The human skeletal system or skeleton is the total number of bones which join together (with the help of joints) in the body. It is the framework that helps in providing support, protection and shape to the body, thereby facilitating movement. Each bone is composed of multiple cells, minerals and protein fibers. Without a skeleton, we would not be able to perform our day to day activities like standing, sitting or walking. It also protects the soft tissues and inner parts of our body. For example, the skull covers and protects the brain which is very soft and ribs protect the lungs and heart. Talking about the number of bones in human body, it’s good to know that a newborn baby has about 300 bones and there are 206 bones in the skeletal system of an adult as they get fused as we grow up; multiple cartilage and ligaments also make up the skeletal system in our body.
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The human skeletal system is responsible for six major functions in our body which include protection, movement, support, storage of minerals, production of blood cells and endocrine regulation. We will further learn about the functions of each kind of bone forming the skeletal system in detail.
The axial skeletal system: It includes the skull, spine and rib cage.
The appendicular skeletal system: It includes the appendages and the girdles including pelvic girdle bones which are attached with the axial skeleton.
The axial skeletal system consists of 80 bones that run the midline axis of the body and as we learnt above, it includes regions like skull, spine, sternum, auditory ossicles, hyoid and ribs. Let’s know more about each of these.
The skull covers and protects the brain which is delicate and soft. It consists of cranium and facial bones where the function of the former kind of bone is to protect the brain and is formed of 8 plate-shaped bones joined together at sutures. The remaining 14 bones along with the cranium, form the facial bones. The only movable bone in the human skull is Mandible which forms the lower jaw and holds the lower teeth in the right position.
The spine or the vertebral column is an interconnected complex of bones, nerves, tendons, muscles, and ligaments. Any damage to these parts may cause pain and show neurological symptoms or even loss of mobility. The vertebral column consisting of 33 bones known as vertebrae are the bony building blocks of the spine. There are 5 categories of vertebrae namely cervical vertebrae, thoracic vertebrae, lumbar vertebrae, sacrum vertebrae and coccyx vertebrae. All of these spinal columns protect the spinal cord and provide stiffening and structural support to the bodyweight. The vertebral column is attached to the pectoral and pelvic girdle bones and muscles.
Also known as the breastbone, it is a long flat bone positioned at the central part of the chest or anteriorly to the thorax. It is situated at the midline of the chest. A rib cage is formed with this sternum via cartilage and the ribs. First seven ribs and the clavicle or collarbone are attached to the sternum. It protects the lungs, hearts and major blood vessels from injury.
It is the bone that provides muscle attachment to the floor of the mouth, the tongue, the larynx, the epiglottis and the pharynx. It is a U-shaped bone held in place by the strap muscles of the anterior triangle of the neck. It helps in swallowing as it supports the tongue and it has no articulation with other bones. It is regarded as an intermediary between the post cranial skeleton and the skull.
Also known as the ossicles, these are the three bones, namely, malleus, incus and stapes present in the middle ear and are the smallest ones in the human body. These help in transmitting sounds from the air to cochlea which is a fluid-filled labyrinth. Hearing loss may occur in the absence of auditory ossicles.
Ribs protect the heart and lungs which are the inner organs of our body. These are present as a set of 12 long curved bones forming a protective cage of the thorax. As part of the bony thorax, these protect the thoracic organs. The ribs or the bones here articulate with the vertebral column and terminate as cartilage namely costal cartilage, posteriorly and anteriorly, respectively.
Human skeletal system comprises the appendicular skeleton which supports the appendages. Consisting of 186 bones including those present in the limbs, pelvic girdles and pectoral girdles.The appendicular skeletal system has bones with six divisions as follows:
Shoulder Girdle - It is also called pectoral girdle which is the set of 4 bones connecting to the arm on each side. It is the part of the appendicular skeleton meant for the upper limbs. In humans, it consists of the clavicle and the scapula.
Arms and Forearms - This region consists of 6 bones that include humerus, radius and ulna as large bones.
Hands - It consists of 54 bones and these provide flexibility and support to the soft tissues found in hands. The hand bones are categorised into carpals, metacarpals and phalanges.
Pelvis - It is found in the lower part of the trunk as a ring-like bony structure It comprises two bones, namely coccyx and sacrum. Paired hip bones made of pubis, ischium and ilium are also part of pelvic girdle. Pelvic girdle functions in transferring the body weight from the axial skeleton to the appendicular component, helping in the movements. It is also attached to multiple muscles and ligaments, facilitating movement.
Thighs and Legs - Bones found here support the muscles of the lower limbs and help in walking, standing, running and jumping. These are strong bones supporting the body weight. Femur or the thigh bone is the largest and heaviest bone found in the human body. Tibia and Fibula are two other long bones present in the lower leg linked closely at the knee and ankle.
Feet and Ankles - Foot is the major and firmm platform that supports the whole weight of the body and the major bones present here include tarsals, phalanges and metatarsals.
1. What Are Tendons, Ligaments and Cartilages?
Tendons are part of the connective tissues that connect skeletal muscles to the bones. Ligaments are the bands of connective tissue that connect bones to other bones to form joints and cartilage is a softer, flexible and firm tissue which covers and protects the bones at the joints. It is present in ribs, ear, nose, intervertebral discs and bronchial tubes, to name a few.
2. What Are the Diseases Related to the Skeletal System?
The various diseases linked to the human skeletal system are osteoporosis, paget’s disease and arthritis. Osteoporosis is a bone-related disorder where bone density is minimal and it enhances the risks of bone fracture. Paget’s disease is a chronic bone disease that causes the affected bones to become weak and brittle. Arthritis is a joint inflammation where difficulty and pain in movements occur.