General Histology – Lecture LN 25: The Cell

Vocabulary flashcards covering key cell structures, organelles, inclusions, and related terms discussed in the lecture notes.

Cilia

Short, motile, hair-like projections whose rhythmic back-and-forth beating moves fluid or particles across epithelial surfaces; anchored by a basal body.

Flagellum

A single long, tail-like appendage (only in sperm cells) that moves with a propeller-like motion to propel the cell forward.

Basal Body

Centriole-derived organelle located at the base of a cilium or flagellum; initiates and anchors the axoneme.

Apoptosis

Programmed, gene-controlled cell death; an active, orderly process that removes unwanted cells.

Cell (Plasma) Membrane

Thin, flexible boundary composed of a phospholipid bilayer; hydrophilic heads face outward and inward, hydrophobic tails face each other; regulates substance movement.

Phospholipid Bilayer

Double layer of phospholipids forming the core of the plasma membrane with hydrophilic heads and hydrophobic fatty-acid tails.

Nucleus

Cell’s control center containing DNA; directs cellular activities and is the site of RNA synthesis.

Chromatin

DNA associated with proteins in a condensed state; appears as dark basophilic clumps inside the nucleus.

Nucleolus

Dense, round intranuclear body that synthesizes rRNA and assembles ribosomal subunits.

Nuclear Lamina

Thin fibrous layer lining the inner nuclear membrane, providing structural support to the nucleus.

Nuclear Envelope

Double membrane with nuclear pores that separates nucleus from cytoplasm and regulates nucleo-cytoplasmic exchange.

Cytoplasm

Region between plasma membrane and nucleus containing organelles and inclusions suspended in cytosol.

Cytosol

Semi-fluid component of cytoplasm where most metabolic reactions occur.

Endoplasmic Reticulum (ER)

Membranous network; rough ER bears ribosomes for protein synthesis, smooth ER lacks ribosomes and performs lipid synthesis, detoxification, and glycogen metabolism.

Rough Endoplasmic Reticulum (rER)

ER segment studded with ribosomes; synthesizes secretory, lysosomal, and membrane proteins.

Smooth Endoplasmic Reticulum (sER)

ER without ribosomes; synthesizes cholesterol and steroid hormones, detoxifies drugs/alcohol, and aids glycogen synthesis.

Golgi Complex (Apparatus)

Stack of flattened cisternae that modifies, sorts, and packages proteins from the rER for secretion or intracellular use.

Lysosome

Membrane-bound vesicle containing hydrolytic enzymes active at acidic pH; digests waste and damaged organelles.

Peroxisome

Small oxidative organelle that degrades fatty acids, uric acid, and amino acids via oxidative enzymes.

Mitochondrion

Sausage-shaped, double-membraned organelle; powerhouse of the cell, generating ATP; abundant in energy-demanding cells.

Centrosome

Region containing two perpendicular centrioles and pericentriolar matrix; organizes microtubules and the mitotic spindle.

Microfilament

Thin filaments composed mainly of actin (with myosin in muscles); involved in cell movement, cytokinesis, and muscle contraction.

Intermediate Filament

10–12 nm fibers providing mechanical strength; types include cytokeratin, vimentin, desmin, GFAP, and neurofilaments.

Microtubule

Hollow tubules of tubulin that maintain cell shape, serve as tracks for organelle movement, and form the mitotic spindle, cilia, and flagella cores.

Cytoskeleton

Dynamic network of microfilaments, intermediate filaments, and microtubules that provides shape, internal support, and facilitates movement.

Glycogen

Cytoplasmic inclusion acting as the storage form of glucose; broken down for ATP production.

Lipid Droplet

Inclusion containing triglycerides and cholesterol esters; abundant in steroid hormone-producing cells.

Lipofuscin

Yellow-brown waste pigment that accumulates with age; has no metabolic function and is not removed by the cell.