2. Skeletal System Flashcards
Supine
Lying face up
Prone
Lying face down
Medial
Nearer to the midline
Lateral
Away from the midline
Bilateral
Both sides
Unilateral
One side
Ipsilateral
On the same side
Contralateral
On the opposite side
Proximal
Nearer to the trunk
Distal
Further from the trunk
Anterior ( ventral)
Nearer the front
Posterior (dorsal)
Nearer the back
Superior
Towards the top
Inferior
Towards the bottom
Coronal / frontal plane
Separating the front and back
Sagittal plane
Separating the left and right
Horizontal / transverse plane
Separating the top and bottom
How many bones in the human body?
206
What percentage of body weight is the skeleton?
18%
Functions of the skeleton
• Support framework for the body. • Forms boundaries(skull). • Attachment for muscles and tendons. • Permits movement(joints). • Haematopoiesis-formation and development of blood cells from the red bone marrow. • Mineral homeostasis (mostly calcium & phosphate). •Triglyceride storage(yellow bone marrow).
Bones Cells
- Osteogenic cells: 2. Osteoblasts: 3. Osteocytes: 4. Osteoclasts:
Osteogenic Cells
Bone stem cells. They are the only bone cell to undergo division (producing osteoblasts).
Osteoblasts
•These are bone building cells. •They synthesise and secrete collagen and other components of bony matrix. •They are trapped and become osteocytes.
Osteocytes
•Osteocytes are mature bone cells.They maintain the daily metabolism of bone, such as nutrient exchange.
Osteoblasts
•Osteoclasts are huge cellsderived from the fusion of as many as 50 monocytes (WBCs). •On the side facing the bone surface, the cell membrane is folded into a ‘ruffled border’,where the cell releases powerful lysosomal enzymes and acidsthat digest bone matrix. •‘Resorption’ is the breakdown of bone matrix. •Osteoblast and osteoclasts work together to ‘remodel’ bone throughout life. Excess osteoclast activity leads to a loss of bone density.
Types of Bone
Compact Spongy
Compact Bone
80% of the skeleton Contains few spaces and is strong Found beneath the periosteum and makes up most of the diaphysis (shaft) of the long bones Structural unit of compact bone is an ‘osteon’ (aligned along stress lines)
Four parts of an Osteon
- Haversian Canal 2. Lamallae 3. Canaliculi 4. Lacunae
Haversian Canal
Contains blood vessels ad nerves
Lamallae
Concentric rings of extracellular matrix containing minerals and collagen
Canaliculi
A mini system of interconnected canals that provide a route for nutrients/waste
Lacunae
Small spaces containing osteocytes
Spongy Bone
Spongy bone does not contain osteons. Instead it consists of an irregular lattice of thin columns called trabeculae that are aligned along stress lines. Microscopic spaces between trabeculae make bones lighter and contain bone marrow. Spongy bone makes up the interior of short, flat and irregularly shaped bones and the end of long bones. Spongy bone is always covered with compact bone.
Bone Matrix
An extracelluar matrix which surrounds separated cells made up of collagen and minerals (calcium phosphate as well as magnesium, sulphate and potassium).