Ch 1-3

Polarity in epithelial tissue

The organization of cells with distinct apical (top), lateral (sides), and basal (bottom) surfaces.

Apical surface

Faces the external environment or lumen and may have cilia or microvilli.

Basal surface

Anchors the epithelial tissue to the underlying connective tissue via the basal lamina.

Avascularity

Refers to epithelial tissue's lack of blood vessels, obtaining nutrients via diffusion.

Regeneration in epithelial tissue

The ability of epithelial cells to divide rapidly for repair.

Tight junctions

Specialized connections that seal cells together to prevent the passage of substances.

Gap junctions

Connections that allow ions and molecules to pass between cells for communication.

Simple squamous epithelium

Single layer of flat cells that allows rapid diffusion; found in air sacs of lungs.

Stratified squamous epithelium

Multiple layers of cells that provide protection against abrasion; found in the skin, mouth, and esophagus.

Keratinized stratified squamous epithelium

Epithelial tissue found in the skin, characterized by dead, keratin-filled cells.

Nonkeratinized stratified squamous epithelium

Found in moist areas; contains living cells that provide protection.

Simple cuboidal epithelium

Cube-shaped epithelial cells involved in secretion and absorption; found in kidney tubules and glands.

Simple columnar epithelium

Tall, narrow epithelial cells involved in absorption and movement; found in the gastrointestinal tract.

Pseudostratified columnar epithelium

Appears layered but is a single layer; often ciliated; found in the respiratory tract.

Functions of connective tissue

Provide support, binding, protection, and transport (e.g., blood).

Collagen fibers

Strong and flexible fibers that provide structure in connective tissue.

Osteoblasts

Bone cells that build bone by secreting the bone matrix.

Elastic fibers

Stretchy and resilient fibers found in certain types of connective tissues.

Sebaceous glands

Glands that secrete sebum to lubricate and waterproof skin and hair.

Sweat glands

Glands that produce sweat to help regulate body temperature.

Vitamin D3 production

Stimulated by UV light; essential for calcium absorption in the intestines.

Dermis

Layer of skin between the epidermis and subcutaneous layer, containing two layers: papillary and reticular.

Papillary layer

Upper layer of the dermis, composed of areolar connective tissue, contains fingerprints.

Stratum basale

Deepest layer of the epidermis; contains stem cells, melanocytes, and Merkel cells.

Bone remodeling

Ongoing process of replacing old bone with new bone.

Osteoporosis

Loss of bone density, making bones fragile, often related to aging.

Calcitonin

Hormone that lowers blood calcium levels by promoting calcium storage in bones.

Parathyroid hormone (PTH)

Hormone that raises blood calcium levels by stimulating osteoclast activity.

Endochondral ossification

Process where cartilage is replaced by bone, occurs during fetal development and growth.

Neurons

Cells responsible for transmitting electrical impulses in the nervous tissue.

Neuroglia

Supporting cells in the nervous system that protect and nourish neurons.