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Movement is vital for all of you because it provides you with the opportunity to live your lives to the full. Just as other human beings, you fall and stand up to continue moving forward. But what provides you with this opportunity? It is your skeletal system. It does not only facilitate your physical activity but also supports and protects your bodies. This system consists of hundreds of bones that are full of calcium, which makes them strong enough to carry your weight. Bones are connected with the help of joints that facilitate motion. The majority of you were born with about 300 bones that fuse with the course of time so that now you have only 206 bones. They all are divided into two parts: axial and appendicular skeletons.
Axial Portion of the Skeleton
Your axial portion of skeleton is composed of “the skull, the vertebral column, and the thoracic cage” (Skeletal System: Bones and Joints 120). Due to its location, it manages to protect your brain and spinal cord from injuries. In addition to that, it supports the organs in the ventral body cavity so that you do not need to carry them in your hands.
Twenty-two bones that are separated into two parts form the skull. You have 8 bones of the cranial cavity that are known as braincase. They surround your brain so that you do not hurt it when fall or receive a headnut. The rest of the bones (there are 14 of them) form your face. They are tightly connected to one another so that your nose is always in the right place. The only exception is the mandible that makes chewing possible. Otherwise, how would you eat? Minimal movement can also be observed within the middle ears. Each of them includes 3 auditory ossicles that are hidden deep in your head.
The vertebral column, or backbone, usually consists of “7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, 1 sacral bone, and 1 coccyx bone” (Skeletal System: Bones and Joints 125). It is the central axis of the skeleton that has four major curvatures. Normally, the cervical and the lumbar regions curve anteriorly. The thoracic, as well as the sacral and coccygeal regions, curves posteriorly. However, considering the way you sit, abnormal curvatures are widespread.
The thoracic or the rib cage protects your organs and supports them. All in all, human beings have 24 ribs that are divided into 12 pairs, but you can recount them to make sure. They are categorized according to their attachment to the sternum. Thus, a direct attachment by costal cartilages is true (1-7); an attachment by a common cartilage is false (8-12); and the absence of attachment resorts to floating ribs (11-12). The sternum, or breastbone, consists of three parts: “the manubrium, the body, and the xiphoid process” (Skeletal System: Bones and Joints 129).
Appendicular Portion of the Skeleton
Your appendicular skeleton consists of the bones of limbs and girdles so that you have:
- “4 bones in the shoulder girdle (clavicle and scapula each side)
- 6 bones in the arm and forearm (humerus, ulna, and radius)
- 58 bones in the hands (carpals 16, metacarpals 10, phalanges 28, and sesamoid 4)
- 2 pelvis bones
- 8 bones in the legs (femur, tibia, patella, and fibula)
- 56 bones in the feet (tarsals, metatarsals, phalanges, and sesamoid)” (“The Axial & Appendicular Skeleton” par. 4).
What would you be without this part of skeleton? Imagine that it is a big 3D puzzle, gathering all these bones together in a right order, you will build your arms and legs with all details. These are all movable parts that allow you to run, dance, write, and even hug your nearest and dearest. Even though the axial skeleton seems to be more important because it is connected with your brain, the appendicular portion of the skeleton contains about 60% of all your bones, which means that its importance should not be undervalued.
Functions of the Skeleton
As you have already understood, your skeleton maintains a lot of different functions. Some of them, such as movement and support, were already mentioned. But let us discuss them all in detail.
- Support. Your bodies are supported by the skeleton so that you can change your position to vertical one and stand strait. Without it, you would be able only to lie because of the gravitation. This function is provided by many bones but the long ones seem to be the leaders in this competition. For instance, those that are in legs, support the trunk. Similarly, vertebras support one another so that eventually the firs one provides support to the skull. In addition to that, they support the organs and ensure that they do not change their positions.
- Protection. The skeleton also protects you. For example, the skull prevents fatal brain injuries. The rib cage protects such vital organs as the heart and lungs. It also takes care of your abdominal organs ensuring that they develop normally.
- Movement. The function of bodily motion allowed you to come here today. However, it is critical to remember that it is maintained not only due to the bones but also with the help of the muscular system.
- Mineral and energy storage. From the outer side of your bones, there is a tissue that serves as a storage. It gathers calcium and phosphorus and withdraws them to maintain appropriate blood levels. In addition to that, mature bones store yellow marrow. It consists of fat almost totally and provides you with energy for various activities.
- Blood-cell formation. The inner core of your bones takes part in the formation of blood cell and platelet. It is known as bone marrow or red marrow. Platelet is vital for you because it ensures your ability to heal wounds while blood cells spread oxygen and destroy infectious cells (CAERT 3).
Relationship between the Skeletal System and the Muscular System
Have you ever thought of the way our movement are maintained? Even a simple nod of the head requires the cooperation between the skeletal and muscular systems. Muscles ensure movement of our body through the attachment to the bones. All in all, there are about 700 of them, which is an enormous amount that comprises about 50% of your weight.
So what happens in your body when you moves? When you want to move, your brain sends a message for the body to release energy. In medical terms, it is called adenosine triphosphate. Affecting your muscles, it makes them contract or shorten. Shortened muscles pulls bones at their insertion point. Thus, the angle between the bones connected by a joint shortens. Relaxation is maintained when the opposing muscle extends and pulls a bone to its initial position.
Sexual Differences in Skeletons
Human skeletons seem to be similar, as they contain the same bones. However, you should remember that their characteristics differ depending on the gender. For example, women have lighter pelvis bones that form a shorter cavity with less dimensions. It has less prominent marking for muscles and more circular pelvic brim. The sacral bones of men are longer and narrower, which makes them more massive. Their femur is also longer and heavier. Its texture is rough unlike women’s smooth.
Muscle marking is more developed and shaft is less oblique. The head of men’s femur is larger and trochanters are more prominent. The femoral neck angle in males is more than 125 and in females is less than 125. Women’s sternum is less than twice the length of manubrium and larger in men. Differences in skull include greater capacity, thicker walls, more marked muscular ridges, prominent air sinuses, smoother upper margin of orbit, less vertical forehead, and heavier cheekbones in males.
Clinical Conditions and Disorders that Affect the Skeleton
Hopefully, it will never affect any of you but the skeleton may be affected by tumours that cause bone defects. People may have skeletal developmental disorders including gigantism, dwarfism, osteogenesis imperfecta, and rickets lead to abnormal body sizes, brittle bones, and growth retardation. Bacterial infections cause inflammation and lead to bone destruction.
Decalcification, including the known to you osteoporosis, reduces bone tissue and softens bones. Joint disorders often deal with inflammation. For instance, arthritis. They are often influenced by age and physical activity. In this way, degradation of joints is observed in the elderly but can be delayed due to regular exercises. The abnormal curvatures of the spine may also cause health issues. That is why you should pay attention to your back posture and avoid kyphosis (a hunchback condition), lordosis (a swayback condition), and scoliosis (an abnormal lateral curvature).
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CAERT. Structures and Functions of the Skeletal System. 2014.
Skeletal System: Bones and Joints. 2012.
“The Axial & Appendicular Skeleton.” TeachPE, 2017.