Structure and Function of the Skeletal System PDF

Structure and Function of the Skeletal System Types of Bones in the Human Body 1 Long Bones 2 Short Bones Found in the limbs, long bones like Located in the wrists and ankles, the femur and humerus provide compact short...

Structure and Function of the Skeletal System Types of Bones in the Human Body 1 Long Bones 2 Short Bones Found in the limbs, long bones like Located in the wrists and ankles, the femur and humerus provide compact short bones like carpals leverage for movement, with a shaft and tarsals offer stability and and two ends optimized for strength weight-bearing in high-stress areas. and mobility. 3 Flat and Irregular Bones Flat bones, like the skull, protect vital organs, while irregular bones, such as vertebrae, have specialized shapes for their functions. Structure of Long Bones 1 Diaphysis The shaft of the long bone, composed primarily of dense cortical bone. This cylindrical structure provides strength and resistance to bending and torsion forces. 2 Epiphyses The ends of long bones, consisting mainly of cancellous bone. These regions are crucial for joint formation and are covered by articular cartilage to facilitate smooth movement. 3 Epiphyseal Plate A cartilaginous growth region in developing bones, responsible for longitudinal bone growth. In adults, this plate calcifies, forming the epiphyseal line. 4 Articular Cartilage A smooth, avascular tissue covering joint surfaces. It reduces friction and absorbs shock, allowing for pain- free movement of articulating bones. Bone Composition: Cells and Tissue Osteoblasts Osteocytes These bone-forming cells Mature bone cells embedded synthesize and secrete in the bone matrix. They collagen and other proteins maintain bone tissue by to form the organic matrix of regulating mineral bone. They are crucial in the concentration and responding process of ossification and to mechanical stresses. bone growth. Osteoclasts Bone Tissue Types Large, multinucleated cells Cortical bone provides responsible for bone strength and support, while resorption. They break down cancellous bone offers a site bone tissue, releasing for hematopoiesis and rapid minerals and allowing for remodeling due to its porous bone remodeling and repair. structure. Bone Tissue and Microstructure Osteon (Haversian System) Trabeculae Periosteum and Endosteum The fundamental functional unit of The lattice-like structure found in The periosteum is a tough, fibrous cortical bone. It consists of concentric cancellous bone. These interconnected membrane covering the outer bone layers of bone matrix (lamellae) bony plates and rods provide strength surface, while the endosteum lines surrounding a central canal containing while maintaining a low density, internal bone cavities. Both contain blood vessels and nerves. allowing for lightweight yet strong blood vessels and cells crucial for bone bones. growth and repair. Bone Marrow and Blood Supply Red Bone Marrow Yellow Bone Marrow Blood Supply Located primarily in flat bones and Found mainly in the medullary cavity Bones receive blood through the epiphyses of long bones, red of long bones, yellow marrow consists periosteal arteries, nutrient arteries, marrow is the site of hematopoiesis. It primarily of fat cells. It serves as an and metaphyseal arteries. This rich produces red blood cells, white blood energy reserve and can convert back blood supply supports bone cells, and platelets, crucial for oxygen to red marrow if increased blood cell metabolism, provides nutrients, and transport, immune function, and blood production is needed. facilitates waste removal, essential for clotting. bone health and function. Bone Formation and Maintenance Osteogenesis 1 The process of bone formation begins before birth and continues through adolescence. It involves the differentiation of mesenchymal stem cells into osteoblasts, which then produce the bone matrix. 2 Bone Remodeling A lifelong process where old bone tissue is removed by osteoclasts and replaced with new bone formed by osteoblasts. This cycle maintains bone strength and mineral homeostasis. Influencing Factors 3 Physical activity, nutrition, and hormones play crucial roles in bone health. Weight-bearing exercises stimulate bone formation, while adequate calcium and vitamin D intake support mineralization. Factors Affecting Bone Health Physical Activity Regular weight-bearing and resistance exercises stimulate bone formation, increasing bone density and strength. This is particularly important during childhood and adolescence for building peak bone mass. Dietary Needs Calcium (1000-1200 mg/day) and Vitamin D (600-1000 IU/day) are crucial for bone health. Adequate protein intake also supports bone matrix formation and maintenance. Hormonal Influence Parathyroid hormone (PTH) and calcitonin regulate calcium levels, while sex hormones like estrogen and testosterone play vital roles in bone metabolism and density maintenance.