Histology Quiz #1 Flashcards
Simple Epithelium Vs. Stratified epithelium
Simple = one layer of cells
Stratified = Multiple Layers of cells
Where is Simple epithelium found
- Lung Alveoli
- Gland and duct lining
- Germal Epithelium in male and female reproductive organs
- Epidermis of skin
- Taste buds
Function of Simple epithelium
- Passive Diffusion
- Secretion + Absorbption
- Provide protection on sin
- Sensory reception
Simple squamous epithelium
Single layer of thin and flattened cells
- Cells = wide and large irregular shape
Found - heart + blood vessles + Lympatic vessles + Serious memebranes + Air sacs + Bowman’s capsule (Kidney) + Tympanic emebranes
Thin = can allow transfer of material across surface = Function - Diffusion + Filtration + Secretion (Exchange gasses + Nutrients)
Structures in Simple Epethlim
Have specialized structures:
1. Microvilia
2. Cilia
3. Sterocillia
Characteristics of Simple epethlium
- No blood supply (A-vasuclar)
- Attaches to basment membrane
- Have latteral attatchments (Sides of cels are attached)
Apical vs. basal side of Epithelial cells
Apical = Side going towrads the lumen
- Side used for function
Basal = Bottom of cell attached to basement memebrane
Simple Squamous epithelium histology
Things to look for:
1. Nuceo are taller than cell (Becuase cell is thin)
Image -
Left - Endothelium(Simple squamous epithlimum lining Blood vessles, lymphatic vessles, and heart)
Right - Mesothelium (Simple squamous epithelium lining body cavities - secretes lubricating substances)
Simple cuboidal epithelium
Single layer of cube-like cells
- Nucleus = in center
Location - Tubules of kindey + overy + thyroid pancerus + repstory tracts
- Are as tall as they are wide
Function - Protection + absorption + Secretion + Excrete waste
Histology of SImple cuboidal epithelium
Things to notice: Uniform shape + karge spherical nucleus in the center
Simple columnar epithelium
Single layer of tall rectagular epithelial cells (taller than they are wide)
Function - barrier + absorbption + Secretion
Specilization of Simiple columnar epithelium
Specilize in secretion (in reproductive and digestive tracts)
Reproductives - secreted growth hormones and cytokines
Digetsive - Keep out pathogens + facilitate absoption of nutrients
Histology of simple columnar
Things to notice - oval shape nucleus closer to the bottom
ALSO see goblet cells (secrete mucus)
Psudeofied epithelium
Appears to be arranged in layers because nuclei appear at different heights BUT it is only one layer of cells
- IS simple because all cells are attached to the basment memebrane
Location - Respitory tract _ fallopian Tubes
Function - Abroptions or secretion
Psudeofied epithelium histology
Things to look for - Pusdofied epithelial cells = associated with goblet cells
Trachea image = can see the cells are ciliated + have thick basment membrane + near goblet cells
Image 2 - salivary gland
Apical surface of epithlium
Faces environments (face lumen or body cavity)
- Free end of the epithelium
Has 3 specialized sturctures:
1. Microvillia
2. Sterocilli
3. Cilia
Microvilia
Finger-like protrusions supported by actin cytoskelaton
- Found on simple cuboidal + columnar epithelium (because function in nutrient uptake)
Location - small intestoine + Proximal tube in kidney
Function - Increases the surface area of the cell to maximize absorption + secretion + reabsorption
- maximizes function of cell surface
Histology of microvillai
Things to look for: Smaller and narrower than cilia (light pink brush boarder on lumen side)
Small intestine - forms a brush borader
Cilia
Finger-like protrusions that beat in coordinated metachronal waves
- Membrane bound organelle
Location - line respitory tract and follopian tubes
Function -
Trachea = movment of Mucus
Fallopian tubes = movment of ovum
Histology of Trachea
See finger projections lining epithelum
Histology of Steroecillia
Things to look for - can see projections facing into the lumen
Stereocillium
Hairlike protrusion on the surface of sensory cells
- Longer than mcrovilla but similar composition
- Not motile = diffreent from cillia
Location - inner ear + epidermis + vas deferens in male reproductive
Function - Mechanosensors aiding in hearing and balance + increase Surface area to faclitate absprotion in male reproductive
Stratified epithelium
Epithlium with multiple layers (only the bottom is in contact with the basement memebrane)
Function - Extrection + secretion + Absorption
Stratified Squamous epitheliam
2+ layers of flat sheet-like epithliaum
- Has flat nucelus
