(P) Lec 2: Epithelial Tissue Flashcards
Groups of cells similar in structure and intercellular substance performing a specific function
Tissue
T or F: Tissues have the same function but different morphology
False (same function and morphology)
A combination of tissues in appropriate patterns and proportions
Organs
Different organs associated with one another in variable proportions
Organ Systems
Basic Types of Tissue:
> The external or internal covering or lining of the body (e.g. skin and glands)
Epithelial
What basic type of tissue are skin and glands?
Epithelial
Basic Types of Tissue:
> The supporting/binding tissue
> Provides general structure, mechanical strength, space filling, and physical and metabolic support for more specialized tissues
Connective
What basic type of tissue are collagen, reticular fibers, and elastic tissue (the dermis)?
Connective
T or F: Connective tissue’s extracellular matrix exists in abundant amounts
True
Basic Types of Tissue:
> Made up of elongated cells specialized for contraction and movement
Muscular
What are the 3 subtypes of muscular tissue?
> Smooth
Skeletal
Cardiac
Basic Types of Tissue:
> Important for the interpretation of stimuli
> Composed of cells with long fine processes specialized to receive, generate, and transmit nerve impulses
Nervous tissue
Basic Types of Tissue:
> Cells are aggregated polyhedral
> Extracellular matrix is in small amounts
> Lines surfaces or body cavities; for glandular secretion
Epithelial
Basic Types of Tissue:
> Has several types of fixed and wandering cells
> Extracellular matrix is in abundant amounts
> Supports and protects tissues/organs
Connective
Basic Types of Tissue:
> Cells are elongated and contractile
> Extracellular matrix is in moderate amounts
> Used in strong contractions and body movements
Muscular
Basic Types of Tissue:
> Cells are elongated with extremely fine processes
> Extracellular matrix is in very small amounts
> Transmits nerve impulses
Nervous
Tissue:
→ composed of cells in close apposition with little to no intercellular substance
→ no ground matrix and intercellular fibers
→ there is strong adhesion between cells attached to a thin layer of extracellular membrane
→ cellular sheets are formed
Epithelial
The basement membrane is also called as?
Basal Lamina
This separates the epithelium from the connective tissue (is non-cellular) and nutrients for the epithelial cells must diffuse across this
Basement membrane
T or F: Epithelial tissues are vascular
False (avascular; blood vessels never cross the basement membrane)
Three Germ Layers:
> An example of this is the epidermis of the skin and epithelium of the cornea
Ectoderm
Three Germ Layers:
> An example of this is the epithelium of the kidneys and reproductive tracts of both males and females
Mesoderm
Three Germ Layers:
> An example of this is the epithelium of the GIT
Endoderm
What is the principal function of epithelial tissue?
Covering, Lining, and/or Protection
What are the functions of epithelial tissue?
Clue: FALSES
> Filtration
Absorption
Lubrication
Secretion
Excretion
Sensory Reception
T or F: Most substances that enter or exit the body must pass through the epithelial layer
False (ALL substances)
T or F: The epithelial layers can modify and change their passage mechanics to influence its normal homeostatic mechanism
True
What are the 2 types of epithelium?
Surface and Glandular
2 main types of epithelium:
> A membranous layer that covers the external and internal surfaces of the body
Surface
2 main types of epithelium:
> Refers to glands
Glandular
Nomenclature of Epithelium:
> The name for the number of cell layers
First
Nomenclature of Epithelium:
> The name for the cell shape
Second
Nomenclature of Epithelium:
> The name that is optional, only if with a special feature
Third
Surface Epithelium Subtypes:
> Lined by a single layer of cells
Simple
Specific Subtype of Epithelium:
> A single layer of flat cells (nuclei also appear flat)
> Well-adapted for exchange, filtration, and diffusion purposes
> Provides little protection against mechanical abrasion–cannot be found near surfaces subject to stresses
> e.g. parietal layer of the Bowman’s capsule (kidney), endothelium of blood vessels, mesothelium of body cavities, corneal endothelium, and lung alveoli
Simple Squamous
Specific Subtype of Epithelium:
> A single layer of square cells
> Nuclei appear circular and centrally located
> The epithelium have the same height and width as the connective tissue
> e.g. PCT and DCT of the kidneys, sweat glands, sebaceous glands, and the small excretory salivary and pancreatic glands
Simple Cuboidal
Specific Subtype of Epithelium:
> Single layer of tall cells
> Nuclei appear elongated and are near the basement membrane
> are taller in relation to cuboidal cells perpendicular to the basement membrane
> Found on absorptive (small intestines) and secretory (stomach) surfaces
Simple Columnar
Surface Epithelium Subtypes:
> Lined by several layers of cells; well-adapted for protective and barrier purposes
> Are poorly suited for absorption and secretion purposes due to its thickness but some are moderately permeable to water and other small molecules (e.g. skin epidermis protects the tissue from water loss)
Stratified
Specific Subtype of Epithelium:
> The most common type; are the matured cells that came from the cuboidal basal layer of the epidermis
Stratified Squamous
What are the 2 types of Stratified Squamous Epithelium?
