Tissue Level of Organization

Vocabulary practice flashcards covering tissue classifications, cellular junctions, epithelial, connective, muscle, nervous tissue types, glands, membranes, repair processes, and embryonic germ layers from Anatomy & Physiology Chapter 4.

Tissue

A group of similar cells that have the same specialized function and embryonic origin.

Histology

The science of tissues.

Pathologist

A physician who studies cells and tissues to help diagnose diseases.

Tight Junctions

Intercellular contacts that form fluid-tight seals between adjacent plasma membranes, found in organs like the stomach, intestines, and urinary bladder.

Desmosomes

Cell junctions that anchor adjacent cells to one another or to the basement membrane, found in tissues subjected to mechanical stress like skin and heart muscle.

Gap Junctions

Cellular junctions containing connexons that permit electrical and chemical signals to pass directly between neighboring cells, such as in muscle cells and nervous tissue.

Apical Surface

The free surface of an epithelial cell that faces a body cavity, lumen, or exterior body surface.

Basal Surface

The deep surface of an epithelial cell that adheres to underlying extracellular material.

Basement Membrane

An acellular extracellular matrix layer consisting of a basal lamina secreted by epithelial cells and a reticular lamina that attaches epithelial tissue to underlying connective tissue.

Endothelium

A specialized simple squamous epithelium that lines the interior of heart chambers, blood vessels, and lymphatic vessels.

Mesothelium

Simple squamous epithelium that forms the epithelial layer of serous membranes lining closed body cavities.

Endocrine Glands

Ductless glands that secrete hormones into the interstitial fluid, which then diffuse directly into blood vessels to maintain homeostasis.

Exocrine Glands

Glands that release their secretory products through ducts onto an epithelial covering surface or into the lumen of a hollow organ.

Merocrine Glands

Multicellular exocrine glands that secrete their products via exocytosis without damaging or altering the secretory cell.

Holocrine Glands

Multicellular exocrine glands that accumulate secretory products inside the cell until the entire cell ruptures, releasing the product along with dead cell fragments.

Apocrine Glands

Exocrine glands that gather secretions at the apical portion of the cell, which then pinches off to release the secretion before repairing itself.

Ground Substance

The fluid, gel, or solid component of the extracellular matrix that fills spaces between connective tissue cells and contains water, cell adhesion proteins, and proteoglycans.

Collagen Fibers

Extracellular fibers made of collagen protein that are extremely strong, flexible, and resistant to tensile (pulling) forces.

Elastic Fibers

Networks of long, thin elastin fibers that allow connective tissue to stretch and recoil back to its original shape.

Reticular Fibers

Short, fine, highly branched collagenous fibers that form a soft internal network (stroma) supporting cells in organs such as the spleen and lymph nodes.

Fibroblasts

Immature, active connective tissue cells that synthesize and secrete ground substance and fibers into the extracellular matrix.

Chondrocytes

Mature cartilage cells that reside in small spaces called lacunae within the matrix.

Areolar Connective Tissue

A widely distributed loose connective tissue consisting of randomly arranged collagen, elastic, and reticular fibers with multiple cell types in a semi-fluid ground substance.

Adipose Tissue

A loose connective tissue dominated by adipocytes containing large fat droplets that push cytoplasm and nuclei to the periphery, functioning in energy storage, insulation, and protection.

Hyaline Cartilage

Cartilage with a resilient gel-like matrix containing fine, non-visible collagen fibers and chondrocytes in lacunae, providing flexible support and reducing joint friction.

Fibrocartilage

A high-tensile-strength cartilage packed with dense, visible bundles of thick collagen fibers and chondrocytes in lacunae, designed to absorb compressive shock.

Elastic Cartilage

Cartilage characterized by a dense network of elastic fibers surrounding chondrocytes in lacunae, providing strength along with exceptional structural flexibility.

Osteons

The basic structural units of compact bone tissue consisting of concentric lamellae, lacunae containing osteocytes, and a central canal.

Intercalated Discs

Specialized transverse cell junctions that connect adjacent branching cardiac muscle fibers, facilitating rapid electrical signal transmission.

Parenchyma

The functional cell population of an organ or tissue that conducts tissue renewal and functional regeneration.

Stroma

The supporting connective framework of an organ that, when participating in tissue repair, leads to scar tissue formation (fibrosis).

Granulation Tissue

Fragile, vascularized tissue consisting of budding capillaries, collagen fibers, and fibroblasts that forms during the organization phase of tissue repair.

Ectoderm

The superficial primary germ layer of an embryo that gives rise to nervous tissue and portions of epithelial tissues.

Mesoderm

The middle primary germ layer of an embryo that gives rise to muscle tissues, connective tissues, and portions of epithelial tissues.

Endoderm

The deep primary germ layer of an embryo that gives rise to the inner epithelial lining of the digestive system and associated organs.