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12 year old boy has broken elbow and appears to have bone protruding from…
12 year old boy has broken elbow and appears to have bone protruding from the skin in the upper arm. Patient diet lacks dairy and only eats junk food.
Anatomy of long bone
General characteristic of a long bone includes a shaft, bone ends, and membranes.
Diaphysis - a shaft forming the long axis of the bone. Constructed primarily of thick compact bone. Surrounds the Medullary cavity that contains yellow marrow and spongy bone .
Epiphysis - the bone ends. composed of an outer shell of compact bone and an inner shell of spongy bone. A thin layer of hyaline cartilage surround the joint surface .
Epiphyseal line- a remnant of epiphyseal plate, between the diaphysis and epiphysis lies a disc of hyaline cartilage that grows during childhood to lengthen bone.
Membranes
Periosteum - double layered membrane covers the external surface of the entire bone except the joint surfaces. Outer fibrous layer contains dense irregular connective tissue and the inner contains osteoprogenitor cells . Also contains bone destroying cells (osteoclasts) and bone forming cells (osteoblasts)
Endosteum - covers internal bone surfaces, covering the trabeculae of the spongy bone and lines canals that pass through the compact bone. contains same cells as periosteum.
Blood vessels and nerves
Bones are well vascularized. Main vessels in diaphysis are nutrient artery and a nutrient vein that run through the nutrient foramen. Nerves accompany blood vessels through nutrient foramen into the bone. the same arteries and veins serve the epiphysis.
Epiphyseal plate
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On the epiphyseal side of the epiphyseal plate , cartilage is formed.
on the diaphysial side , cartilage is ossified, allowing the diaphysis to grow in length.
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Cells of bone tissue
Osteoprogenitor - mitotica active stem cells, found in periosteum and endosperm. differentiate into osteoblasts
Osteoblasts - bone forming cells, secrete bone matrix, actively mitotic, completely surrounded by matrix secreted they become osteocytes.
Osteocytes - mature bone cells that occupy spaces (lacunae) that conform to their shape. Monitor and maintain bone matrix, act as strain or stress sensors. responsible for bone remodeling
Bone lining cells - on bone surface where bone remodeling is not going on, maintain matrix
Osteoclasts - giant multinucleate cells located at sites of bone reabsorption. responsible for degrading bone and sealing off areas.
Bone formation
Ossification - Process of bone tissue formation. In embryos the process leads to formation of bony skeleton. another form of ossification is bone growth that goes on into adulthood as body increases. Ossification in adults serve as bone remodeling and repair.
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Bone Growth
Mimics events of endochondral ossification, process involves zones where specific functions occur, Below resting zone, the cartilage cells form tall columns, like coin stacks, that allow fast and efficient growth.
- Proliferation zone - these cells divide quickly, pushing the epiphysis away from the diaphysis and lengthening the entire long bone
- Hypertrophic zone - The older chondrocytes in the stack, closer to the diaphysis, hypertrophy. their lacunae erode and enlarge, leaving large interconnecting spaces
- Calcification - Surrounding cartilage calcifies, chondrocytes dies, and matrix deteriorate, allowing blood vessels to invade. Leaving long spicules of calcified cartilage at the epiphysis diaphyisis junctions
- Ossification zone - Spicules invaded by marrow elements from medullary cavity. osteoclasts partly erode the cartilage spicules, then osteoblasts cover them with new bone. As osteoclasts digest the specula tips, the medullary cavity also lengthens
Bone remodeling
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when bone is broken down to increase blood calcium levels, PTH is released and osteoclasts are activated.
Mechanical forces acting on osteocytes direct which osteoclasts are called into action, so that bone in the least stressed areas is broken down first.
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Upstream causes
Indirect cause - possible indirect cause of bone fracture is due to lack of calcium intake that is needed for bone which is uncommon in young adults
direct cause- possible direct cause is due to hard landing on right arm on a very hard surface like concrete .
downstream effects
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second downstream effect - bone fracture is a complete displaced compound fracture and will need to be reduced
Physician will have to surgically place screws in order to realign bone again. Followed by a cast in order to secure the site.
third downstream effect - Patient lacks calcium which is needed for bone growth and lacks a healthy diet
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fourth downstream effect - Bones in young adults are less likely to break due to the bone having a hard plastic like structure compared to an elderly person who would have bones compared to glass.
Because the patient was able to fully break the bone, the lack of calcium and bone growth hormones may slow down the recovery therefore will need to administered bone growth hormones to better help bone recovery.