Chapter_5_PPT.pptx

Chapter 5 Lecture Outline: Anatomy & Physiology

Introduction

Tissue Definition:Tissues are defined as groups of similar cells and their extracellular matrix that work together to perform specific functions. These functions are critical for the overall homeostasis of the body and include aspects such as protection, movement, and communication among cells. The formation of tissues allows for increased complexity in biological systems and facilitates specialized functions.

Four Types of Tissues:

1. Epithelial Tissue

2. Connective Tissue

3. Muscle Tissue

4. Nervous Tissue

5.1 Epithelial Tissue Characteristics

5.1a Overview

• Cellularity:Epithelial tissues are composed primarily of closely packed cells with minimal extracellular matrix, enhancing their ability to form barriers and control permeability. This characteristics allows for quick and efficient transport of substances.

• Polarity:Epithelial cells exhibit polarity, meaning they have distinct apical and basal surfaces. The apical surface may have specializations such as cilia or microvilli, further enhancing function depending on their location.

• Avascularity:There are no blood vessels within epithelial tissue; instead, they receive nutrients through diffusion from underlying connective tissues.

• Regeneration:Epithelial cells have a high regeneration capacity due to frequent cell division, allowing them to repair quickly after injury.

5.1b Functions

1. Physical Protection:Protects underlying tissues from damage, dehydration, and microbial invasion.

2. Selective Permeability:Regulates the passage of substances in and out of tissues.

3. Secretions:Specialized epithelial cells, such as goblet cells, secrete substances like mucus, enzymes, and hormones.

4. Sensation:Epithelial tissues contain sensory nerve endings, transmitting information regarding environmental changes to the nervous system.

5.1c Classification

• By Number of Cell Layers:

  1. Simple Epithelium:

  • Composed of a single layer of cells, allowing for efficient absorption and secretion.

  2. Stratified Epithelium:

  • Multiple layers providing additional protection against physical stress.

  3. Pseudostratified Epithelium:

  • Appears layered but consists of a single layer of irregularly shaped cells.

• By Cell Shape:

  1. Squamous:

  • Flat, wide cells allowing for rapid diffusion and filtration.

  2. Cuboidal:

  • Cube-shaped cells involved in secretion and absorption, with a spherical nucleus located centrally.

  3. Columnar:

  • Tall, column-like cells that are often involved in secretion and absorption, typically containing oval nuclei.

  4. Transitional:

  • Specialized for stretching, these cells can change shape, found in areas like the bladder.

5.2 Connective Tissue Characteristics

General Overview

• Origin:All connective tissues originate from mesenchyme, a type of embryonic tissue.

• Components:Composed of cells, protein fibers, and ground substance (extracellular matrix), providing structural and functional support. The matrix can vary in consistency, influencing the characteristics of the tissue.

5.2a Types of Cells

1. Resident Cells:Permanent cells that maintain and repair the tissue (e.g., fibroblasts, adipocytes).

2. Wandering Cells:Cells that move through tissue spaces to perform functions typically related to immune response (e.g., leukocytes).

5.2b Functions

• Physical Protection:Supports and protects various structures in the body.

• Support:Provides framework for the body, ensuring integrity of organs, muscles, and other tissues.

• Binding Structures:Connective tissues bind structures together, facilitating movement and stability.

• Storage:Stores energy reserves (e.g., adipose tissue) and minerals (e.g., bone).

• Transport:Blood acts as a transport medium for gases, nutrients, and waste products.

• Immune Protection:Attacks pathogens and prevents infection through the activity of wandering cells.

5.2c Embryonic Connective Tissue

• Mesenchyme:The first connective tissue formed during embryonic development that gives rise to all other connective tissues.

• Mucous Connective Tissue:Found predominantly in the umbilical cord, providing structural support.

5.2d Classification of Connective Tissue

1. Connective Tissue Proper:

   • Loose Connective Tissue:Provides elasticity and cushioning.

   • Dense Connective Tissue:Provides strength and stability.

2. Supporting Connective Tissue:

   • Cartilage:Provides flexible support; types include hyaline, elastic, and fibrocartilage.

   • Bone:Provides rigid support and facilitates movement.

3. Fluid Connective Tissue:

   • Blood and Lymph:Transport nutrients, waste, and immune responses.

5.3 Muscle Tissue Characteristics

Types:

1. Skeletal Muscle:

   • Voluntary control, striated appearance, and multinucleated. Responsible for body movement.

2. Cardiac Muscle:

   • Involuntary control, specialized striated muscle with intercalated discs. Essential for heart contractions and blood circulation.

3. Smooth Muscle:

   • Involuntary control, non-striated, spindle-shaped cells found in the walls of internal organs. Essential for peristalsis and controlling blood flow.

5.4 Nervous Tissue Characteristics

• Components:Neurons, which transmit signals, and glial cells, which provide support and protection for neurons.

• Functions:Neurons facilitate communication within the body while glial cells play key roles in homeostasis, forming myelin, and providing support for neurons.

5.5 Organs and Membranes

• Organs:Composed of multiple tissue types that collaborate to perform complex functions (e.g., stomach combines epithelial, connective, muscle, and nervous tissues).

• Body Membranes:Comprised of epithelial layers attached to connective tissue; types include:

  1. Mucous Membranes:Line body cavities that open to the exterior.

  2. Serous Membranes:Line body cavities and cover organs within cavities (e.g., pleura, peritoneum).

  3. Cutaneous Membrane:Another name for the skin; provides physical barrier.

  4. Synovial Membranes:Line synovial joints, producing synovial fluid that lubricates the joints.

5.6 Tissue Development and Modification

Stages of Development

• Fertilization:Initiates the formation of an embryo with three primary germ layers:

  1. Ectoderm:Forms the nervous system and skin.

  2. Mesoderm:Develops into connective tissues, muscle, and circulatory system.

  3. Endoderm:Forms internal structures such as the gastrointestinal tract.

Modification Types

• Hypertrophy:Increase in cell size commonly seen in muscle tissues during exercise.

• Hyperplasia:Increase in cell number often occurring during tissue repair or growth.

• Atrophy:Decrease in size or number, often due to disuse or nutrient deficiency (e.g., muscle atrophy).

• Dysplasia:Abnormal development, which could lead to precancerous conditions.

• Neoplasia:Uncontrolled cell growth that can be benign or malignant.

• Necrosis:Tissue death resulting from damage, loss of blood supply, or infection.

Clinical Connections

• Vitamin C and Scurvy:Vitamin C is essential for collagen formation; its deficiency leads to weakened connective tissues, symptoms include bleeding gums and joint pain.

• Marfan Syndrome:Genetic disorder affecting connective tissue, resulting in tall stature, long limbs, and cardiovascular complications due to weak connective structures.

• Tissue Aging:Age-related changes result in reduced cellular function, decreased regenerative capacity, and altered organ performance, affecting all tissue types, leading to conditions such as reduced mobility or osteoporosis.