The Structure of The Human Skull: Anatomy of Bone, Joint, Cartilaginous and muscle structures
The structure and functions of the head occupy one of the key positions in the study of medicine, and it is not unreasonable: it is in the skull that the main organs are enclosed, thanks to which a person is able to perceive and understand the world around him, maintain most of the physiological functions and form consciousness. The most important role here is played by the brain – this is how the bones of the skull protect it so strongly, trying to prevent the slightest injury, which can be fraught with serious consequences. The organs of hearing and sight, taste and smell, as well as the vessels and nerves that connect the brain with the rest of the body are located in the cavities of the skull. Articulating, the bones of the head form the upper respiratory tract and the initial section of the digestive tract (oral cavity), in which the preparatory stage is carried out – grinding and softening food.
The study of the bones of the skull is not limited to anatomy – the structure of the head is of interest to other scientists, including anthropologists and historians. By the slightest nuances of the skull, experts can determine gender, age and race, recreate the subtleties of the silhouette and predict the existing features of the body. Let’s look at what these or those nuances of the anatomy of the human head depend on, what role the bones of the skull play and how they perform the functions assigned to them.
The structure of the human skull: anatomy of bone, cartilaginous and muscle structures
It is believed that the main role in the structure of the head is played by bone formations: they surround the brain tissue with a dense frame, act as protective cavities for the eye sockets, hearing organs, nasal cavity, serve as an attachment point for muscles and form holes for the passage of blood vessels and nerve fibers. Cartilaginous structures form the outer part of the nose and the auricles, and in infancy they also replace some parts of the bones, providing mobility and thereby preventing child injury during childbirth.
The muscles of the head surround the skull with a relatively thin cover. Some facial features, facial expressions and the possibility of free movement of the lower jaw, due to which the chewing process is carried out, depend on their structure and degree of development. As a rule, muscle fibers are tightly attached to the bones and repeat the shape of the skull along their entire length.
The special structure allows the skull to cope with the functions assigned to it, among which the main place is occupied by:
protection of brain tissue from injury due to intense external influences;
the formation of physiognomic features of facial expressions and facial expressions;
thorough grinding and softening of food before it enters the digestive tract;
Human skull bones: anatomy
The following functional areas are distinguished in the human skull:
the inner base, on which the posterior, anterior and middle cranial fossa are located;
temporal and infratemporal fossa;
All these formations are formed due to various bone structures and their dense joints. In the anatomy of the human skull, there are 23 separate bones, of which 7 are unpaired and 16 are paired (8 pairs, respectively). In addition, the cranium contains 3 pairs of auditory bone formations – the malleus, incus and stapes in the right and left middle ear cavities. The dentition located on the upper and lower jaw is sometimes also referred to the bones of the skull. The number of teeth can vary depending on age and dental presentation.
The cerebral section of the skull is the receptacle and the main defense of the brain. This area includes:
the arch formed by flat bones;
external and internal base, consisting of mixed bones, some of which are classified as pneumatic (i.e., containing the airways).
The arch and base are formed due to the tight fixed articulation of 8 bone formations – 4 paired and 4 unpaired:
The right and left parietal bones form the lateral walls of the skull. They connect along the mid-sagittal line and adjoin the frontal bone, forming a coronary suture;
The right and left temporal bones are located slightly below the parietal bones. On their surface there are 3 processes – zygomatic, styloid and mastoid. The zygomatic process looks like a thin jumper and connects to the zygomatic bone just above the lower jaw. The subulate protrusion serves as an attachment point for most of the muscle fibers in the neck. And the mastoid process is located directly behind the auricle;
The frontal bone is easily felt from the front. It forms the surface of the forehead, brow arches and the upper part of the eye sockets;
The sphenoid bone represents the lower part of the orbits and the lateral surface of the skull. Shaped like a butterfly, this bone spans the skull and supports the base of the cranial cavity;
The ethmoid bone is located slightly below the frontal bone and forms the bony part of the turbinates and septum;
The occipital bone is the final part of the skull. It is located below the rest of the bones and is adjacent to the first cervical vertebra at the occipital condyles at the large opening through which the spinal cord passes.
The facial skeleton is formed by paired and unpaired mixed bones. They serve as the basis of the chewing apparatus and support for most of the facial muscles responsible for the formation of individual facial features. Each of the facial bones performs a specific function:
Two nasal bones make up the bridge of the nose and partially ensure the patency of the nasal passages;
The inferior turbinates look like thin curved plates. They separate the lower and middle nasal passages and form the lacrimal, maxillary and ethmoid processes;
The right and left cheekbones replace the side walls of the eye sockets;
Small lacrimal bones are located in front of the medial part of the eye orbits. They act as the junction of the eye sockets with the nasal sinuses;
Two maxillary bones, connecting along the midline, form the upper jaw, which holds the dentition and participates in the act of chewing;
The palatine bones are located in the posterior region of the nasal passages, they form part of the hard palate;
The lower jaw is one of the most powerful bones in the facial region of the skull. It adjoins the right and left temporal bones on both sides of the face, forming a movable joint, thanks to which the active part of chewing is carried out. In addition, the lower jaw supports the dentition and forms a visible oval of the face (cheekbones, chin, partly cheeks);
The opener is the main part of the nasal septum. It has a flat trapezoidal shape and occupies a central place in the nasal cavity, dividing it into two moves – right and left;
The hyoid bone is shaped like a small horseshoe and lies under the tongue. It is one of the few bones that does not connect with others, located directly in the thickness of muscle fibers.
Skull structure: anatomy of bony joints and joints
The vast majority of the bones of the skull are connected using fixed sutures. The adjacent facial bone formations form flat joints that are invisible under the thin cover of the muscle tissue. And the temporal bone, connecting with the parietal, gives rise to a scaly suture.
There are only 3 serrated sutures in the anatomy of the skull:
coronal, formed by the parietal and frontal bones;
sagittal, located between the two parietal bones;
lambdoid, located between the occipital and parietal bones.
The only movable joint of the skull is the mandibular. The lower jaw can perform movements in various planes: rise and fall, move to the right / left and forward / backward. Thanks to such mobility, a person can not only chew food thoroughly, but also maintain articulate speech.
With age, the shape and structure of the skull changes. So, in newborn babies, the facial part is almost 8 times smaller than the brain, so the head can look disproportionate and large. The crumbs’ jaws are usually underdeveloped and have no teeth, because he does not yet need to chew solid food.
The bones of the skull of babies are loosely articulated, so that the head can slightly change shape, shrink when passing through the birth canal. This feature protects newborns from birth trauma and helps maintain normal intracranial pressure. On the interosseous sutures, they have noticeable membranous areas – fontanelles. The largest – the anterior fontanelle – occupies a central position at the junction of the sagittal and coronal sutures. It usually grows over the age of two. Other fontanelles are less voluminous: the occipital, two wedge-shaped and mastoid membranes are not palpable by 2-3 months.
The anatomy of the skull changes not only in infancy – the formation usually takes place in 3 stages:
Preferential growth in height, strengthening of bones and hardening of seams – from birth to 7 years;
The period of relative rest is from 7 to 14 years;
The growth of the facial part of the skull is from 14 to 20-25 years, depending on puberty.
A short excursion into the anatomy of the skull allows you to visually make sure that the head is an extremely complex structure, the state of which directly affects the health of the brain, and therefore most of the vital functions. With the slightest injury, the bones take on most of the damage, but their strength is not unlimited – with a strong impact, fractures and bruises are not excluded, the consequences of which can be irreversible. Therefore, under all circumstances, the skull should be properly protected and protected from injury and other damage.