1. Chapter 7 and 9 Bone Tissue and Articulations
Tissues and organs of the skeletal system
Histology of osseous tissue
Bone development
Physiology of osseous tissue
Bone disorders

2. Bone as a Tissue Dynamic tissue that continually remodels itself
Bones and bone tissue
bone or osseous tissue is a connective tissue with a matrix hardened by minerals (calcium phosphate)
bones make up the skeletal system
individual bones are made up of bone tissue, marrow, cartilage & periosteum
Functions of the skeletal system
support, protection, movement, blood formation, mineral reservoir, pH balance & detoxification

3. Shapes of Bones

4. Structure of a Flat Bone
External and internal surfaces of flat bone are composed of compact bone
Middle layer is spongy bone (diploe). No marrow cavity
Blow to the skull may fracture outer layer and crush diploe, but not harm inner compact bone

5. Structure of a Long Bone
Periosteum & articular cartilage
Compact & spongy bone
Endosteum
Yellow marrow

6. General Features of Bones
Shaft (diaphysis) is cylinder of compact bone containing marrow cavity (medullary cavity) & lined with endosteum (layer of osteopenic cells and reticular connective tissue)
Enlarged ends (epiphyses) are spongy bone covered with a layer of compact bone
enlarged to strengthen joint & provide for attachment of tendons and ligaments
Joint surface covered with articular cartilage (lubrication)
Remainder of bone covered with periosteum
outer fibrous layer of collagen fibers continuous with tendons or perforating(Sharpey’s) fibers that penetrate into bone matrix
inner osteogenic layer important for growth & healing
Epiphyseal plate or line depends on age

7. Cells of Osseous Tissue (1)
Osteogenic cells reside in endosteum, periosteum or central canals
arise from embryonic fibroblasts and become only source for new osteoblasts
multiply continuously & differentiate into osteoblasts in response to stress or fractures
Osteoblasts form and help mineralize organic matter of matrix
Osteocytes are osteoblasts that have become trapped in the matrix they formed
cells in lacunae connected by gap junctions inside canaliculi
signal osteoclasts & osteoblasts about mechanical stresses

8. Cells of Osseous Tissue (2)
Bone destroyers (Osteoclasts) develop in bone marrow by the fusion of 3-50 of the same stem cells that give rise to monocytes found in blood
Reside in pits called resorption bays that they have eaten into the surface of the bone

9. Matrix of Osseous Tissue
Dry weight is 1/3 organic & 2/3 inorganic matter
Organic matter
collagen, glycosaminoglycans, proteoglycans & glycoproteins
Inorganic matter
85% crystallized calcium phosphate salt (hydroxyapatite)
10% calcium carbonate
5 % other minerals (fluoride, sulfate, potassium, magnesium)
Combination provides for strength & resilience
minerals resist compression; collagen resists tension
fiberglass = glass fibers embedded in a polymer
bone adapts to tension and compression by varying proportions of minerals and collagen fibers

10. Compact Bone Osteon (haversian system) = basic structural unit
cylinders of tissue formed from layers (lamellae) of matrix arranged around central canal holding a blood vessel
collagen fibers alternate between right- and left-handed helices from lamella to lamella
osteocytes connected to each other and their blood supply by tiny cell processes in canaliculi
Perforating canals or Volkmann canals
vascular canals perpendicularly joining central canals
Circumferential or outer lamellae
Form in rings around the Haversian (Osteonic) Canal

11. Histology of Compact Bone

12. Blood Vessels of Compact Bone

13. Spongy Bone
Spongelike appearance formed by rods and plates of bone called trabeculae
spaces filled with red bone marrow
Trabeculae have few osteons or central canals
no osteocyte is far from blood of bone marrow
Provides strength with little weight
trabeculae develop along bone’s lines of stress

14. Spongy Bone Structure and Stress

15. Bone Marrow
Soft tissue that occupies the medullary cavity of a long bone or the spaces amid the trabeculae of spongy bone
Red marrow looks like thick blood
mesh of reticular fibers and immature cells
hemopoietic means produces blood cells
found in vertebrae, ribs, sternum, pelvic girdle and proximal heads of femur and humerus in adults
Yellow marrow
fatty marrow of long bones in adults
Gelatinous marrow of old age
yellow marrow replaced with reddish jelly

