5 major functions of skeletal system: Types, structure

Edited By Irshad Anwar | Updated on Jul 02, 2025 06:46 PM IST

What Is A Skeletal System?

The skeletal system consists of bones in continuation with related connective tissues that give form, protection, and movement to the human body. In the skeleton system of an adult, there are 206 bones. It includes the skull, spine, ribs, and appendages that are articulated by joints and supported by cartilages, ligaments, and tendons. Some of the major functions include the provision of the overall outline of the body, the attachment points or sites on which muscles are anchored for effective movement, and protecting vital body organs such as the heart, brain, lungs, and liver. The other function is the production of blood cells through the process called erythropoiesis in the bone marrow. In addition, it provides further maintenance of some of the key minerals in the body, such as calcium and phosphorous, via the skeleton.

Components Of Skeletal System

Bones are rigid, hard organs comprising part of the skeleton in most vertebrate animals. Bones support and protect the body's various organs and support body weight.
Bones work as levers and store important minerals, such as calcium and phosphate, releasing them to the bloodstream as needed.
The marrow inside a few bones is the location of the synthesis of blood cells through the process called hematopoiesis.
A cartilage is a flexible form of connective tissue that takes place in several locations in the body, for instance, the joints in the ear and nose, and the intervertebral disks.
It provides cushion-bearing properties and reduces friction in the joints to enable smooth and frictionless movement of the body to be relieved from unwanted pain.
Joints are those parts of the skeleton where two or more bones meet. Accordingly, it provides different bowel degrees of movement and flexibility.
There could be fixed, semi-movable, and freely movable joints that offer all sorts of movements.
Ligaments are relatively elastic, tough forms of fibrous connective tissue that bind bone to bone and thereby provide strength to the joints of the body.
Ligaments aid in holding internal organs in their respective places.
The ligaments keep the bones together, maintaining alignment and preventing harmful or excessive movements of bones in a joint, thereby avoiding injury.
Tendons are tough, flexible bands of tissues that connect muscles to bones.
Tendons serve the basic function of passing the force that is developed through the muscles for appropriate articulation of the bones to create motion.
Tendons also help in joint stability by supporting muscle alignment while the muscles are contracted and, thus, motion.

Functions Of Skeletal System

The functions are discussed below-

Support

The skeleton supports the form of the body by the weight of tissues and organs, by position, as well as by the body's erect position, which reduces the pressure in the tissues.
The skeleton provides a framework for the body; hence, it gives it basic support and stays on.
The skeleton further functions to support the form of the body and tissues, organs and weight, besides the body's erect position.
The rigidity of the bones provides muscular attachments and distributes the mechanical loads during activities such as standing, walking, and lifting.

Examples of key bones that contribute to support

Vertebral Column: Another very important columnar supporting structure includes the spine or vertebral column, which maintains the erect posture of the body by balanced rigidities and protects the spinal cord. This is an individual column of vertebrae that absorb and then distribute mechanical stresses.

Pelvis: It takes the weight of the upper body, directly by way of support for the legs, in sitting and standing. Furthermore, it provides support for the lower abdominal organs, and it provides a base of support for the lower limbs during the movement of walking and running.

Protection

The skeletal system provides this protective function because it envelops all of the vital organs with bony structures. Such a protective function remains very crucial in ensuring protection against mechanical injury or trauma to the delicate internal organs.

Skull: Protection of the brain

The skull is a bony rigid enclosure that envelops the brain to protect it from mechanical shocks and concussions. It is composed of the basic cranium, which holds the brain, and also, the facial bones to further strengthen and protect the facial area. The skull provides a means of protection for the brain from massive injuries through its muscular and firm structures.

Rib cage: Protection of the heart and lungs

The cage is formed of 12 pairs of ribs that arise from the thoracic vertebrae into the sternum. This provides the covering of the heart and lungs against shocks and weights. Again, it participates in the mechanics of breathing by facilitating the expansion and contraction of the chest cavity.

Vertebrae: Protection of the spinal cord

The vertebral column or spine protects and envelops the spinal cord, a component of the central nervous system. The spinal cord is guarded from injuries or compressive forces by the composite structure of the vertebrae along with the spinal canal; however, this also gives flexibility and mobility to the trunk.

Movement

The bones are a rigid framework to which the muscles of the body are attached. Muscles are contraction machines that bend and straighten parts of the body, twist, pull, pump body fluids, and perform many other important functions. The contraction has the effect of pulling the tendons connected to a bone, rotating the bone at the joint.

