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Chapter 6 Bones
Bones and Skeletal Tissue
| Question | Answer |
|---|---|
| What are the three types of skeletal cartilage? | hyaline, elastic, and fibrocartilage |
| What surrounds skeletal cartilage? | Perichondrium |
| What are the characteristics of hyaline cartilage? | It provides support, flexibility, and resilience, is most adundant skeletal carilage, and is present in aricular, coastal, respiratory, and nasal cartilages |
| What is the difference between hyaline and elastic cartilage? | Elastic contains elastic fiber |
| What are characteristics of fibrocartilage? | highly compressed with great tensil strength, contains collagen fibers, and found in the menisci of the knee and in intervertebral discs |
| Explain the appositional and interstitial growth of cartilage. | Appositional- cells in the perichondrium secrete matrix against the external face of existing cartilage Interstitial- lacunae-bound chondrocytes inside the cartilage divide and secrete new matrix, expanding the cartilage from within |
| Explain the axial and appendicular skeleton | Axial- bones of the skull, vertebral column, and rib cage Appendicular- bones of the upper and lower limbs, shoulder, and hip |
| What are the classifications of bones by shape? | Long- e.g. humerus Short- e.g patella Flat- e.g. sternum and skull bones Irregular- vertebrae and hip bones |
| What are the main functions of bones? | Support- form the framework supporting the body Protection- protective case for brain, spinal cord, and vital organs Movement Mineral storage- reservoir for minerals, like calcium and phosphorus Blood cell formation- hematopoiesis in marrow cavities |
| What are the characteristics of the long bone? | Consists of diaphysis (forms axis) and epiphysis (expanded end) |
| What is periosteum? | double-layered protective membrane Outer layer is dense regular, inner osteogenic layer is osteoblasts and osteoclasts, supplied with nerve fibers, blood, and vessels Secured by Sharpey's fibers |
| What is endosteum? | membrane covering internal surfaces of bone |
| Which bones have thin plates of periosteum-covered compact bone on the outside with endosteum-covered spongy bone (dipoloe) on the inside? | Short, irregular, and flat bones |
| Where is red marrow found in infants? | in the medullary cavity and all areas of spongy bone |
| Where is red marrow found in adults? | in the diploe of flat bones, and the head of the femur and humerus |
| What makes up the Haversian system (osteon) | Lamella (column-like matrix of mainly collagen), Haversian/central canal (channel containing blood vessels and nervesVolkmann's canals (lying @ right angles to the central canal, connecting blood and nerve supply of the periosteum to Haversian canal) |
| What is 65% of bone by mass, mainly calcium phosphates, and responsible for bone hardness & resilience? | Hydroxyapatites, or mineral salts |
| Define osteogenesis and ossification | Bone tissue formation, leading to formation of bony skeleton in embryos. Bone growth until early adulthood Bone thickness, remodeling, and repair |
| What are the three functional zones in long bone growth? | Growth Zone- Cartilage cells undergo mitosis, pushing epiphysis away from diaphysis Transformation zone- old cells enlarge, matrix becomes calcified, cartilage cells die, and matrix deteriorates Osteogenic zone- new bone formation occurs |
| What is essential for mineralization of bone? | Alkaline phosphatase |
| Sites of new matrix desposition are revealed by what? | Osteoid seam- unmineralized band of bone matrix Calcification front- abrupt transition zone between the osteoid seam and the older mineralized bone |
| What are resorption bays? | grooves formed by osteoclasts as they break down bone matrix |
| Resorption involves osteoclast secretion of what? | Lysosomal enzymes that digest organic matrix Acids that convert calcium salts into soluble forms |
| What is calcium necessary for? | transmission of nerve impulses, muscle contraction, blood coagulation, secretion by glands and nerve cells, and cell division |
| What two control loops regulate bone remodeling? | Hormonal mechanism maintains calcium homeostasis in the blood Mechanical and gravitational forces acting on the skeleton |
| What triggers the thyroid to release calcitonin? | Rising blood Ca^2+ levels |
| What signals the parathyroid glands to release PTH? | Falling blook Ca^2+ levels |
| WHat stimulates calcium salt deposit in bone? | Calcitonin |
| What does PTH do? | Signals osteoclasts to degrade bone matrix and release Ca^2+ in the blood |
| Define Wolff's law and give supporting observations. | Law- a bone grows or remodels in repsonse to the forces or demands placed upon it Observations- Long bones are thickest midway along the shaft, and curved bones are thickest where they are most likely to buckle |
| What are bone fractures classified by? | The position of the bone ends after fracture The completeness of the break The orientation of the bone to the long axis Whether or not the bone ends penetrate the skin |
| What is the first stage in the healing of a bone fracture? | Hematoma formation |
| Explain hematoma formation. | Torn blood vessels hemorrhage, a mass of clotted blood forms at the fracture site, and site becomes swollen, painful, and inflamed |
| What is the second stage in bone fracture? | Fibrocartilaginous callus formation |
| Explain fibrocartilaginous callus formation | granulation tissue (soft callus) forms a few days after fracture, and capillaries grow into the tissue and phagocytic cells begin cleaning debris |
| How does fibrocartilaginous callus form? | Osteoblasts & fibroblasts migrate to fracture & begin reconstructing the bone, fibroblasts secrete collagen fibers to connect broken bone ends, osteoblasts form spongy bone, & osteoblasts furthest from capillaries secrete cartilaginous matrix |
| What is the third stage in the healing of a bone fracture? | Bony callus formation |
| Explain bony callus formation. | New bone trabeculae appear in the fibrocartilaginous callus, fibrocartilaginous callus converts into a bony callus, and bone callus begins 3-4 weeks after injury and continues until firm union is formed 2-3 months later |
| What is the fourth stage in the healing of a bone fracture? | Bone remodeling |
| Explain bone remodeling. | Excess material on the bone shaft exterior and in the medullary canal are removed, and compact bone is laid down to reconstruct shaft walls |
| What is osteomalacia? | Softening of bones due to inadequate mineralization. Causes pain when weight is put on bone, and is caused by insufficient calcium in the diet, or by Vitamin D deficiency |
| What is rickets? | Inadequately mineralized bones of children causing softened bones. Bowed legs and deformities of the pelvis, skull, and rib cage. Caused by Vitamin D deficiency or insufficient calcium. |
| What is Paget's Disease? | Excessive bone formation and breakdown, high ratio of woven to compact bone is formed, causes spotty weakening of bone, osteoclast activity wanes, but osteoblast activity continues to work |
| What occurs when mesoderm gives rise to embryonic mesenchymal cells? | Produces membranes and cartilages that form the embryonic skeleton |
| What can be used to determine embryonic skeleton ossification? | Sonograms |
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