Skeletal System Flashcards
What are the major organs of the skeletal system?
Bones, cartilage, ligaments
What are the functions of the skeletal system?
- Provide support and protection for other tissues
- Store calcium and other minerals
- Blood cell production
Describe the composition of bone
Bone Matrix -Consists of extracellular protein fibres, ground substance (fluid), and inorganic compounds (e.g. calcium) Bone Cells -Osteocytes -Osteoblasts -Osteoclasts -Osteogenic
What is an osteocyte?
Mature bone cell that maintains bone matrix
What is an osteoblast?
Immature bone cell that produces new bone matrix in a process called ‘ossification’
What is an osteoclast?
Absorb and remove bone matrix
What is osteogenic?
Stem cells that ultimately become osteoblasts
Describe an osteon
- Mature compact bone
- Consists of venule, canaliculi, central canal, capillary, lacunae and lamellae
What is a venule?
- Transport blood to heart
- Small blood vessel
What is the canaliculi?
Narrow passageway that permits transport of nutrients/wastes
Describe the central canal?
Contains blood vessels that carry blood to and from osteon
What is a capillary?
Small blood vessel that transport blood to osteon
What is the lacunae?
Mature bone cell that maintains bone matrix
What is the lamellae?
Layers of bone matrix and collagen that add strength and resiliency
What is the structure of spongy bone?
- Bone marrow
- Trabeculae
Describe bone marrow
- Within epiphyses of long bones & large bones
- Red bone marrow (blood cell production) is present between trabeculae
- Yellow bone marrow (adipose tissue-energy reserve) present at other sites
Describe the trabeculae
- Meshwork of supporting bundles of fibres in the matrix of spongy bone
- Nutrients reach osteocytes by diffusion along canaliculi
Describe periosteum
- Membrane that covers superficial layer of compact bone
- Isolates bone from surrounding tissues
- Involved in bone growth & repair
Describe endosteum
-Thin layer of osteogenic cells, osteoblasts, and osteoclasts -Covers trabeculae of spongy bone and lines the medullary cavity -Bone growth, repair, and remodelling
Describe endochondral ossification
- Chondrocytes in hyaline cartilage calcify and die
- Cells of perichondrium turn into osteoblasts
- Formation of periosteum
- Osteoblasts form compact and spongy bone
- Osteoclasts remodel bone
- Some cartilage remains exposed to joint cavity as articular cartilage
Describe intramembranous ossification
- Occurs in clavicles, mandible, and flat bones of skull
- Begins when osteoblasts differentiate within mesenchymal or fibrous connective tissue
Can you briefly describe the effect of exercise on bone growth and maintenance?
Increased physical activity
Increased applied force (stress) to bones
Increased bone production by osteoblasts
Decreased physical activity & weightless environment
Decreased applied force (stress) to bone
Bone loss
Describe what occurs when blood calcium ion levels increase
-Low calcium ion level in blood
-Parathyroid gland secretes parathyroid hormone
Bone response: osteoclasts stimulated to release stored calcium ions from bone- calcium released
-Kidney response: kidneys absorb calcium ions, more calcitriol- calcium conserved, decreased calcium loss in urine
-Intestinal response: intestinal absorption of calcium increases- calcium absorbed
Describe what occurs when blood calcium ion levels decrease
- High calcium ion level in blood
- Thyroid gland secretes calcitonin
- Bone response: osteoclast activity decreases, osteoblast activity unaffected- calcium release slowed
- Kidney response: kidneys excrete less calcium ions, less calcitriol- calcium excreted, increased calcium loss in urine
- Intestinal response: intestinal absorption of calcium decreases- calcium absorbed slowly
