Junqueira's Basic Histology practicing flashcards

Comprehensive vocabulary practice covering the fundamental concepts of human histology, including tissue types, organ systems, and specialized cell functions.

Histology

The study of the tissues of the body and how these tissues are arranged to constitute organs, from the Greek root "histo" meaning "tissue" or "web."

Extracellular matrix

A component of tissues consisting of many kinds of molecules, such as collagen fibrils and basement membranes, that furnish mechanical support for cells and transport nutrients.

Fixation

The process of preserving tissue structure and molecular composition, typically using agents like formalin (a buffered isotonic solution of $37\%$ formaldehyde).

Microtome

An instrument used for sectioning paraffin-embedded tissues for light microscopy, typically cutting sections at a thickness between $1$ and $10\,m$.

Basophilic

Tissue components with a net negative charge (anionic) that stain more readily with basic dyes, such as toluidine blue or hematoxylin.

Acidophilic

Cationic tissue components, such as proteins with many ionized amino groups, that have affinity for acidic dyes like eosin or orange G.

H&E Staining

The most common simple dye combination where hematoxylin stains acidic structures (DNA/RNA) blue and eosin stains cytoplasmic components and collagen pink.

Resolving power

The smallest distance between two particles at which they can be seen as separate objects; for light microscopy, the maximal power is approximately $0.2\,m$.

Birefringence

The ability of crystalline or highly oriented molecular substances (like collagen or cellulose) to rotate the direction of vibration of polarized light.

Autoradiography

A method of localizing newly synthesized macromolecules in cells or tissue sections using radioactively labeled metabolites detected by silver bromide crystals.

Mesenchyme

An embryonic tissue developed from the mesoderm, formed by elongated undifferentiated cells that give rise to all types of connective tissue cells.

Integrins

Plasma membrane proteins linked to both cytoplasmic cytoskeletal filaments and extracellular matrix components, allowing a constant exchange of influences between the two.

Phagocytosis

A form of endocytosis literally meaning "cell eating," specialized for engulfing and removing particulate matter such as bacteria or dead cells.

Transcytosis

The process of bulk transfer of material across a cell, commonly seen in the endothelial cells lining capillaries.

G proteins

A class of intermediary proteins that bind guanine nucleotides and act on membrane-bound effectors to propagate signals into the cell.

Mitochondria

Membrane-enclosed organelles specialized for aerobic respiration and the production of ATP, typically $0.5-1\,m$ in diameter.

Thermogenin

An inner mitochondrial membrane protein (UCP-1) unique to brown fat that shunts protons back into the matrix to dissipate energy as heat rather than producing ATP.

Ribosomes

Small electron-dense particles ($20 \times 30\,nm$) composed of rRNA and proteins that serve as the site for protein synthesis.

Aggrecan

The dominant proteoglycan in cartilage where the core protein bears several chondroitin sulfate and keratan sulfate chains bound to hyaluronic acid.

Heterochromatin

Electron-dense chromosomal material that appears as coarse granules in the electron microscope and as intensely basophilic clumps in the light microscope.

Barr body

A mass of genetically inactive, heterochromatic sex chromatin found in the somatic cells of females, representing one of the two X chromosomes.

Karyotype

The number and characteristics of chromosomes in an individual, usually analyzed by arresting cells in metaphase using colchicine.

Apoptosis

Programmed cell death or "cell suicide" that occurs rapidly and produces small membrane-enclosed apoptotic bodies without an inflammatory response.

Lamina propria

The layer of connective tissue that supports, provides nutrition to, and binds the epithelium to underlying structures in internal organs.

Zonula occludens

Also called tight junctions, these are the most apical junctions that form a seal to prevent the paracellular flow of materials between epithelial cells.

Connexons

Hexameric complexes formed by proteins called connexins that create central hydrophilic pores for movement of molecules between cells in gap junctions.

Parenchyma

The cells within an organ that are responsible for the main functions typical of that organ.

Holocrine secretion

A mode of secretion where the cell fills with secretory product and then the whole cell is disrupted and shed, typical of sebaceous glands.

Leptin

A $16\,kDa$ polypeptide hormone produced by adipocytes that acts as a "satiety factor" to regulate appetite and the amount of adipose tissue.

Chondrocytes

Cartilage cells that synthesize and secrete the ECM and are located in matrix cavities called lacunae.

Osteon

Also known as a Haversian system, it is a complex of concentric bony lamellae surrounding a small canal containing blood vessels and nerves.

Sarcomere

The repetitive functional subunit of the contractile apparatus in muscle, extending from $Z$ line to $Z$ line, measuring about $2.5\,m$ in resting muscle.

Neuromil

A dense network of fibers from processes of both neurons and glial cells that fills the interneuronal space of the central nervous system.

Nodes of Ranvier

Small nodal gaps in the myelin sheath between adjacent Schwann cells along the axon of a peripheral nerve fiber.

Hematocrit

The volume of erythrocytes in a sample of whole blood, normally about $45\%$ in healthy adults.

Erythrocyte life span

Human red blood cells normally survive in the circulation for about $120$ days before being removed by macrophages of the spleen, liver, or bone marrow.

Diapedesis

The process by which leukocytes migrate out of venules between endothelial cells to enter connective tissue spaces during inflammation.

Kupffer cells

Specialized stellate macrophages bound to the endothelial lumen of liver sinusoids that break down aged erythrocytes and remove debris.

Islets of Langerhans

Compact spherical masses of endocrine tissue in the pancreas containing $\alpha$ cells (glucagon), $\beta$ cells (insulin), and $\delta$ cells (somatostatin).

Surfactant

A phospholipid-rich material produced by Type II alveolar cells that spreads over alveolar surfaces to lower surface tension and prevent collapse.

Melanocytes

Specialized cells of the epidermis, derived from the neural crest, that produce the brownish-black pigment eumelanin.

Canal of Schlemm

Also called the scleral venous sinus, it is the site where aqueous humor is drained from the anterior chamber of the eye.

Tectorial membrane

An acellular layer extending over the spiral organ of Corti in which the tips of the tallest stereocilia of outer hair cells are embedded.

Sella turcica

A cavity of the sphenoid bone where the pituitary gland is located below the brain.

Chief cells

Also called principal cells, these are small polygonal cells in the parathyroid gland that secrete parathyroid hormone (PTH).

Corpus luteum

A temporary endocrine gland formed in the ovary after ovulation that secretes progesterone and estrogens to maintain the uterine mucosa.

Myometrium

The thickest tunic of the uterus composed of interwoven layers of smooth muscle that undergoes hyperplasia and hypertrophy during pregnancy.

Podocytes

Modified epithelial cells of the renal corpuscle's visceral layer with pedicels that form filtration slits around glomerular capillaries.

M cells

Microfold cells specialized for sampling antigens from the intestinal lumen and transporting them to immune cells in the underlying Peyer patches.

Brain sand

Also called corpora arenacea, these are concretions of calcium and magnesium salts in the pineal gland that increase in number with age.