Chapter 4

Tissues

Organization of Tissues Types

There are four major tissue types:

1. Epithelium

2. Connective

3. Muscle

4. Nervous

Characteristics of Epithelial tissue

•High cellularity - lots of densely packed cells with …

•Specialized intercellular contacts - such as tight junctions, desmosomes and gap junctions.

•Basement membranes & other c.t. support - anchors to connective tissue.

•Polarity - it has an apical side and a basal side (a free edge and a fixed edge).

•Avascular - no blood supply. Receive oxygen and nutrients by diffusion

•Highly mitotic - cells readily regenerate.

Free Surface and Attached Surface

• Polarity: – apical and basolateral surfaces

Intercellular Connections• Support and

communication

Tight Junctions

• Between

2 cell

membranes

Gap Junctions

• Allow rapid communications

Desmosomes

• CAMs, dense areas, and intercellular cement

Attachment to Basal Lamina• Hemidesmosomes

Typical arrangement of epithelium

Subcategories of epithelial tissue

i. Simple1. squamous2. cuboidal3. columnar

ii. Stratified1. squamous2. cuboidal3. columnar

iii. Special (doesn’t fall neatly into either of the above)• Pseudostratified columnar• Transitional

Classes of Epithelia

Figure 4–3a

Simple Squamous Epithelium

Simple SquamousTop view

Thyroid tissue

Kidney

Stratified Squamous Epithelium

Stratified squamous

Keratinizing Stratified

Squamous

Keratin layer of dead cells

Simple Cuboidal Epithelium

Figure 4–4a

Simple Cuboidal

Nuclei

Simple squamous cell

Stratified Cuboidal Epithelium

Figure 4–4b

Stratified Cuboidal

Simple Columnar Epithelium

Simple Columnar

Basement membrane

Goblet cells

Stratified Columnar Epithelium

Stratified Columnar

Rare, found in the male urethra and few other places.

Stratified Columnar

Basal layer

Apical layer

Pseudostratified Columnar Epithelium

Pseudostratified columnar a.

Pseudostratified columnar b.

Cilia

Transitional Epithelium

Transitional

Found only in the urinary tract

Glandular Epithelium:

exocrine glands

Modes of Secretion• Merocrine secretion – sweat glands

Modes of Secretion

• Apocrine secretion – mammary glands

Modes of Secretion• Holocrine secretion – sebaceous (oil) glands

Types of Secretions

• Serous glands:– watery secretions

• Mucous glands:– secrete mucins

• Mixed exocrine glands:– both serous and mucous

Unicellular Glands

• Goblet cells are the only unicellular exocrine glands:– scattered among epithelia– e.g., in intestinal lining

Structure of Multicellular Exocrine Glands

• Structural classes of exocrine glands

Figure 4–7 (1 of 2)

Structure of Multicellular Exocrine Glands

Figure 4–7 (2 of 2)

Characteristics of Connective Tissue

• Common developmental origin - it is all from mesoderm

• Mostly well vascularized (except cartilages, tendons and ligaments)

• Low cellularity - the general arrangement is a variable (often scant) number of cells in a non-living matrix.

• The matrix:• fibers of protein (collagen, elastic & reticular)• ground substance (proteoglycans, cell adhesion molecules & interstitial fluid

Connective tissue

Subcategories of Connective tissue

i. Embryonic 1. Mesenchyme

ii. Connective tissue proper1. Loose

a. Areolarb. Adiposec. Reticular

2. Densea. Irregular (elastic or yellow)b. Regular (white fibrous)

3. Cartilagea. Hyalineb. Elasticc.Fibrocartilage

4. Bone (osseous)5. Blood

Mesenchyme

Loose c.t.: areolar

Reticular Tissue

• Provides support

Figure 4–10b

Loose c.t.: reticular

Adipose Tissue

• Contains many adipocytes (fat cells)

Figure 4–10a

Loose c.t.: adipose

Types of Adipose Tissue

• White fat:– most common – stores fat– absorbs shocks– slows heat loss (insulation)

Types of Adipose Tissue

• Brown fat: – more vascularized – adipocytes have many mitochondria– breaks down fat – produces heat

Dense Regular Connective Tissue

• Attachment and stabilization

Dense regular c.t.

