Frontal bone

“ Fig. 15.—Cranium at birth, showing sutures and fontanelles.
The frontal bone, as its name implies, forms the fore part of the head or forehead. It joins the parietal bones above and the temporal bones on either side. At the lower edge are the supra-orbital arches, each with a supra-orbital notch or foramen on its inner margin for the passage of the supra-orbital vessels and nerve, the nerve most affected in neuralgia. Just above the arches on either side are the superciliary ridges, behind which, between the two tables of the skull, lie the frontal sinuses. ”

“ The Frontal bone, forming the forehead.—The more the frontal bone retires, the lower is the forehead, and the more prominent the face. The more it is vertical or arched, the more the brain seems to be in superposition over the face; rather than lying behind it. By drawing one line from the opening of the ear to the base of the nose, by drawing a second from the most prominent part of the forehead to the insertion of the teeth, and by measuring the inner angle at which these two lines bisect each other, we have the famous facial angle of Camper ”

“ From the appearance of the wound in the top of his head, the fragments of bone being lifted up, the brain protruding from the opening and hanging in shreds upon the hair, it was evident that the opening in the skull was occasioned by some force acting from below, upward, having very much the shape of an inverted funnel, the edges of the scalp everted and the frontal bone extensively fractured, leaving an irregular oblong opening in the skull of two by three and one-half inches. ”

“ The muscle-fibres take origin from the strong craniolateral part of the inner surface of the temporal fascia, from the groove on the temporal bone dorsad of the dorsal root of its zygomatic process, from the whole inner surface of this process and of the zygomatic process of the malar bone, and sometimes also from that part of the frontal bone which lies within the temporal fossa. ”

“ The occipital and frontal muscles, united by a thin aponeurosis, cover the whole upper cranium and are known as the occipito-frontalis muscle. At the back this is attached to the occipital bone, while in front it interlaces with various face muscles. It is a powerful muscle and raises the brows, wrinkles the forehead, and draws the scalp forward. Long hair grows on the skin over it as a further protection against blows upon the skull and sudden variations in temperature. ”

“ The lachrymal (3) is a fairly large bone that forms the anterior border of the orbit. It is bounded laterally by the jugal, anteriorly by the maxilla, and medially by the prefrontals. Its postero-medial border is pierced by a large lachrymal foramen that extends lengthwise through the bone and opens, at its anterior end, into the nasal chamber.
The supraorbital, missing in the skull figured, is a small bone lying in the eyelid close to the junction of the frontal and prefrontal. Being unattached it is usually absent from prepared skulls. ”

“ The limb bones are long, slender, and less curved than those of the other associated human beings (A) , and herein the earliest type is suggested once more. [Pg 62] But the differences occur now in the skull. The brain is as large as in the other subdivision (A) and in modern men. The brain-case is becoming elevated: the brow-ridges are undergoing reduction; this process, commencing at their outer ends, expresses to some extent the degree of reduction in the muscles and bone of the lower jaw. The teeth are smaller and the chin becomes more prominent. ”

“ Among the solid parts of the human frame the bones stand conspicuous. Their use is, to give firmness and shape to the body. Some of them likewise serve as armour, or defense, to guard important parts; thus the skull is admirably contrived to defend the brain; and the spine or backbone is designed, not only to strengthen the body, but to shield that continuation of the brain, called the spinal marrow, from whence originate great numbers of nerves, which pass through convenient openings of this bone, and are distributed to various parts of the body. ”

“ After the brain has been removed, the skin is stripped off a limited area of the skull, and the bone at the place of junction of the sagittal and lambdoid sutures above the occipital foramen is filed away, so that only a point, like a bony outgrowth, is left. ”

“ A very tough skin—a sheathe—surrounds the neck with blood vessels, nerves, muscles, bones, ligaments, fascia, glands great and small, throat and trachea. In bones we find a great canal for spinal cord. It is well and powerfully protected by a strong wall of bone, so no outer pressure can obstruct the flow of passing fluids, to keep vitality supplied by brain forces, but with all the guards given to protect the cord, we find that it can be overcome by impact fluids to such degree as to stop blood and other fluids from supplying lungs and all below. ”

“ A positive strain represents stretching, whilst compression is represented by a negative figure. Direct experimental measurements in a human showed that the strain levels in the parietal bone of the skull are 10 fold lower compared with the tibia [4] . ”

“ And this may possibly be the reason why the bones of the skull, though not exposed to forces such as those which produce, in other bones, dense outer layers including less dense interiors, nevertheless repeat this general trait of bony structure. While, however, it is beyond doubt that some bones are not due to the direct influence of mechanical stress, we may, I think, conclude that mechanical stress initiates bone-formation. ”

“ As a rule the whole thickness of the skull is broken, and, as usual, the inner table suffers most. In infants the bones may be merely indented, the fracture being of the greenstick variety. All degrees of severity are met with, from a simple, localised indentation of the bone, to complete smashing of the skull into fragments. ”

“ If we take a transverse section of the bones of the cranium, we find that they are formed of two very thin layers of bone united by a porous, osseous substance; the external layer is in direct contact with the muscles of the scalp, and the internal layer with the brain. ”

“ In course of time the vertebral column becomes rigid, the head is bent forward, the hips are flexed, and abduction and other movements of the arms are limited. The disease progresses by fits and starts, until all the striped muscles of the body are replaced by bone, and all movements, even those of the jaws, are abolished. ”

“ The parietals and frontals, being membrane bones, are not comparable to the supra-occipital, in the way that the presphenoid and basisphenoid are to the basi-occipital. [20]
The cartilage bones of the occipital segments are derived from the parachordals of the embryonic skull, those of the parietal and frontal segments from the trabeculae. ”

“ As the neck has much to do with the arm, we should keep a living picture of the forms of each bone, how and where it articulates with others, how it is joined by ligaments, what blood vessels, nerves and muscles cross or range with it lengthwise, because to overlook a small nerve and blood vessel you may fail to remove a goitre, and all diseases of the head, face and neck. ”

“ The head, which is covered with cartilage, except for an oval depression for the attachment of the ligamentum teres, one of the ligaments of the hip-joint, and which articulates with the hollow of the acetabulum in the os innominatum, projects considerably upward, inward, and forward from the shaft, the neck varying much in length and angle. It is generally more [Pg 188] horizontal in women than in men and in rickets the great weight on the softened bone tends to press the head down, causing the deformity known as “coxa vera”, in which the neck is almost horizontal. ”

“ The lower extremities resemble the upper very closely in the arrangement of the bones, muscles, arteries, and nerves, though modifications occur, due to the difference in function of the lower limbs. There is one long bone in the upper part or thigh, the femur, and two in the lower part or leg, the tibia and fibula, while over the knee-joint is the patella or knee-cap. The ankle has seven bones and the foot nineteen like the hand. ”

“ The delicate sense of feeling depends on the nervous supply; and the power of clasping and holding on upon the bending or flexor muscles. A bony framework supports all these structures, and runs from the last bone of the sacrum to the tip, and consists of many separate vertebral bones placed in a long series. The first few bones which join on to the sacrum, and form the root of the tail, resemble the back-bone pieces, or vertebræ, to a certain extent. Each has a body, and also processes for jointing with the one before and behind, and a spine also. ”

“ The angle of inclination of the neck of the femur is dependent upon the adjustment of certain forces, namely, the weight of the body, the action of muscles, and the resistance of the bone. The most obvious cause of deviation of the neck from the normal angle is some condition which causes softening of the bone so that it yields under weight-pressure, the most common being partial fractures, rickets, and other diseases of the bone. ”