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Anatomy & Physiology > Chapter 6 Bones and Skeletal Tissues > Flashcards

Chapter 6 Bones and Skeletal Tissues Flashcards

1
Q

Skeletal Tissue in early development

A
  • Skeletal initially made up of cartilage and fibrous membranes
  • Bone replaces cartilage and in adult cartilage found where flexibility needed
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2
Q

Basic structure of Skeletal Cartilage

A 
large portion is water
	no blood vessels or nerves
	surrounded by perichondrium
	appositional growth 
	interstitial growth 
	hyaline cartilage – most abundant skeletal cartilage 
o	elastic cartilage 
o	fibrocartilage
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3
Q

Perichondrium

A

Dense irregular connective tissue

- Contains blood vessels that supply nutrients to cartilage via diffusion.

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4
Q

Appositional growth

A

New matrix onto surface of existing cartilage from chondroblasts in the perichondrium

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5
Q

Interstitial growth

A

Chrondrocytes in existing lacunae divide and secrete more matrix

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6
Q

Hyaline cartilage types?

A

most abundant skeletal cartilage – forms:

Articular cartilage – covers ends of most moveable joints

Costal cartilage – connects ribs to sternum

Respiratory cartilage – forms framework of larynx and reinforce respiratory passages

Nasal cartilage – supports external nose

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7
Q

Elastic cartilage

A

Similar but more flexible than hyaline cartilage

  • Contains elastin fibers in extracellular matrix
  • Found in pinna (external ear) and epiglottis (cover larynx when swallowing)
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8
Q

Fibrocartilage

A

Highly compressible and great tensile strength

  • Parallel rows of chondrocytes and thick collagen bundles
  • Cushion areas subject to pressure and stretch
  • Menisci of knees, pubic symphysis, intervertebral discs
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9
Q

Bones functions?

A

Provide:

  • Support – framework that supports body
  • Protection – surrounds brain and spinal cord and protects vital organs of thorax
  • Anchorage – skeletal muscles attach to it by tendons – bones act as levers to allow movement
  • Mineral and growth factor reservoir – calcium and phosphate – can be stored and removed from bone
  • Hematopoiesis = blood cell formation – occurs in red marrow of bones
  • Triglyceride storage – fat (energy) storage in yellow marrow of bones
  • Hormone production – osteocalcin – helps regulate insulin secretion
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10
Q

Axial skeleton

A

Forms long axis of body

Skull bones, vertebral column, rib cage

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11
Q

Appendicular skeleton

A

Bones of upper and lower limbs and girdles (pectoral and pelvic) that attach them to the axial skeleton

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12
Q

Compact bone

A

Dense outer layer of bone – looks smooth and solid

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13
Q

Spongy bone

A

Honeycomb look with bone arranged on trabeculae – flat beams

-Spaces between trabeculae filled with marrow

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14
Q

Long bones structure

A 
Diaphysis 
Epiphyses  
Epiphyseal plate 
Epiphyseal line 
Periosteum
Endosteum
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15
Q

Long-bone Diaphysis

A
  • Shaft – composed of thick collar of compact bone that surrounds
  • Medullary cavity – contains yellow marrow in adults
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16
Q

Long-bone Epiphyses

A

-Bony ends that are broader than diaphysis
• exterior = compact bone
• interior = spongy bone – contains red marrow
• articular cartilage – covers joint surface
-Cushions opposing bone ends during movement

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17
Q

Long-bone Epiphyseal plate

A

Epiphyseal plate (“growth plate”) = disc of hyaline cartilage between epiphyses and diaphysis where lengthening of bone and linear growth occurs during childhood

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18
Q

Long-bone Epiphyseal line

A

Forms when epiphyses and diaphysis fuse in adult and linear growth ceases

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19
Q

Long-bone Periosteum

A
  • Double-layered membrane surrounding external surface of bone (except on articular surface) - dense irregular connective tissue and osteogenic cells
  • Rich supply of blood vessel and nerves
  • Nutrient foramen = holes that allow blood vessels and nerves to penetrate shaft and enter marrow cavity
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20
Q

Long-bone Endosteum

A

-Delicate connective tissue layer (reticular) covers internal bone and trabeculae

