reticulum

Examples of reticulum in the following topics:

• The Endoplasmic Reticulum

  • The endoplasmic reticulum is an organelle that is responsible for the synthesis of lipids and the modification of proteins.
  • The endoplasmic reticulum (ER) is a series of interconnected membranous sacs and tubules that collectively modifies proteins and synthesizes lipids.
  • The smooth endoplasmic reticulum (SER) is continuous with the RER but has few or no ribosomes on its cytoplasmic surface.
  • This transmission electron micrograph shows the rough endoplasmic reticulum and other organelles in a pancreatic cell.
  • Describe the structure of the endoplasmic reticulum and its role in synthesis and metabolism

• The Rumen and Ruminant Animals

  • The four compartments are called the rumen, the reticulum, the omasum, and the abomasum.
  • The food then enters the first two stomach chambers, the reticulum and rumen (or reticulorumen).
  • The reticulum and rumen work together to separate solids and liquids.
  • Contractions push solid food particles back up into the rumen, while liquids are drained into the reticulum.
  • The ruminant digestive tract has four compartments, the rumen, the reticulum, the omasum, and abomasum.

• Regulatory Proteins

  • The concentration of calcium within muscle cells is controlled by the sarcoplasmic reticulum, a unique form of endoplasmic reticulum in the sarcoplasm.
  • Muscle contraction ends when calcium ions are pumped back into the sarcoplasmic reticulum, allowing the muscle cell to relax.
  • The inward flow of calcium from the L-type calcium channels activates ryanodine receptors to release calcium ions from the sarcoplasmic reticulum.
  • Calcium remains in the sarcoplasmic reticulum until released by a stimulus.

• Excitation–Contraction Coupling

  • A neural signal is the electrical trigger for calcium release from the sarcoplasmic reticulum into the sarcoplasm.
  • The action potential triggers the sarcoplasmic reticulum to release of Ca2+, which activate troponin and stimulate muscle contraction.
  • The sarcoplasmic reticulum is a specialized endoplasmic reticulum found in muscle cells.

• Skeletal Muscle Fibers

  • 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.

• Short-Term Chemical Control

  • When stimulated a signal transduction cascade leads to increased intracellular calcium from the sarcoplasmic reticulum through IP3 mediated calcium release, as well as enhanced calcium entry across the sarcolemma through calcium channels.
  • Once elevated, the intracellular calcium concentration is returned to its basal level through a variety of protein pumps and calcium exchangers located on the plasma membrane and sarcoplasmic reticulum.
  • This is accomplished through reuptake of ions into the sarcoplasmic reticulum via exchangers and expulsion across the plasma membrane.

• Rigor Mortis

  • ATP is no longer provided to operate the SERCA pumps in the membrane of the sarcoplasmic reticulum; these pumps move calcium ions into the terminal cisternae.
  • This release of calcium is caused by the loss of ATP-mediated function of calcium pumps of the sarcoplasmic reticulum, due to ATP depletion in the absence of cellular respiration.

• Ribosomes

  • Many ribosomes are found free in the cytosol, while others are attached to the rough endoplasmic reticulum.
  • In eukaryotes, ribosomes can commonly be found in the cytosol of a cell, the endoplasmic reticulum or mRNA, as well as the matrix of the mitochondria.

• Vertebrate Digestive Systems

  • The four compartments of the stomach are called the rumen, reticulum, omasum, and abomasum.
  • These animals do not have a rumen, but do have an omasum, abomasum, and reticulum.
  • The first two stomachs, the rumen and the reticulum, contain prokaryotes and protists that are able to digest cellulose fiber.
  • The ruminant regurgitates cud from the reticulum, chews it, and swallows it into a third stomach, the omasum, which removes water.

• Characteristics of Eukaryotic Cells

  • numerous membrane-bound organelles (including the endoplasmic reticulum, Golgi apparatus, chloroplasts, and mitochondria)
  • The endoplasmic reticulum modifies proteins and synthesizes lipids, while the golgi apparatus is where the sorting, tagging, packaging, and distribution of lipids and proteins takes place.
  • The nucleus stores chromatin (DNA plus proteins) in a gel-like substance called the nucleoplasm.The nucleolus is a condensed region of chromatin where ribosome synthesis occurs.The boundary of the nucleus is called the nuclear envelope.It consists of two phospholipid bilayers: an outer membrane and an inner membrane.The nuclear membrane is continuous with the endoplasmic reticulum.Nuclear pores allow substances to enter and exit the nucleus.