A&P Chapter 6 Flashcards
Functions of the Skeletal System
Support - Weight bearing Protection - Encases organs Movement - Muscle attachment Storage - Minerals
Cartilage (3 types)
Hyaline Cartilage associated with bones - Development, lengthening, and repair. Specialized cells - Chondroblasts - Chondrocytes
2 types of cartilage growth
Apositional
- Chondroblasts in perichondrium add matrix to outside of existing cartilage.
Interstitial
- Chondrocytes within tissue divide and matrix between existing cells.
Bone Matrix
- 35% organic material
- 65 inorganic material
- collagen gives flexibility
- loss of collagen causes brittle bones
- minerals give strength
- loss of minerals causes “bendy” bones
Bone Histology
Bone cells - osteoblasts, osteocytes, osteoclasts Woven bone: collagen fibers randomly oriented Lamellar bone: mature bone in sheets Spongy: trabeculae Compact bone: dense
Origin of bone cells
Mesenchymal cells give rise to osteochindral progenitor cells Osteochondral progenitors cells -Innner perichondrium & periosteum -Give rise to osteoblasts Osteoblasts -Develop into osteocytes
Bone Cells
Osteoblasts
- Formation of bone through ossification or osteogenesis. Collagen produced by E.R. and golgi. Released by exocytosis. Precursors of hydroxyapetite stored in vesicles, then released by exocytosis.
- Ossification: formation of bone by osteoblasts. Osteoblasts communicate through gap junctions. Cells surround themselves by matrix.
Bone Cells
Osteocytes. Mature bone cells. Surrounded by matrix, but can make small amounts of matrix to maintain it.
- Lacunae: spaces occupied by osteocyte cell body
- Canaliculi: canals occupied by osteocyte cell processes
- Nutrients diffuse through tiny amount of liquid surrounding cell and filling lacunae and canaliculi. Then can transfer nutrients from one cell to the next through gap junctions.
Bone Cells
Osteoclasts. Resorption of bone
- Ruffled border: where cell membrane borders bone and resorption is taking place.
- H ions pumped across membrane, acid forms, eats away bone.
- Release enzymes that digest the bone.
- Derived from monocytes (which are formed from stem cells in red bone marrow)
- Multinucleated and probably arise from fusion of a number of cells
Woven and Lamellar Bone
Woven bone
- Collagen fibers randomly oriented
- Formed during embryonic development and fracture repair
- Replaced with lamellar bone over time
Lamellar bone
- Mature bone with organized collagen fibers
- Arranged in thin sheets called lamellae
Spongy Bone
- Contains interconnected plates called trabeculae
- Bone marrow and blood vessels fill spaces between trabeculae
- Trabeculae are oriented along lines of stress
- Trabeculae can rearrange if stress changes
Compact Bone
- Denser than spongy bone
- Central canal contain blood vessel
- Concentric lamella surround central canal
- Osteon is central canal, lamella, & osteocytes
- Circumferential lamella form outer surface
- Blood vessels enter bone by perforating canals
Shape of Bones
Long bones - Upper and lower limb Short bones - Ankle and wrist Flat bones - Skull, ribs, sternum, shoulder blades Irregular bones - Vertebrae and facial bones
Structure of Long Bones
Diaphysis - Long axis or shaft of bone Articular cartilage - Covers the end of long bones Epiphysis - End of bones Epiphyseal plate - Separates epiphysis from diaphysis
Structures of Bone
Medullary cavity - Internal cavities filled with marrow Periosteum - Covers outside of bone has blood - Outer layer of vascularized connective tissue -Fibers of tendons become continuous with fibers of periosteum. Endosteum - Covers internal space of bone