and has a large circumference, and the brain area is much larger than the facial. However, the main difference lies in the presence of fontanelles - cartilaginous joints, remnants of membranous skull, which eventually will be replaced by bone tissue. Their presence allows the bones of the head to move, thereby helping it to pass through the birth canals at birth, protecting against various kinds of bruises. They are also a compensatory mechanism that protects the brain with head injuries at the beginning of life.

The large (anterior) fontanel is the most extensive, located where the frontal and parietal bone of the skull is attached, it closes when the child reaches two years of age.

A small (rear) fontanel is located between the parietal and occipital bones, it closes faster - already in the second or third month of the development of the child.

There are also small wedge-shaped and mastoid fontanels located on the lateral surfaces of the skull and ossified soon after birth.

Features of the structure of the skull at a young age

The human body grows and develops to 20-25 years. Up to this point, there is such a type of connection of the bones of the skull, like synchondrosis, formed by a fibrous cartilaginous tissue. It is present between the wedge and occipital bone, and also between the four parts of the occipital bone. At the base of the skull there is a stony-occipital synchondrosis, as well as a layer of cartilaginous tissue at the junction of the sphenoid bone and the lattice. Over time, bone tissue develops in their place, and syndesmosis appears.

Thus, it is clear what complex functions the human skull carries. The connection of the bones of the skull is arranged in such a way that it allows the entire bone structure to be extremely strong, fulfilling the role of protection for the brain, sensory organs, vital vessels and nerve fibers. Therefore it is very important to keep your head from blows, bruises and various kinds of injuries.

When riding a horse, motorcycle, scooter, ATV and other vehicles, you should wear a safety helmet, it can protect the cranium from damage in the event of a fall or accident.