The passive part of this system can also be called the osteoarthrosyndesmology, which is the science of the bones and their articulations.
This branch of anatomy studies the skeleton. The skeleton is a complex of hard structures that originate in the mesenchyme and possesses mechanical importance. It consists of separate bones joined to each other by means of connective cartilaginous or bony tissue, which together make up the passive locomotor apparatus or system. The skeleton is composed of Axial(the skull, thorax and vertebral column) and appendicular(skeleton of upper and lower limbs) skeleton.
The skeleton consists of about 206 separate bones, out of which 24-40 are unpaired and the rest of them are paired.Each bone, with the exception of the cartilaginous joint surfaces and areas where flat tendons are attached, is enclosed in a connective tissue sheath, the periosteum.The structural and functional unit of the bone are the osteon and the trabecular pack. .
22
bones in skull
6 in
middle ears
1
hyoid bone
26 in
vertebral column
25 in
thoracic cage
4 in
pectoral girdle
60 in
upper limbs
60 in
lower limbs
2 in
pelvic girdle
206
bones in all.
ARTHROLOGY
T This branch of anatomy studies joints and articulations.Site
where rigid elements of the skeleton meet are called articulations. Joints are places of union between two or
more skeletal elements.They can be classified by the type of tissue present. Using this method, we can split the joints of the body into fibrous, cartilaginous and synovial joints.
Fibrous Joints
A fibrous joint is where the bones concerned are bound by fibrous tissue. Fibrous joints can further be subclassified into sutures, gomphmoses and syndesmoses.
Sutures:
- Immovable joint (called a synarthrosis)
- Only found between the bones of the skull.
- There is limited movement until about 20 years of age, after which they become fixed.
Fig 1.0 – Lateral view of the skull, showing the suture joints joining the skull bones together.
Gomphoses:
- Immovable joint (called a synarthrosis)
- Where the teeth articulate with their sockets in the maxillae (upper jaw) or the mandible(lower jaw)
- The fibrous connection that binds the tooth and socket is the periodontal ligament
Syndesmoses:
- Slightly movable joins (called an amphiarthrosis)
- Usual structure is bones held together by an interosseous membrane
- Middle radio-ulnar and middle tibiofibular joint are key examples.
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Cartilaginous:
In cartilaginous joints, the bones are attached by fibrocartilage or hyaline cartilage. They can be split into synchondroses and symphysis cartilgainous joints.
Synchondroses:
- Also known as primary cartilaginous joints, they only involve hyaline cartilage.
- The joints can be immovable (synarthroses) or slightly movable (amphiarthroses)
- The joint between the diaphysis and epiphysis of a growing long bone is a synchondrosis. This is interesting in that it is a temporary joint with no movement.
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Symphyses:
- Also known as a secondary cartilaginous joint, can involve fibrocartilage or hyaline cartilage
- The joints are slightly movable (amphiarthroses)
- An example of a symphysis is the pubic symphysis.
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The pubic symphysis, formed by a junction of the two pubic bones. It is an example of a symphysis. |
Synovial:
A synovial joint is a joint filled with synovial fluid. These joints tend to be fully moveable (known as diarthroses), and are the main type of joint found around the body. They are defined by the arrangement of their articular surfaces, and types of movement they allow.
Hinge:
- Permits flexion and extension
- Elbow joint is a notable example
Saddle
- Concave and convex joint surfaces
- E.g. Metatarsophalangeal joint
Plane
- Permit gliding or sliding movements
- E.g. Acromioclavicular joint
Pivot
- Allow rotation; a round bony process fits into a bony ligamentous socket
- E.g. Atlantoaxial joint & proximal radio-ulnar joint.
Condyloid:
- Permits flexion & extension, adduction, abduction & circumduction
- E.g. Metacarpophalangeal joint.
Ball & Socket
- Permits movement in several axis; a rounded head fits into a concavity
- E.g. Glenohumeral Joint.
MYOLOGY
Myology is the study of the muscular system.This includesthe study of the structure, function,and diseases of muscle.The muscular system consists of skeletal muscles which contract to move or position parts of the body (e.g., the bones that articulate at joints),smooth and cardiac muscles that propel, expel, or control the flow of fluids and contained substances.
