Chapter 001

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Chapter 1: Organization of the Body

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SCIENCE AND SOCIETY

Science involves logical inquiry based on experimentation (Figure 1-1) Hypothesis: idea or principle to be tested in experiments Experiment: series of tests of a hypothesis; a controlled

experiment eliminates biases or outside influences Theory: a hypothesis that has been proved by experiments to

have a high degree of confidence Law: a theory that has an unusually high level of confidence

The process of science is active and changing as new experiments add new knowledge

Science is affected by culture and culture is affected by society

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ANATOMY AND PHYSIOLOGY

Anatomy and physiology are branches of biology concerned with the form and functions of the body

Anatomy: science of the structure of an organism and the relations of its parts Gross anatomy: study of the body and its parts

that relies only on what the eye can see as a tool for observation (Figure 1-2)

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ANATOMY AND PHYSIOLOGY (cont.)

Microscopic anatomy: study of body parts with a microscope Cytology: study of cells Histology: study of tissues

Developmental anatomy: study of human growth and development

Pathological anatomy: study of diseased body structures

Systemic anatomy: study of the body by systems

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ANATOMY AND PHYSIOLOGY (cont.)

Physiology: science of the functions of organisms; subdivisions named by: Organism involved: human or plant physiology Organizational level: molecular or cellular

physiology Systemic function: respiratory physiology,

neurophysiology, or cardiovascular physiology

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LANGUAGE OF SCIENCE AND MEDICINE

Scientific terms are often based on Latin or Greek word parts

A terminology tool is provided in the pull-out section near the front of this textbook

Terminologia Anatomica (TA) and Terminologia Histologica (TH) Official lists of anatomical terms (TA, gross anatomy; TH,

microscopic anatomy) Terms listed in Latin, in English, and by number Avoids use of eponyms (terms based on a person’s name)

Physiology terms do not have an official list but follow the same principles as TA and TH

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CHARACTERISTICS OF LIFE

A single criterion may be adequate to describe life, such as: Autopoiesis: living organisms are self-organized and self-

maintaining Cell theory: if the entity is made of one or more cells, it is alive

Characteristics of life considered most important in human beings are summarized in Table 1-1

Metabolism: sum total of all physical and chemical reactions occurring in the living body

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LEVELS OF ORGANIZATION

Chemical level: basis for life (Figure 1-3) Organization of chemical structures separates living material

from nonliving material Organization of atoms, molecules, and macromolecules

results in living matter—a gel called cytoplasm Organelle level

Chemical structures organized to form organelles that perform individual functions

Functions of the organelles allow the cell to live Dozens of organelles have been identified, including:

• Mitochondria• Golgi apparatus• Endoplasmic reticulum

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Cellular level Cells: smallest and most numerous units that

possess and exhibit characteristics of life Each cell has a nucleus surrounded by

cytoplasm within a limiting membrane Cells differentiate to perform unique functions

LEVELS OF ORGANIZATION (cont.)

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Tissue level Tissue: an organization of similar cells

specialized to perform a certain function Tissue cells are surrounded by nonliving matrix Four major tissue types

• Epithelial• Connective• Muscle• Nervous

LEVELS OF ORGANIZATION (cont.)

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LEVELS OF ORGANIZATION (cont.)

Organ level Organ: organization of several different kinds

of tissues to perform a specific function Organs represent discrete and functionally

complex operational units Each organ has a unique size, shape,

appearance, and placement in the body

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System level Systems: most complex organizational units of the body System level involves varying numbers and kinds of

organs arranged to perform complex functions (Table 1-2):

• Support and movement• Communication, control, and integration• Transportation and defense• Respiration, nutrition, and excretion• Reproduction and development

LEVELS OF ORGANIZATION (cont.)

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Organism level The living human organism is greater than the

sum of its parts All the components interact to allow the human

being to survive and flourish

LEVELS OF ORGANIZATION (cont.)

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ANATOMICAL POSITION

Reference position (Figure 1-4) Body erect with arms at sides and palms

forward Head and feet pointing forward

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ANATOMICAL POSITION (cont.)

