Epithelial tissue Flashcards
Definition of a tissue
is a grouping of similarly specialised cells united in the performance of a particular function.
what are the 4 types of tissue
epithelial
connective
muscle
nervous tissue
what are the types of epithelial tissue
- lining
- glandular
- sensory
- myoepithelium
- germinal
describe myoepithelium
these are muscle cells and contractile cells in glands contract and allow secretion into the duct
describe the sensory epithelial tissue
forms part of the smell and sensory system nerves
describe the germinal epithelial tissue
ovarian surface epithelium, a layer of cells covering the ovary and present in sperm, this is where zygotes are formed
what are the major two types of the epithelial tissue
- lining
- glandular
what are the characteristics
- Cellular polarity – basal v apical
- Polarity means that each cell has a top and bottom, the bottom is called the basal and the top is called the apical.
- The basal sits on the basement membrane in a single layer, if it is in a multiple layer than only the bottom sits on the basement membrane and the more mature move away,
- On the apical surface the epithelial cells are more specialised for example they may have cilia this increases the surface area, they may also have cilia present this helps them move and is powered by ATP
- Sit on a basement membrane; cell surface specialisations - Intercellular junctions – tissues have high cellularity (cell density) and are linked by junctional complexes
- High regenerative capacity, this is in response to damage; they have metaplastic potential which is when one form of epithelium changes to become another form
- They are produced and die very quickly usually in 3-5 days, replaced by new cells that come up and take there place - Avascular, this means that they have no blood vessels within the tissues but are innervated which means that nerve fibres can go between cells
- There are blood vessels present underneath and nutrients diffuse upwards, - They are supported by connective tissue
what does morphology mean
morphology of cells means the shape of the cell
what does it mean if the lining epithelial is simple
means there is only one layer
what does it mean if the lining epithelial is stratified
it means has more than 1 layer of tissue
if stratified what do we look at
- look at the surface layer which is the top layer
- If it is in a tube we look at the cell closest to the lumen
what are the types of epithelial tissue
- Simple squamous (flattened)
- Simple cuboidal – less active so nucleus is higher up
- Simple columnar – rectangle in shape and have the nucleus towards the bottom
- Pseudostratified columnar
describe the cell when it is active
When cells are active the cytoplasm is towards the apical end and the nucleus is towards the bottom such as simple columnar epithelial
describe the simple squamous tissue
single layer of flattend cells with disc shaped central nuclei and sparse cytoplasm
describe the function of the simple squamous
allows passage of materials by diffusion and filtration in sites where protection is not important, secres lubricating substances in serosae
describe the location of the simple squamous tissue
– kideny glomeruli, air sacs of lungs, lining of heart, blood vessels, lining of ventral body cavity, lymphatic vessels
describe the special names for the simple squamous tissue
- Called endothelium when lines blood and lympathic vessels
- Called mesothelium when it lines closed body cavities such as around the heart, the lungs and most of the abdominal contents
describe the function, location and special names of the simple squamous tissue
- Description – single layer of flattend cells with disc shaped central nuclei and sparse cytoplasm
- Function – allows passage of materials by diffusion and filtration in sites where protection is not important, secres lubricating substances in serosae
- Location – kideny glomeruli, air sacs of lungs, lining of heart, blood vessels, lining of ventral body cavity, lymphatic vessels
- Called endothelium when lines blood and lympathic vessels
- Called mesothelium when it lines closed body cavities such as around the heart, the lungs and most of the abdominal contents
describe the simple cuboidal tissue
single layer of cubelike cells with large spherical central nuclei
- This lines tubes and ducts
- Less active
- Larger nuclues
- There is some in the kidney where they are a bit more active
describe the function of the simple cuboidal tissue
secretion and absorpiton
describe the location of the simple cuboidal tissue
kidney tubules, ducts and secretory portions of small glands, ovary surface
- Mainly used in the trasport of bile
