Which Characteristic Distinguishes Epithelial Tissues From Other Types Of Animal Tissue?
What is epithelium? A quick overview
Epithelial tissue or Epithelium (plural = epithelia) is a protective, continuous sheet of compactly packed cells. Epithelium covers all internal and external surfaces of our torso, and lines trunk cavities and hollow organs. Epithelium also forms major tissues in all glands.
[In this image] Epithelium is one of the 4 basic types of animal tissue, along with connective tissue, musculus tissue, and nervous tissue.
The function of the epithelium varies depending on where information technology's located in your torso. Examples include protection, secretion, awareness, and absorption.
[In this paradigm] Examples of epithelial tissues and their functions.
To assist you lot take a quick thought of what epithelial tissues tin do, here are some examples:
- Epithelium forms the outer layer of your skin (chosen epidermis).
- Specialized epithelium forms secretory organs similar sweat glands and thyroid glands.
- Epithelial cells line the airway of our respiratory tract, waving their pilus-like cilia to prevent dust and pathogens from inbound our lungs.
- Epithelial cells line the inner surface of our digestive tract. In the intestines, these epithelial cells absorb nutrients from the digested nutrient.
Characteristics of epithelial tissue
Epithelial cell sheets and cellularity
Epithelial tissue is formed by a tightly packed continuous layer ofepithelial cells. There is piffling intercellular fabric or matrix present between epithelial cells. Instead, epithelial cells stay very close to each other, leaving no space between neighbors. Epithelial tissue has loftier cellularity (Epithelial tissue mainly comprised cells).
In comparison, cells in the connective tissues are separated from each other and embedded in a matrix. Thus, the connective tissue is low cellularity.
[In this image] Epithelial tissues are tightly packed prison cell sheets, in which epithelial cells attach firmly to each other. These cell sheets may consist of only a single layer of cells or a stack of multilayered cells.
Intercellular adhesion and other junctions
Epithelial cells use specialized junctions to link adjacent cells tightly together. These junctions include:
- Tight junctions – provide a strong bonding betwixt neighboring cells and foreclose leakage across tissues
- Adherens junctions– link the cytoskeleton from two adjusted cells together and transmit mechanical forces
- Gap junctions – facilitate the movement of ions and molecules across the tissue
[In this image] Cell junctions link epithelial cells into tissues.
[In this image] Adherens junctions link actin cytoskeleton from ii adjacent cells together.
[In this prototype] Gap junctions serve equally channels for the exchange of small molecules between cells.
Polarity
To maintain the integrity of epithelial barriers, epithelial cells tend to be in a cube or cuboid shape. As we know, a cube has six faces or sides; each face of an epithelial cell is different. This intrinsic asymmetry observed in cells is calledCell polarity.
Theupmost face of the epithelial tissue is exposed to either the external environment or the body fluid. Thelateral faces are the iv sides closely linked to the neighboring cells past intercellular junctions. The basal face is attached to the underneath connective tissues by the basement membrane.
Basement membrane
The basement membrane separates the epithelia from the underlying connective tissues. The basement membrane can exist further divided into two parts. The basal lamina (close to the epithelium) consists of fibers and polysaccharides secreted by epithelial cells. The reticular lamina (close to the connective tissue) is rich in collagen proteins produced past cells of connective tissues, also known as the fibroblasts.
[In this paradigm] Most epithelial cells are separated from the connective tissue by a canvass of extracellular fabric called basement membrane. It is formed by the clan of two layers: Basal lamina and Reticular lamina.
Paradigm credit: Socratic Q&A
Avascular and innervated
Claret vessels don't grow into the epithelial tissues therefore chosen avascular. Instead, epithelial cells receive their nutrients from capillaries in the underlying connective tissues. The commutation of chemicals between epithelial and connective tissues is accomplished through improvidence.
Although blood vessels do not penetrate epithelial tissues, nervus endings do; that is, epithelia are innervated, pregnant they accept their own supply of nerves.
[In this paradigm] A summary of key characteristics of epithelial tissues.
Regeneration
Equally epithelia line all the external and internal surfaces to protect our body, epithelial cells are constantly exposed to hostile substances such equally leaner, acids, and smoke. Fortunately, our epithelial tissues display a high regenerative capacity. Every bit long as epithelial cells receive adequate diet, they can quickly replace dead cells by cell division to catch up with a high turnover.
[In this video] Quick proliferation of man kidney epithelial cells in a culture dish.
Development
Epithelial tissues tin can derive from all 3 embryological germ layers:
from ectoderm (e.g., the epidermis);
from endoderm (e.g., the lining of the digestive tract);
from mesoderm (e.g., the inner linings of body cavities).
