Epithelial Tissue (Lectures 4 and 5) Flashcards
What are the specialised cell junctions?
Cells are closely apposed and adhere to one another by means of specific cell adhesion molecules (CAMs).
Specialised cell junctions:
OCCLUDING JUNCTIONS - Link forming an impermeable barrier, tight junction.
ANCHORING JUNCTIONS - Provide mechanical stability by linking of the cytoskeleton of one cell to the cytoskeleton of adjacent cell.
- Zonula adherens (focal contacts) - actin filaments
- Macula adherens/desmosome (hemidesmosome) - intermediate filaments
COMMUNICATING JUNCTIONS - Gap junctions – allow selective diffusion of molecules between adjacent cells. (Cell to extracellular matric junctions).
Explain cell polarity.
Free surface or apical domain:
Special structural surface modifications
Microvilli:
- Cytoplasmic processes (core consisting of actin filaments).
- Closed packed microvilli = brush border (absorptive epithelium).
Stereocilia:
- Long immotile microvilli (hair cells of the inner ear, epithelium of the ductus epididymidis and ductus deferens).
Cilia:
- Motile cytoplasmic processes (consisting of microtubule axoneme, basal bodies).
- Epithelium of respiratory ways, and uterine tube.
Lateral domain:
- In close contact with the opposed lateral domains of neighboring cells.
- Presence of unique proteins, cell adhesion molecules (CAMs).
- Specialized cell-to-cell junctions (occluding, anchoring, communicating).
- Folding - invagination and evagination (interdigitation) of lateral cell membrane.
Basal domain:
- Attached to the basement membrane, cell-to-extracellular matrix junctions (focal contacts, hemidesmosomes), basal cell membrane infoldings (ion – transporting cells: striated ducts of salivary glands, kidney tubules).
How can epithelium be classified according to the arrangement of cells?
PLANAR = cells form tightly cohesive sheets traditional nomenclature is based on:
- Cell shape –> squamous, cuboidal, columnar
- Number of layers –> simple, stratified, pseudostratified
TRABECULAR = cells are arranged in cords or plates (liver, endocrine glands).
RETICULAR = cells form three-dimensional network (stroma of thymus, epithelium of crypts in tonsils, stellate reticulum of enamel organ).
Classification of epithelium according to functional specialization.
- Covering epithelium
- Simple squamous, cuboidal, columnar, pseudostratified columnar
- Stratified squamous, columnar
- Transitional epithelium (urothelium)
- Secretory epithelium
- Exocrine and endocrine
- Polarisatin of cells
- Mechanism of secretion: merocrine, apocrine, holocrine
- Absorptive epithelium
- Respiratory epithelium
- Exchange of respiratory gases, in the lung alvioli
- Sensory epithelium
- Cells react on the external stimuli by change of membrane potential.
- Primary and secondary sensory cells.
- Myoepithelium
- Cells with ability to contract
- Germinal epithelium
- Production of cells (seminiferous epithelium of testis produce spermatozoa).
- Ion-transporting epithelium
- Modificaiton of the basal cell surface
What is this slide?
LIVER
Trabecular epithelium
What is this slide?
Suprarenal gland
Trabecular epithelium
What is this slide?
Simple squanous epithelium
Mesothelium
What is this slide?
Simple cuboidal epithelium
Thyroid gland
What is this slide?
Basement membrane (kidney, PAS reaction).
What is this slide?
Simple squamous epithelium (kidney, HE)
What is this slide?
Simple cuboidal epitheloim (Heidenhain H)
What is this slide?
Simple columnar mucus secreting epitheloim (alcian blue, nuclear red).
What is this slide?
Small intestine
Villi
Simple columnar epithelium
PAS reaction
What is this slide?
Pseudostratified columnar ciliated epithelium (trachea, green trichrome)
Type of epithelium in which all cells lie on the basal lamina, but only columnar cells reach lumen.
What is this slide?
Stratified columnar epithelium
Duct of a sweat gland
What is this slide?
Parotid gland
H and E
What is this slide?
Oesophagus
HE
What is this slide?
Pseudostratified ciliated epithelium
Trachea
Explain transitional epithelium
- Lines urinary passages, is a special form of the covering epithelium.
- According of arrangement of cells - psudostratified epithelium.
- Is impermeable for salts and water, is able to adapt to the distension of organ.
- Adaptability of epithelium to distension is enabled by a unique structure of luminal cell membrane that exhibits modified areas – plaques.
- Plaques appear to be more rigid and thicker (12 nm) and actin filaments are attached to the inner surface of plaques.
- In the undistended epithelium plaques infold inward the cytoplasm and appear as fusiform vesicles – their lumina, however, are in continuity with the cell surface.
- As organ distends, the fusiform vesicles unfold and become part of the surfaceas the cell streches and flattens.
What is this slide?