Ball-and-socket Joints: This joint allows a wide, extensive movement in many directions. The shoulder and hip are the typical joints in which the rounded head of one bone slips into the cup-like of another.

Hinge Joints: They allow movement in only one direction similar to a door swinging open or shut. It's found in the elbow and knee joints that allow 'flexion and extension".

Musculoskeletal interaction: The musculoskeletal system acts as an integrated system in which the action can be performed by the bones, muscles, and joints. It is the muscles that contract and apply forces on the bones through tendons. These bones articulate at joints and perform motion. It is this articulation that allows the execution of highly complex activities and adjustment in posture supporting gross motor activities to be carried out.

Mineral Storage

The more likely of these are measured in the body to be calcium and phosphorus. Bones facilitate the storage of homeostatic reserves for major minerals, with the highest account held in reserves of calcium and phosphorus in the matrix of the bone.

Importance of mineral storage

The functions that bones perform by storing and releasing unlock means for mineral storage to contribute to the general homeostasis of minerals, thereby being useful for other physiological processes. Calcium and phosphorus are obligate needs for not only the skeleton but also for individual nerve impulse transmission, muscle contraction, or blood clotting.

Blood Cell Production

Hematopoiesis is a process through which there is derived blood production in the red marrow from stem cells located in the bone. It involves the differentiation of hematopoietic stem cells into different types of blood cells, precisely: red blood cells, white blood cells, and platelets. These cells require a microenvironment in which to mature and be released into the bloodstream.

Types of blood cells produced

Red Blood Cells (Erythrocytes): These cells take oxygen from the lungs to all the tissues of the body, while also returning carbon dioxide originating in the body's tissues back to vacate from the lungs. They are biconcave in shape and have no nucleus.

White Blood Cells or Leukocytes: The cells forming the very basis of the immune response, most importantly against an infection or disease, further categorized as neutrophils lymphocytes, and monocytes with their specific functions in their mechanism of immune guarding.

Locations of bone marrow

The bone marrow is mainly found within osseous tissue in the central cavities, as in long bones of the femur and humerus and flat bones like the pelvis, sternum, and ribs. In adults, most active hematopoiesis takes place in the red bone marrow of the pelvis-kidneys, girdle, sternum, and proximal heads of the femur and humerus at an approximate rate of making 5 million red blood cells per second.

Frequently Asked Questions (FAQs)

1. What are the major functions of the skeletal system?

The skeletal system, in addition to providing structural support and shape to the body, protects vital organs, helps in various movements on account of the joints, and attaches to muscles. More important is its role in storing vital minerals like calcium and phosphorus and its action in producing blood cells within the marrow of the bones.

2. How does the skeletal system provide support to the body?

The skeletal system is supportive in that it operates as a rigid framework that assists in keeping the form and upright attitude of the body. Bones support and distribute the weight of tissues and organs and are strong enough to serve as attachment points for muscles tending to balance and stabilise the body.

3. Which bones protect vital organs in the human body?

The essential bones that protect the vital organs are the skull, which covers the brain, the rib cage, and the vertebral column, within which the spinal cord is housed.

4. How do bones facilitate movement?

Bones allow movement by acting as levers—forces applied to the bones then create movement at the joints. The muscle first contracts, then yank on the bones by tendons, causing motion at the joints. The shape and structure of bones and joints allow a broad range of different movements—bend, rotate, stretch—and admit varied ranges of flexibility.

5. What role do bones play in blood cell production?

The important role of bones is to produce blood cells in a process called hematopoiesis, which takes place in the bone marrow. Marrow is composed of cells and tissues within the cavitation of some bones. It produces red blood cells, white blood cells, and platelets that, when combined, are crucial for oxygen carriage, immunity to diseases, and blood clotting.

6. What are the two main types of bone tissue?

The two main types of bone tissue are compact (cortical) bone and spongy (trabecular) bone. Compact bone is dense and forms the outer layer of bones, while spongy bone has a honeycomb-like structure and is found inside bones, particularly at the ends of long bones.

7. How does the structure of compact bone differ from spongy bone?

Compact bone has a dense, solid structure with concentric layers called lamellae arranged around central canals. Spongy bone, in contrast, consists of a network of interconnected trabeculae (bone spicules) with spaces in between, giving it a porous appearance.

8. What is an osteon, and what is its function?

An osteon, also called a Haversian system, is the basic structural unit of compact bone. It consists of concentric layers of bone matrix (lamellae) surrounding a central canal containing blood vessels and nerves. Osteons provide strength and allow for nutrient distribution within the bone.