Sometimes, endothelium and mesothelium (both derived from mesoderm) are likewise listed every bit epithelium. However, many scientists do non count endothelium and mesothelium as "true" epithelium.
The structure of epithelial cells
Like all other cells, epithelial cells are enclosed within a cell membrane. Each jail cell has ane cell nucleus and several organelles, including mitochondria, endoplasmic reticulum, ribosomes, Golgi apparatus, peroxisomes, and lysosomes.
[In this image] The beefcake of epithelial cells.
Epithelial cells have all the common jail cell organelles like other animate being cells. Some epithelial cells take hair-similar protrusions (cilia or microvilli) on their apical sides.
Some epithelial cells have unique characteristics on the cell surface that help them perform certain functions.
Cilia
Cilia are tiny, hair-similar structures on the surface of some epithelial cells. Ciliated cells usually accept hundreds of cilia on their surfaces. Their cilia can wave in a coordinated mode to sweep small objects abroad from the epithelium-lined surface.
For example, epithelial cells lining our airway have cilia that trap grit, bacteria, and other substances that you breathe in and movement them toward your nostrils and then that they don't go into your lungs. Some other example of cells with cilia are the epithelial cells that line the fallopian tubes that help motility an egg from an ovary to the uterus.
[In this image] Tiny hair-similar cilia are observed on the upmost sides of trachea epithelial cells under a loftier magnification low-cal microscope. Ciliated epithelium lines most parts of our upper airway.
Microvilli
Microvilli are tiny finger-like structures on the surface of abdominal epithelial cells. Unlike cilia, microvilli don't move. Even so, they tin increment the jail cell'due south surface area so that information technology can absorb substances efficiently. Each small intestine epithelial prison cell may have thousands of microvilli that absorb nutrients from the nutrient you eat and protect your body from intestinal bacteria.
[In this epitome] Manual electron microscopy image of small-scale intestine epithelium surface covered by the dumbo microvilli.
Image credit: Atlas of found and animal histology
Stereocilia
Stereocilia are specialized microvilli that resemble cilia and project from the surface of auditory and vestibular sensory cells. For instance, stereocilia are needed on the epithelial tissue in your inner ear for hearing and balance.
[In this image] Colored scanning electron microscopy prototype of a agglomeration of stereocilia on the inner ear epithelium.
Image credit: Estereocilios
Types of epithelia
In general, epithelial tissues are classified by the number of layers, the prison cell shape, and the office of the cells. Hither is just a quick summary of common types of epithelial tissues. See "Classification and Types of Epithelial Tissues" for more detailed explanations and examples.
System
Three types of epithelial tissue arrangements – Epithelial tissues could form past cells assembling in Simple (simply one layer), Stratified (multiple layers), and Pseudostratified (one layer of cells with different sizes resulting in a multilayered appearance) arrangements.
[In this image] Schematics of simple, stratified, and pseudostratified arrangements of epithelial cells.
Shape
3 types of epithelial cells based on their shapes – Epithelium may consist of cells that are Squamous (apartment and scale-like), Cuboidal (cube-like), and Columnar (taller, cavalcade-similar) in appearance.
[In this prototype] Schematics of Squamous, Cuboidal, and Columnar shapes of epithelial cells.
Part
Some unique epithelial tissues are categorized by their special functions, including Transitional (can become flattened when stretched), Glandular (tin secrete substances and grade the glands), Mucous (tin produce fungus), Serous (lines the trunk cavities), and Olfactory (involves in the sense of smell).
Given the dissimilar shapes and arrangements of epithelial cells, at that place can be several types of epithelial tissue in combination. Examples are Simple squamous epithelium (a single, flat layer of cells forming the alveoli of lungs), Simple columnar epithelium (a single, thick layer of cells lining the stomach and intestines), Stratified squamous epithelium (multilayered cells forming the outer layer of skin), Stratified cuboidal epithelium (forming the ducts of salivary and sweat glands), and Pseudostratified columnar epithelium (lining our upper respiratory tract and usually has a lot of cilia).
[In this image] A summary of eight types of epithelial tissues and examples. To learn more, see "Classification and Types of Epithelial Tissues".
Functions of epithelium – What does the epithelium exercise?
Epithelium plays many important functions that are vital to our life. Since epithelial cells are found throughout our body, they adapt to unlike functions based on their location and organs' needs.
[In this epitome] Epithelial tissues pick up specialized functions to fit the needs of different organs in our body.