- Cornified/keratinized
- Non-cornified/non-keratinized
This type of stratified squamous epithelia slough off and prevents skin dehydration
Cornified/keratinized
This type of stratified squamous epithelia lines the body cavities where water loss is not a problem (e.g. mouth, esophagus, vagina, larynx, and anal canal)
Non-cornified/non-keratinized
Specific Subtype of Epithelium:
> Found in the lining of larger excretory ducts of exocrine glands (salivary and sweat)
> Composed of 2 or 3 layers
Stratified Cuboidal
Specific Subtype of Epithelium:
> Are very rare in nature
> Found in the conjunctiva of the eyelids where they act as protection and secrete mucus
Stratified Columnar
Surface Epithelium Subtypes:
> A modification of stratified epithelium
> Contains cells that are flattened and cuboidal
> e.g. uroepithelium (excretory passages of the urinary tract)
> Usually has 4-5 layers when empty but can appear to have only 2-3 when distended
Transitional
T or F: An empty bladder will have squamous transitional cells while a full bladder will have cuboidal transitional cells
False (reverse)
Surface Epithelium Subtypes:
> A modification of simple epithelium
> All cells are in contact with the basal lamina but not all of them reach the apical surface; it sometimes causes the nuclei to be compressed upwards or downwards
> Means false stratification
> e.g. respiratory epithelium (majority contains goblet cells–mucus secreting cells)
Pseudostratified
What is the specific subtype of blood vessels?
Simple squamous
What is the specific subtype of the epidermis?
Stratified squamous
What is the specific subtype of the salivary glands?
Stratified Cuboidal
What is the specific subtype of the conjunctiva?
Stratified Columnar
What is the subtype of the bladder?
Transitional
What is the subtype of respiratory epithelium?
Pseudostratified
Refers to the transformation of one tissue type to another (e.g. stratified squamous may replace other tissues in areas of chronic irritation)
Metaplasia
Refers to incomplete development of tissue
Hypoplasia
Refers to increased number of tissue cells
Hyperplasia
Refers to the formation of new tissue (e.g. tumors)
Neoplasia
Refers to the abnormal uncontrolled growth of epithelial cells; arises from surface epithelia (malignant neoplasm)
Carcinoma
What specific subtype is the most likely to undergo malignant metaplasia producing squamous cell carcinoma?
Stratified squamous (e.g. when large moles are found on the epidermis)
Apical Cell Surface Modification:
→ tightly packed projections of intestinal absorptive cells
→ minute finger-like projections of the plasma membrane
→ gives a striated/brush-border appearance
→ increases the cell’s surface area
→ highly specific for cells with absorptive function
Microvilli
Apical Cell Surface Modification:
→ actively motile processes that propel substances along the surface
→ found in respiratory epithelium
→ larger than microvilli and contains microtubules
Cilia
Apical Cell Surface Modification:
→ long microvilli found in the epididymis and vas deferens of the male reproductive tract
→ are longer and non-motile compared to cilia
→ also increases cell surface area and facilitates absorption
→ specialized versions of these with motion detecting functions are found in the inner ear sensory cells
Stereocilia
Apical Cell Surface Modification:
→ modified columnar epithelial cells
→ synthesizes and secretes mucus
→ scattered amongst many simple epithelial linings
→ found in the respiratory and the GI tract
→ usually don’t take up stains as they contain mucus
Goblet Cells
Type of Epithelium:
→ they secrete hormones and are derived from epithelium
→ cells may or may not maintain a connection with the surface epithelium; the connection is maintained to form a duct in exocrine or lost in endocrine
→ are cells specialized in producing a secretion that differs from blood or intercellular fluid
→ may synthesize, store, and secrete: proteins (pancreas), lipids (adrenal and sebaceous), and complexes of carbohydrates and proteins (salivary glands)
Glandular Epithelium
Glandular Classifications acc. to Number of Cells:
> A single secreting cell (e.g. goblet cells)
Unicellular Gland
Glandular Classifications acc. to Number of Cells:
> Has an epithelium-derived duct and secretory units
Multicellular Gland
Glandular Classifications acc. to Secretion:
> Thin and watery (e.g. sweat and parotid glands)
> Can be basophilic or acidophilic
Serous
Glandular Classifications acc. to Secretion:
> Thick and vicious (e.g. sebaceous and esophageal glands)
> Contains heavily glycosylated proteins known as mucosin–usually don’t take up much stain
Mucous
Glandular Classifications acc. to Secretion:
> Both watery and viscous; mucous-serous gland (e.g. tracheal, sublingual, submaxillary, and submandibular glands)