Function - Protection + prevent wtaer loss + stop pathogen invasion (uses tight junctions)
Non-keratinized and kertinized subtypes
How do you define the shape of stratified epithelium
Defined by the shape of cells on teh apical surfce (NOT close to the basal layer)
- basal layer of squamous could be coiboidal or columnar BUT i is still classified as squamous
Non-keratinized statified squamous
Wet and permeable
Secretions prevent drying out
Mucous + tears
Location - Esophogus + tongue + pharnyx + vagina + Cornea
Keratinized
Cells are filled with keratin and dead - has a lyer of dead cells full of keratin = proetcts against abration on the skin
Dry and impermeable
Protects skin from abrasions
Location - Epidermis + parts of mouth
Histology of Startified squamous
Espophogues (non-keratinized) - cels near the lumen are flat and sheet like BUT in multiple layers
Epidermis (keratiziized) - Thicker layer on top = dead cells filled with keratin
Stratified cuboidal
2 or ore layers of cube like epithelia + has a round nucelus in the middle
Function - Protects and strength walls of glands and ducts (fond in salivary glands and sweat glands)
Histology of stratifed cuboidal
Things to look for - see multiple layers of cube cells with round purple nucelus
Esaphagas - have 2 layers of cube cells with round nuceli
Stratified columnar
Layers of stacked epiltheial cells that appear like columns
- More rare form of stratified epithelial
Function - protective + mucus secretion (Ex. lubricate eye)
Histology of Stratified columnar
Salivary gland - in top area = statified columnar
- At the bottom see psuedostartified columnar at the bottom (less compact)
Transitional Epithelial Cells
Cells that change shape and become flattened when stretched
- Changes shape based on expanding and contracting
Top most cells = umbrella cells (covers the layers of cell beneath them)
Location - Bladder
Function - Allows organs to expad and contract by changing shape
Histology of Transitional Epithelial Cells
Relaxed cells = more circular
Contracted = cells are more elongated (lose distict shape)
Types of Junctions
- Tight junctions
- Anchroing Junctions
- Gap Junctions
Tight Junctions
Joins the plasma membrane of adjacent cells
- Can be selective about what can get through the junction (uses specialized transport proteins to only take what they want
Function - forms a barrier to prevent diffusiion + seals off intracellular space
Proteins at junctions - Claudin and occulin proteins
Location - In tissue where need selective permeability - Between cells in GI + between endothelial cells
Celiac and IBD
Result from tight junctions abnormalitiesn –> because increase permability = things get in
Tight Junction Histology
See web of tight junctions at base see based on microvillia)
Anchoring Junctions
Attaches cells to each other and to ECM
Function - resists mechanical stress + prevents cells from pulling apart
Location - In tissues subject to mechanical stress (Ex. Muscle = epidermis)
Composition of Anchoring Junctions
- Intracellular anchor proteins - form plaques inside cell
- Transmembrane adhesion proteins - Link anchor proteins adjacent cel
Transmembrane protein links to inracellular anchr proteins and themselves)
- Anchors through IAP
Example Anchoring Junction
- Adherans Junctions – Connects actin filaments between cellls through cadherin proteins
- Uses Anchor proteins + transmembrane proteins
- Example - Adhesion belt - helps make nueral tube (GOOD image on slides)
EM image - See brush boarder + see adherans junction forming adhesion belt structure
Function - cell morphology
Example 2 Anchoring Junctions
Desmosomes - Connects intermediate filaments (Intermediate filaments are made of keratin)
- Located on the basal lateral surfcae of cells
- CReates intercellular network of filaments
- Spane across and hrough the cell
- Connects cells = forms mesh = can cope with mechanical stress
Structure - have cadherins on extraceullar side and Keratin intermediate filaments in intracellular side
Location - High in cells with lots of mechanical stress
Function - provides tensile strength + structure
EM of desmosomes
See cadherans and see anchor where dense
Gap junctions
Links cells cytoplasm together by forming small chanels
- Allows diffusion of small molecule ions + second messsengers + metabolites)
- Can be regulated by the envirnment (chanel c an close if one cell is stressed so damage doesn’t spread)
- Formed by hexons (5 connecins make a connexon)
Function - Allows cels to Coordinates + synchronizes activities (Example - heart contractions + metabolic coupling + embryogensis)
