뒤로Chapter 1: The Human Body—An Orientation (Anatomy & Physiology Study Notes)
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Form and Function of Anatomy & Physiology
Definition and Scope
Anatomy is the study of the structure of body parts and their relationships to one another, while physiology is the study of the function of body parts and how they carry out life-sustaining activities. Understanding both is essential for a comprehensive knowledge of the human body.
Anatomy requires knowledge of anatomical terminology and the ability to observe, manipulate, palpate, and auscultate.
Physiology requires understanding basic physical and chemical principles, such as electrical currents, pressure, and movement.
Topics of Anatomy
Gross (macroscopic) anatomy: Study of large, visible structures.
Regional anatomy: Examines all structures in a specific area of the body.
System anatomy: Focuses on one organ system at a time (e.g., cardiovascular, nervous).
Surface anatomy: Studies internal structures as they relate to the overlying skin.
Microscopic anatomy: Structures too small to be seen with the naked eye, including:
Cytology: Study of cells.
Histology: Study of tissues.
Developmental anatomy: Study of anatomical and physiological development throughout life, including embryology (development before birth).
Topics of Physiology
Usually based on organ systems (e.g., renal physiology, cardiovascular physiology).
Often focuses on cellular and molecular levels, emphasizing how chemical reactions in cells drive body functions.
Complementarity of Structure and Function
Anatomy and physiology are inseparable; function always reflects structure. This is known as the principle of complementarity of structure and function: what a structure can do depends on its specific form.
Structural Organization of the Human Body
Levels of Organization
The human body is organized from the smallest chemical level to the entire organism:
Chemical level: Atoms, molecules, and organelles.
Cellular level: Single cells.
Tissue level: Groups of similar cells.
Organ level: Two or more types of tissues working together.
Organ system level: Organs that work closely together.
Organismal level: All organ systems combined to make the whole organism.
Requirements for Life
Necessary Life Functions
To maintain life, the human body must perform several essential functions:
Maintaining boundaries: Separation between internal and external environments (e.g., plasma membranes, skin).
Movement: Movement of body parts (skeletal muscles) and substances (cardiac and smooth muscle).
Responsiveness: Ability to sense and respond to stimuli (e.g., withdrawal reflex, breathing rate).
Digestion: Breakdown of ingested food and absorption of nutrients into the blood.
Metabolism: All chemical reactions in body cells, including catabolism (breakdown) and anabolism (synthesis).
Excretion: Removal of wastes (e.g., urea, carbon dioxide, feces).
Reproduction: Cellular division for growth/repair and production of offspring.
Growth: Increase in size of a body part or the organism as a whole.
Organ Systems Overview
There are 11 organ systems in the human body, each with specialized functions but all working together to maintain life:
Integumentary system
Skeletal system
Muscular system
Nervous system
Endocrine system
Cardiovascular system
Lymphatic/Immune system
Respiratory system
Digestive system
Urinary system
Reproductive system
Interrelationships Among Body Organ Systems
Organ systems work cooperatively to promote the well-being of the entire body. For example, the digestive, respiratory, cardiovascular, and urinary systems interact to supply nutrients and remove wastes.
Survival Needs
Humans require several factors for survival, each in appropriate amounts:
Nutrients: Chemicals for energy and cell building (carbohydrates, proteins, fats, vitamins, minerals).
Oxygen: Essential for energy release from food; survival without oxygen is limited to a few minutes.
Water: Most abundant chemical in the body; necessary for chemical reactions.
Normal body temperature: Required for proper rates of chemical reactions (about 37°C).
Appropriate atmospheric pressure: Needed for adequate breathing and gas exchange in the lungs.
Homeostasis
Definition and Importance
Homeostasis is the maintenance of relatively stable internal conditions despite continuous changes in the environment. It is a dynamic state of equilibrium, maintained by all organ systems, especially the nervous and endocrine systems.
Homeostatic Control Mechanisms
Homeostatic control involves three main components:
Receptor (sensor): Monitors the environment and responds to stimuli.
Control center: Determines the set point, receives input from the receptor, and determines the appropriate response.
Effector: Receives output from the control center and provides the means to respond, either reducing (negative feedback) or enhancing (positive feedback) the stimulus.
Negative Feedback
Negative feedback is the most common homeostatic control mechanism. The response reduces or shuts off the original stimulus, causing the variable to change in the opposite direction of the initial change.
Examples: Regulation of body temperature, regulation of blood glucose by insulin.
