6/5/2014
1
 Functions of Bone and Skeletal System
 Structure of Bone
 Histology of BoneTissue
 Blood and Nerve Supply ...
6/5/2014
2
 Diaphysis
 Epiphyses
 Metaphyses
▪ Epiphyseal growth plate
 Articular cartilage
 Periosteum
▪ Perforating...
6/5/2014
3
 Four types of cells are present in bone tissue
 Osteogenic cells
 Undergo cell division; the resulting cell...
6/5/2014
4
 Bone is richly supplied with
blood
 Periosteal arteries
accompanied by nerves
supply the periosteum and
comp...
6/5/2014
5
 Formation of Bone in an Embryo
 Bone formation follows one of two patterns
▪ Intramembranous ossification
▪ ...
6/5/2014
6
 Growth in Length
 The growth in length of long
bones involves two major events:
 1) Growth of cartilage on ...
6/5/2014
7
 A balance must exist between the actions of
osteoclasts and osteoblasts
 If too much new tissue is formed, t...
6/5/2014
8
 Hormones
 Estrogen and testosterone cause a dramatic
effect on bone growth
▪ Cause of the sudden “growth spu...
6/5/2014
9
Compact bone
Spongy bone
Periosteum
Fracture hematoma
Fracture
hematoma
Bone
fragment
Osteocyte
Red blood
cell
...
6/5/2014
10
 Bone is the body’s major calcium reservoir
 Levels of calcium in the blood are maintained by
controlling th...
6/5/2014
11
 Bone tissue alters its strength in response to
changes in mechanical stress
 Under stress, bone tissue beco...
6/5/2014
12
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Bio 201 chapter 6 lecture

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Bio 201 chapter 6 lecture

  1. 1. 6/5/2014 1  Functions of Bone and Skeletal System  Structure of Bone  Histology of BoneTissue  Blood and Nerve Supply of Bone  Bone Formation  Bone’s Role in Calcium Homeostasis  Exercise and BoneTissue  Aging and BoneTissue  Support  Protection  Assistance in Movement  Mineral Homeostasis  Blood Cell Production  Triglyceride Storage
  2. 2. 6/5/2014 2  Diaphysis  Epiphyses  Metaphyses ▪ Epiphyseal growth plate  Articular cartilage  Periosteum ▪ Perforating fibers  Medullary cavity  Endosteum  Long Bone Anatomy (Humerus)  Extracellular matrix surrounding widely separated cells  Matrix ▪ 25% water ▪ 25% collagen fibers ▪ 50% crystallized mineral salts  The most abundant mineral salt is calcium phosphate  A process called calcification is initiated by bone-building cells called osteoblasts  Mineral salts are deposited and crystalize in the framework formed by the collagen fibers of the extracellular matrix  Bone’s flexibility depends on collagen fibers
  3. 3. 6/5/2014 3  Four types of cells are present in bone tissue  Osteogenic cells  Undergo cell division; the resulting cells develop into osteoblasts  Osteoblasts  Bone-building cells  Synthesize extracellular matrix of bone tissue  Osteocytes  Mature bone cells  Exchange nutrients and wastes with the blood  Osteoclasts  Release enzymes that digest the mineral components of bone matrix (resorption)  Regulate blood calcium level
  4. 4. 6/5/2014 4  Bone is richly supplied with blood  Periosteal arteries accompanied by nerves supply the periosteum and compact bone  Epiphyseal veins carry blood away from long bones  Nerves accompany the blood vessels that supply bones  The periosteum is rich in sensory nerves sensitive to tearing or tension  The process by which bone forms is called ossification  Bone formation occurs in four situations:  1) Formation of bone in an embryo  2) Growth of bones until adulthood  3) Remodeling of bone  4) Repair of fractures
  5. 5. 6/5/2014 5  Formation of Bone in an Embryo  Bone formation follows one of two patterns ▪ Intramembranous ossification ▪ Flat bones of the skull and mandible are formed in this way ▪ “Soft spots” that help the fetal skull pass through the birth canal later become ossified forming the skull ▪ Endochondral ossification ▪ The replacement of cartilage by bone ▪ Most bones of the body are formed in this way including long bones 1 Blood capillary Ossification center Mesenchymal cell Osteoblast Collagen fiber Development of ossification center Mandible Flat bone of skull 1 Blood capillary Ossification center Mesenchymal cell Osteoblast Osteocyte in lacuna Canaliculus Osteoblast Newly calcified bone matrix Development of ossification center Calcification Mandible Flat bone of skull 2 Collagen fiber 1 Blood capillary Ossification center Mesenchymal cell Osteoblast Development of ossification center Calcification Mandible Flat bone of skull 2 Collagen fiber Osteocyte in lacuna Canaliculus Osteoblast Newly calcified bone matrix Mesenchyme