Histology-Exam 2 Flashcards
Mesenchymal Cells
Spindle to stellate cells
Scant Cytoplasm
Surrounded by amorphous (no shape) ground substance.
Rich in Hyaluronic acid/ thin reticular/ collagen fibers.
Stem cells for other connective tissue types and smooth muscle.
Adipocytes
Fat cells, Specialize in storing fat
Do not make ECM
Originate from Mesenchymal cell
Surrounded and supported by reticular collagen and fibroblasts.
Will typically be removed by prestaining for H&E
- Brown adipocytes: Prenatal and juvenille, heat producing (multiple small droplets)
White Adipocytes: Peripheral nucleus ( looks like ring)
Fibroblasts
most common in connective tissue proper.
Fusiform- elongated nucleus
Fibroblast Replicating (active) ( more abundant)
Fibrocyte: just sitting (smaller then fibroblast)
Difference is maturity
Produce extracellular matrix
ECM: Amorphous (Functions)
Lubrication
Diffusion
Blockage (barrier)
Adhesion
ECM: Amorphous (Components)
GAGs (Hyaluronic acid (eases migration (mesenchyme), molecular diffusion and lubrication).
GAGs and Proteoglycans (Dermatan [ Chondroitin, Keratan, heparan ] sulfate (lubricants, space filling)
Glycoproteins ( Laminin (adhesion of epithelial cells) (found in: Basal lamina, endomysium, sub-endothelium)
ECM: Fibrous
Produced by fibroblasts mainly but not only. Strong resistant flexible.
Protein fibers: Collagen, reticular fibers, elastin
Collagen Type 1
Fibrillar and most abundant/ strongest
Found in: Bone, ligament, tendon, skin
Collagen Type 2
Fibrillar
Found in: Cartilage
Collagen Type 3
Fibrillar
Found in: Viscera retinaculum ( Lymph nodes, kidney, liver, ect)
Very delicate, Argyrophillic and sometimes PAS + because of high sugar content. Silver stain works well
Produced by fibroblasts
Collagen Type 4
Network (Sheet)
Found in Basement Membrane
Collagen Type 5
Linking (anchoring)
Found in basement membrane
Elastic fiber
Fibrillin and Elastin
Interspersed with collagen bundles, provide stretching ( arteries/ lungs)
Produced by fibroblasts and smooth muscle cells (in blood vessels)
Embryonic connective tissue
Mesenchymal ( loose matrix, hyaluronic acid, stellate cells (lattice)
Mucous/ Mucinous ( Fibroblasts and collagen, Mucinous matrix)
Where can you find Mucinous in adult chickens?
Combs and waddles
Dermal Mucinousis
In adult sharpei’s, excess mucin under skin, keeps producing and increases size of folds.
Connective Tissue Proper
Loose, Dense, Reticular, Elastic, and Adipose tissue
Loose connective tissue
Various cell types Thin fibers (collagen, reticulin, elastin) Soft, Spacious
Dense Connective Tissue
Thick Collagen ( more collagen= dense/ fibrous tissue)
Few cells (fibroblasts)
Regular or irregular
Trichrome stain is good
Reticular connective tissue
Reticulin Fibers
Few Cells
Visceral Stroma ( lymph node, spleen, liver)
Gomori/ GMS is a good stain, Silver stains
Elastic connective tissue
Elastin fibers
Moderate number of cells (fibroblasts)
Sometimes combined with smooth muscle
Adipose Tissue
Adipocytes
Supported by fine collagenous tissue
Empty cells: fat is lost in processing
Sudan stain is good for fat staining.
What is the germ layer Connective tissue arrises from?
Mesoderm
Connective tissue Function
Produce intercellular substance (binding)
Join tissue elements and fill gaps
Provide support (scaffolding or mortaring)
Defend organism by giving rise to blood cells, immune cells.
Healing (scarring) very regenerative when needed.
Extracellular matrix
most abundant component and basis for its classification.
Epidermis is from which germ layer
ectoderm
Epidermis
Stratified Squamous epithelium Keratinocytes present (undergo terminal differentiation (keratinization)
Strata of Epidermis ( Top to bottom
Stratum Corneum Stratum Granulosum *Humans: Stratum Lucidum Stratum Spinosum Stratum Basale (basal layer)
Stratum Basale
Single layer (cuboidal ish or columnar ish cells)
anchored to basement membrane (hemidesmosomes)
Attached to other cells: Desmosomes
Actively reproductive via mitosis.
