Anatomy and Physiology

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UNIT 1

Chapter 1: Organization of the Body

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)

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

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

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

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

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
  • 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.)

  • 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.)

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
  • 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.)

  • 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.)

ANATOMICAL POSITION

  • Reference position (Figure 1-4)
  • Body erect with arms at sides and palms forward
  • Head and feet pointing forward

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

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

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

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

BODY REGIONS (cont.)

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

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

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

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

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

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

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

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

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)

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