Ch. 5 Tissues

Tissue Organization

Overview

• Tissue Organization is a fundamental concept in understanding the structure and function of organisms.

• It involves the study of various types of tissues and their roles.

Basic Principles

• Cells Working Together: Cells that function together form tissues.

• Histology: The study of tissues is called histology, which examines the microscopic structure.

• Four Major Types of Tissue:

  • Epithelial Tissue: Covers body surfaces and lines cavities.

  • Connective Tissue: Supports and binds other tissues.

  • Muscle Tissue: Responsible for movement.

  • Neural Tissue: Involved in communication and control.

• Anatomical Knowledge: Understanding the anatomy of tissues aids in connecting structures with their functions.

Identifying Tissue Types

• Which is Not a Primary Tissue Type?

  • A. Muscle tissue

  • B. Epithelial tissue

  • C. Collagenous tissue (CORRECT)

  • D. Connective tissue

Key Terminology

• Biopsy: The process of harvesting living tissue for examination, typically via microscopy.

• Fixation: Preservation of tissues in preparation for staining.

• Autopsy: The examination of a deceased body, often to determine cause of death.

• Pathologist: A trained professional that examines tissue slides and performs autopsies.

Clinical Procedures

• Biopsy Process: Removal of tissue for pathological study when growth is noticed.

  • Choices include:

    • A. Autopsy

    • B. Dissection

    • C. Coroner review

    • D. Biopsy (CORRECT)

Preparing Slides for Histological Examination

• Steps Involved:

  • Biopsy: Initial step to collect tissue.

  • Fixation: Using agents like formalin for preservation.

  • Dehydration: Gradually increasing levels of ethyl alcohol.

  • Clearing: Using organic solvents to make tissues translucent.

  • Embedding: In paraffin or plastic to obtain a solid specimen.

  • Microtome Use: Sections of tissue are sliced from the wax block.

Slide Preparation Follow-up Steps

• Tissue Slices: Placed on slides for examination.

• Staining Slides: Dipped in dye mixtures to color various structures.

  • Common Stain: H&E (Hematoxylin and Eosin).

    • Hematoxylin: Colors acidic structures red.

    • Eosin: Colors basic structures blue.

  • Specialized Stains:

    • Silver Salts: Chocolate brown for axons.

    • Chromium Salts: For adrenal medulla.

    • Sudan IV: For adipose tissues.

Basic Embryology

• Primary Germ Layers:

  • Form tissues about two weeks after fertilization.

  • Three Germ Layers:

    • Ectoderm: Forms skin and related structures, nervous tissue, and parts of sensory organs.

    • Mesoderm: Develops muscle, connective tissues, kidneys, and more.

    • Endoderm: Forms epithelial lining of major organs like the digestive and respiratory tracts.

Features of Epithelium

• Characteristics:

  • Covers body surfaces; cells are closely packed and avascular.

  • Consists of glands (exocrine and endocrine).

  • Contains minimal intercellular substance.

  • Attached to a basement membrane binding it to underlying tissue.

  • High mitotic activity and may have modifications on their apical surface.

Basement Membrane

• Structure:

  • Attaches epithelium to connective tissue, contains two layers:

    • Basal Lamina: Secreted by epithelial cells; made of proteoglycans.

    • Reticular Lamina: Produced by connective tissue; contains reticular fibers.

  • Anchoring via desmosomes and hemidesmosomes allows for structural integrity.

Functions of Epithelium

• Main Functions Include:

  • Protection

  • Secretion

  • Lubrication

  • Absorption

  • Special Sensations

  • Reproduction

Classification of Epithelium

• Two Major Categories:

  • Covering and Lining

  • Glandular

Covering and Lining Classification Criteria

• Cell Shape:

  • Squamous (flat), Cuboidal (cube-shaped), Columnar (tall).

• Layers:

  • Simple (one layer) versus stratified (multiple layers).

• Modifications: Includes Goblet cells, cilia, keratinization.

Function of Ciliated Epithelial Cells

• Most Likely Function:

  • B. To move substances along the surface of the epithelium.

Simple Epithelium Types

• 1. Simple Squamous Epithelium:

  • Function: Absorption and diffusion.

  • Location: Alveoli, blood vessels.

• 2. Simple Cuboidal Epithelium:

  • Function: Secretion and protection.

  • Location: Kidney tubules, glands.

• 3. Simple Columnar Epithelium:

  • Function: Absorption and secretion; may contain microvilli and goblet cells.