9. How do bones grow in length?

Bones grow in length through a process called endochondral ossification. This occurs at the epiphyseal plates (growth plates) located at the ends of long bones. Cartilage cells in these plates divide and grow, then transform into bone tissue, gradually increasing the bone's length.

10. What is the difference between intramembranous and endochondral ossification?

Intramembranous ossification involves the direct transformation of mesenchymal tissue into bone, typically in flat bones like the skull. Endochondral ossification, on the other hand, involves the replacement of a cartilage model with bone tissue and is the process by which most bones in the body form and grow.

11. What are the 5 major functions of the skeletal system?

The 5 major functions of the skeletal system are: 1) Support for the body, 2) Protection of vital organs, 3) Movement through muscle attachment, 4) Blood cell production in bone marrow, and 5) Mineral storage and homeostasis.

12. How does the skeletal system provide support for the body?

The skeletal system provides support by acting as a framework that gives the body its shape and allows us to stand upright. Bones are rigid structures that can bear weight and resist compression, providing a solid foundation for muscles and other tissues to attach to.

13. Which bones are primarily responsible for protecting vital organs?

Several bones protect vital organs: the skull protects the brain, the ribcage protects the heart and lungs, the vertebral column protects the spinal cord, and the pelvis protects reproductive organs. These bones form protective cavities or cages around delicate organs.

14. How does the skeletal system facilitate movement?

The skeletal system facilitates movement by providing attachment points for muscles. Bones act as levers, and when muscles contract, they pull on bones, causing them to move. This interaction between bones and muscles, along with joints, allows for a wide range of body movements.

15. What is the role of bone marrow in the skeletal system?

Bone marrow, found inside certain bones, plays a crucial role in blood cell production (hematopoiesis). Red bone marrow produces red blood cells, white blood cells, and platelets, while yellow bone marrow stores fat.

16. How do joints contribute to the skeletal system's function?

Joints are connections between bones that allow for movement. They contribute to the skeletal system's function by providing flexibility and a range of motion. Different types of joints (e.g., hinge, ball-and-socket) allow for various types of movement, enhancing the body's overall mobility.

17. How does the skeletal system interact with the muscular system?

The skeletal and muscular systems work together in a relationship called the musculoskeletal system. Muscles attach to bones via tendons, and when muscles contract, they pull on bones, causing movement. The bones provide leverage, while the muscles provide the force for movement.

18. What is osteoporosis, and how does it relate to the skeletal system's functions?

Osteoporosis is a condition characterized by decreased bone density, making bones fragile and more susceptible to fractures. It directly impacts the skeletal system's support and protection functions. Osteoporosis occurs when bone resorption outpaces bone formation, often due to factors like aging, hormonal changes, or certain medications.

19. What is the role of vitamin D in skeletal health?

Vitamin D plays a crucial role in skeletal health by promoting calcium absorption in the intestines and helping to maintain appropriate calcium and phosphate concentrations in the blood. This allows for proper mineralization of bone tissue. Vitamin D deficiency can lead to weakened bones and conditions like rickets in children or osteomalacia in adults.

20. What is the role of collagen in bone structure?

Collagen is a protein that forms the organic component of bone matrix. It provides flexibility and tensile strength to bones, allowing them to withstand stretching and twisting forces. Collagen fibers form a framework upon which mineral crystals (mainly hydroxyapatite) are deposited, creating the composite material that gives bone its unique combination of strength and flexibility.

21. How do bones remodel throughout life?

Bone remodeling is a continuous process where old bone tissue is removed (resorption) by cells called osteoclasts, and new bone tissue is formed (deposition) by cells called osteoblasts. This process allows bones to adapt to changing mechanical needs and repair microdamage.

22. What factors influence bone density?

Bone density is influenced by various factors including genetics, age, sex hormones, physical activity, diet (especially calcium and vitamin D intake), and certain medical conditions or medications. Regular weight-bearing exercise and a balanced diet can help maintain or improve bone density.

23. How does exercise affect bone health?

Weight-bearing and resistance exercises stimulate bone formation, increasing bone density and strength. This occurs through a process called mechanotransduction, where mechanical stress on bones triggers cellular responses that promote bone growth. Regular exercise also improves balance and coordination, reducing the risk of falls and fractures.

24. What is the relationship between bone health and kidney function?

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25. How does the skeletal system contribute to mineral homeostasis?

The skeletal system acts as a reservoir for minerals, particularly calcium and phosphorus. Bones can release or absorb these minerals as needed, helping to maintain proper mineral levels in the blood and throughout the body, which is crucial for various physiological processes.

