SKELETAL SYSTEM

• Bone tissue is a dynamic and living part of our bodies, playing a vital role in maintaining homeostasis through support, protection, blood cell production, and mineral storage.
• Bone tissue continually grows, remodels, and repairs itself, providing support and protection to the body.
• Bone tissue produces blood cells and stores minerals and triglycerides.
• The skeleton acts as a structural framework for the body, supporting soft tissues and providing attachment points for muscles.
• The skeleton safeguards internal organs, for example, cranial bones protecting the brain and ribcage protecting the heart and lungs.
• Skeletal muscles attach to bones, allowing movement.
• Bone stores minerals, especially calcium and phosphorus, maintaining critical mineral balances in the body.
• Red bone marrow within certain bones produces blood cells, a process known as hemopoiesis.
• Yellow bone marrow stores triglycerides as an energy reserve.
• Long bones, like the humerus, have distinct parts: the diaphysis, epiphyses, metaphyses, articular cartilage, periosteum, medullary cavity, and endosteum.
• Bone, or osseous tissue, consists of an extracellular matrix: approximately 15% water, 30% collagen fibers, 55% crystallized mineral salts, with the primary mineral salt being calcium phosphate [Ca3(PO4)2].
• Treatment typically involves multidrug chemotherapy and may include the removal of the malignant growth or amputation of the affected limb.
• Calcium phosphate combines with calcium hydroxide [Ca(OH)2] to form hydroxyapatite [Ca10(PO4)6(OH)2].
• Other mineral salts and ions like calcium carbonate (CaCO3), magnesium, fluoride, potassium, and sulfate contribute to tissue hardening through calcification.
• Calcification is the process of mineral salts crystallizing within the collagen fibers of the extracellular matrix, initiated by bone-building cells called osteoblasts.
• Bone's hardness relies on crystallized mineral salts, while flexibility is maintained by collagen fibers, providing tensile strength.
• Dissolving mineral salts in an acidic solution, like vinegar, makes bone flexible.
• Osteoclasts, bone cells, break down both mineral salts and collagen fibers in bone.
• Stem cells derived from mesenchyme are known as osteoprogenitor cells.
• In long bones, spongy bone forms the core of the epiphyses beneath a thin layer of compact bone and a rim bordering the medullary cavity of the diaphysis.
• Numerous small blood vessels within the marrow provide nourishment to osteocytes, the bone cells.
• Osteoclasts are large cells derived from monocytes that release enzymes and acids to digest bone matrix, a process known as bone resorption.
• The final arrangement of spongy bone is established once locomotion is fully learned.
• Circumferential lamellae line the outer and inner circumference of long bone shafts.
• Trabeculae are the primary structural components of spongy bone.
• Spongy bone in the hip bones, ribs, sternum, vertebrae, and the proximal ends of the humerus and femur plays a crucial role in blood cell production.
• Compact bone always protects spongy bone, ensuring its safety.
• Each osteon has concentric lamellae, an osteonic canal, lacunae with osteocytes, and canaliculi.
• This orientation helps bones resist stresses and distribute forces without breaking.
• Trabeculae in spongy bone support and protect red bone marrow, making it the primary site for hemopoiesis (blood cell production) in adults.
• Spongy bone tissue is always found within the interior of bones, shielded by a layer of compact bone.
• Compact bone tissue is composed of repeating units called osteons or haversian systems.
• Spongy bone adapts its arrangement as lines of stress change due to factors like fractures or deformities.
• Interstitial lamellae are fragments of older osteons.
• This weight reduction allows bones to move more efficiently when pulled by skeletal muscles.
• Blood vessels and nerves enter through interosteonic canals.
• Compact bone resists bending and fractures due to the organization of osteons.
• These spaces in spongy bone tissue hold red bone marrow for blood cell production and yellow bone marrow (adipose tissue) in different bones.
• Blood supply to long bones enters through the periosteum and outer compact bone, passing through nutrient foramina into the inner compact bone and red bone marrow, and supplying the metaphyses and epiphyses.
• Spaces between trabeculae in spongy bone tissue are visible to the naked eye and contain bone marrow.