Exam 1 Microanatomy Thread Flashcards
Phase Contrast
Microscopy
Small differences in refractive index ⇒ difference in contast.
Darkfield Microscopy
Specimen illuminated at an angle.
Curved surfaces scatter light.
Increases contrast of small objects in unstained specimen.
Polarizing Microscopy
Only rotated light visible.
Useful for visualizing structures that are arranged in a cystalline or paracrystallin array.
Confocal Microscopy
Opectical section of unsectioned specimen.
Laser excits cells in thin plan.
Out of focus regions are excluded ⇒ sharp image.
Hematoxylin & Eosin
Stains according to net charge at pH of staining solution.
Hematoxylin (+) charge so stains (-) charged tissues ⇒ basophillic
DNA/RNA
Proteoglycans & GAGS
Nucleus/Nucleolus
Ribosomes and RER
Eosin is (-) charged and stains (+) charged tisues ⇒ acidophillic
Mitochondria
Lysosomes
Erythrocytes
Collagen
Secretory vacuoles
Cytosol (proteins)
Trichrome Stains
Stains collagen
Masson trichrome ⇒ greenish blue
Mallory trichrome ⇒ sky blue
Elastic Stains
Aldehyde fusion
Orcein
Weigert’s elastic stain
Silver Stains
Reticular Fibers
Carbohydrate Stains
Periodic acid-Schiff (PAS)
Best’s Carmine
Lipid Stains
Oil Red O
Sudan black
Osmium tetraoxide
Stains Summary
Glycocalyx Funtions
- Recognition
- Enzymes
- Immune recognition signals
- Receptors
- Transporters
- Components of channels
Inclusions
- Glycogen
- No membrane
- PAS or Best’s Carmine stains
- Lipid droplets
- no membrane
- Lipofuschsin
- Melanosomes
Nucleolus
Formed around nucleolar organizer regions (NOR).
Assembles signal recognition particles (SRPs)
Nucleus Transport
Nuclear pores are open aqueous channels ⇒ small (9-11nm) molecules passively diffuse
Larger proteins with nuclear localization signal (NLS).
Work with Exportins and Importins
Nucleus and Cell Division
- Lamins phosphorylated ⇒ nuclear lamina and pore complexes disassembled
- Dephosphorylation of lamins ⇒ repolymerize on chromosomes
- Vesicles fuse around chromosomes or groups
- Chromosomes come together, membranes fuse into one
Mitochrondria Function
Calcium sequestration
Apoptosis role
Thermogenesis
Energy generation
Enzyme histochemistry with succinic dehydrogenase.
RER
- Protein synthesis and modification
SER
- lipid and steriod synthesis
- detoxification of lipid soluble drugs and toxins
- sequesters Ca2+
- role in glycogen metabolism
Golgi
Proteins/Lipids made in ER modified and sorted in golgi.
Large cytocentrum/centrosome ⇒ active golgi
Lysosomes
ID with acid phosphatase
Primary ⇒ enzymes, no substrates
Secondary ⇒ active enzymes and substrate
Tertiary ⇒ little or no rsidual enzyme activity, undigested substrates
Peroxisomes
Oxidation of long-chain fatty acids, bile acids, ethanol, and cholesterol.
ID with catalase.
Some with crystalloid of urate oxidase but not humans.
Formed de novo via pre-peroxisomal vesicles from ER
or from pre-existing peroxisomes via fission mediated by Pex proteins or peroxins
Cytosolic Protein Filaments
Overview
Microtubules
- Filaments formed of heterodimers
- Beta tubulins at (+) end
- Alpha tubulins at (-) end
- (-) end of the MT centralized near the nucleus at the MOC
- Dynamic instability
- growth and shrinkage at either end but more easily at (+) end
Microtubule Associated Proteins
(MAPs)
- Organize microtubules
- Stabilize, anchor, and space MTs
- Regulate MT interactions with other elements
- Regulate MT stability and dynamics
- Ex. Tau, MAP1A, MAP2, MAP4, Katanin
Tau & Alzheimer’s Disease
- Tau modulates stability of axonal microtubules
- Hyperphosphorylation of Tau can result in disassembly of microtubules
- Hyperphos tau form complexes ⇒ neurofibrillary tangles
Microtubule
Motor Proteins
Dyneins ⇒ move from + to - ends
Kinesins ⇒ move from - to + ends
Mitotic Spindle
- Chromosome kinetochores captured by (+) end of MT
- Moved to poles by MT dynamics and motor proteins
- Spindle pole (aster) and spindle fibers allow for seperation of daughter chromosomes and daughter cells.
