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Lecture

BIOB32H3 Lecture Notes - Central Canal, Endosteum, Long Bone


Department
Biological Sciences
Course Code
BIOB32H3
Professor
Kenneth Welch

Page:
of 3
Osseous Tissue and Skeletal Structure
The Skeletal System: An Introduction
The skeletal system includes
Bones of the skeleton
Cartilages, ligaments and other connective tissues that stabilize and connect
Functions of the skeletal system
Support
Storage of minerals and lipids
Blood cell production
Protection
Leverage
A Classification of Bones
Bone shapes
Long
Flat
Short
Irregular
Sesamoid
Sutural
Bone structure = two types of bone
Compact bone (dense)
Spongy bone (cancellous)
A typical long bone includes
Diaphysis
Epiphyses
Metaphysis
Articular cartilage
Marrow cavity
Filled with red or yellow marrow
Bone Histology
Osseous tissue
Supporting tissue with a solid matrix
Crystals of hydroxyapatite
Minerals deposited in lamellae
Covered by periosteum
Cells in bone:
Osteocytes = mature bone cells
In lacunae
Connected by canaliculi
Osteoblasts synthesize new matrix
Osteogenesis
Osteoclasts dissolve bone matrix
Osteolysis
Osteoprogenitor cells differentiate into osteoblasts
Compact bone and spongy bone
Basic unit of compact bone is an osteon
Osteocytes arranged around a central canal
Perforating canals extend between adjacent osteons
Spongy bone contains trabeculae
Bones and stress
Compact bone located where stresses are limited in direction
Spongy bone located where stresses are weaker or multi-directional
Bones are:
Covered by periosteum
Lined by endosteum
Bone development and growth
Ossification = converting other tissue to bone
Calcification = depositing calcium salts within tissues
Osseous Tissue and Skeletal Structure
Intramembranous ossification
Begins with osteoblast differentiation
Dermal bones produced
Begins at ossification center
Figure 6.7 Intramembranous Ossification
Endochondral ossification
Cartilage model gradually replaced by bone at metaphysis
Increasing bone length
Timing of epiphyseal closure differs
Appositional growth increases bone diameter
Osseous Tissue and Skeletal Structure
The Dynamic Nature of Bone
continually changing
Remodeling
Exercise
Hormone levels
Growth hormone and thyroxine increase bone mass
Calcitonin and PTH control blood calcium levels
The skeleton is a calcium reserve
99% body’s calcium in the skeleton
Calcium ion concentration maintained by bones GI tract and kidneys
Calcitonin and PTH regulate blood calcium levels
Calcitonin decreases blood calcium levels
PTH increases blood calcium levels
Fracture repair
Fracture hematoma
External callus
Internal callus
Bone Markings (Surface Features)
Bone markings
Are characteristic for each bone and each individual
Markings include
Elevations
Projections
Depressions
Grooves and tunnels
Aging and the Skeletal System
Effects of aging include
Osteopenia
Osteoporosis