Bones & Skeletal Tissue Ch 6

Function of the Skeletal System Support Protection Movement Mineral storage Blood cell formation (hemopoiesis) Triglyceride storage

Bones & Cartilage

Anatomy of a Long Bone spongy bone Proximal compact bone epiphysis Endosteum diaphysis epiphyseal line yellow marrow Sharpey’s fibers Distal epiphysis periosteum hyaline cartilage

Anatomy of a Bone Haversian system spongy bone periosteum Lamellae osteocyte Haversian system Lamellae spongy bone periosteum

Haversian System in Compact Bone osteocytes in lacunae central canal

Haversian System in Compact Bone osteocytes in lacunae

Intramembranous Ossification Cranial bones Mandible Clavicles frontal, parietal, occipital, and temporal bones)

Intramembranous Ossification

Fetal Skeleton 275 bones 16 weeks fetus

Fig. 06.13

bone calcified cartilage epiphyseal line epiphyseal plate Fetus: 1st 2 months Endochondral Ossification 1o ossification center 2o ossification center bone Hyaline cartilage calcified cartilage Just before birth Bone growth stops around age 21 for males and 18 for females when the epiphysis & diaphysis fuse (epiphyseal plate closure) epiphyseal line epiphyseal plate Childhood Adult

Epiphyseal Plate

During puberty- sex hormones: estrogen and testosterone Hormonal Regulation of Bone Growth GH from anterior pituitary, which is regulated by T3 and T4 of the thyroid During puberty- sex hormones: estrogen and testosterone

Hormones TSH GH TSH T3 T4

Hormones Ovary Testes Estrogen Testosterone

Hypersecretion of GH- gigantism Sultan Kosen (R) 8 ft 1 in Hyposecretion of GH- dwarfism He Pingping 2 ft 5.37 in

Maintains homeostasis Bone Homeostasis: Remodel & Repair Parathyroid hormone- stimulates osteoclasts Calcitonin- inhibits osteoclasts Maintains homeostasis

Bone Homeostasis: Remodel & Repair

Bone cells that aid in remodeling Osteoblast Builds new bone Osteocyte Mature bone cell Osteoclast Eats bone OsteoblastsOsteoblasts are responsible for building new bone and lie at the centre of bone physiology. Their functions include the synthesis of collagen and the control of mineralisation. OsteoclastsOsteoclasts are specialised cells that resorb bone. They work by sealing off an area of bone surface then, when activated, they pump out hydrogen ions to produce a very acid environment, which dissolves the hydroxyapatite. OsteocytesBone adapts to applied forces by growing stronger in order to withstand them; it is known that exercise can help to improve bone strength. Osteocytes are thought to be part of the cellular feed-back mechanism which directs bone to form in the places where it is most needed. They lie within mineralised bone and it is thought that they may detect mechanical deformation and mediate the response of the osteoblasts.

Repair of Fractures hematoma callus bony callus bone remodeling

Common Types of Fractures Usually treated by realignment Simple- closed fracture (8-12 wks to heal) bone breaks cleanly; no penetration Compound- bone penetrates through skin Comminuted- bone fragments into many pieces; aged or brittle bones Compression- bone is crushed Depressed- broken bone portion is depressed inward Impacted- broken bone ends are forced into each other Spiral- excessive twisting of bone Greenstick- bone breaks incompletely

Common Types of Fractures Oblique Comminuted Spiral Compound

Bone Repair Electrical stimulation of the fracture site: Increases speed and completeness of healing The e- stimulation inhibits PTH and slow osteoclasts down from reabsorbing bone 2. Ultrasound treatment: Daily treatments reduce healing time of broken bones by 25-35% 3. Free vascular fibular graft technique: Transplant fibula in arm Gives good blood supply not available in other treatments 4. Bone substitutes: Crushed bone from cadaver- but risk of HIV and hepatitis Sea bone- coral Artificial bone- ceramic

Diseases of the Skeletal System Osteoporosis- bone reabsorption outpaces bone deposit; bones become lighter and fracture easier Factors: age, gender (more in women) estrogen and testosterone decrease insufficient exercise (or too much) diet poor in Ca++ and protein abnormal vitamin D receptors smoking

Osteoporosis 29 40 84 92

Osteoporosis

Diseases of the Skeletal System Rickets- vitamin D deficiency Osteomalacia- soft bones, inadequate mineralization in bones, lack of vitamin D

Diseases of the Skeletal System Rheumatoid arthritis- autoimmune reaction

What does the secondary site of ossification produce? INQUIRY What does the secondary site of ossification produce? What is an epiphyseal line? Provide an example of a flat bone? How does PTH effect bone development? How many bones in the adult skeleton? What does an osteoblast do and where are they primarily found?