Epithelium can take ane or a combination of the following functions:
Protection
As epithelial tissues embrace the entire body surface, their primary function is serving as the first line of defense against all kinds of pathogens, injury, and chemicals. For case, the outer layer of our peel is a thick epithelial tissue called the epidermis. Information technology protects your body from impairment, keeps your body hydrated, produces new pare cells, and contains melanin, which determines your peel colour.
Epithelium likewise protects our respiratory tract. Cilia presented by epithelial cells in the nose or upper respiratory tract help trap the dust particles and foreclose them from entering the lungs.
[In this paradigm] Examples of epithelial tissues that function as a protective barrier are the epidermis (skin), stomach wall epithelium, and ciliated airway epithelium.
Secretion
Epithelial tissues in diverse exocrine and endocrine glands (i.eastward., thyroid, salivary glands, sweat glands, mammary glands) can secrete hormones, enzymes, saliva, mucus, sweat, milk, fluids, etc. Major organs similar the liver and pancreas are too secretory organs. For glands that release substances through secretory ducts, these ducts are also made of epithelial tissues.
[In this image] Examples of epithelial tissues that secrete essential substances for our body: pancreatic juice and insulin from pancreas; saliva from sublingual gland; and thyroxine from thyroid gland.
Examples of epithelial tissues that secrete essential substances for our torso:
i. Pancreas has both exocrine and endocrine functions. Acinar epithelium (exocrine) secrets the pancreatic juice through the pancreatic duct into the intestines to help nutrient digestion. Pancreatic islets (endocrine) secrete insulin directly into the bloodstream to regulate claret sugar levels.
2. Sublingual glands are a pair of salivary glands (exocrine) situated underneath the natural language. They produce saliva in the mouth.
3. Thyroid (endocrine) is a butterfly-shaped gland that sits depression on the forepart of the neck. It secretes several thyroid hormones into the bloodstream.
Lubrication
Mesothelium is a layer of epithelium that lines our trunk cavities, such as the peritoneum (abdomen cavity), pleura (lung cavity), and pericardium (heart cavity). Mesothelium also surrounds the internal organs. Mesothelium secretes a lubricant pic called serous fluid, which prevents the frictions betwixt organs and body walls during motility, animate, or heart beating.
[In this prototype] Mesothelium covers the torso wall and the organs.
(Left) Mesothelial cells lining the cavities/body walls in these subdivisions are called parietal mesothelia, while visceral mesothelia cover the organs. (Right) The size and location of our lungs alter during each breath. For this reason, the lubricant layer between parietal pleura (mesothelia lining the chest crenel) and visceral pleura (mesothelia covering the lungs) is critical to reduce the fraction and foreclose injury.
Absorption
The epithelial lining of the digestive tract absorbs water and nutrients. For instance, the intestine epithelial cells forming villi can increment the surface area of cells and blot nutrients from the food we eat.
[In this image] Villi organization of small intestine epithelium.
Image source: Atlas of found and animal histology
Substitution of substances
Epithelial tissues control the substitution of substances betwixt the torso and the external environs. For example, the oxygen/carbon dioxide exchange in our lungs happens across the thin epithelial layer of alveoli.
[In this image] Simple squamous epithelium lines the surface of alveoli (singular: alveolus) and serves as the site for gas commutation.
Filtration and excretion
Excretion is the removal of waste product from our bodies. The epithelial cells in the kidneys form renal tubules to filter and make clean the blood. These cells filters waste product from the claret into the fluid (which becomes urine) as it flows through the tubules. They too reabsorb and return needed h2o, electrolytes, and nutrients (such every bit glucose and amino acids) dorsum to the claret.
[In this epitome] Nephron is the kidney's microscopic structural and functional unit. A nephron consists of a tuft of capillaries, called the glomerulus, and renal tubules made of tubule epithelial cells.
Sensation
Sensory nerve endings are present in the epithelial tissues of the skin, olfactory organ, ears, taste bud, etc. These receptors can receive outside sensory stimuli and transmit signals to the brain. For example, the stereocilia on the surface of the ear epithelial tissues are essential for hearing and balance. In addition, your taste buds sit in the stratified squamous epithelium of your tongue.
[In this image] Examples of epithelial tissues that host sensory nerves are the tongue epithelium with sense of taste buds.
Image source: Histology at SIU
Diseases – What weather condition affect epithelial tissue?
Cancer
I of the biggest concerns with epithelial tissue is the potential for malignancy evolution (a bad side of their robust regeneration adequacy). The types of cancer that initiate from epithelial tissues are called carcinomas.
Carcinomas are the most common type of cancer. They make up about 85 out of every 100 cancers in the U.s.. Based on their origins, carcinomas include squamous jail cell carcinoma, adenocarcinoma, transitional cell carcinoma, and basal cell carcinoma, etc.
