digestive and lymphatic

• The mammalian circulatory system is a closed system of tubes with an endothelial lining from the heart through the arteries into the capillaries and back through the veins
• The circulatory system consists of organs and structures which pump, transport, and distribute oxygen, nutrients and hormones to the different cells and tissues of the body and collect from them carbon dioxide and the waste products of metabolism
• The circulating or peripheral blood is the mode of transportation of the substances and gases in the cardiovascular system
• Components of the cardiovascular system

  • Heart
  • Pulmonary circulation
  • Systemic circulation
• Types of blood vessels according to caliber (strength)

  • Arteries
  • Capillaries
  • Veins
  • Lymphatic vessels
• Arteries


  Blood vessels that carry blood away from the heart to the capillaries
• Capillaries


  Site of exchange of nutrients and waste products of metabolism as well as oxygen and carbon dioxide between the vascular bed and the surrounding tissues
• Veins


  Blood vessels that return the blood from the tissues to the heart
• Lymphatic vessels

  Blood vessels that return extracellular or tissue fluid as lymph to the cardiovascular system
• Factors affecting the size of the Lumen of the Blood Vessel walls

  • Velocity of the blood moving through the blood vessels
  • Pressure with which blood is being propelled
  • Volume of the blood being moved
• Faster blood velocity


  Thicker wall and smaller lumen of the blood vessel
• Slower blood velocity


  Thinner wall and bigger lumen of the blood vessel
• Higher blood pressure


  Thicker wall and smaller lumen of the vessels
• Higher blood volume


  Larger lumen and thinner wall of the blood vessels
• Lower blood volume


  Thicker wall and smaller lumen of the blood vessels
• The arterial side of circulation carries a low volume of blood under high pressure at a high velocity
• The capillary system carries a large volume of blood under an appreciably diminished pressure and velocity
• Layers of the blood and lymphatic vessel walls

  • Tunica intima
  • Tunica media
  • Tunica adventitia
• Tunica intima


  Innermost layer which faces the lumen of the blood vessel
• Components of the tunica intima


  • Endothelium
  • Sub-endothelial coat
  • Elastica interna
• Endothelium


  Simple squamous epithelium which lines the blood and lymphatic vessels and rests on a basal lamina
• Sub-endothelial coat


  Thin layer of loose connective tissue located under the endothelium
• Elastica interna


  Thin condensation of elastic fibers that has a wavy appearance and functions in separating the tunica intima from the tunica media
• Tunica media


  Middle layer of blood and lymph vessels consisting of a mixture of smooth muscle fibers, collagenous and elastic fibers, and fibroblast
• Components of the tunica media

  • Muscular/medium arteries
  • Large/elastic arteries
  • Vaso vasorum
  • Nervi vasorum
  • Elastica externa
• Muscular/medium arteries


  Smooth muscle fibers predominate the tunica media
• Large/elastic arteries


  Elastic fibers predominate the tunica media
• Vaso vasorum


  Tiny blood vessels
• Nervi vasorum


  Nerve fibers
• Elastica externa


  Separates the tunica media from the tunica adventitia
• Tunica adventitia


  Consists of the external elastic lamina or elastica externa and dense fibroelastic connective tissue
• Types of blood and lymphatic vessels

  • Capillaries
  • Arteries
  • Veins
  • Lymphatic vessels
• Capillaries


  Smallest type of blood vessels characterized by a very thin wall consisting only of the endothelium resting on a basal lamina
• Types of capillaries


  • Continuous capillaries
  • Fenestrated capillaries
• Continuous capillaries


  Capillaries characterized by the absence of interruptions in the cell membrane of the endothelial lining cells
• Fenestrated capillaries


  Capillaries characterized by the presence of pores in the endothelial lining which may be covered by a diaphragm
• Sinusoids


  Very large and irregularly shaped capillary-like structures lined by both phagocytic and non-phagocytic cells
• Sinuses


  Similar to sinusoids but are lined only by non-phagocytic cells
• Types of arteries


  • Arterioles
  • Muscular or distributing arteries
  • Elastic or large arteries
• Arterioles


  Very small arteries with special construction, having relatively narrow lumens and relatively thick walls