Co 6

Skull Clavicle Sternum Humerus Ribs Vertebral column Pelvis Radius Fig. 6.1 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Skull Clavicle Sternum Humerus Ribs Vertebral column Pelvis Radius Ulna Femur Tibia Fibula

Fig. 6.4 Compact bone Spongy bone Spaces containing bone marrow and Copyright © McGraw-Hill Education. Permission required for reproduction or display. Compact bone Spongy bone Spaces containing bone marrow and blood vessels Trabeculae (a) Osteoblast Osteoclast Osteocyte Trabecula Lamellae Canaliculus (b)

Fig. 6.2 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Articular cartilage Epiphysis Epiphyseal plates in juveniles Epiphyseal lines in adults Spongy bone Compact bone Medullary cavity (contains red marrow in juveniles and yellow marrow in adults) Diaphysis Diaphysis Periosteum Endosteum Young bone (a) (b) Adult bone Osteons (haversian systems) Endosteum Inner layer Periosteum Outer layer Compact bone Central canals Spongy bone with trabeculae Connecting vessels Medullary cavity (c) Adult bone

Fig. 6.3 Osteon Lamellae on surface of bone Osteon Concentric rings Copyright © McGraw-Hill Education. Permission required for reproduction or display. Osteon Lamellae on surface of bone Osteon Concentric rings of lamellae Lamellae between osteons Central canal Periosteum Blood vessel within the periosteum Blood vessels connecting to a central canal Blood vessels within a central (Haversian) canal Canaliculi LM 400x Osteocytes in lacunae (a) Canaliculi (b) Lacunae Blood vessel connecting to a central canal between osteons a: ©Trent Stephens

Fig. 6.4 Compact bone Spongy bone Spaces containing bone marrow and Copyright © McGraw-Hill Education. Permission required for reproduction or display. Compact bone Spongy bone Spaces containing bone marrow and blood vessels Trabeculae (a) Osteoblast Osteoclast Osteocyte Trabecula Lamellae Canaliculus (b)

b: ©Biophoto Associates/Science Source Fig. 6.5 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Parietal bone Frontal bone Ossification center Ossification center Superior part of occipital bone Ethmoid bone Nasal bone Inferior part of occipital bone Maxilla Zygomatic bone Temporal bone Mandible Vertebrae Styloid process Sphenoid bone (a) Fontanel Intramembranous bones forming Cartilage Endochondral bones forming (b) b: ©Biophoto Associates/Science Source

Fig. 6.6 Uncalcified cartilage Epiphysis Perichondrium Perichondrium Copyright © McGraw-Hill Education. Permission required for reproduction or display. Uncalcified cartilage Epiphysis Perichondrium Perichondrium Calcified cartilage Periosteum Diaphysis Bone collar Cartilage Blood vessel to periosteum Epiphysis 1 A cartilage model, with the general shape of the mature bone, is produced by chondrocytes. A perichondrium surrounds most of the cartilage model. 2 The chondrocytes enlarge, and cartilage is calcified. A bone collar is produced, and the perichondrium of the diaphysis becomes the periosteum. Cartilage Perichondrium Calcified cartilage Cartilage Spongy bone Periosteum Secondary ossification center Blood vessel Bone collar Primary ossification center Space in bone Calcified cartilage Blood vessel Trabecula Spongy bone Medullary cavity Periosteum Bone collar Blood vessel Medullary cavity 3 A primary ossification center forms as blood vessels and osteoblasts invade the calcified cartilage. The osteoblasts lay down bone matrix, forming trabeculae. 4 Secondary ossification centers form in the epiphyses of long bones.

Fig. 6.2 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Articular cartilage Epiphysis Epiphyseal plates in juveniles Epiphyseal lines in adults Spongy bone Compact bone Medullary cavity (contains red marrow in juveniles and yellow marrow in adults) Diaphysis Diaphysis Periosteum Endosteum Young bone (a) (b) Adult bone Osteons (haversian systems) Endosteum Inner layer Periosteum Outer layer Compact bone Central canals Spongy bone with trabeculae Connecting vessels Medullary cavity (c) Adult bone

