Chapter 6 Flashcards
Functions of Skeletal System
- Support
- Protection
- Movement
- Storage
- Hematopoiesis
Support of Skeletal System
-Provides a framework for the body
Protection from Skeletal System
-Protects internal organs
Movement of Skeletal System
-Skeletal muscles attach to bones to move body parts
Storage of Skeletal System
Stores:
- Calcium (98%)
- Fat (Triglycerides)
Hematopoiesis
-Production of blood cells (RBCs and WBCs) by hematopoietic stem cells (hematocytoblasts)
Characterization of bone shape
- Long bone (Humerus)
- Short bone (Triquetral)
- Flat bone (Sternum)
- Irregular bone (Vertebra)
Composition of Bone Matrix
-67% hydroxyapatites
Calcium Phosphate
Calcium Carbonate
-33% Collagen
Hydroxyapatites
- Mineral Salts
- Inorganic
- Resist Compression
Collagen
- Organic
- Resist tension
Osteogenesis Imprefecta
-Caused by mutation in gene for Type I collagen
What cells make up bone?
- Osteogenic cells —>
- Osteoblast —>
- Osteoclast —>
- Osteocytes
Osteogenic Cell
- Mitotically active
- Stem cells
Osteoblast
- Bone forming cells
- Secrete bone matrix
- Collagen and Osteoid
Osteoid
- Immature bone matrix
- Glue that will hold calcium crystals and collagen fibers
Osteoclast
- Giant multinucleate cells derived from stem cells in bone marrow
- Degrade bone matrix
- Ruffled border
- Increases surface area for degrading bone matrix
How do osteoclasts degrade bone matrix?
- HCl degrades hydroxyapatites
- Lysosomal enzymes degrade collagen
Osteocytes
- Reside in lacuna
- Monitor their environment
- Maintain bone matrix by regulating osteoblasts and osteoclasts
Structure of bone
- Spongy bone
- Compact bone
- Articular cartilage
Trabeculae
-Network of supporting “beams” present in spongy bone
Long Bone Anatomy
- Diaphysis
- Epiphysis
- Periosteum
- Endosteum
Diaphysis
-Shaft
-Compact bone-dense
-Medullary cavity
Yellow marrow-adipose
Red Marrow-hematopoiesis
Epiphysis
- Ends of bone
- Compact bone-outer layer
- Spongy bone-porous
- Epiphyseal line
- Articular cartilage
Epiphyseal line
-Former growth plate
Articular Cartilage
- Cartilage at ends of bones
- Made of hyaline
- No nerves
- Smooth
- Enables bones to glide
Periosteum
-Fibrous tissue coating outer surface of bones
Outer Layer Composition of Periosteum
- Dense Irregular tissue
- Surface for muscle attachment
- Vascular
Inner Layer Composition of Periosteum
-Contains osteogenic cells
Sharpey’s fibers
- Collagen fibers
- Attach periosteum to bone
Endosteum
- Lines medullary cavity
- Contains Osteogenic cells
Types of Bone Marrow
- Yellow Bone Marrow
- Red Bone Marrow
Yellow Bone Marrow
-Fat Storage
Red Bone Marrow
-Site of production for blood cells
-Contains hematopoietic stem cells
-These cells have the potential to differentiate into:
WBCs
RBCs
Platelets
Hematopoiesis
-The process by which hematopoietic stem cells self-renew and differentiate to form RBCs, WBCs, and platelets
Where is hematopoietic tissue located in newborns?
-Medullary cavity of long bones and all areas of spongy bone that contains red marrow
Where is hematopoeitic tissue located in adults?
-Most red marrow is replaced with yellow marrow except in:
head of femur
head of humerus
Diploe of flat bones (Sternum, coxal bones)
Osteons
-Unit of compact bone
-Contains:
Central Canal
Lamella
Lacuna
Central Canal of Osteons
- Blood Vessels
- Nerve fibers
Lamella of Osteons
-Rings around central canal
Lacuna
-Where the osteocytes sit
How is bone made?
- Intramembranous Ossification
- Endochondrial Ossification
Intramembranous Ossification
- Differentiation of bone from mesenchymal stem cells found in fibrous connective tissue
- Process by which cranial bones and clavicles are formed
- Begins at 8 weeks of development-fibrous connective tissue starts to ossify
Endochondrial Ossification
-Process by which cartilage is turned into bone
Intramembranous ossification step 1
- Mesenchymal cells differentiate into osteoblasts
- Osteoblasts start laying down matrix (collagen, osteoid) to form ossification centers
Intramembranous Ossification step 2
- Osteoids calcify forming the bone matrix
- Trapped osteoblasts turn into osteocytes
Intramembranous Ossification step 3
- Trabeculae and periosteum form
- Osteoid is laid down between embryonic blood vessels forming trabeculae
- Vasculized mesenchyme condenses and becomes the periosteum
Intramembranous Ossification step 4
- Trabeculae deep to periosteum are replaced by compact bone-forming compact bone plates
- Spongey bone (diploe) persists inside
