Humans Body Parts Informations

The superior border is thin, bevelled at the expense of the internal surface, so as .to overlap the lower border of the parietal bone, forming the squam­ous suture. The position and size of this foramen are very variable. It is not always present; sometimes it is situated in the occipital bone or in the suture between the temporal and the occipital. The mastoid portion is continued below into a conical projection, the mastoid process, the size and form of which vary somewhat. This process serves for the attachment of the Sterno-mastoid, ~Jllenius capitis, and 'rl'achelo-mastoid muscles. On the inner side of the mastoid process is a deep groove, the digastric fossa, for the attachment of the Diga"tric muscle; and, running parallel with it, but more in­ternal, the occipital gronee. which lodges the occipital artery.

External to the stylo-mastoid foramen is the auricular fissure, for the auricular branch of the pneumogastric, bounded behind by the mastoid process. Upon the inner side of the mastoid proc­ess is a deep groove, the digastric fossa; and a little more internally the occipital groove, for the occipital artery. At the base of the internal pterygoid plate is a large and somewhat triangular aperture, the foramen lacerum medium, bounded in front by the great wing of the sphenoid, behind by the apex of the petrous portion of the temporal bone, and internally by the body of the sphenoid and basilar proc­ess of the occipital bone: it presents in front the posterior orifice of the Vidian canal; behind, the aperture of the carotid canal. The basilar surface of this open­ing is filled in the recent state by fibro-cartilaginous substance f across its upper or cerebral aspect passes the internal carotid artery. External to this aperture the petro-sphenoidal suture is observed, at the outer termin

The ribs which require especial consideration are five in number-viz. the first, second, tenth, eleventh and twelfth. The first rib is one of the shortest and the most curved of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward. The head is of small size, rounded, and presents only a single articular facet for articulation with the body of the first dorsal vertebra. The neck is narrow and rounded. The tuberosity, thick and prominent, rests on the outer border. There is no angle, but in this situation the rib is slightly bent, with the convexity of the bend upward, so that the head of the bone is directed downward. The upper surface of the shaft is marked by two shallow depressions, separated by a small rough surface for the attachment of the Scalenus anticus muscle-the groove in front of it transmitting the subclavian vein, that behind it the subclavian artery. Between the groove for the subclavian artery and the tuberosi

The arm is that portion of the upper extremity which is situated between the shoulder and the elbow. Its skeleton consists of a single bone, the humerus. The HUMERUS The Humerus is the longest and largest bone of the upper extremity; it presents for examination a shaft and two extremities. The Upper Extremity presents a large, rounded head, joined to the shaft by a constricted   portion, called the neck, and two other eminences, the greater and lesser tuberosities. The head, nearly hemispherical in form/ is' directed upward, inward, and alittle backward, and articulates with the glenoid cavity of the scapula; its surface is smooth and coated with cartilage in the recent state. The circumference of its articular surface is slightly constricted, and is termed the anatomical neck, in con­tradistinction to the constriction which exists below the tuberosities. The latter is called the surgical neck, from its often being the seat of fracture.

The Ulna so called from its forming the elbow is a long bone, prismatic in form, placed at the inner side of the forearm, parallel with the radius. It is the larger and longer of the two bones. Its upper extremity, of great thickness and strength, forms a large part of the articulation of the elbow­joint; it diminishes in size from above downward, its lower extremity being very small, and excluded from the wrist-joint by the interposition of an interarticular fibro-cartilage. It is divisible into a shaft and two extremities. The Upper Extremity, the strongest part of the bone, presents for examination two large, curved processes, the Olecranon process and the Ooronoid process; and two concave, articular cavities, the greater and lesser sigmoid cavities. The Olecranon Process is a large, thick, curved eminence situated at the upper and back part of the ulna. It is curved forward at the summit so as to present a prominent tip which is received into the olecranon fossa in exte

The humerus is almost entirely clothed by the muscles which surround it, and the only parts of this bone which are strictly subcutaneous are small portions of the internal and external condyles. In addition to these, the tuberosities and a part of the head of the bone can be felt under the skin and muscles by which they are covered. Of these the greater tuberosity forms the most prominent bony point of the shoulder, extendinll: beyond the acromion process and covered by the Deltoid muscle. It influences materially the surface form of the shoulder. It is best felt while the arm is lying loosely by the side; if the arm be raised, it recedes from under the finger. The lesser tuberosity, directed forward and inward, is to be felt to the inner side of the greater tuberosity, just below the acromio-clavicular joint. Between the two tuberosities lies the bicipital groove. This can be defined by placing the finger and making firm pressure just internal to the greater tuberosity; then, by ro