Stratum Spinosum
Multilayered (polygonal cells)
Attached to other cells: Desmosomes prominent due to tissue sharing
Some reproductive activity
Stratum Granulosum
Single to few layers (plump squamous)
Attached to other cells: Desmosomes (less visible)
Cytoplasm filled with keratohyaline granules
May be invisible in thin skin
Stratum Corneum
Few to many layers (squamous cells)
Attached to other cells (desmosomes rarely visible)
Terminally differentiated cells - SQUAMES
May be preceded by stratum lucidum (thick skin)
These cells are dead, no reproduction.
Other Cells in Epidermis
Melanocytes: Usually in basal layer.
Synthesizes melanin pigment in melanosomes. Melanosomes then interact with Keratinocytes and MQ.
Langerhans cells: Dendritic cells
Antigen presenting cells.
What layer will you find hair and hair follicles
Dermis
Parts of Hair Cell
Bulb (base with germinal cell matrix)
Medulla (central cuboidal/columnar cells, absent in wool)
Cortex (Flat cells, longitudinal to axis)
Outer cuticle (Scaly (squamous) cells) (Pointing upwards)
Parts of Hair Follicle
Dermal Papilla (vascular) goes into hair bulb
Hair Follicle:
Inner root sheath: From germinal cell matrix.(Cuticle, pointing downwards)
Outer Root sheath: Scaly Squamous cells
Connective tissue sheath: Abuts follicular basement membrane
Single (simple) Hair Follicles
Ruminants and horses, vertical in sheep.
How many hair follicles are grouped together in the pig?
3
What kind of hair follicles do carnivores have?
Compound ( single primary, multiple secondary, union at sebaceous gland opening)
Tactile hairs are
Specialized hair follicles. Blood filled sinuses in connective tissue sheath.
Differences in Avian skin
- Epidermis is thinner than mammals
Stratum germinativum (layers usually not obvious) (basal layer, intermediate layers, vacuolated layer)
Stratum Corneum - No glands ( except uropygial gland ( except in emus and ostriches)
- No papillae
Types of Feathers
Contour (wing and Tail)
- Central shaft with quill or calamus ( hollow, Rachis ( upper part of shaft which contains barbs and barbules with hooks)
Down: Hook less barbules
Filoplumes: Hair like, no barbules
What muscle gives feathers movement?
Arrector Plimae smooth muscle (Pillorector muscle) (absent in filoplumes)
Feather Follicle layers
Stratum Corneum
Stratum germinativum
connective tissue layer
What stain is ideal for mucinous connective tissue?
Alcian blue
What are Beaks?
Specialized structure with thick keratinized outer layer called ramphotheca (all dead tissue)
- Usually include herbst corpuscles
What is a Hoof
Keratinized epidermis covering distal end of digit.
Laminitis is also known as…
Founders disease
What causes laminitis?
- Sepsis
- Diet change ( specifically high grain to low grain quickly)
What mammals have scales?
Pangolins
What are epidermal scales ?
modified epidermis: Modified and thickened stratum corneum ( keratin) Can be shed ( corneal layer only)
Found in snakes, chicken leg, beak, ect
What are dermal scales?
Fish primarily, some reptiles, turtle shell, and toads.
Derived from mesenchyme ( mesodermal) Remnants of dermal skin, bony base, cannot be shed
Dermis
Connective tissue ( collagenous (loose irregular most superficial (papillary), and dense irregular deeper (reticular) Contains vascular (blood and lymphatic), nerves (receptors), and glands
Sebaceous Glands
Stratified epithelium Holocrine Secretion: destroying cell Produces Sebum (lipid product). Opens into lumen of hair follicle. Meibomian Gland ( sebaceous gland of eyelid)
What is Meibomian Gland adenoma?
Benign common tumor of eyelid in older dogs (looks like roxies barnacle)
Sweat (sudoriferous) Glands
Simple Cuboidal Epithelium
Apocrine (membrane bound blebs of cytoplasm) or Merocrine ( exocytosis, cytoplasm intact) secretion.
Secretes: GAGs and proteoglycans.
Opens into Epidermal surface or lumen of hair follicle
Surrounded by: Myoepithelium
Mammary Glands
Tubuloacinar glands
Apocrine Secretion: membrane bound blebs of cytoplasm)
Secretion product: Milk (lipids protein sugars)
Open into: interlobular ducts (cuboidal/ columnar epithelium)
Surrounded by myoepithelium
Uropygial glands
In birds
Holocrine secretion of oily sebum for preening.
Radiating simple tubules or branched alveoli (acini)
Opens to: Primary duct through papilla on epidermal surface.
What kind of muscle is the arrector pili muscle and where is its origin and insertion?
Smooth muscle
Origin: Superficial Dermis
InsertionL Connective tissue sheath of hair follicle