16. Intramembranous Ossification
Produces flat bones of skull & clavicle
“within membrane”
Steps of the process
mesenchyme condenses into a sheet of soft tissue
transforms into a network of soft trabeculae
osteoblasts gather on the trabeculae to form osteoid tissue (uncalcified bone)
calcium phosphate is deposited in the matrix transforming the osteoblasts into osteocytes
osteoclasts remodel the center to contain marrow spaces & osteoblasts remodel the surface to form compact bone
mesenchyme at the surface gives rise to periosteum

17. Intramembranous Ossification

18. Endochondral Ossification
“within cartilage” - bone arises from hyaline cartilage
Only partially underway at the time of birth
Primary ossification center - in shaft of long bones
Secondary ossification center - in the ends of long bone

19. Endochondral Ossification - steps
Primary ossification center forms in cartilage model
chondrocytes near the center swell to form primary ossification center
matrix is reduced & model becomes weak at that point
cells of the perichondrium produce a bony collar
cuts off diffusion of nutrients and hastens their death
Primary marrow space formed by periosteal bud
osteogenic cells invade & transform into osteoblasts
osteoid tissue deposited and calcified into trabeculae at same time osteoclasts work to enlarge the primary marrow cavity

20. Primary Ossification Center & Marrow Space
Both form in center of cartilage model -- same process begins again subsequently at ends of cartilage model.

21. Secondary Ossification Center
Begin to form in the epiphyses near time of birth
Same stages occur as in primary ossification center
result is center of epiphyseal cartilage being transformed into spongy bone
Hyaline cartilage remains on joint surface as articular cartilage and at junction of diaphysis & epiphysis (epiphyseal plate)
each side of epiphyseal plate has a metaphysis

22. Metaphysis & Secondary Ossification Center
Metaphysis is cartilagenous material that remains as growth plate between medullary cavity & secondary ossification centers in the epiphyses.

23. The Fetal Skeleton at 12 Weeks

24. Epiphyseal Plates

25. Bone Growth and Remodeling
Grow and remodel themselves throughout life
growing brain or starting to walk
athletes or history of manual labor have greater density & mass of bone
Cartilage grows by both appositional & interstitial growth
Bones increase in length by interstitial growth of epiphyseal plate
Bones increase in width by appositional growth
osteoblasts lay down matrix in layers parallel to the outer surface & osteoclasts dissolve bone on inner surface
if one process outpaces the other, bone deformities occur (osteitis deformans)

26. Achondroplastic Dwarfism
Short stature but normal-sized head and trunk
long bones of the limbs stop growing in childhood but other bones unaffected
Result of spontaneous mutation when DNA is replicated
mutant allele is dominant
Pituitary dwarf has lack of growth hormone
short stature with normal proportions

27. Mineral Deposition
Mineralization is crystallization process in which ions (calcium, phosphate & others) are removed from blood plasma & deposited in bone tissue
Steps of the mineralization process
osteoblasts produce collagen fibers that spiral along the length of the osteon in alternating directions
fibers become encrusted with minerals hardening matrix
ion concentration must reach the solubility product for crystal formation to occur & then positive feedback forms more
Ectopic ossification is abnormal calcification
may occur in lungs, brain, eyes, muscles, tendons or arteries (arteriosclerosis)

28. Mineral Resorption
Process of dissolving bone & releasing minerals into the blood
performed by osteoclasts “ruffled border”
hydrogen pumps in the cell membrane secrete hydrogen ions into the space between the osteoclast & the bone
chloride ions follow by electrical attraction
hydrochloric acid with a pH of 4 dissolves bone minerals
an enzyme (acid phosphatase) digests the collagen
Dental braces reposition teeth, creating greater pressure on the bone on one side of the tooth and less on the other side
increased pressure stimulates osteoclasts; decreased pressure stimulates osteoblasts to remodel jaw bone

