Name
Western Governors University
D312 Anatomy and Physiology I with Lab
Prof. Name
Date
Anatomy is the scientific study focused on understanding the physical structure of the human body, including the size, shape, and spatial relationships of various body parts. A key aspect of anatomy is exploring how structural features relate to function. Within this field, Developmental Anatomy investigates the changes in body structures from conception to adulthood. A more specialized area called Embryology focuses on the early stages of development, specifically from conception up to the eighth week of gestation.
Anatomy also operates on different scales: Cytology examines cellular structures under the microscope, while Histology studies tissues composed of groups of cells and extracellular substances. Gross Anatomy deals with body structures visible to the naked eye and can be approached either by studying entire body systems (Systemic Anatomy) or by examining specific body regions (Regional Anatomy). Additionally, Surface Anatomy involves assessing external body features to infer the locations of deeper structures, such as feeling the ribs and sternum on the chest.
Modern technology has expanded anatomy’s reach through Anatomical Imaging methods, including X-rays, ultrasound, and MRI scans, which allow for non-invasive internal body examinations.
Are all human bodies structurally identical?
No, individual anatomical differences exist and are known as Anatomical Anomalies—physical variations that differ from the typical anatomical pattern.
Physiology is the branch of science that studies the functions and processes of living organisms. Its primary focus is to understand how the body responds to internal and external stimuli and maintains internal stability—known as homeostasis—despite changes in the environment. Unlike anatomy, which often focuses on structure, physiology typically examines entire organ systems to comprehend how they function collectively.
Some main branches of physiology include:
| Branch | Focus |
|---|---|
| Cell Physiology | Functions and processes within cells |
| Systemic Physiology | Functions of entire organ systems |
| Neurophysiology | Nervous system activities |
| Cardiovascular Physiology | Heart and blood vessel function |
Anatomy and physiology are deeply intertwined since understanding the body’s physical structure is essential for grasping how it functions.
In medical science, Pathology is closely related and studies diseases by investigating their causes, progression, and the structural and functional changes they cause.
The human body is organized in a hierarchy of six increasingly complex levels, from the smallest building blocks to the complete organism:
| Level | Description | Example |
|---|---|---|
| Chemical Level | Atoms and molecules, the smallest units of matter | Collagen molecules in skin providing strength |
| Cell Level | Basic units of life formed by molecules | Cell nucleus containing genetic material |
| Tissue Level | Groups of similar cells plus extracellular matrix | Four types: epithelial, connective, muscle, nervous |
| Organ Level | Structures composed of two or more tissue types | Heart, lungs, stomach |
| Organ System Level | Organs working together to perform specific functions | Urinary system including kidneys and bladder |
| Organism Level | Entire living being made up of organ systems | A complete human being |
The human body comprises 11 primary organ systems, each specialized to perform unique roles vital for survival and health:
| Organ System | Primary Functions | Main Components |
|---|---|---|
| Integumentary | Protects the body, regulates temperature, prevents water loss, synthesizes vitamin D | Skin, hair, nails, sweat glands |
| Skeletal | Supports and protects organs, enables movement, produces blood cells, stores minerals | Bones, cartilage, ligaments, joints |
| Muscular | Facilitates movement, maintains posture, generates heat | Skeletal muscles attached via tendons |
| Nervous | Detects sensory stimuli, controls movements and bodily functions, cognitive functions | Brain, spinal cord, nerves, sensory receptors |
| Endocrine | Regulates metabolism, growth, and reproduction via hormones | Glands such as pituitary and thyroid |
| Cardiovascular | Transports nutrients, gases, wastes, hormones; regulates temperature; immune response | Heart, blood vessels, blood |
| Lymphatic | Defends against disease, removes foreign substances, maintains fluid balance, absorbs fats | Lymphatic vessels, nodes, organs |
| Respiratory | Exchanges oxygen and carbon dioxide, regulates blood pH | Lungs, respiratory tract |
| Digestive | Breaks down food, absorbs nutrients, eliminates waste | Mouth, esophagus, stomach, intestines, accessory organs |
| Urinary | Eliminates waste, regulates pH, ion and water balance | Kidneys, urinary bladder, ducts |
| Reproductive | Produces sex cells and hormones, supports fertilization and development | Female: ovaries, uterus, mammary glands; Male: testes, ducts, penis |
Living organisms share six fundamental traits that define life:
Organization: Life forms exhibit highly organized structures from molecules and cells to complex organ systems.