- Sometimes you don’t see the cells as other tubules are lined with cells that have greater amounts of cytoplasm so there are fewer seen lining the tubule in a cross section
describe simple columnar
single layer of tall cells with round to oval nuclei, some cells have cilia and the layer may contain mucus secreting unicellular glands
- Columns are elongated and the nuleus is towards the bottom as they are more active
describe the function of simple columnar
absorption, secretion of mucus, enzymes and other substances ciliated type propels mucus by ciliary action
- In the digestive tract cells do not have cilia but the enterocytes have another cell surface speiclisation which acts to increase the surface area of each cell, with increased luminal surface area each cell can help digestion and absorption of nutrients, electrolytes and water, these are called microvili
describe the location of simple columnar
– nonciliated type lines most of the digestive tract, gallbaldder and excretory ducts of some glands, ciliated variety lines small bronchi, uterine tubes and some regions of the uterus
describe pseudo stratified columnar
single layer of cells of differing heights, nuclei are seen at differnet levels and may contain mucus secreting cells and cilia
describe the function of pseudo stratified columnar
– secretion, particularly of mucus, propulsion of mucus by ciliary action
describe the location of pseudo stratified columnar
nonciliated type in males sperm carrying ducts and ducts of large glands, ciliated variety lines the trachea and most of the upper respiratory tract
describe an example of pseudo stratified columnar
- For example globet cells, that are ciliated and unicellular mucous glands, help us get rid of pathogens
describe stratified lining epithelium
- Stratified squamous – flattened at surface
- Stratified cuboidal – top layer is cubodial
- Stratified columnar – top layer is columnar
- Trasitional (urothelium – stretches so cells at surface go from cubodial to flattened) – only found in the urine tract as it allows it to extend, unfolds and flattens out
describe stratified squamous epithelium
thick membrane composed of serveral layers, they are either cubodial or columnar and metabolically active, surface cells are flattened, in the keratinised 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 - Cells on the surface are flattened, they retain the nuclei
- K is where the skin is, there is dead cells present bound to one another with keratin protecting from water loss
describe the function of the squamous epithelium
protects underlying tissues in areas subjected to abrasion
describe the location of the squamous epithelium
nonkeratinized type forms the moist linings of the esophagus mouth and vagin, keratinized variety forms the epidermis of the skin, a dry membrane
where are the stratified cuboidal epithelium found
- 2 layers of cells
- Found in the lining ducts of the larger glands e.g. mammary gland and sweat gland
where is the stratified columnar tissue found
- More rare
- Found in lining in large glandular ducts and small amounts in the male urethra and pharynx
describe transitional epithelium
- Relaxed, lots of differnet cells, they fold in the membrane as they relax
- basal cells cubodial or columnar, surface cells are dome shaped or squamous like depending on degree of organ stretch
describe function of transitional epithelium
streches readily and permits distension of urinary organ by contained urine
describe the location of transitional epithelium
lines the urters, urinary bladder and part of the urethra
what is transitional epithelium also called
Also called urothelium because its only found in the urinary tract goes from cubodial shape to a squamous shape
how is transitional epithelium specialised
Specialised in two ways
- The epithelium is essential impermeable to salts and water, it is a strong barrier against most substance in urine
- Luminal surface of transitional epithelium have membrane thickenings called plaques present this allowes stretching or distension, can fold into the cell when not distended and this gives their dome apperance
what are the two types of glandular epithelium
- exocrine glands - secrete onto surface and possess ducts- endocrine glands -secretions diffuse into the bloodstream ‘ductless” – the endocrine glands secrete through the basement membrane into the blood therefore they do not need ducts as they are going through the tissues
what are the types of exocrine glands
- Single (single duct)
- Compound (branched duct)
Unicellular – goblet cells
Tubular – uterus, alimentary tract, sweat glands
Acinar (alveolar)-breast – ball of cells
Tubuloacinar – pancreas, salivary glands
what is a mucosa
- A moist lining epithelium of a body cavity and its underlying supporting conncitve itssue (lamina propria)
