vesicle

Examples of vesicle in the following topics:

• Gas Vesicles

  • There is a simple relationship between the diameter of the gas vesicle and pressure at which it will collapse - the wider the gas vesicle the weaker it becomes.
  • However, wider gas vesicles are more efficient.
  • They provide more buoyancy per unit of protein than narrow gas vesicles.
  • This will select for species with narrower, stronger gas vesicles.
  • Discuss the role of a gas vesicle in regards to survival

• Vesicles and Vacuoles

  • Vesicles and vacuoles are membrane-bound sacs that function in storage and transport.
  • Vesicles can fuse with the plasma membrane to release their contents outside the cell.
  • Vesicles can also fuse with other organelles within the cell.
  • Vesicles perform a variety of functions.
  • Vesicles are involved in metabolism, transport, buoyancy control, and enzyme storage.

• Exocytosis

  • The first stage is called vesicle trafficking.
  • The next stage that occurs is vesicle tethering, which links the vesicle to the cell membrane by biological material at half the diameter of a vesicle.
  • Next, the vesicle's membrane and the cell membrane connect and are held together in the vesicle docking step.
  • The final stage, vesicle fusion, involves the merging of the vesicle membrane with the target membrane.
  • In exocytosis, vesicles containing substances fuse with the plasma membrane.

• The Golgi Apparatus

  • We have already mentioned that vesicles can bud from the ER and transport their contents elsewhere, but where do the vesicles go?
  • The transport vesicles that formed from the ER travel to the cis face, fuse with it, and empty their contents into the lumen of the Golgi apparatus.
  • Finally, the modified and tagged proteins are packaged into secretory vesicles that bud from the trans face of the Golgi.
  • While some of these vesicles deposit their contents into other parts of the cell where they will be used, other secretory vesicles fuse with the plasma membrane and release their contents outside the cell.
  • Several vesicles can be seen near the Golgi apparatus.

• Development of Vision

  • Neural tube: First, there is an outpocketing of the neural tube called optic vesicles .
  • Development of the optic vesicles starts in the three week embryo from a progressively deepening groove in the neural plate called the optic sulcus.
  • Epidermis: The optic vesicles come into contact with the epithelum and induce the epidermis.
  • Some cells in the lens vesicle will be fated to form the cornea and the lens vesicle will develop completely to form the definitive lens.
  • After the closure of the tube they are known as the optic vesicles.

• Transcytosis

  • Transcytosis, or vesicle transport, is one of three mechanisms that facilitate capillary exchange, along with diffusion and bulk flow.
  • Substances are transported through the endothelial cells themselves within vesicles and this mechanims is mainly used by large molecules which are typically lipid-insoluble preventing the use of other transport mechanisms.
  • Briefly the substance to be transported is endocytosed by the endothelial cell into a lipid vesicle which moves through the cell and is then exocytosed to the other side.
  • Vesicles are capable of merging allowing for their contents to mix and can be transported directly to specific organs or tissues.

• Yolk Sac Development

  • At the end of the fourth week, the yolk sac has the appearance of a small pear-shaped vesicle (umbilical vesicle) opening into the digestive tube by a long narrow tube, the vitelline duct.
  • The vesicle can be seen in the afterbirth as a small, somewhat oval-shaped body whose diameter varies from 1 mm to 5 mm.
  • In the meantime Heuser's membrane, located on the opposite pole of the developing vesicle, starts its upward proliferation and meets the hypoblast.

• Fourth Week of Development

  • At the end of the fourth week the yolk sac presents the appearance of a small pear-shaped vesicle (umbilical vesicle) opening into the digestive tube by a long narrow tube, the vitelline duct.
  • The optical vesicle (which will eventually become the optic nerve, retina, and iris) forms at the basal plate of the prosencephalon.
  • White circle represents the area of the optice vesicle.

• Accessory Sex Glands

  • The seminal vesicles secrete a significant proportion of the fluid that ultimately becomes semen.
  • Seminal vesicle fluid is alkaline, resulting in human semen having a mildly alkaline pH.
  • The vesicle produces a substance that causes the semen to become sticky/jelly-like after ejaculation.
  • Seminal vesicle fluid is expelled under sympathetic contraction of the muscularis muscle coat.
  • Prostate with seminal vesicles and seminal ducts, viewed from the front and above.

• Synaptic Transmission

  • The synaptic vesicles fuse with the presynaptic axon terminal membrane and empty their contents by exocytosis into the synaptic cleft.
  • Fusion of a vesicle with the presynaptic membrane causes neurotransmitters to be released into the synaptic cleft.
  • This pseudocolored image taken with a scanning electron microscope shows an axon terminal that was broken open to reveal synaptic vesicles (blue and orange) inside the neuron.
  • The calcium entry causes synaptic vesicles to fuse with the membrane and release neurotransmitter molecules into the synaptic cleft.