Chapter 6: Cartilage and Bone Tissue

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Chapter 6 Cartilage and Bone Tissue

• What does the skeletal system do for us?

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Cartilage

• Location
• Ear and nose
• Respiratory system
• Movable joints
• Costal cartilage
• Intervertebral disks
• Pubic symphysis
• Embryonic

(6.1)
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Cartilage Tissue

• Specialized CT
• Chondrocytes in lacunae
• Solid ground substance and fibers
• Avascular
• No nerves
• Perichondrium
• 60-80 water resilient

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Hyaline Cartilage

• Most abundant
• Locations
• Joints
• Trachea
• Costal cartilages
• Network of collagen fibers

(6.1)
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Elastic Cartilage

• Elastic fibers
• Locations
• External ear
• Epiglottis

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Fibrocartilage

• Bundles of collagen fibers in rows
• Locations
• Intervertebral disks
• Pubic symphysis
• Menisci

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Cartilage Growth

• Appositional growth
• From perichondrium
• Interstitial growth
• By chondrocytes within cartilage
• No new chondrocytes in adults and no cartilage
  growth

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Bone Functions

• Support body weight
• Protect soft organs
• Movement at joints
• Storage of Ca and PO4-3
• Hematopoiesis

(6.2)
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Bone Shapes

• Long bones extremities
• Short bones cube-shaped, wrist ankle
• Flat bones skull, sternum, scapula, ribs
• Irregular bones vertebrae, pelvis

(6.2)
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Compact vs. Spongy Bone

• Compact solid, weight-bearing, structural
  support
• Spongy marrow cavity, trabeculae, light weight

(6.3ab)
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Compact vs. Spongy Bone
Medullary cavity
See Fig. 6.5b
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Long Bones

• Diaphysis shaft
• Epiphyses ends
• Epiphyseal plate/line growth region
• Nutrient arteries to marrow and compact bone

(6.3ac)
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Periosteum

• Fibrous layer dense irregular CT
• Cellular layer osteoblasts osteoclasts
• Nerves
• Blood vessels
• Sharpeys fibers
• Attachment for tendons

(6.3c)
(6.6a)
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Endosteum

• Inner surface of compact bone
• Covers trabeculae
• Osteoblasts osteoclasts

(6.3b)
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Flat Bone

• Skull
• Two sheets of compact bone
• Diploe spongy bone

(6.4)
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Compact Bone Histology
(6.7)

• Osteon / Haversian system
• Structural unit of long bone
• Cylindrical
• Parallel to bone
• Concentric lamellae
• Collagen fibers in different directions
• Increase strength

(6.6a)
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Compact Bone Histology

• Interstitial lamellae
• Circumferential lamellae
• Inner outer

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Compact Bone Histology

• Central / Haversian Canals
• Perforating / Volkmanns Canals
• Endosteum
• Blood vessels
• Nerves

(6.6a)
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Osteocytes
4.12j

• Located within lacunae (cavities) in lamellae
• Canaliculi allow processes of osteocytes to
  communicate with each other with capillaries

(6.6b)
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Spongy Bone

• Lamellae
• Osteocytes
• Endosteum

(6.3b)
See 6.8b
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Bone Composition

• 35 cells, fibers (collagen), ground substance
• 65 mineral salts, mainly calcium phosphate
  precipitated around collagen fibers

See 6.8b
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Bone Formation

• Osteogenesis development of the skeleton and
  growth through adolescence (18 females, 21
  males)
• Osteoblasts secrete osteoid
• Osteoid is mineralized (calcium phosphate
  precipitates)
• Osteoblasts become osteocytes
• Forms woven bone (immature)
• Periosteum formed
• Mature lamellar bone formed on surfaces

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Intramembranous Ossification

• Flat bone develops from mesenchyme
  (undifferentiated, embryonic CT)
• Skull and clavicle
• Mesenchymal cells become osteoblasts
• Osteoblasts form bone

(6.9)
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Endochondral ossification

• Hyaline cartilage model of bone first
• Cartilage is replaced by bone(long bone)

(6.10)
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Bone Growth

• Regulated by
• Growth hormone
• Thyroid hormone
• Sex hormones

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Abnormal Bone Growth

• Hyperpituitarism. Gigantism.  F/19.  Family
  photographs showed that this young woman had
  consistently outgrown her twin brother and was
  always the biggest child in the school class. 
  She had a pituitary adenoma secreting growth
  hormone.

http//www.anatpath.com/resource/educationalaids/c
olouratlas/ENDOCRINE20SYSTEM.htm
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Bone Remodeling
(6.6)

• Dynamic changing throughout life
• Osteoblasts form new bone
• Osteoclasts
• multinucleated, fused cells
• Secrete HCl, dissolve calcium phosphate
• Lysosomal enzymes digest collagen matrix
• Phagocytize debris

(6.13)
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Mechanical Stress

• Bone tissue thickens in response to stress, e.g.,
  exercise / weight gain
• Bone tissue thins in response to decreased
  exercise or weightlessness

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Osteoporosis

• Bone resorption gt bone deposition
• Bone mass
• Fractures
• Related to
• Estrogen after menopause
• Exercise
• Calcium and protein in diet
• Treatment
• Calcium and exercise
• vitamin D

See 6.15
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Normal Osteoporosis
http//www.umassmemorial.org/ummhc/hospitals/med_c
enter/services/osteoporosis/index.cfm
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Development of Skeleton
Bone tissue is stained red. Note development of
the skull (suture lines), rib cage, and
extremities. See class demonstration.