Bilateral symmetry: a term meaning that right and left sides of the body are mirror images Bilateral symmetry confers balanced proportions Remarkable correspondence of size and shape between

body parts on opposite sides of the body Ipsilateral structures are on the same side of the body in

anatomical position Contralateral structures are on opposite sides of the

body in anatomical position

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BODY CAVITIES

Ventral body cavity (Figure 1-5; Table 1-3) Thoracic cavity

• Right and left pleural cavities• Mediastinum

Abdominopelvic cavity• Abdominal cavity• Pelvic cavity

Dorsal body cavity Cranial cavity Spinal cavity

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BODY REGIONS

Axial subdivision (Figure 1-6; Table 1-4) Head Neck Torso, or trunk, and its subdivisions

Appendicular subdivision Upper extremity and subdivisions Lower extremity and subdivisions

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BODY REGIONS (cont.)

Abdominal regions (Figure 1-7) Right hypochondriac region Epigastric region Left hypochondriac region Right lumbar region Umbilical region Left lumbar region Right iliac (inguinal) region Hypogastric region Left iliac (inguinal) region

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BODY REGIONS (cont.)

Abdominopelvic quadrants (Figure 1-8) Right upper quadrant Left upper quadrant Right lower quadrant Left lower quadrant

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TERMS DESCRIBING BODY STRUCTURE

Directional terms (Figure 1-9) Superior and inferior Anterior (ventral) and posterior (dorsal) Medial and lateral Proximal and distal Superficial and deep

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TERMS DESCRIBING BODY STRUCTURE (cont.)

Terms related to organs Lumen (luminal) Central and peripheral Medullary (medulla) and cortical (cortex) Apical (apex) and basal (base)

Many directional terms are listed inside the front cover of the textbook

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BODY PLANES AND SECTIONS

Planes are lines of orientation along which cuts or sections can be made to divide the body, or a body part, into smaller pieces (Figures 1-9 and 1-10)

The three major planes lie at right angles to each other Sagittal plane runs front to back; sections through this

plane divide the body (or body part) into right and left sides

• If section divides the body (or part) into symmetrical right and left halves, the plane is called midsagittal or median sagittal

Frontal (coronal) plane runs lengthwise (side to side) and divides the body (or part) into anterior and posterior portions

Transverse (horizontal) plane is a crosswise plane that divides the body (or part) into upper and lower parts

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INTERACTION OF STRUCTURE AND FUNCTION

Complementarity of structure and function is an important and unifying concept in the study of anatomy and physiology

Anatomical structures often seem designed to perform specific functions because of their unique size, shape, form, or body location

Understanding the interaction of structure and function helps integrate otherwise isolated factual information

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HOMEOSTASIS

Term homeostasis coined by American physiologist Walter B. Cannon

Homeostasis is used to describe the relatively constant states maintained by the body; internal environment around body cells remains constant (Figure 1-13)

Body adjusts important variables from a normal set point in an acceptable or normal range

Examples of homeostasis: Temperature regulation Regulation of blood carbon dioxide level Regulation of blood glucose level

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HOMEOSTATIC CONTROL MECHANISMS

Devices for maintaining or restoring homeostasis by self-regulation through feedback control loops

Basic components of control mechanisms Sensor mechanism: specific sensors detect and react to any

changes from normal Integrating, or control, center: information is analyzed and

integrated; if needed, a specific action is then initiated Effector mechanism: effectors directly influence controlled

physiological variables Feedback: process of information about a variable constantly

flowing back from the sensor to the integrator

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HOMEOSTATIC CONTROL MECHANISMS (cont.)

Negative feedback control systems Are inhibitory Stabilize physiological variables Produce an action opposite to the change that

activated the system Are responsible for maintaining homeostasis Are much more common than positive

feedback control systems

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HOMEOSTATIC CONTROL MECHANISMS (cont.)

Positive feedback control systems Are stimulatory Amplify or reinforce the change that is occurring Tend to produce destabilizing effects and disrupt

homeostasis Bring specific body functions to swift completion

Feed-forward control systems occur when information flows ahead to another process or feedback loop to trigger a change in anticipation of an event that will follow

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HOMEOSTATIC CONTROL MECHANISMS (cont.)

Levels of control (Figure 1-14) Intracellular control

• Regulation within cells• Genes or enzymes can regulate cell processes

Intrinsic control (autoregulation)• Regulation within tissues or organs• May involve chemical signals• May involve other “built in” mechanisms

Extrinsic control• Regulation from organ to organ• May involve nerve signals• May involve endocrine signals (hormones)

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CYCLE OF LIFE: LIFE SPAN CONSIDERATIONS

Structure and function of body undergo changes over the early years (developmental processes) and late years (aging processes)

Infancy and old age are periods when the body functions least well

Young adulthood is the period of greatest homeostatic efficiency

Atrophy: term to describe the wasting effects of advancing age