Tissue Level of Organisation

Types of Tissue

• Introduction to Tissue Types   - Course: HUBS 1401 - Human Bioscience

Learning Outcomes

• Key Learning Outcomes for the Course:   - Name the four major tissue types in the human body and their chief subcategories.   - Explain how the four major tissue types differ structurally and functionally.   - Identify major locations of the various tissue types in the body.

Cell Differentiation

• Understanding Cell Types:   - Cells can divide and differentiate into various specialized types.   - Examples of cell types include:     - Loose connective tissue with fibroblasts     - Bone tissue with osteocytes     - Nerve cells     - Striated muscle cells     - Red blood cells     - Intestinal epithelial cells     - Smooth muscle cells     - Adipose (fat) cells

Gene Activation in Cell Differentiation

• Differentiation Mechanisms:   - Different genes are active in different cell types.   - Genes are initially kept inactive by bound proteins, which must be removed for gene activation.   - Each gene has regulatory segments such as:     - ‘read this message’ – signals that the gene can be transcribed.     - ‘don’t read this message’ – inhibits transcription.     - ‘message starts/ends here’ – indicates the range for active transcription.   - An active gene leads to the production of its corresponding protein.

Cell Differentiation Process

• Characteristics of Cell Differentiation:   - Involves a progression from less specialized to more specialized forms.   - It is a step-wise process that is not reversible.   - Types of Stem Cells:     - Adult stem cells:       - Partially differentiated and have limited pathways to differentiation.     - Embryonic stem cells:       - Pluripotent; capable of developing into any cell type.

Overview of Major Tissue Types

• Defining Tissue:   - Tissue refers to an organized aggregation of cells and their products that function collectively.

Epithelial Tissue

• Learning Outcomes for Epithelial Tissue:   - Describe the basic properties of epithelial tissue.   - Explain how epithelial tissue is constructed.   - Define the classification of epithelial tissue.

Characteristics of Epithelial Tissue

• 10 Key Characteristics:   - Cellular with specialized contacts.   - Exhibits polarity (apical and basal surfaces).   - Supported by connective tissue.   - Avascular but innervated (lack blood vessels but possess nerve endings).   - High regenerative capacity, requiring stem cells for repair in areas like the GI tract and skin.

Specialized Structures in Epithelial Cells

• Increased Surface Area:   - Certain epithelial cells have adaptations, such as microvilli or cilia, to enhance their functionality.

Classification of Epithelia

• Basis of Classification:   - Classification is based on:     - Cell Shape:       - Squamous (flat).       - Cuboidal (cube-shaped).       - Columnar (elongated).     - Number of Cell Layers:       - Simple (single layer).       - Stratified (multiple layers).

Functions of Epithelial Tissue

• Overview of Functions:   - Provides physical protection.   - Regulates permeability (controls what enters/exits).   - Provides sensory functions.   - Capable of specialized secretions (e.g., mucus, enzymes).   - Effective barrier when it forms a complete cover or lining.

Glandular Epithelia

• Gland Functions:   - Gland cells are specialized for secretion.   - Types of Glands:     - Exocrine glands:       - Release substances into ducts that lead to the epithelial surface (e.g., digestive enzymes, milk).     - Classification by Structure & Secretion Mode:       - Can be unicellular (e.g., goblet cells) or multicellular.

Types of Epithelium

• Simple Squamous Epithelium:   - Description: Single layer of flattened cells.   - Function: Allows diffusion and filtration; secretes lubricating substances.   - Location: Air sacs of lungs, lining of heart and blood vessels.

• Stratified Squamous Epithelium:   - Description: Multiple layers of cells, with keratinized (dead) cells at the surface or non-keratinized types found in moist areas.   - Function: Provides protection against mechanical stresses.

• Simple Cuboidal Epithelium:   - Description: Single layer of cube-shaped cells.   - Function: Involved in secretion and absorption.   - Location: Kidney tubules, glands.

• Simple Columnar Epithelium:   - Description: Single layer of taller cells; may have cilia and goblet cells for secretion.   - Function: Absorption and secretion.   - Location: Digestive tract lining, uterine tubes.

Connective Tissue

• Learning Outcomes for Connective Tissue:   - Explain connective tissue characteristics and roles.   - Describe key cells found in various connective tissues.   - Define different extracellular fibers and their roles.   - List different categories of connective tissue and their specifics.

Characteristics of Connective Tissue

• Found throughout the body, never exposed to outside environments.

• Functions include:   - Establishing structural frameworks.   - Transportation of fluids and dissolved materials.   - Protection of delicate organs.   - Supporting other tissues.   - Storage of energy reserves.   - Defense against microorganisms.

