Histology – The Cell, Epithelium & Glands (Review)

Flashcards cover key structures, functions, and pathologies related to cell biology, epithelial tissue, and glandular histology.

What two major compartments make up the protoplasm of a cell?

The cytoplasm and the nucleoplasm.

Name the three main types of endocytic uptake across the plasmalemma.

Pinocytosis, receptor-mediated endocytosis, and phagocytosis.

What is the difference between constitutive and regulated exocytosis?

Constitutive exocytosis is continuous and does not require an external signal; regulated exocytosis relies on clathrin-coated storage vesicles that fuse with the membrane only after an extracellular signal.

Which two physical factors directly influence membrane fluidity?

Temperature and the degree of unsaturation of membrane phospholipid fatty acyl tails.

What are the two broad classes of membrane transport proteins?

Ion channel proteins and carrier proteins.

Define uniport, symport, and antiport transport.

Uniport moves a single substance; symport moves two substances in the same direction; antiport moves two substances in opposite directions.

Which small, bipartite organelles serve as the 'workbenches' for protein synthesis?

Ribosomes.

In rough endoplasmic reticulum, what two docking molecules hold translating ribosomes at the membrane?

Ribophorins (ribosome receptors) and the docking protein for the signal recognition particle (SRP).

State the main function of smooth endoplasmic reticulum in hepatocytes.

Detoxification of lipid-soluble drugs and toxins, and synthesis of cholesterol and lipid molecules.

Which mitochondrial membrane contains the enzymes of the electron-transport chain?

The inner mitochondrial membrane, specifically in the cristae.

What signal targets lysosomal enzymes for packaging in the trans-Golgi network?

A mannose-6-phosphate residue on the oligosaccharide side chain.

Differentiate early endosomes from late endosomes by pH and location.

Early endosomes (pH ≈ 6.0) lie near the cell periphery; late endosomes (pH ≈ 5.5) lie deeper in the cytoplasm and mature into lysosomes.

Which oxidative organelle contains catalase and is formed by fission from pre-existing organelles?

The peroxisome.

What small, barrel-shaped organelles degrade ubiquitin-tagged cytosolic proteins?

26S proteasomes.

Name the two motor MAPs that move cargo along microtubules and state their directions.

Kinesin (anterograde, outward) and dynein (retrograde, inward).

Which intermediate filament protein is the diagnostic immunological marker for epithelial tumors?

Keratin.

Where is ribosomal RNA (rRNA) transcribed and ribosomal subunits assembled?

In the nucleolus.

List the four phases of the cell cycle in order.

G1 phase, S phase, G2 phase, and M phase (mitosis).

During which mitotic stage do sister chromatids separate and migrate to opposite poles?

Anaphase.

What genetic enzyme deficiency leads to Tay-Sachs disease?

Hexosaminidase deficiency (failure to degrade GM2 ganglioside in lysosomes).

Which autoimmune disease targets hemidesmosomal proteins and causes subepidermal blistering?

Bullous pemphigoid.

Name the three regions (layers) that form the light-microscopic ‘basement membrane’.

Lamina lucida, lamina densa (both together = basal lamina), and lamina reticularis.

What class of transmembrane proteins forms the focal sealing strands of a zonula occludens?

Claudins (aided by occludins and JAMs).

Which junctional complex component is composed of E-cadherin linked to actin filaments?

The zonula adherens.

Describe the cytoskeletal attachment of a desmosome.

Intermediate filaments (keratin) form hairpin loops that insert into an intracellular plaque of plakoglobin, plakophilin, and desmoplakin.

What is the basic structural unit of a gap junction connecting two cells?

A pair of aligned connexons, each made of six connexins forming a 2-nm channel.

List three apical surface specializations that increase or aid surface functions in epithelia.

Microvilli, stereocilia, and cilia.

Which epithelial type lines blood vessels and heart chambers?

Simple squamous epithelium called endothelium.

What distinguishing feature identifies pseudostratified columnar epithelium?

All cells contact the basal lamina but only some reach the free surface, giving a stratified appearance.

Where in the body would you find stratified squamous keratinized epithelium?

On the epidermis of skin (e.g., palms and soles).

Which epithelium contains dome-shaped surface cells that flatten during bladder distension?

Transitional epithelium (urothelium).

Define a serous acinus by secretion and cell morphology.

It secretes a watery, enzyme-rich fluid; cells are pyramidal with round nuclei and basophilic cytoplasm containing zymogen granules.

What secretion mode characterizes sebaceous glands and what happens to the secreting cells?

Holocrine secretion; the entire cell dies and becomes the oily product (sebum).

Name the three classical modes of product release in exocrine glands.

Merocrine (eccrine), apocrine, and holocrine.

Which histological feature distinguishes mucous acini from serous acini in mixed glands?

Mucous acini have foamy cytoplasm with flattened basal nuclei; serous cells form dark-staining crescent caps called serous demilunes.

What structural and functional protein is attacked in pemphigus vulgaris?

Desmoglein (a cadherin) of desmosomes, leading to loss of cell adhesion in stratified squamous epithelium.

How does cholera toxin produce life-threatening diarrhea at the epithelial level?

It disrupts tight-junction proteins (ZO-1, ZO-2), allowing massive paracellular efflux of water and electrolytes.

Give one example of metaplasia involving respiratory epithelium.

Chronic smoking can convert pseudostratified ciliated columnar epithelium of bronchi to stratified squamous epithelium.

Which ciliary component provides ATPase activity for motility?

Dynein arms on the A-tubules of each microtubule doublet.

What is the name and composition of the actin-rich layer into which intestinal microvilli insert?

The terminal web, composed of actin filaments, spectrin, tropomyosin, and myosin II.

Which epithelial cell type secretes histamine and heparin from its cytoplasmic granules?

The mast cell (a connective-tissue resident, often viewed with epithelia).

Explain the 'signal hypothesis' in protein targeting.

mRNAs coding for non-cytosolic proteins contain a signal codon that is translated into a signal peptide; SRP binds this peptide, pausing translation until the ribosome docks on RER for co-translational import.

What class of collagen forms anchoring fibrils between lamina densa and lamina reticularis?

Type VII collagen.

Identify two diseases caused by peroxisomal defects.

Zellweger syndrome and adrenoleukodystrophy (not detailed here but both peroxisomal).

Which intermediate filament protein is abundant in astrocytes and useful as a tumor marker?

Glial fibrillary acidic protein (GFAP).

What is the functional significance of stereocilia in the epididymis?

Exact function is unclear, but they probably aid in absorption and maturation of sperm.