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Human Skeleton:
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| What is the Skeleton for? The human skeleton is made up of around 206 fused or individual bones, which give our bodies its shape; it is supported and supplemented by Ligaments, Tendons, Muscles and Cartilage to provide movement; it serves as a scaffold which supports the organs, it anchors the muscles. The skeleton also protects your vital organs; the Skull protects the brain, the eyes and the middle and inner ears; the Vertebrae protects the spinal cord; the Rib Cage, Spine, and Sternum protect the lungs, heart and major blood vessels; the Clavicle and Scapula protect the shoulder; the Ilium and Spine protect the digestive and urogenital systems and the hip; the Patella and the Ulna protect the knee and the elbow respectively and the Carpals and Tarsals protect the wrist and ankle respectively. Blood Cell Production: The skeleton is the site of Haematopoiesis, which takes place in red bone marrow; there are two types of bone marrow, red marrow, consisting mainly of myeloid tissue and yellow marrow, consisting mainly of fat cells; red blood cells, platelets and most white blood cells arise in red marrow andsome white blood cells develop in yellow marrow. Both types of bone marrow contain numerous blood vessels and capillaries; at birth, all bone marrow is red; with age, more and more of it is converted to the yellow type; red marrow is found mainly in the flat bones, such as the hip bone, breast bone, skull, ribs, vertebrae and shoulder blades and in the cancellous, spongy, material at the epiphyseal ends of the long bones such as the femur and humerus; yellow marrow is found in the hollow interior of the middle portion of long bones. Calcium and Iron Storage: Bone matrix can store calcium and is involved in calcium metabolism and bone marrow can store iron in ferritin and is involved in iron metabolism; however, bones are not entirely made of calcium, but a mixture of chondroitin sulfate and hydroxyapatite, the latter making up 70% of a bone. Endocrine Regulation: Bone cells release a hormone called Osteocalcin, which contributes to the regulation of blood sugar (glucose) and fat deposition; Osteocalcin increases both the Insulin secretion and sensitivity, in addition to boosting the number of insulin producing cells and reducing stores of fat. At birth, a newborn baby has over 300 bones, whereas on average an adult human has 206 bones; this can vary slightly between individuals; the difference comes from a number of small bones that fuse together during growth, such as the Sacrum and Coccyx of the vertebral column; other fused bones include those of the pelvis and the cranium. Not all bones are interconnected directly, there are three bones in each middle ear called the Ossicles that articulate only with each other and the Hyoid bone, which is located in the neck and serves as the point of attachment for the tongue, does not articulate with any other bones in the body, being supported solely by muscles and ligaments. The Main Bones of the Human Skeleton are: The Skull - Cranium, Mandible and Maxilla; the Shoulder Girdle - Clavicle and Scapula; the Arm - Humerus, Radius and Ulna; the Hand - Carpals, Metacarpals and Phalanges; the Chest - Sternum and Ribs; the Spine - Cervical area (Top 7 Vertibrae), Thoracic (Next 12 Vertibrae), Lumbar (Bottom 5 Vertebrae), Sacrum (5 fused or stuck together bones) and Coccyx, the tiny bit at the bottom of the spine; the Pelvic girdle - Ilium, Pubis and Ischium; the Leg - Femur, Tibia and Fibula; the Ankle - Talus and Calcaneus and the Foot - Tarsals, Metatarsals and Phalanges. The biggest bone in the body is the Femur in the thigh and the smallest bone is the Stapes bone in the middle ear; several factors contribute to the bone density and average mass of the human skeleton including gender, race, hormonal factors, nutrition, physical activity and lifestyle behaviors; because of these and other factors affecting an individual's weight the human skeleton may comprise between 12 and 20 percent of a person's total body weight with the average being 15 percent. |
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How are bones formed? |
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