Endochondral Ossification
Step 5
Childhood to adolescence.
The epiphyses ossify. When completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages.
The cells at the "top" side of the stack next to the resting zone comprise the proliferation or growth zone. The cells divide quickly, pushing the epiphysis away from the diaphysis and lengthening the entire long bone.
Proliferation zone
Name the functions of skin.
Protection, blood reservoir, thermoregulation, physical barrier, chemical barrier.
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Main functions of the skeletal system?
Supports, protects, movement, mineral and growth factor storage, blood cell formation, triglyceride storage, hormone production.
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Smallest functional unit of a skeletal muscle fiber and is a highly organized arrangement of contractile, regulatory, and structural proteins. It is the shortening of these individual _______ that lead to the contraction of individual skeletal muscle fibers (and ultimately the whole muscle). Comprised of thick and thin filaments.
Sarcomere
Step 4
Birth to childhood.
The diaphysis elongates and a medullary cavity forms. Secondary ossification centers appears in the epiphysis.
Meanwhile, the older chondrocytes in the stack, which are closer to the diaphysis, hypertrophy, and their lacunae erode and enlarge, leaving large interconnecting spaces.
Hypertrophic zone
Only affects epidermis, no blistering, scarring is rare. Often heals on its own.
First degree burns
Mitotically active stem cells found in the membrane of periosteum and endosteum. Essentially bone stem cells. Flattened or squamous
Osteogenic or osteoprogenitor cells.
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Describe the 4 characteristics of muscle tissue.
Excitability - Also termed responsiveness. Ability to receive and respond to an action potential.
Contractility - Shorten forcibly when adequately stimulated.
Extensibility - Ability to stretch or go beyond the resting state when contracting.
Elasticity - Ability to recoil and resume resting state after stretching.
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Step 3
Month 3
The periosteal bud invades the integral cavities and spongy bone forms.
Subsequently, the surrounding cartilage matrix calcifies and these chondrocytes die and deteriorate, producing this zone.
Calcification zone
Why are 3rd degree burns life threatening?
Fluid loss/electrolyte imbalance and infection.
Cells located at sites of reabsorption. Arise from same stem cells that become macrophages. Giant and multinucleated. Ruffled border. Directly contacts the bone. Actively reabsorbing – rest in a shallow depression known as reabsorption bay.
Osteoclasts
Difference between Isometric and Isotonic contractions?
Isometric- tension may build to the muscle’s peak tension-producing capacity but the muscle neither shortens nor lengthens.
Isotonic- Muscle length changes to move load.
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Step 2
Week 9-Month 3
Cartilage in the center of the diaphysis calcifies and then develops cavities.
Calcified spicules ultimately become part of the ______ zone or ______ zone and are invaded by marrow elements from the medullary cavity. Osteoclasts partly erode the cartilage spicules, then osteoblasts quickly cover them with new bone. Ultimately spongy bone replaces them. Osteoclasts digest the spicule tips, the medullary cavity also lengthens.
Ossification zone
What are the contributing factors of skin color?
Melanin, carotene, and hemoglobin.
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Mature bone cells monitor and maintain the bone matrix. Spidery looking. Occupy spaces (lacunae) that conform to their shape. Act as sensors for strain and stress respond mechanical stimuli (bone loading, bone deformation, weightlessness). Act as messengers to communicate to cells responsible for bone remodeling.
Osteocytes
Explain the 4 steps of excitement contraction coupling.
1. Action potential travels across entire sarcolemma and down the T tubules.
2. Release Ca2+ into sarcoplasmic reticulum allowing calcium to flow into cytosol.
3. Ca2+ floating into the SR and binds to troponin which changes its shape exposing binding sites for myosin to bind to.
4. Myosin is now bonded to actin forming cross bridge and cross bridge cycling begins. E-C coupling ends.
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Step 1
Week 9
Bone collar forms around the diaphysis of hyaline cartilage model.
Cartilage next to the diaphysis which organizes into a pattern that allows fast, efficient growth. The cartilage cells here form tall columns, like coins in a stack.
Epiphyseal plate
Where are dermal ridges found?
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Bone forming cells that comes from bone matrix. Actively mitotic. Secrete collagen (90% of bone protein) and calcium binding protein. Cube shaped. Once completely surrounded by matrix they become osteocytes.
Osteoblasts
Explain the 5 steps at the neuromuscular junction.
1. Action potential reaches axon terminal
2. Voltage gated Ca2+ open, Ca2+ enters axon terminal, moving down concentration gradient
3. Ca2+ comes in causing ACh to release into synaptic cleft
4. ACh diffuses across synaptic cleft.
5. Open ligand gated channels allowing for movement of Na+ and K+
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