Beskrive nefronens hovedstrukturer og deres funktioner?
Nephron
Nefronet (fra græsk νεφρός - nephros, der betyder "nyre") er den mikroskopiske strukturelle og funktionelle enhed i nyren. Det består af en nyrekorpuskel og en nyre-tubulus. Nyrelegemet består af en tue af kapillærer kaldet en glomerulus og en omsluttende Bowman-kapsel. Nyretubuli udgår fra kapslen. Kapslen og tubulus er forbundet og består af epitelceller med et lumen. En sund voksen har 0,8 til 1,5 millioner nefroner i hver nyre. Blodet filtreres, når det passerer gennem tre lag: kapillærvæggens endothelceller, dens basalmembran og mellem podocytternes fodprocesser i kapselens foring. Tubuli har tilstødende peritubulære kapillærer, der løber mellem den nedadgående og den opadgående del af tubuli. Når væsken fra kapslen strømmer ned i tubuli, behandles den af de epitelceller, der beklæder tubuli: vand reabsorberes og stoffer udveksles (nogle tilføres, andre fjernes); først med den interstitielle væske uden for tubuli og derefter til plasmaet i de tilstødende peritubulære kapillærer gennem de endothelceller, der beklæder disse kapillærer. Denne proces regulerer mængden af kropsvæske samt niveauet af mange af kroppens stoffer. For enden af tubulus kommer den resterende væske - urin - ud: den består af vand, stofskifteaffald og toksiner.
Nephron
The nephron (from Greek νεφρός – nephros, meaning "kidney") is the microscopic structural and functional unit of the kidney. It is composed of a renal corpuscle and a renal tubule. The renal corpuscle consists of a tuft of capillaries called a glomerulus and an encompassing Bowman's capsule. The renal tubule extends from the capsule. The capsule and tubule are connected and are composed of epithelial cells with a lumen. A healthy adult has 0.8 to 1.5 million nephrons in each kidney. Blood is filtered as it passes through three layers: the endothelial cells of the capillary wall, its basement membrane, and between the foot processes of the podocytes of the lining of the capsule. The tubule has adjacent peritubular capillaries that run between the descending and ascending portions of the tubule. As the fluid from the capsule flows down into the tubule, it is processed by the epithelial cells lining the tubule: water is reabsorbed and substances are exchanged (some are added, others are removed); first with the interstitial fluid outside the tubules, and then into the plasma in the adjacent peritubular capillaries through the endothelial cells lining that capillary. This process regulates the volume of body fluid as well as levels of many body substances. At the end of the tubule, the remaining fluid—urine—exits: it is composed of water, metabolic waste, and toxins.
Nephron