Not every person treats their he alth properly. Often people do not even pay attention to some pains, and this indicates 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 illness. Often, not all of us are familiar with the structure of the sacrum. Let's explore it together.
How the sacrum works
The sacrum is a large triangular bone located at the base of the spinal column. Since the skeleton is still being formed in children, it consists of five separate vertebrae in them, while in adults it is a single part. It fits like a wedge between the pelvic bones.
As a rule, the sacrum is formed by five fused vertebrae, but there may be more if there is such an anomaly as sacralization. The vertebrae do not always fuse during adolescence, which, by the way, is not a violation, and usually by the age of 25 everything is corrected.
Departments of the sacrum
Now let's take a closer look at the structure of the sacrum. Its anatomy implies 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 divisions (pars lateralis);
- base (basis ossis sacri);
- apex (apex ossis sacri);
- sacral canal (canalis sacralis).
The front surface has a concave shape, which is more pronounced in the downward and upward direction, but less in the sides. In the middle, the anterior part of the sacrum is crossed by 4 crossbars, which form the fusion sites of the vertebrae. On both sides of these lines there 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 to a smaller side. Blood vessels and nerve endings pass through these openings and form plexuses.
On the back surface, the structure of the sacrum has a narrower and more convex shape with roughness. Five bony crests run along it, which are formed by the fusion of some vertebrae. The spinous processes form an unpaired ridge, the articular processes merge into intermediate ridges, and the lateral processes form paired ridges of the same name. Sometimes all the tubercles merge into a single ridge.
The sides are broader at the top but narrower at the bottom.
Base -it is a bone that has a prominent and broad shape, facing forward and upward. Its front part connects to the fifth vertebra of the lower back, which forms a kind of cape directed into the pelvic cavity.
The top is oval in shape, which allows it to better connect with the coccyx bone.
The structure of the sacrum and coccyx also includes a canal that runs along the entire bone and has a curved shape. From above it is expanded and resembles a triangle, and at the bottom it is narrowed. In this case, the back wall of the channel remains unfilled. In the sacral canal is a plexus of nerve endings that exit through holes.
How the pelvis works
The sacrum, located closer to the back, is only part of the overall structure of the pelvis of any person, regardless of gender. As a rule, it consists of three main parts:
- two pelvic bones;
- sacrum;
- coccyx.
Front, the two paired bones of the pelvis are connected through a non-synovial semi-movable joint. Otherwise, this area is referred to as the pubic articulation or pubic symphysis. Behind these bones, with their ear-shaped sections, are attached to the same protrusions of the sacral bone. As a result, this leads to the formation of paired sacroiliac joints.
At the same time, each of the two bones, as well as the structure of the pelvis, in turn, also consists of three other components:
- iliac;
- ischial;
- pubic.
After reaching the age of 16-18, these bones are interconnected by cartilage. Thenthere 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: a large, wider one (pelvis major) and a small, narrower one (pelvis minor). They are separated by a border line that passes through the sacral promontory, the arches of the two iliac bones, the crests of the pubis, and the superior border of the pubic symphysis.
As a result, the structure of the pelvis includes a section where the internal organs belonging to the lower abdominal cavity are located - this is a large pelvis. And in the small, the rectum and bladder are hidden. In addition, here is the uterus along with appendages and the vagina in women. In men, this department guards the prostate gland and seminal vesicles.
Differences in the structure of the pelvis of men and women
Mainly the differences in the structure of the pelvic region are caused by the fact that the woman's body is adapted to the birth of a child. Like the pelvis, the female sacrum also looks different (the structure, the diagram 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 are also different: in the female half they are much wider, since a child passes through them. Moreover, during childbirth, the hole increases. The pelvic bones themselves in women are more curvature than in men.
Functional purpose
In our body, an important role falls on the sacrum. Structural features allow it to perform the main function of protecting the organs that are located in the pelvic cavity. But, in addition, the sacrum provides a vertical position of the human skeleton. Thanks to him, the entire load is distributed evenly, especially when walking. And since the vertebrae of the sacrum are immobile, it cannot perform a motor function.
Muscular Apparatus
The sacral region would not be able to perform its function normally without a muscle group:
- pear-shaped;
- iliac;
- partitioned;
- gluteal.
The beginning of the piriformis muscle is the sacrum itself, the ligamentous apparatus and the greater sciatic foramen. Separate bundles of muscle fibers depart from them, which are then connected and sent to the greater trochanter of the femoral bone. The muscle provides rotational movement of the hip joint.
The iliac muscles of the sacrum also start from the bone, where the iliac crest along with the fossa is responsible for its fastening. Then the muscle goes to the lesser trochanter of the thigh bone. Its function is to bend the lower limb.
Manifested muscle fibers are located in the grooves of the sacrum and are responsible for bending the back back.
The gluteal muscular apparatus originates from the bones of the sacrum and coccyx, including the iliac. Further, the fibers extend to the gluteal tuberosity itself. In everythingin the sacral region, the gluteal muscle is the largest. Its task is rotation and flexion of the lower limbs.
Sacral blood supply
Certain blood vessels are responsible for providing nutrition to the muscle fibers of the described department. The structure of the sacrum is such that the piriform and gluteal muscle groups receive nutrients from the gluteal arteries, which are divided into several branches.
The iliac-lumbar artery approaches the iliac muscle fibers. In addition to it, the artery enveloping the thigh bone also takes part. The lumbar arteries supply the multifid muscle group.
Nerve endings
Good work of the muscle structure is possible thanks to the nerve endings. The activity of the iliac and piriformis muscle groups is controlled by the lumbar and sacral plexus. Due to this, the mobility of each joint is ensured. At the same time, the lumbar plexus is responsible for the iliac fibers, and the nerve endings of the sacrum follow the piriformis muscles.
The structure of the sacrum includes the gluteal plexus of nerve cells that control the work of the muscles of the same name. The spinal nerve canals are responsible for the innervation of the multifidine muscle group.
