Introduction to Anatomy & Physiology

Definition and Scope

• Anatomy is the study of the structure of body parts and their relationships to one another.

• Physiology is the study of the function of body parts and how they work to carry out life-sustaining activities.

• The principle of complementarity states that function always reflects structure; what a structure can do depends on its specific form.

Subdivisions of Anatomy

• Gross (macroscopic) anatomy: Study of large body structures visible to the naked eye.

  • Regional anatomy: All structures in a particular region (e.g., abdomen).

  • Systemic anatomy: Structures studied by system (e.g., cardiovascular system).

  • Surface anatomy: Study of internal structures as related to the overlying skin.

• Microscopic anatomy: Structures too small to be seen with the naked eye.

  • Cytology: Study of cells.

  • Histology: Study of tissues.

• Developmental anatomy: Structural changes throughout life.

  • Embryology: Development before birth.

• Specialized branches:

  • Pathological anatomy: Structural changes caused by disease.

  • Radiographic anatomy: Internal structures visualized by imaging techniques.

  • Molecular biology: Structure of biological molecules.

Subdivisions of Physiology

• Often focuses on specific organ systems (e.g., renal, cardiovascular physiology).

• Frequently examines events at cellular and molecular levels.

Levels of Structural Organization

Hierarchy of Organization

• Chemical level: Atoms combine to form molecules; molecules form organelles.

• Cellular level: Cells are the smallest units of living things.

• Tissue level: Groups of similar cells with a common function.

• Organ level: Structures composed of at least two tissue types performing specific functions.

• Organ system level: Organs working together for a common purpose.

• Organismal level: The living human being; sum total of all structural levels working together.

The Eleven Organ Systems

Requirements for Life

Necessary Life Functions

• Maintaining boundaries: Separation between internal and external environments (e.g., skin, cell membranes).

• Movement: Locomotion and movement of substances within the body.

• Responsiveness (Irritability): Ability to sense and respond to stimuli.

• Digestion: Breakdown of ingested food into simple molecules.

• Metabolism: All chemical reactions in the body.

  • Anabolism: Building up substances.

  • Catabolism: Breaking down substances.

• Excretion: Removal of wastes from the body.

• Reproduction: Cellular (mitosis) and organismal (offspring) reproduction.

• Growth: Increase in size of a body part or the organism as a whole.

Survival Needs

• Nutrients: Chemicals for energy and cell building (carbohydrates, proteins, fats, minerals, vitamins).

• Oxygen: Essential for energy release (cellular respiration).

• Water: Most abundant chemical in the body; environment for metabolic reactions.

• Normal body temperature: Necessary for proper metabolic reaction rates.

• Atmospheric pressure: Required for adequate breathing and gas exchange in the lungs.

Homeostasis and Feedback Mechanisms

Definition and Importance

• Homeostasis is the maintenance of a stable internal environment despite external changes.

• Essential for normal body functioning and sustaining life.

Homeostatic Control Mechanisms

• Variable: The factor or event being regulated.

• Receptor: Detects changes (stimuli) and sends information to the control center.

• Control center: Determines set point, analyzes input, and determines response.

• Effector: Carries out the response to return the variable to the set point.

• The response feeds back to influence the effect of the stimulus (either reducing or enhancing it).

Types of Feedback

• Negative feedback: Most common; reduces or shuts off the original stimulus (e.g., regulation of body temperature, blood glucose).

• Positive feedback: Enhances or exaggerates the original stimulus (e.g., blood clotting, labor contractions).

Homeostatic Imbalance

• Disturbance of homeostasis increases risk of disease and may contribute to changes associated with aging.

Anatomical Terminology

Anatomical Position and Directional Terms

• Anatomical position: Body erect, feet slightly apart, palms facing forward, thumbs pointing away from the body.

• Directional terms describe the location of one body part relative to another (e.g., superior/inferior, anterior/posterior, medial/lateral).

Regional Terms

• Axial region: Head, neck, trunk.

• Appendicular region: Limbs (arms and legs).

• Specific regional terms designate precise areas within these divisions (e.g., brachial for arm, femoral for thigh).

Body Planes and Sections

• Sagittal plane: Divides body into right and left parts.

  • Midsagittal (median): Lies on the midline.

  • Parasagittal: Not on the midline.

• Frontal (coronal) plane: Divides body into anterior and posterior parts.

• Transverse (horizontal) plane: Divides body into superior and inferior parts.

• Sections: Cuts made along a plane to observe internal structures.

Table: Orientation and Directional Terms

Body Cavities and Membranes

Major Body Cavities

• Dorsal body cavity: Protects the nervous system; includes:

  • Cranial cavity: Contains the brain.

  • Vertebral (spinal) cavity: Contains the spinal cord.

• Ventral body cavity: Houses internal organs (viscera); includes:

  • Thoracic cavity: Contains pleural cavities (lungs), mediastinum (heart, esophagus, trachea), and pericardial cavity (heart).

  • Abdominopelvic cavity: Separated from thoracic by diaphragm; includes:

    • Abdominal cavity: Digestive organs, spleen, etc.

    • Pelvic cavity: Urinary bladder, reproductive organs, rectum.

Serous Membranes

• Double-layered membranes lining ventral body cavity and covering organs.

• Parietal serosa: Lines cavity walls.

• Visceral serosa: Covers organs.

• Serous fluid between layers reduces friction.

• Named for associated organs (e.g., pericardium for heart, pleura for lungs, peritoneum for abdominopelvic organs).

Abdominopelvic Regions and Quadrants

• Abdominopelvic cavity can be divided into four quadrants or nine regions for anatomical reference.

• Four quadrants: Right upper, left upper, right lower, left lower.

• Nine regions: Right/left hypochondriac, epigastric, right/left lumbar, umbilical, right/left iliac (inguinal), hypogastric (pubic).

Other Body Cavities

• Smaller cavities (mostly in the head) include oral, nasal, orbital, middle ear, and synovial cavities (joint spaces).

Example: Application of Anatomical Terms

• When describing pain in the abdomen, a physician may refer to the right lower quadrant or the left iliac region to specify the location.

Additional info: The above notes expand on the original outline by providing definitions, examples, and context for each major concept, as would be expected in a mini-textbook summary for introductory Anatomy & Physiology.