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Biol 2110 Name _________Eboni Cook____________________________________ Case Study: Bone Fracture and Muscle Contraction Date due: June 27th Please bring hard copy to class and post to drop box 35 points

Chief Complaint: 14-year-old girl admitted with a broken left leg. History: Nicole Michaelson, a 14-year-old girl, was skiing when she fell and broke her left leg. As she fell, her left leg got caught under the body of another skier who ran into her. An X-ray revealed that the fracture was a compound, tibial-fibular fracture just below the knee. The X-ray also revealed a torn meniscal cartilage in the knee above the fracture. The girl remained in the hospital for 14 days because of an infection of the leg in the area of skin breakage. Her immobilized leg was casted after the infection subsided. She remained in a full leg-length cast for 3 months, after which the upper portion of the cast was removed and she was allowed to star bearing weight on the leg. The bones ultimately healed, but the girl continued to have left knee swelling ("water on the knee") and pain made worse by walking. Arthroscopic examination of the knee revealed a meniscus that was still torn 6 months after her injury. Questions: 1. What is a compound fracture? (2 points) 

An injury in which a broken bone pierces the skin, causing a risk of infection.

2. Describe the microscopic features of the osseous tissue that help long bones withstand compressive forces without breaking. (4 points)  

weight-bearing pillars epiphyses (spongey bone)

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weight distribution

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Long bones have bony collar that can withstand compressive stretch and support the weight of the body. In the epiphyses is a spongy bone that helps withstand compressive forces by strengthening a bone to add minimum weight. In spongy bone tissue, there is trabeculae that can balance and distribute the weight of the body evenly out to the bony collar of the diaphysis.

3. What types of ossification processes formed this bone originally? ( 7 points)

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Endochondral ossification

4. What features of the knee joint structure help minimize friction between the thigh bone and the leg bone? (3 points) 

The knee joint is a synovial joint. It’s filled with synovial fluid that reduces friction between the femur and the tibia during flexion and extension of the knee. The joint surfaces of the femur and tibia are covered with smooth hyaline cartilage, which also helps reduce friction. There are also two pieces of fibrocartilage, the medial and lateral menisci. The shapes of these menisci match the shape of the medial and lateral condyles on the distal side of the femur, allowing stabilization of the knee joint and also shock absorbing function during weight-bearing.

5. Describe the changes a broken bone undergoes as it is healing. (the repair, process include all cells) 4 points  

fracture hematoma (i.e. blood clot) forms soft tissue callus

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fibroblasts and osteoblasts come in from the periosteum and endosteum

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fibroblasts lay down a collagen matrix - some of the fibroblasts turn into chondroblasts and lay down a fibrocartilage splint

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bony callus - osteoblasts begin to replace the fibrocartilage splint with spongy bone, forming a bulge that is initially wider than the after the injury.

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bone remodeling - as the patient starts to use the bone, the bone starts to remodel

The effects of bone fracture and muscle atrophy 6. What was the purpose of allowing weight bearing activity on the leg? How does weightbearing influence the bone repair process you described above? (i.e. what effect does weightbearing have on the orientation of the Haversian systems?) (3points) 

Wolff's law states that bone grows and remodels in response to the mechanical stresses placed upon it. Bone is laid down along lines of maximal stress.

7. After the bone healing process, the muscles of the leg exhibited atrophy. Explain the sequence of events starting with excitation of the muscle cell that result in contraction. Will therapy increase the diameter of the muscle? Why ? (10 points) 

Excitation–contraction coupling in skeletal muscle is a process by which depolarization of the sarcolemmal membranes is coupled to the opening of Ca2+ release channels on the sarcoplasmic reticulum (SR). This transduction is mediated by two key proteins – the t-

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tubule dihydropyridine receptor (DHPR)/Ca2+ channel and the SR ryanodine receptor (RyR) channel. The DHPR and RyR1 associate with other junctional proteins to form a macromolecular complex which spans the triad junction and interacts to control RyR opening. This interaction produces a fast transient rise in [Ca2+]i which activates the contractile proteins and results in muscle contraction. Yes. During the therapy exercise, the muscle cells will increase the number of mitochondria and myofilaments in the muscle cells. The increase of myosin filaments and actin will increase the diameter of the muscle cell and muscle.

8. Why would it take a longer time for the meniscus of the knee to heal? (2) 

Bones have a good blood supply. Cartilage, on the other hand, has a poor blood supply. Bones heal more quickly because the blood brings more nutrients. Cartilage has less blood therefore less nutrients and takes a long time to heal.

Be sure and site your references. (NO Points will be given if references are not attached. )

1. https://www.merriam-webster.com/dictionary/compound%20fracture 2. https://www.ukessays.com/essays/health-and-social-care/physical-exertion-affect-bonegrowth-health-and-social-care-essay.php 3. http://boneandspine.com/endochondral-ossification-and-intramembranous-ossification/ 4. http://www.innerbody.com/image/skel16.html 5. https://askabiologist.asu.edu/bone-healing 6. https://myokophysio.com/wolffs-law-what-is-it-and-why-do-i-need-to-know/ 7. https://www.sciencedirect.com/topics/medicine-and-dentistry/excitation-contraction-coupling AND https://www.ncbi.nlm.nih.gov/pubmed/2222798 8. https://socratic.org/questions/which-is-likely-to-heal-faster-a-bone-injury-or-a-cartilage-injury...