George Simon

The Head and the Neck

This chapter discusses the structure of head and the neck in humans. A pair of rounded ridges is seen passing up the back of the neck in children and young adults, with a pronounced intervening furrow in the middle line. The ridges are formed by the semispinalis capitis muscles, covered by the thin sheet of the upper part of the trapezius muscle. In the adult, the groove between the ridges tends to become obliterated, but the semispinalis muscles are recognized on palpation if the head is extended against resistance. The pharynx is a space that lies behind the nasal cavities, the mouth and tongue, and the larynx. Three portions are, thus, distinguished as the nasal part, the oral part, and the laryngeal part. The shape and proportions of the head and face show striking hereditary differences, and it is mainly by these that an individual is recognized and the likeness of a portrait is appreciated. No two persons are exactly alike but the differences are very slight, as with identical or like twins. The face and head ordinarily show a slight asymmetry, which is mainly because of the effects of asymmetrical facial expressions and possibly also because of slight differences in the size of the two sides of the brain. Around the mouth, differences depend partly on the form of the facial skeleton and partly on the amount of superficial fat present. Gross disturbances of the posture of the neck may affect the growth of the face, as when the head is habitually held on one side on account of pathological shortening of the sternomastoid muscle. That part of the face which is on the side to which the head is inclined fails to grow as large as the other side.

The Human Skeletal Pattern

This chapter reviews the human skeletal pattern. Bone is a connective tissue, the matrix of which consists of bundles of collagenous connective tissue fibres 3–5 μ thick surrounded by an amorphous polysaccharide gel or ground substance in which crystals of a complex calcium phosphate salt are deposited. Two kinds of bones may be distinguished, namely, lamellar bone and fibrous bone. In the teeth, two modified forms of bone are found, namely, dentine and cement. A radiograph is a unique way of visualizing the fine detail of the calcified portions of the bones in the living person because it reveals details of internal structure. Some muscles and tendons are sufficiently dense or bulky to cast a shadow of low density, which are distinguished from the shadow of the skin and other soft tissue structures. An example is the tendo calcaneus. As a rule, they are demonstrated in radiographs taken especially for this purpose better than in those taken to show the bones.

The Upper Limb

This chapter discusses the anatomy and movement of the upper limb. The general form of the shoulder and upper limb is determined primarily by the skeleton, but most of the detail is provided by muscles and tendons. On account of the extensive movements that take place at the joints, the relative positions of the various skeletal structures differ greatly in different postures. Movements of the shoulder girdle ordinarily involve movements both at the shoulder joint and between the shoulder girdle and chest wall. The shoulder girdle movements alter the orientation of the glenoid cavity of the scapula and, thus, modify the position of the limb. The position of the limb, thus, depends both on the position of the girdle in relation to the trunk and on the posture at the shoulder joint. Movements at the elbow joint comprise flexion and extension of the forearm. Flexion is limited by the contact of the soft tissues of the forearm and arm and by contact of the head of the radius against the humerus, extension by the tension of the brachialis muscle, or sometimes by the contact of the olecranon with the olecranon fossa of the humerus.

The Lower Limb

This chapter discusses the anatomy and movement of the lower limb. The general outline of the buttock and thigh is determined by the form of the pelvis and femur, together with the covering muscles and accumulations of fat. The crest of the ilium gives form to the junction of buttock and loin, the symphysis pubis forms the medial end of the groin, while the greater trochanter produces a prominent lateral convexity at the junction of buttock and thigh. The forward curve of the shaft of the femur determines the general form of the thigh. The positions to which the distal end of the femur is displaced by movement at the hip joint lie approximately on the surface of a hemisphere, the radius of which is represented by the length of the femur. The movements are flexion, extension, adduction, and abduction. The general form of the knee is determined by the patella and the condyles of the femur and tibia. The outlines of the skeleton are partially concealed by soft tissues, by masses of fat and to a smaller extent by muscle tendons or muscles. The chapter provides an overview of lower limb lymphatics. The lymphatics of the leg are demonstrated after the injection of a suitable contrast medium into one of the small lymphatic vessels on the dorsum of the foot, which is identified by injecting dye between the webs of the toes.