Transitional epithelium
Non distended state - urinary blasser
AZAN
What is this slide?
Urinary bladder
HE
What is this slide?
Respiratory epithelium (lung)
What is this slide?
Respiratory epithelium
What is this slide?
Respiratory epithelium
Explain the structure and function of sensory epithelium.
- Sensory epithelium consists of sensory cells and supporting cells.
- Sensory cells are receptors, convert external stimuli into electric impulses.
Classification according stimulus:
Photoreceptors = rods and cones of the retina Chemoreceptors = olfactory cells (smell, olfaction) and taste cells Mechanoreceptors = hair cells of the inner ear (auditory/sound perception and vestibular/balance systems)
Classification according structure:
Primary sensory cells –> have axon; rods, cones, and olfactory cells Secondary sensory cells –> have no axon; hair and taste sensory cells
SENSORY ORGANS
- Taste buds
- Olfactory epithelium
- Eye (retina)
- Inner ear –> Corti organ and vestibular apparatus (maculae staticae and cristae ampullares)
What is this?
Olfactory epithelium
Olfactory cells
Explain rods and cones.
Rod:
- Thin elongated cell
- Photoreceptor
- Part has red shape
- Rods are more sensitive to light
- Prgment rhodopsin (visual purple)
- 120 million rods
Cones:
- Photoreceptor part has cone shape.
- Each cone is specialised to respond to one of three colours - red, green or blue.
- Pigment = iodopsins.
- Contrary to rod the interior of cone discs is continuous with the extra cellular space.
- Outer limiting membrane (red lining is formed by a row of zonulae adherentes (ZA) between Muller’s cells and photoreceptors.
OS = Outer segment –> Has cylindrical shape, contains horizontally flattened membrane discs.
C = Connecting stalk with cilium.
BB = Basal body of cilium.
IS = Inner segment (metabolic region), contains protein synthesis organelles (Golgi complex, rER, free ribosomes, mitochondria).
OF = Outer fibre
N = Cell body with nucleus
IF = Inner fibre - axon
P = Presynaptic part (synapse with bipolar neurons).
Describe sensory epithelium
- Sensory epithelium of the inner ear consists of sensory hair cells and supporting cells.
- Hair cells are mechanoreceptors.
- Apical surface carries highly organised system of steriocilia and one kindocilium.
- Steriocilia are rigid structures and have mechanial-gated ion channels on their tops.
- Flection of stereocilia to kinocilium causes excitation (depolarisation of the plasma membrane).
Describe myoepithelium
Myoepithelium is a contractile epithelium which contains actin and myosin myofilaments.
Surround the glandular epithelial cells in the salivary glands, eccrine and apocrine glands in the skin, mammary gland, dilator pupillae muscle.
What is this slide?
Seminiferous tubule
What are the two types of glandular epithelium?
Exocrine
Endocrine
What is this slide?
Goblet cells
Large intestine
PAS reaction
What is this slide?
Goblet cells
Large intestive
Alcian blue
Nucear red
Describe serous cells
Serous cells (serous acini, serous demiluni):
- Protein secreting cell (secretion = enzymes, water ions)
- Basl cytoplasm - basophilic, RER, motochondria
- Golgi complex in supranuclear location
- Apical cytoplasm - secretory granules (usually basophilic)
Describe mucous cells
Mucous cell (mucous tubules):
- Low columnar cell
- Flattened condensed nucleus
- Cytoplasm is fulled with mucinogeous granules
- Mucus/mucin-producing cell
- Staining - PAS reaction, alcian blue
What are the different kinds of ducts?
What is this slide?
Submandibular gland (HE)
A = serous acinus
T = mucous tubule
E = striated duct lined with a simple columnar, ion transporting epithelium
O = eosinophilic basal striation
What is this slide?
Parotid duct
What is this slide?
Submandibular gland
What is this slide?
Sublingual gland
What is this slide?
Parotid gland
What is this slide?
Striated duct
What is this slide?
Interlobular ducts
What is this slide?
Interlobular duct
Describe this scheme of an endocrine cell
Polarity of the secretory epithelium
A cell (glucagon producing) of Langerhans islet of the pancreas.
N = nucleus
Nu = nucleolus
M = mitochondria
S = secretory granules
BL = basal lamina
rER = Rough endoplasmic reticulum
P = plasma membrane
Cap = blood capillary
Arrow = exocytosis of glucagon into bloodstream
What is this slide?
Pancreas
What is this slide?
Islets of Langerhans
What are the types of secretion?
What is this slide?
Sebacious gland
What is this slide?
Sebacious gland
What is this slide?
Sebacious gland
What is this slide?
Merocrine sweat gland
What is this slide?
Merocrine sweat gland
What is this slide?
Merocrine sweat gland
What is this slide?
Apocrine gland - skin
What is this slide?
Apocrine gland - skin
