The Cell, Epithelium and Glands – Core Vocabulary

Core vocabulary flashcards covering key structures, processes, and classifications discussed in the lecture on cells, epithelia, and glands.

Cell

Basic structural and functional unit of the body; a mass of protoplasm surrounded by a plasma membrane.

Cytology

The study of cells.

Protoplasm

Living substance of the cell, consisting of nucleus and cytoplasm.

Nucleus

Organelle that houses the genome in the form of chromosomes.

Cytoplasm

Aqueous gel containing water, proteins, lipids, carbohydrates, and various molecules plus organelles.

Mitochondrion

“Powerhouse” organelle that generates ATP.

Rough Endoplasmic Reticulum (rER)

Membranous organelle studded with ribosomes; site of protein synthesis.

Smooth Endoplasmic Reticulum (sER)

Organelle involved in lipid and steroid synthesis, detoxification, calcium storage.

Golgi Apparatus

Organelle that modifies, packages, and sorts proteins from the rER.

Ribosome

Macromolecular complex that translates mRNA into protein.

Lysosome

Membrane-bound vesicle containing hydrolytic enzymes for intracellular digestion.

Peroxisome

Organelle that detoxifies, oxidizes fatty acids, and degrades alcohol via peroxide metabolism.

Cell Cycle

Ordered series of events of cell growth and division; includes interphase and M phase.

Interphase

Non-mitotic portion of the cell cycle (G1, S, G2) during which the cell grows and replicates DNA.

G1 Phase

First gap phase in which cells grow and differentiate.

S Phase

DNA synthesis phase—genome replication occurs.

G2 Phase

Second gap phase; cell prepares for mitosis.

M Phase

Mitotic phase when nuclear division and cytokinesis occur.

Mitosis

Somatic cell division producing two genetically identical diploid daughter cells.

Prophase

Stage of mitosis where chromatin condenses and the nucleolus disappears.

Metaphase

Chromosomes align at the metaphase plate.

Anaphase

Sister chromatids separate and move to opposite poles.

Telophase

Chromosomes decondense; nuclear envelopes and nucleoli re-form.

Cytokinesis

Division of the cytoplasm producing two separate cells.

Meiosis

Two-step division in germ cells producing four non-identical haploid gametes.

Tissue

Group of cells plus extracellular matrix performing a specific function.

Epithelium

Avascular tissue of tightly packed polyhedral cells that lines surfaces and forms glands.

Functions of Epithelium

Protection, barrier, absorption, secretion, lubrication, reproduction, transport.

Avascular

Lacking blood vessels; nutrients diffuse from nearby connective tissue.

Polarity (epithelial)

Structural difference between apical, lateral, and basal domains of epithelial cells.

Basement Membrane

Thin extracellular sheet anchoring epithelium to connective tissue; visible by light microscopy.

Basal Lamina

Electron-dense layer of basement membrane rich in type IV collagen and laminin.

Reticular Lamina

Deeper, diffuse layer of basement membrane containing type III collagen.

Keratin

Intermediate filament protein characteristic of epithelial junctional complexes.

Tight Junction (Zonula Occludens)

Most apical cell-to-cell seal preventing paracellular passage; formed by claudin & occludin.

Zonula Adherens

Band-like anchoring junction below tight junctions; mediated by E-cadherin–catenin complexes linked to actin.

Desmosome (Macula Adherens)

Spotlike anchoring junction using desmoglein/desmocollin to connect intermediate filaments.

Gap Junction

Nexus of connexons allowing ions & small molecules (<1.5 nm) to pass between cells.

Hemidesmosome

Basal junction anchoring intermediate filaments to the basement membrane via integrins.

Focal Adhesion

Integrin-based basal junction linking actin filaments to extracellular matrix; mechanosensitive.

Flagellum

Long, whip-like motile extension; present on human sperm.

Cilium

Long motile apical projection with 9 + 2 microtubule axoneme; propels fluid or cells.

Microvillus

Short, actin-supported, non-motile projection that increases absorptive surface area (brush border).

Stereocilium

Long, branching, actin-based, non-motile projection; found in epididymis and inner ear.

