Introduction to Anatomy, Physiology, and the Chemical Basis of Life

Chapter 1: The Human Body: An Orientation

Anatomy and Physiology Defined

Anatomy and physiology are two closely related branches of science that study the human body. Anatomy focuses on the structure of body parts and their relationships, while physiology examines how these structures function.

• Anatomy: The study of body structure and the relationships among structures.

• Physiology: The study of how body structures function.

Levels of Structural Organization

The human body is organized into six hierarchical levels, each building upon the previous one:

• Chemical level: Atoms and molecules, the smallest units of matter.

• Cellular level: Molecules combine to form cells, the basic structural and functional units of life (e.g., muscle cells, nerve cells, epithelial cells).

• Tissue level: Groups of similar cells and their surrounding materials form tissues. Four basic types: epithelial, connective, muscular, and nervous tissue.

• Organ level: Different types of tissues join to form organs (e.g., heart, lungs, kidneys, stomach).

• Organ system level: Related organs with a common function form organ systems (e.g., digestive system includes mouth, intestines, liver, gallbladder, pancreas).

• Organismal level: All organ systems working together constitute a living individual.

Body Cavities and Membranes

The body contains several cavities that house and protect internal organs. These cavities are lined by membranes that provide protection and lubrication.

• Thoracic cavity (chest cavity): Formed by ribs, muscles, sternum, and thoracic vertebrae. Contains:

  • Pericardial cavity: Surrounds the heart.

  • Pleural cavities (2): Surround each lung.

  • Mediastinum: Central compartment between the lungs (contains trachea, esophagus).

• Abdominopelvic cavity: Divided into:

  • Abdominal cavity: Contains stomach, spleen, liver, gallbladder, small and large intestines, pancreas.

  • Pelvic cavity: Contains urinary bladder, internal reproductive organs, and rectum.

• Dorsal cavity: Includes cranial cavity (protects the brain) and vertebral canal (contains the spinal cord).

• Ventral cavity: Includes thoracic and abdominopelvic cavities.

Serous Membranes

• Serous membrane: Thin, slippery membrane covering the viscera (organs) in the thoracic and abdominopelvic cavities.

• Consists of two layers:

  • Parietal layer: Lines the cavity walls.

  • Visceral layer: Covers the organs.

• The space between layers contains serous fluid for lubrication.

• Types: Pleura (lungs), Pericardium (heart), Peritoneum (abdominal organs).

Body Sections and Planes

Body sections are cuts made along specific planes to study internal structures.

• Frontal (coronal) plane: Divides the body into anterior (front) and posterior (back) portions.

• Transverse (horizontal) plane: Divides the body into superior (upper) and inferior (lower) portions.

• Oblique section: Passes through the body at an angle.

• Sagittal section: Divides the body into right and left portions.

  • Midsagittal: Equal right and left halves.

  • Parasagittal: Unequal right and left portions.

Basic Life Processes

Six essential processes distinguish living organisms from non-living things:

• Metabolism: Sum of all chemical processes in the body.

  • Catabolism: Breakdown of complex molecules.

  • Anabolism: Building up of complex molecules from simpler ones.

• Responsiveness: Ability to detect and respond to changes (e.g., sound, light).

• Movement: Motion of the whole body or parts of the body.

• Growth: Increase in body size due to cell number or size.

• Differentiation: Development of a cell from an unspecialized to a specialized state (e.g., stem cells becoming specialized cells).

• Reproduction: Formation of new cells (mitosis) or new individuals (meiosis).

Homeostasis

Homeostasis is the maintenance of a stable internal environment. It is essential for the survival and function of cells.

• Body fluids: Watery solutions containing dissolved chemicals inside and outside cells.

  • Intracellular fluid (ICF): Fluid within cells.

  • Extracellular fluid (ECF): Fluid outside cells, including:

    • Interstitial fluid: ECF between cells and tissues.

    • Blood plasma: ECF within blood vessels.

Feedback Systems

Homeostasis is maintained by feedback systems that monitor and regulate body conditions.

• Three basic components:

  • Receptor: Detects changes and sends input to the control center.

  • Control center: (Usually the brain) Sets the range of values, evaluates input, and generates output commands.

  • Effector: Receives output and produces a response to restore balance.

Body Positions and Directional Terms

• Anatomical position: Upright, facing forward, feet flat, arms at sides, palms facing forward.

• Prone: Lying face down.

• Supine: Lying face up.

Directional Terms

• Anterior (ventral): Near the front.

• Posterior (dorsal): Near the back.

• Superior: Toward the head.

• Inferior: Away from the head.

• Proximal: Closer to the point of attachment.

• Distal: Farther from the point of attachment.

• Lateral: Farther from the midline.

• Medial: Nearer to the midline.

Chapter 2: The Chemical Level

Chemical Elements and Atoms

All matter is composed of chemical elements, substances that cannot be broken down into simpler substances by ordinary chemical means. The smallest units of elements are atoms.

• Atoms: Consist of a nucleus (containing protons and neutrons) and electrons that surround the nucleus in a cloud.

• Protons: Positively charged particles in the nucleus.

• Neutrons: Uncharged particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

• In a neutral atom, the number of protons equals the number of electrons.

Atomic Number and Mass Number

• Atomic number (Z): The number of protons in the nucleus of an atom.

• Mass number (A): The sum of protons and neutrons in the nucleus.

Example: For carbon, Z = 6 (6 protons), A = 12 (6 protons + 6 neutrons).

• Molecules: Two or more atoms joined together by chemical bonds.

Additional info: The chemical level forms the foundation for all higher levels of biological organization, as atoms and molecules make up the structures and substances necessary for life.