Histology and Pathology Week 1

4 main types of tissue

connective, epithelial, muscle, nerve

Epithelial tissue

Medium stain, outer cell/contact with world, 9 main types; name by shape, layering, and special features

Simple epithelium

All cells contact basal laminate

Basal lamina

Layer of extracellular matrix secreted by epithelial cells, makes up basement membrane

Simple cuboidal epithelium

Square shape, secrete products in glands and ducts, look for them surrounding follicles and glands

Simple columnar epithelium

Tall and thin but round nucleus, can be near goblet cells; found in digestive tract, airways, and other tubes (uterine tubes, epididymis, ductus deferens)

Simple low epithelium

AKA squamous or thin, scale like pattern, squished nucleus

Stratified squamous epithelium

Layers of low epithelium, either has surface terminal cells (vagina, esophagus) or keratin layers (skin)

Keritanized epithelium

Found in skin

Parakeratinized epithelia

Can be found in masticatory mucosa

Stratified cuboidal

Layers of cubes

Stratified columnar

Can be found in gland ducts

Goblet cell

Produces and stores mucus. stains poorly

Ciliated columnar epithelium

Airway and uterine tubes, spread mucus and remove debris

Pseudostratified ciliated columnar epithelium

Respiratory epithelium, appear stratified but are all in contact with basal lamina

Urothelium

Many shapes, appear stratified (pseudostratified), might see multinucleated cells (umbrella cells) at surface; only in ureter, bladder, and urethra (look for lumen)

Connective tissue

Medium to light stain; includes adipose tissue, bone, cartilage, tendons, and more

Loose connective tissue

More neurons, cells make up more mass than collagen fibers (if you can see fibers and a decent amount of nuclei, loose is indicated - think zoom level)

Dense irregular connective tissue

Cells widely separated by thick bands of collagen, few nuclei; thick bands of type I collagen, but fibers randomly oriented

Dense regular connective tissue

Patterned collagen fibers, tendons and ligaments

Adipocytes

Connective tissue proper, lipid store is removed in fixation process leaving empty bubble; nucleus often flattened, thin cytoplasm ring around bubble

Mast cells

store and release substances for inflammatory response (heparin, histamines, leukotrienes; stain darkly due to granules (small circles), found in dermis, respiratory tract, digestive tract

Macrophages

Attack cells that are found in connective tissue; very dark center with lighter surrounding bubbly body (from lysosomes)

Fibroblasts

Help create supporting fibers (collagen), overactivity can cause fibrosis (scarring); small, dark, football like shape

Muscle tissue

Darker stain, differentiate between cardiac, smooth, and skeletal

Cardiac muscle

Only found in heart, branched, has intercalcated disc, lightly striated, 1-2 nuclei per cell

Intercalcated disc

Dark lines where cardiac cells join, have gap junctions for coordinated contractions, fascia adherens and desmosomes

Desmosomes

Like welding points holding cells together

Skeletal muscle

Striated, many peripheral nuclei, geometric shape, large, arranged into fascicles

Endomysium

Innermost surrounding layer of muscles, basal lamina and reticular fibers; surrounds single myocyte/myofiber

Perimysium

Surrounds fascicle

Epimysium

Surrounds whole muscle, fascia, continuous with tendons, dense irregular connective tissue

Smooth muscle

Involuntary muscles, found in blood vessels and digestive system, not striated; small, irregular, pointed/spindle shaped, irregular or even corkscrew nucleus

Nervous tissue

Light stain, differentiate CNS vs PNS, white matter vs grey matter

Cerebellum

Distinct dendritic pattern, near 4th ventricle and choroid plexus

Choroid plexus

Ependymal cells, makes CSF, found in ventricles

Neuron cell bodies

Found in grey matter, usually only cell body stains; dendrites and axons do not stain well unless alternate method is used

Glial cells

Fill gaps between neurons in CNS, nuclei seen in white matter

Pia mater

Looks similar to thin keratin or collagen, thin layer around grey matter in brain and white matter in spine

Peripheral nerve

Typically no neuron bodies, nuclei usually Schwann cells; similar look to connective tissue and smooth muscle but lighter stain, look for PNS connective tissue/organization

Epineurium

Outer cover, surrounds entire nerve, dense irregular connective tissue

Perineurium

Middle layer, surrounds bundles of axons

Endoneurium

Inner layer, around individual axons and Schwann cells

Enteric ganglia

Autonomic ganglia found in digestive tract, help regulate gut movement; look for bundles of nerves between layers of smooth muscle and connective tissue