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Medical Science


Orthopedics concerns with correction of deformities or functional impairments of the skeletal system, especially the extremities and the spine, and associated structures such as the muscles and ligaments (Figure 27a).

Orthopedics Limbs Vertebrates are segmented chordates in which the notochord is replaced in the adult by a vertebral column composed of individual vertebrae. The skeleton is internal, and in all the vertebrates, there is not only a backbone but also a skull, or cranium, to enclose and to protect the brain. In higher vertebrates, other parts of the skeleton serve as attachment for muscles and for protection of internal organs of the thoracic cavity and the abdomen. Movements are provided by muscles attached to the endoskeleton. All but the fishes are tetrapods, meaning that they have four limbs. General body plan consists of head, trunk, two pairs of appendages, and a postanal tail (these structures are highly modified in many vertebrates and sometimes absent). There is a fundamental design in the skeleton of all vertebrates. Humans,

Figure 27a Orthopedics
[view large image]

Figure 27b Limbs
[view large image]

bats, lizards, and whales are all just variations on a theme (see for example the common pattern of limbs for some vertebrates in Figure 27b).
Bone Bone is the major component of the skeletons in adult vertebrates. It is composed of both living tissues, such as bone cells, fat cells, and blood vessels, and nonliving materials (such as collagen) secreted by the bone cells called osteoblasts into the inter-cellular space. The collagen fibers are coated with a calcium phosphate salt, making it strong without being brittle. As shown in Figure 27c, a bone can be divided into four parts:

Figure 27c Bone Structure
[view large image]

1. Periosteum - This fibrous membrane is the outer layer of the bone. It is rich with blood vessels and nerve endings and it ends at the edge of the joint area or where the ligaments and the tendons insert themselves.

2. Compact bone - This part makes up most of the bone of arms and legs. The structural units of compact bone are osteons, elongated cylinders that act as weight-bearing pillars, able to withstand any mechanical stress placed on the bone. The center of each osteon contains a hollow canal that acts as a central passageway (Haversian canal) for blood vessels and nerves.

3. Spongy bone - In some bones, internal to the compact bone is spongy bone composed of a honeycomb network of bones called trabeculae that act as supporting beams. Spongy bone is designed to bear stress from several directions, such as that exerted on the pelvis in bending or stretching. The spaces between the trabeculae are filled with red bone marrow containing the blood vessels that nourish spongy bone. In additon to produce cells, which make up the bone, the cells of red bone marrow also produce the majority of the cellular elements of the blood and of the lymph. Spongy bone is found in bones of the pelvis, ribs, breastbone, vertebrae, skull, and at the ends of the arm and leg bones.

4. Bone marrow - It is the soft tissue found in the hollow interior of bones. In adults, marrow in large bones produces new blood cells. There are two types of bone marrow: red marrow (consisting mainly of myeloid tissue) and yellow marrow (consisting mainly of fat cells). Red blood cells, platelets and most white blood cells arise in red marrow; some white blood cells develop in yellow marrow. Both types of bone marrow contain numerous blood vessels and capillaries. At birth, all bone marrow is red. With age, more and more of it is converted to the yellow type. About half of the bone marrow is red. Red marrow is found mainly in the flat bones, such as the hip bone, breast bone, skull, ribs, vertebrae and shoulder blades, and in the spongy material at the proximal ends of the long bones femur and humerus. Yellow marrow is found in the hollow interior of the middle portion of long bones. In cases of severe blood loss, the body can convert yellow marrow back to red marrow in order to increase blood cell production.

Vertebra An important contribution to the shape of animals with backbones is the number of vertebrae (bones in spinal column) that make up the structure. While human has 33, snakes have more than 300, with some species having more than 500. Vertebrae develop from segments of tissue called somites, which form, one after another, in a head-to-tail sequence in the embryo (diagram a, Figure 27d). They bud off from the "head" end of the presomitic mesoderm (PSM), an immature tissue fated to generate the somites. This budding is regulated by a "clock-and-wavefront" model. In snakes, the clock genes seems to express 4 times faster than in shorter-bodies animal (such as mice), leading to many more, though smaller, somites (see diagram b in Figure 27d).

Figure 27d Somitogenesis [view large image]

Table 06a below lists some Orthopedic specialities for bone healing.

Disease Symptom(s) Cause(s) Treatment(s)
ACL Injury, Sprains, Strains Instability in the knee (ACL), pain, swelling, bruising, inflammation Tear in knee ligament (ACL), generally in ligaments and tendons Physical Rehabilitation, surgery; Rest, Ice, Compression, Elevation (RICE)( see link)
Bone Fracture Swelling, deformity, pain, loss of function, protruding bone High impact, medical conditions Pain management, immobilization with cast, surgery ( see link)
Bone Tumor Painless mass, Pain, fatigue, fever, weight loss, anemia, unexplained bone fractures Benign tumors, cancerous growth Medication, chemotherapy, radiotherapy, surgery
( see link)
Concussion Headache, confusion, amnesia, dizziness, nausea, vomiting, slurred speech, fatigue Traumatic brain injury Rest (physical and mental)
( see link)
Elbow Injury Elbow Deformity, protruding bone Inflammation or injury to the tendons that attach muscle to bone Rest, ice (20 mins, 3 times/day), compression with bandage, Elevating arm ( see link)
Frozen (Fifty) Shoulder Chronic shoulder pain with limitation of movement Adhesive capsulitis of the shoulder joint often associated with ageing ( > 50 years old) Medication, prolotherapy, prescribed exercises
( see link)
Herniated Disk Arm or leg pain, numbness or tingling, muscle weakness Slipped or ruptured cushion disk between the vertebrae compressing the nerves Medications, therapy, surgery
( see link)
Muscular Dystrophy Frequent falls, trouble with movement, waddling gait, walking on toes, large calf muscles, learning disabilities Abnormal genes in X-chromosome interfere with the production of healthy muscle No cure, some relief by medications, therapy, surgery
( see link)
Osteoporosis Back pain, loss of height, stooped posture, easy bone fracture Rate of bone mass loss exceeds replacement Medications
( see link)
Whiplash Neck pain, stiffness, headaches, numbness in the arms, fatigue, dizziness Neck injury due to forceful, rapid back-and-forth movement Rest, medications, exercise, physical therapy ( see link)

Table 06a Orthopedics

Shark has no bone, its skeleton is made of lightweight and flexible material called cartilage, which is a type of connective tissue similar to bone.
Skeletons Elephant Shark Both are composed of living cells that maintain a non living matrix. Obviously, the sharks evolved along a slightly different path than the bony fish. They solved the buoyancy problem (in water) with lightweight skeleton, while the bony fish developed swim bladder and can afford to bear heavier skeleton.

Figure 27e Skeleton of Fish and Shark [view large image]

Figure 27f Elephant Shark

A 2014 Nature article about the genome of Elephant Shark (Figure 27f) reveals that it is the absence of a single gene family that inhibits the turning of cartilage into bone.
    Following summaries the differences in skeleton between these two groups (Figure 27e) :

  1. Bony fish's bone is calcified just like ours (such as the vertebra and fins in Figure 27e), while the shark's are made of cartilage similar to our joints and the flexible part of our nose.

  2. The upper jaw of shark is not attached to the skull as it is in bony fish.

  3. The skull of shark is made of 10 cartilaginous elements while the bony fish's has about 63 bones.

  4. Bony fish have pleural ribs formed from dermal bone and sharks lack these ribs.

  5. Bony fish have bony plate to cover their gills, the gill slits of shark are exposed and visible.

See also Frilled Shark and Fish Anatomy.

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