1. Skeletal System: Bones and Bone Tissue

2.  Four major components:  BONES  CARTILAGE  TENDONS  LIGAMENTS

3.  1. Support - provides hard framework for soft tissue  Strong bones to bear weight  2. Protection of underlying organs  Skull – Brain  Rib cage - heart & lungs  3. Movement - skeletal muscles use bones as levers  Tendons hold muscles to bones  Joints – two bones come together  Ligaments –provide limited movement

4.  4. Storage  Calcium and Phosphorous  Fat stored in marrow cavities  5. Blood cell production (Hematopoiesis)  Red bone marrow  blood cells and platelets

5.  Hyaline cartilage  Most bones develop from this type of cartilage  Fibrocartilage  Elastic cartilage

9.  Hyaline – specialized cells that produce matrix surrounding cells  Chondroblasts – produce new cartilage matrix  Chondrocyte – cells that maintain the cartilage  Lacunae – space within the matrix  Matrix – contains collagen, provides strength

10.  Perichondrium – double layered connective tissue sheath  Covers most cartilage  Blood vessels and nerves penetrate outer layer of perichondrium  Does not enter cartilage matrix  Nutrients diffuse through cartilage matrix to reach chondrocytes

11.  Articular cartilage  Cartilage that covers end of bones where they form joints  Has no perichondrium, blood or nerves

13.  Bone  connective tissue  Bone matrix  Steel bars is collagen fibers, weight bearing strength or cement is mineral components  Organic components (35%) Primarily collagen  Inorganic mineral salts (65%) Primarily calcium phosphate Hydroxyapatite Gives bone its hardness; resists compression

14.  (b) If minerals are removed, bone is too bendable (collagen is present)  (c) If collagen removed, bone is too brittle (minerals are present)

15.  Osteoblasts  Active in bone formation = ossification  Form collagen and hydroxyapatite crystals

16.  Osteocytes  Essentially osteoblasts that are surrounded by bone matrix  Relatively inactive  Found in compact and spongy bone

17.  Osteoclasts  Cells used to breakdown bone (bone resorption)  Stimulated by need for calcium & phosphate in the body  Breaks down mineral salts (demineralization or decalcification)  Resorption starts to exceed formation as people age

18.  Bone classified based on collagen fibers within bone matrix:  1. Woven bone – collagen randomly oriented in many directions  Formed during fetal development or repair of fracture  Remodeling forms lamellar bone

20.  2. Lamellar bone – mature bone organized into thin sheets or layers (lamallae)  Collagen fibers of one lamallae lie parallel to one another

21.  Bone classified by amount of matrix relative to amount of space in bone  Cancellous – less bone matrix, more space  Compact – more bone matrix less space; denser

22.  Trabeculae: interconnecting rods or plates of bone  Between the trabeculae - filled with bone marrow and blood vessels  Porous appearance  No blood vessels, osteocytes obtain nutrients through canaliculi  Covered with single layers of cells of osteoblasts and few osteoclasts

23. Denser Has fewer spaces than cancellous bone Blood vessels enter the substance of the bone itself

24. Figure 6.6

25. Osteon or Haversian System Basic unit of compact bone Consists of a central canal run parallel to surface of bone Contains blood vessels Concentric lamellae - cylinders of bone

26.  Circumferential lamellae – outer surfaces of compact bone  Interstitial lamellae – in between osteons  Perforating or Volkmann’s canal – Osteocytes receive nutrients and eliminate waste products through canal system Contain blood vessels that then branch to enter central canal

27. Figure 6.6

28.  Long – longer than wide  Ex. Upper and lower limbs  Short – as broad as wide  Ex. Carpals (wrist) and tarsals (ankle)

29.  Flat – thin, flattened shape, curved  Ex. Ribs, sternum, skull, scapulae  Irregular – doesn’t fit in other category  Ex. Vertebrae, facial

30.  Diaphysis  Shaft of bone  Mostly compact bone, can contain cancellous  Epiphysis  End of the bone - Cancellous bone  Covered with articular cartilage  Develops from center of ossification  Bones with one or more epiphyses: Long bone of arm Forearm Thigh bone Lower leg

31.  Epiphyseal plate - responsible for growth in length of bone Composed of hyaline cartilage Present until growth stops Then becomes epiphyseal line

33.  Medullary cavity - central, hollow cavity  Filled with marrow  At birth, there’s more red marrow  Conversion from red to yellow as you age  Yellow marrow completely replaces red in long bones of limbs, except in proximal part of arm and thigh bones

34.  Periosteum – connective tissue membrane covers outside of bone  Fibers of tendon that bind muscle to bone become continuous with fibers of periosteum.  Sharpey’s fibers - fibers that penetrate into the bone matrix Strengthen attachment of tendon to bone

36.  Endosteum  Similar to inner layer of periosteum  Lines all internal spaces including spaces in cancellous bone

37. Figure 6.3a-c

39.  1. What are the 4 different types of bones?  2. Identify the following:  The end of a bone is called –  The shaft of the bone is called –  3. What is found in the medullary cavity?  4. What is the difference between red and yellow marrow?