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21
Q

Short bones

A
  • Roughly cube shape
  • Carpal and tarsal bones of wrist and foot
  • Sesamoid bones – form in a tendon and act to alter angle of pull – patella, base of the thumb and great toe
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22
Q

Flat bones

A
  • Thin, flattened and usually slightly curved

- Sternum, scapulae, ribs and most skull bones

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23
Q

Irregular bones

A

-Complicated shapes – coxal (hip) bones and vertebrae

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24
Q

Short, Irregular and Flat bone

A

-External layer of compact bone and filled with spongy bone (and red marrow)

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25
Q

Bone markings

A
  • Projections that bulge from outward from surface – usually stresses created by muscles pulling on bone, or where bones meet to form joints
    • head, trocanter, spine, tuberosity, line, crest, facet, condyle

-Depression and openings – allow blood vessels and nerves to pass, muscles to sit
• groove, fissure, foramen, notch, fossa

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26
Q

Bone Cells

A

osteogenic cells
osteoblasts
osteocytes
osteoclasts

27
Q

Osteogenic cells

A

-Mitotically active stem cells found in periosteum and edosteum

28
Q

Osteoblasts

A

-Mitotically active bone “building” cells that secrete bony matrix – when they become completely surrounded by bony matrix become osteocytes

29
Q

Osteocytes

A
  • Mature cells that sit in lacunae – monitor and maintain matrix
  • Respond to mechanical stimuli – bone loading, deformation, weightlessness
  • Communicate with bone remodelling cells (osteoblasts and osteoclasts)
30
Q

Osteoclasts

A

“bone-clearing” cells - giant multi-nucleated cells with ruffled border
-Located at site of bone resorption and enzymatically degrade bone

31
Q

Microscopia:

Compact bone: Osteon

A

Structure unit of compact bone

32
Q

Microscopia:

Compact bone: Haversian system

A
  • Group name for osteons

- Longated cylinder oriented parallel to the long axis of bone

33
Q

Microscopia:

Compact bone: Lamellae

A

-Layers of bony matrix
• Each layer – collagen fibers in extracellular matrix run in same direction
• Adjacent layers – collagen in different orientation from neighbour
• Resists twisting (torsion) forces

34
Q

Microscopia:

Compact bone: (Haversian) canal

A

In center of each osteon and contains blood vessels and nerve fibers

35
Q

Microscopia:

Compact bone: Volkmann’s (perforating) canals

A

-Lie at right angles to the long axis of the bone and connect the blood vessels and nerves of the medullary cavity to the central canals

36
Q

Microscopia:

Compact bone: Osteocytes

A

-Osteocytes lie in lacunae at the junctions of lamellae and canaliculi (hair-like channels) connect lacunae to each other

37
Q

Microscopia:

Compact bone: Circumferential lamellae

A

-Extend around the entire circumference of the diaphysis

• located just deep to the periosteum and just superficial to the endosteum

38
Q

Spongy bone

A

-Not as highly organized
-Trabeculae align precisely along lines of stress
Contain irregularly arranged lamellae and osteocytes connected by canaliculi

39
Q

Osteogenesis and Ossification

A

Formation of bone
• embryonic skeleton prior to week 8 gestation = entirely fibrous membranes and hyaline cartilage
• bone tissue begins to replace cartilage during fetal period (beginning 9th week gestation)
• endochondral ossification (Fig. 6.8)– bone develops by replacing hyaline cartilage
o except for clavicle – all bones below the skull form by endochondral ossification
o hyaline cartilage must be broken down as ossification proceeds
-Long bone – primary ossification center – in the center of the diaphysis
-At birth – most long bones have a bony diaphysis surrounding remnants of spongy bone, a widening medullary cavity and two cartilaginous epiphyses
-Shortly after birth – secondary ossification centers – start in one or both epiphyses
-When secondary ossification is complete – hyaline only remains:
-On the epiphyseal surface as articular cartilage
- And at the junction of the diaphysis and epiphysis = epiphyseal plates

• Intramembranous – ossification begins within fibrous connective tissue membranes formed by mesenchymal cells at about 8 weeks gestation
-Forms cranial bones of the skull (frontal, parietal, occipital, temporal) and clavicles (flat bones)

40
Q

Osteogenesis and Ossification

A
  • Endochondral ossification – bone develops by replacing hyaline cartilage
    - At birth
    - Shortly after birth-secondary ossification centres.