Metabolism: Encompasses all chemical reactions in cells, including energy production and molecule synthesis.
Responsiveness: The capacity to detect and respond to internal and external environmental changes.
Growth: An increase in cell size or number that results in the enlargement of the organism or its parts.
Development: Lifespan changes including cell specialization (differentiation) and changes in shape (morphogenesis).
Reproduction: The ability to produce new cells or organisms, critical for growth and survival of species.
Homeostasis refers to the body’s ability to sustain a stable internal environment despite external changes. For instance, human body temperature normally hovers around 98.6°F (37°C), fluctuating slightly but maintained within a narrow range to support optimal function.
Homeostasis primarily relies on negative feedback mechanisms to counteract deviations from set points:
Receptor: Detects changes in variables (e.g., temperature sensors).
Control Center: Processes information and sets the desired range (often the brain).
Effector: Implements responses to adjust variables (e.g., sweat glands cool the body).
In contrast, positive feedback amplifies changes, typically to complete processes such as childbirth contractions. While beneficial in some cases, positive feedback can be harmful when unregulated, such as during a heart attack.
The anatomical position is a standard reference posture where a person stands upright, facing forward, arms at the sides, and palms facing forward. This position ensures consistent and clear descriptions of body parts and directions.
Two important body positions:
Supine: Lying face up.
Prone: Lying face down.
Directional terms are used to describe locations relative to other body parts:
| Term | Meaning | Example |
|---|---|---|
| Superior | Toward the head or upper part | Chin is superior to the navel |
| Inferior | Away from the head or lower part | Navel is inferior to the chin |
| Anterior | Front of the body | Navel is anterior to the spine |
| Posterior | Back of the body | Spine is posterior to the breastbone |
| Proximal | Closer to point of attachment | Elbow is proximal to the wrist |
| Distal | Farther from point of attachment | Wrist is distal to the elbow |
| Medial | Toward the midline | Nose is medial to the eyes |
| Lateral | Away from the midline | Nipple is lateral to the breastbone |
| Superficial | Toward the body surface | Skin is superficial to muscle |
| Deep | Away from the body surface | Lungs are deep to the ribs |
The body can be divided into different planes to help study anatomy systematically:
| Plane | Description |
|---|---|
| Sagittal | Vertical plane dividing body into right and left parts |
| Median (Midsagittal) | Sagittal plane dividing body into equal halves |
| Transverse (Horizontal) | Divides body into upper (superior) and lower (inferior) parts |
| Frontal (Coronal) | Vertical plane dividing body into front (anterior) and back (posterior) parts |
Sections created by these planes are named accordingly: longitudinal, transverse, and oblique.
Anatomy and physiology form the foundation for understanding human biology, ranging from microscopic cellular structures to complex organ systems. Together, they explain how the body is built and how it functions to maintain life. Homeostasis is vital for internal stability, while standardized anatomical terms and positions ensure clear communication in medical and scientific settings.
Marieb, E. N., & Hoehn, K. (2019). Human Anatomy & Physiology (11th ed.). Pearson.
Saladin, K. S. (2021). Anatomy & Physiology: The Unity of Form and Function (9th ed.). McGraw-Hill Education.
Tortora, G. J., & Derrickson, B. H. (2017). Principles of Anatomy and Physiology (15th ed.). Wiley.