- Hepatocypes - sympathen nerves cans send a second messenger to neighboring cell
- Embryonic - estblish cell identity in groups
Gap junction Histology
Found in plaques = cluster toegther
Image - can see sende patch with black line
Adenomas
Beginign epithelial tumors
Starts as epithelial cells
Develop in glandular tissue
Usually doesn’t develope into cancer BUT if they do they develop into Carcinoma
Image - can see growth in surface while the other regions are smooth
Carcinoma
Cancer that forms in epithelial tissue
- More agressive than adenocarcinomas (seen in image)
Subtypes:
1. Adenocarcinoma - In organ or gland
2. Squamas cell carcinoma - orginates in the squamas
Found in many organs (Skin, breasts, kidney etc.)
Adenoma vs. Carcinoma
Adenocarcinam:
1. Bengign
2. Grows slower + less agressive
3. Localized/non-invasive
Carcinoma:
1. Cancerous
2. More agressive/grows faster
3. Can stay localized or spread
Carcinoma Subtypes
Types = based on spread
- Carcinoma in situ - has not spread
- Image = see expansion of cells but can stil see cell sturcture s
- Invasive carcinoma - invased local tissue
- Can see cell structure BUT pentrated more tissue
- Metastatic Carcinoma - Has spread
Transition from Adenoma to Carcinoma
Overalll - cells gain ability to proliferate
Have a series of mutogensis - turn on oncogenes and turn off supressive genes
- Have epigenetic regulation
- Tumors ca secrete kemokines and cytokines to agrevate other cell popultions = provides growth factors and pro inflamatory cytokines to promote cancer
Point of malignecey in Carcinoma
Point where the rumore can destroy the basal lamina and spread out
Myopehelial carcinal
Have low mutational burden - mostly fusion genes that are tumoregenic
- Have copy number variants
Metaplasia
A stimuli-induced observable chnage in tissue cause by chnage in differentiation of progenitor cells - Transition from one cell type to another cell type
- reversible tranistion
- Could be early precursor to cancer
Example - columnar cells transtion to squamas cells
Cause = alchol + chronic endometriosis + smoking + helicopter pylori + salt + HPV + injury + Hormones
Purpose = protect body –> if someone goes wrong with ine cell type then another cell comes in to preform functions instead
Types of Metaplasia
- Acinar to ductal - pancreiatic acinar cells differentiate to ductal cells (pyrmidal epithelial cells to columnar epithelial cells)
- Going from cells that line glands on pancoues toc ells that line duct of pancreus
- Intestinal metaplasia - nonkeritinized squamous epithelium –> ninciliates columnar epithelial cells
- Squamous metaplasia - non-squmous epithelium to stratified squamous epithelium
Example metaplasia
Barrets esophagas - nonkeratinzied squamous epithelium truns into nonciliated columnar epithelial cells
- Go from cells in esophogas to cells found in stomach/intestine
Cause - Acid reflux/GERD
Image - see stratified squalmaous cell with cillia going to intestinal columnar instead
Example 2 metaplasia
Endometrium
Caused by trauma + IUD + chronic endometriosis
Columnar to squamaous cell type
Image - see columnar epithelial to squashed squamous cells
Cilia
Long and motile
Come from the basal body in cytoplasm
Project into aplical memebrane
Made of microtubulues and dynein
Use ATP to move in wave like fashion
Often found next to goblet cells thatssecrete mucus –> cilia will then move the mucus (see in histology the black arrow points to goblet cells)
Cilia in body
- Cilia = found in trachea + in lungs
Function - direct the movement of mucus across respitory track to clear the respitry tract of microbes/toxins/devris + protect the lungs
- FOund in female reproductive tract - direct movement of Oocytes to from overy to uterus
Primary ciliary dyskinesis (PCD)
Caused by a defect in cilia - clia is the wrong size or shape so they don’t move correectly OR could be missing cilia alltogether
Symptoms:
1. Have chronic respitory tract infections - because mcirobes buildup i lungs
2. Infertility +
3. Abnormal organ placment - because cilia are involoved in movement of organs during development –> means defective cilia means have organs in wrong place (often mirror image of what should be)
Histolgy.- can see cilia is missing/looks torn
Epidermis
Composed of keratinocyes (eventually become keratin) + melanocytes + Langerhands cells + Merkel cells
- Keratin = important for epithelial lining
Derived from ectoderm
Function - barrrier between the outter envirnment and inner envirnment
What is S. corneum composed of?
