5.9: Glossary

Key Terms and Definitions

• Adipocytes - mature cells found in adipose (fat) tissue - filled with a large storage sac of lipid. The lipid in these cells does not stain well with H&E staining, so the cells appear empty.
• Agranulocytes - without prominent-staining cytoplasmic granules.
• Anucleate - without a nucleus.
• Apical - the exposed side of epithelial tissue.
• Aponeuroses - connective tissue connections between to muscle groups.
• Articular cartilage - cartilage that surrounds the articular surface of bones (surfaces where bone meets bone to form a joint). This cartilage decreases friction in movement and provides cushioning.
• Avascular - without blood vessels.
• Axon - axon hillock of the cell body narrows to become the axon, which transmits electrical signals to the axon terminus to communicate with other cells.
• Basal - the anchored side of epithelial tissue.
• Basement membrane - a thin layer of connective tissue that anchors the cells of epithelial tissues to the deeper structures of our body.
• Biconcave - narrow in the center and thicker on the edges, RBC's are biconcave or shaped like a donut (if the icing touched in the center).
• Bone matrix - extracellular matrix containing collagen, calcium-binding proteins, calcium and phosphate depositions.
• Branched - branched cells will resemble the letter Y. A branched cell may connect to one cell on one end, but two cells on the other end.
• Canaliculi - meaning "tiny canal".
• Cell body - contains nucleus and organelles and serves as the biosynthetic center of the cell (synthesizes biological molecules)
• Central canal - running the length of the osteon, containing blood vessels and nerves.
• Chondrocytes - mature cells found in cartilage that monitor and maintain the cartilage extracellular matrix.
• Cilia - surface appendages found in some epithelial cells that move in a rhythmic manner to move mucous across the apical surface of the tissue.
• Collagen - a fibrous protein that has many structural types.
• Columnar - a tall, rectangular cell with an egg-shaped nucleus.
• Cross section - a transverse section, cutting perpendicular to the length of a structure. If cutting a tubular structure, a cross section would produce a ring of tissue.
• Cuboidal - a cube-shaped cell with a round nucleus.
• Dendrites - receive stimuli (signals/information) from environment or other neurons, which are conducted to the axon.
• Dermis - the deepest region of the skin (underlying the epidermis), consisting of two layers: the papillary layer is areolar connective tissue and the reticular layer is dense irregular connective tissue.
• Elastic fibers - provide elasticity to tissues - the ability to be pulled and recoil like a rubber band.
• Erythrocytes - red blood cells, biconcave cells lacking a nucleus and organelles that contain approximately 250 million molecules of hemoglobin.
• Extracellular matrix (ECM) - structural proteins and surrounding ground substance, and minerals that surround cells in our tissues, specifically connective tissues.
• Fibroblasts - cell type found in connective tissue that actively produces the proteins in the extracellular matrix.
• Glial cells/Neuroglia - cells that play an important role in supporting neurons and the nervous system.
• Goblet cells - uni-cellular mucous-producing gland found in epithelium.
• Granulocytes - contain prominent-staining cytoplasmic granules.
• Ground substance - consists of soluble proteins, nutrients, ions, waste products, dissolved gasses.
• Hypodermis - layer of connective tissue, primarily adipose tissue, located deep to the dermis.
• Innervated - having nerve endings for sensory or motor function.
• Intercalated discs - specialized cell-to-cell connections in cardiac muscle tissue containing gap junctions and desmosomes.
• Involuntary - under sub-conscious control, occurs without you thinking about it.
• Keratinized - containing keratin, a structural protein found in skin, hair, and nails.
• Lacunae - A gap, cavity, or depression. Osteocytes (bone) and chondrocytes (cartilage) are found within lacunae.
• Lamellae - sheets or layers.
• Leukocytes - white blood cells, function in immune response.
• Longitudinal section - cut along the long axis of a tissue.
• Lumen - the interior of a tube-shaped organ, like a blood vessel, kidney tubule, or intestines.
• Lymphocytes - a type of lymphocyte (white blood cell) that is part of our adaptive immune system (i.e., B-cells and T-cells).
• Mesenchyme - loosely arranged connective tissue in the embryo that originates from the mesoderm.
• Multinucleated - cell that contains many nuclei.
• Neurons - excitable cells that can receive and send electrical signals.
• Nissl bodies - granular substance in neuron cell body caused by the staining pattern of the rough ER.
• Nucleated - containing a nucleus.
• Osteoblasts - immature bone cells that deposit new bone matrix.
• Osteocytes - mature cells in bone tissue that monitor and maintain the osseous tissue matrix.
• Osteogenic cells - stem cells in bone that can form osteoblasts and osteocytes.
• Osteons - the functional unit in compact bone, consisting of a central (Haversian) canal surrounded by concentric rings/layers of bone matrix called lamellae.
• Perpendicular canals - running at right angles to the central canal, containing blood vessels and nerves.
• Plasma - the fluid in blood, containing dissolved solutes such as: proteins, blood gasses (CO2 and O2), hormones, nutrients, waste products.
• Platelets - fragments of a cell precursor (megakaryocytes) that function to stop bleeding of a damaged blood vessel.
• Polarity - having two sides with different structural or functional characteristics.
• Regeneration - the ability of a tissue to repair itself or to replace old cells with new cells.
• Regeneration capacity - the ability of a tissue to repair or replenish itself.
• Reticular fibers - a specialized type of collagen that forms branching networks (branches on a tree) instead of long, linear strands.
• Simple - in epithelial tissues, a single layer of cells anchored to a basement membrane.
• Soma - means "body".
• Squamous - a scale-like, flattened cell with a disc-shaped nucleus.
• Stratified - in epithelial tissues, a layer of two or more cells with the basal layer anchored to a basement membrane.
• Striated - perpendicular "striped" appearance of skeletal and cardiac muscle cells.
• Superficial - closer to the surface.
• Trabeculae - plates/spikes of bone matrix found in spongy bone.
• Uninucleated - containing a single (1) nucleus.
• Vascularized - containing blood vessels.
• Voluntary - under conscious control - you can actively choose to move your skeletal muscles.