29. Functions of Calcium & Phosphate
Phosphate is a component of DNA, RNA, ATP, phospholipids, & acid-base buffers
Calcium is needed for communication between neurons, muscle contraction, blood clotting & exocytosis
Calcium plasma concentration is 9.2 to 10.4 mg/dL -- 45% is as Ca+2, rest is bound to plasma proteins & is not physiologically active
Phosphate plasma concentration is 3.5 to 4.0 mg/dL & occurs in 2 forms: HPO4 -2 & H2PO4-

30. Ion Imbalances Changes in phosphate concentration have little effect
Changes in calcium can be serious
hypocalcemia is deficiency of blood calcium
causes excessive excitability of nervous system leading to muscle spasms, tremors or tetany
laryngospasm may cause suffocation
calcium normally binds to cell surface contributing to resting membrane potential
with less calcium, sodium channels open more easily exciting neuron
hypercalcemia
excessive calcium binding to cell surface makes sodium channels less likely to open, depressing nervous system
Calcium phosphate homeostasis depends on calcitriol, calcitonin & PTH

31. Carpopedal Spasm
Hypocalcemia causing overexcitability of nervous system and muscle spasm of hands and feet

32. Calcitriol (Activated Vitamin D)
Produced by the following process
UV radiation penetrating the epidermal keratinocytes converts a cholesterol derivative (7-dehydrocholesterol) to previtamin D3 and then (cholecalciferol) D3
liver adds OH to convert D3 to calcidiol
kidney adds OH to convert calcidiol to calcitriol
Calcitriol behaves as a hormone (blood-borne messenger)
stimulates intestine to absorb calcium, phosphate & magnesium
weakly promotes urinary reabsorption of calcium ions
promotes osteoclast activity to raise blood calcium concentration to the level needed for bone deposition
Abnormal softness of the bones is called rickets in children and osteomalacia in adults

33. Calcitriol Synthesis & Action

34. Hormonal Control of Calcium Balance
Calcitriol, PTH and calcitonin maintain normal blood calcium concentration.

35. Calcitonin
Secreted by C cells of the thyroid gland when calcium concentration rises too high
Functions
reduces osteoclast activity by as much as 70% in 15 minutes
increases the number & activity of osteoblasts
Important role in children, but little effect in adults
calcitonin deficiency is not known to cause any disease in adults
may be useful in reducing bone loss in osteoporosis

36. Parathyroid Hormone
Secreted by the parathyroid glands found on the posterior surface of the thyroid gland
Released when calcium blood level is too low
Functions
binds to osteoblasts causing them to release osteoclast-stimulating factor that stimulates osteoclast multiplication & activity
promotes calcium resorption by the kidneys
promotes calcitriol synthesis in the kidneys
inhibits collagen synthesis and bone deposition by osteoblasts
Injection of low levels of PTH can cause bone deposition

37. Negative Feedback Loops in Calcium

38. Other Factors Affecting Bone
20 or more hormones, vitamins & growth factors not well understood
Bone growth especially rapid at puberty
hormones stimulate proliferation of osteogenic cells and chondrocytes in growth plate
adolescent girls grow faster than boys & reach their full height earlier (estrogen has stronger effect)
males grow for a longer time
Growth ceases when epiphyseal plate “closes”
anabolic steroids may cause premature closure of growth plate producing short adult stature

39. Fractures and Their Repair
Stress fracture is a break caused by abnormal trauma to a bone
car accident, fall, athletics, etc
Pathological fracture is a break in a bone weakened by some other disease
bone cancer or osteoporosis
Fractures are classified by their structural characteristics -- causing a break in the skin, breaking into multiple pieces, etc
or after a physician who first described it

40. Types of Bone Fractures (Table 7.3)

41. Healing of Fractures
Normally healing takes weeks (longer in elderly)
Stages of healing
fracture hematoma (1)
broken vessels form a blood clot
granulation tissue (2)
fibrous tissue formed by fibroblasts & infiltrated by capillaries
callus formation (3)
soft callus of fibrocartilage replaced by hard callus of bone in 6 weeks
remodeling (4) occurs over next 6 months as spongy bone is replaced with compact bone

