Summary of Functions
- Support - posture
- Movement - as attachment points for muscle
- Protection - of soft tissue
- Storage - of both minerals and fat
- Hematopoiesis - production of RBCs, WBCs, and PLTs
As a characteristic of CT, bone is composed of
- cells and abundant matrix
- Bone tissue on the whole is innervated, contains lymphatics, and is highly vascular
Bone Matrix includes:
- protein scaffolding (mostly collagen) arranged in alternating layers (at 90 degrees to one another),
- deposited minerals (mostly Ca, P in the form of hydroxyapatite),
- cells referred to as osteocytes
The composition matrix determines
- strength of bone
Proteins provide _____ strength
Minerals provide _____ strength
- TENSILE (proteins)
- COMPRESSION (minerals)
Osteoblasts
What are the 3 basic stages of existence?
What are these stages termed?
- bone-forming cells
- produce protein fibers for the matrix
- secrete enzymes that promote mineralization of the matrix
- once engulfed in the calcified matrix, they stop the above and become known as osteocytes
* * stages termed OSSIFICATION*
Osteocytes
- thought to be mechanosensors within bone, sensing tensile and compressive stress
- no longer bone-forming cells
- remain connected and communicate with the osteoblasts
Osteoclasts
- digest and remove excess (old) and damaged bone
- process is known as resorption and involves acid and enzyme secretion (think phagocytosis as this type of cell is a specialized macrophage)
All individual bone has 2 distinct areas of varying matrix density:
Compact Bone
Cancellous Bone
- makes up the surface of all bone and the shaft of long bones
- this is where one will find bundles of collagen fibers stacked in alternating layers and tightly packed in concentric rings around a vessel-containing canal, collectively termed haversian systems. Intercellular communication/transport occurs in both the longitudinal and transverse directions. Columns.
All individual bone has 2 distinct areas of varying matrix density:
Compact Bone
Cancellous Bone
- makes up the bulk of short, flat, and irregular bone, as well as the ends of the long bone
- it also lines the medullary cavity of long bone
- this is the more porous, marrow containing matrix
- aka - spongey bone, trabecular bone
Marrow
- aka myeloid tissue, always co-exists with cancellous bone
- considered a type of CT, and occurs in 2 somewhat interchangeable forms based on preponderance of cell type
RED MARROW & YELLOW MARROW
Red Marrow
- consists mainly of hematopoietic stem cells, and relative little fat
- site of RBC, WBC, and PLT production
- found at ends of long bone and center of other bone (but mainly flat bones)
Yellow Marrow
- consists mostly of fat cells (yellow tissue)
- site for adipose storage
- found in central (medullary) cavity of long bone
Endosteum
- thin CT lining the medullary cavity
- contains osteoblasts from the marrow
Periosteum
- dense CT covering the outer bone surface
- contians stem cells that can differentiate into osteoblasts and chondroblasts (cartilage forming cells)
- contains nocireceptors (sensory neurons)
Embryonic, Pediatric, and Adult Processes are depedent on:
hormones
Endochondral Ossification
chondrocyte -> cartilage growth - mineralization - vascularization, then apoptosis - marrow formation and osteoblast activation
- basis for lengthening and growth of bone (growth plates)
Intramembranous Ossification
osteoblast -> collagen matrix - mineralization
- basis for thickening and widening of bone (endosteum and periosteum)
* embryonic and child development involves both methods (embryonic skeleton begins primarily as cartilage, with activation of osteoblasts and subsequent ossification beginning in mid-to-late first trimester)
* adult skeleton undergoes constant intramembranous ossification balanced by osteoclast activity (a process termed remodeling), though both ossification methods are involved in fracture repair
Fracture Repair Process
- begins with cartilage production and mineralization to spongy bone over the first weeks to months
- synthesis of compact bone will follow over the next 3-5 years
Factors affecting osetoblask-osteoclast dynamic
- physical stress on bone stimulants
- nutritional factors such as Ca, P, Vitamin D promote strengthening
- hormonal influencers (look @ endocrine notes) include GH, estrogen, testosterone, parathyroid hormone, calcitonin, and steroid hormones
- direct toxicity and genetic factors may alter cellular activity
- other tissue needs for minerals or acid-neutralizing OH will stimulate resorption
- hydoxyapatite - main mineral compound of bone
- 99% of body Ca is in bone (when extracellular levels drop it gets pulled from bone
- bone also reservior for Mg, Fe, Na
Sinus (in reference to anatomy) may be defined as
“Undoubtedly, you will be treating conditions involving…”
- a hollow space, cavity within bone, narrow opening/canal, or a dilated channel as it relates to the cardiovascular system
- involving accessory nasal sinuses - cavities within skull bone
Accessory Nasal Sinuses
- cavities within skull bone that connect to the nasal cavity
- should be empty (air-filled), but as they are lined with the same epithelial membrane found within the nose they may exhibit the same SSx that occur with rhinitis - over production of mucus and membrane inflammation
Where are the 3 main sinuses found (for charting purposes)?
Frontal sinuses: above the eyes
Ethmoid sinuses: (anterior, middle, posterior): bridge of the nose, b/w the eyes
Maxillary sinuses: below the eyes and lateral to the nose
4th deep within the sphenoid bone and not accessible fo general observation
**observation techniques include: pen light, palpation, changes in voice tone
Synarthrosis
- immovable (fixed) joint connected by fibrous tissue
- teeth, sutures (of the skull), 1st rib and sternum
