Histology Flashcards
List the 4 fundamental body tissues
epithelium, connective tissue, nervous tissue, muscle
Locations & 3 characteristics of epithelia
List 3 domains of epithelial cells
Covers/Lines surfaces of body and Interfaces with various biological compartments
- Anchored to Basement Membrane (resting on connective tissue)
- AVASCULAR (relies on diffusion from connective tissue)
- Tightly connected to each other laterally via SPECIALIZED JUNCTIONAL COMPLEXES
Apical (lumen facing), Lateral, Basal (interstitium facing)
How are the different types of epithelial tissues named/characterized? (3 ways)
- Number of cell layers (Simple, Pseudostratified, Stratified)
- Cell Shape (Squamous, Cuboidal, Columnar)
- Keratinization (Keratinized, Non-keratinized)
Simple Squamous Epithelium (Characteristics, Example)
- Monolayer, flat cells, tightly connected
- Parietal layer of Bowman’s Capsule, Blood vessel endothelium, Lung Alveolar Wall, Body Cavity Mesothelium (Peritoneum, Pericardium, Pleura)
Simple Cuboidal Epithelium (Characteristics, Example)
- Monolayer, square cells
2. Renal Tubules, Thyroid follicles, Glandular tissue
Simple Columnar Epithelium (Characteristics, Example)
- Monolayer, very elongated cells
2. Small Intestine, Bronchioles
Pseudostratified Epithelium (Characteristics, Example)
- Monolayer because every cell is touching the basement membrane; however, the different positioning of nuclei give appearance of multiple layers
- Trachea, Epididymus (male reproductive)
Stratified Squamous Epithelium (Characteristics, Example)
- Multi-layered, flat cells on top, square cells near basement membrane (where new cells are generated)
- Moist areas (esophagus, oral cavity, vagina, anal canal)
Keratinized Stratified Squamous Epithelium (Characteristics, Example)
- With the multiple extra layers of dead cells (no nuclei) - to act as protective layer
- Skin
Transitional Epithelium
Characteristics, Example
Specially made for its location
TWO STATES
1. Relaxed: 5-6 layers, top layer is large, pillowy, cuboidal cells
2. Stretched: 2-4 layers, top layer is flattened
3. Urinary Tract (ureter and bladder)
3 Specializations of the Apical Domain (examples for each)
- Microvilli - greatly increase surface area of apical side for reabsorption (intestinal lumen and kidney PT)
- Stereocilia - very long, thin, non-motile microvilli in male reproductive system (epididymus + ductus deferens)
- Cilia - actively motile processes (line respiratory tract and female reproductive tract - help move ovum/particles along)
Tight Junction (Name, Family/Location, Function, Proteins)
- Zona Occludens
- At TOP of Apical Junctional Complex in Lateral Domain of Epithelia
- Block Movement b/w cells in ECM, maintain cell polarity, prevent fluid penetration
- Claudins + Occludins
Adherens Junction (Name, Family/Location, Function, Proteins)
- Zonula Adherens
- Just below zona occludens in Apical Junctional Complex in Lateral Domain of Epithelia
- Provide Strength, links nearby cell’s actin cytoskeletons, form continuous band around cells - 6 pack appearance
- Cadherins (binding actin)
Desmosomes (Name, Family/Location, Function, Proteins)
- Macula Adherens
- Deep below zonula adherens in Apical Junctional Complex in Lateral Domain of Epithelia
- binds IF cytoskeletons - abundant in stratified epithelia exposed to stress
- Cadherins (bind IF not actin)
Gap Junction (Name, Family/Location, Function, Proteins)
- Scattered throughout Lateral Domain of Epithelia
- Direct pore between 2 closed membranes - allows passage of small mLc/nutrients b/w adjacent cells
- Helps coordinate epithelial function
- Connexons
2 components of the basal domain
- Basement membrane - thin non-cellular layer between epithelium and connective tissue - structural support for epithelium + selective barrier for material movement
- Hemidesmosomes - like desmosomes but anchor cell to BM (not other cells); attaches to keratin IFs with INTEGRINS (bind type IV collagen in BM)
Definition of histology + Components of the H&E Stain
Histology - the way we observe cells make up our body
H - Hemotoxillin - basic - stains purple - binds DNA/nucleus
E - Eosin - acidic - stains pink (ex. collagen)
Connective Tissue (Function, Location, Developmental Derivation)
- Supportive Framework for all other tissue types in the body
- Found in every organ system and helps align epithelium
- Derived from Mesodermal layer during development (Paraxial Mesoderm - somatic tissues; Lateral Plate Mesoderm - visceral tissues)
2 Roles of Basement Membrane in tissue structure
- Structural: anchors epithelium to connective tissue
2. Protective: acts as barrier between epithelium and connective tissue
6 types of connective tissue cells and their role
- Fibroblast/Myoblast: Make type IV collagen, nucleated, structural support + healing/remodeling - used to make scars
- Macrophage: (AKA: histiocytes in tissue), structural support + healing/remodeling
- Adipocyte: Fat Storage
- Pericyte: Structural support around blood vessel
- Mast Cell: Round cell with granules, defense + healing/remodeling by releasing cytokines to trigger immune system
- Neutrophils (Other WBC): Defense + Healing/Remodeling
Dense Connective Tissue (Features, Function, Example)
