11 11 bones have a complex structure a layer of tough

This preview shows page 11 - 14 out of 20 pages.

1111
Bones have a complex structure. A layer of tough connective tissue called the periosteum covers a bone. Bones are made up of two types of bone tissue.Compact bone is a dense outer layer that is arranged around Haversian canals—channels through which blood vessels and nerves run.Spongy bone is a less dense layer found at the ends of long bones and in the center of flat bones, which adds strength without adding excess mass.Soft tissue called bone marrowfills cavities in some bones. Yellow marrow stores fat. Red marrow contains stem cells, which make most types of blood cells.In infants, the skeleton is almost all cartilage,which is a dense tissue built around protein fibers. Bone replaces cartilage by a process called ossification,during which cells called osteoblastssecrete minerals.Osteoblasts mature into cells called osteocytes,which maintain the minerals in bone and strengthen the bone.Mature bone contains some osteoblasts, which build new bone, and cells called osteoclasts,which breakdown bone minerals. These cells enable the repair of broken or damaged bones and keep bone from becoming brittle and weak.JointsBones meet at joints, which contain connective tissues that hold the ends together. Joints permit bones to move without damaging each other.Joints are classified into three types:Immovable, or fixed, joints allow no movement. These joints are found between bones in the skull.Slightly movable joints, such as those found between vertebrae, permit some movement.Freely movable joints, such as those found in the elbows and knees, permit movement in two or more directions.Cartilage covers the ends of the bones in a joint. Ligaments, tough strips of connective tissue, hold bones together. Synovial fluid reduces friction between moving bones. Bursae are sacs of synovial fluid that also act as shock absorbers.Joint injuries include ligament damage, inflammation, or loss of cartilage. Bursitis is inflammation of thebursae. Osteoarthritis is a painful stiffening of joints caused by the breakdown of cartilage.The Skeleton1.Complete the concept map that summarizes the parts of the human skeleton.12The Human Skeleton
3.Suggest another possible analogy for the structure and function of the skeleton.4.List five functions of the skeletal system.Bones5.The diagram shows a cross-section of bone. Label the Haversian canals, periosteum, compact bone, and spongy bone. On the lines below, describe the difference between spongy bone and compact bone.For Questions 6–12, complete each statement by writing the correct word or words6.A tough layer of connective tissue called the surrounds a bone.7.Nerves and blood vessels run through the in bones.8.Bone is soft tissue in bone cavities that (yellow) or produces blood cells (red).THINK VISUALLY1313

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture