Lecture 3 Flashcards
Types of cartilage (3)
- Hyaline
- Elastic
- Fibrocartilages
Perichondrium
Surrounds cartilages
Resists outward pressure (adds strength)
Functions in growth and repair
Cartilage
Connective tissue
Consists primarily of water
Resilient tissue: can return to original form
Chondrocyte
Cartilage cell type
Exists inside lacunae
Lacunae
Cavity within cartilage matrix
House chondrocytes
Cartilage matrix
Contains fibers and jellylike ground substance
Hyaline cartilage
"glass": translucent Most abundant Chondrocytes appear spherical Collagen fibers in matrix Ground substance holds large amount of water Provides support through flexibility
Elastic cartilage
Contains many elastic fibers
Yellowish in colour
Able to tolerate repeated bending
Located in epiglottis and external ear
Fibrocartilage
No perichondrium
Resists strong compression and strong tension
Intermediate between hyaline and elastic
Located in pubis symphysis, mensici of knee, annulus fibrosus
Growth of cartilage (2)
- Appositional growth
- Interstitial growth
Cartilage stops growing when the skeleton stops growing
Functions of bones (5)
- Support/protection
- Movement
- Mineral storage
- Blood formation
- Energy metabolism (osteoblasts secrete osteocalcin)
Osteocalcin
Secreted by osteoclasts
Thought to due with body homeostasis
Bone tissue make up (2)
- 35% organic components
2. 65% inorganic components
Organic components
Cells, fibers, ground substance
Contribute to flexibility and tensile strength
Inorganic components
Mineral salts that invade bony matrix
Provide exceptional hardness, resist compress
Cells that produce or maintain bone (3)
- Osteogenic cells
- Osteoblasts
- Osteocytes
Osteogenic cells
Stem cells that differentiate into osteoblasts
Osteoblasts
Actively produce and secrete bone matrix
Osteoid
Bone matrix
Osteocytes
Keep bone matrix healthy
Osteoclasts
Found within bone tissue
Crawls along bone surface
Giant cell with many nuclei
Responsible for reabsorption of bone
Derived from line of hematopoietic stem cell
Secrete hydrochloric acid and lysosomal enzymes
Compact bone
Dense outer layer Contains passage ways for blood vessels, lymph vessels and nerves Osteons Osteocytes sandwiched between lamellae Volkmann's canals
Spongy bone
Cancellous
INternal network of bone
Trabeculae: little beams of bone
Open spaces between trabeculae are filled with marrow
Endosteum
Inner lining inside bone
Epiphyses
Ends of long bone
Bone design and stress
Anatomy of bone reflects stresses
Compression and tension are greatest at external surfaces
Centre of bone does not have any force
Structure of typical long bone (5)
- Diaphysis: shaft
- Epiphyses - ends of bone
- Blood vessels
- Medullary cavity
- Membranes
Diaphysis
Shaft of long bone
Medullary cavity
Hollow cavity filled with yellow marrow
Membranes of long bone (3)
- Periosteum
- Perforating collagen fiber bundles (Sharpey’s fibers)
- Endosteum
Diploe
Internal spongy bone of flat bones
Osteons
Present in compact bone
Contain lamellae, central canal, perforating canals and canaliculi
Long cylindrical structures
Function in support
Structurally resemble rings of a tree in cross section
Volkmann’s canals
Perforating canals
Allow passage of nutrients and cell communications between Haversian systems
Ossification/osteogenesis
Bone formation
Intramembranous ossification
Membrane bones
Formed directly from mesenchyme
Endochondral ossification
All bones except some bones of skull and clavicles
Bones are modeled in hyaline cartlage
Begins forming late in the second month of embryonic development
Continues forming until early adulthood
Ephiphyseal plates
Cartilage organized for quick, efficient growth
Cartilage cells form tall stacks
Chondroblasts at top of stacks divide quickly
Pushes epiphysis away from piaphysis
Lengthens entire long bone
Older chondrocytes
Bone elongation
Signal surrounding matrix to calcify
Die and disintegrate, leaving long trabeculae of calcified cartilage on diaphysis side
Trabeculae are partly eroded by osteoclasts, which are then covered by bone tissue by osteoblasts
Trabeculae are eaten away from their tips by osteoclasts
Postnatal growth of endochondral bones
During childhood and adolescence
Bones lengthen entirely by growth of epiphyseal plates
Cartilage is replaced with bone connective tissue as quickly as it grows
Epiphyseal plate maintains constant thickness
Whole bone lengthens
Hormonal regulation of bone growth (3)
- Growth hormone
- Thyroid hormone
- Sex hormones
Growth hormone
Produced by the pituitary gland
Stimulates epiphyseal plates
Thyroid hormone
Ensures that the skeleton retains proper proportions
Sex hormones
Estrogen and progesterone
Promote bone growth
Lated induces closure of epiphyseal plates
Bone remodelling
Bone is dynamic living tissue
500mg of Ca may leave or enter skeleton each day
Bone matrix + osteocytes are continually removed by reabsorption and replaced by bone deposition by osteoblasts
Cancellous bone is replaced every 3-4 years, compact bone is replaced every 10 years
Osteoporosis
Characterized by low bone mass
Bone reabsportion outpaces bone deposition
Occurs most often in women after menopause
Osteomalacia
Occurs in adults
Bones are inadequately mineralized
Rickets
Occurs in children
Analogous to osteomalacia
Osteosarcoma
Form of bone cancer
Skeleton throughout life
Stops growing from 18-21
Bone mass declines with age
