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Lab Activity 4

Classification of Tissues

Martini Chapter 4

Portland Community CollegeBI 231

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Tissues

• Groups of cells similar in structure and function

• Each tissue is then further subdivided into categories.

• All organs are made of a combination of different tissues.

• The four types of tissues

• Epithelial

• Connective

• Muscle

• Nerve

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Epithelial Tissue

Distinguishing Characteristics

1. Cellularity: Composed almost entirely of cells

2. Polarity: apical and basal surfaces (top and a bottom)

3. Attachment: Supported by connective tissue (basement membrane)

4. Avascular: Contains no blood vessels: obtains nutrients by diffusion

5. Regeneration: Rapidly replaces lost cells by cell division

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Classification of Epithelia

1. First name:• Simple: one layer

• Stratified: more than one layer

2. Second name:• Based on the shape of the top layer of cells

• Squamous (flat)

• Cuboidal (square)

• Columnar (rectangle)

3. Two additional categories

• Transitional

• Pseudostratified

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• Squamous

• Cuboidal

• Columnar

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Simple Squamous Epithelium

• Single layer of flattened cells with disc-

shaped nuclei and sparse cytoplasm

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• Top View

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• Functions:

1. Diffusion

• Alveoli in the respiratory system allows for exchange of O2 and CO2

2. Filtration

• Capillaries allow fluid and other substances out and holds blood cells and proteins in

3. Lubrication

• Secretes lubricating substances in serosae

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Simple Cuboidal Epithelium

• Single layer of cube like cells with large,

spherical central nuclei

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• Functions:

1. Secretion

• Glands such as the thyroid are composed of simple cuboidal epithelium and secrete hormones ect…

2. Absorption

• In the kidney, the proximal convoluted tubule is composed of simple cuboidal epithelium and reabsorbs water and other nutrients from the filtered fluid

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Simple Columnar Epithelium

• Single layer of tall cells with oval nuclei toward

the basal surface

• Goblet cells are often found in this layer

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• Functions

1. Secretion

• Example: In the stomach, these cells

secrete digestive enzymes

2. Absorption

• Example: In the intestine, these cells

absorb nutrients

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Pseudostratified Columnar

Epithelium

• Single layer of cells with different heights;

some do not reach the free surface

• Nuclei are seen at different levels

• May be ciliated (PCCE) or non-ciliated

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Epithelium

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Ciliated Epithelium (PCCE)

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Ciliated Epithelium (PCCE)

• Functions

1. Protection

• Example: Lines the upper respiratory tract.

The cilia sweep debris toward the throat

2. Secretion

• Example: May contain goblet cells

(unicellular glands) that secrete mucus

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Stratified Squamous Epithelium

• Composed of several layers of cells

• Top layer flat

• Bottom layers any shape

• Function in protection of underlying areas

subjected to abrasion

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Stratified Squamous

Epithelium

•Non-keratinized

•Composed of several

layers of cells

•Top layer flat

•Bottom layers any

shape

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Non-Keratinized

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Non-Keratinized

• Functions

1. Physical protection against abrasion and pathogens

• Non-Keratinized is associated with “moist” areas

• Mouth

• Throat

• Esophagus

• Anus

• Vagina

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Keratinized

Looks

“flakey” on

the top

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Keratinized

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Keratinized

• Functions

1. Physical Protection

• Found only in the epidermis of the skin

• Keratin is a protein that helps strengthen

the cells against abrasion

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Transitional Epithelium

• Several cell layers, basal cells are cuboidal

• Apical cells are dome shaped when not

stretched

• Apical cells are flat when stretched

• Only found in Urinary System

• Functions:

1. Allows expansion and recoil after

stretching

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Transitional Epithelium

Distended bladder Empty bladder

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Stratified Cuboidal and Columnar

• Typically two cell layers thick

• Rare

• Functions:1. Secretion

• Found in some sweat and mammary glands

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Stratified Cuboidal Epithelium

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Stratified Cuboidal Epithelium

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Stratified Columnar Epithelium

• Limited distribution in the body• To tell the difference between this and

pseudostratified columnar, look at the nucleus.

