smooth

Examples of smooth in the following topics:

• Types of Muscle Tissue

  • There are three kinds of muscle tissue: skeletal, smooth, and cardiac.
  • Smooth muscle is named because it does not have any striations.
  • The individual smooth muscle fibers are spindle shaped and contain a centrally located nucleus.
  • Smooth muscle is found in the walls of the hollow organs.
  • Although cardiac muscle is involuntary in nature, it is structurally different from smooth muscle.

• Characteristics of Muscle Tissue

  • The three types of muscle tissue are skeletal, smooth, and cardiac.
  • Smooth muscle myocytes are spindle shaped with a single centrally located nucleus.
  • Cardiac and skeletal muscle are both striated in appearance, while smooth muscle is not.
  • Both cardiac and smooth muscle are involuntary while skeletal muscle is voluntary.
  • Differentiate among the structure and location of skeletal, smooth, and cardiac muscles

• Adrenergic Neurons and Receptors

  • Smooth muscle behavior is variable depending on anatomical location.
  • One important note is the differential effects of increased cAMP in smooth muscle compared to cardiac muscle.
  • Increased cAMP will promote relaxation in smooth muscle, while promoting increased contractility and pulse rate in cardiac muscle.
  • Specific actions of the α1 receptor mainly involve smooth muscle contraction.
  • Other areas of smooth muscle contraction are as follows:

• Local Regulation of Blood Flow

  • Blood flow is regulated locally in the arterioles and capillaries using smooth muscle contraction, hormones, oxygen, and changes in pH.
  • Blood flow is regulated by vasoconstriction or vasodilation of smooth muscle fibers in the walls of blood vessels, typically arterioles.
  • Arterioles contain smooth muscle fibers in their tunica media which allows for fine control of their diameter.
  • Local responses to stretch, carbon dioxide, pH, and oxygen also influence smooth muscle tone and thus vasoconstriction and vasodilation.

• Vascular Spasm

  • 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 vasoconstriction response is triggered by factors such as a direct injury to vascular smooth muscle, signaling molecules released by injured endothelial cells and activated platelets (such as thromboxane A2), and nervous system reflexes initiated by local pain receptors.
  • Smooth muscle in the vessel wall goes through intense contractions that constrict the vessel.
  • Blood vessel experiencing vasoconstriction as its smooth muscle contracts while the blood clot forms.

• Short-Term Chemical Control

  • The mechanism that leads to vasoconstriction results from the increased concentration of calcium (Ca2+ ions) and phosphorylated myosin within vascular smooth muscle cells.
  • 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.
  • Some physiologists have suggested it is the lack of oxygen itself which causes capillary beds to vasodilate by the smooth muscle hypoxia of the vessels in the region.
  • As with vasoconstriction vasodilation is modulated by calcium ion concentration and myosin phosphorylation within vascular smooth muscle cells.
  • Dephosphorylation by myosin light-chain phosphatase and induction of calcium symportersand antiporters that pump calcium ions out of the intracellular compartment both contribute to smooth muscle cell relaxation and therefore vasodilation.

• Lymphatic Vessel Structure

  • The next layer is smooth muscles that are arranged in a circular fashion around the endothelium which, by contracting and relaxing, which alters the pressure inside the lumen (space) inside the vessel.
  • The activity of smooth muscles allows lymph vessels to slowly pump lymph fluid through the body without needing a central pump or heart.
  • By contrast, the smooth muscles in blood vessels are instead involved in vasoconstriction and vasodilation instead of fluid pumping.
  • As they proceed forward and integrate into the larger lymph vessels, they take on adventitia, and smooth muscle.
  • Lymph fluid can only flow forward through lymphagions due to the closing of valves after fluid is pushed through by fluid accumulation, smooth muscle contraction, or skeletal muscle contraction.

• Esophagus

  • The esophageal tube in humans is comprised of two main layers of smooth muscle, though striated muscle comprises the tube near the pharynx.
  • The innermost layer of smooth muscle is arranged in a series of concentric rings, while the outermost layer is arranged longitudinally.
  • In much of the gastrointestinal tract, smooth muscles contract in sequence to produce a peristaltic wave which forces a ball of food (called a bolus) from the pharynx to the stomach.

• Overview of the Musculoskeletal System

  • These are skeletal, smooth, and cardiac muscle.
  • Only skeletal and smooth muscles are considered part of the musculoskeletal system.
  • Examples of smooth muscles include those found in intestinal and vessel walls.
  • Cardiac and smooth muscle are characterized by involuntary movement (not under conscious control).

• Orbits

  • The primary functions of the orbit include protection of its delicate contents and, through muscle attachment and a smooth coating fascia, to  also promote the smooth, delicate movements of the eye.