26. How does the skeletal system change with age?

As we age, bone density tends to decrease, bones become more brittle, and the rate of bone formation slows down compared to bone resorption. This can lead to conditions like osteoporosis. Additionally, joints may become less flexible, and the production of synovial fluid (which lubricates joints) may decrease.

27. What is the difference between red and yellow bone marrow?

Red bone marrow is responsible for hematopoiesis (blood cell production) and is found in the spongy bone of the skull, ribs, vertebrae, and ends of long bones. Yellow bone marrow, found in the hollow interior of long bones, consists mainly of fat cells and serves as an energy reserve.

28. What is the role of cartilage in the skeletal system?

Cartilage plays several roles in the skeletal system: it provides a smooth surface at joints to reduce friction, acts as a shock absorber, forms a model for bone growth during development, and allows for some flexibility in certain structures like the nose and ears.

29. What is the function of the periosteum?

The periosteum is a tough, fibrous membrane that covers the outer surface of bones (except at joints where cartilage is present). It plays crucial roles in bone growth, repair, and nutrition by containing blood vessels, nerves, and bone-forming cells (osteoblasts).

30. How do bones store and release calcium?

Bones store calcium in their mineral matrix, primarily in the form of hydroxyapatite crystals. When blood calcium levels drop, parathyroid hormone stimulates osteoclasts to break down bone tissue, releasing calcium into the bloodstream. When calcium levels are high, calcitonin promotes calcium deposition in bones.

31. What is the difference between osteoblasts and osteoclasts?

Osteoblasts are bone-forming cells that synthesize and secrete bone matrix, contributing to bone growth and repair. Osteoclasts, on the other hand, are large, multinucleated cells that break down bone tissue, playing a crucial role in bone remodeling and calcium homeostasis.

32. How do hormones influence the skeletal system?

Several hormones influence the skeletal system. For example, growth hormone and insulin-like growth factor promote bone growth. Sex hormones (estrogen and testosterone) help maintain bone mass. Parathyroid hormone and calcitonin regulate calcium homeostasis. Thyroid hormones influence bone remodeling and maturation.

33. How do bones contribute to acid-base balance in the body?

Bones contribute to acid-base balance by acting as a buffer system. When blood becomes too acidic, bones can release alkaline minerals (like calcium) to help neutralize the acid. Conversely, if blood becomes too alkaline, bones can absorb these minerals. This process helps maintain the body's pH within a narrow, healthy range.

34. What is the difference between compact bone and spongy bone in terms of function?

While both types provide support, compact bone is dense and strong, forming the outer layer of bones and providing maximum strength with minimum weight. Spongy bone, found inside bones, has a more open structure that allows for flexibility and shock absorption. Spongy bone also houses red bone marrow, crucial for blood cell production.

35. How does the skeletal system adapt to different mechanical stresses?

The skeletal system adapts to mechanical stresses through a process called bone remodeling. When bones experience increased stress (like during exercise), they respond by depositing more bone tissue, becoming stronger and denser. Conversely, lack of stress (like in prolonged bed rest) can lead to bone loss. This adaptation follows Wolff's Law, which states that bone adapts to the loads it is placed under.

36. How do bones contribute to the body's immune system?

Bones contribute to the immune system primarily through the production of immune cells in the bone marrow. The bone marrow produces various types of white blood cells, including lymphocytes, which are crucial for immune responses. Additionally, bones can produce proteins that act as part of the innate immune system, helping to fight off pathogens.

37. What is the significance of the skeletal system in human evolution?

The skeletal system has played a crucial role in human evolution. Changes in skeletal structure, particularly in the pelvis, spine, and skull, allowed for bipedal locomotion, increased brain size, and changes in facial structure. These skeletal adaptations reflect major evolutionary shifts in human physiology and behavior, such as upright walking and increased cognitive capacity.

38. How does the skeletal system contribute to energy metabolism?

The skeletal system contributes to energy metabolism in several ways. Yellow bone marrow stores fat, which can be used as an energy source. Additionally, bones secrete hormones like osteocalcin, which influences glucose metabolism and energy expenditure. The process of bone remodeling itself also requires energy, contributing to overall body metabolism.

39. What is the relationship between the skeletal system and the endocrine system?

The skeletal system and endocrine system have a complex relationship. Bones respond to various hormones like growth hormone, parathyroid hormone, and sex hormones. Conversely, bones themselves are now recognized as endocrine organs, producing hormones like osteocalcin and fibroblast growth factor 23, which influence metabolism and mineral homeostasis throughout the body.