> Called as the Demilunes of Giannuzzi or serous demilunes
Mixed
Glandular Classifications acc. to Secretion:
> Secretes living cells found in the ovary and testes
Cytogenetic
Glandular Classifications acc. to Manner of Secretion:
> Releases products into a system of ducts (e.g. sweat, gastric, and salivary glands)
Exocrine
Glandular Classifications acc. to Manner of Secretion:
> Releases products into the blood or lymph with no ducts (e.g. pituitary, adrenal gland, and islets of Langerhans–aka hormone producing cells)
Endocrine
Glandular Classifications acc. to Manner of Secretion:
> Releases products into the extracellular spaces for simple diffusion to target cells in the immediate vicinity (e.g. Merkel’s cells)–aka paraneurons
Paracrine
Glandular Classifications acc. to Manner of Secretion:
> Secretions are not discharged from the cells producing it (e.g. phagocytes and granular leukocytes)
Accrine
Glandular Classifications acc. to Fate of Secretion:
> No destruction (most exocrine glands) as the cell remains intact
> Secretes proteins via exocytosis through the apical surface of excretory cells (e.g. sweat and salivary glands)
Merocrine
Glandular Classifications acc. to Fate of Secretion:
> Partial destruction; loss of membrane-enclosed cytoplasm containing one or more lipid droplets (e.g. mammary glands)
> There is a loss of some parts during secretion
Apocrine
Glandular Classifications acc. to Fate of Secretion:
> Total destruction (death) which leads to gland fragmentation
> The whole cell is released into excretory ducts
> e.g. sebaceous glands–pimples
Holocrine
Glandular Classifications acc. to Morphology:
> Ducts do not branch
Simple
Glandular Classifications acc. to Morphology:
> Simple epithelium-lined tubules that open to the surface and run in a straight course (e.g. intestinal glands)
Simple Tubular
Glandular Classifications acc. to Morphology:
> A deeper portion of the tube is convoluted (e.g. sweat glands)
Simple Coiled Tubular
Glandular Classifications acc. to Morphology:
> A deeper portion divides into branches lined with secreting cells which open into superficial portions as ducts (e.g. uterine glands)
Simple Branched Tubular
Glandular Classifications acc. to Morphology:
> Does not occur in man
> The simplest form containing a single sac with a dilated lumen and connected to the surface by a constricted portion
Simple Acinar/Alveolar
Glandular Classifications acc. to Morphology:
> Simple alveolar gland made up of numerous sac-like structures or out-pocketings
Simple Branched Acinar/Alveolar
Glandular Classifications acc. to Morphology:
> Ducts from several secretory units converge into larger ducts
Compound
Glandular Classifications acc. to Morphology:
> Terminal portions of the smallest tubules are more or less coiled; usually branching
> e.g. pure mucous or oral cavity glands, cardiac glands of stomach, Brunner’s glands, bulbourethral glands, and renal tubules
Compound Tubular
Glandular Classifications acc. to Morphology:
> Has structures that divide into branches with sac-like dilations or out-pocketings
> e.g. large salivary, pancreatic, esophageal, respiratory, and mammary glands
Compound Tubulo-Acinar/Alveolar
Glandular Classifications acc. to Morphology:
> Have sac-like structures that branch and divide into numerous dilated segments (e.g. portions of the mammary gland)
Compound Acinar/Alveolar
T or F: Glands cannot undergo neoplastic changes
False
Refers to benign epithelial growth with glandular morphology
Adenoma
Refers to malignant growth that arises from glands
Adenocarcinoma
Intercellular Junctions:
→ occluding junction (zonula occludens)
→ located beneath the apical surface; are the sealing strands
→ forms a collar around each cell beneath the apical surface which blocks the passage of luminal contents between cells and lateral movements of plasma membrane proteins and lipids in the plane of the membrane between the apical and basolateral plasma membrane
Tight Junctions
Intercellular Junctions:
→ provide anchorage points for cytoskeletal elements
→ links the cytoskeletons of individual cells to form a strong transcellular network
Adherens Junctions
Another name of adhesion belt
Zonula adherens
These link adjacent cells (cell to cell connection)
Desmosomes
These link epithelial cells to the basal membrane
Hemidesmosomes
Intercellular Junctions:
→ contains proteins known as connexons which allows the passage of inorganic ions and other small molecules
→ important in the control of growth, development, cell recognition, and differentiation
→ provides the means of electrical coupling of visceral and cardiac muscle cells which permit synchronous contraction
→ made up of spaces usually adjacent to the plasma membrane
Gap Junctions
