Tissues Derived From Eukaryotic Cells (2A) - MCAT Biological and Biochemical Foundations of Living Systems

Barrier and exchange (protection, absorption, secretion). Epithelial tissues line surfaces and cavities, regulating interactions between the body and its environment.

Epithelial, connective, muscle, nervous. These tissues originate from eukaryotic cells and form the structural and functional basis of animal organs.

Tightly packed cells with minimal extracellular matrix. This arrangement allows epithelial tissue to form continuous sheets that serve as barriers or interfaces for exchange.

Sparse cells embedded in abundant extracellular matrix. The matrix provides mechanical support and enables functions like binding tissues and storing energy.

Support, binding, and structural framework. Connective tissues provide structural integrity and connect other tissues, facilitating organ support and repair.

Contraction to produce movement and force. Muscle tissue contains contractile proteins that enable voluntary and involuntary movements throughout the body.

Rapid signaling and information processing. Nervous tissue consists of neurons and glia that transmit electrical impulses for coordination and response.

The surface facing the lumen or external environment. The apical surface often has specializations like microvilli or cilia for interaction with the environment.

The surface attached to the basement membrane. The basal surface connects to underlying connective tissue, providing anchorage and nutrient access.

Specialized extracellular matrix anchoring epithelium. Composed of basal lamina and reticular lamina, it separates epithelium from connective tissue and supports regeneration.

It has no blood vessels; it is nourished by diffusion. Avascularity ensures epithelium relies on nearby capillaries in connective tissue for oxygen and nutrients.

Number of layers and cell shape. Classification by layers (simple or stratified) and shapes (squamous, cuboidal, columnar) correlates with specific functions.

Rapid diffusion and filtration. Its thin, flat cells facilitate efficient gas exchange in alveoli and filtration in kidney glomeruli.

Simple columnar epithelium. Found in the digestive tract, its tall cells with microvilli enhance nutrient uptake and mucus production.

Pseudostratified ciliated columnar epithelium. Appearing multilayered but single-layered, its cilia propel mucus to trap and remove debris from airways.

Stratified squamous epithelium. Multiple layers of flattened cells keratinize to form a durable barrier against friction and pathogens.

Cells change shape to allow stretching. In the bladder, this allows expansion without tearing, accommodating volume changes during urine storage.

Increase surface area for absorption. Microvilli are finger-like projections that amplify membrane area for efficient nutrient and ion transport.

Prevent paracellular leakage; maintain apical-basal polarity. Tight junctions form seals between cells, creating selective barriers and separating membrane domains.

Strong cell-cell adhesion to resist mechanical stress. Desmosomes link intermediate filaments between cells, providing tensile strength in tissues under stress.

Direct intercellular communication via ion and small molecule flow. Gap junctions form channels allowing rapid sharing of signals and metabolites for coordinated activity.

A single layer of epithelial cells. A single layer maximizes efficiency in processes like diffusion and secretion in organs such as lungs and intestines.

Multiple layers of epithelial cells. Multiple layers provide enhanced protection in areas subject to mechanical stress, like the skin or esophagus.