Chapter 5

ANATOMY OF THE BONES, CONTINUED

95. The bones of the upper and lower limbs are enlarged at each extremity, and have projections, or processes. To these, the tendons of muscles and ligaments are attached, which connect one bone with another. The shaft of these bones is cylindrical and hollow, and in structure, their exterior surface is hard and compact, while the interior portion is of a reticulated character. The enlarged extremities of the round bones are more porous than the main shaft.

96. The UPPER EXTREMITIES contain sixty-four bones--the _Scap´u-la_, (shoulder-blade;) the _Clav´i-cle_, (collar-bone;) the _Hu´mer-us_, (first bone of the arm;) the _Ul´na_ and _Ra´di-us_, (bones of the fore-arm;) the _Car´pus_, (wrist;) the _Met-a-car´pus_, (palm of the hand;) and the _Pha-lan´ges_, (fingers and thumb.)

97. The CLAVICLE is attached, at one extremity, to the sternum; at the other, it is united to the scapula. It is shaped like the Italic _[s]_. Its use is to keep the arms from sliding toward the breast.

98. The SCAPULA is situated upon the upper and back part of the chest. It is flat, thin, and of a triangular form. This bone lies upon and is retained in its position by muscles. By their contractions it may be moved in different directions.

99. The HUMERUS is cylindrical, and is joined at the elbow with the ulna of the fore-arm; at the scapular extremity, it is lodged in the _glenoid_ cavity, where it is surrounded by a membranous bag, called the _capsular ligament_.

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95-104. _Give the anatomy of the bones of the upper extremities._ 95. Give the structure of the bones of the extremities. 96. How many bones in the upper extremities? Name them. 97. Give the attachments of the clavicle. What is its use? 98. Describe the scapula. How is it retained in its position? 99. Describe the humerus.

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100. The ULNA articulates with the humerus at the elbow, and forms a perfect hinge-joint. This bone is situated on the inner side of the fore-arm.

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What is represented by fig. 13? By fig. 14? 100. Describe the ulna.

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101. The RADIUS articulates with the bones of the carpus and forms the wrist-joint. This bone is situated on the outside of the fore-arm, (the side on which the thumb is placed.) The ulna and radius, at their extremities, articulate with each other, by which union the hand is made to rotate, permitting its complicated and varied movements.

102. The CARPUS is composed of eight bones, ranged in two rows, and so firmly bound together, as to permit only a small amount of movement.

103. The METACARPUS is composed of five bones, upon four of which the first range of the finger-bones is placed; and upon the other, the first bone of the thumb. The five metacarpal bones articulate with the second range of carpal bones.

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101. The radius. 102. How many bones in the carpus? How are they ranged? 103. Describe the metacarpus.

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104. The PHALANGES of the fingers have three ranges of bones, while the thumb has but two.

_Observation._ The wonderful adaptation of the hand to all the mechanical offices of life, is one cause of man's superiority over the rest of creation. This arises from the size and strength of the thumbs, and the different lengths of the fingers.

105. The LOWER EXTREMITIES contain sixty bones--the _Fe´mur_, (thigh-bone;) the _Pa-tel´la_, (knee-pan;) the _Tib´i-a_, (shin-bone;) the _Fib´u-la_, (small bone of the leg;) the _Tar´sus_, (instep;) the _Met-a-tar´sus_, (middle of the foot;) and the _Pha-lan´ges_, (toes.)

106. The FEMUR is the longest bone in the system. It supports the weight of the head, trunk, and upper extremities. The large, round head of this bone is placed in the acetabulum. This articulation is a perfect specimen of the ball and socket joint.

107. The PATELLA is a small bone connected with the tibia by a strong ligament. The tendon of the _ex-tens´or_ muscles of the leg is attached to its upper edge. This bone is placed on the anterior part of the lower extremity of the femur, and acts like a pulley, in the extension of the limb.