The Vertebral Column

This chapter describes the vertebral column, which is a flexible structure made up of vertebrae and intervertebral discs. Small alterations of form accompany changes in the distribution of the bodyweight, while greater alterations take place in general movements of the body. The numbers of vertebrae in the various regions into which the vertebral column is subdivided are cervical 7, thoracic 12, lumbar 5, sacral 5, and coccygeal 4. Either the 7th cervical or the 1st lumbar vertebra bears an additional pair of ribs. The cervical ribs are short and only detected on radiological examination, but they are longer and palpable in the supraclavicular fossa of the neck. In a small proportion of subjects, there are only four lumbar vertebrae, while the absence of a 12th rib or nonfusion of the first sacral segment suggests the presence of six lumbar vertebrae. Exceptionally, a half vertebral body may be interposed between the bodies of adjacent vertebrae on one side. In the condition of spina bifida, the neural arches are incomplete dorsally. This bony defect may be accompanied by anomalies of the spinal cord. It is not unusual to find minor degrees of the condition in the sacrum and the neural arch of the 5th lumbar vertebra, and these are usually without significance.

General Anatomy and Radiological Methods

The anatomy of the living subject is studied by the four classical methods of inspection, palpation, percussion, and auscultation. This chapter discusses these four methods. Inspection reveals the proportions and natural posture of the body. As these influence the radiological appearances, the two methods are complimentary. The form of parts of the human skeleton is deduced from inspection. Suitable instruments have been devised that make it possible to examine the interior of all the hollow organs possessing an external opening or communication. The interior of the larynx is examined with a laryngoscope, the larger airways with a bronchoscope or, fiberscope, the alimentary tract with a gastroscope, fiberscope, sigmoidoscope, or colonoscope, the urethra and bladder with a cystoscope, and the rectum or vagina with the aid of a speculum. Palpation gives information about some of the deeper structures that are invisible, for example, the shape of the shaft of the humerus or the size of the uterus. Percussion and auscultation further add to the total anatomical picture by giving functional data such as the state of distension of the bladder whether the heart valves are opening and closing in a normal manner, or whether air is entering or leaving the alveoli or smaller airways evenly throughout both lungs. The newer methods such as isotope studies and ultrasound echo studies help to complete the total anatomical picture.

CHAPTER 6 – The Thorax

Publisher Summary This chapter provides an overview of the thorax. The clavicles on either side of the chest form sinuous ridges at the junction of the thorax and neck. A broad depression lies over the sternum and separates the elevations formed by the pectoralis muscles in the male and by these muscles and the mammary glands in the female. The lower border of the pectoralis muscle forms a curved prominence below the nipple, continuous in the male with the anterior wall of the axilla. The lower end of the depression between the pectoralis major muscles ends below in the broad epigastric fossa. The cardiac impulse in many individuals is shown as a thrust of the heart against the chest wall and is known clinically as the apex beat. It usually lies in the 5th intercostal space generally 9 cm from the middle line. The movements of the upper ribs produce an increase mainly in the anteroposterior diameter, while those of the lower ribs result mainly in an increase of the transverse diameter of the thorax. In inspiration, there is an increase in the girth and in all horizontal diameters of the thorax. The thorax in the female is relatively shorter and more rounded than in the male, and the upper ribs are more movable. This allows for greater movement of this part of the thorax in females, and the movement is especially evident in the later stages of pregnancy.

CHAPTER 7 – The Abdomen

Publisher Summary This chapter discusses the structure of abdomen in humans. The contour of the abdomen varies with the muscular development, obesity, sex, and age of the individual. In the female, the abdomen is relatively broader below the umbilicus so that the waist is more distinct than in the male. The umbilicus is a distinctive landmark situated at a variable level. In the adult, it is usually situated at about the same level as the supracristal plane but is lower when the abdominal wall is protuberant if this condition is because of weakness of the musculature. In the child, it lies relatively nearer the pubis owing to the relatively undeveloped state of the pelvis. In a lean muscular subject, the muscles of the abdominal wall produce distinctive elevations. The rectus abdominis muscle forms an elevation on either side of the medial furrow, which overlies the linea alba. On each side, a curved shallow groove in the abdominal wall, that is, the linea semilunaris, marks the lateral margin of the rectus abdominis muscle. The upper end of the groove reaches the costal margin at the level of the 9th costal cartilage. Protuberance of the abdomen may be because of a poor state of the anterior abdominal wall, for example, in subjects in poor physical condition or in elderly women who have borne many children.