Cell Structure and Epithelial Tissue

These flashcards cover key vocabulary related to cell structure, particularly the nucleus, nuclear envelope, and epithelial tissue, providing definitions essential for understanding their functions and characteristics.

Nucleus

Averages 5 μm in diameter; typically spherical or oval and larger than any cytoplasmic organelles.

Nuclear Envelope

Double membrane structure surrounding the nucleus, containing pores that regulate molecular passage.

Nucleolus

Dark-staining spherical body within the nucleus, involved in ribosome production.

Chromatin

Consists of DNA and proteins, plays a role in gene regulation and DNA packaging within the nucleus.

Nuclear Pores

Puncture the nuclear envelope, regulating the entry and exit of molecules.

Nucleoplasm

Jellylike fluid contained within the nuclear envelope, similar to cytosol.

Histones

Proteins that package DNA in chromatin and regulate gene expression through chemical modifications.

Nucleosome

Fundamental unit of chromatin, comprising eight histone proteins wrapped by DNA.

Simple Epithelium

Single cell layer found in areas of absorption, secretion, and filtration.

Stratified Epithelium

Multiple cell layers found in high-abrasion areas for protection.

Apical Surface

The surface of epithelial tissue that is exposed to the body exterior or internal cavity.

Basal Surface

Surface of epithelial tissue attached to underlying connective tissue.

Tight Junctions

Specialized contacts in epithelial cells that prevent leakage between cells.

Basement Membrane

Reinforces epithelial sheet and defines the epithelial boundary, consisting of basal and reticular lamina.

Avascular but Innervated

Characteristic of epithelium; lacks blood vessels but is supplied by nerve fibers.

Endocrine Glands

Ductless glands that secrete hormones directly into the extracellular space.

Exocrine Glands

Glands that secrete products onto body surfaces or into body cavities.