Positive Feedback
Positive feedback enhances or exaggerates the original stimulus, often resulting in a cascade or amplifying effect. It usually controls infrequent events that do not require continuous adjustment.
Examples: Enhancement of labor contractions by oxytocin, platelet plug formation and blood clotting.
Homeostatic Imbalance
Disturbance of homeostasis increases the risk of disease and contributes to changes associated with aging. If negative feedback mechanisms are overwhelmed, destructive positive feedback mechanisms may take over (e.g., heart failure).
Anatomical Terms
Anatomical Position and Directional Terms
The standard anatomical position is body erect, feet slightly apart, palms facing forward with thumbs pointing away from the body. Directional terms describe the location of one body structure relative to another, always based on the standard anatomical position.
Orientation and Directional Terms
Directional terms are essential for accurately describing locations and relationships of body parts. The following tables summarize key terms:
Term | Definition | Example |
|---|---|---|
Superior (cranial) | Toward the head end or upper part of a structure or the body; above | The head is superior to the abdomen. |
Inferior (caudal) | Away from the head end or toward the lower part of a structure or the body; below | The navel is inferior to the chin. |
Anterior (ventral) | Toward or at the front of the body; in front of | The breastbone is anterior to the spine. |
Posterior (dorsal) | Toward or at the back of the body; behind | The heart is posterior to the breastbone. |
Term | Definition | Example |
|---|---|---|
Medial | Toward or at the midline of the body; on the inner side of | The heart is medial to the arm. |
Lateral | Away from the midline of the body; on the outer side of | The arms are lateral to the chest. |
Intermediate | Between a more medial and a more lateral structure | The collarbone is intermediate between the breastbone and shoulder. |
Term | Definition | Example |
|---|---|---|
Proximal | Closer to the origin of the body part or the point of attachment of a limb to the body trunk | The elbow is proximal to the wrist. |
Distal | Farther from the origin of a body part or the point of attachment of a limb to the body trunk | The knee is distal to the thigh. |
Superficial (external) | Toward or at the body surface | The skin is superficial to the skeletal muscles. |
Deep (internal) | Away from the body surface; more internal | The lungs are deep to the skin. |
Regional Terms
The body is divided into two major regions:
Axial: Head, neck, and trunk.
Appendicular: Limbs (arms and legs).
Regional terms designate specific areas within these divisions.
Body Planes and Sections
Body planes are imaginary flat surfaces along which the body or structures may be cut for anatomical study. The three most common planes are:
Sagittal plane: Divides the body vertically into right and left parts.
Frontal (coronal) plane: Divides the body vertically into anterior and posterior parts.
Transverse (horizontal) plane: Divides the body horizontally into superior and inferior parts.
Oblique section: Cuts made at angles other than 90° to the vertical plane.
Body Cavities and Membranes
Major Body Cavities
The body contains internal cavities that are closed to the environment, providing protection to organs. There are two main sets of cavities:
Dorsal body cavity: Protects the nervous system; includes the cranial cavity (brain) and vertebral cavity (spinal cord).
Ventral body cavity: Houses internal organs (viscera); includes the thoracic cavity and abdominopelvic cavity, separated by the diaphragm.
Thoracic and Abdominopelvic Cavities
Thoracic cavity: Contains two pleural cavities (each surrounds a lung), the mediastinum (containing the pericardial cavity and other thoracic organs), and the pericardial cavity (encloses the heart).
Abdominopelvic cavity: Subdivided into the abdominal cavity (stomach, intestines, spleen, liver) and pelvic cavity (urinary bladder, reproductive organs, rectum).
Serous Membranes
Serosa (serous membrane) is a thin, double-layered membrane covering surfaces in the ventral body cavity. The parietal serosa lines internal body cavity walls, while the visceral serosa covers internal organs. The layers are separated by a cavity filled with serous fluid, reducing friction.
Pericardium: Associated with the heart.
Pleurae: Associated with the lungs.
Peritoneum: Associated with the abdominopelvic cavity.
Abdominopelvic Quadrants and Regions
The abdominopelvic region is divided for clinical and anatomical purposes:
Quadrants: Right upper (RUQ), left upper (LUQ), right lower (RLQ), left lower (LLQ).
Nine regions: Right hypochondriac, epigastric, left hypochondriac, right lumbar, umbilical, left lumbar, right iliac (inguinal), hypogastric, left iliac (inguinal).
Other Body Cavities
Additional smaller cavities include:
Oral and digestive cavities
Nasal cavity
Orbital cavities
Middle ear cavities
Synovial cavities (joint cavities; not exposed to the environment)
