Quartz 5

Histology_cheatsheet

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Histology — Organ Recognition Cheatsheet

A concise visual-reference for slide recognition. Focus on the listed identifying features when scanning at low → medium magnification.

Epithelia

  • Simple squamous: very thin, flattened nuclei; lines alveoli, vessels (endothelium).
  • Simple cuboidal: square cells, central nucleus; ducts, kidney tubules.
  • Simple columnar: tall cells, basal nuclei, brush border (microvilli) in intestine; goblet cells present.
  • Pseudostratified ciliated columnar: nuclei at different levels, cilia/goblet cells → respiratory tract/trachea.
  • Stratified squamous (non-keratinized): multiple layers, surface nuclei present → oral mucosa, esophagus.
  • Stratified squamous (keratinized): surface anucleate keratin layer → skin (palmar/plantar).
  • Transitional (urothelium): dome/umbrella superficial cells; stretches (bladder).

Glandular epithelium

  • Exocrine (acinar/tubular): look for ducts; serous acini: dark basophilic cells with central lumen (parotid, pancreas); mucous: pale cells, peripheral nuclei (sublingual, mucous glands).
  • Myoepithelial cells: around acini — help identify salivary glands.
  • Endocrine: highly vascularized cords/follicles (thyroid follicles with colloid). No ducts.

Connective Tissue (CT) — identification

  • Loose CT: abundant cells, sparse fibers; around vessels and under epithelia.
  • Dense irregular CT: thick collagen bundles in multiple directions — dermis, organ capsules.
  • Dense regular CT: parallel collagen bundles — tendons, ligaments (wavy, fibroblasts nuclei in rows).
  • Reticular CT: delicate mesh (type III collagen) — lymphoid organs, liver sinusoids.
  • Adipose: large empty-looking cells (paraffin), peripheral nucleus (WAT); multilocular brown fat (multiple droplets).

Cartilage

  • Hyaline: glassy matrix, chondrocytes in lacunae, territorial vs interterritorial matrix; perichondrium present except articular cartilage.
  • Elastic: similar to hyaline but with dark elastic fibers in matrix — ear, epiglottis.
  • Fibrocartilage: dense type I collagen + chondrocytes in rows/columns; no perichondrium — intervertebral disc, pubic symphysis.

Bone

  • Compact (lamellar) bone: osteons (concentric lamellae) with central Haversian canal; canaliculi radiating from lacunae (osteocytes).
  • Spongy (trabecular) bone: trabeculae with marrow spaces.
  • Osteoblasts: cuboidal basophilic cells on bone surface; osteoclasts: large multinucleated, acidophilic cells in Howship’s lacunae.

Muscle

  • Skeletal muscle: long cylindrical fibers, obvious cross-striations, peripheral multiple nuclei; organized in fascicles with endomysium/perimysium/epimysium.
  • Cardiac muscle: branched fibers, central 1–2 nuclei, striations, intercalated discs (transverse darker lines), abundant mitochondria.
  • Smooth muscle: spindle-shaped cells, single central nucleus, no striations; nuclei corkscrew on contraction.

Nervous tissue

  • Neurons: large cell bodies, prominent nucleus & nucleolus, Nissl substance (basophilic RER clumps) absent at axon hillock.
  • Glia: small nuclei; oligodendrocytes (CNS) vs Schwann cells (PNS). Myelinated axons appear as pale tubes with nodes (LM: separated segments).
  • Peripheral nerve: fascicles with epineurium/perineurium/endoneurium.

Blood & Hematopoietic

  • RBCs: biconcave discs, uniform size (~7–8 µm), anucleate.
  • Neutrophils: multilobed nucleus, pale granular cytoplasm.
  • Eosinophils: bilobed nucleus, large eosinophilic (red) granules.
  • Basophils: dark basophilic granules masking nucleus (rare).
  • Lymphocytes: dense round nucleus, thin rim of cytoplasm.
  • Monocytes: largest WBC; kidney-shaped nucleus, gray-blue cytoplasm.

Lymphoid organs

  • Lymph node: capsule, cortex with follicles (germinal centers), paracortex (T cells), medullary cords and sinuses.
  • Spleen: white pulp (lymphoid follicles around central arteriole), red pulp (cords & sinuses).
  • Thymus: lobulated, cortex (dense immature T cells) darker, medulla lighter with Hassall’s corpuscles.

Common organs — quick cues

  • Liver: plates of hepatocytes radiating from central vein, sinusoids, portal triads (portal vein, hepatic artery, bile duct).
  • Pancreas: exocrine serous acini (basophilic), pale centroacinar cells, scattered endocrine islets (lighter-staining cell clusters).
  • Kidney: cortex with glomeruli and proximal/distal tubules (proximal: fuzzy lumen brush border, acidophilic; distal: clearer lumen, cuboidal).
  • Lung: alveoli lined by simple squamous (type I) and type II pneumocytes (rounded, surfactant); bronchi: pseudostratified ciliated epithelium + cartilage.
  • Skin: epidermis (stratified squamous keratinized), dermis with hair follicles and glands; look for keratin layer.
  • Spleen: look for white pulp follicles around arteries.
  • Thyroid: follicles with colloid; follicular cells cuboidal (resting) or columnar (active).

Tips for the exam

  • Start low magnification: identify empty spaces (lumina), overall architecture (capsules, lobules, ducts).
  • Identify connective tissue pattern (dense vs loose) — gives organ context.
  • Use nuclei shape & position as rapid clues (peripheral vs central, single vs multiple).
  • Look for unique landmarks: intercalated discs (cardiac), goblet cells (respiratory/GI), striations (skeletal/cardiac), osteons (bone), follicles (thyroid).
  • Remember staining artifacts (folds, tears) and preparation effects (collapsed alveoli).

Quick reference file: see the source notes tagged in your vault under parent Histology in All/ (examples: [01 - Introduction](All/01 - Introduction.md), [03 - Epithelium](All/03 - Epithelium.md), [06 - Connective Tissue Proper](All/06 - Connective Tissue Proper.md), [08 - Cartilage](All/08 - Cartilage.md), [09 - Bone](All/09 - Bone.md), [10 - Muscle Tissue](All/10 - Muscle Tissue.md), [11 - Nervous Tissue](All/11 - Nervous Tissue.md), [07 - Blood and Lymphoid System](All/07 - Blood and Lymphoid System.md), [04 - Glandular Epithelia](All/04 - Glandular Epithelia.md)).

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