Not every person treats his health properly. Often people don’t even pay attention to some pains, and this suggests that the body is not in perfect order, and measures need to be taken. For example, few people care about pain in the sacrum. Meanwhile, this can signal the presence of a serious disease. Often, not all of us are familiar with the structure of the sacrum. Let's look at it together.
How is the sacrum
The sacral section is a large bone of a triangular shape, which is located at the base of the spinal column. Since the skeleton is still forming in children, it consists of five separate vertebrae in them, and in adults it is a single part. It is a kind of wedge placed between the pelvic bones.
As a rule, the sacrum is formed by five fused vertebrae, but there may be more of them, in the presence of such an anomaly as sacralization. The vertebrae are not always fused in adolescence, which, incidentally, is not a violation, and usually by the age of 25 everything is corrected.
Sacral departments
Now consider in more detail what structure the sacrum has. Its anatomy involves the connection of the bone with the lumbar and coccyx. Moreover, it consists of several parts:
- front and back surfaces (facies pelvina, facies dorsalis);
- lateral departments (pars lateralis);
- base (basis ossis sacri);
- top (apex ossis sacri);
- sacral canal (canalis sacralis).
The front surface has a concave shape, which is more pronounced in the direction down and up, but less on the sides. In the middle of the anterior part of the sacrum, 4 crosses cross, forming places of fusion of the vertebrae. On both sides of these lines are holes in the amount of 4 pieces on each side. They have a rounded shape, directed forward and sideways, and in the direction from top to bottom, you can notice a change in diameter in a smaller direction. Blood vessels and nerve endings that form plexuses pass through these openings.
On the back surface, the structure of the sacrum has a narrower and convex shape with roughness. Five bone scallops, which are formed by the fusion of some vertebrae, pass along it. The spinous processes form an unpaired ridge, the articular processes merge into intermediate ridges, and the paired ridges of the same name are formed by lateral processes. Sometimes all the tubercles merge into a single comb.
The lateral surfaces are distinguished by the expansion in the upper part, but they are narrowed downwards.
The base is a bone that has a protruding and broad shape, facing forward and upward. Its front part is connected to the fifth vertebra of the lower back, which forms a kind of cape directed into the pelvic cavity.
The top has an oval shape, which allows it to better connect with the tailbone bone.
The structure of the sacrum and coccyx includes the canal, which runs along the entire bone and has a curved shape. Above it is expanded and resembles a triangle, and below it is narrowed. In this case, the rear wall of the channel remains unfilled. In the sacral canal is the plexus of nerve endings that exit through the holes.
How is the pelvis
The sacrum, located closer to the back, is only part of the general structure of the pelvis of any person, despite gender. As a rule, it consists of three main parts:
- two pelvic bones;
- sacrum;
- coccyx.
In front, two paired pelvic bones are connected by a non-synovial semi-movable joint. Otherwise, this site is referred to as the pubic joint or pubic symphysis. Behind these bones with their sections of an ear-shaped form are attached to the same protrusions of the sacral bone. As a result, this leads to the formation of paired sacroiliac joints.
Moreover, each of the two bones, as well as the structure of the pelvis, in turn, also consists of three other components:
Upon reaching 16-18 years of age, these bones are interconnected by cartilage. Then there is a gradual fusion of these elements into a single pelvic bone. On their outer surface there is an acetabulum, which serves as a convenient place for attaching the femoral head.
As a result, a pelvic cavity or ring is formed, where the internal organs are enclosed. At the same time, the entire pelvis is divided into two sections: large, wider (pelvis major) and small, narrower (pelvis minor). They are separated by a border line that runs through the sacral promontory, the arches of two iliac bones, the crests of the pubic bones and the upper border of the pubic joint.
As a result, the structure of the pelvis includes a department where the internal organs belonging to the lower abdomen are located - this is a large pelvis. And in the small, the rectum and the bladder are hidden. In addition, there is the uterus along with the appendages and the vagina in women. In men, this department protects the prostate gland and seminal vesicles.
Differences in the structure of the pelvis of men and women
The main differences in the structure of the pelvic region are due to the fact that the woman’s body is adapted for the birth of a child. Like the pelvis, the female sacrum also looks different (the structure, the scheme of which is presented in our article). It is wider and less curved.
The female pelvis is noticeably wider and shorter. In addition, its openings differ: in the female half, they are much wider, since a child passes through them. Moreover, during childbirth, the opening increases. The pelvic bones themselves in women are more curved than in men.
Functional purpose
In our body, an important role lies with the sacrum. Structural features allow him to perform the main function of protecting organs that are located in the pelvic cavity. But, in addition to this, the sacrum provides a vertical position of the human skeleton. Thanks to him, the entire load is distributed evenly, especially a large volume of it falls when walking. And since the vertebrae of the sacrum are motionless, it cannot perform a motor function.
Muscular apparatus
The sacral section would not be able to perform its function normally without a muscle group:
- pear-shaped;
- iliac;
- multi-partitioned;
- buttock.
The sacrum itself, the ligamentous apparatus and the large sciatic opening are the beginning of the piriformis muscle. Separate bundles of muscle fibers depart from them, which are then connected and sent to the greater trochanter of the femur bone. The muscle provides rotational movements of the femoral joint.
The ileal muscles of the sacrum also begin with the bone, where the iliac crest along with the fossa is responsible for its attachment. Then the muscle goes to the lesser trochanter of the hip bone. Its function is to bend the lower limb.
Multiple muscle fibers are located in the grooves of the sacrum and are responsible for bending the back back.
The gluteal muscle apparatus originates from the bones of the sacrum and tailbone, including the iliac. Further, the fibers extend to the gluteal tuberosity. In the entire sacral region, the gluteal muscle is the largest. Her task is the rotation and flexion of the lower limbs.
Sacral blood supply
Certain blood vessels are responsible for the nutrition of muscle fibers in the department described. The structure of the sacrum is such that the piriform and gluteal muscle group receives beneficial substances due to the gluteal arteries, which are divided into several branches.
The ileo -lumbar artery is suitable for the iliac muscle fibers . In addition to it, an artery surrounding the hip bone also takes part. The lumbar arteries provide nutrition to a divided muscle group.
Nerve endings
Good muscle structure is possible due to nerve endings. The activity of the ileal and piriform muscle groups is controlled by the lumbar and sacral plexus. This ensures the mobility of each joint. At the same time, the lumbar plexus is responsible for the iliac fibers , and the nerve endings of the sacrum monitor the piriformis muscles.
The structure of the sacrum includes the gluteal plexus of nerve cells, which controls the work of the muscles of the same name. For the innervation of a divided muscle group, the spinal nerve channels are responsible.