condenses Blood vessel Spongy bone trabeculae Osteoblast Formation of trabeculae3 1 Blood capillary Ossification center Mesenchymal cell Osteoblast Mesenchyme condenses Blood vessel Spongy bone trabeculae Osteoblast Periosteum Spongy bone tissue Compact bone tissue Development of ossification center Calcification Formation of trabeculae Development of the periosteum Mandible Flat bone of skull 3 4 2 Collagen fiber Osteocyte in lacuna Canaliculus Osteoblast Newly calcified bone matrix 1 Development of cartilage model Hyaline cartilage Perichondrium Proximal epiphysis Distal epiphysis Diaphysis 1 Development of cartilage model Growth of cartilage model 2 Hyaline cartilage Uncalcified matrix Calcified matrix Perichondrium Proximal epiphysis Distal epiphysis Diaphysis 1 Development of cartilage model Development of primary ossification center Growth of cartilage model 2 3 Hyaline cartilage Uncalcified matrix Calcified matrix Nutrient artery Perichondrium Proximal epiphysis Distal epiphysis Diaphysis Periosteum Primary ossification center Spongy bone 1 Hyaline cartilage Calcified matrix Periosteum (covering compact bone) Uncalcified matrix Calcified matrix Medullary cavity Nutrient artery and vein Nutrient artery Perichondrium Proximal epiphysis Distal epiphysis Diaphysis Development of cartilage model Development of primary ossification center Development of the medullary cavity Growth of cartilage model Periosteum Primary ossification center 2 3 4 Spongy bone Uncalcified matrix 1 Development of cartilage model Development of primary ossification center Development of the medullary cavity Growth of cartilage model 2 3 4 Hyaline cartilage Calcified matrix Periosteum (covering compact bone) Uncalcified matrix Calcified matrix Medullary cavity Nutrient artery and vein Nutrient artery Perichondrium Proximal epiphysis Distal epiphysis Diaphysis Periosteum Primary ossification center Secondary ossification center Nutrient artery and vein Uncalcified matrix Epiphyseal artery and vein Development of secondary ossification center 5 Spongy bone Uncalcified matrix 1 Articular cartilage Spongy bone Epiphyseal plate Secondary ossification center Nutrient artery and vein Uncalcified matrix Epiphyseal artery and vein Formation of articular cartilage and epiphyseal plate Development of secondary ossification center Development of cartilage model Development of primary ossification center Development of the medullary cavity Growth of cartilage model 2 3 4 5 6 Hyaline cartilage Uncalcified matrix Calcified matrix Periosteum (covering compact bone) Uncalcified matrix Calcified matrix Medullary cavity Nutrient artery and vein Nutrient artery Perichondrium Proximal epiphysis Distal epiphysis Diaphysis Periosteum Primary ossification center Spongy bone
  6. 6. 6/5/2014 6  Growth in Length  The growth in length of long bones involves two major events:  1) Growth of cartilage on the epiphyseal plate  2) Replacement of cartilage by bone tissue in the epiphyseal plate  Osteoclasts dissolve the calcified cartilage, and osteoblasts invade the area laying down bone matrix  The activity of the epiphyseal plate is the way bone can increase in length  At adulthood, the epiphyseal plates close and bone replaces all the cartilage leaving a bony structure called the epiphyseal line  Growth in Thickness  Bones grow in thickness at the outer surface  Remodeling of Bone  Bone forms before birth and continually renews itself  The ongoing replacement of old bone tissue by new bone tissue  Old bone is continually destroyed and new bone is formed in its place throughout an individual’s life
  7. 7. 6/5/2014 7  A balance must exist between the actions of osteoclasts and osteoblasts  If too much new tissue is formed, the bones become abnormally thick and heavy  Excessive loss of calcium weakens the bones, as occurs in osteoporosis  Or they may become too flexible, as in rickets and osteomalacia  Normal bone metabolism depends on several factors  Minerals  Large amounts of calcium and phosphorus and smaller amounts of magnesium, fluoride, and manganese are required for bone growth and remodeling  Vitamins  Vitamin A stimulates activity of osteoblasts  Vitamin C is needed for synthesis of collagen  Vitamin D helps build bone by increasing the absorption of calcium from foods in the gastrointestinal tract into the blood  Vitamins K and B12 are also needed for synthesis of bone proteins  Hormones  During childhood, the hormones most important to bone growth are growth factors (IGFs), produced by the liver ▪ IGFs stimulate osteoblasts, promote cell division at the epiphyseal plate, and enhance protein synthesis  Thyroid hormones also promote bone growth by stimulating osteoblasts  Insulin promotes bone growth by increasing the synthesis of bone proteins
