Ch 5 Skeletal System

7-2 Bone Tissue Connective tissue with a matrix hardened by minerals (calcium phosphate) Continually remodels itself Functions of the skeletal system –support, –protection, –movement, –mineral storage, –blood formation (hematopoiesis)

7-3 Long bones – levers acted upon by muscles Short bones – glide across one another in multiple directions Flat bones – protect soft organs Shapes of Bones

Types of bone tissue Compact – dense, made of osteons Spongy – porous, made of irregular, needle like trabeculae 7-4

7-5 Structure of a Long Bone Shaft (diaphysis) Enlarged ends (epiphyses) Epiphyseal plate (growth plate > line) Compact and spongy bone Marrow cavity Articular cartilage Periosteum Endosteum

7-6 Structure of a Flat Bone External and internal surfaces composed of compact bone Middle layer is spongy bone and bone marrow

Compact Bone Osteon = basic structural unit –cylinders formed from layers (lamellae) of matrix around central canal (Haversion canal) –osteocytes in lacunae connected to each other and their blood supply by tiny cell processes in canaliculi

7-8

Blood Vessels of Bone Perforating canals or Volkmann canals - perpendicularly join central canals

7-10 Bone Cells Osteoblasts form organic matter of matrix Osteocytes are osteoblasts trapped in the matrix they formed –cells in lacunae connected by gap junctions inside canaliculi

7-11 Bone Cells Osteoclasts develop in bone marrow by fusion of 3-50 stem cells Reside in pits that they ate into the bone Resorb (break down) bone matrix

Matrix of Bone Tissue Dry weight = 1/3 organic & 2/3 inorganic matter –Organic matter Collagen and glycoproteins –Inorganic matter 85% hydroxyapatite Ca 10 (PO 4 ) 6 (OH) 2 10% calcium carbonate CaCO 3 other minerals (fluoride, potassium, magnesium) Combination provides strength and resilience

Spongy Bone Spongelike appearance formed by plates of bone called trabeculae –spaces filled with red bone marrow Trabeculae have few osteons or central canals –no osteocyte is far from blood of bone marrow Provides strength with little weight –trabeculae develop along bone’s lines of stress

7-14 Spongy Bone Structure and Stress

7-15 Bone Marrow In medullary cavity (long bone) and among trabeculae (spongy bone) Red marrow like thick blood –reticular fibers and immature cells –Hemopoietic (produces blood cells) –in vertebrae, ribs, sternum, pelvic girdle and proximal heads of femur and humerus in adults Yellow marrow –fatty marrow of long bones in adults

Bone marrow transplant