40. How do bones aid in detoxification?

Bones aid in detoxification by sequestering heavy metals and other toxic substances from the bloodstream. These toxins can be incorporated into the bone matrix, effectively removing them from circulation. However, this can also pose a risk if the bones are later broken down, potentially releasing these stored toxins back into the body.

41. What is the role of the skeletal system in thermoregulation?

While not its primary function, the skeletal system contributes to thermoregulation. Bones can store or release heat, helping to maintain body temperature. Additionally, shivering, a mechanism for generating heat, involves rapid contraction of skeletal muscles attached to bones. The bone marrow's extensive blood supply also plays a role in distributing heat throughout the body.

42. How does the skeletal system change during spaceflight?

In microgravity environments like spaceflight, the skeletal system undergoes significant changes. Without the constant force of gravity, bones experience decreased mechanical stress, leading to bone loss and decreased density. This process, similar to accelerated osteoporosis, can weaken bones and increase the risk of fractures upon return to Earth's gravity.

43. What is the function of red bone marrow versus yellow bone marrow?

Red bone marrow is primarily responsible for hematopoiesis, the production of blood cells including red blood cells, white blood cells, and platelets. It's found in the spongy bone of flat and short bones, and the epiphyses of long bones. Yellow bone marrow, found in the medullary cavity of long bones, is composed mostly of fat cells and serves as an energy reserve. However, yellow marrow can convert back to red marrow if needed, such as in cases of severe blood loss.

44. How do bones contribute to mineral homeostasis beyond calcium?

While calcium is the most well-known mineral associated with bones, they also play a crucial role in the homeostasis of other minerals. Bones store and regulate levels of phosphorus, magnesium, sodium, and other trace elements. For example, bones contain about 85% of the body's phosphorus, which is essential for energy metabolism and cell signaling.

45. What is the role of osteocytes in bone function?

Osteocytes are mature bone cells embedded within the bone matrix. They play a crucial role in maintaining bone structure and function. Osteocytes act as mechanosensors, detecting mechanical stress on bones and signaling for appropriate bone remodeling. They also regulate mineral homeostasis and communicate with other cells through a network of tiny canals called canaliculi.

46. How does the skeletal system contribute to blood pH regulation?

The skeletal system helps regulate blood pH through a process called bone buffering. When blood becomes too acidic, bones release alkaline minerals like calcium and magnesium to neutralize the acid. Conversely, if blood becomes too alkaline, bones can absorb these minerals. This process helps maintain the body's pH within the narrow range necessary for proper physiological function.

47. What is the relationship between the skeletal system and the nervous system?

The skeletal system and nervous system are closely interconnected. Bones protect vital parts of the nervous system, such as the brain and spinal cord. The nervous system controls muscle contractions that move bones. Additionally, bones contain numerous nerve endings that provide sensory information about position, movement, and pain. This sensory feedback is crucial for proprioception and coordinated movement.

48. How do bones contribute to sound transmission in hearing?

In the middle ear, three small bones called ossicles (the malleus, incus, and stapes) play a crucial role in hearing. These bones transmit and amplify sound vibrations from the eardrum to the inner ear. This demonstrates a specialized function of certain bones beyond the typical roles of the skeletal system.

49. What is the significance of bone density in overall health?

Bone density is a measure of bone strength and is crucial for overall health. Adequate bone density reduces the risk of fractures, supports proper posture, and ensures effective protection of internal organs. Beyond these structural roles, bone density is also linked to overall metabolic health, as bones are involved in energy metabolism and endocrine functions.

50. How does the skeletal system change during pregnancy?

During pregnancy, the skeletal system undergoes several changes. The mother's bones may experience some decrease in density as calcium is used for fetal bone development. The pelvis ligaments become more flexible to accommodate childbirth. Additionally, postural changes occur as the center of gravity shifts, which can affect the spine and hip joints.

51. What is the role of the skeletal system in locomotion?

The skeletal system is fundamental to locomotion. Bones act as levers, providing the rigid structure necessary for movement. Joints between bones allow for various types of motion. Muscles attached to bones via tendons contract to move these bony levers. The specific shapes and arrangements of bones, particularly in the limbs and vertebral column, are adapted for efficient bipedal locomotion in humans.

52. How do bones contribute to the body's overall energy storage?

Bones contribute to energy storage in multiple ways. Yellow bone marrow, found in the hollow interior of long bones, is primarily composed of fat cells and serves as an energy reserve. Additionally, the protein matrix of bones can be broken down for energy in extreme cases of starvation. Bones also play a role in overall energy metabolism through the production of hormones like osteocalcin.