Bones and Bone Structure Flashcards
Skeletal system
Bones, cartilages, ligaments and connective tissues
Functions of the skeletal system
- Support
- Mineral and lipid storage
- Blood cell production
- Protection
- Leverage
Sutural bones
Small, flat bones found between flat bones of skull
Irregular bones
Complex shapes that form spinal columns, bones of pelvis, several bones in skull
Short bones
Boxlike e.g. carpal and tarsal bones
Flat bones
Thin, parallel surface that protect soft tissue
Long bones
Long, slender bones like arm, forearms and thighs
Sesamoid bones
Small, round, flat e.g. patella
Projections
Where muscles, tendons, and ligaments attach and where adjacent bones form joints
Openings and depressions
Where blood vessels or nerves lie alongside or penetrate the bone
Diaphysis
Extender tubular shaft of long bone made of compact bone
Epiphysis
Expanded area at the ends of long bones made of spongy bone
Metaphysis
Narrow zone joining diaphysis and epiphysis
Medullary cavity
Central space in long bone
Spongy bone
Consists of an open network of struts and plates
Compact bone
Dense and solid bone
Bone tissue
Supporting connective tissue
Why is the bone matrix very dense?
Due to deposits of calcium salts around the protein fibres
Where are osteocytes found?
In pockets called lacunae in the bone matrix
Canaliculi
Narrow passageways through the bone matrix
Periosteum
Covers the outer surfaces of the bone except at joints
What makes up almost two-thirds of the weight of bone?
Calcium phosphate
Hydroxyapatite
Crystals formed from calcium phophate and calcium hydroxide
Calcium phosphate
Hard but inflexible and brittle crystals
Collagen fibres
Stronger than calcium phosphate and also flexible
Osteogenic cells
Stem cells whose divisions produce osteoblasts
Where are osteogenic cells found?
Inner, cellular layer of the periosteum
Which bone cells are important in repair of fractures?
Osteogenic cells
Endosteum
Lines medullary cavities and passageways for blood vessels that penetrate the matrix of compact bone
Osteoblasts
Produce new bone matrix through osteogenesis by making proteins and other organic components of the matrix
Osteoid
The organic bone matrix made by osteoblasts before calcium salts are deposited
Osteocytes
Mature bone cells that make up most of the cell population
Lacuna
Pockets sandwiched between layers of matrix
Each osteocyte occupies a lacuna
Can osteocytes divide?
No
How do osteocytes exchange nutrients and hormones?
Gap junctions
Functions of osteocytes
- Maintain protein and mineral content of the surrounding matrix
- Take part in the repair of damaged bone
Osteoclasts
Absorb and remove bone matrix
Where are osteoclasts found?
Osteoclastic crypts
Osteolysis
The erosion process of the bone matrix
Function of compact bone
To protect, support, and resist stress
Function of spongy bone
Provides some support and stores marrow
Osteon
Basic functional unit of mature compact bone
Central canal
Contains one or more blood vessels that carry blood to and from the osteon
They run parallel to the surface of the bone
Perforating canals
Extend perpendicular to the surface containing blood vessels that supply blood both to osteons deeper in the bone and to tissues of the medullary cavity
Lamellae
Bone matrix layers
When is compact bone thickest?
When stresses are applied from a limited number of directions (all osteons in compact bone are aligned the same)
Are osteons present in spongy bone?
No
Trabeculae
- A meshwork of supporting bundles of fibres formed by the matrix in spongy bone
- Supports and protects bone marrow
Where is spongy bone found?
Where bones are not heavily stressed or where stresses originate from many directions
Are there capillaries or venules in the matrix of spongy bone?
No
Where is red bone marrow found?
Spongy bone within the epiphyses of long bones
Yellow bone marrow
Stores adipose tissue
Composition of the periosteum
Fibrous outer layer and inner cellular layer
2 surface coverings of the bone
Periosteum (outer) and endosteum (inner)
Ossification
The physical process of bone formation and bone growth
Calcification
Deposition of calcium salts during ossification
Calcified tissue
Results from calcification taking place in tissues other than the bone
Endochondral ossification
Bone replaces existing cartilage and then bone growth occurs through interstitial growth (in length) and appositional growth (in width)
Intramembranous ossification
Bone develops directly from mesenchyme or fibrous connective tissue
Where does endochondral ossification mostly occur?
In long bones
Where does intramembranous ossification mostly occur?
In flat bones
3 major sets of blood vessels in typical bones
- Nutrient artery and vein
- Metaphyseal vessel
- Perisoteal vessel
Hormones
Calcitriol/calcitonin - calcium and phosphate ion absorption
Growth hormone, thyroxine, sex hormones, parathyroid hormones - stimulate osteoblasts
Calcium and neurons/mucle cells
Calcium ions increase by 30% - unresponsive
Calcium ions decrease by 35% - overexcitable
2 hormones that maintain calcium ion homeostasis
Parathyroid hormone and calcitonin
Parathyroid hormone
Increases blood calcium ion levels
Calcitonin
Reduces osteoclast activity, decreasing blood calcium ion levels
2 types of fractures
Open (compound): project through the skin
Closed (simple): completely internal
Repair of a fracture
- Fracture hematoma formation
- Callus formation
- Spongy bone formation
- Compact bone formation
Osteopenia
Inadequate ossification that happens with ageing
Osteoporosis
When the reduction in bone mass is sufficient to compromise normal function
Osteoclast-activating factor
A chemical released by by cancers of the bone marrow, breast, or other tissues producing severe osteoporosis
