Anatomy & Physiology: Foundational Concepts

Definitions and Scope

Anatomy and Physiology are two closely related fields that form the basis of understanding the human body. Anatomy focuses on the structure of body parts, while Physiology examines their function and how they contribute to life-sustaining activities.

• Anatomy: The study of the structure of body parts and their relationships to one another.

• Physiology: The study of the function of body parts; how they work to carry out life-sustaining activities.

• Example: An anatomist studies the shape, size, location, blood supply, and innervation of the liver, while a physiologist investigates the production of bile and the liver's role in nutrition and regulation of body functions.

Subdivisions of Anatomy

Major Branches

Anatomy is divided into several branches based on the size and visibility of structures studied.

• Macroscopic (Gross) Anatomy: Study of large, visible structures.

• Regional Anatomy: All structures in a particular area of the body.

• Systemic Anatomy: Study of one system (e.g., cardiovascular, nervous).

• Surface Anatomy: Study of internal structures as they relate to the overlying skin.

• Microscopic Anatomy: Structures too small to be seen by the naked eye.

  • Cytology: Study of cells.

  • Histology: Study of tissues.

• Developmental Anatomy: Study of anatomical and physiological development throughout life.

• Embryology: Study of developments before birth.

Note: Studying anatomy requires knowledge of anatomical terminology and the ability to observe, manipulate, palpate, and auscultate.

Subdivisions of Physiology

Organ System Focus

Physiology is often studied by organ systems and focuses on cellular and molecular levels.

• Examples: Renal physiology (kidneys), cardiovascular physiology (heart and blood vessels).

• Physiology examines how body abilities depend on chemical reactions in individual cells.

• Understanding physiology requires basic physical and chemical principles, such as electrical currents, pressure, and movement.

Complementarity of Structure & Function

Principle of Complementarity

Anatomy and physiology are inseparable; function always reflects structure, and what a structure can do depends on its specific form.

• Example 1: Bones can support body organs because they contain hard mineral deposits.

• Example 2: Blood flows in one direction through the heart because the heart has valves that prevent backflow.

• Example 3: Lungs can serve as a site for gas exchange because the walls of their air sacs are extremely thin.

Levels of Structural Organization in the Human Body

Hierarchical Organization

The human body is organized from the smallest chemical level to the whole organism level.

• Chemical Level: Atoms combine to form molecules.

• Cellular Level: Cells are the fundamental structural and functional units of life.

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

• Organ Level: Structures composed of at least two (usually four) tissue types that perform specific functions.

• Organ System Level: Organs that work closely together to accomplish a common purpose.

• Organismal Level: All organ systems combined to make the whole organism.

Cells: The Living Unit

Cell Diversity and Structure

There are over 250 different types of human cells, varying in size, shape, subcellular components, and functions. All cells share three basic parts:

• Plasma Membrane: Flexible outer boundary.

• Cytoplasm: Intracellular fluid containing organelles.

• Nucleus: DNA-containing control center.

General Structure of the Cell

Cytoplasm and Organelles

The cytoplasm is the cellular material located between the plasma membrane and the nucleus. It is composed of:

• Cytosol: Gel-like solution made up of water and soluble molecules.

• Inclusions: Insoluble molecules; vary with cell type (e.g., glycogen granules, pigments).

• Organelles: Metabolic machinery structures of the cell, each with specialized function.

Organelles are classified as membranous or non-membranous:

• Membranous: Mitochondria, Endoplasmic Reticulum (ER), Golgi Apparatus, Peroxisomes, Lysosomes.

• Non-Membranous: Ribosomes, Cytoskeleton, Centrioles.

Major Organelles and Their Functions

Mitochondria

Known as the "power plant" of cells, mitochondria generate most of the cell's ATP via aerobic respiration.

• Enclosed by double membranes; inner membrane has folds called cristae.

• Contain their own DNA, RNA, and ribosomes.

Endoplasmic Reticulum (ER)

• Rough ER: Studded with ribosomes; synthesizes proteins.

• Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification.

Golgi Apparatus

Stacked and flattened membranous sacs that modify, concentrate, and package proteins and lipids received from the ER.

• Directs proteins and lipids to their final destinations via transport vesicles.

• Three main pathways for vesicles:

  • Secretory vesicles (exocytosis)

  • Vesicles containing membrane components

  • Lysosomes containing digestive enzymes

Peroxisomes

Membranous sacs containing enzymes that detoxify harmful substances and neutralize free radicals.

• Oxidase converts toxins to hydrogen peroxide ().

• Catalase converts to water.

• Also involved in fatty acid breakdown and synthesis.

Lysosomes

Membranous bags containing digestive enzymes (acid hydrolases).

• Break down ingested bacteria, viruses, and toxins.

• Degrade nonfunctional organelles.

• Release stored glycogen and calcium.

• Autolysis: cellular self-digestion in injured cells.

Cytoskeleton

Elaborate network of protein rods throughout the cytosol, providing structural support and facilitating movement.

• Microfilaments

• Intermediate filaments

• Microtubules

Centrosome & Centrioles

The centrosome is the "cell center" near the nucleus, consisting of a granular matrix and a pair of centrioles.

• Generates microtubules and organizes the mitotic spindle.

• Centrioles form the basis of cilia and flagella.

Cellular Extensions

Cilia, Flagella, and Microvilli

Some cells have structures extending from the cell surface:

• Cilia: Whiplike, motile extensions that move substances across the cell surface (e.g., respiratory tract).

• Flagella: Longer extensions that propel the whole cell (e.g., sperm tail).

• Microvilli: Fingerlike projections that increase surface area for absorption.

Both cilia and flagella are made up of microtubules arranged in a "9 + 2" pattern (nine pairs surrounding two central microtubules).

Extracellular Materials

Types and Functions

Substances found outside cells are collectively called extracellular materials.

• Extracellular fluids:

  • Interstitial fluid: bathes cells

  • Blood plasma: fluid of the blood

  • Cerebrospinal fluid: surrounds nervous system organs

• Cellular secretions: e.g., saliva, mucus

• Extracellular matrix: Acts as glue to hold cells together

Classification of Body Tissues

Four Basic Types

The human body contains four main types of tissues, each with distinct functions:

Summary Table: Levels of Structural Organization

Additional info: These notes expand on the provided slides with definitions, examples, and tables for clarity and completeness, suitable for college-level Anatomy & Physiology students.