Epithelium Classification Flashcards
Simple squamous epithelium are found where?
- Lining of Vascular System
- Lining of Body Cavities
- Kidney (Bowman’s Capsule)
- Lung (Respiratory Spaces)
Simple squamous epithelium function as?
- A barrier
- Diffusion O2 CO2 due to their thinness
Specialized simple squamous epithelium that line the inside of blood vessels and the heart?
Endothelium (prevent coagulation of blood)
Specialized simple squamous epithelium that line body cavities such as pericardial, peritoneal, and plural cavities?
Mesothelium
Malignant tumors that derive from the mesothelium?
Plural Mesothelioma
What are the features of simple cuboidal epithelial cells?
Cell height=Cell Width
Single Layer
Round Nuclei
What are the features of simple squamous epithelial cells?
Flattened cells, scale like, flattened nuclei
Where are simple cuboidal epithelium found?
- Kidney Tubules
- Ducts/Glands
Simple cuboidal epithelium function?
Barrier
Absorption
Secretion
What are the features of simple columnar epithelium?
Tall Columnar
Oval-Shaped Nuclei
Surface Modifications: Microvilli, Cilia
Where are simple columnar epithelium found?
- GI Tract and Gallbladder
- Non-Ciliated Type
- Oviduct
- Ciliated Type
What are the functions of simple columnar epithelium?
Absorption
Secretion
Lubrication
Transport
What are the features of pseudostratified columnar epithelium?
Columnar Cells and Basal Cells
Oval-Shaped Nuclei
Ciliated: Trachea, Bronchi
Non-Ciliated: Epidymis, Prostate
Where are ciliated pseudostratified columnar epithelium found?
Trachea and Bronchi
What function do ciliated pseudostratified columnar epithilial cells carry out?
Protection
Movement of Mucus
Where are non-ciliated pseudostratified columnare epithelium found?
Epididymis
What is the function of non-ciliated pseudostratified columnare epithelium?
Absorption
What are the features of stratified squamous epithelium?
Top layer is flat
Multiple cell layers
Keratinized stratified squamous epithelium are found wear?
Skin (Epidermis)
Non-keratinized stratified squamous epithelium are found where?
Oral Cavity
Esophagus
Vagina
What are the functions of both keratinized and non-keratinized stratified squamous epithelium?
Barrier
Protection
What are the features of stratified cuboidal epithelia?
Cube Shaped Basal Layer
Round Nuclei
Apical Layer: Cuboidal
What are the features of stratified columnar epithelia?
Cube-Shaped Basal Layer
Round Nuclei
Apical Layer: Columnar
Where are stratified cuboidal epithelium found?
Sweat Gland Ducts
Exocrine Glands
What is the function of stratified cuboidal epithelium?
Barrier
Conduit
Where are stratified columnar epithelium found?
Large ducts of glands (ie. Parotid Salivary Glands)
What is the function of stratified columnar epithelium?
Barrier
Conduit
What are the features of transitional epithelium?
Multiple Layers
Variable Cell Shape
Surface Layer of dome cells that are often binucleated
Ability to Stretch
Where are transitional epithelium found?
Urinary System: Ureter, Bladder, Kidney
What is the function of translational epithelium?
Protection
Barrier
Apical Domain
- Forms external/luminal surface of the cell
- Exhibit various modifications
- Microvilli (Can’t see in lab)
- Increase surface area (absorption)
- Small Intestine, Kidney
- Size - 1 x 0.01 micrometer
- Core is formed by actin filaments bound together by fimbrin and fascin anchored into the membrane by lateral anchoring proteins such as myosin I
- Amorphous apex formed by villin by which the actin filaments anchor into
- Increase surface area (absorption)
- Stereocilia
- Uncommon modified microvilli
- Long and sometimes branching
- Core formed by actin filaments similar to microvilli
- Found in the epididymis (absorption) and inner ear cochlea (sensory receptors)
- Cilia
- Move substances along the surface of the epithelium
- Respiratory tract and oviduct
- Formed by 10 pairs of microtubule (axoneme)
- 9 doublets and 1 central pair
- Thicker than microvilli 2-10 x 0.25 micrometers
- Base is attached to centriole/basal body
- 9 triplets
- Base is attached to centriole/basal body
- Primary ciliary dyskinesia
- Dextrocardia
- Impaired development of skull air sinuses
- No mucus removal from lunds ->infection
- Infertility
- Move substances along the surface of the epithelium
- Secretory Vesicles
- Present in epithelium involved in production and secretion of macromolecules
- Microvilli (Can’t see in lab)
Lateral Domain
- Cell junctions - allows functioning as a whole
- Occluding Junctions (Tight)
- Apically oriented
- Zonula occludens
- Virtually impermeable, functions to prevent diffusion by blocking paracellular pathways (4 nm)
- Formed by sealing strands of transmembrane proteins
- Found in cells with secretory or absoptive roles
- Anchoring Junctions
- Provide stability and mechanical strength by connecting adjacent cytoskeletons
- Two major types
- Zonula Adherins
- Connect actin to actin and not as tight at occluding junctions (20 nm)
- Composed of:
- Actin binding proteins
- Vinculin, alpha-actinin
- Peripheral protein
- Cadherin family (Ca2+ dependent)
- Plays important role in control of cell behavior
- Cadherin family (Ca2+ dependent)
- Actin binding proteins
- Macula adherins (desmosome)
- Connects intermediate filaments
- Epidermis of skin and muscle
- Composed of:
- Intracellular plaque
- Made of desmoplakin
