A Treatise on Anatomy, Physiology, and Hygiene (Revised Edition) by Calvin Cutter (read more books .txt) 📕
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77. The skull is convex externally, and at the base much thicker than at the top or sides. The most important part of the brain is placed here, completely out of the way of injury, unless of a very serious nature. The base of the cranium, or skull, has many projections, depressions, and apertures; the latter affording passages for the nerves and blood-vessels.
74. How many bones in the human body? How are they divided? 75–81. Give the anatomy of the bones of the head. 75. How are the bones of the head divided? 76. Describe the bones of the skull. 77. What is the form of the skull? What does the base of the skull present?
3378. The bones of the cranium are united by ragged edges, called sut´ures. The edges of each bone interlock with each other, producing a union, styled, in carpentry, dovetailing. They interrupt, in a measure, the vibrations produced by external blows, and also prevent fractures from extending as far as they otherwise would, in one continued bone. From infancy to the twelfth year, the sutures are imperfect; but, from that time to thirty-five or forty, they are distinctly marked; in old age, they are nearly obliterated.
Fig. 7.
Fig. 7. 1, 1, The coronal suture at the front and upper part of the skull, or cranium. 2, The sagittal suture on the top of the skull. 3, 3, The lambdoidal suture at the back part of the cranium.
79. We find as great a diversity in the form and texture of the skull-bone, as in the expression of the face. The head of the New Hollander is small; that of the African is compressed; while the Caucasian is distinguished for the beautiful oval form of the head. The Greek skulls, in texture, are close and fine, while the Swiss are softer and more open.
78. How are the bones of the skull united? What are the uses of the sutures? Mention the appearance of the sutures at different ages. What does fig. 7 represent? 79. What is said respecting the form and texture of the skull in different nations?
3480. In each EAR are four very small bones. They aid in hearing.
81. In the FACE are fourteen bones, some of which serve for the attachment of powerful muscles, which are more or less called into action in masticating food; others retain in place the soft parts of the face.
Fig. 8.
Fig. 8. 1, The frontal, or bone of the forehead. 2. The parietal bone. 3, The temporal bone. 4, The zygomatic process of the temporal bone. 5, The malar (cheek) bone. 6, The superior maxillary bone, (upper jaw.) 7, The vomer, that separates the cavities of the nose. 8, The inferior maxillary bone, (lower jaw.) 9. The cavity for the eye.
82. The TRUNK has fifty-four bones—twenty-four Ribs; twenty-four bones in the Spi´nal Col´umn, (back-bone;) four in the Pel´vis; the Ster´num, (breast-bone;) and the Os hy-oid´es, (the bone at the base of the tongue.) They are so arranged as to form, with the soft parts attached to them, two cavities, called the Tho´rax (chest) and Ab-do´men.
80. How many bones in the ear? 81. How many bones in the face? What is their use? Explain fig. 8. 82–94. Give the anatomy of the bones of the trunk. 82. How many bones in the trunk? Name them. What do they form by their arrangement?
3583. The THORAX is formed by the sternum in front; the ribs, at the sides; and the twelve dorsal bones of the spinal column, posteriorly. The natural form of the chest is a cone, with its apex above; but fashion, in many instances, has nearly inverted this order. This cavity contains the lungs, heart, and large blood-vessels.
Fig. 9.
Fig. 9. 1, The first bone of the sternum, (breast-bone.) 2. The second bone of the sternum. 3, The cartilage of the sternum. 4, The first dorsal vertebra, (a bone of the spinal column.) 5, The last dorsal vertebra. 6, The first rib. 7, Its head. 8, Its neck. 9, Its tubercle. 10, The seventh, or last true rib. 11, The cartilage of the third rib. 12, The floating ribs.
84. The STERNUM is composed of eight pieces in the child. These unite and form but three parts in the adult. In youth, the two upper portions are converted into bone, while the lower portion remains cartilaginous and flexible until extreme old age, when it is often converted into bone.
85. The RIBS are connected with the spinal column, and increase in length as far as the seventh. From this they successively 36 become shorter. The direction of the ribs from above, downward, is oblique, and their curve diminishes from the first to the twelfth. The external surface of each rib is convex; the internal, concave. The inferior, or lower ribs, are, however, very flat.