- Irregular - non-parallel pink fibers to provide multidirectional impact resistance (ex: skin, joint capsules b/w fascia)
- Regular - parallel pink fibers to provide tensile strength and resistance to lengthening (ex: tendons)
Mainly composed of collagen fibers (elastin fibers somewhat present)
Loose Connective Tissue (Features, Function)
- Vascular, Pink collagen fibers, with more space (space filled with ground substance - GAGs and Hyaluronan)
- Space allows room for material to pass from blood to epithelium
Connective Tissue in Arteries
- Predominantly Elastin fibers in the Tunica Media of arteries to help vessel stretch and expand to increase volume load
- helpful when paired with smooth muscle (can expand AND contract)
* NOT A TYPE OF CONNECTIVE TISSUE *
Reticular Connective Tissue (Features, Function, Example)
- Meshwork in hematopoietic tissues to open up spaces for cells to pass through while providing structure
- Spleen and lymphoid tissues
Adipose Connective Tissue (Function)
- Fat Storage - extra connective tissue helps give adipocytes some structure (and not just melt down)
Examples of Specialized Connective Tissue
Bone, Blood, Cartilage
types of fibers and substances in the ECM (and their function)
- collagen fibers - resistability
- elastin fibers - elasticity
- GAGs - ground substance
- Hyaluronan - ground substance
Ground Substance: Structure; Hydrates tissue helps deliver nutrients, cell migration/sensing/reaction to microenvironment
Defining feature of muscle tissue (and its two types and functions)
CELLS THAT CAN CONTRACT
Skeletal Muscle: Voluntary Movement
Smooth Muscle: Involuntary Movement
Skeletal Muscle (Histological Findings)
- covered by thin layer of fascia
- PARALLEL arrays of muscle fibers (myofibrils)
- longitudinal pink (eosinophilic fiber filled with myofibrils)
- multiple nuclei pushed to the edge of the cell
- STRIATED due to sarcomere’s alternating thick/thin filaments (only seen longitudinally, not cross-sectionally)
- Cross-section: CONCENTRIC fibers so they shorten upon contraction
Skeletal Muscle (Structure)
1 myocyte - many myofibrils - back to back arrangements of sarcomeres - alternating thick/thin filaments
Thick Filaments: Myosin
Thin Filaments: Actin, Troponin, Tropomyosin
Depolarization - Increased IC Ca ions - free more IC Ca ions from sarcoplasmic reticulum - bind troponin and allow actin to bind myosin
Atrophied Skeletal Muscle (Histological Findings)
- more space b/w myocytes, spaces tend to fill with firbosis
- wavier, thinner myocytes look pinker due to cellular degeneration
- Nuclei start to centralize
Cardiac Muscle (Histo. Findings, Contraction)
- Striated due to sarcomeres & actin-myosin binding
- Shorter + Branched myofibrils
- Centralized nuclei
- Intercalated discs: cardiac myocytes attach end-to-end with these specialized junctions (important in propagating action potentials)
Contraction depends more on extracellular Ca ions that enter through T-tubules
Smooth Muscle (Histo. findings, Contraction)
- No striations, because no sarcomeres
- Network of actin-myosin filaments connected by “dense bodies”
- bright pink (eosiniphilic cytoplasm)
- blunt ended nuclei (cigar shape)
Form long lines (fascicles?) and surround the walls of blood vessels
NO TROPONIN
Increased calcium binds calmodulin, activates myosin light chain kinase, phosphorylates myosin, interacts with actin
Peripheral Nerve (Histo Findings, Cross-sectional v. Longitudinal) [CS v L]
- Fascicle - bundle of many neuronal axons each surrounded by a clearing of myelin (CS)
- Axons - pink fibrillary tissue (L)
- Perineurium - lines outside of fascicles for structural support - thin elongated cells that form a ring (CS) or white space around fascicle (L)
- Epineurium - further supportive structure for fascicle (fibroblastic tissue)
- Schwann Cell Nuclei - elongated, wavy, pointed on one end (L also little CS)
- Myelin - white spaces between axons (L)
Schwann Cell (Functions, Location)
- Produces Myelin (a. Protects axon, b. helps propagate action potentials)
- PNS
Ganglion (Histo. Findings, Definition)
collections of neuronal cell bodies in the PNS
- Ganglion cell - large cell/cytoplasm - large nucleus off to one side - nucleolus present - cytoplasmic granules: NISSL BODIES - rough ER in neurons responsible for protein production
- Satellite cells - support cells for ganglion
- Schwann cells - very much in the background
Central Nervous Tissue (Grey Matter v. White Matter, HIst Findings for non-glial cells)
Gray Matter: cell bodies and supportive cells in the CNS
White Matter: Axons/Sensory processes of neurons in CNS
1. Neuron cell body (star shape, big nucleus, input dendrites, long axonal process, granular cytoplasm (NISSL BODIES))
2. Neuropil - gray fuzzy stuff (network of nerve fibers)
Types of Supportive Glial Cells (Structure and Function)
- Astrocytes - scaffolding for brain tissue (like epineurium/supportive fibroblasts), cell processes surround neural processes
- Oligodendrocytes - surround neurons + produce myelin (like Schwann cells but CNS); “fried egg” look with small round nucleus and big clearing around it
- Microglia - macrophages in CNS, eat debris, foreign material, organisms
- Ependymal Cells - line ventricles + form choroid plexus to produce CSF (round elongated cells near CSF ventricles)
