Chapter 6 Flashcards
Six main functions of skeletal system
Support
Protection
Assistance in movement
Mineral homeostasis (storage/release)
Blood cell production
Tryglyceride storage
Explain how bones control mineral homeostasis
Bone stores minerals, especially calcium and phosphorus and release on demand into blood
What Percentage of body mass is bone? What percentage of calcium is stored in bone
18
99
Explain blood cell production in bones
Red bone marrow produces RBC WBC and platelets: called hemopoises
Red bone marrow is made of what? Where is it found
Consists of blood cells Adipocytes fibroblasts macrophages in network of reticular fibers
Found in bones of fetus/ some adult (hip,ribs,sternum,vertebrae,skull, ends of humerus/femur)
Explain tryglyceride storage in bones
Yellow bone marrow consists of mainly adipose cells=potential energy reserve
Diaphysis
Bone shaft
Epiphyses
Proximal/distal end
Metaphyses
Between diaphyses/epiphyses
Contains epiphyseal plate=hyaline cartilage allowing diaphyses to grow
Epiphyseal line: at 14-24 replaces plate with bone
Articular cartilage
Thin layer hyaline cartilage covering epiphyseal at joint, no perichondrium/BV=limited repair
Periosteum/layers
Thought connective tissue sheath/blood supply surrounds bone not covered by articular cartilage
Outer fibrous layer: dense irregular connective tissue
Inner osteogenic layer: cells
Protects repairs nourish attachment point (ligaments/tendons)
Perforating fibers
Thick bundles of collagen attatching periosteum to bone
Medullary cavity (marrow cavity)
Hollow space in diaphyses containing YBM/BV, minimizes weight of bone
Endostuem
Thin membrane lines medullary cavity, has bone forming cells/connective tissue
Other name for bone
Osseous tissue
ECM of bone
15% water
30% collagen fibers
55% crystallized minerals salts
Hydroxyapatite
Calcium phosphate and calcium hydroxide
Calcification
Mineral salts crystallized=tissue hardens
Requires collagen fibers
What helps bone hardness/flexibility
Crystallized inorganic mineral salts=hardness
Collagen fibers=flexibility
Cells in bone tissue
Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
Osteoprogenitor cells
Unspecialized bone stem cells become osteoblasts
Found along Inner portion of periosteum, in endosteum, in canal in bone containing BV
Osteoblasts
Bone building cells, synthesize/secrete collagen fibers, ECM, initiate calcification
When trapped in their secretions (ECM) become osteocytes
Osteocytes
Mature/main bone cells, maintains bones daily metabolism
Osteoclasts
Huge cells from fusion of 50 monocytes (WBC)
Ruffled border releases lysosomal enzymes, breakdown ECM=bone resorption
Compact bone tissue
Few spaces=strongest
Found beneath periosteum of all bones/most diaphyses of long bones
Osteons (Haversian) systems
Repeating concentric lamellae arranges around osteonic (Haversian/central) canal
Concentric lamellae
Circular plates of mineralized ECM in increasing diameter (tree rings)
Lacunae
Spaces between concentric lamellae
Canaliculi
Radiate from lacunae
Filled with ECM, system of interconnected canals in bone for O2s/nutrients/wastes
How are osteons arranged in compact vs spongy
Aligned in same direction and are parallel to the length of diaphyses
No osteons
Interstitial lamellae
Area between neighbouring osteons
Have lacunae with osteocytes/Canaliculi
Interosteonic canals
BV/nerves form periosteum penetrate the compact bone thought these these transversely
Connect with medullary cavity periosteum central canals
Circumferential lamellae
Around entire outer/inner circumference of shaft of long bone
External:under periosteum connected by perforating fibers
Internal: lines medullary cavity
Spongy bone tissue
Always interior covered by compact bone for protection
Spongy=light=easier to move
Trabeculae
Spongy
Irregularly patterned lamellae
Consists of concentric lanellae, osteocytes that lie in lacunae, Canaliculi radiate outward from lacunae
Support RBM and protect
Periosteal arteries
Small arteries with nerves enter diaphysis through interosteonic canal to supply periosteum/outer compact bone
Nutrient artery
Passed through a hole in the compact bone called nutrient foramen
Supplies inner compact bone/spongy bone/RBM as far as epiphyseal plates/lines
Nutrient veins
One of two a company nutrient artery, exit through diaphyses
Epiphyseal veins/metaphyseal veins
Numerous acoompany respective arteries/exit areas
Periosteal veins
Many accompany respective arteries be exit periosteum
