Medical Science

Orthopedics

		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 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.

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

		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.

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