Ti Tissues sues Dr.shatarat 1 6/15/2013 . Types Tissues are - - PowerPoint PPT Presentation

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Ti Tissues sues

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Types

Tissues are classified into 4 types according to their structure and function:

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1. Epithelial tissues 2. Connective tissues 3. Muscular tissues 4. Nervous tissue

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• 1. Epithelial tissues

1.Act as a selective barriers that limit or aid the transfer of substances into and out the body. 2.Produce secretions on their free surfaces.

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Major functions:

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1-Cellularity

(Packed cells) cells are in close contact with each other with little or no intercellular space between them

2-Specialized contacts

may have junctions for both attachment and communication 4-Avascular

nutrients must diffuse from near by connective tissue to reach the epithelial cells

6-Regeneration

epithelial tissues have a high capacity for regeneration

High risk of cancer

5-Innervated

3-Polarity

Epithelial tissues always have an apical and basal surface (Healing of wounds?)

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Three types of junctions What is the function of Gap Junctions? Gap junctions serve as passageway between two adjacent cells by allowing small molecules move directly between neighboring cells

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at the apical (apex / Top) surface First name of tissue indicates number of layers Stratified – more than one layer of cells Simple – Cells arranged in one layer.

Classification of epithelial tissue

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1-According to the number of layers, epithelium is divided into: 1- Simple 2-Stratified

Last name of tissue describes the shape of the cells A- Squamous cells (flat): Are thin, like a plate. B-Cuboidal cells: shaped like cubes C-Columnar cells: like columns.

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2-According to the shape of each cell, the epithelium is divided into: 1-Squamous 2- Cuboidal 3-Columnar

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I. Simple epithelium

When we combine the 2 characters (cell shapes and the number of layers), epithelial tissue has the following types:

a. Simple squamous. b. Simple cuboidal. c. Simple columnar (nonciliated and ciliated) d. Pseudostratified columnar (nonciliated and ciliated)

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simple epithelium

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• A. Simple squamous epithelium

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Functions:

Filtration Diffusion Secretion Formed of a single layer of flat cells and can be found in: 1-Mesothelium: it is a simple squamous epithelium that covers body’s cavities:

A- Peritoneum B- Pleura C-Pericardium

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4-Renal corpuscles 3-Alveoli of lungs

2- Endothelium: lining the inner surfaces of the heart and blood vessels

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• B. Simple cuboidal

Formed of a single Layer of cube-shaped cells.

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Locations:

Line kidney tubules. Surface of ovary. Ducts of pancreas.

Functions:

Secretion Absorption.

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• C. Simple columnar nonciliated
• Form of single layer of nonciliated column like cells.
• location: lines Gastrointestinal Tract.
• Functions: High capacity of secretion and absorption.

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• D. Simple columnar ciliated
• lines Bronchioles of lung
• lines Uterine tubes

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Formed of a single layer of ciliated column like cells with Goblet cells in between. Locations:

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E.Pseudostratified columnar

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Pseudostratified epithelium:(pseudo= false)

• Tissue appears to be several layers but is

really a single layer.

• Cells nuclei lie at different levels and

cells appear to have multiple layers.

• All its cells rest on the base but not all of

them reach the surface.

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1. Ciliated: Form of cells with cilia and Goblet cells.

• Locations: Lines airways of most of upper respiratory tract.
• Functions: Secretes mucus that traps foreign particles.

2.Nonciliated: Contains cells without cilia and lack goblet cells. Locations: Lines larger ducts of many glands & epididymis. Functions: Absorption and protection.

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• II. Stratified epithelium

Types: a. Stratified squamous

• keratinized
• Nonkeratinized.
• b. Stratified cuboidal epithelium.

c. Stratified columnar epithelium.

• d. Transitional epithelium.

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A-Stratified squamous epithelium

• Forms of several layers of cells.
• Cells in apical layer and some layers deep to it are squamous

(Flat).

• Cells move gradually from deep to superficial away from blood

vessels then die and slough (fall off).

• Found mainly in places subject to attrition (wear and tear) as skin,

mouth, esophagus, vagina).

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Two types:

• Keratinized (dry).
• Nonkeratinized (wet).

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Keratinized stratified squamous :

• Covers dry surfaces such as epidermis of skin (superficial layer of

the skin). Form tough layer of keratin (tough protein) between surface cells.

• Functions:

Protect skin and underlying tissues from heat, microbes, chemicals and water loss.

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Nonkeratinized stratified squamous

• Surface layers contain small amount of keratin and always wet.
• Location: Lines wet surfaces as Mouth and Esophagus.
• Function: Protection against scratch, water loss, ultraviolet radiation, and

foreign invasion.

• Both types form first line of defense against microbes.

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D.TRANSITIONAL EPITHELIUM

• Show variable

appearance.

• The form of these cells

changes according to the degree of distention of the

• rgan.
• Locations: Urinary

bladder, ureter.

• Functions: Allow the
• rgan to stretch and

protection from rupturing.

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• B. Glandular Epithelium
• A gland may consist of a single epithelial cell or a

group of cells adapted for secretion.

• Normally found as:

– Unicellular glands as Goblet cells. – Multicellular glands group of cells as Salivary glands.

• All glands of the body are classified into:

– Exocrine (Exo=outside, crine=secretion): Secrete substances

• nto a surface by ducts.

– Endocrine: Secrete hormones into the blood. – Mixed (exocrine and endocrine): e.g.. Pancreas

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Functional classification of exocrine glands

1-Merocrine glands (mero=a part):

• Secretions are released via exocytosis.
• Most exocrine glands of the body are

merocrine glands. 2-Apocrine glands (apo= from):

• Secretion collected at the apical part of

the cell then pinched off by exocytosis. 3-Holocrine glands (holo= entire):

• Secretion collected in their cytosol.

When cell matures, it ruptures and becomes the secretory product. e.g. sebaceous gland.

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Based on the releasing mode of their secretions and whether the secretion is a product of a cell or consists whole or a part of the cell they are divided into: