Skeletal System Flashcards
(36 cards)
Skeletal functions
- Protection
- Mineral storage and acid-base homeostasis
- Blood cell formation
- Fat storage
- Movement
- Support
5 main groups of bone classification and their structural function
- Long bone: transmits force
- Short bone: support, stability, limits movement
- Flat bone: protective
- Irregular bone: varied
- Sesamoid bone: protect tendons
Bone structure
Compact bone -
Outer surface of bones; solid; resists compression and twisting
Spongy bone –
Honeycombed by trabeculae; lightweight; provides strength to forces in all directions; spaces contain bone marrow
Major anatomical structures that make up the bone
Epiphyses:
- Ends, head and tail of the bone
- Covered by hyaline cartilage
Diaphysis:
- Bone shaft
- Contains the medullary cavity
- Weight bearing
- Bone marrow; nutrient supply
Epiphyseal line:
- Growth plate
Periosteum:
- The skin of the bone
- Lies on all surfaces of the bone except cartilage
- Connective tissue rich in blood and nerve fibres
Endosteum:
- Separates the bone structure from the bone cavity
- Thin membrane lining the medullary cavity
Short, flat, irregular and sesamoid bones
- Do NOT have diaphyses, epiphyses, medullary cavities, epiphyseal lines, or epiphyseal plates
- Covered by periosteum, with perforating fibers, blood vessels & nerves, like long bones
- Structure: 2 outer layers of thin compact bone & a middle layer of spongy bone, called diploë, & its bone marrow
- Some flat & irregular skull bones have hollow spaces -such as sinuses - reduce bone weight
Primary tissue found in bone
Osseous tissue
- Composed mostly of extracellular matrix
- ECM defines connective tissues
- Bone itself is a connective tissue
ECM of the bone
Inorganic matrix (structure)
- Consists of minerals that make up about 65% of bones total weight
- 55% crystalised Ca mineral salts = Hardness
Organic matrix
- Makes up remaining 35%
- Consists of collagen fibers and usual ECM components
- 15% water, 30% collagen + other proteins
- Provide tensile strength & flexibility
What happens to bone properties when the ECM composition is altered?
- Remove organic matrix = brittle bones that shatter easily
- Remove inorganic matric = cannot resist compression and can bend easily
Bone cells
Osteoblasts
- Builds bone
- Mainly in peri- & endosteum
Osteocytes
- Maintains bone structure and bone integrity
- Mature bone cells
- In compact & spongy bone
Osteoclasts
- Breaks down bone
- Resorb/remodel bones
- Mainly in endosteum
Where are osteocytes located?
Lacunae
What connects lacunae?
Canaliculi
The lacunae and canaliculi form rings around the central canal called?
Lamellae
The central canal is also called?
The Haversian canal
What is an osteon?
Lamellae + canal
What is the function of the following?
- Lacunae
- Canaliculi
- Lamellae
- Haversian/central canal
- Osteon
- Lacunae = provides a habitat for bone cells - osteocytes
- Canaliculi = links lacunae, ‘canals’/minute spaces that contain bone cells
- Lamellae = the concentric circles around the Haversian canal
- Haversian/central canal = tubes in bone that house nerve fibers and a few capillaries (tiny blood vessels)
- Osteon = cylindrical structures that contain a mineral matrix and living osteocytes connected by canaliculi, which transport blood
How does bone form?
Ossification (osteogenesis) is the process of bone formation
What are the 2 types of ossification?
Intramembranous
- The process of bone development from fibrous membranes
- Flat bones e.g. skull
- Connective tissue is replaced by bone
Endochondral
- The process of bone development from hyaline cartilage
- Typically in long bones, cartilage turns to bone
- Hyaline cartilage converts to bone (chondrocytes become osteoblasts)
How does bone grow?
- Epiphyseal (growth) plate is cartilage that continues to divide pushing the epiphysis away from the diaphysis, resulting in longitudinal growth
- The cartilage in the region of the epiphyseal plate next to the epiphysis continues to grow by mitosis.
- The chondrocytes, in the region next to the diaphysis, age and degenerate.
What happens at 25 years of age in relation to bone growth?
The growth plate stops & becomes epiphyseal line
What type of growth is the increasing width of bone?
Appositional growth
What is the difference between bone growth and bone remodelling?
Bone growth = lengthening of the bones
Bone remodeling = changes to the shape, width and breadth of the bone
What factors affect bone growth and remodelling?
- Hormones
- Vitamins
- Minerals
What hormones affect bone growth and remodelling?
Parathyroid hormone
- Determines when/if bone is resorbed (in response to blood Ca levels); under homeostatic control
Thyroid hormone
- Stimulates osteoblasts
Growth hormone
Testosterone & estrogen
- ↑ appositional growth (thicker bones)
- ↑ longitudinal growth & inhibits osteoclasts
- Growth spurts (↑ mitosis of epiphyseal plate & closure of epiphyseal plate
What vitamins affect bone growth and remodelling?
- A stimulates osteoblasts
- C collagen synthesis
- D builds bone by absorbing calcium from food
- K & B12 for other bone proteins