108. The TIBIA is the largest bone of the leg. It is of a triangular shape, and enlarged at each extremity.

109. The FIBULA is a smaller bone than the tibia, but of similar shape. It is firmly bound to the tibia, at each extremity.

110. The TARSUS is formed of seven irregular bones, which are so firmly bound together as to permit but little movement.

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104. How many ranges of bones have the phalanges? 105-112. _Give the anatomy of the bones of the lower extremities._ 105. How many bones in the lower extremities? Name them. 106. Describe the femur. 107. Describe the patella. What is its function? 108. What is the largest bone of the leg called? What is its form? 109. What is said of the fibula? 110. Describe the tarsus.

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Explain fig. 17. Explain fig. 18.

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111. The METATARSAL bones are five in number. They articulate at one extremity with one range of tarsal bones; at the other extremity, with the first range of the toe-bones.

_Observation._ The tarsal and metatarsal bones are united so as to give the foot an arched form, convex above, and concave below. This structure conduces to the elasticity of the step, and the weight of the body is transmitted to the ground by the spring of the arch, in a manner which prevents injury to the numerous organs.

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111. Describe the metatarsal bones. Explain fig. 19. What is represented by fig. 20? What is said of the arrangement of the bones of the foot?

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112. The PHALANGES (fig. 19) are composed of fourteen bones; each of the small toes has three ranges of bones, while the great toe has but two.

113. The JOINTS form an interesting part of the body. In their construction, every thing shows the regard that has been paid to the security and the facility of motion of the parts thus connected together. They are composed of the extremities of two or more bones, _Car´ti-lages_, (gristles,) _Syn-o´vi-al_ membrane, and _Lig´a-ments_.

114. CARTILAGE is a smooth, solid, elastic substance, of a pearly whiteness, softer than bone. It forms upon the articular surfaces of the bones a thin incrustation, not more than the sixteenth of an inch in thickness. Upon convex surfaces it is the thickest in the centre, and thin toward the circumference; while upon concave surfaces, an opposite arrangement is presented.

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112. Describe the phalanges. 113-118. _Give the anatomy of the joints._ 113. What is said of the joints? Of what are the joints composed? What is illustrated by fig. 21? By fig. 22? 114. Define cartilage.

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115. The SYNOVIAL MEMBRANE is a thin, membranous layer, which covers the cartilages, and is thence bent back, or reflected upon the inner surfaces of the ligaments which surround and enter into the composition of the joints. This membrane forms a closed sac, like the membrane that lines an egg-shell.

116. Beside the synovial membrane, there are numerous smaller sacs, called _bur´sæ mu-co´sæ_. These are often associated with the articulation. In structure, they are analogous to synovial membranes, and secrete a similar fluid.

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115. Describe the synovial membrane. 116. Describe the bursæ mucosæ. What is represented by fig. 23? By fig. 24?

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117. The LIGAMENTS are composed of numerous straight fibres, collected together, and arranged into short bands of various breadths, or so interwoven as to form a broad layer, which completely surrounds the articular extremities of the bones, and constitutes a capsular ligament. These connecting bands are white, glistening, and inelastic. Most of the ligaments are found exterior to the synovial membrane.

118. The bones, cartilages, ligaments, and synovial membrane are insensible when in health; yet they are supplied with organic nerves, as well as with arteries, veins, and lymphatics.

_Observation._ The joints of the domestic animals are similar in their construction to those of man. To illustrate this part of the body, a fresh joint of the calf or sheep may be used. After divesting the joints of the skin, the satin-like bands, or ligaments, will be seen passing from one bone to the other, under which may be observed the membranous bag, called the capsular ligament. This is very smooth, as it is lined with the soft synovial membrane, beneath which will be seen the cartilage, that may be cut with a knife, and under this the rough extremity of the ends of the bones.

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117. Of what are ligaments composed? What is the appearance of these bands? Where are they found? 118. With what vessels are the cartilages and ligaments supplied? How can the structure of the joints be explained?

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