  8. 8. 6/5/2014 8  Hormones  Estrogen and testosterone cause a dramatic effect on bone growth ▪ Cause of the sudden “growth spurt” that occurs during the teenage year ▪ Promote changes in females, such as widening of the pelvis ▪ Shut down growth at epiphyseal plates  Parathyroid hormone, calcitriol, and calcitonin are other hormones that can affect bone remodeling  Fracture Types  Open (compound) fracture ▪ The broken ends of the bone protrude through the skin  Closed (simple) fracture ▪ Does not break the skin  Comminuted fracture ▪ The bone is splintered, crushed, or broken into pieces  Greenstick fracture ▪ A partial fracture in which one side of the bone is broken and the other side bends  Impacted fracture ▪ One end of the fractured bone is forcefully driven into another  Pott’s fracture ▪ Fracture of the fibula, with injury of the tibial articulation  Colles’ fracture ▪ A fracture of the radius in which the distal fragment is displaced  Stress fracture ▪ A series of microscopic fissures in bone
  9. 9. 6/5/2014 9 Compact bone Spongy bone Periosteum Fracture hematoma Fracture hematoma Bone fragment Osteocyte Red blood cell Blood vessel Formation of fracture hematoma Phagocyte Osteon 1 Phagocyte Osteoblast Fibroblast Fibrocartilaginous callus Collagen fiber Chondroblast Cartilage Fibrocartilaginous callus formation2 Compact bone Spongy bone Periosteum Fracture hematoma Fracture hematoma Bone fragment Osteocyte Red blood cell Blood vessel Formation of fracture hematoma Phagocyte Osteon 1 Bony callus Spongy bone Osteoblast Bony callus formation Osteocyte 3 Compact bone Spongy bone Periosteum Fracture hematoma Fracture hematoma Bone fragment Osteocyte Red blood cell Blood vessel Formation of fracture hematoma Phagocyte Osteon 1 Phagocyte Osteoblast Fibroblast Fibrocartilaginous callus Collagen fiber Chondroblast Cartilage Fibrocartilaginous callus formation2 Spongy bone Osteoblast Osteoclast New compact bone Bony callus formation Bone remodeling Osteocyte 3 4 Compact bone Spongy bone Periosteum Fracture hematoma Fracture hematoma Bone fragment Osteocyte Red blood cell Blood vessel Formation of fracture hematoma Phagocyte Osteon 1 Phagocyte Osteoblast Fibroblast Fibrocartilaginous callus Collagen fiber Chondroblast Cartilage Fibrocartilaginous callus formation2 Bony callus
  10. 10. 6/5/2014 10  Bone is the body’s major calcium reservoir  Levels of calcium in the blood are maintained by controlling the rates of calcium resorption from bone into blood and of calcium deposition from blood into bone  Both nerve and muscle cells depend on calcium ions (Ca2+) to function properly  Blood clotting also requires Ca2+  Many enzymes require Ca2+ as a cofactor  Actions that work to decrease blood Ca2+ level  The thyroid gland secretes calcitonin (CT) which inhibits activity of osteoclasts  The result is that CT promotes bone formation and decreases blood Ca2+ level
  11. 11. 6/5/2014 11  Bone tissue alters its strength in response to changes in mechanical stress  Under stress, bone tissue becomes stronger through deposition of mineral salts and production of collagen fibers by osteoblasts  Unstressed bones diminishes because of the loss of bone minerals and decreased numbers of collagen fibers  The main mechanical stresses on bone are those that result from the pull of skeletal muscles and the pull of gravity  Weight-bearing activities help build and retain bone mass  The level of sex hormones diminishes during middle age, especially in women after menopause  A decrease in bone mass occurs  Bone resorption by osteoclasts outpaces bone deposition by osteoblasts  Female bones generally are smaller and less massive than males  Loss of bone mass in old age has a greater adverse effect in females  There are two principal effects of aging on bone tissue:  1) Loss of bone mass ▪ Results from the loss of calcium from bone matrix ▪ The loss of calcium from bones is one of the symptoms in osteoporosis  2) Brittleness ▪ Results from a decreased rate of protein synthesis ▪ Collagen fibers gives bone its tensile strength ▪ The loss of tensile strength causes the bones to become very brittle and susceptible to fracture
  12. 12. 6/5/2014 12

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