Nerves into bone
Accompany BV that supplies bones periosteum is rich with nerves
Ossification
Process by which a bone forms
Initial bone formation in an embryo/fetus (don’t think this is right but two kinds)
Intramembraneous ossification: forms within Mesenchyme, simpler
Endochondral ossification: replacement of cartilage by bone
Intramembraneous ossification steps
1) Development of ossification center:
Chemical message cause Mesenchyme to cluster(center) and differentiate into Osteoprogenitor cells then osteoblasts
2) calcification: secretion of ECM stops, osteocytes lie in lacunae extend cytoplasmic processes into Canaliculi
Calcium/mineral salts deposit into ECM=hardens/calcified
3) formation of trabeculae: ECM develops into trabeculae=forms spongy around BV
Connective tissue in trabeculae differentiates into RBM
4) development of the periosteum: Mesenchyme condenses=periosteum
Thin layer replaced surface layers of spongy bone
Endochondral ossification steps simple
Development of cartilage model
Growth of cartilage model
Development of the primary ossification center
Development of the medullary (marrow) cavity
Development of secondary ossification center
Formation of articular cartilage and the epiphyseal (growth) plate
Development of cartilage model
Mesenchyme crowds into shape of bone, develop into chondoblasts, perichondrium develops
Growth of cartilage model
division of chondrocytes=growth
Interstitial/endogenous growth: length chondrocytes dividing/secretion ECM
Appositional/exogenous growth: thickness, deposition of ECM on surface form perichondrium
Development of primary ossification center
Nutrient artery penetrates, perichondrium forms bone=perisoteum, capillaries induce growth of primary ossification center (bone tissue replaces cartilage)
Development of medullary canal
Bone breakdown by osteoclasts =canal
Development of secondary ossification center
Secondary ossification centres In epiphyses
Formation of articular cartilage formation
Consist of hyaline cartilage
Growth in length
Interstitial forth of cartilage on epiphyseal side of epiphyseal plate
Replacement of cartilage with bone by Endochondral ossification of diaphysial side
Four zones of epiphyseal plate/growth in length
1) zone of resting cartilage: consist of small scattered chondrocytes, anchor epiphyseal plate to epiphyses
2) zone of proliferation cartilage: larger chondrocytes arranged like coins, interstitial growth/secrete ECM replace diaphyses side
3) zone of hypertonic cartilage: even larger chondrocytes arranged in columns
4) since of calcified cartilage, few chondrocytes dead as ECM calcified, osteoclasts/osteoblasts use Endochondral ossification=new diaphyses
Growth in thickness
1) periosteal cells differentiate into osteoblasts, surrounded by ECM=osteocytes, forms bone ridges
2) ridges fold/fuse, groove becomes tunnel that encloses BV, periosteum=endosteum
3)osteoblast in endosteum deposit bone ECM=forming new concentric lamellae
4) osteoblasts under periosteum deposit circumferential lamellae=thicnkess
Bone remodelling
Bone reposition: removal of mineral/collagen fibers by osteoclasts (destroy ECM)
Bone deposition: addition of mineral/collagen fibers by osteoblast (add ECM)
Factors affecting bone growth/remodelling
1) minerals: large # Ca/P, small Mg/Fl/Mn
2) vitamins: a,c,d,b12
3) hormones: insulin like growth factors(IGFs), thyroid hormones, insulin, sex hormones
4) exercise
5) aging: Less sex hormone
How does vitamin A affect bone growth
Stimulates osteoblast
How does vitamin C affect bone growth
Synthesis of collagen
How does vitamin D affect bone growth
Increase absorption of Ca=bone growth
How does vitamin K/B12 affect bone growth
Synthesis of bone proteins
How does insulin like growth hormones affect bone growth
Produced by liver/bone tissue, stimulate osteoblasts, promote cell division at epiphyseal plate/periosteum, enhance syntheses of protein
How does thyroid hormones affect bone growth
T3/t4 stimulate osteoblasts
How does insulin affect bone growth
Increase synthesis of bone proteins
How do sex hormones affect bone growth
Increase osteoblasts activity, synthesis of bone ECM, growth spurt, shut down growth at epiphyseal plate slow resorption
Parathyroid hormone
PTH
Increases blood ca2+ level, decrease loss in urine, stimulates formation of calcitriol
Calcitonin
CT
Inhibits acidic of osteoclasts, speeds blood Ca2+ uptake by bone/accelerates deposition
(Promotes bone formation/lowers blood Ca2+)