S. corneum - composed of flatted plates (Squames) of flattened cross linked keratin and lipids
S. granulosam
S. granulosam - has keratohyalin granuals (ketratin precursors)
- Has laminlar grannuales - produve lipids to prevent dehydration because have glyco lipids on cell surface
Composed of diamond shaped cells (Keratohylalin and laminellar granuals)
S. spinosum
S. spinosum - thickest layer of the epidermis (has cuboidal and slightly lattened keratinocytes connected by desmosomes)
S. basael
S. basael - near basement membrane
- Basment membrane = ogin of keratinocyte division
Single basal layer of mitotically active cuboidal keratinocyte
Serperated from dermis by basal lamina
Dermis
Composed of connective tissue
Divided in papilary and reticular dermis
- reticular - bulk region of collegen (supports the epidermis)
Provides support for the nutrients for epidermis
Hypodemermis
Compossed of fat + hair follciles + sweat glands + sensory receptors
Layer of subcutenous fat + loss connective tissue
Function - attaches skin to underlying tissue + allows skin to move over muscle and tissue
Histology - see wide region = adipose tissue in the hypodemris
Thick skin
Glabrous
Found on palms + flexor surfaces + soles of feet
400 - 600 um
Thin skin
Hairy
75-150 um
Lacks stratum lucidum in epidermis + Stratum spinsum, granulosum, and corneum are narrowing
Layers in epidermis
Melanocytes
Location - Hair follciles and Stratum basale
Synthesis melanins + deposit it to nearby cells
- Deposit melanin by making melanin granuals
Histology - pale/while stain
- Melanocytes shrink when process tissue = the cells are surounded by white –> white buble shows melanoctyes
- near melanocyte = keratinocytes have brown dots that show melanin
Vitalaigo vs. Alopecia
Vitligo = patients don’t have melanoctyoes
Albanism = melanocyes are there but can’t produce melanin or can’t deposit it to keratinocytes
Langerhans cells
Dendritic cells in skin –> idetofy pathogens and microbes –> THEN phagovytose them –> goes the lymphocytes and shows antigens to lymphocytes
- Phagocytosis for immeidate defense and then go to lymph nodes
- Very motile
Two morphologies:
1. Tissue with infection = active = have star shape (engulfing pathogens)
2. No infection = no star shape
Histology = use IHC (hard to see on H/E)
Merkel Cells
Primarly in Thick skin
connects to keratinocyes by desmosomes
Function - Mechanoreceptors (receive afferents nerve signal)
- Communicates with nerve
- sneses touch + thermal regulation
- Communicates with keratinocytes
Desmosomes
Function - adhesion of neighboring epithelial cells + create a tight seal to prevent large foreign proteins or cells from pentrating the skin
Intracellular compoent = intermediate filamenst taht act as anchor
Extracellular compeonent = cadherins that lock with the cadherins of neighboring cell
Keratinocytes in epidermis are tightly joined by desmosomes
Hemidesmoses
Similar to desmosomes BUT link the dermal and epidermal junction
- tether to the basal lamina through hemidesmosomes
Linkes to lower layer of the basment membrane
Work on apical and basal direction
Image - see cells connected to the basement membrane
What layers are affected by Pemphigus Vulgaris and Psrisis
PV - affects spinosum in epidermis
Sporisis = affects cornuem in epidermis
Desmogleins
Transmembrane glycoproteins that mediate epidermal cell-cell adhesion molcules in desmosomes
- Essntial for maintaining integrity of skin and mucous
- Part of desmosomes
Function - cell to cell adhesions + Attchment to basament membrane
Acanthosis
Thickining of epidermis