-Intramembranous – ossification begins within fibrous connective tissue membranes formed by mesenchymal cells at about 8 weeks gestation

41
Q

Infancy and youth

A
  • Infancy and youth – long bones lengthen entirely by interstitial growth of the epiphyseal plate cartilage and its replacement by bone
  • Epiphyseal plate maintains a constant thickness because rate of cartilage growth on epiphysis-facing side is balanced by replacement with bony tissue on diaphysis-facing side
  • Longitudinal growth accompanied by consistent remodelling of epiphyseal ends to maintain proportion between epiphyses and diaphysis
  • Involves both new bone formation and bone resorption
42
Q

All bones grow in?

A

-All bones grow in thickness by appositional growth

  • Osteoblasts beneath the periosteum secrete bone matrix on the external bone surface
  • Osteoclasts on the endosteal surface remove bone
  • Normally slightly more building up than breaking down
  • Produces thicker, stronger bone but prevents it from getting too heavy
43
Q

End of adolescence characteristics?

A
  • Chondroblasts divide less often
  • Epiphyseal plates become thinner and thinner until entirely replaced by bone
  • Epiphyseal plate closure = when longitudinal bone growth ends as bones of epiphyses and diaphysis fuse and only articular cartilage remains
  • Females ~18 years of age, male ~21 years of age
44
Q

Adult Bone remodelling

A
  • Recycle 5-7% of bone mass weekly
  • Bone remodelling – bone deposit and bone resorption occur at the surfaces of both the periosteum and endosteum
  • Controlled by genetics
  • Calcium homeostasis mechanisms
  • Mechanical and gravitational forces acting on the skeleton
  • Hormonal controls determine whether and when remodelling occurs in response to blood calcium levels
  • Mechanical stress determines where remodelling occurs
45
Q

Adult Bone remodelling: Calcium homeostasis mechanisms

A

-Maintains blood Ca++ within narrow range
•Ca++ required for numerous physiological functions
•99% of found in bony matrix
•Hypocalcemia (low blood Ca++) – can lead to hyper-excitability, muscle cramps and spasms
•Hypercalcemia (high blood Ca++) – can lead to weakened bones, non-responsiveness, kidney stones

46
Q

Mechanical and gravitational forces acting on the skeleton

A

•Keeps bones strong where stressors are acting
•Bending compresses bone on one side and subjects it to tension on the other
•Compression and tension minimal toward center of bone
-Can hollow out for lightness and use spongy bone
•Vigorous exercise leads to large increases in bone strength

47
Q

Adult Bone remodelling:

  • Hormonal controls
  • Mechanical stress
A

-Hormonal controls determine whether and when remodelling occurs in response to blood calcium levels
-Mechanical stress determines where remodelling occurs:
spongy bone is replaced every 3-4 years
compact bone is replaced every 10 yrs

48
Q

Adult Bone remodelling:

Hormonal regulation

A
  • Growth hormone = most important hormone stimulating epiphyseal plate activity during infancy and childhood
    • Hyper-secretion can result in gigantism
      * Thyroid hormone – modulates growth hormone activity ensuring proper proportion of skeleton
      • Deficiency in growth hormone or thyroid hormone can result in dwarfism
  • Testosterone in males and estrogens in females – increase in amounts during puberty stimulating growth spurt
    * Induces epiphyseal closure

-Calcium homeostasis
*Parathyroid hormone (PTH) – produced by parathyroid glands
• released when blood calcium levels decline
• stimulates osteoclasts to resorb bone – releases Ca++ into blood

   *Calcitonin – produced by C cells of thyroid gland •	less of an impact than rise and fall of PTH •	released when blood Ca++ levels rise  •	suppresses osteoclast activity and enhances osteoblast activity
49
Q

Adult Bone remodelling:

Hormones Involved?