- Chromosome-located kinesin help draw daughter chromosomes to spindle pole
- Spindle fiber kinesins push daughter chromosomes apart
Microtubule Organizing Center
(MTOC)
Centrosome is the main MTOC.
- Site of nucleation
-
γ-tubulin is only found in centrosome
- required for nucleation
- Nucleated at minus end
MT
Accessory Proteins
Anchor MT
Sever and release MT from centrosome
Provides scaffolds and adaptors for other proteins to link to centrosome
Centrioles
- Embedded in centrosome
- Organize centrosome (pericentriolar) matrix
- Become basal bodies in cilia and flagella
- Proximal part of lumen lined by α-tubulin
- provides template for nucleation and arrangement of MT triplets
- Distal part of lumen with centrin
- Proximal and distal connecting fibers connect pair
- 9x3
Basal Bodies
- Formed from centrioles
- Located at base of cilia and flagella
- 9x3+0
Motile Cilia and Flagella
- 9x2+2 arrangement
- Ciliary dynein provides movement
Nodal cilia
Found in embryo @ gastrulation
9x2+0
beat clockwise
Primary Cilia
- Non-motile
- Found on almost all eukarytoic cells
- 9x2+0
- Act as mechanosensors and chemosensors
Keratins
Intermediate filament specific to epithelial cells.
Vimentin
Intermediate filament specific to fibroblasts and chondrocytes and other cells of mesenchymal origin.
Desmin
Intermediate filament specific to myocytes.
Glial fibrillary acidic protein
(GFAP)
Intermediate filament specific to glial cells
Neurofilaments
Intermediate filament specific to neurons
Nuclear lamins
Intermediate filament specific to the nucleus rather than cell specific.
Microfilaments
Characteristics
-
Filamentous acid (F-actin)
- globular/G-actin monomers for a two stranded helix polymer of F-actin
- Free G-actin can be found in the cytoplasm
- Dynamic and polarized
- Barbed end / (+) end ⇒ fast growing
- Pointed end / (-) end ⇒ slow growing
- In non-muscle cells associated with non-muscle myosins ⇒ movment of cargo or microfilament sliding
- In muscle cells, actin associated proteins stabilize polymerized actin to form microfilaments
- Interact with thick filaments containing myosin to cause contraction
Functions of Microfilaments
- Structure of cell cortex
- Core of microvilli
- Anchor microvilli into terminal web
- Major component of terminal web
- Cell-cell attachment via zonula and fascia adherens.
- Cell movement
- filopodia, microspikes, lamellipodia
- attach cell to substratum via focal adhesions
- Form intracellular stress fibers (“muscles”)
- Contractile ring during cytokinesis
Cell Adhesion Molecules
(CAMs)
Transmembrane proteins that mediate cell adhesion.
4 families:
- Cadherins
- Immunoglobulins
- Selectins
- Integrins
Cadherins
- Calcium dependent
- Homotypic binding
- Large role in cell-cell adhesion
- Involved in epithelial-mesenchymal transition
- Several tissue specific families
- Concentrated at adherens junctions
- Actin ⇒ catenins
E-Cadherins
Associated with epithelial cells
N-cadherins
Associatd with CNS, skeletal and cardiac muscle
P-cadherin
Associated with placenta
Selectins
- Calcium dependent
- Bind cells via carbohydrate residues on opposite surfaces ⇒ heterotypic binding
- Several varieties:
- L (leukocytes)
- E (endothelial)
- P (platelet)
- Involved in lyphocyte homing mechanisms
- Involved in inflammation
Immunoglobulins
- Calcium independent
- Adhere to one another via disulfide bonds ⇒ homotypic
- Involved in neuronal guidance in CNS
Integrins
- Calcium independent
- Involved in cell-cell and cell-matrix adhesions
-
Heterotypic binding
- Interact with extracellular matrix molecules
- Collagens
- Laminin
- Fibronectin
- Interacts with actin and intermediate filaments
- Interact with extracellular matrix molecules
- Important in cell behaviors like apoptosis and migration
Tight Junctions
A.k.a occluding junctions or zonulae occludens
- Forms continuous seals around cells in belt-like fashion
- Rows of transmembrane proteins form sealing strands
- Transmembrane:
- occludins
- claudins
- Adaptor protein:
- Scaffolding proteins
- ZO-1, ZO-2, ZO-3
- Scaffolding proteins
- Filaments:
- Actin
Adhering Junction
Characteristics
- Connect cells to one another or to ECM
- Also connect cytoskeletal filaments to plasma membrane
- All adhering junctions are composed of two categories of proteins:
- Adaptor proteins
- Cell adhesion molecule
- Types:
- Zonula adherens
- Desmosome
- Hemidesmosome
- Focal contact/adhesion
Adaptor Proteins
Intracellular achors that attach cytoskeletal filaments to cytoplasmic domain of CAMs.
