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L5 histo- bone
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- 1Explain the relationship between the thyroid and parathyroid hormones and the calcium level in bone and in the blood- During hypercalcemia (high Ca2+) the thyroid hormone secretes calcitonin which stimulates calcium salt deposit in bones and inhibits osteoclasts
- During hypocalcemia the parathyroid glands release parathyroid hormone (PTH) which stimulates osteoclasts to degrade bone matrix to release Ca2+ into blood - 2—1- articular cartilage; epiphysis
2. epiphyseal line; apophysis
3. compact/cortical bone
4. periosteum/diaphysis
5. metaphysis/nutrient foramen
6. medullary/marrow cavity
7. spongy/cancellous/trabecular bone
8. muscle attachment site
9. tendon of muscle
- 3Describe a decalcified bone preparation- soft bc mineral is gone and you can slice-> thin so you can see thru them and see details
- acid extracts the mineral
- can be cut and stained like other tissues
- visualize cellular components - 4Describe a ground bone preparation- hard but still you want thin
- a piece of bone is cut with a diamond saw and ground on a wheel until the section is thin enough to view
- visualize matrix components
- can't see cells but cell lacuna - 5—Top- decalcified
bottom- ground
- 63 types of bone cells?- osteoblasts: bone forming cells that secrete and synthesize osteoid, the un-mineralized organic component of bone
- osteoclasts: bone resorbing cells that break down the matrix
- osteocytes: osteoblasts that are entrapped in bone matrix that maintain bone matrix - 7—large pink- osteoclasts
several purple dots- osteoblasts
single purple dots- osteocyte sitting in a lacuna - 8What are features of osteoblasts?- cuboidal to columnar
- derived from mesenchyme/embryonic tissue
- single layer on bone surfaces
- basophilic cytoplasm (blue/purple)
- nucleus often off center
- cytoplasmic processes communicate via gap junctions - 9What are features of osteocytes?- osteoblasts trapped within lacunae
- cytoplasmic processes travel through canaliculi to communicate via gap junctions - 10What are features of osteoclasts?- located on bone surfaces
- giant, multi-nucleated
- derived from fusion monocytes
- face bone with "ruffled" border
- secrete enzymes and acids to break down bone matrix
- phagocytose debris
- acidophilic cytoplasm- stains red - 11What is the lacuna that osteocytes create called?An erosion lacuna- forms eroded boney matrix
- 12What are the components of organic matrix of ECM?- Fibers: Type I is primary; function is to provide strength to each osteon-> would crumble without it
- Ground substance: sulfated GAGs and Glycoproteins (osteo..) - 13What is the function of organic matrix?Provide strenght
- 14What is the function of inorganic matrix?makes bone hard
- 15What are the components of inorganic matrix?- hydroxyapatite crystals deposited within the collagen network
- principal ions (calcium, phosphorous, carbonate, hydroxide, sodium, magnesium, potassium, iron) - 16List and differentiate the two bone liningsPeriosteum: lines outside
- fibrous layer: dense CT
- cellular layer: closest to bone and osteoblasts and osteoclasts
Endosteum: lines inside - 17What are the two types of bone marrow?Red: developing blood cells
Yellow: fat-storing cells - 18Which type of marrow increases with age?Yellow
- 19What are the two types of bone identified macroscopically?1. Compact- denser, harder stronger
2. Trabecular- more flexible - 20What is the functional unit of compact bone and what does it include?Osteon (haversian system)
- osteonal/haversian canal: central canal, nerve/blood supply & lymph nodes
- concentric layers (lamellae) surround osteonal canal-> sheets of bones laid down by osteoblasts and they become entrapped and become osteocytes - 21What are remnants of old osteons?Interstital lamellae
- 22—left: compact
right: trabecular
- 23Where is trabecular bone present?ends of some long bones, flat bones, irregular bones
- 24What is the histological structure of trabecular bone?- made of spicules and trabeculae
- lamellae are parallel or concentric
- capillaries between trabeculae nourish osteocytes
- bone marrow occupies endosteum lined spaces between trabeculae and spicules - 25Describe primary bone- woven, immature, new
- first type to be formed during development or repair
-many osteocytes (highly cellular)
-disorganized - 26Describe secondary bone- lamellar, mature
- replaces all primary bone in adults
- produced by remodeling of primary bone
- lacunae are arranged in layers in an orderly fashion
- the collagen fibers are parallel within lamella
- contains a higher concentration of inorganic matrix than primary bone making it more rigid - 27—left: primary
right: secondary
- 28What do bones differentiate from?Pluripotent embryonic tissues
- 29How are most bones formed?Endochondrally- replacement of a cartilage model
- 30How are calvaria and face bones formed?Intramembranously: ectomesenchyme cells become osteoblasts directly rather than becoming chondroblasts
- 31What involves intramembranous and encochondral ossification?bone repair (fractures)
- 32What are the steps of direct/intramembranous ossification?1. Some cells within the mesenchyme differentiate into osteoblasts
2. Osteoblasts secrete osteoid (matrix) that becomes calcified. Trapped osteoblasts become osteocytes
3. Osteoid is laid down around blood vessels, forming a meshwork of trabecular bone. Mesenchyme gathers near the edges and becomes periosteum.
4. Trabeculae just deep to the periosteum become compact bone. Diploe remains and its vascular spaces are known as red bone marrow (where hematopoiesis occurs) - 33What are the zones of endochondral ossification?1. Primary ossfication center/epiphysis
2. Zone of reserve/resting- hyaline cartilage where chondrocytes are distributed singly or in groups
3. Zone of proliferation- chondrocytes arranges in columns, mitotic division creates isogenous groups
4. Zone of hypertrophy- interstitial growth, chondrocytes swell, new cartilage matrix between cell columns
5. Zone of resorption- blood vessels invade matrix to bring in osteoproginator cells
6. Zone of ossification- bony material deposited on the plates of calcified catilage matrix, where bone marrow can now be seen - 34Does the size of the epiphyseal plate increase with bone growth?the growth of the cartilage is balanced with the bone that replaces it. The epiphyseal line (as opposed to plate) develops when lengthening of the bone stops and all cartilage is replaced by bone. Over time, as bone remodels, the line becomes less and less visible.
- 35When does bone growth stop?Growth stops in the physeal plate, when the cartilage is replaced by bone.
Timing of closures of the physeal plates vary per bone, among species, and even somewhat between individuals - 36What happens in fracture repair?Macrophages remove the damaged matrix, and dead osteocytes adjacent to the break.
Cell proliferation
Adjacent periosteum and endosteum proliferate to produce osteoprogenitor cells. - 37What happens in bone remodeling?Existing bone is resorbed by osteoclasts and osteoblasts secrete new bone.
Remodeling replaces primary bone with stronger secondary bone.
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- Fichas sobre L5 histo- bone, creado por Reagan McCrary el 01/10/2020.
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- Reagan McCrary
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