[In this image] Cancer cells plunder the nutrients from surrounding cells and tissues to sustain the rapid growth of tumors.
In addition to cancer, various organs can develope disease. Examples are asthma (airways), celiac disease (intestines), vertigo (ears), dermatitis (skin), etc.
Look at epithelial cells nether a microscope
Project 1 – Wait at your cheek cells
The tissue that lines the inside of our oral fissure is known as the basal mucosa. This protective layer is composed of stratified squamous epithelial cells or cheek cells. These cells divide approximately every 24 hours and are constantly shed from the surface of our mouth. Quick jail cell turnover makes sure whatsoever damage to this protective barrier is repaired as soon as possible.
[In this epitome] Cheek cells (epithelial cells) form a protective barrier lining your oral cavity. You lot tin can easily obtain your cheek cells for your microscope projection by scraping the inside of the oral fissure using a make clean cotton swab. Come across more details hither.
Project ii – Study premade histological slide sets
All colorful pictures in this article are taken from my collection of professional slides for histological report.
Histology is the branch of biology that studies biological tissues' microscopic anatomy. In lodge to see the particular of individual cells in the tissues or organs, the specimens accept to exist cutting into very thin sections. To practice so, a professional microtome and special chemic treatments are required. Below is the typical process to prepare professional microscopic slides:
(1) The tissue is grossly cutting into a suitable piece and placed in a cassette. Soft animal tissues require chemic fixation (including formalin and alcohol) to preserve the cell structures.
(2) The specimen is then embedded in a wax-like material chosen paraffin to become a difficult, solid cake.
(iii) A professional person rotary microtome.
(4) Carefully identify the specimen block and the sectioning blade.
(5) By rotating the drive bike, the blade will trim a thin section of the specimen cake like the peeler in the kitchen. Each department can be as thin as 3 micrometers (1/30 the thickness of your hair!) Series of sections can exist cut similar a ribbon. The ribbon will then be moved to a water bathroom for flotation. The proficient sections will be selected and transferred to the glass slide.
(6) Depending on the purpose of the specimen, the slides can be stained with specific stains, so washed, dried, and permanently mounted with coverslips.
[In this paradigm] The steps of histological slides preparation.
Hematoxylin and eosin stain (or H&Eastward stain) is one of the most mutual stains used in histology. The hematoxylin stains cell nuclei a purplish bluish, and eosin stains the matrix and cytoplasm pinkish. Most pictures of epithelial tissues we saw in this article are done by H&E stain.
None of us can take these professional microtomes and special chemicals at home. Only don't worry, you lot tin can purchase premade slide sets. At that place are all kinds of slide sets on Amazon.com, from 10 to 200 slides per prepare with different contents.
You can check out our 25 Microscope Prepared Slide Set, which includes 6 slides of human being histology (claret, trachea, tum, liver, pancreas, and brain).
Summary
1. Epithelial tissue or Epithelium (plural = epithelia) is a protective, continuous sheet of compactly packed cells. Epithelium covers all internal and external surfaces of our body, and lines torso cavities and hollow organs.
2. Characteristics of epithelial tissue include cell sheets and cellularity, cell junction, polarity, basement membrane, high regeneration, nervus innervation and lack of blood vessels.
3. Epithelial cells have all the common cell organelles like other animal cells. Some epithelial cells have hair-like protrusions (cilia or microvilli) on their apical sides.
4. Epithelial tissues are classified by the number of layers and by the shape or the function of the cells. Epithelial tissues could form past cells assembling in Unproblematic (just one layer), Stratified (multiple layers), and Pseudostratified (1 layer of cells with unlike sizes resulting in a multilayered advent). Cell shape includes Squamous (apartment and calibration-like), Cuboidal (cube-like), and Columnar (taller, column-similar).
5. There are 8 types of epithelial tissue: simple squamous, simple cuboidal, unproblematic columnar, pseudostratified columnar, stratified squamous, stratified cuboidal, stratified columnar, and transitional epithelia.
6. Major functions of epithelia are protection (peel), secretion (thyroid), absorption (intestine), gas commutation (lung), secretion (liver), and filtration (kidney).
7. Carcinomas are the nearly common type of cancer, which initiated from epithelial tissue (a bad side of their robust regeneration capability).
viii. How to look at epithelial cells nether a microscope? ane. Look at your cheek cells. 2. Report premade histological slide sets.
Extended Reads
Classification and Types of Epithelial Tissues
References
"Epithelium" past Cleveland Dispensary
Source: https://rsscience.com/epithelium/
Posted by: pragertharsen.blogspot.com
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