Most form plaques on cytoplasmic face of membrane.
Zonula Adherens
- Found only in epithelia and only as part of junctional complex
- Forms continuous belt around entire cell
- Transmembrane CAMs:
- E-cadherin
- Adaptor proteins:
- Vinculin
- Catenin
- Alpha-actinin
- Filaments:
- Actin
Fascia Adherens
Similar to zonula adherens but only forms a large irregular patch.
Found in intercalated discs of cardiac muscle cells.
Desmosome
-
Found in epithelia
- Can be part of junctional complex or scattered elsewhere
- Found as part of intercalated disks joining cardiac muscle cells
- Transmembrane CAMs:
- E-cadherin in epithelia
- Adaptor proteins:
- Desmoplankin
- Plakoglobins
- Filaments:
- Keratin in epithelia
Hemidesmosome
- Anchors intermediate filaments of cytoskeleton to cell membrane
- Anchors cells to the basal lamina of basement membrane
- Transmembrane CAMs:
- Integrins
- Type XVII collagen (Bullous pemphigoid antigen 2 / BPAG2)
- Adaptor proteins:
- Plectin
- Erbin
- Dystonin (BPAG1)
- Filaments:
- Keratin
- Basement membrane components:
- Laminin
- Type IV collagen
Focal Contact/Adhesion
- Cell-ECM junctions
- Found in fibroblasts, some epithelial cells, and smooth muscle
- More labile than hemidesmosomes
- Important where contacts must be repeatedly broken and reformed
- Transmembrane:
- Integrins
- Adaptor proteins:
- Talin
- Paxillin
- Alpha actinin
- Vinculin
- Filaments:
- Actin ⇒ stress fibers
- Basement membrane:
- Laminin
- Fibronectin
Gap Junctions
- Found in epithelial cells, osteocytes, neurons, smooth/cardiac muscle cells
- Allows communication & passage of ions/small molecules between cells
- Connexins subunits form a connexon
- Many connexons align to form gap junction
- Can be in open or closed conformation
Epithelial Tissue
- Lines internal and external body surface
- Makes up glands
- Cells closely apposed
Connective Tissue
- Broad category including ordinary CT, blood, cartilage, bone, lymphoid, adipose
- Binds tissues/organs
- Provides support and protection
- Medium for diffusion
- Extensive ECM
- many fibers embedded in ground substance
Surface Ectoderm
Derivatives
- Epidermis
- Enamel
- Internal ear
- Corneal epithelium
- Lens of eye
- Anterior pituitary
Neuroectoderm
Derivatives
- CNS
- PNS
- adrenal medulla
- melanocytes
- mesenchyme of head
- inner structures of teeth
Mesoderm
Derivatives
- CT
- striated and smooth muscles
- heart,
- blood and lymphatic vessels
- spleen
- kidneys
- gonads
- mesothelium
- adrenal cortex
Endoderm
Derivatives
- Epithelial lining of respiratory tract
- urinary bladder
- digestive tract and glands
- thyroid
- parathyroid
- thymus
- lining of ear
Chorus-line effect
Nuclei of dividing epithelial cells move closer to the apical end.
Simple Squamous
Locations
- Lumen of blood vessels (endothelium)
- Lining body cavities (mesothelium)
- Covering epicardium of heart (mesothelium)
- Forming outer wall of renal corpuscles (Bowman’s capsule)
Simple cuboidal
Locations
- Proximal and distal tubules of kidneys
- Smaller ducts in some exocrine glands
Simple Columnar
Locations
- Lining lumen of stomach, intestines, and gall bladder
- Lining lumen of larger ducts in some exocrine glands
- Exocrine pancreas
Minimally keratinized stratified squamous
Locations
- Lining of lumen of esophagus and vagina
- Parts of the oral cavity
- Inner cheeks
Max. keratinized stratified squamous
Location
Epidermis of skin
Stratified Cuboidal
Locations
Ducts of sweat glands
Stratified Columnar
Locations
Parts of very large ducts in some exocrine glands
Ex. submandibular gland
Pseudostratified columnar
Locations
- Parts of the respiratory tract
- trachea
- bronchi
- Parts of the male reproductive tract
- epididymis
- vas deferens
Transitional epithelium
Locations
Parts of the urinary system
Ureters
Urinary bladder
Proximal part of urethra
Transport across epithelial sheet
Many transporting epithelia are simple cuboidal and simple columnar, few are stratified.