- Intermediate filaments go throught the plaque
- Transmembrane Proteins
- Cadherin family
- Intracellular plaque
- Pemphigus disease
- body produces abnormal antibodies to the proteins forming desmosomes
- Presents as blistering of skin and mucous membranes
- Zonula Adherins
- Communicating Junctions (Gap Junctions)
- Allow diffusion of small molecules and ions b/t adjacent cells
- Intercellular channels (2.8 nm in diameter)
- Formed by a pair of connexons
- Each consists of 6 connexins
- Formed by a pair of connexons
- Usually occur in patches
- Most common in epithelia, cardiac, smooth musclem, and embryonic tissues
- Communication and cell proliferation
- Occluding Junctions (Tight)
Basal domain
- Basement membrane
- Separates epithelium from underlying connective tissue
- 2 Layers
- Basal Lamina
- Most external layer that belongs to the epithelium
- Mostly composed of sheets of collagen type IV and laminin
- Reticular lamina
- Deeper layer that belongs to the connective tissue
- Mostly composed of thin collagen fibers (Type III)
- Basal Lamina
- Epithelial cells attach via anchoring junctions
- Focal Adhesions
- Attach actin cytoskeleton of cell to extracellular matrix
- Composed of
- Actin-binding proteins
- Vinculin, alpha-actinin attach to microfiliaments
- Peripheral protein
- Talin
- Connects actin binding proteins to transmembrane proteins
- Talin
- Transmembrane proteins
- Integrin (Ca2+ dependent)
- Actin-binding proteins
- Hemidesmosomes
- Attach intermediate filaments from cell cytoskeleton to extracellular matrix
- Composed of:
- Intracellular plaque (made of desmoplakin)
- Intermediate filaments end on plaque
- Transmembrane proteins
- Integrin family - attach to extracellular proteins
- Intracellular plaque (made of desmoplakin)
- Focal Adhesions
Differentiate between exocrine and endocrine glands.
- Endocrine glands
- Secrete their product into the intercellular space or underlying tissue which then diffuse into the blood
- Cells usually arranged in cords along capillaries that supply the gland
- Exocrine glands
- Secrete their product into ducts or spaces lined with epithelium
- Cells usually arranged in acini or tubules
What are the major mechanism of secretion for exocrine glands?
- Merocrine
- Apocrine
- Holocrine
Describe merocrine glands.
- Secretory product is delivered in membrane bound vesicles to the apical surface
- Fuse with membrane and release via exocytosis
- Three subtypes
- Serous glands
- Secrete thin, watery, protein rich secretion
- Vesicles small and densely stained
- Better developed RER than mucous cells
- Cell cytoplasm stains more basophilic
- RER occupies basal part of cell forcing nuclei to middle of the cell
- Cells are usually pyramidal in shape
- Serous acini rounded in shape
- Example: pancreas and parotid salivary gland
- Mucous glands
- Produce mucins that consist of long chains of negatively charged carbohydrates attached to a small protein core
- Mucins are viscous and important to lubrication and protection
- Secretory granules are large and stain very lightly w/ H&E
- RER not well developed
- Nuclei are heterochromatic and occupy the basal position
- Cells columnar in shape
- Mucous acini have a tubular shape
- Example: Goblet cells, glands of soft palate, Brunner’s glands
- Produce mucins that consist of long chains of negatively charged carbohydrates attached to a small protein core
- Mixed glands (Seromucous glands)
- Have both serous and mucous glands
- Mucous cells form tubules capped by serous cells that form serous demilunes
- Example: Submandibular salivary gland
- Have both serous and mucous glands
- Serous glands
Describe apocrine glands.
- Secretion of product involves pinching of the apical cytoplasm w/ the formation of secretory vesicles
- Found in mammary gland where it is responsible for releasing large lipid droplets into milk
Describe holocrine glands.
- Secretion involves whole cell rather than its parts
- Cells accumulate secretory product and goes through apoptosis resulting in both the cellular content and cell debris to be released into the lumen of the gland
- Typical of sebaceous glands of the skin
Describe unicellular glands.
- Individual secretroy cells scattered within non-secretory epithelium
- Goblet cells are the most common
- Specialized for the secretion of mucus
- Scattered within the columnar epithelia of the GI and respiratory tracts
- Goblet cells are the most common
Describe multicellular exocrine glands.
- Composed of more than one cell
- Most form tubular invaginations from the surface
- Allows increase in surface area
- Terminal part = secretory portion
- Serves as a duct
- Connects secretory cells to the surface
- If shaped like a flask = alveolar or acinar
- Most often serous
- If shaped like a tube = tubular
- Most often mucous
- If secretory tube ends with a flask-shaped dilation = tubuloalveolar
- Always mixed/seromuscous
- Serves as a duct
Describe myoepithelial cells.
- Are contractile cells present in some glands between the basal lamina and in the secretory portion of glands and ducts
- Contain contractile proteins (myosin)
- Contraction causes expulsion of secretory product
- Present in sweat glands, salivary glands, and in the mammary gland
Cancer derived from barrier epithelium
Carcinoma
Cancer derived from glandular epithelium
Adenocarcinoma
