Lab Exercise 5 Epithelial and Connective Tissues Portland Community College BI 231

Lab Exercise 5

Epithelial and Connective Tissues

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

Epithelium

• Covers all body surfaces, inside and out

• Is anchored to connective tissue by a layer of glycoproteins and protein fibers called the basal lamina

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Epithelial TissueDistinguishing Characteristics

1. Cellularity: Composed almost entirely of cells2. 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

Functions of Epithelia

• Protection:Skin

• Secretion: glands release secretions

• Absorption: Uptake nutrients

• Sensory: Taste buds

• Filtration: In the kidneys

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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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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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Stratified Squamous EpitheliumNon-Keratinized

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Stratified Squamous EpitheliumNon-Keratinized

• Functions1. Physical protection against abrasion and

pathogens• Non-Keratinized is associated with “moist”

areas• Mouth• Throat• Esophagus• Anus• Vagina

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Stratified Squamous EpitheliumKeratinized

Looks “flakey” on the top

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• 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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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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Pseudostratified Columnar Epithelium

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Pseudostratified Columnar Ciliated Epithelium (PCCE)

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Pseudostratified Columnar 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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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 cells2. 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

• 3 types of fibers include collagen, elastic and reticular

• 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

Blast cells

• Undifferentiated cells (blast = forming)

• Fibroblasts- fount in loose and dense connective tissues (secrete matrix)

• Chondroblasts in cartilage

• Osteoblasts in bone

• Hemocytoblasts in blood

• ‘cytes’ are the mature forms

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Cells of Connective Tissue Proper

1. Reticular cells: specialized fibroblasts found in reticular connective tissue

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

3. Adipocytes: Fat cells

4. Plasma cells: produce antibodies

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

6. Leukocytes: WBC involved in immunity

Mesenchyme

• Embryonic Connective tissue

• Gel-like ground substance with fine protein fibers and immature cells; gives rise to all other connective tissues

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Areolar Connective Tissue (Loose)

• Gel like matrix• Contains all 3 fiber types• Functions:

1. Wraps and cushions organs2. Holds and conveys tissue fluid

• Locations: 1. Under epithelial tissues2. Packages organs3. 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

• Functions1. Soft internal skeleton that supports other cell

types

• Locations1. 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. Tendons2. Ligaments3. 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 penis2. Cushions and permits expansion and

contraction of organs• Locations:

1. Between vertebrae2. Ligaments supporting penis, transitional

epithelia3. Blood vessel walls

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Elastic Connective Tissue (Dense)

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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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Bone: Osseous Tissue

• Functions:1.Lever for muscles

2.Mineral storage

3.Protection

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Blood: Hematopoietic Tissue

• Functions:1.Transportation

2.Immunology

3.Hemostasis

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The End

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Lab Exercise 5 Epithelial and Connective Tissues Portland Community College BI 231