Anatomy and Physiology: The Tissue Level of Organization

Chapter 5: The Tissue Level of Organization

Introduction

  • The study of tissues is vital for understanding the structural and functional organization of the body.


Section 5.1: Types and Components of Tissues


Definition of Key Terms

  • Tissue: A group of cells that perform a specific function.

  • Histology: The study of tissue structure, organization, and function.

  • Pathology: The study of changes associated with disease of tissues.

Four Main Types of Tissue

  1. Epithelial tissue: Forms coverings, linings, and glands.

  2. Connective tissue: Provides protection and support.

  3. Muscle tissue: Allows for movement.

  4. Nervous tissue: Facilitates communication throughout the body.

Section 5.2: Epithelial Tissue


Characteristics of Epithelia

  • Epithelial tissues form coverings, linings, and glands.

  • Basement membrane: Anchors epithelia to the extracellular matrix (ECM).

  • Two distinct surfaces:

    • Basal surface: The surface attached to the basement membrane.

    • Apical surface: The surface exposed to either the external environment or an internal body space.

  • Avascular: Lacks blood vessels and relies on diffusion from capillaries in the underlying connective tissue.

  • Highly regenerative: Capable of rapid cell division.

Classification of Epithelial Tissues

  • Classified by shape and layers:

    • Shape:

    1. Squamous: Flat cells.

    2. Cuboidal: Box-shaped cells.

    3. Columnar: Column-like cells.

    • Layers:

    1. Simple: Single layer of cells.

    2. Stratified: Two or more layers of cells.

    3. Pseudostratified: Appears layered but is a single layer.

Simple Epithelia (Table 5.1)

  1. Simple squamous epithelium

  2. Simple cuboidal epithelium

  3. Simple columnar epithelium

  4. Pseudostratified ciliated columnar epithelium

Stratified Epithelia (Table 5.1)

  1. Stratified squamous epithelium

  2. Stratified cuboidal epithelium

  3. Stratified columnar epithelium

  4. Transitional epithelium

  1. Classify types of connective tissues.

  2. Understand the function of connective tissue cells and fibers.

Classification of Connective Tissues

  • Twelve types of connective tissues are separated into three categories:

    1. Connective tissue proper:

    • Areolar, adipose, reticular, dense regular, dense irregular connective tissue.

    1. Supportive connective tissue:

    • Hyaline cartilage, fibrocartilage, elastic cartilage, compact bone, spongy bone.

    1. Fluid connective tissue:

    • Blood and lymph.

Cells and Fibers of Connective Tissues

  • Fibroblasts: Produce fibers in the ECM.

    • Collagen: Strongest fibers providing tensile strength.

    • Elastic fibers: Provide elasticity.

    • Reticular fibers: Branching fibers that support internal organs.

    • Adipocytes: Store energy and provide cushioning.

    • White blood cells: Essential for immune function.

    • Red blood cells: Carry gases such as oxygen.

Loose Connective Tissues

  1. Areolar connective tissue: Located in subcutaneous layers and supports nearby tissues.

  2. Adipose tissue: Focused on energy storage and cushioning.

  3. Reticular connective tissue: Forms a framework for internal organs.

Dense Connective Tissues

  1. Dense regular connective tissue: Forms tendons and ligaments.

  2. Dense irregular connective tissue: Found in the skin.

Cartilage Types

  1. Hyaline cartilage: Most abundant, located within joints and ribs.

  2. Fibrocartilage: Strongest, found in intervertebral discs.

  3. Elastic cartilage: Present in the external ear.

Bone Classification

  • Compact bone: Solid, offers greater strength.

  • Spongy bone: Contains spaces that house red bone marrow.

Fluid Connective Tissues

  • Comprises blood and lymph:

    • Blood: Contains cells such as erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.

    • Lymph: An acellular component helping maintain bodily fluid levels.

  1. Identify the characteristics of muscle tissue.

  2. Recognize different muscle tissue types.

Characteristics of Muscle Tissue

  • Major function: Movement.

  • Contracts in response to stimuli:

    • Voluntary muscle: Requires conscious control.

    • Involuntary muscle: Functions without conscious control.

Types of Muscle Tissue

  1. Skeletal Muscle:

    • Attached to bones.

    • Allows body movement and maintains posture.

    • Contains striations (alternating light and dark bands).

    • Voluntary control and multinucleated.

  2. Cardiac Muscle:

    • Found in the walls of the heart.

    • Contains striations.

    • Involuntarily controlled.

    • Cells are interconnected by intercalated discs in cardiac structure.

  3. Smooth Muscle:

    • Found in internal organs and associated with various systems (digestive, respiratory, urinary, reproductive).

    • Lacks striations and is involuntarily controlled.

Section 5.5: Nervous Tissue

Neurons

  • Function: Generate action potentials.

  • Anatomical structures:

    • Dendrites: Short branches that receive signals.

    • Cell body: Houses nucleus and organelles.

    • Axon: Long projection to send action potentials.

    • Synapse: Gap between neuron and its target, facilitating communication.

Glial Cells

  • Various types support neuronal function.

  • Some glial cells form myelin, insulating axons to allow faster action potential transmission.

Section 5.6: Membranes

Types of Membranes

  1. Mucous Membranes:

    • Line body cavities exposed to the external environment.

    • Contain goblet cells that secrete mucus.

    • Found in the digestive, respiratory, urinary, and reproductive tracts.

  2. Serous Membranes:

    • Cover and line internal organs to reduce friction.

    • Examples: Pericardium (heart), Pleura (lungs), Peritoneum (abdominal cavity).

  3. Cutaneous Membrane:

    • The skin, acting as a barrier against dehydration and pathogens.

    • Made of stratified squamous epithelium with keratin providing protection.

  4. Synovial Membrane:

    • Located in freely movable joints (e.g., elbow, hip, knee).

    • Secretes synovial fluid for lubrication and nourishment of cartilage, thereby reducing friction.

Section 5.7: Tissue Growth and Healing

Inflammation

  • The body’s initial standard response to injury.

  • Aims to limit the extent of injury and initiate repair:

    • Acute inflammation: Short-term response.

    • Chronic inflammation: Persists over long periods, potentially leading to further tissue damage.

Tissue and Aging

  • Tissues undergo changes as the body ages:

    • Rate of mitosis slows down, resulting in slower tissue healing.

    • Decrease in the number of elastic fibers, leading to decreased elasticity and contributing to wrinkles, joint stiffness, and hypertension.

Tissues and Cancer

  • Cancerous cells may harbor mutations that disrupt regulatory signals, resulting in uncontrolled growth:

    • A mass of cells resulting from uncontrolled growth is referred to as a tumor.

    • Malignant tumors: Harmful, causing damage to the body.

    • Benign tumors: Non-harmful and typically do not cause disease.