Acantholysis
Seperation of epidermal cells (caused by the breakdown of intercellular connections)
Pemphigus vulgaris
Autoimmune disorder - autoantigens against desmogolins
Loss of intracellular connections –> Causes blitering
- Keratinocyes in the epidermis and mucosous memebranes lose cell-cell adhesion
Two types:
1. Pemphigus Vulgaris - affects Stratum spinosum
2. Pemphigus foliaceus - affecst stratum foliaceus
Causes - geentic + envirnmental + medications
Pemphicus vulgaris mechanism
B cell deposite Autoantibodies target desomgleinsin stratum spinosum –> leads to lysis of desmosomes = get dissociated of keratnocytes = get gaps –> fluid fills the gaps and get blisters
End - get blisters or erosions on skin and mouth
Secondary complication of pemphigus vulgaris
Becuase have blisters and erosions = get infection + weight loss (painful to eat) + gingevitus
Pemphigus ulgaris histology
- Intraepidermal Acantholysis (seperate of spinosum and basal layeer)
- Intect basal layer – raised pattern (see in image)
3 – Intraepidermal eosinphils
Psorisis
Chronic inflamatory skin disease
Causes scaly patches on the skin (often scalp, elbows, knees)
Have increased epidermal cell turnover
Have increased epidermal cell turnover - Keratinocytes have rapid growth and proliferation –> leads to aberant mutuartion –> leads to accumulation of incompletley difefrentated keratinocytes in stratum corneum
Psorisis causes
Overactive immune system (have positive feedback loop of T cells and Keratinocytes causing inflamation)
Genetic
Envirnmental triggers can cause flares
Psorisis clincal manifestion
Plaque psorisis = scaly red plaques
Guttate Psorisis = many small red spots
Pustular = get small postules (pus-containing blisters)
Psorisis Histopathology
Common feature
1. Acanthosis (thickend stratum spinosum in epidermis with elonfated rete ridges)
- Parakeratosis with nuertophilic collections (Thickend stratum corneum)
- Absent or thin granular layer (Hypogranulosis)
Image - see elongated purple ridges (bone shapes) that go down to the dermis + see thicker corneum (thick pink layer)
Epidermal appendages
Eccrine sweat glands
Apocrine sweat galnds
Sebbacous Glands
Pilosebecous Units
Located in dermis + Hypodermis
Eccrine Sweat Glands
All over body
Structure - Inner has cuboidal cells; outside has myoepthilial cell later ; ducts open onto skin
Function - Thermoregulation
Appocrine Sweat Glands
Present on skin with hair
Structure - Inside has cuboidal cells ; outside has myoepotheal cells; larger lumen
Function - Secretes products that contains proteins
Sebbecous Glands
Found all around body + in places with hair
Sturcture - Simple branch acinar glands ; duct opens to hair follicle
Function - Holocrine secretion of sebum (Lipids)
Pilosebecous glands
Contains Hair follicle + arrector pilli muscle + Sebeccous gland
Meissner’s corpsucles
Mechanico receptors cotaining nerve termials
- enclosed by flattened support cells and connective tissue
- Located in dermal papillae (fingertips + palms + soles of feet)
Function - respond to touch and tactile desxrimination
Paccinean corpsicles
Mechanico receptors
- Consists of unmylinated nerve endings
- Encapsulted by cicular layers of collegen and fibroblasts
- Located in reticular dermis and hypodermis on palms and soles
Function - respond to coarse touch + pressure + vibrartions
Cornification
Cells undergoing terminal differential and cell death
- Forms the cornified layer (protects skin from envrinemnt)
- Also call Karatinzation
Examples - epidermis and in hair follcies
Cornification hair follicle
