lumen

Examples of lumen in the following topics:

• Mucosa

  • Since the mucosa is the innermost layer within the GI tract, it surrounds an open space known as the lumen.
  • Food, mucous, and digestive juices pass through the lumen, and the mucosa comes in direct contact with digested food (chyme).
  • This cross section shows the mucosa in relation to the interior space, or lumen.

• Transcytosis

  • Listeria monocytogenes has been shown to enter the intestinal lumen via transcytosis across goblet cells.
  • Shiga toxin secreted by entero-hemorrhagic E. coli has been shown to be transcytosed into the intestinal lumen.

• Epithelial Tissues

  • Epithelial tissues cover the outer surfaces of the body and the lumen of internal organs; they are classified by shape and number of layers.
  • They also line the lumens of organs in a single layer or multiple layers of cells.
  • These cells absorb material from the lumen of the digestive tract and prepare it for entry into the body through the circulatory and lymphatic systems.
  • Goblet cells secret mucous into the digestive tract lumen.

• Histology of the Small Intestine

  • Because the lumen of the gastrointestinal tract is exposed to the external environment, much of it is populated with potentially pathogenic microorganisms.
  • Peyer's patches function as the immune surveillance system of the intestinal lumen and facilitating the generation of the immune response within the mucosa.
  • In other words, increased surface area (in contact with the fluid in the lumen) decreases the average distance traveled by nutrient molecules, so the effectiveness of diffusion increases.

• Lymphatic Vessel Structure

  • The endothelium is designed with junctions between cells that allow interstitial fluid to flow into the lumen when pressure becomes high enough (such as from blood capillary hydrostatic pressure), but does not normally allow lymph fluid to leak back out into the interstitial space.
  • The next layer is smooth muscles arranged in a circular fashion around the endothelium that alters the pressure inside the lumen (space) inside the vessel by contracting and relaxing.
  • Smooth muscle contractions only cause small changes in pressure and volume within the lumen of the lymph vessels, so the fluid would just move backwards when the pressure dropped.

• The Endoplasmic Reticulum

  • The hollow portion of the ER tubules is called the lumen or cisternal space.
  • Ribosomes transfer their newly synthesized proteins into the lumen of the RER where they undergo structural modifications, such as folding or the acquisition of side chains.

• Processes of the Light-Dependent Reactions

  • In non-cyclic photophosphorylation, cytochrome b6f uses the energy of electrons from PSII to pump hydrogen ions from the lumen (an area of high concentration) to the stroma (an area of low concentration).
  • The electron transport chain moves protons across the thylakoid membrane into the lumen.
  • At the same time, splitting of water adds protons to the lumen while reduction of NADPH removes protons from the stroma.
  • The net result is a low pH in the thylakoid lumen and a high pH in the stroma.

• Tubular Secretion

  • Tubular secretion is the transfer of materials from peritubular capillaries to the renal tubular lumen; it is the opposite process of reabsorption.
  • Active transport—the movement of molecules via ATPase pumps that transport the substance through the renal epithelial cell into the lumen of the nephron.

• Aging and the Heart

  • Deposition of fatty plaques in the lumen of the arteries can lead to blockages and clots.

• Absorption in the Small Intestine

  • The epithelial cells of the villi transport nutrients from the lumen of the intestine into these capillaries (amino acids and carbohydrates) and lacteals (lipids).