83. Describe the thorax. Explain fig. 9. 84. Describe the sternum. 85. Describe the ribs.
86. The seven upper ribs are united to the sternum, through the medium of cartilages, and are called the true ribs. The cartilages of the next three are united with each other, and are not attached to the sternum; these are called false ribs. The lowest two are called floating ribs, as they are not connected either with the sternum or the other ribs.
87. The SPINAL COLUMN is composed of twenty-four pieces of bone. Each piece is called a vert´e-bra. On examining one of the bones, we find seven projections, called processes; four of these, that are employed in binding the bones together, are called articulating processes; two of the remaining are called the transverse; and the other, the spinous. The last three give attachment to the muscles of the back.
88. The large part of the vertebra, called the body, is round and spongy in its texture, like the extremity of the round bones. The processes are of a more dense character. The projections are so arranged that a tube, or canal, is formed immediately behind the bodies of the vertebræ, in which is placed the me-dul´la spi-na´lis, (spinal cord,) sometimes called the pith of the back-bone.
89. Between these joints, or vertebræ, is a peculiar and highly elastic substance, which much facilitates the bending movements of the back. This compressible cushion of cartilage also serves the important purpose of diffusing and diminishing the shock in walking, running, or leaping, and tends to protect the delicate texture of the brain.
86. How are the ribs united to the sternum? 87. Describe the spinal column. 88. Give the structure of the vertebra. Where is the spinal cord placed? 89. What is placed between each vertebra? What is its use?
3790. Another provision for the protection of the brain, which bears convincing proof of the wisdom and beneficence of the Creator, is the antero-posterior, or forward and backward curve of the spinal column. Were it a straight column, standing perpendicularly, the slightest jar, in walking, would cause it to recoil with a sudden jerk; because, the weight bearing equally, the spine would neither yield to the one side nor the other. But, shaped as it is, we find it yielding in the direction of the curves, and thus the force of the shock is diffused.
Fig. 10.
Fig. 10. A vertebra of the neck. 1, The body of the vertebra. 2, The spinal canal. 4, The spinous process, cleft at its extremity. 5, The transverse process. 7, The inferior articulating process. 8, The superior articulating process.
Fig. 11.
Fig. 11. 1, The cartilaginous substance that connects the bodies of the vertebræ. 2, The body of the vertebra. 3, The spinous process. 4, 4, The transverse processes. 5, 5, The articulating processes. 6, 6, A portion of the bony bridge that assists in forming the spinal canal, (7.)
Observation. A good idea of the structure of the vertebræ may be obtained by examining the spinal column of a domestic animal, as the dog, cat, or pig.
91. The PELVIS is composed of four bones; the two in-nom-i-na´ta, (nameless bones,) the sa´crum, and the coc´cyx.
92. The INNOMINATUM, in the child, consists of three pieces. 38 These, in the adult, become united, and constitute but one bone. In the sides of these bones is a deep socket, or depression, like a cup, called the ac-e-tab´u-lum, in which the round head of the thigh-bone is placed.
90. What is said of the curves of the spinal column? What is represented by fig. 10? By fig. 11? How can the structure of the vertebræ be seen? 91. Of how many bones is the pelvis composed? 92. What is said of the innominatum in the child?
93. The SACRUM, so called because the ancients offered it in sacrifices, is a wedge-shaped bone, that is placed between the innominata, and to which it is bound by ligaments. Upon its upper surface it connects with the lower vertebra. At its inferior, or lower angle, it is united to the coccyx. It is concave upon its anterior, and convex upon its posterior surface.
Fig. 12.
Fig. 12. 1, 1, The innominata, (nameless bones.) 2, The sacrum. 3, The coccyx. 4, 4, The acetabulum. a, a, The pubic portion of the innominata. d, The arch of the pubes; e, The junction of the sacrum and lower lumbar vertebra.
94. The COCCYX, in infants, consists of several pieces, which, in youth, become united and form one bone. This is the terminal extremity of the spinal column.
In the adult? Describe the acetabulum. 93. Describe the sacrum. Explain fig. 12. 94. Describe the coccyx.
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 ∫. 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 40 lodged in the glenoid cavity, where it is surrounded by a membranous bag, called the capsular ligament.
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.
Fig. 13.
Fig. 13. 1, The shaft of the humerus. 2, The large, round head that
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