Atlas of Neuroanatomy for Communication Science and Disorders (eBook)

2 General Anatomical Concepts

2.1 The Human Body (Proportions, Surface Areas, and Body Weights)

2.1.1 Change in Body Proportions during Growth

While the head height in embryos at 2 months’ gestation is equal to approximately half the total body length, it measures approximately one-fourth of the body length in newborns, one-sixth in a 6-year-old child, and one-eighth in an adult (Fig. 2.1).

2.1.2 Normal Body Proportions

In an adult, the midpoint of the total body height lies approximately at the level of the pubic symphysis, that is, there is a 1:1 ratio of upper to lower body height at that level (Fig. 2.2). The pelvis accounts for one-fifth of the upper body height, the thorax for two-fifths, and the head and neck for two-fifths. The lower body height is distributed equally between the thigh and leg (plus heel) at the joint space of the knee.

2.1.3 Span of the Outstretched Arms

The arm span from fingertip to fingertip (= 1 fathom) is slightly greater than the body height (~ 103% in women and 106% in men) (Fig. 2.3).

2.1.4 Selected Body Measurements in the Standing and Sitting Human Being (Unclothed, 16–60 Years of Age)

The percentile values indicate what percentage in a population group are below the value stated for a particular body measurement. For example, the 95th percentile for body height in males 16 to 60 years of age is 184.1 cm, meaning that 95% of this population group are shorter than 184.1 cm, and 5% are taller (Fig. 2.4, Table 2.1).

2.1.5 Distribution of Body Surface Area in Adults, Children, and Infants

According to the “rule of nines” described by Wallace (1950), the body surface area of adults over about 15 years of age (a) can be divided into units that are a multiple of 9%: the head and each arm account for 9% each, the front and back of the trunk and each leg account for 18% (2 × 9) each, and the external genitalia comprise 1%. In children (b) and infants (c), the rule of nines must be adjusted for age. Note: The rule of nines can be used in burn victims to provide a quick approximation of the area of skin that has been burned (Fig. 2.5).

2.1.6 Hand Area Rule

The percentage of the body surface affected by burns can be accurately estimated with the hand area rule, which states that the area of the patient's hand is approximately 1% of the patient's own total body surface area. The hand rule also applies to children, whose hands and total surface area are both proportionately smaller than in adults (Fig. 2.6).

2.1.7 Dependence of Relative Body Surface Area (Skin Surface Area) on Age, and Consequences

For progressively larger solid bodies, the surface area increases as the square of the radius, but the volume increases as the cube of the body's radius. Because of this basic geometrical relationship, smaller animals generally have a larger relative surface area than larger animals. A higher ratio of surface area to volume causes smaller animals to radiate relatively more body heat. As a result, small ani mals like mice and children tend to have a higher metabolic rate than larger animals like elephants and human adults (Table 2.2).

2.1.8 Body Mass Index

In anthropometry, the body mass index (BMI) has become the international standard for evaluating body weight because it correlates relatively well with total body fat. BMI is defined as the body weight in kilograms divided by the square of the height in meters:

Body mass and body weight are important to practitioners of speech–language pathology when significant weight loss caused by swallowing disorders is related to malnutrition. Under these circumstances, decisions on assessment and treatment of swallowing disorders must be undertaken (Fig. 2.7).

2.2 The Structural Design of the Human Body

2.2.1 Location of the Internal Organs

Lateral view (Fig. 2.8).

2.2.2 Regional Subdivisions of the Body

2.2.3 Functional Subdivision by Organ Systems

2.2.4 Serous Cavities and Connective Tissue Spaces

Organs and organ systems are embedded either in serous cavities or in connective tissue spaces of varying size. A serous cavity is a fully enclosed potential space that is lined by a shiny membrane (serosa) and contains a small amount of fluid. The serosa consists of two layers that are usually apposed (both layers are not necessarily in direct contact, as in the abdominal cavity): a visceral layer that directly invests the organ, and a parietal layer that lines the wall of the serous cavity.

2.2.5 Selected Planes of Section Through the Human Body Superior View

See Fig. 2.9 (see also Chapter 2.4).

2.3 Body Surface Anatomy

2.3.1 Body Surface Anatomy of the Female (Anterior View)

Body surface anatomy deals with the surface anatomy of the living subject (Fig. 2.10). It plays an important role in classic methods of examination (inspection, palpation, percussion, auscultation, function testing), and so it has particular significance in clinical examination courses.

2.3.2 Body Surface Anatomy of the Female (Posterior View)

See Fig. 2.11.

2.3.3 Body Surface Anatomy of the Male (Anterior View)

See Fig. 2.12.

2.3.4 Body Surface Anatomy of the Male (Posterior View)

See Fig. 2.13.

2.4 Terms of Location and Direction, Cardinal Planes and Axes

2.4.1 General Terms of Location and Direction

See Table 2.3.

2.4.2 The...