Histology Review: Keratinized vs Non-keratinized Epithelium, Adipose, Muscle, Nervous Tissue, Basal Membrane Cells

Vocabulary-style flashcards covering keratinized vs non-keratinized epithelium, adipose tissue types, muscle types, nervous tissue components, and key epidermal cells. Each card defines a key histology term as presented in the video notes.

Keratinized epithelium

Stratified squamous epithelium whose surface cells are anucleate and filled with keratin; forms the stratum corneum and provides a waterproof, protective surface.

Non-keratinized epithelium

Stratified squamous epithelium with nucleated surface cells; lacks a keratin layer (examples: oral cavity, esophagus, vagina, pharynx).

Stratum corneum

Outermost layer of keratinized epithelium composed of anucleate keratin-filled cells; provides waterproofing and abrasion resistance.

Stratum granulosum (keratohyalin granules)

Granular layer of keratinized epithelium containing dark basophilic keratohyalin granules; contributes to keratinization.

Stratum spinosum

Prickly layer between granulosum and basale; characterized by desmosomal connections and spinous cell morphology.

Stratum basale (germinativum)

Basal layer of epidermis with mitotic figures; site of keratinocyte renewal.

Anucleate keratin layer

Keratinized surface cells that have lost their nuclei, forming the protective stratum corneum.

Alveoli of the lungs

Sites where simple squamous epithelium functions in diffusion and gas exchange.

Endothelium

Lining of blood vessels; selective barrier with anticoagulant surface properties.

Mesothelium

Lining of body cavities (serous membranes); secretes lubricating serous fluid.

Glomerular filtration barrier

Structure in the kidney where filtration occurs; involves a specialized endothelium and epithelium with a basement membrane.

Parakeratosis

Keratin layer with retained nuclei; seen in some mucosal surfaces and inflammatory states.

Keratohyalin granules

Dark basophilic granules in the granular layer of keratinized epithelium; essential for keratinization.

White adipose tissue

Tissue with large lipid-filled adipocytes; nuclei pushed to the periphery by lipid droplets; stores energy.

Adipocytes

Cells that store fat as triglycerides in lipid droplets; characteristic of adipose tissue.

Brown adipose tissue

Fat tissue found in infants/small mammals; mitochondria-rich with multilocular lipid droplets; major site of thermogenesis.

Multilocular lipid droplets

Multiple small lipid droplets within brown adipocytes, typical of thermogenic fat.

Thermogenesis

Heat production by brown adipose tissue via mitochondrial activity.

Visceral adipose tissue

Fat stored around internal organs; more metabolically active and linked to cardiometabolic risk.

Subcutaneous adipose tissue

Fat stored beneath the skin; serves as energy reserve, insulation, and cushioning.

Skeletal muscle

Muscle type with long, multinucleated fibers, peripheral nuclei, striations, and voluntary control.

Smooth muscle

Muscle type with spindle-shaped cells, single central nucleus, non-striated, involuntary control.

Differences between skeletal and smooth muscle

Skeletal: long, multinucleated, peripheral nuclei, striated, voluntary; Smooth: spindle-shaped, single nucleus, non-striated, involuntary.

Locations of smooth muscle

Found in walls of hollow organs (e.g., intestines, uterus), vascular walls, and airways.

Ca2+-calmodulin-MLCK pathway

Ca2+ activates calmodulin, which activates myosin light chain kinase, phosphorylating myosin and driving contraction in smooth muscle.

Satellite cells

Muscle stem cells associated with skeletal muscle; important for repair and regeneration.

Neuron

Nerve cell with three major visible parts: soma (cell body), axon, and dendrites.

Nissl substance

Rough endoplasmic reticulum in neurons; visible with certain stains and gives a blue/purple hue to cell bodies.

Methylene blue staining

Stain that highlights Nissl substance and makes cell bodies appear blue.

Neuron vs glial cell on H&E

Neurons are larger with a prominent euchromatic nucleus and nucleolus; glial cells are smaller with denser, darker nuclei.

Keratinocytes

Epidermal cells that produce keratin; provide mechanical strength and protective barriers against abrasion and pathogens.

Melanocytes

Pigment-producing cells in the epidermis that synthesize melanin and transfer it to keratinocytes.

Melanin

Pigment produced by melanocytes; protects DNA from UV by forming a cap over the nucleus.

Melanosomes

Organelles in melanocytes that store and transfer melanin to keratinocytes.

Basement membrane (basal layer cells)

Structural boundary under the epidermis; contains basal cells such as keratinocytes and melanocytes that originate from the epidermis.

Germinativum

Alternative term for the basal layer (stratum basale) of the epidermis where cell division occurs.