  • Location: Digestive tract lining.

Stratified Epithelium Types

• Stratified Squamous Epithelium:

  • Function: Protection, includes keratinized and non-keratinized types.

• Stratified Cuboidal Epithelium:

  • Function: Mostly protective.

• Stratified Columnar Epithelium:

  • Function: Protection in limited areas (rare).

Transitional Epithelium

• Function: Allows for distension; found in urinary organs.

• Structure: Changes shape based on the organ's fullness.

Glandular Epithelium

• Exocrine Glands: Have ducts, secrete products onto surfaces.

• Endocrine Glands: Secrete hormones directly into the bloodstream.

Functional Classification of Exocrine Glands

1. Merocrine: Secretes without loss of cellular material (e.g., salivary glands).

2. Apocrine: Part of the cell pinches off (e.g., mammary glands).

3. Holocrine: Entire cell disintegrates (e.g., sebaceous glands).

Connective Tissue General Features

• Functions: Support, integrity, protection.

• Derived: Primarily from mesoderm (embryonic layer).

• Features: Scattered cells in an extracellular matrix (ground substance and fibers).

Classification of Connective Tissue

1. Embryonic Connective Tissue: Restricted to early development.

2. Adult Connective Tissue:

   • Includes Connective Tissue Proper, Cartilage, Bone, Blood.

Connective Tissue Proper Characteristics

• Loose vs. Dense: Refers to fiber density.

• Types of Fibers: Collagenous (white), elastic (yellow), reticular.

• Cell Types: Immature forms (blasts) vs. mature forms (cytes).

Loose Connective Tissue (Areolar)

• Composed of: Permanent and visiting cells, supporting structures.

• Matrix: Gel-like, facilitates diffusion of nutrients.

• Location: Subcutaneous layers, around organs.

Adipose Tissue**

• Specializes in lipid storage.

• Types: Brown (heat generation) and White (energy storage).

Reticular Tissue**

• Structure: Reticular fibers provide a stroma for lymphatic organs.

• Location: Found in spleen, lymph nodes, etc.

Connective Tissue Types: Dense

• Dense Regular Connective Tissue:

  • Predominant collagen fibers, found in tendons and ligaments.

• Dense Irregular Connective Tissue:

  • Randomly arranged fibers, provides strength in multiple directions.

Cartilage Characteristics

• Matrix: Strong and fibrous but avascular.

• Chondrocytes: Primary cell type, live in lacunae.

• Types: Hyaline, Elastic, Fibrocartilage.

• Grows via two methods:

• Interstitial growth: Expansion from within the cartilage itself, allowing for increase in size. (on the surface)

• Appositional growth: Formation of new layers on the surface, contributing to thickness. (within)

Cartilage Types Functionality

• Hyaline Cartilage: Most common type, smooth matrix.

  Found in articulations or joints, like sternum or nose

• Fibrocartilage: High in collagen, strongest cartilage

  Found in intervertebral discs and pubic symphysis

  (Important in females for childbirth)

• Elastic Cartilage: Resilient and flexible

  Found in ear and epiglottis

Bone Characteristics

• Matrix Composition: Calcium hydroxyapatite with collagen fibers.

  Hydroxyapatite- is 85% calcium phosphate, 10% calcium carbonate and other (magnesium and fluoride primarily)

• Two associated CT

  Periosteum- covers the bone

  Endosteum- lines the marrow (medullary) cavity of long bones

• Key Cells:

• Osteoprogenitors- stem cells in bone

• Osteoblasts- cells that form new bones

• Osteocytes- a cell that lies within the substance of fully formed bone

• Osteoclasts- dissolve and break down old or damaged bone cells

• Bone Types: Compact (dense) vs. spongy (cancellous).

Blood (Vascular Tissue)

• Composition: Formed elements (RBCs, WBCs, and platelets) and plasma.

• Function: Transports gases, nutrients, and hormones.

Functions of Connective Tissue

• Structural framework, energy storage, and organ protection.

Muscle Tissue Characteristics

• Types: Skeletal, Cardiac, and Smooth muscle tissues.

• Unique Traits: Excitability, contractility, and elasticity.

Nervous Tissue Types

• Neurons: Functional units conducting nerve impulses.

• Neuroglial Cells: Supportive cells for neurons.

Clinical Terms Related to Tissue

• Atrophy: Decrease in tissue size.

• Hypertrophy: Increase in size.

• Necrosis: Cell death in tissues.

• Gangrene: Infection and death of tissue due to poor blood supply.