Components of Connective Tissue

• Basic Components:   - Specialized cells.   - Extracellular matrix (includes protein fibers and ground substance).

Key Cells in Connective Tissue

• Fibroblasts:   - Most abundant, secrete protein components and form ground substance.

• Adipocytes:   - Store lipids; numbers vary by tissue type.

• Immune Cells:   - Some are permanent residents, others are migratory.

Types of Connective Tissue Fibres

• Collagen Fibres:   - Long and unbranched, providing strength in tissues such as tendons and ligaments.

• Reticular Fibres:   - Fine collagen networks providing support in soft organs.

• Elastic Fibres:   - Flexibility and resilience (e.g., in blood vessels).

Classification of Connective Tissues

1. Loose Connective Tissue:    - Also known as areolar tissue; found widely throughout the body.    - Composed of a mix of ground substance and all three types of fibers.

2. Adipose Tissue:    - Mainly adipocytes, serving as energy storage, insulation, and protection.

3. Dense Connective Tissue:    - Thick and densely packed fibers (e.g., tendons and ligaments).    - Classified into dense regular, dense irregular, and dense elastic tissues.

Specialized Connective Tissue

• Types of Specialized Connective Tissue:   - Bone:     - Containing osteocytes, a rich extracellular matrix.   - Blood:     - Contains various cell types and a liquid matrix (plasma).   - Cartilage:     - Contains chondrocytes; avascular and takes longer to heal; three types include hyaline, elastic, and fibrocartilage.

Summary of Connective Tissue

• Connective tissue is diverse in function and structure and encompasses a wide range of cells and functions crucial for maintaining bodily systems.

Muscle Tissue

• Learning Outcomes for Muscle Tissue:   - Describe the three muscle types and their characteristics.   - Explain organization of muscle tissue.   - Discuss the structure of muscle fibers.

Types of Muscle Tissue

1. Skeletal Muscle:    - Long fibers, multinucleated, and striated.    - Voluntary control; requires nervous system input.

2. Cardiac Muscle:    - Branched, striated, usually mononucleated, with intercalated discs for strength and communication.    - Involuntary control; specialized pacemaker cells regulate contractions.

3. Smooth Muscle:    - Non-striated, involuntary muscle found in various systems (circulatory, digestive, reproductive).    - Small cells that can initiate contraction through various stimuli (nerves, hormones).

Nervous Tissue

• Learning Outcomes for Nervous Tissue:   - Describe structure and classification of neurons.   - Explain the role of neuroglia.   - Define chemical and electrical gradients; explain resting membrane potential.

Components of Nervous Tissue

• Neurons:   - Cells responsible for processing and transmitting signals; typically non-dividing.   - Varied sizes affecting transmission times.

• Neuroglia:   - Supporting cells that provide nourishment and support to neurons; include six types categorized into CNS and PNS:     - CNS Types: Astrocytes, oligodendrocytes, microglial cells, and ependymal cells.     - PNS Types: Schwann cells and satellite cells.

Synapses and Communication

• Synapses:   - Points of communication between neurons (chemical and electrical).

Membrane Potential Across Neurons

• Key Concepts:   - Neurons generate electrical changes; resting membrane potential varies due to ion concentration gradients.   - Changes in ion permeability can signal physiological responses.

Summary of Nervous Tissue

• Comprised of neurons and neuroglia, which work alongside electrical gradients to regulate bodily functions and responses.

Integumentary System

• Learning Outcomes for the Integumentary System:   - List major membranous types—cutaneous, mucous, serous, and synovial; compare structures.   - Recognize components of the skin (epidermis, dermis).   - Understand contributions of various tissue types in integumentary functions.

Overview of Membranes

• Four types of membranes present in the body:   - Mucous Membranes: Line cavities that open to the exterior.   - Serous Membranes: Line closed body cavities.   - Cutaneous Membrane: Skin itself.   - Synovial Membranes: Line joint cavities.

Functions of the Integumentary System

• Largest organ system, serving multiple functions including:   - Protection against external attacks.   - Regulation of body temperature.   - Sensory reception.   - Excretion of wastes.

Skin Structure

• Components Include:   - Epidermis: Outermost layer composed of keratinized stratified squamous epithelium.   - Dermis: Deep layer consisting of connective tissue features.   - Accessory Structures: Hair and glands.

• Key Functions of Skin:   - Provides a protective barrier, regulates fluids, synthesizes Vitamin D, and facilitates sensation and thermoregulation.

Summary of the Integumentary System

• Includes a variety of membranes and structures that function in protection, sensation, and regulation of the body environment.