Histology Biology 2121 Chapter 4. Introduction Histology - the study of tissue Four Tissue Types –1. Epithelial –2. Connective Tissue –3. Muscle Tissue.

Histology Biology 2121Chapter 4

IntroductionIntroduction

• Histology - the study of tissue

• Four Tissue Types – 1. Epithelial – 2. Connective Tissue– 3. Muscle Tissue – 4. Nervous Tissue

Epithelial Tissue

• In the body found as – 1. covering or lining– 2. glandular epithelium

• General Functions– 1. protection– 2. absorption– 3. filtration– 4. excretion– 5. secretion– 6. sensory reception

Characteristics Characteristics • 1. Epithelial tissue - apical (upper )surface and basal

surface (lower)– Basal lamina - beneath the basal surface

• Glycoprotein - adhesive • filter (selective for the upper epithelial tissue)

• 2. Tight fitting tissue– Tight junctions & desmosomes

• 3. Connective tissue base below the basal lamina - ‘reticular lamina’– collagen fibers

• 4. Basal and reticular lamina = ‘basement membrane’

Classification

(1)Simple Squamous(2)Simple cuboidal(3)Stratified squamous(4)Simple Columnar

Classification

Classification - Columnar

Classification-Stratified

Glandular Epithelium

Introduction to Connective Tissue • Major functions

are binding and support – Protection,

insulation, transportation

• 4 classes

• Subclasses

• Mesenchyme – Embryonic

Characteristics of Connective Tissue

• 1. Vascular – Exception - cartilage

• 2. Stem cell - mesenchyme embryonic tissue

• 3. ‘Noncellular’ extracellular matrix– Fewer cells compared to

epithelial tissue – Makes it stronger, resist

abrasion, etc.

What does Connective look like?

• Extracellular matrix – Made of ground substance (‘matrix’) and

fibers.

• 1. Ground Substance– Between cells and holds fibers – Interstitial fluid; cell adhesion

proteins and (fibronectin, laminin); proteoglycans •Cell adhesion proteins allow for cells to attach to matrix

Ground Substance and Matrix• Proteoglycans - protein core

to which ‘glycosaminoglycans (GAGs) are attached (4.7)

– Polysaccharides (- charge); chondroitin; keratin sulfate; hyaluronic acid

– Traps water and forms a gel-like substance

– Allows for nutrients and substances to diffuse between blood and cells.

Fibers • Types

– 1. Collagen• Thick, tough, fiberous; resist

stress– Tendons and ligaments

– 2. Elastic• Long and thinner; made of

elastin; stretch and recoil; helps collagen to return to original shape

– Found in skin, lungs and BVs

– 3. Reticular • Short, fine and collagen;

continuous with collagen fibers• Branch and surround small BVs;

support soft tissue of organs; found in basement membrane of epithelial tissues

Cells Cells • 1. Connective tissue proper – ‘fibroblasts’

– ‘fibrocyte’

• 2. Cartilage – ‘chondroblast’– ‘chrondrocyte’

• 3. Bone – ‘osteoblast’ – ‘osteocyte’

• 4. Blood – hematopoietic stem cells– Blood cells (does not make fluid and is

not located in its tissue

• 5. Additional Cells- leukocytes (mast and phagocytes); plasma cells; macrophages

CellsCells

Above: Tendon- What identify the cell.Middle: Tissue? Cell?Right: Tissue? Cell?

Areolar CT is a general example of what connective tissue looks like

Survey of Connective Tissue Proper (loose CT)Survey of Connective Tissue Proper (loose CT)

Dense CT – CT Proper

Cartilage Cartilage

1. Hyaline Cartilage: firm, glassy matrix in which chondrocytes lie in ‘lacunae’

2. Joints; ribs (costal cartilage)

Cartilage Types

Bone and Blood

Nervous Tissue

• Brain and spinal cord • Cell types

– 1. neurons– 2. supporting cells or ‘neuroglia’

Muscle Tissue • Cellular -

Vascular– myofilaments

(actin and myosin) for movement and contraction

• Three types– 1. Skeletal – 2. Smooth – 3. Cardiac

Membranes that cover and line surfaces Membranes that cover and line surfaces

Membranes

Inflammatory Response and Tissue Repair (online notes) Inflammatory Response and Tissue Repair (online notes)

• 1. Inflammation– Injury, release of inflammatory

chemicals by cells; vasodilation; entry of neutrophils and monocytes; clotting proteins in plasma; scab forms

• 2. Organization– First phase of tissue repair; scab

replaced by granulation tissue (capillaries and other tissue); fibroblast produce growth factors and collagen; becomes a scar tissue

• 3. Regeneration – Surface epithelium regenerates;

epithelium on top of scar tissue replaces the scab