CHORIOALLANTOIC MEMBRANE A membrane that surrounds bird embryos, which lies adjacent to the egg shell and contributes to gas exchange.
COLLECTING DUCT Structures of the collecting-duct system that drain the nephrons of urine and that derive from the branched ureteric bud.
ENDOTHELIAL CELLS Flattened cells that grow in a single layer and line blood vessels.
GLOMERULUS The network of blood capillaries in the cup-like end (Bowman's capsule) of the nephron, where waste products are filtered from the blood into the kidney tubule.
GLYCOSAMINOGLYCANS (GAGs). Polysaccharides that comprise repeating disaccharide units of amino-sugar derivatives that are covalently bonded to proteins to function as proteoglycans. Four types of GAG exist according to their sugar residues, and sulphate group numbers and location: chondroitan sulphate and dermatan sulphate; heparin sulphate and heparin; keratan sulphate and hyaluronan.
HEPARAN SULPHATE A sulphated polysaccharide that is found in cell-surface proteoglycans and is structurally similar to heparin. Heparan sulphates are highly heterogeneous, with different lengths of saccharide chain, levels of sulphation and core carbohydrate sequences.
HOMEOBOX A 180-base-pair sequence that is present in many developmental genes of animals and plants. It encodes a DNA-binding helix–turn–helix motif, indicating that homeobox-containing gene products function as transcription factors.
INTERMEDIATE MESODERM A specific region of embryonic mesoderm that forms the kidney and the sex organs.
METANEPHRIC BLASTEMA Loosely organized mesenchymal cells that form nephrons in the kidney.
NEPHROGENIC MESENCHYME Mesenchymal cells adjacent to the tips of the branching ureteric bud that will form the nephrons.
NEPHRON The functional unit of the adult kidney that contains the organ's secretory and excretory parts.
RENAL PELVIS A funnel-shaped structure that is formed at one end by the expanded upper portion of the ureter and at the other by the union of the calyxes of the kidney, which receive urine from the collecting ducts. Urine collected here is funnelled through to the ureter, to be collected in the bladder and then excreted.
STROMA Connective tissue that is made up of cells, such as fibroblasts, and matrix, such as collagen.
WOLFFIAN DUCT A duct that originates from the mesonephros, which gives rise to the ureteric bud of the metanephric kidney. The duct persists in males to contribute to parts of the gonad, but regresses in females.
