fibrous rings

Examples of fibrous rings in the following topics:

• Fibrous Skeleton of the Heart

  • There are four fibrous rings:
  • The left fibrous ring encircles the bicuspid valve.
  • This ring is the thickest and strongest of all the fibrous rings due to the thickness of the left ventricle, which requires more structural support than the other chambers of the heart.
  • The right fibrous ring encircles the tricuspid valve.
  • Transverse section of the heart showing the fibrous rings surrounding the valves.

• Herniated (Slipped) Disc

  • A disc herniation is a common injury caused by a tear in the fibrous ring of an intervertebral disc, allowing the central portion to bulge.
  • A spinal disc herniation is a medical condition affecting the spine in which a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion to bulge out beyond the damaged outer rings .

• Structure, Type, and Location of Cartilage

  • The cartilage fibrous sheath is called the perichondrium.
  • Hyaline cartilage is the most widespread cartilage type and, in adults, it forms the articular surfaces of long bones, the rib tips, the rings of the trachea, and parts of the skull.
  • It owes its flexibility and toughness to the fibrous tissue, and its elasticity to the cartilaginous tissue.
  • Images of microscopic views of the different types of cartilage: elastic, hyaline, and fibrous.
  • Elastic cartilage has the most ECM; hyaline a middle amount; and fibrous cartilage has the least amount of ECM.

• Fibrous Joints

  • Fibrous joints are also called fixed or immovable joints because they do not move.
  • Fibrous joints are connected by dense connective tissue consisting mainly of collagen.
  • Fibrous joints have no joint cavity and are connected via fibrous connective tissue.
  • The skull bones are connected by fibrous joints called sutures.
  • Syndesmoses of long bones and gomphoses of teeth are also types of fibrous joints.

• The Evolution of Roots in Seedless Plants

  • Dicots (flowering plants with two embryonic seed leaves) have a tap root system while monocots (flowering plants with one embryonic seed leaf) have a fibrous root system.
  • In contrast, a fibrous root system is located closer to the soil surface, forming a dense network of roots that also helps prevent soil erosion (lawn grasses are a good example, as are wheat, rice, and corn).
  • In addition, some plants actually have a combination of tap root and fibrous roots.
  • In dicot roots, the xylem and phloem of the stele are arranged alternately in an X shape, whereas in monocot roots, the vascular tissue is arranged in a ring around the pith.
  • (a) Tap root systems have a main root that grows down, while (b) fibrous root systems consist of many small roots.

• Electrocyclic Reactions

  • The reverse reaction may be called electrocyclic ring opening.
  • The electrocyclic ring closure is is designated by blue arrows, and the ring opening by red arrows.
  • In the first case, trans,cis,trans-2,4,6-octatriene undergoes thermal ring closure to cis-5,6-dimethyl-1,3-cyclohexadiene.
  • This mode of reaction is favored by relief of ring strain, and the reverse ring closure (light blue arrows) is not normally observed.
  • Photochemical ring closure can be effected, but the stereospecificity is opposite to that of thermal ring opening.

• Structural Classification of Joints

  • There are three structural classifications of joints: fibrous, cartilaginous, and synovial.
  • There are three types of fibrous joints.
  • These moveable fibrous joints are also termed amphiarthrodial.
  • They allow more movement than fibrous joints but less than that of synovial joints.
  • Image demonstrating the three types of fibrous joints.

• Cycloalkanes

  • Cycloalkanes have one or more rings of carbon atoms.
  • Since all the carbons of a ring are equivalent (a ring has no ends like a chain does), the numbering starts at a substituted ring atom.
  • The three dimensional shapes assumed by the common rings (especially cyclohexane and larger rings) are described and discussed in the Conformational Analysis Section.
  • Hydrocarbons having more than one ring are common, and are referred to as bicyclic (two rings), tricyclic (three rings) and in general, polycyclic compounds.
  • The structural relationship of rings in a polycyclic compound can vary.

• Peptide Synthesis

  • Fibrous keratin chains then twist around each other to form helical filaments.
  • This kind of regular repetition and high glycine content is found in only a few other fibrous proteins, such as silk fibroin (75-80% Gly and Ala + 10% Ser).
  • Collagen chains are approximately 1000 units long, and assume an extended left-handed helical conformation due to the influence of proline rings.
  • Globular proteins are more soluble in aqueous solutions, and are generally more sensitive to temperature and pH change than are their fibrous counterparts; furthermore, they do not have the high glycine content or the repetitious sequences of the fibrous proteins.
  • In contrast to the structural function played by the fibrous proteins, the globular proteins are chemically reactive, serving as enzymes (catalysts), transport agents and regulatory messengers.

• Carbohydrate Molecules

  • Monosaccharides can exist as a linear chain or as ring-shaped molecules; in aqueous solutions they are usually found in ring forms.
  • Because of the way the glucose subunits are joined, every glucose monomer is flipped relative to the next one resulting in a linear, fibrous structure.