Major Organs and Organ Systems

Introduction to Major Organs

The study of human anatomy and physiology begins with identifying the major organs of the body and understanding their locations within various organ systems. This foundational knowledge is essential for further study in both anatomy and physiology.

• Nervous System: Brain

• Cardiovascular System: Heart

• Lymphatic System: Spleen

• Respiratory System: Lungs

• Digestive System: Liver, Gallbladder, Stomach, Pancreas, Small Intestine, Large Intestine

• Urinary System: Kidneys, Urinary Bladder

• Endocrine System: Adrenal Glands, Thyroid Gland

Histology Part 1: Introduction to Tissues

Overview of Histology

Histology is the study of the microscopic structure of tissues. All tissues in the human body are classified into four general types: epithelial tissue, muscle tissue, connective tissue, and nervous tissue. In this lab, the focus is on epithelial and muscle tissues.

• Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands.

• Muscle Tissue: Responsible for movement and force generation.

Epithelial Tissue

General Characteristics of Epithelial Tissue

Epithelial tissues cover surfaces exposed to the environment and line hollow organs and body cavities. The cells are tightly packed with minimal extracellular space and are attached to underlying tissues via a basement membrane, which consists of the basal lamina and reticular lamina. The basal surface faces the basement membrane, while the apical surface faces the environment or lumen.

Classification of Epithelial Tissue

Epithelial tissues are classified based on two criteria: cell shape and number of cell layers.

• Cell Shapes:

  • Squamous: Thin, flat cells

  • Cuboidal: Cube-shaped cells with centrally located nuclei

  • Columnar: Tall, column-like cells with nuclei typically near the base

• Number of Layers:

  • Simple Epithelium: Single layer of cells, all touching the basement membrane

  • Stratified Epithelium: Multiple layers; named for the shape of the apical layer

  • Pseudostratified Epithelium: Appears multilayered but all cells contact the basement membrane

Classification Tree of Epithelial Tissue

The following diagram summarizes the classification of epithelial tissues by cell shape and layering, including which types are required for Lab 1.

Simple Squamous Epithelium

Composed of a single layer of thin, flat cells, simple squamous epithelium allows for rapid diffusion, osmosis, filtration, and secretion. Special names include endothelium (lining heart chambers and blood vessels) and mesothelium (lining body cavities).

• Body Locations: Alveoli, glomerular capsule, lining of body cavities, heart chambers, blood vessels

Simple Cuboidal Epithelium

Simple cuboidal epithelium consists of a single layer of cube-shaped cells, primarily involved in secretion and absorption, with limited protection.

• Body Locations: Lining kidney tubules, thyroid gland

Simple Columnar Epithelium

Simple columnar epithelium is a single layer of tall, column-like cells. These cells may have cilia (for movement of substances) or microvilli (to increase surface area for absorption). This tissue is specialized for secretion and absorption.

• Body Locations: Lining the stomach, gallbladder, small intestine, large intestine

Pseudostratified Columnar Epithelium

Pseudostratified columnar epithelium appears to have multiple layers due to varying cell heights, but all cells contact the basement membrane. Goblet cells (mucus-producing) and cilia are common features.

• Body Locations: Lining the trachea, nasal cavities

Stratified Squamous Epithelium

Stratified squamous epithelium consists of multiple layers of cells, with squamous cells at the apical surface. It provides protection against mechanical stress.

• Body Locations: Epidermis, lining of esophagus, anus, rectum, vagina

Transitional Epithelium

Transitional epithelium is composed of multiple layers with dome-shaped cells at the apical surface. It is specialized to stretch and recoil without damage.

• Body Locations: Lining the ureters, urinary bladder

Muscle Tissue

Overview of Muscle Tissue

Muscle tissue is specialized for contraction and movement. There are three types of muscle tissue in the human body:

• Skeletal Muscle: Voluntary, striated, multinucleate, cylindrical cells; found in skeletal muscles

• Cardiac Muscle: Involuntary, striated, single nucleus, branched cells, intercalated discs; found in the heart

• Smooth Muscle: Involuntary, non-striated, single nucleus, tapered cells; found in walls of blood vessels and hollow organs

Lab 1 Study Checklist

• Define all bold terms from the lab manual

• Identify the major organs listed

• Classify each tissue as muscle or epithelium

• Identify the 3 muscle tissues and 6 epithelial tissues by their complete names

• Identify and label bolded structures for each tissue

• Give one detailed body location for each tissue, as listed in the manual

• Use only lab manual definitions and terms