• The nuclei are lined up in a straight row

• Function1. Protection

• Found in the pharynx, male urethra, lining some glandular ducts, and anus

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Connective Tissue

• 4 Types

1. Connective Tissue Proper

2. Bone

3. Blood

4. Cartilage

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Connective Tissue Features

1. Specialized cells

2. Matrix: Nonliving material between the cells that makes up most of the volume (ground substance + fibers)

• Extracellular fibers

• Ground substance: Composed chiefly of interstitial fluid, cell adhesion proteins, and proteoglycans

• Specific composition varies between tissues (Blood=fluid, Cartilage=gel like, Bone=Solid)

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Connective Tissue Fibers

• Collagen Fibers: Fibrous protein

molecules

• Extremely tough

• High tensile strength

• Strongest type of fibers in connective

tissue.

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Connective Tissue Fibers

• Elastic Fibers: Form branching networks

• Elastin: a rubber like protein that allow it to act like

a rubber band and snap back to its original shape

after it is stretched

• Reticular Fibers: Forming delicate networks

• Fine collagenous fibers (with a different

chemical structure) branch extensively

• Surround small blood vessels and

support soft tissue organs

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Cells of Connective Tissue Proper

1. Fibroblasts: Secrete the matrix

2. Macrophages: Scavenger cells that engulf pathogens or damaged cells

3. Adipocytes: Fat cells

4. Mesenchymal Cells: Stem cells

5. Mast cells: Stimulate local inflammation: contain histamine and heparin

6. Lymphocytes/microphages: WBC involved in immunity

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Areolar Connective Tissue (Loose)

• Gel like matrix

• Contains all 3 fiber types

• Functions:

1. Wraps and cushions organs

2. Holds and conveys tissue fluid

• Locations:

1. Under epithelial tissues

2. Packages organs

3. Surrounds capillaries

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Areolar Connective Tissue (Loose)

Fibroblast

Collagen fiber

Macrophage

Elastic fiber

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Adipose Tissue (Loose)

• Function:

1. Storage of lipid

molecules

2. Insulation

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Reticular Connective Tissue (Loose)

• Network of reticular fibers in a loose

ground substance

• Functions

1. Soft internal skeleton that supports other cell

types

• Locations

1. Lymph nodes

2. Bone marrow

3. Spleen

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Reticular Connective Tissue (Loose)

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Dense Regular Connective Tissue

• Primarily parallel collagen fibers

• Major cell type: fibroblast

• Functions:

1. Withstands great tensile stress pulling in one direction

• Locations:

1. Tendons

2. Ligaments

3. Aponeuroses

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Dense Regular Connective Tissue

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Dense Irregular Connective Tissue

• Irregularly arranged collagen fibers

• Functions:

1. Withstands tension exerted in many directions

2. Provides structural strength

• Locations:

1. Dermis of skin

2. Submucosa of digestive tract

3. Fibrous capsules of organs and joints

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Dense Irregular Connective Tissue

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Elastic Connective Tissue (Dense)

• Dense regular CT dominated by elastic fibers

• Functions:

1. Stabilizes positions of vertebrae and penis

2. Cushions and permits expansion and contraction of organs

• Locations:

1. Between vertebrae

2. Ligaments supporting penis, transitional epithelia

3. Blood vessel walls

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Elastic Connective Tissue (Dense)

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Blood: Hematopoietic Tissue

• Functions:

1.Transportation

2.Immunology

3.Hemostasis

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Bone: Osseous Tissue

• Functions:

1.Lever for muscles

2.Mineral storage

3.protection

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Hyaline Cartilage

• Functions:

1.Stiff but flexible support

2.Reduces friction

between bony surfaces

• Locations:

1.Articular surfaces

2.Larynx

3.Trachea

4.Nasal septum

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Elastic Cartilage

• Functions:

1. Support, but

flexible

• Locations:

1. Ear

2. Epiglottis

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Fibrocartilage

• Functions:

1. Resists

compression

2. Prevents bone-to-

bone contact

• Locations:

1. Meniscus of knee

2. Pubic symphysis

3. Intervertebral

discs

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Skeletal Muscle

• Voluntary

• Multiple

peripheral

nuclei

• Striated

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Skeletal Muscle:

Peripheral Nuclei

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Cardiac Muscle:

Arrow: Intercalated Discs

• One or two

central nuclei

• Striated

• Involuntary

• Found only in

the heart

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Smooth Muscle

• One central nuclei

• No striations

• Involuntary

• Found in hollow organs, blood vessels

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Nervous Tissue

• Functions:

1. Neurons: Electrical signaling

2. Glial cells: Support of neurons

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Nervous Tissue

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The End

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