Bones in Human Body (206), Types, Functions, Disorders

Bones in Human Body: Human bones are composed of connective tissue strengthened with calcium and specialised bone cells, including osteoblasts, osteocytes, and osteoclasts. Each bone within the human skeleton consists of layers, each housing a distinct type of bone tissue: the periosteum, compact tissue, cartilaginous tissue, and bone marrow. The body continually adjusts the skeleton by depositing new bone tissue when necessary and resorbing old tissue when no longer required. Maintaining healthy bones necessitates a well-balanced diet, regular weight-bearing exercise, and appropriate hormone levels.

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Bones in Human Body

Types of Bones in Human Body

1. Long Bones: These elongated skeletal elements, found in the arms, legs, fingers, and toes, have a tubular structure. Long bones provide structural support, allow for joint articulation, and house the bone marrow, which produces red blood cells.
2. Short Bones: These bones, similar in length and width, are primarily found in the wrists (carpals) and ankles (tarsals). Despite their small size, short bones play a significant role in skeletal stability and mobility, allowing for a wide range of motion.
3. Flat Bones: Flat bones are distinguished by their thin, flattened shape and include important anatomical structures such as the skull, ribs, and shoulder blades (scapulae). These bones serve two functions: they protect vital organs and provide anchorage points for muscle attachment.
4. Irregular Bones: Irregular bones, with their complex shapes that defy categorization, exemplify skeletal anatomy diversity. The vertebrae, facial bones, and pelvic bones are all good examples. They protect vital organs, provide structural support, and serve as sites for muscular attachment.
5. Sesamoid Bones: These small, rounded bones live within tendons, primarily near joints such as the knees, hands, and feet. The patella, the largest sesamoid bone, exemplifies their importance in increasing tendon durability and optimizing muscular mechanics.
6. Accessory Bones: These skeletal components vary in occurrence and morphology between individuals and deviate from the standard bone composition. Examples include extra bones or irregularities in bone size or shape, such as accessory bones in the feet (e.g., accessory navicular bone) or supernumerary ribs .

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Major Bones in Human Body

Axial Skeleton

• Skull: Protects the brain and houses the sensory organs. Comprising 22 bones, most of them are fused except for the lower jawbone (mandible).
• Vertebral column: Also known as the spine, it consists of 26 vertebrae providing support and flexibility to the body while safeguarding the spinal cord.
• Ribs: Forming the rib cage, the 12 pairs of ribs shield the heart and lungs, attaching to the thoracic vertebrae at the back and the sternum (breastbone) at the front.
• Sternum: Positioned at the front of the chest, this flat bone connects to the ribs, forming the front section of the rib cage.

Okazaki Fragments

Appendicular Skeleton

• Pectoral girdle: Links the upper limbs (arms) to the axial skeleton. Comprised of two clavicles (collarbones) and two scapulae (shoulder blades).
• Upper limbs: Consisting of the humerus (upper arm bone), radius and ulna (forearm bones), and hand bones (carpals, metacarpals, and phalanges).
• Pelvic girdle: Connects the lower limbs (legs) to the axial skeleton, formed by the fusion of the ilium, ischium, and pubis bones.
• Lower limbs: Comprising the femur (thigh bone), patella (kneecap), tibia (shinbone), fibula, and foot bones (tarsals, metatarsals, and phalanges).

Function of Bones in Human Body

1. Support: Bones provide a strong framework, similar to a building's foundation, that supports our body's shape and keeps our organs in their proper positions.
2. Movement: Bones and muscles work together as levers to facilitate movement. Muscles contract and pull on bones at joints, allowing you to bend your elbow or straighten your arm.
3. Protection: Bones protect vital organs such as the brain, heart, and lungs from harm.  For example, the skull protects the brain, whereas the rib cage protects the heart and lungs.
4. Mineral Storage: Bones hold essential minerals like calcium and phosphorus. These minerals are required for proper bone health, muscle function, and nerve communication. When the body's calcium levels drop, bones release calcium into the bloodstream to maintain balance.
5. Blood Cell Production: Soft bone marrow in certain bones generates blood cells. This marrow produces red blood cells, which transport oxygen, white blood cells, which fight infections, and platelets, which are necessary for blood clotting.

Systole and Diastole

Disorders of Bones in Human Body

• Osteoporosis: This condition renders bones fragile and prone to breakage. It predominantly affects older individuals, particularly women. Even minor accidents or falls can result in bone fractures.
• Osteopenia: This condition involves lower-than-normal bone density, though not to the extent of osteoporosis. If left untreated, osteopenia can advance to osteoporosis.
• Paget's disease of bone: This is a persistent condition causing abnormal breakdown and remodeling of bones, leading to weakness and deformity.
• Osteogenesis imperfecta (OI): OI is a genetic disorder characterized by brittle bones that are easily fractured. Its severity varies among individuals.
• Osteomyelitis: An infection of the bone, which can be instigated by bacteria, fungi, or viruses.
• Bone cancer: A relatively uncommon cancer originating within the bones.
• Rickets and osteomalacia: These conditions entail softening of the bones. Rickets occurs in children, while osteomalacia affects adults. Both are triggered by deficiencies in vitamin D or calcium.
• Arthritis: This term encompasses joint inflammation, with numerous types affecting the bones in joints.