- Moistend by mucus produced by the epithelium or adjacent glands
- +/- msucle layer (muscularis mucosae)
what types of tissue does the mucosa (mucus membrane) involve
- Epithelium
- Conenective tissue (the lamina propria)
- A layer of smooth muscle (muscularis mucosa)
- Covered with a coating of mucus
draw the mucosa
draw it
what types of tissue are in the serosa
- Epithelium (simple squamous type called mesothelium)
- Connective tissue
what is a serosa
- A moist simple squamous epithelium (mesotheium) lining a closed body cavity, together with its underlying connective tissue
what is the serosa moistened by
- Moistened by water seorus fluid that passes across the epithelium
where is the serosa present
- Only in body cavities
- Present in pleural cavity, pericardio caity and have a mesothelium and lining in the inside of the sack
what kind of connective tissue surrounds the serosa
- Areolar is loose connective tissue, it brings blood vessels to the epithelia above it and allows for diffusion to happen
- denser tissue is present in the tendons and ligaments
what are the two types of dye used in tissue staining
- Most are stained with haemotoxylin which is blue and eosin which is red, they are often called H&E,
- Haemotoxlyin is a basic dye that stains nucleic aicds blue so nuclei are blue
- Esoin is a red acid dye and stains other tissue components red
define epithelial tissue
- Forms boundaries between differnet environments, protects, secretes, absorbs, filters, makes up the skin surface and lining of the gi tract organ and other hollow organs
how do you classify epithelium
- Think about function
- When looking at epithelium, you have to think about function, the air spaes of the lungs are lined by a single layer of flattend epithelial cell that allow oxygen to travel across them into surrounding vessels if you have more than one layer this would be difficult, this is simple epithelium
- But the outside of the body needs to be tough so it is lined by many layers forming the epidermis of the skin this is stratified epithelium - Think about shape
- Squamous – flatteend and nuclei flat cells good for easy movement of substances across the cell
- Cubodial cells – round nuclei, chunky cells give structure to ducts and tubes
- Columnar cells – have elongated nuclei that sit towards the base of the cells, tend to be more metabolically active cells that secrete or absorb
how do you classify epithelial tissue due to function
- When looking at epithelium, you have to think about function, the air spaes of the lungs are lined by a single layer of flattend epithelial cell that allow oxygen to travel across them into surrounding vessels if you have more than one layer this would be difficult, this is simple epithelium
- But the outside of the body needs to be tough so it is lined by many layers forming the epidermis of the skin this is stratified epithelium
how do you classify epithelial tissue due to shape
- Squamous – flatteend and nuclei flat cells good for easy movement of substances across the cell
- Cubodial cells – round nuclei, chunky cells give structure to ducts and tubes
- Columnar cells – have elongated nuclei that sit towards the base of the cells, tend to be more metabolically active cells that secrete or absorb
describe goblet cells
- They are unicellular glands which produce glycoprotein mucin, this with water is known as mucus
- Found between other simple columnar epithelial cells in mucus membranes
- Protective and lubricating roles in the body
- Mucin does not stain well with H&E so they use speical stains that are carbohydrate rich including periodic acid schiff reaction to stain mucin
- To cope with increasingly solid faeces the colon needs abundant mucus acting as a lubricant
describe exocrine glands
simple - one duct
complex - more than one duct
describe the basement membrane
- Found underlying all epithelia
- Divide epithelai from the subjacent connective tissue and are fomred of an shapeless matrix of ground substance and fibrils of laminin, collagen types III and IV
- Formed by contributions from both the epithelium and stroma and can be stained by the periodic acid schiff method and by the silver method or speical stains for its compoenents
describe the function of the basement membrane
- Functions include supporting the epithelium, acting as a selective filter and acting as a selevtive barrier to passage of cells between epithelia and connective tissue
what is the definition of connective tissue
connective tissue provides structural, metabolic and support to tissues and other organs
describe characteristic of connective tissues
- it contains a few cells compared to the epithelium but a large amount of extracellular matrix