40.  5. What is the name of cells that make new cartilage?  6. What is the name of cells that maintain cartilage?  7. What makes up the bone matrix?  8. What is the difference between cancellous and compact bone?

41.  1. What are the 4 different types of bones?  Long, short, flat and irregular  2. Identify the following:  The end of a bone is called – Epiphysis  The shaft of the bone is called – Diaphysis  3. What is found in the medullary cavity?  - Bone marrow

42.  4. What is the difference between red and yellow marrow?  Red – blood formation  Yellow – adipose tissue  5. What is the name of cells that make new cartilage?  Chondroblasts  6. What is the name of cells that maintain cartilage?  Chondrocytes

43.  7. What makes up the bone matrix?  Collagen (35%)  Calcium phosphate (65%) – aka hydroxy apatite  8. What is the difference between cancellous and compact bone?  Cancellous – less bone matrix, more space between  Compact – More bone matrix, less space, denser

44.  Flat Bones  No diaphyses or epiphyses  A sandwich of cancellous (spongy) bone between compact

45.  Short and Irregular bones  Similar composition to epiphyses of long bones  Compact bone surfaces that surround cancellous bone center with small spaces filled with marrow

46.  Short and Irregular bones  Not elongated and have no diaphyses  Certain regions of these bones have epiphyseal growth plates and small epiphyses

47.  Bone formation occurs in 2 different ways  Intramembranous ossification Occurs in connective tissue membrane  Endochondral ossification Occurs in cartilage  Both produce woven bone that is then remodeled to lamellar

48.  Internally, osteoblasts form cancellous bone  Externally, osteoblasts form compact bone  Forms many flat skull bones, part of mandible, diaphyses of clavicles  When remodeled, indistinguishable from endochondral bone

49.  ALL bones except some bones of the skull and clavicles  Bones are modeled in hyaline cartilage  Begins forming late in 2nd month of human development

50.  Continues forming until early adulthood  Blood vessel invade cartilage, matrix becomes calcified and chondrocytes die  Perichondrium becomes periosteum

51. Figure 6.10

53.  1. How are short, flat and irregular bones different from long bones?  2. What is “remodeling”?  3. How is intramembranous ossification different from endochondral ossification?

54.  1. How are short, flat and irregular bones different from long bones?  Short bones have no diaphysis or epiphysis; cancellous bone sandwiched between compact  2. What is “remodeling”?  Bone metabolism  Life long process where mature bone tissue is removed from the skeleton and new tissue is formed

55.  3. How is intramembranous ossification different from endochondral ossification?  Intramembranous Forms the skull, shoulder blades, jaw Occurs in the connective tissue membrane Occurs in fetal development Cartilage is NOT present  Endochondral ALL other bones Cartilage (hyaline) is present Continues forming until early adulthood

56.  Bone formation happens on surface of older bone or cartilage  Long bones increase in length because of growth at epiphyseal plate  Involves formation of new cartilage from inside of preexisting cartilage and bone growth of surface of cartilage

57.  Interstitial growth – new cells formed from within tissue (cyte cells)  Appositional growth – new cells added to surface of tissue by blast cells

58. Composed of 4 zones:  1. Zone of resting cartilage – nearest epiphysis and contains random chondrocytes that don’t divide rapidly  2. Zone of proliferation – produce new cartilage through interstitial cartilage growth; chondrocytes form stacks

59.  3. Zone of hypertrophy – chondrocytes produced mature and enlarge  cells nearer epiphysis: younger and actively proliferate  cells nearer diaphysis: older and maturing

60.  4. Zone of calcification – thin and contains hypertrophied chondrocytes and calcified cartilage matrix  Hypertrophied chondrocytes die  Blood vessels from diaphysis grow into area  Connective tissue surround blood vessels contains osteoblasts  Osteoblasts make new bone matrix

61.  In epiphyseal plates of growing bones...  Length of diaphysis increases  Cells push the epiphysis away from the diaphysis  Once bones reach adult size, epiphyseal plate ossifies and becomes epiphyseal line  Occurs between 12-25 yrs of age (depends on bone and individual)

63.  Long bones increase in width; other bones increase in size or thickness  Rapid growth – young bones or puberty

64.  Size and shape of a bone determined genetically but can be modified  Influenced by  Nutrition  Hormones  Nutrition  Lack of calcium, protein and other nutrients during growth and development can cause bones to be small; illness and malnutrition

65.  Nutrition con’t  Vitamin D Necessary for absorption of calcium from intestines Can be eaten or manufactured in the body Rickets: lack of vitamin D during childhood Osteomalacia: lack of vitamin D during adulthood leading to softening of bones

66.  Nutrition con’t  Vitamin C Necessary for collagen synthesis Can cause growth retardation Scurvy: due to deficiency of vitamin C Ulceration & hemorrhage in any area of body Lack of vitamin C also causes wounds not to heal, teeth to fall out

68.  Hormones  Growth hormone stimulates interstitial cartilage growth appositional bone growth  Thyroid hormone required for growth of all tissues

