Epithelia, CT & Integument Flashcards
(40 cards)
What are the 2 types of Epithelium?
- Surface Epithelium (Epithelium, Endothelium, Mesothelium)
2. Glandular Epithelium
What are the general functions of Epithelium?
- Protection (e.g. skin) / barrier (e.g. bladder)
- Absorption (e.g. intestine)/ secretion (e.g. glands)
- Excretion (e.g. kidney)
What is Mesothelium?
A membrane composed of simple squamous cells that covers organs & body cavities (e.g. pleura, pericardium, peritoneum)
What is Endothelium?
Type of epithelium that lines the interior surface of blood vessels and lymphatic vessel. It is a thin layer of simple squamous cells called endothelial cells.
What is the basement membrane composed of?
Thin layer (50-100nm) of acellular material between epithelial cells and underlying CT
- Proteoglycans
- Adhesive molecules
- Fine collagen fibres
What is the function of the basement membrane?
Adhesion, allows stretch, filtration barrier & diffusion medium for waste and nutrients.
Features of simple squamous epithelium? and an example where it can be found?
- Flat/scale-like cells
- Every cell attached to BM
- e.g. Bowman’s capsule (kidney), blood vessels
Features of simple cuboidal epithelium? Where is it found?
- Cells appear square in section
- e.g. Line small ducts, kidney tubules, thyroid follicles
Features of simple columnar epithelium? Where is it found?
- Tall rectangles
- Often has a role in secretion
- e.g. Lines larger ducts, lines stomach and intestine, gall bladder
Features of stratified squamous epithelium?
- Only cells at base have connection to basement membrane
- At the bottom can appear cuboidal
- Can be keratinised/non-keratinised
- e.g.non-keratinised = lines oesophagus, vagina and oral cavity
- e.g. keratinised = skin
Features of stratified cuboidal epithelium?
- Usually 2 layers (can detect round nuclei)
- Cuboidal epithelia throughout layer
- e.g. sweat gland ducts, large exocrine ducts
Features of stratified columnar epithelium?
- Only cells near the lumen become columnar
- largest exocrine ducts
Features of Pseudostratified epithelium?
Pseudostratified (1 layer)
- Single layer but some cells do not reach the surface
- Nuclei at different heights therefore look layered but are not
- RESPIRATORY EPITHELIUM
What is transitional epithelium?
A type of tissue consisting of multiple layers of epithelial cells which can contract and expand.
It is so named because of this function in the transition of degree of distension.
What are the two broad classifications of Glands?
- Unicellular
- Multicellular (Intraepithelial vs Extraepithelial)
What is a unicellular gland?
Single secretory cell.
Function: Produces mucus
e.g. Goblet cells
Location: airway, intestine
Features of multicellular Intraepithelial glands?
- UNCOMMON
- Small number of secretory cells within the surface epithelium
e. g. glands found in trachea of chicken
Features of multicellular extraepithelial exocrine (MCE) glands?
- A secretory unit is used to denote a group of cells that secrete the product of the gland
- End piece shapes (adenomeres)
(tubular, acinar, alveolar) - Can be simple or complex
What is the difference between endocrine and exocrine glands?
Endocrine has no ducts.
Exocrine secretory unit transported by ducts.
What is a subclassification of multicellular extraepithelial glands?
- Endocrine (no ducts)
- Exocrine (ducts- simple vs complex)
What are features of complex exocrine glands?
- Larger, more complex organisation reflected in duct system
- Have organised supporting tissue (e.g. connective tissue forms capsule/ sheets (septa) and strands (traberculae) from capsule penetrate the parenchyma and divide it into lobes.
Explain Merocrine secretion.
Merocrine
- only secretory substance lost
- exocytosis from secretory cells into an epithelial-walled duct or ducts and thence onto a bodily surface or into the lumen.
Explain Apocrine secretion.
Apocrine
- Secretory substance and some plasma membrane lost
- Bud their secretions off through the plasma membrane producing membrane-bound vesicles in the lumen.
Explain Holocrine secretion.
Holocrine
- Entire cell and its contents (secretory substance) lost
- Secretions in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen.