Ex. sweat gland ducts
Epithelial Sensory Receptor Function
Taste buds composed of epithelial cells
Olfactory epithelium contains oder-detecting olfactory receptor cells.
Basement Membrane
-
Basal lamina
- Components made by epithelial cells
- Divided into lamina lucida and lamina densa
- Collagen type VI in lamina densa
- Anchoring fibrils
-
Reticular lamina
- Components made by CT cells
- Reticular fibers
Anchoring fibrils (collagen type VII) attach basal lamina to reticular lamina by wrapping around bundles of reticular fibers (collagen type III).
Layers of the Epidermis
Inferior to superior:
-
Stratum Basale
- single layer of cuboidal cells
- rests on basal lamina
- stems cells
-
Stratum Spinosum
- 5-10 layers of cells
- transition from polygonal to flat as you move up
- processess connected by desmosomes
-
Stratum Granulosum
- 3-5 layers
- Elongated cells
- Basophilic keratohyalin granules
- Lamellar granules by EM
-
Stratum Lucidum
- Pale-staining
- Only visible in thick skin
-
Stratum corneum
- 15-20 layers of non-nucleated squamous cells
- filled with keratin
Thick vs Thin
Skin
Based on epidermis thickness.
-
Think skin
- all 5 layers
- thick stratum corneum
- hairless (glabrous)
- only on palms and soles
-
Thin skin
- no stratum lucidum
- thinner stratum corneum
- has hairs (vellus)
Dermis
Layers
-
Papillary layer
- just beneath epithelium in dermal papillae
- loose CT
- Interdigitats with epidermal pegs (ridges)
-
Reticular layer
- deep to papillary
- composed of dense irregular CT
Epidermal-Dermal
Connections
Epidermis connected to dermis via basement membrane.
Dermal papillae fit into inter-papillary pegs of epidermis.
Keratinocyte
- Produces keratin
- Stem cells in stratum basale
- Differentiate as they move up
- Basophillic due to free ribosomes
- Apoptosis then desquamate
Keratinization
Process
- Keratin protein made in stratum basale and assemble into tonofilaments
- In stratum spinosum, tonofilaments bundled into tonofibrils
- Cytoplasm more eosinophilic
- Near top of stratum spinosum, keratohyalin granules made.
- Contain filaggrin and trichohyalin
- Promote aggregation of tonofibrils
- Granules have dispersed into cytoplasm by stratum lucidum.
- Tonofibrils + keratohyalin granule proteins ⇒ soft keratin
- Keratinocyte cornifies
- nucleus and organelles break down
- plasma membrane thickens
- Cells desquamated from stratum corneum as part of “squares”
Formation of Water Barrier
Via membrane-coating granules (MCGs) aka lamellar bodies
-
MCGs first made in stratum spinosum
- Contains lipids and several enzymes
- In upper stratum granulosum, MCGs fuse with plasma membrane
- Contents secreted via exocytosis into intercellular spaces between stratum granulosum and stratum corneum
- Several insoluble proteins form a layer called cell envelope on the inner surface of the plasma membrane which also contributes
- Loricrin
- Desmoplankin
- Elfin
- Envoplakin
- Filaggrin
Melanocytes
- Located between keratinocytes of stratum basale
- Pale staining in H&E
- Derived from neural crest cells
- Have long processes that extend between keratinocytes of stratum basale and spinosum
- Produces melanin
Melanin Synthesis
- Made within melanosomes
- As melanosomes mature, move to processes and pinch off ⇒ cytocrine secretion
-
Phagocytized by neighboring keratinocytes
- Melanosomes and melanin content gradually degraded via autophagy
- Keratinocytes get lighter as they move up
Langerhans Cells
- Stellate, pale staining cells with long processes
- Found mainly in stratum spinosum
- A type of dendritic cell involved in immune response
- Possess membrane bound Birbeck granules
- ping pong paddle shape
- part of endosome system
Merkel Cells
- Epithelial derivatives
- Function as touch receptors
- Lies on basement membrane
- Bound to keratinocytes by desmosomes
- Have keratin filaments
- Contain neurosecretory granules basally
- Base of cell in contact with expanded nerve called Merkel Disc
- Both form Merkel Corpuscle
