عملي Oral

Epithelial Tissue M.Sc. Sarah Ahmed

انسجة عملي / د . سارة (م 1 – 3 ) ثاني اسنان موصل 8 / 12 / 2015 (م 1)

Epithelial Tissue

Makes up 3% of your body weight Their cells are all touching one another Of all tissues, they are the most widely varied in structure and function

Locations of Epithelial Tissues

Covers the body (epidermis) Found on the inside of hollow organs and the outside of all organs Found above a connective tissue layer (epi = above) Lines the cavities, tubes, ducts, and blood vessels inside the body

Epithelial Anatomy

Apical surface – upper surface that is free or exposed to the “exterior”Basal surface – attached surface (below)

Epithelial Tissues: Covers a body surface or lines a body cavity Forms most glands Functions of epithelium Protection Absorption, secretion, and ion transport Filtration Forms slippery surfaces

Three Basic Shapes

Squamous – like scalesCuboidal – looks like cubesColumnar – longer and look like columns


Simple – single layer of cells; typically found where absorption and filtration occur or a single layer of epithelial is neededsimple squamoussimple cuboidal simple columnarStratified – layers of cells; common in areas where protection is needed like the skinstratified squamousstratified cuboidalstratified columnar

The shape of the nucleus is sometimes important in distinguishing different types of epithelia Nucleus is flattened

Nucleus is spherical

Nucleus is oblong

Squamous Epithelium

Simple – one layerNucleus is flattened Forms solid layer of cells which line blood vessels, body cavities and covers organs in body cavities
Stratified – multiple layersForms epidermis

(a) Simple squamous epithelium

Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia.
Function: Allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae.
Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae).
Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (125x).
Air sacs of lung tissue
Nuclei of squamous epithelial cells



Figure 4.3e Epithelial tissues.
(e) Stratified squamous epithelium
Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers.
Function: Protects underlying tissues in areas subjected to abrasion.
Location: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane.
Photomicrograph: Stratified squamous epithelium lining the esophagus (285x).
Stratified squamous epithelium
Nuclei
Basement membrane
Connective tissue

Cuboidal Epithelium

Simple – one layerRoughly cube shapedNucleus is spherical Line ducts in kidneys where re-absorption and secretion activities take place.
Duct
Cuboid Cells
Duct
Cuboid Cells

Figure 4.3b Epithelial tissues.

(b) Simple cuboidal epithelium
Description: Single layer of cubelike cells with large, spherical central nuclei.
Function: Secretion and absorption.
Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface.
Photomicrograph: Simple cuboidal epithelium in kidney tubules (430x).
Basement membrane
Connective tissue
Simple cuboidal epithelial cells

Columnar Epithelium

Simple – one layerColumn shaped (long and narrow)Lines digestive tract where re-absorption & secretion occurs.

Figure 4.3c Epithelial tissues.

(c) Simple columnar epithelium
Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus- secreting unicellular glands (goblet cells).
Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action.
Location: Nonciliated type lines most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.
Photomicrograph: Simple columnar epithelium of the stomach mucosa (860X).
Simple columnar epithelial cell
Basement membrane


“Pseudostratified Columnar Epithelium”Looks like it has more than one layer because of the position of the nucleusNuclei are positioned at differing levelsCells narrow in the area without the nucleus

Figure 4.3d Epithelial tissues.

(d) Pseudostratified columnar epithelium
Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus- secreting cells and bear cilia.
Function: Secretion, particularly of mucus; propulsion of mucus by ciliary action.
Location: Nonciliated type in male’ssperm-carrying ducts and ducts oflarge glands; ciliated variety linesthe trachea, most of the upperrespiratory tract. Photomicrograph: Pseudostratified ciliated columnar epithelium lining the human trachea (570x).
Trachea
Cilia
Pseudo- stratified epithelial layer
Basement membrane
Mucus of mucous cell



Transitional Epithelium – stratified tissue ; basal cells cuboidal or columnar; surface cells dome shaped or squamous like, depending on degree of organ stretch. Shape of cells depends upon the amount of stretching (ex: bladder)

Figure 4.3f Epithelial tissues.

(f) Transitional epithelium
Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch.
Function: Stretches readily and permits distension of urinary organ by contained urine.
Location: Lines the ureters, urinary bladder, and part of the urethra.
Photomicrograph: Transitional epithelium lining the urinary bladder, relaxed state (360X); note the bulbous, or rounded, appearance of the cells at the surface; these cells flatten and become elongated when the bladder is filled with urine.
Basement membrane
Connective tissue
Transitional epithelium

Epithelial Tissue in Review…