A
  • Growth hormone
  • Testosterone in males and estrogens in females
  • Calcium homeostasis
    * Parathyroid hormone (PTH)
    * Calcitonin –
50
Q

Fractures and Bone Repair: Fractures

A

Fractures = bone breaks
Youth –trauma that twists or smashes bone (sports injuries, automobile accidents, falls)
Elderly – as bones thin and weaken

51
Q

Fractures and Bone Repair: non-displaced fractures

A

Bone ends retain their normal position

52
Q

Fractures and Bone Repair: Displaced fractures

A

Bone ends are out of alignment

53
Q

Fractures and Bone Repair: Complete fracture

A

Bone broken all the way through

54
Q

Fractures and Bone Repair: Incomplete fracture

A

Bone not broken all the way through

55
Q

Fractures and Bone Repair: Open (compound) fracture

A

Bone ends penetrate the skin

56
Q

Fractures and Bone Repair: (simple) fracture

A

Bone ends do not penetrate skin

57
Q

Fractures can be described?

A

Can be described in terms of location, external appearance, and/or nature of fracture

58
Q

Fractures and Bone Repair:

Treatment

A
  • Reduction – realignment of the broken bone ends
    * closed (external) reduction = physician’s hands realign bones
    * open (internal) reduction = bones secured together surgically with pins or wires

-Immobilization = cast or traction

59
Q

Fractures and Bone Repair:

Repair

A
  • Hematoma forms = mass of clotted blood at fracture site
    * Damage and tissue death lead to swelling, inflammation, and pain
  • Fibrocartilaginous callus forms
    * Granulation tissue (soft callus) – capillary growth into hematoma, phagocytic cells invade
    * Fibroblasts, cartilage and osteogenic cells arrive forming bulging fibrocartilaginous callus
  • Bony callus forms – within one week
    * conversion of fibrocartilaginous callus to bony (hard) callus of spongy bone
    * endochondral ossification process continues for about 2 months until firm union forms

-Bone remodelling occurs – excess material on diaphysis exterior and within medullary cavity is removed

60
Q

Bone Disorders:

Osteomalacia

A

-Number of disorders where bones are poorly mineralized
calcium salts are not adequately deposited so bones are weak and soft

main symptom = pain when weight is put on affected bones

rickets = disease in children and more severe than adult osteomalacia due to rapid growth of bones
*bowed legs, deformities of pelvis, skull and rib cage

caused by insufficient calcium in diet or vitamin D deficiency
61
Q

Bone Disorders:

Osteoporosis characteristics?

A

-Group of diseases in which bone resorption outpaces bone deposit

bones become so fragile – strong sneeze or stepping off curb can break bone

composition of the matrix remains normal 

bone mass decreases – becoming porous and light

spongy bone of spine most vulnerable and compression fractures of vertebrae are common

neck of femur very susceptible to fracture
62
Q

Bone Disorders:

Osteoporosis risk factors?

A

-Aged – especially postmenopausal women
• 30% of all Caucasian women (most susceptible group) will experience bone fracture due to osteoporosis
• androgens (male) and estrogens (female) – sex hormones help maintain health and normal density of bone – restrain osteoclasts and promote osteoblast activity
*Estrogen deficiency strongly implicated in osteoporosis in older women

  • Petite body form
  • Insufficient exercise
  • Poor diet – especially in calcium and protein
  • Abnormal vitamin D receptors
  • Smoking (reduces estrogen levels)
  • Hormone-related conditions: Hyperthyroidism, low thyroid stimulating hormone, diabetes mellitus
63
Q

Bone Disorders:

Osteoporosis Treatment?

A
  • Supplemental calcium and vitamin D
  • Weight-bearing exercise
  • Hormone replacement therapy (HRT) – slows bone loss but increased risk of heart attack, stroke and breast cancer
  • Bisphosphonates – decrease osteoclast activity and number
  • Selective estrogen receptor modulators (SERMS) – e.g. raloxifene – estrogen-like effect but reduced side effects
64
Q

Bone Disorders:

Paget’s Disease

A
  • Excessive and haphazard bone deposit and resorption
  • Abnormally high ratio of spongy bone to compact bone and reduced mineralization
  • Spotty weakening of bones
  • Osteoclast activity decreases but osteoblast activity continues – irregular thickenings
    • spine, pelvis, femur and skull most often involved
    • become increasing deformed and painful

-Cause unknown – may be viral induced - occurrence low, over age of 40

Anatomy & Physiology (10 decks)

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