Simple Squamous Epithelium

Single layer of flattened cells (e.g., endothelium, mesothelium); enables passive diffusion.

Simple Cuboidal Epithelium

Single layer of cube-shaped cells (e.g., renal collecting tubules, thyroid follicles).

Simple Columnar Epithelium

Single layer of tall cells often with microvilli or cilia (e.g., stomach, intestines, gallbladder).

Pseudostratified Columnar Ciliated Epithelium

All cells touch basement membrane but nuclei at different levels; ciliated; seen in trachea.

Stratified Squamous Non-keratinized

Multiple layers with surface nucleated cells; moist surfaces (oral mucosa, esophagus, vagina).

Stratified Squamous Keratinized

Surface layers of anucleate keratin; skin and gingiva for extra protection.

Stratified Cuboidal Epithelium

Two or more layers of cube cells; found in sweat-gland ducts, developing ovarian follicles.

Stratified Columnar Epithelium

Rare epithelium with several layers of tall cells; lines conjunctiva and large exocrine ducts.

Transitional Epithelium

Stratified epithelium with dome-shaped umbrella cells; distensible lining of urinary tract.

Exocrine Gland

Gland that retains a duct delivering secretion to a surface or lumen.

Endocrine Gland

Ductless gland releasing hormones directly into the bloodstream.

Unicellular Gland

Single secretory cell such as a goblet cell.

Serous Cell

Pyramidal secretory cell with basophilic cytoplasm and apical granules producing watery protein-rich fluid.

Mucous Cell

Columnar secretory cell with flattened basal nucleus; secretes viscous mucin.

Mixed (Seromucous) Gland

Gland containing both serous and mucous cells; often shows serous demilunes.

Simple Tubular Gland

Unbranched elongated secretory portion lacking a long duct (e.g., intestinal crypt).

Simple Coiled Tubular Gland

Long coiled secretory portion (e.g., eccrine sweat gland).

Simple Branched Tubular Gland

Several elongated secretory portions empty into one duct (e.g., stomach, uterus glands).

Simple Acinar (Alveolar) Gland

Single sac-like secretory portion (small mucous glands of urethra).

Simple Branched Acinar Gland

Multiple saclike secretory units sharing one duct (sebaceous glands).

Compound Tubular Gland

Branched duct draining many elongated units (Brunner glands of duodenum).

Compound Acinar Gland

Branched duct draining multiple acini (exocrine pancreas, parotid).

Compound Tubuloacinar Gland

Branched duct draining mixed tubular and acinar units (submandibular, sublingual glands).

Merocrine Secretion

Exocytosis of secretory vesicles with no cytoplasmic loss (salivary glands, sweat).

Apocrine Secretion

Release of apical cytoplasm enclosing product (mammary gland).

Holocrine Secretion

Disintegration of entire cell releasing product (sebaceous gland).

Intercalated Duct

Initial short duct segment lined by simple cuboidal epithelium receiving glandular secretions.

Striated Duct

Larger intralobular duct with basal striations due to mitochondria-rich infoldings; modifies saliva.

Myoepithelial Cell

Contractile epithelial cell surrounding acini and small ducts to expel secretions.

Histogenesis of Epithelium

Embryonic origin can be ectoderm (epidermis), mesoderm (endothelium), or endoderm (gut lining).

Epithelial Cell Renewal

Continuous mitosis replacing cells; rate inversely related to number of layers (e.g., intestine 4-6 days, epidermis 28 days).

Pemphigus Vulgaris

Autoimmune disease targeting desmogleins causing blistering of skin and mucosa.

Epidermolysis Bullosa

Inherited defect in hemidesmosomes or basal lamina causing fragile, blistering skin.

Claudin

Key transmembrane protein of tight junctions; target of Clostridium perfringens enterotoxin.

Connexin

Protein subunit forming connexons of gap junctions.

Integrin

Transmembrane adhesion receptor linking cytoskeleton to extracellular matrix in hemidesmosomes and focal adhesions.

Dynein Arm

Motor protein on ciliary microtubule doublets responsible for ciliary motility.

Villin

Actin-binding protein at tips of microvilli.

Brush Border

Dense array of microvilli in kidney proximal tubules; height irregular (vs striated border in intestine).