Foundations of Anatomy & Physiology: Levels of Organization, Cell Structure, and Functional Cell Types

Topics of Anatomy

Overview of Anatomical Study

Anatomy is the study of the structure of body parts and their relationships to one another. It is divided into several subfields based on the scale and method of observation.

• Gross (macroscopic) anatomy: Study of large body structures visible to the naked eye.

  • Examples: Heart, lungs, kidneys

• Regional anatomy: Focuses on all structures in a particular area of the body.

  • Examples: Muscles, bones, blood vessels in a specific region

• System anatomy: Looks at one organ system at a time.

  • Examples: Cardiovascular, nervous, muscular systems

• Surface anatomy: Studies internal structures as they relate to the overlying skin.

  • Example: Using surface anatomy to identify bulging muscles beneath the skin

• Microscopic anatomy: Deals with structures too small to be seen with the naked eye.

  • Examples: Cytology (study of cells), Histology (study of tissues)

Specialized Fields

• Cytology: Study of cells

• Histology: Study of tissues

• Developmental anatomy: Traces structural changes throughout the life span

• Embryology: Study of developmental changes before birth

Essential Skills in Anatomy

• Observation

• Manipulation

• Palpation (feeling organs with hands)

• Auscultation (listening to organs with a stethoscope)

Medical Imaging Technology

• Non-invasive tools to view inside the body: X-ray, MRI, CT, ultrasound

Subdivisions of Physiology

Overview of Physiological Study

Physiology is the study of the function of body parts and how they work to carry out life-sustaining activities. It is often organized by organ systems.

• Renal physiology: Functions of the kidney and urine production

• Neurophysiology: Functions of the nervous system

• Cardiovascular physiology: Functions of the heart and blood vessels

Physiology often focuses on cellular or molecular events, such as chemical reactions in individual cells.

Principle of Complementarity of Structure and Function

The function of a body structure depends on its specific form. For example, the urinary bladder can store urine because it stretches and expands as urine accumulates.

• Incisors (structure): Ideal for cutting like scissors (function)

• Molars (structure): Ideal for grinding like a mortar and pestle (function)

Levels of Structural Organization in the Human Body

Hierarchy from Simple to Complex

The human body is organized into levels of increasing complexity, each building upon the previous.

1. Chemical level: Atoms and molecules

2. Cellular level: Cells and their organelles

3. Tissue level: Groups of similar cells

4. Organ level: Contains two or more types of tissues

5. Organ system level: Organs that work closely together

6. Organismal level: All organ systems combined to make the whole organism

Example:

1. Chemical level – atoms

2. Cellular level – smooth muscle cell

3. Tissue level – smooth muscle tissue

4. Organ level – blood vessel

5. Organ system level – cardiovascular system

Major Tissue Types

Classification and Functions

• Epithelial Tissue: Covers body surface and lines cavities

• Muscle Tissue: Provides movement

• Connective Tissue: Supports and protects body organs

• Nervous Tissue: Provides rapid internal communication by transmitting electrical impulses

Cells and Cell Theory

Definition and Diversity

Cells are the structural and functional units of all living things. The human body contains 50 to 100 trillion cells, with over 250 different types that vary in size, shape, and subcellular components, leading to differences in function.

Cell Theory

• The cell is the smallest unit of life

• All organisms are made of one or more cells

• Cells arise only from other cells

  • Most body cells arise by mitosis

  • Ova and sperm arise by meiosis

Functional Categories of Body Cells

Major Cell Types and Their Functions

Functional Category	Example Cell Types	Function
Cells that connect body parts, form linings, or transport gases	Fibroblasts, Erythrocytes, Epithelial cells	Connect tissues, transport oxygen, form protective linings
Cells that move organs and body parts	Skeletal muscle cells, Smooth muscle cells	Produce movement
Cells that store nutrients	Fat cell	Store energy as fat
Cells that fight disease	Macrophage	Engulf and destroy pathogens
Cells that gather information and control body function	Nerve cell	Transmit electrical impulses
Cells of reproduction	Sperm	Fertilize egg for reproduction

Structure of the Generalized Cell

Overview and Major Organelles

The generalized cell is depicted as roughly oval in shape, with the plasma membrane enclosing the entire cell. The cytoplasm is the material between the plasma membrane and the nucleus, containing the cytoskeleton and various organelles.

• Mitochondrion: Double membrane-bound organelle, kidney bean-shaped; produces most of the cell's ATP (energy).

• Ribosomes: Small granules; sites of protein synthesis.

• Rough endoplasmic reticulum (ER): Network of interconnected tubes and parallel membranes; studded with ribosomes; synthesizes proteins.

• Smooth endoplasmic reticulum (ER): Tubular network; synthesizes lipids and detoxifies chemicals.

• Golgi apparatus: Stacked flattened membranous sacs; modifies, concentrates, and packages proteins and lipids.

• Peroxisomes: Spherical membranous sacs; contain enzymes for detoxification.

• Lysosomes: Spherical membranous organelles; contain digestive enzymes.

• Centrosome: Region near nucleus; acts as microtubule organizing center; contains centrioles.

• Nucleus: Large, spherical structure; control center of the cell.

• Nuclear envelope: Double membrane enclosing the nucleus.

• Chromatin: DNA, histone proteins, and RNA chains; genetic material inside the nucleus.

Additional info: The cytoskeleton includes microfilaments, intermediate filaments, and microtubules, which provide structural support and facilitate cell movement.