42. Healing of Fractures

43. Fractures and Their Repairs

44. Osteoporosis Most common bone disease
Bones lose mass & become brittle due to loss of both organic matrix & minerals
risk of fracture of hip, wrist & vertebral column
lead to fatal complications such as pneumonia
widow’s (dowager’s) hump is deformed spine
Postmenopausal white women at greatest risk
by age 70, average loss is 30% of bone mass
ERT slows bone resorption, but best treatment is prevention -- exercise & calcium intake (1000 mg/day) between ages 25 and 40
Therapies to stimulate bone deposition are still under investigation

45. Effects of Osteoporosis

46. Chapter 9 Joints Fibrous, cartilagenous and bony joints
Synovial joints
Anatomy of selected diarthroses
knee joint

47. Joints and Their Classification
Arthrology is the study of the joints
Kinesiology is the study of musculoskeletal movement
Joints are classified by their freedom of movement
diarthrosis (freely movable); amphiarthrosis (slightly movable) and synarthrosis (little or no movement)
Joints are classified by the manner adjacent bones are joined -- fibrous, cartilaginous, bony and synovial joints

48. Joint Classification

49. Fibrous, Cartilaginous & Bony Joints
Fibrous joints have collagen fibers spanning the space between bones
sutures, gomphoses & syndesmoses
Cartilaginous joints have 2 bones bound to each other by cartilage
synchondroses or symphyses
Bony joints have 2 bones fused by osseous tissue
synostoses in early adulthood

50. Fibrous Joint -- Sutures
Immovable fibrous joints that bind the bones of the skull to each other
Serrate sutures appear as interlocking wavy lines
coronal, sagittal & lambdoid sutures
Lap or squamous sutures are 2 bones with overlapping beveled edges
temporal & parietal bones
Plane or butt sutures have straight, nonoverlapping edges
palatine processes of the maxillae

51. Types of Sutures

52. Fibrous Joint -- Gomphoses
Attachment of a tooth to its socket is a joint called a gomphoses
Tooth held in place by fibrous periodontal ligament
collagen fibers that extend from bone of jaw to tooth
Allows tooth to move a little while chewing

53. Fibrous Joint -- Syndesmoses
Joint in which two bones are bound by a ligament only (interosseus membrane)
Most movable of fibrous joints
Interosseus membranes unite radius to ulna and tibia to fibula

54. Cartilaginous Joint -- Synchondroses
Bones are joined by hyaline cartilage
rib attachment to sternum by
epiphyseal plate in children binds epiphysis and diaphysis

55. Cartilaginous Joint -- Symphyses
2 bones joined by fibrocartilage
pubic symphysis and intervertebral discs
Only slight amount of movement is possible

56. General Anatomy of Synovial Joints
Articular capsule
fibrous capsule lined by synovial membrane
continuous with periosteum
Synovial fluid
viscous slippery fluid rich in albumin & hyaluronic acid & similar to raw egg white
Articular cartilage
hyaline cartilage covering the joint surfaces
Meniscus is pad of fibrocartilage in jaw, wrist, knee and sternoclavicular joints
absorbs shock, guides bone movements & distributes forces
Tendon attaches muscle to bone
Ligament attaches bone to bone

57. Tendon Sheaths and Bursae
Bursa is saclike extension of joint capsule that extends between nearby structures allowing them to slide more easily past each other
Tendon sheaths are elongated cylinders of connective tissue lined with synovial membrane & wrapped around a tendon
numerous in hand and foot

58. Ball-and-Socket Joints
Smooth hemispherical head fits within a cuplike depression
head of humerus into glenoid cavity of scapula
head of femur into acetabulum of hip bone
Multiaxial joint

59. Hinge Joints
One bone with convex surface that fits into a concave depression on other bone
ulna and humerus at elbow joint
femur and tibia at knee joint
finger and toe joints
Monoaxial joint

60. Saddle Joints
Each articular surface is shaped like a saddle, concave in one direction and convex in the other
trapeziometacarpal joint at the base of the thumb
Biaxial joint
more movable than a condyloid or hinge joint forming the primate opposable thumb

61. Pivot Joints
One bone has a projection that fits into a ringlike ligament of another
First bone rotates on its longitudinal axis relative to the other
atlantoaxial joint (dens and atlas)
proximal radioulnar joint allows the radius during pronation and supination

