Organization of the Human Body
Organization of the Human Body
Anatomy and Physiology Overview
Anatomy: The study of the structure of the body parts and their relationships to one another.
Gross / Macroscopic Anatomy: The study of body structures that can be seen with the naked eye.
Regional Anatomy: All the structures in a particular area of the body (e.g., muscles, bones).
Systemic Anatomy: Body structures are studied system by system (e.g., cardiovascular system).
Surface Anatomy: The study of internal structures as they relate to the overlying skin.
Microscopic Anatomy: Study of body structures at the microscopic level.
Cytology: The study of individual cells.
Histology: The study of tissues, groups of cells that work together to perform a particular function.
Developmental Anatomy: The study of structural changes from conception to adulthood.
Embryology: The study of development before birth.
Using Anatomy Clinically:
Observation: Visual examination of the body.
Manipulation: Physical handling to assess structures.
Palpation: Feeling internal structures with the hands.
Auscultation: Listening to the sounds made by internal organs.
Physiology: The study of the function of the body parts.
Pathology: The study of diseases and their effects on the body.
Organization of Living Things
Levels of Biological Organization:
Chemical Level: Atoms combine to form molecules.
Cellular Level: Cells are made up of molecules.
Tissue Level: Tissues consist of similar types of cells.
Organ Level: Organs are made up of different types of tissues.
Organ System Level: Organ systems consist of different organs that work together closely.
Organismal Level: An individual living entity (e.g., human).
Characteristics of Life
Necessary Life Functions: Characteristics that differentiate living from nonliving organisms:
Metabolism: The sum of all chemical reactions that occur in the body.
Anabolism: Synthesis of complex molecules from simpler ones.
Catabolism: Breakdown of complex substances into simpler ones.
Responsiveness: Ability to detect and respond to stimuli.
Movement: Activities at the organismal and cellular levels.
Digestion: Breakdown of food into absorbable units.
Growth: Increase in size or number of cells.
Differentiation: The process by which cells become specialized.
Reproduction: Formation of new cells or new individuals.
Maintaining Boundaries: Separation of internal from external environments.
Survival Needs
Essential for human survival:
Nutrients: Chemicals for energy and cell building.
Oxygen: Required for metabolic processes.
Water: Most abundant chemical in the body, vital for chemical reactions and environment.
Normal Body Temperature: Necessary for metabolic reactions; typically around 37°C (98.6°F).
Appropriate Atmospheric Pressure: Necessary for proper breathing and gas exchange in the lungs.
Organ Systems
There are 12 organ systems in the human body:
Integumentary System: Protects deeper tissues, synthesizes vitamin D.
Includes skin, nails, hair.
Skeletal System: Supports body organs and provides framework for muscles.
Composed of bones, joints.
Muscular System: Allows manipulation and locomotion, produces heat.
Composed of skeletal muscles.
Nervous System: Fast-acting control system; responds to stimuli.
Composed of brain, nerves, spinal cord.
Endocrine System: Glands secrete hormones regulating processes.
Includes glands like the thyroid, pancreas, adrenal glands.
Cardiovascular System: Blood vessels transport blood; the heart pumps blood.
Lymphatic System/Immunity: Returns fluid to bloodstream; involved in immunity.
Includes lymph nodes, spleen.
Respiratory System: Supplies body with oxygen and removes carbon dioxide.
Composed of lungs, trachea.
Digestive System: Breaks down food for absorption; eliminates indigestible food.
Includes stomach, intestines.
Urinary System: Eliminates nitrogenous wastes; regulates water and electrolytes.
Composed of kidneys, bladder.
Male Reproductive System: Produces sperm and male hormones.
Includes testis, penis.
Female Reproductive System: Produces eggs; site for fetal development.
Includes ovaries, uterus, mammary glands.
Homeostasis
Homeostasis: The body's ability to maintain a stable internal environment despite changes in external conditions.
Mechanisms of Homeostasis Regulation:
Negative-Feedback Mechanism: Control system that reduces the effect of a stimulus; involves:
Receptors: Detect changes in variables.
Control Center: Analyzes input and determines response.
Effectors: Execute the response to restore homeostasis.
Positive-Feedback Mechanism: Enhances the original stimulus until a climax is reached; not commonly used to maintain homeostasis.
Directional Terms
Anterior (Ventral): Toward the front of the body.
Posterior (Dorsal): Toward the back of the body.
Superior (Cranial): Toward the head or upper part.
Inferior (Caudal): Away from the head or lower part.
Medial: Toward the midline of the body.
Lateral: Away from the midline of the body.
Intermediate: Between a more medial and a more lateral structure.
Proximal: Closer to the origin of the body part.
Distal: Farther from the origin of the body part.
Superficial (External): Toward or at the body surface.
Deep (Internal): Away from the body surface.
Body Cavities
Dorsal Body Cavity: Comprises two parts:
Cranial Cavity: Contains the brain.
Spinal (Vertebral) Cavity: Contains the spinal cord.
Ventral Body Cavity: Divided into thoracic and abdominopelvic cavities:
Thoracic Cavity:
Contains mediastinum.
Contains pleural cavities (lungs) and pericardial cavity (heart).
Abdominopelvic Cavity:
Abdominal Cavity: Contains digestive organs (liver, stomach, intestines).
Pelvic Cavity: Contains urinary bladder and reproductive organs.
Quadrants and Regions
The abdominopelvic cavity can be divided into four quadrants using transverse and midsagittal planes:
Right Upper Quadrant (RUQ).
Left Upper Quadrant (LUQ).
Right Lower Quadrant (RLQ).
Left Lower Quadrant (LLQ).
It can also be organized into nine regions:
Epigastric Region: Located above the stomach.
Umbilical Region: Around the navel.
Hypogastric (Pubic) Region: Below the stomach.
Left and Right Hypochondriac Regions: Flanking the epigastric region.
Left and Right Lumbar Regions: Flanking the umbilical region.
Left and Right Iliac Regions: Flanking the hypogastric region.
Other Body Cavities
Additionally described cavities include:
Oral and Digestive Cavities: Encompass the mouth.
Nasal Cavity: Contains the nasal structures.
Orbital Cavities: Contain the eyes.
Middle Ear Cavities: Contain the structures of hearing.
Synovial Cavities: Fluid-filled spaces in joints.
Serous Membranes
These membranes line and enclose the thoracic and abdominopelvic cavities:
Parietal Serosa: Lines the cavity walls.
Visceral Serosa: Covers the organs.
Types of serous membranes include:
Pleura: Surrounds the lungs.
Pericardium: Surrounds the heart.
Peritoneum: Surrounds abdominal organs.
The structure of serous membranes can be likened to a balloon:
The outer balloon wall is comparable to parietal serosa, the inner wall equates to visceral serosa, and the space between them represents the serous cavity.