| Muscles are connected with the bones,cartilages,ligaments, and skin, either directly, or through the intervention of fibrous structures called tendons or aponeuroses. Where a muscle is attached to bone or cartilage, the fibers end in blunt extremities upon the periosteum or perichondrium, and do not come into direct relation with the osseous or cartilaginous tissue. Where muscles are connected with its skin, they lie as a flattened layer beneath it, and are connected with its areolar tissue by larger or smaller bundles of fibers, as in the muscles of the face. |
| The muscles vary extremely in their form.In the limbs, they are of considerable length, especially the more superficial ones; they surround the bones, and constitute an important protection to the various joints. In the trunk, they are broad, flattened, and expanded, and assist in forming the walls of the trunk cavities. Hence the reason of the terms, long, broad, short, etc., used in the description of a muscle. |
There is considerable variation in the arrangement of the fibers of certain muscles with reference to the tendons to which they are attached. In some muscles the fibers are parallel and run directly from their origin to their insertion; these are quadrilateral muscles, such as the Thyrohyoideus. A modification of these is found in the fusiform muscles, in which the fibers are not quite parallel, but slightly curved, so that the muscle tapers at either end; in their actions, however, they resemble the quadrilateral muscles. Secondly, in other muscles the fibers are convergent; arising by a broad origin, they converge to a narrow or pointed insertion. This arrangement of these fibers is found in the triangular muscles—e. g., the Temporalis. In some muscles, which otherwise would belong to the quadrilateral or triangular type, the origin and insertion are not in the same plane, but the plane of the line of origin intersects that of the line of insertion; such is the case in the Pectineus. Thirdly, in some muscles (e. g., the Peronei) the fibers are oblique and converge, like the plumes of a quill pen, to one side of a tendon which runs the entire length of the muscle; such muscles are termed unipennate. A modification of this condition is found where oblique fibers converge to both sides of a central tendon; these are called bipennate, and an example is afforded in the Rectus femoris. Finally, there are muscles in which the fibers are arranged in curved bundles in one or more planes, as in the Sphincters. The arrangement of the fibers is of considerable importance in respect to the relative strength and range of movement of the muscle. Those muscles where the fibers are long and few in number have great range, but diminished strength; where, on the other hand, the fibers are short and more numerous, there is great power, but lessened range. |
| The names applied to the various muscles have been derived: (1) from their situation, as the Tibialis, Radialis, Ulnaris, Peronæus; (2) from their direction, as the Rectus abdominis, Obliqui capitis, Transversus abdominis; (3) from their uses, as Flexors, Extensors, Abductors, etc.; (4) from their shape, as the Deltoideus, Rhomboideus; (5) from the number of their divisions, as the Biceps and Triceps; (6) from their points of attachment, as the Sternocleidomastoideus, Sternohyoideus, Sternothyreoideus. |
| In the description of a muscle, the term origin is meant to imply its more fixed or central attachment; and the term insertion the movable point on which the force of the muscle is applied; but the origin is absolutely fixed in only a small number of muscles, such as those of the face which are attached by one extremity to immovable bones, and by the other to the movable integument; in the greater number, the muscle can be made to act from either extremity. |
| In the dissection of the muscles, attention should be directed to the exact origin, insertion,actions and innervation of each, and to its more important relations with surrounding parts. While accurate knowledge of the points of attachment of the muscles is of great importance in the determination of their actions, it is not to be regarded as conclusive. The action of the muscle deduced from its attachments, or even by pulling on it in the dead subject, is not necessarily its action in the living. By pulling, for example, on the Brachioradialis in the cadaver the hand may be slightly supinated when in the prone position and slightly pronated when in the supine position, but there is no evidence that these actions are performed by the muscle during life. It is impossible for an individual to throw into action any one muscle; in other words, movements, not muscles, are represented in the central nervous system. To carry out a movement a definite combination of muscles is called into play, and the individual has no power either to leave out a muscle from this combination or to add one to it. One (or more) muscle of the combination is the chief moving force; when this muscle passes over more than one joint other muscles (synergic muscles) come into play to inhibit the movements not required; a third set of muscles (fixation muscles) fix the limb—i. e., in the case of the limb-movements—and also prevent disturbances of the equilibrium of the body generally. As an example, the movement of the closing of the fist may be considered: (1) the prime movers are the Flexores digitorum, Flexor pollicis longus, and the small muscles of the thumb; (2) the synergic muscles are the Extensores carpi, which prevent flexion of the wrist; while (3) the fixation muscles are the Biceps and Triceps brachii, which steady the elbow and shoulder. A further point which must be borne in mind in considering the actions of muscles is that in certain positions a movement can be effected by gravity, and in such a case the muscles acting are the antagonists of those which might be supposed to be in action. Thus in flexing the trunk when no resistance is interposed the Sacrospinales contract to regulate the action of gravity, and the Recti abdominis are relaxed. |
| By a consideration of the action of the muscles, the surgeon is able to explain the causes of displacement in various forms of fracture, and the causes which produce distortion in various deformities, and, consequently, to adopt appropriate treatment in each case. The relations, also, of some of the muscles, especially those in immediate apposition with the larger bloodvessels, and the surface markings they produce, should be remembered, as they form useful guides in the application of ligatures to those vessels. |
| NB: the tree categories of locomotor system shall be dealt with into details in subsequent lectures. |
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