62. Gliding Joints
Flat articular surfaces in which bones slide over each other
Limited monoaxial joint
Considered amphiarthroses

63. Condyloid (ellipsoid) Joints
Oval convex surface on one bone fits into a similarly shaped depression on the next
radiocarpal joint of the wrist
metacarpophalangeal joints at the bases of the fingers
Biaxial joints

64. Flexion, Extension & Hyperextension
Flexion decreases the angle of a joint
bending elbow or wrist
Extension straightens a joint and returns a body part to the anatomical position
Hyperextension is extension of a joint beyond 180 degrees

65. Abduction & Adduction
Abduction is movement of a part away from the midsagittal line -- raising the arm to the side
Adduction is movement towards the midsagittal line

66. Abduction & Adduction
Abduction is spreading the fingers away from the midline (middle finger)
Adduction is movement is returning the fingers to the anatomical position

67. Elevation and Depression
Elevation is a movement that raises a bone vertically
mandibles are elevated during biting & clavicles during a shrug
Depression is lowering the mandible or the shoulders

68. Protraction & Retraction
Protraction is movement of a bone anteriorly (forward) on a horizontal plane
thrusting the jaw forward, shoulders or pelvis forward
Retraction is movement of a bone posteriorly

69. Lateral & Medial Excursion
Lateral excursion is sideways movement to right or left
Medial excursion is movement back to the midline
Side-to-side grinding movements occurring during chewing

70. Circumduction
Movement in which one end of an appendage remains stationary while the other end makes a circular motion
Sequence of flexion, abduction, extension & adduction movements
baseball player winding up for a pitch

71. Lateral and Medial Rotation
Movement of a bone turning on its longitudinal axis
rotation of trunk, thigh, head or arm
Medial rotation turns the bone inwards
Lateral rotation turns the bone outwards

72. Supination & Pronation
Occurs in the forearm and foot
Supination
rotation of forearm so that the palm faces forward
inversion and abduction of foot (raising the medial edge of the foot)
Pronation
rotation of forearm so the palm faces to the rear
eversion and abduction of foot (raising the lateral edge of the foot)

73. Opposition & Reposition
Opposition is movement of the thumb to approach or touch the fingertips
Reposition is movement back to the anatomical position
Important hand function that enables the hand to grasp objects

74. Dorsiflexion & Plantar Flexion
Dorsiflexion is raising of the toes as when you swing the foot forward to take a step (heel strike)
Plantarflexion is extension of the foot so that the toes point downward as in standing on tiptoe

75. Inversion & Eversion
Inversion is a movement in which the soles are turned medially
Eversion is a turning of the soles to face laterally

76. Range of Motion Varies greatly from one type of joint to another
Measured with goniometer
Factors affecting ROM and joint stability
structure & action of the muscles
proprioceptors keep track of joint position & muscle tone
structure of the articular surfaces
strength and tautness of ligaments, tendons & capsule
gradual stretching of ligaments increases range of motion
“double-jointed” people have unusually long or slack ligaments

77. The Knee Joint Most complex diarthrosis of the body
patellofemoral = gliding joint
tibiofemoral = gliding with slight rotation & gliding possible in flexed position
Joint capsule anteriorly consists of patella & extensions of quadriceps femoris tendon
Rest of capsule strengthened by both extracapsular & intracapsular ligaments

78. Knee Joint

79. Knee Joint Medial & lateral meniscus absorb shock & shape joint
Anterior & lateral cruciate ligaments limit anterior & posterior sliding movements
Medial and lateral collateral ligaments prevent rotation of extended knee

80. Dissection of Knee Joint

81. Arthritis & Artificial Joints
Arthritis is a broad term for pain & inflammation
Osteoarthritis results from years of joint wear
articular cartilage softens and degenerates
accompanied by crackling sounds called crepitus
bone spurs develop on exposed bone tissue causing pain
Rheumatoid arthritis is autoimmune attack on joint
antibodies attack synovial membrane, enzymes in synovial fluid degrade the cartilage, bones ossify
remissions occur, steroids & aspirin control inflammation
Arthroplasty is replacement of diseased joint with artificial device called prosthesis

82. Rheumatoid Arthritis

83. Joint Prostheses