Introduction to Anatomy and Physiology

1-1 Basic Functions of Living Organisms

All living organisms share certain fundamental characteristics that distinguish them from non-living matter. Understanding these functions is essential for the study of anatomy and physiology.

• Organization: Living things exhibit a complex but ordered structure, from the cellular to the organismal level.

• Metabolism: The sum of all chemical reactions in the body, including catabolism (breaking down molecules) and anabolism (building up molecules).

• Responsiveness: The ability to sense and respond to changes in the environment (stimuli).

• Growth and Development: Increase in size and complexity over time.

• Reproduction: The ability to produce new organisms and pass on genetic material.

• Movement: Both internal (transport of substances) and external (locomotion).

• Homeostasis: Maintenance of a stable internal environment.

1-2 Relationship Between Anatomy and Physiology; Specialties

Anatomy is the study of the structure of body parts, while physiology is the study of how those parts function. These disciplines are closely related, as structure often determines function.

• Gross Anatomy: Study of structures visible to the naked eye (e.g., organs, organ systems).

• Microscopic Anatomy: Study of structures requiring magnification (e.g., cells, tissues).

• Specialties in Anatomy: Regional, systemic, surface, developmental, and clinical anatomy.

• Specialties in Physiology: Cell physiology, organ physiology, systemic physiology, pathological physiology.

Example: The structure of the heart (anatomy) enables it to pump blood (physiology).

1-3 Major Levels of Organization in Organisms

Biological organization in humans progresses from the simplest to the most complex levels:

• Chemical Level: Atoms and molecules essential for life.

• Cellular Level: Cells, the basic units of life.

• Tissue Level: Groups of similar cells performing a common function.

• Organ Level: Structures composed of two or more tissue types working together.

• Organ System Level: Groups of organs that perform related functions.

• Organism Level: The complete living being.

1-4 The 11 Organ Systems of the Human Body and Their Major Functions

The human body is organized into 11 organ systems, each with distinct functions. The table below summarizes these systems and their primary roles.

Contrast: For example, the nervous system provides rapid, short-term responses, while the endocrine system regulates long-term processes.

1-5 The Concept of Homeostasis

Homeostasis is the maintenance of a stable internal environment despite external changes. It is vital for the survival and proper functioning of organisms.

• Involves dynamic equilibrium, where conditions fluctuate within a narrow range.

• Regulated by feedback mechanisms.

• Examples: Body temperature, blood glucose levels, pH balance.

1-6 Negative and Positive Feedback in Homeostatic Regulation

Feedback mechanisms are processes that help maintain homeostasis by responding to changes in the internal environment.

• Negative Feedback: The most common mechanism; a change in a variable triggers a response that counteracts the initial change, restoring balance.

• Example: Regulation of body temperature. If body temperature rises, mechanisms such as sweating are activated to cool the body.

• Positive Feedback: Less common; a change in a variable triggers a response that amplifies the initial change.

• Example: Blood clotting and labor contractions during childbirth.

General Feedback Loop Equation:

1-7 Anatomical Terms for Body Regions, Sections, and Relative Positions

Standard anatomical terms are used to describe locations and relationships of body parts.

• Body Regions: Examples include cephalic (head), thoracic (chest), abdominal, pelvic, brachial (arm), femoral (thigh).

• Body Sections/Planes:

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

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

  • Sagittal: Divides body into right and left parts (midsagittal = equal halves).

• Relative Positions: Superior/inferior, anterior/posterior, medial/lateral, proximal/distal, superficial/deep.

Example: The heart is medial to the lungs and superior to the diaphragm.

1-8 Major Body Cavities of the Trunk and Their Subdivisions

The trunk of the body contains major cavities that house and protect internal organs.

• Dorsal Body Cavity: Includes the cranial cavity (brain) and vertebral cavity (spinal cord).

• Ventral Body Cavity: Divided into:

  • Thoracic Cavity: Contains pleural cavities (lungs) and pericardial cavity (heart).

  • Abdominopelvic Cavity: Contains abdominal cavity (digestive organs) and pelvic cavity (urinary bladder, reproductive organs).

Subdivisions: The diaphragm separates the thoracic and abdominopelvic cavities. Membranes such as the pleura, pericardium, and peritoneum line these cavities and cover organs.