Fig. 6.7 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Femur Patella Epiphysis Epiphyseal plate Diaphysis (a) Length of bone increases. Epiphyseal side 1 New cartilage is produced on the epiphyseal side of the plate as the chondrocytes divide and form stacks of cells. Thickness of epiphyseal plate remains unchanged. 1 1 Chondrocytes divide and enlarge. Epiphyseal plate 2 2 Chondrocytes mature and enlarge. 2 Bone is added to diaphysis. 3 Calcified cartilage is replaced by bone. 3 Matrix is calcified, and chondrocytes die. 3 Bone of diaphysis 4 The cartilage on the diaphyseal side of the plate is replaced by bone. 4 4 LM 400x (b) (c) Diaphyseal side a: ©Ed Reschke/Photolibrary/Getty Images; c: ©Biophoto Associates/Science Source

Fig. 6.2 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Articular cartilage Epiphysis Epiphyseal plates in juveniles Epiphyseal lines in adults Spongy bone Compact bone Medullary cavity (contains red marrow in juveniles and yellow marrow in adults) Diaphysis Diaphysis Periosteum Endosteum Young bone (a) (b) Adult bone Osteons (haversian systems) Endosteum Inner layer Periosteum Outer layer Compact bone Central canals Spongy bone with trabeculae Connecting vessels Medullary cavity (c) Adult bone

Fig. 6.9 Decreased blood Ca2+ Increased blood Ca2+ 1 5 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Decreased blood Ca2+ Increased blood Ca2+ 1 5 Posterior aspect of thyroid gland Parathyroid glands 1 Decreased blood Ca2+ stimulates PTH secretion from parathyroid glands. Kidney Thyroid gland 2 PTH stimulates osteoclasts to break down bone and release Ca2+ into the blood. 3 In the kidneys, PTH increases Ca2+ reabsorption from the urine. PTH also stimulates active vitamin D formation. 3 PTH Calcitonin 4 Vitamin D promotes Ca2+ absorption from the small intestine into the blood. 2 6 Stimulates osteoclasts Inhibits osteoclasts 5 Increased blood Ca2+ stimulates calcitonin secretion from the thyroid gland. Vitamin D 6 Calcitonin inhibits osteoclasts, which allows for enhanced osteoblast uptake of Ca2+ from the blood to deposit into bone. Bone Osteoclasts promote Ca2+ uptake from bone. Ca2+ 4 Osteoblasts promote Ca2+ deposition in bone. Small intestine Ca2+ Blood

Fig. 6.8 Compact bone Medullary cavity Woven bone External callus: Copyright © McGraw-Hill Education. Permission required for reproduction or display. Compact bone Medullary cavity Woven bone External callus: Periosteum Woven bone Dead bone Hematoma Cartilage Broken humerus Internal callus: Compact bone at break site Dead bone Fibers and cartilage Woven bone Hematoma formation Callus formation Callus ossification Bone remodeling 1 Blood released from damaged blood vessels forms a hematoma. 2 The internal callus forms between the ends of the bones, and the external callus forms a collar around the break. 3 Woven, spongy bone replaces the internal and external calluses. 4 Compact bone replaces woven bone, and part of the internal callus is removed, restoring the medullary cavity. Callus around broken humerus (at arrow) (a) (b) a: ©Andrew F. Russo

Osteoporosis Symptoms Page 145 MUSCULAR INTEGUMENTARY NERVOUS Copyright © McGraw-Hill Education. Permission required for reproduction or display. MUSCULAR Muscle atrophy from reduced activity. Increased chance of falling and breaking a bone. INTEGUMENTARY Limited sun exposure lowers vitamin D production, which reduces Ca2+ absorption. NERVOUS Pain from injury may reduce activity level and therefore further injuries. Osteoporosis Symptoms Pain and stiffness especially in spine Easily broken bones Loss of height Treatment Dietary calcium and vitamin D Exercise Calcitonin Alendronate REPRODUCTIVE Decreased estrogen following menopause contributes to osteoporosis. ENDOCRINE Calcitonin is used to treat osteoporosis. CARDIOVASCULAR If bone breakage has occurred, increased blood flow to that site removes debris. Blood carries nutrients necessary for repair. DIGESTIVE Inadequate calcium and vitamin D intake can cause insufficient Ca2+ absorption in small intestine. RESPIRATORY Excessive smoking lowers estrogen levels, which increases bone loss. LYMPHATIC AND IMMUNE Immune cells help prevent infection after surgery, such as hip replacement.