Dense regular c.t.: tendon

Dense Irregular Connective Tissue

• Strength in many directions

Figure 4–11b

Dense irregular c.t.

More dense irregular c.t.

Elastic Tissue

• Made of elastic fibers:– e.g., elastic ligaments of spinal vertebrae

Cartilage Matrix

• Proteoglycans derived from chondroitin sulfates

• Ground substance proteins

• Cells (chondrocytes) surrounded by lacunae (chambers)

Cartilage Growth (1 of 2)

• Interstitial growth

Figure 4–13a

Cartilage Growth (2 of 2)

• Appositional growth

Figure 4–13b

Types of Cartilage

• Hyaline cartilage:– translucent matrix– no prominent fibers

• Elastic cartilage:– tightly packed elastic fibers

• Fibrocartilage:– very dense collagen fibers

Hyaline Cartilage

• Reduces friction in joints

Figure 4–14a

Hyaline Cartilage

Elastic Cartilage

• Flexible support

Figure 4–14b

Elastic Cartilage

Fibrocartilage

• Resists compression

Bone• Also called osseous tissue:

– strong (calcified: calcium salt deposits)– resists shattering (flexible collagen fibers)

Bone: compact

Bone

Fluid Connective Tissues

• Fluid connective tissues: – blood and lymph– watery matrix of dissolved proteins– carry specific cell types (formed elements)

Formed Elements of Blood

Figure 4–12

Blood

4 Types of Membranes

1. Mucous

2. Serous

3. Cutaneous

4. Synovial

Figure 4–16

Mucous Membrane

• Mucous membranes (mucosae):– line passageways that have external

connections – also in digestive, respiratory, urinary, and

reproductive tracts

Structure of Mucous Membrane

Figure 4–16a

Serous Membranes

• Line cavities not open to the outside

• Are thin but strong

• Have fluid transudate to reduce friction

Structure of Serous Membrane

Figure 4–16b

Structure of Cutaneous Membrane

3 Types of Fasciae

• Superficial fascia Figure 4–17

3 Types of Fasciae

• Deep fasciaFigure 4–17

3 Types of Fasciae

• Subserous fasciaFigure 4–17

Muscle tissue

• It contracts (shortens with force).• It is irritable (responsive).• There are three types

1. Skeletal2. Smooth3. Cardiac

Skeletal Muscle

• Most abundant

• Striated

• Multinucleate with peripheral nuclei

• Long, parallel fibers

• Voluntary

Skeletal Muscle

Skeletal muscle

l.s c.s.

Smooth Muscle

• Involuntary

• Not striated (hence the name “smooth”)

• Uninucleate

• Small, spindle-shaped fibers

• Found lining the walls of hollow organs

Skeletal Muscle

• Striated, voluntary, and multinucleated

Figure 4–18a

Cardiac Muscle

• Striated

• Uninucleate (occasionally binucleate)

• Short, fat, branched fibers

• Intercalated discs

• Involuntary

• Found in the heart

Cardiac Muscle Tissue

• Striated, involuntary, and single nucleus

Figure 4–18b

Cardiac muscle

Smooth Muscle Tissue

• Nonstriated, involuntary, and single nucleus

Figure 4–18c

Smooth muscle

Neural Tissue

• Also called nervous or nerve tissue:– specialized for conducting electrical

impulses – rapidly senses internal or external

environment– process information and controls

responses

2 Kinds of Neural Cells

1. Neurons:– nerve cells – perform electrical communication

2. Neuroglia:– support cells– repair and supply nutrients to neurons

Neuroglia

Figure 4–19

The Neuron

Figure 4–19

Nervous tissue

Nervous tissueNeurons

That’s it!