Development and growth of human skeleton Flashcards
Discuss skeletal system structure
Axial- Skull, vertebrae, ribs, sternum, hyoid bone
Appendicular- limb bones and bones of pectoral and pelvic girdle
Discuss system function
Range of functions including: Protection of organs Supports the body Movement Production of new red blood cells Metabolic reservoir
Discuss cartilage
Connective tissue
Forms the skeleton in parts where flexibility is required
Avascular
Proportions of bone to cartilage change as the individual develops.
Discuss bone
Hard form of connective tissue
Provides a ridged framework
Vascular
Two types of bone: compact and spongy
Discuss the covering
A connective tissue element covers the skeletal system.
Except where an articulation occurs
The connective tissue surrounding bone is called the periosteum
The connective tissue surrounding cartilage is called the perichondrium
Discuss the microanatomy of bone
Bone is comprised of 4 cell types: Osteoprogenitor cells Osteoblasts Osteocytes Osteoclasts
Bone is constantly remodelled as a result of activity between osteoclasts and osteoblasts
Discuss compact bone
Compact bone is covered by the periosteum
Lamella (concentric layers of inorganic matrix) is laid down by osteoblasts
Lamella form the haversian canal in the centre
Haversian canal contains vascular and nerve supply
Osteoblasts become trapped and turn into osteocytes
Each osteocyte occupies its own lacunae
Radiating from each lacunae are minute canals (canaliculi)
Nutrients travel in the canaliculi to the osteocyte
Describe spongy bone
Spongy bone also known as cancellous bone
Irregular lamellae
Has red bone marrow surrounding it
Highly vascular
What are the five classifications of bone
Long bones Flat bones Irregular bones Short bones Sesamoid bones
Describe bone development
Bone development begins at week 8 and finishes at 20 years
Bone is derived from mesoderm
Specifically paraxial and lateral plate mesoderm
Ossification can occur in two ways:
Intramembranous
Endochondral
Discuss Intramembranous Ossification
Direct mineralisation of connective tissue (mesenchyme)
Cells divide and condense around capillary network
Starting point is called primary ossification center
Grows radially, finally fusing together replacing the connective tissue
Connective tissue that remains penetrated by blood cells and undifferentiated mesenchyme gives rise to bone marrow.
Examples include the skull, mandible and clavicle
Discuss Endochondral Ossification
Cartilaginous template made from the mesenchyme
Template is replace by bone- osteogenesis
Different ossification centres emerge, a primary one in the diaphysis and secondary ones in the epiphysis
Initially a bone collar is produced and from here the primary centre develops
The epiphyseal plate (Growth Plate) exists between the diaphysis and the epiphysis
Discuss bone growth
Bone growth is associated with partial reabsorption of previously laid down bone and the laying down of new bone.
Long bones gradually lengthen as ossification continues
Developing bone is penetrated by blood vessels at week 9
With maturity the epiphyseal plate is abolished
Discuss bone development and maintenance
Bone maintenance is regulated by a dietary intake of calcium, phosphorous, vitamins, A, C and D
Vitamin A is essential for bone remodelling
Vitamin C is essential for connective tissue
Vitamin D is essential for calcium absorption
Bone development is controlled by endocrine activity.
Parathyroid hormone- hyperparathyroidism
Growth hormone- Dwarfism , Acromegaly
