malpighian tubule

Examples of malpighian tubule in the following topics:

• Malpighian Tubules of Insects

  • Malpighian tubules remove wastes from insects by producing urine and solid nitrogenous waste, which are then excreted from the body.
  • Malpighian tubules line the gut of some species of arthropods, such as bees.
  • Malpighian tubules work cooperatively with specialized glands in the wall of the rectum .
  • Malpighian tubules of insects and other terrestrial arthropods remove nitrogenous wastes and other solutes from the hemolymph.
  • Explain how insects use malpighian tubules to excrete wastes and maintain osmotic balance

• Phylum Arthropoda

  • Crustaceans possess green glands while insects use Malpighian tubules, which work in conjunction with the hindgut to reabsorb water while ridding the body of nitrogenous waste.

• Flame Cells of Planaria and Nephridia of Worms

  • Their excretory system consists of two tubules connected to a highly-branched duct system that leads to pores located all along the sides of the body.
  • The cells in the tubules are called flame cells (or protonephridia) because they have a cluster of cilia that looks like a flickering flame when viewed under the microscope .
  • They are similar to flame cells in that they have tubules with cilia and function like a kidney to remove wastes, but they often open to the exterior of the organism.
  • The ciliated tubules filter fluid from the body cavity and carry waste, including excess ions, through openings called nephrostomes.
  • In the excretory system of the (a) planaria, cilia of flame cells propel waste through a tubule formed by a tube cell.

• Nephron: The Functional Unit of the Kidney

  • A nephron consists of three parts: a renal corpuscle, a renal tubule, and the associated capillary network, which originates from the cortical radiate arteries.
  • The renal tubule is a long, convoluted structure that emerges from the glomerulus.
  • The first part is called the proximal convoluted tubule (PCT), due to its proximity to the glomerulus.
  • The third part of the renal tubule is called the distal convoluted tubule (DCT); this part is also restricted to the renal cortex.
  • The glomerulus and convoluted tubules of the nephron are located in the cortex of the kidney, while the collecting ducts are located in the pyramids of the kidney's medulla.

• Other Hormonal Controls for Osmoregulation

  • This, in turn, stimulates the renal tubules to reabsorb more sodium.
  • Almost all of the sodium in the blood is reclaimed by the renal tubules under the influence of aldosterone.
  • By contrast, absence of aldosterone means that no sodium is reabsorbed in the renal tubules; all of it is excreted in the urine.
  • ANP also prevents sodium reabsorption by the renal tubules, decreasing water reabsorption (thus acting as a diuretic) and lowering blood pressure.

• Skeletal Muscle Fibers

  • The sarcolemma of myocytes contains numerous invaginations (pits) termed transverse tubules which are usually perpendicular to the length of the myocyte.
  • Transverse tubules play an important role in supplying the myocyte with Ca+ ions which are key for muscle contraction.
  • Each myofibril is surrounded by the sarcoplasmic reticulum which is closely associated with the transverse tubules.
  • The sarcoplasmic reticulum acts as a sink of Ca+ ions, which are released upon signalling from the transverse tubules.

• Kidney Function and Physiology

  • Second, the renal tubules collect the filtrate.
  • Tubular reabsorption occurs in the PCT part of the renal tubule.
  • Because Na+ is actively transported out of the tubule, water follows to even out the osmotic pressure.
  • It tends to absorb water from the renal tubule and concentrate the filtrate.
  • Additional solutes and wastes are secreted into the kidney tubules during tubular secretion, which is the opposite process to tubular reabsorption.

• Male Reproductive Anatomy

  • Coiled in each testis are seminiferous tubules that produce sperm.
  • Sperm develop in the seminiferous tubules that are coiled inside the testes .
  • The walls of the seminiferous tubules are composed of the developing sperm cells, with the least-developed sperm at the periphery of the tubule and the fully-developed sperm in the lumen.
  • Other cells mixed in the wall of the tubules are the interstitial cells of Leydig; these cells produce high levels of testosterone once the male reaches adolescence.
  • Sperm are produced in the seminiferous tubules, mature in the epididymis, and then are forced out into the vas deferens and out of the body through the urethra during ejaculation.

• The Endoplasmic Reticulum

  • The endoplasmic reticulum (ER) is a series of interconnected membranous sacs and tubules that collectively modifies proteins and synthesizes lipids.
  • The hollow portion of the ER tubules is called the lumen or cisternal space.

• Hormonal Regulation of the Excretory System

  • As ADH (which is also known as vasopressin) causes direct water reabsorption from the kidney tubules, salts and wastes are concentrated in what will eventually be excreted as urine.
  • ADH travels in the bloodstream to the kidneys where it changes the kidneys to become more permeable to water by temporarily inserting water channels, aquaporins, into the kidney tubules.
  • Water moves out of the kidney tubules through the aquaporins, reducing urine volume.
  • In contrast to ADH, which promotes the reabsorption of water to maintain proper water balance, aldosterone maintains proper water balance by enhancing Na+ reabsorption and K+ secretion from extracellular fluid of the cells in kidney tubules.