Introduction to Anatomy & Physiology: Organization, Tissues, and Organ Systems

Introduction to Anatomy & Physiology

Basic Characteristics of Living Things

Living organisms share several fundamental characteristics that distinguish them from non-living matter. These characteristics are essential for maintaining life and include:

• Cells: Basic structural and functional units of life.

• Organization: Ordered structure in biological systems.

• Responsiveness: Ability to sense and respond to stimuli.

• Regulation: Maintenance of internal conditions (homeostasis).

• Growth & Development: Increase in size and complexity.

• Reproduction: Production of new organisms.

• Metabolism: All chemical processes occurring in the body.

Homeostasis

Homeostasis is the process by which living organisms maintain a relatively stable internal environment despite changes in external conditions. This is vital for the survival and proper functioning of cells and organs.

• Involves feedback mechanisms to regulate variables such as temperature, pH, and ion concentrations.

• Disruption of homeostasis can lead to disease or dysfunction.

Metabolism

Metabolism encompasses all chemical reactions that occur within living organisms to maintain life. It includes two main types of processes:

• Anabolic (building up) processes: Synthesis of large molecules from smaller ones (e.g., protein synthesis).

• Catabolic (breaking down) processes: Breakdown of large molecules to release energy (e.g., cellular respiration).

Metabolic processes require energy, which must be continually replaced as it is used.

Basic Metabolic Processes

• Respiration

• Digestion

• Circulation

• Excretion

Anatomy and Physiology: Definitions and Scope

Anatomy

Anatomy is the study of the structure of the body and the physical relationships among body parts.

• Gross Anatomy: Study of large structures visible to the naked eye.

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

Gross Anatomy	Microscopic Anatomy
Large structures & features Visible to the eyes	Structures not seen without magnification Dissecting microscope: tissue structures Light microscope: cell structures Electron microscope: molecules

Physiology

Physiology is the study of function and how living organisms perform their vital functions. Structure and function are interrelated; anatomical details are significant because each has an effect on function, and physiological mechanisms can only be fully understood in terms of the underlying structural relationships.

Levels of Organization in the Human Body

The human body is organized into hierarchical levels, each increasing in complexity:

Organization Level (big to small)	Definitions
Organism Level	All organ systems work together to maintain life and health (e.g., human)
Organ System Level	Organs interact in organ systems and work together for an outcome (e.g., cardiovascular system)
Organ Level	Consists of 2 or more tissues working to perform several functions (e.g., heart muscle tissue + connective tissue)
Tissue Level	Groups of similar cells performing specific functions (e.g., cardiac muscle cells form cardiac muscle)
Cellular Level	Smallest living units; functions depend on organelles and complex molecules (e.g., single heart muscle cell)
Atomic/Chemical Level	Atoms combine to form molecules with complex shapes (e.g., small molecules joining to form proteins)

Cells and Cell Theory

• Cells are the smallest subunit of life.

• Dimensions are generally given in micrometers (μm).

Basic Principles of the Cell Theory

• Cells are structural building blocks of all plants and animals.

• Cells are produced by the division of pre-existing cells.

• Cells are the smallest structural units that perform all vital functions.

Cytology: The study of cells.

Tissues and Histology

Histology is the study of tissues. Specialized groups of cells and cell products form tissues, with roughly 200 different cell types in the body.

4 Primary Tissue Types

1. Epithelial tissue

2. Connective tissue

3. Muscle tissue

4. Nervous tissue

1. Epithelial Tissue

• Most common tissue type

• Layer of cells that form a barrier

• Protects exposed surfaces

• Produces glandular secretions

2. Connective Tissue

• Contains cells and an extracellular matrix (protein fibers & ground substance liquid)

• Amount & consistency of matrix depends on type of connective tissue

• Fills internal spaces

• Provides structural support

• Stores energy

3. Muscle Tissue

• Individual muscle cells contract

• Enables skeletal movement

• Provides soft tissue support

• Maintains blood flow

• Moves materials along internal pathways

• Stabilizes body temperature

4. Nervous Tissue

• Neurons: Transmit information in the form of electrical impulses

• Neuroglia: Isolate and protect neurons while forming supporting framework

Nervous tissue is divided into:

• Central Nervous System (CNS): Brain & spinal cord

• Peripheral Nervous System: Nerves connecting the CNS with other tissues & organs

Organs and Organ Systems

• Organ: Functional unit composed of more than one tissue type

• Organ System: Organs that interact to perform a specific range of functions

11 Organ Systems in the Body

Organ System	Major Function
Integumentary System	Protects against environmental hazards & helps control body temperature
Skeletal System	Provides support, protects tissues, stores minerals, forms blood cells
Muscular System	Produces movement, provides support, generates heat
Nervous System	Directs immediate responses to stimuli, coordinates activities of other organ systems
Endocrine System	Directs long-term changes in other organ systems
Cardiovascular System	Transports cells & dissolved materials in the bloodstream (nutrients, wastes, gases)
Lymphatic System	Defends against infection & disease, returns tissue fluid to the bloodstream
Respiratory System	Delivers air to sites where gas exchange occurs between air & blood, produces sound
Digestive System	Processes food, absorbs nutrients, eliminates waste
Urinary System	Eliminates excess water, salts, & waste, controls pH
Reproductive System	Produces sex cells & hormones, supports embryonic development (female)

Examples of Organ Systems

1. Integumentary System

• Protects against environmental hazards

• Helps control body temperature

• Major organs/structures: Hair, nails, sweat glands, sensory receptors

2. Skeletal System

• Provides support

• Protects tissues

• Major organs/structures: Bones, cartilage, joints, bone marrow

3. Muscular System

• Produces movement

• Provides support

• Generates heat

Additional info:

• Feedback mechanisms in homeostasis include negative feedback (returns conditions to normal) and positive feedback (amplifies changes, often in dangerous or stressful situations).

• Directional terms (anterior, posterior, superior, inferior, medial, lateral, superficial, deep) and sectional planes (frontal/coronal, sagittal, transverse) are used to describe locations and orientations in the body.

• Body cavities (thoracic, abdominopelvic) house and protect internal organs, separated by structures such as the diaphragm.