Histology 2

Page 1: Copyright Notice

• Material reproduced by UNSW under the Copyright Act 1968.

• Contact: j.el-haddad@unsw.edu.au

• Twitter: @orientatewithjoyce

Page 2: Lecture Outline

• Function of Connective Tissue

• Components of CT:

  • Cells

  • Extracellular Matrix (ECM)

• Classification of CT

• Learning Outcomes:

  • LO1: Understand structure and function of cell types in connective tissues.

  • LO2: Understand structure, function of reticular, areolar (loose), and dense connective tissue.

  • LO3: Recognize adipose tissue (white and brown fat) and its functions.

• Textbook Reference: Netter’s Essential Histology

Page 3: Function of Connective Tissue

• Provides:

  • Structural and metabolic support to other tissues

  • Protection, transport, repair, storage.

• Well vascularized (with few exceptions).

• Consists of:

  • Cells

  • Extracellular Matrix (ECM):

    • Fibers

    • Ground substance

• Learning Outcome 1 Overview: Structure and function of cell types in connective tissues.

Page 4: Main Components of Connective Tissue

• Cells

• Extracellular Matrix (ECM)

• Learning Outcome 1 Overview

Page 5: Connective Tissue Cells

• Develop from embryonic mesenchymal cells.

• Classifications:

  • "Blast" (immature)

  • "Cyte" (mature)

• Two groups:

  1. Resident (Fixed)

  2. Wondering (Transient):

     • Migrate from blood due to specific stimuli.

• Learning Outcome 1 Overview

Page 6: Types of Connective Tissue Cells

• Fixed Cells:

  • Fibroblasts

  • Adipocytes

  • Chondroblasts

  • Osteoblasts

• Wondering Cells:

  • Mast cells

  • Macrophages

  • Lymphocytes

  • Plasma cells

  • Eosinophils

• Learning Outcome 1 Overview

Page 7: Mesenchymal Cells

• Primitive stem cells.

• Differentiate into connective tissue, bone, blood, lymph, endothelium, muscle cells.

• Some retain plasticity in adult life.

• Histologically resemble fibroblasts (generally smaller).

• Clinical Context: Sarcomas (tumors of connective tissue), umbilical cord banking.

• Learning Outcome 1 Overview

Page 8: Fibroblasts

• Fibroblasts are basophilic (high organelles, protein synthesis) vs fibrocytes are acidophilic (lower organelles).

• Functions:

  • Synthesize collagen, elastic, and reticular fibers.

  • Active in injury repair and scar tissue formation.

• Learning Outcome 1 Overview

Page 9: Fibroblast Nucleus

• Characteristics of fibroblast nucleus:

  • Eurochromatic: loosely packed, accessible DNA (light staining).

  • Heterochromatic: tightly packed, inaccessible DNA (dark appearance).

Page 10: Adipocytes

• Types of Adipocytes:

  • White Adipocytes:

    • For fat storage, energy, insulation; hormone synthesis.

    • Unilocular; large central lipid droplet, flattened nucleus.

  • Brown Adipocytes:

    • Rich in mitochondria; multipolar.

    • Functions: heat generation, non-shivering thermogenesis; located in back, neck, thigh.

• Learning Outcome 3 Overview

Page 11: Macrophage Function

• Develop from monocytes (WBC).

• Characteristics:

  • Irregular shape, short branched projections.

• Function:

  • Destroy bacteria and cellular debris through phagocytosis.

  • Can be fixed or wandering.

• Learning Outcome 1 Overview

Page 12: Mast Cells

• Develop in bone marrow, differentiate in connective tissue.

• Function:

  • Inflammatory and allergic responses (histamine, heparin granules).

  • Kill bacteria.

Page 13: Extracellular Matrix (ECM)

• Fibers: Collagen, reticular, elastic.

• Ground Substance:

  • Ranges from liquid to solid; water, complex carbohydrates, glycoproteins form a flexible gel.

• Functions:

  • Mechanical/structural support; biochemical barrier regulating metabolic functions for surrounding cells.

Page 14: Types of Fibers

• Collagen:

  • Most abundant; flexible, high tensile strength; made from collagen protein.

• Reticular:

  • Very thin, associated with glycoproteins; provides supporting framework (reticular tissue stroma).

• Elastic:

  • Thin, stretchy (elastin protein); present in skin, lungs, bladder.

Page 15: Collagen and Scurvy Disease

• Importance of collagen in skin care.

• Scurvy: Collagen breakdown due to vitamin C deficiency.

Page 16: Elastic Fibers Features

• Characteristics of elastic fibers.

• Location examples: urinary bladder, lungs.

Page 17: Reticular Fibers

• Provide framework and support for various tissues; key for liver functions.

Page 18: Classification of CT

• Overview of different types of connective tissue

  • Learning outcome related to structure and function.

Page 19: Dense Connective Tissue Overview

• Reinforcement of dense connective tissue functions and characteristics.

Page 20: Dense Regular Connective Tissue

• Characteristics:

  • Abundant collagen fibers, few cells, minimal ground substance;

  • Collagen fibers in uniform bundles; fibroblasts between.

• Functions and locations:

  • Tendons and ligaments; reinforcement of organ attachment.

Page 21: Dense Irregular Connective Tissue

• Characteristics:

  • Mostly collagen fibers, random alignment;

• Functions and locations:

  • Locations: fasciae, deep dermis, digestive tract; resists stretch/tearing in various directions.

Page 22: Elastic Connective Tissue

• Characteristics:

  • Dominated by elastic fibers with fibroblasts in between.

• Locations and Functions:

  • Found in lungs, elastic arteries, select ligaments.

Page 23: Types of Connective Tissue

• Overview of connective tissue classifications:

  • Mature Connective Tissue
    - Specialised CT such as bone, cartilage, bloo
    

Page 24: Loose Areolar Tissue

• Characteristics:

  • All three fiber types, abundant ground substance; well vascularized.

• Functions:

  • Allows movement, inhibits distortion; located in subcutaneous layers, around organs, lamina propria.

Page 25: Loose Reticular Connective Tissue

• Characteristics:

  • Intertwining reticular fibers;

• Functions:

  • Forms stroma, binds smooth muscle cells, filters blood and lymph.

Page 26: Adipose Tissue Overview

• Two types of Adipocytes:

  • White: Fat storage, energy, insulation; synthesis of hormones.

  • Brown: Heat generation, located in specific body areas, rich in mitochondria.