A Rib from the middle of the series should be taken in order to study the common characters of the ribs. Each rib presents two extremities, a posterior or vertebral, an anterior or ster­nal, and an intervening portion-the body or shaft.The posterior or vertebral extremity presents for examination a head, neck, and tuberosity. The head is marked by a kidney-shaped articular sur­face, divided by. a horizontal ridge into two facets for articulation with the costal cavity formed by the junction of the bodies of two contiguous dorsal vertebrse ; the upper facet i- small, the inferior one of larger size; the ridge separating them serves for the attachment of the interarticular ligament. The neck is that flat­tened portion of the rib which extends outward from the head; it is about an inch long, and is p aced in front of the transverse process of the lower of the two vertebrte with 'hieh the head articulates. Its anterior surface is flat and smooth, its posterior roueh f r the attac

Emerging from the upper end of the valve of Vieussens. the nerve is directed outward across the superior peduncle of the cerebellum, and then winds forward round the outer side of the crus cerebri, immediately above the pons Varolii, pierces the dura mater in the free border of the tentorium cerebel1i. just behind, and external to, the posterior clinoid process, and passes forward in the outer wall of the cavernous sinus, between the third nerve and the ophthalmic division of the fifth. It crosses the third nerve and enters the orbit through the sphe¬noidal fissure. It now becomes the highest of all the nerves, lying at the inner extremity of the fissure internal to the frontal nerve. In the orbit it passes inward, above the origin of the Levator palpebrse, and finally enters the orbital surface of the Superior oblique muscle. In the outer wall of the cavernous sinus this nerve is not infrequently blended with the ophthalmic division of the fifth. Branches of Communication.-In th

The Fifth or Trifacial Nerve (n. trigeminus) is the largest cranial nerve. It resembles a spinal nerve (1) in arising by two roots; (2) in having a ganglion developed on its posterior root; and (3) in its function, since it is a compound nerve. It is the great sensory nerve of the head and face and the motor nerve of the muscles of mastication. Its upper two divisions are entirely sensory; the third division is partly sen.sory and partly motor. It arises by two roots: of these the anterior is the smaller, and is the motor root; the posterior, the larger and sensory. Its superficial origin is from the side of the pons Varolii, nearer to the upper than the lower border. The smaller root consists of three or four bundles; the larger root consists of numerous bundles of fibres, varying in number from,seventy to a hundred. The two roots are separated from one another by a few of the transverse fibres of the pons. 'I'he deep origin of the larger or sensory root is chiefly from a

THE ANASTOMOTICA accompanies the long saphenous nerve to the inner side of the thigh. It passes between the Sartorius and Gracilis muscles, and, piercing the fascia lata, is distrib¬uted to the integument of the upper and inner part of the leg, anastomosing with the inferior internal articular. The deep branch descends in the substance of the Vastus internus, lying in front of the tendon of the Adductor magnus, to the inner side of the knee, where it anastomoses with the superior internal articular artery and anterior recurrent branch of the anterior tibial. A branch from this vessel crosses outward above the articular surface of the femur, forming an anastomotic arch with the superior external articular artery, and supplies branches to the knee-joint. Popliteal Artery. The popliteal artery commences at the termination of the femoral at the opening in the Adductor magnus, and, passing obliquely downward and outward behind the knee-joint to the lower border of the Pop

Dissection.-A vertical incision about eight inches in length should be made along the back part of the knee-joint, connected above and below by a transverse incision from the inner to the outer side of the limb. The flaps of integument included between these incisions should be reflected in the direction.  Boundaries.-The popliteal space, or the ham, is a lozenge-shaped space, widest at the back part of the knee-joint, and deepest above the articular end of the femur. It is bounded externally, above the joint; by the Biceps, and, below the joint, by the Plantaris and external head of the Gastrocnemius. Internally, above the joint, by the Semimembranosus, Semitendinosus, Gracilis, and Sartorius; below the joint. by the inner head of the Gastrocnemius.  Above, it is limited by the apposition of the inner and outer hamstring muscles; below, by the junction of the two heads of the Gastrocnemius. The floor is formed by the lower part of the posterior surface of the shaft of the femu