vessel

Examples of vessel in the following topics:

• Structure of the Lymphatic System

  • The lymphatic system consists of lymphatic vessels and associated lymphoid organs.
  • The lymphatic vessels are the lymphatic system equivalent to the blood vessels of the circulatory system and drains fluid from the circulatory system.
  • The network of lymph vessels consists of the initial collectors of lymph fluid, which are small, valveless vessels, and goes on to form the precollector vessels which have rudimentary valves that are not fully functional.
  • Skeletal muscle contractions also move lymph through the vessels.
  • The lymphatic vessels make their way to the lymph nodes and from the lymph nodes the vessels form into trunks.

• Lymphatic Vessel Structure

  • The general structure of lymphatic vessels are similar to that of blood vessels.
  • This is largely because blood vessels and lymphatic vessels are the two types of vessels in the body.
  • An endothelium is a general term for the inner layer of a vessel, and blood vessels have them as well as lymph vessels.
  • Larger lymph vessels have many more layers of adventitia compared to smaller lymph vessels.
  • Valves are found in larger lymph vessels and collecting vessels and are absent in the lymphatic capillaries.

• Vascular Spasm

  • Vasoconstriction is the narrowing of the blood vessels, which reduces blood loss during injury.
  • Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the smooth muscle wall of the vessels, particularly in the large arteries and small arterioles.
  • The process is the opposite of vasodilation, the dilation and expansion of blood vessels.
  • Smooth muscle in the vessel wall goes through intense contractions that constrict the vessel.
  • If the vessels are medium to large-sized, the spasms slow down immediate outflow of blood, lessening the damage but still preparing the vessel for the later steps of hemostasis.

• Distribution of Lymphatic Vessels

  • Lymphatic vessels are most densely distributed near lymph nodes.
  • Afferent lymphatic vessels: the lymph vessels that flow into a lymph node.
  • Efferent lymphatic vessels: the lymph vessels that flow out of a lymph node.
  • They may also refer to lymph vessels that leave the thymus or spleen (which lack afferent vessels).
  • The lymphatic vessels start with the collection lymph fluid from the interstitial fluid.

• Development of Blood and Blood Vessels

  • New blood vessels are formed from endothelial stem cells, which give rise to the endothelial cells which line the vessels.
  • ESCs will eventually produce endothelial cells (ECs), which create the thin-walled endothelium that lines the inner surface of blood vessels and lymphatic vessels.
  • As part of the circulatory system, blood vessels play a critical role in transporting blood throughout the body.
  • Formation of new blood vessels occurs by two different processes: vasculogenesis and angiogenesis.
  • The latter occurs when new vessels are built from preexisting blood vessels.

• Muscular Arteries

  • Distributing arteries are medium-sized arteries that draw blood from an elastic artery and branch into resistance vessels.
  • Muscular or distributing arteries are medium-sized arteries that draw blood from an elastic artery and branch into resistance vessels, including small arteries and arterioles.
  • In contrast to the mechanism elastic arteries use to store and dissipate energy generated by the heart's contraction, muscular arteries contain layers of smooth muscle providing allowing for involuntary control of vessel caliber and thus control of blood flow.
  • The splenic artery (lienal artery), the blood vessel that supplies oxygenated blood to the spleen, is an example of a muscular artery.

• Blood Vessel Function

  • Blood vessels carry nutrients and oxygen throughout the body and aid in gas exchange.
  • Additionally, blood vessels provide the ideal network for immune system surveillance and distribution.
  • Mechanically the blood vessels, especially those near the skin, play a key role in thermoregulation.
  • Blood vessels can swell to allow greater blood flow, allowing for greater radiant heat loss.
  • Conversely, blood flow through these vessels can be lessened to reduce heat loss in colder climates.

• Blood Vessel Structure

  • Blood vessels are flexible tubes that carry blood, associated oxygen, nutrients, water, and hormones throughout the body.
  • Blood vessels are key components of the systemic and pulmonary circulatory systems that distribute blood throughout the body.
  • The junctions between vessels are called anastomoses.
  • In smaller arterioles or venules, this subendothelial layer consists of a single layer of cells, but can be much thicker in larger vessels such as the aorta.
  • The tunica intima is surrounded by a thin membrane comprised of elastic fibers running parallel to the vessel.

• Open and Closed Circulatory Systems

  • The circulatory system can either be open or closed, depending on whether the blood flows freely in a cavity or is contained in vessels.
  • In an open circulatory system, the blood is not enclosed in the blood vessels, but is pumped into a cavity called a hemocoel.
  • (a) In closed circulatory systems, the heart pumps blood through vessels that are separate from the interstitial fluid of the body.
  • (b) In open circulatory systems, a fluid called hemolymph is pumped through a blood vessel that empties into the body cavity.
  • Hemolymph returns to the blood vessel through openings called ostia.

• Distribution of Blood

  • Blood is circulated around the body through blood vessels by the pumping action of the heart .
  • Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries and small arterioles.
  • The process is the opposite of vasodilation, the widening of blood vessels.
  • Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large veins, large arteries, and smaller arterioles.
  • When blood vessels dilate, the flow of blood is increased due to a decrease in vascular resistance.