69.  Hormones  Sex hormones : estrogen and testosterone Cause growth at puberty, but also cause closure of the epiphyseal plates Females stop growing earlier than males because estrogen causes quicker closure of epiphyseal plate

70.  Bone deposit and removal  Occurs at periosteal and endosteal surfaces  Bone deposition – accomplished by osteoblasts  Bone reabsorption – accomplished by osteoclasts  Converts woven bone into lamellar bone  Involves bone growth, change in bone shape, adjustment of bone stress, and bone repair

71.  Completed through osteoclasts and osteoblasts  Travel through bone, removing old bone matrix and replacing it with new bone matrix  These specific cells renew the entire skeleton every 10 years

74.  1. Hematoma formation - blood clot formation  Hematoma – localized mass of blood released from blood vessels but confined within a space  Injury followed by inflammation and swelling

75.  2. Callus formation - mass of tissue that forms at a fracture site and connects the broken ends of the bone  Internal and external callus  Cartilage is formed  Osteoblasts invade = New bone is formed  Bone/cartilage (woven bone) stabilizes broken bone

76.  3. Callus ossification  Callus replaced by woven, cancellous bone  Stronger external callus  4. Bone remodeling  Replacement of cancellous bone and damaged material by compact bone  Remodeling takes sometimes more than a year; repaired zone thicker than adjacent bone

78.  Open (compound) – bone break with open wound. Bone may be sticking out of wound.  Closed (simple) – Skin not perforated.  Complicated – soft tissue around closed fracture is damaged  Incomplete - doesn’t extend across the bone. (2+ fragments)  Complete – does extend across the bone

79.  Greenstick – incomplete fracture that occurs on the convex side of the curve of a bone  Hairline: incomplete where two sections of bone do not separate  Common in skull fractures

80.  Rickets  Soft bones  Vitamin D/Calcium/Phosphate deficiency in CHILDREN  If the blood levels of these mineral become too low, hormones cause Ca and P to be released from bones  Osteomalacia  Softening of bones  Vitamin D deficiency in ADULTS  Leads to improper calcium absorption

81.  Osteomalacia  Normal bone density Not enough Vitamin D in the diet Note enough exposure to sunlight Lactose intolerant  Bone fractures happen with very little injury  Widespread bone pain  Complete healing with treatment takes place in 6 months

83.  Osteomyelitis  Bacterial infections (or fungal) of bones  Infections spread via the blood from wounds, boils, TB  Infection can start after bone surgery Especially when rods or plates are used  Leads to destruction of bone

84.  A condition of abnormally increased height  Results from excessive cartilage and bone formation at epiphyseal plates of long bones. What causes Giantism?

85.  Pituitary giantism – excess secretion of pituitary growth hormone. Robert Wadlow's height of 8' 11.1" qualifies him as the tallest person in history.

86.  Acromegaly – excess pituitary growth hormone secretion  Involves growth of connective tissue, including bones, after epiphyseal plates ossified  Mainly involves increased diameter of all bones

87.  Growth hormone deficiency involves abnormally short stature with normal body proportions.

88.  Achondroplastic  Most common type  long bones stop growing in childhood normal torso, short limbs  Parents are normal height  Pituitary dwarfism  lack of growth hormone  normal proportions with short stature

89.  Bone matrix decreases  More brittle due to lack of collagen  Also less hydroxyapetite (calcium phosphate)  Bone mass decreases  Highest around 30 yrs of age  Male bone mass denser due to testosterone and greater weight  Rate of bone loss increases 10 fold after menopause

90.  Increased bone fractures  Bone loss causes deformity, loss of height, pain, stiffness  Stooped posture  Loss of teeth

91.  Decrease in bone density  Depletion of calcium and phosorphous  Porous bone  Occurs when rate of bone resorption exceeds rate of bone formation  Bone is deformed and prone to fracture  Occurs mostly in older people

92.  Occurrence increases in age  Strong genetic component  60% genetic; 40% environmental or lifestyle (diet & exercise)

93.  Loss of bone mass  Curvature of spine  Muscle weakness  Pain sensations  Impaired respiration

94.  Postmenopausal women (> 50) at greatest risk  Decrease of estrogen – maintains bone mass  Estrogen maintains density in both sexes (inhibits resorption)  Males, reduction of testosterone levels  Testosterone levels don’t decrease significantly until age 65

95.  Treatments  HRT – uses estrogen to decrease osteoclast numbers Reduces bone loss  SERMS – class of drugs bind to estrogen receptors Inhibit osteoclasts, stimulate osteoblasts, increase bone mass  Prevention -- exercise and calcium intake (1000 mg/day) between ages 25 and 40

97.  What you need to know…  The 5 functions of the skeletal system  Components of the bone matrix  Types of cartilage found in the body  Chondroblasts vs chondrocytes vs condroclasts  Osteoblasts vs osteocytes vs osteoclasts  Compact vs cancellous bones  Bone types & examples  Compare & contrast the 4 bone types  Types of marrow  Factors affecting bone growth  Labeling diagram of compact bone (ex – osteons)