Anatomy

• Vascular system


  A closed system of vessels that transports blood to and from the lungs and body tissues

  
• Types of blood vessels

  • Venules
  • Veins
  • Arteries
  • Arterioles
  • Capillaries

  
• Blood vessels


  • Subdivided into two circuits: Pulmonary circuit (carry blood to the lungs) and Systemic circuit (supply the rest of the body)

  
• Arteries


  Carry blood away from the heart and toward the capillaries in the tissues

  
• Arterioles


  Smallest arteries
• Capillaries


  Allow for exchanges between the blood and body cells, or between the blood and airsacs in the lung tissues; Connect the arterioles and venules

  
• Venules


  Smallest veins; Receive blood from the capillaries of the tissue area and return it to the heart

  
• Veins


  Vessels formed from venules merging; Carry blood towards the heart

  
• Pulmonary circuit


  1. Eliminates carbon dioxide from the blood

  2. Replenishes its supply of oxygen
• Components of pulmonary circuit


  • Pulmonary arteries trunk and its branches (towards the lungs, low in oxygen)
  • Capillaries in lungs (gases, nutrients & waste are exchanged, becomes oxygenated)
  • Pulmonary veins (back to the heart, high in oxygen)

  
• Systemic circuit


  Carries nutrients and oxygen to rest of the body
• Components of systemic circuit

  • Aorta (receives freshly oxygenated blood)
  • Systemic arteries (carries oxygenated blood to tissues)
  • Systemic capillaries (exchange of materials, loss of oxygen)
  • Systemic veins (back to the heart, low in oxygen)

  
• Oxygen content changes as blood flows through the capillaries

  
• Pulmonary arteries and systemic veins contain oxygen-poor blood. Pulmonary veins and systemic arteries contain oxygen-rich blood.

  
• Arteries and veins


  • Have three layers ('tunics'): Inner (simple squamous epithelial cells/endothelium), Middle (smooth muscle, involuntary contractions controlled by autonomic nervous system), Outer (supporting connective tissue)

  
• Veins


  Have valves that control blood flow

  
• Arterioles


  • Have thinner walls that are less elastic but have more smooth muscle; Smooth muscle regulates the amount of blood entering various tissues at one time by contracting (constricting) or relaxing (dilating)
• Capillaries


  Have the thinnest walls of any vessels: one cell layer; Some only allow one red blood cell through at a time; Transparent; Smooth, plate-like cells (endothelium)
• Capillaries are so thin to allow for exchanges between the blood and the body (somatic) cells & between the alveoli in the lungs and blood

  
• Blood vessel structure and function

  • Arteries (Three tunics, carry blood away from heart, systemic arteries high in oxygen, pulmonary/umbilical arteries low in oxygen)
  • Veins (Three tunics, thinner walls, carry blood to heart, systemic veins low in oxygen, pulmonary/umbilical veins high in oxygen)
  • Capillaries (Single layer endothelium, exchange of gases, nutrients & waste)
  • Arterioles (More muscle, less connective/elastic, link arteries and capillaries, control blood pressure and distribution)
  • Venules (Intermediate between capillaries and veins, link capillaries & veins)

  
• Parts of the aorta

  • Ascending aorta
  • Aortic arch
  • Thoracic aorta
  • Abdominal aorta

  
• Branches of the ascending aorta and aortic arch

  • Left and right coronary arteries (supply heart muscle)
  • Brachiocephalic artery (right subclavian, right common carotid)
  • Left common carotid artery
  • Left subclavian artery

  
• Branches of the thoracic aorta

  • Intercostal arteries (reach muscles of chest walls)
  • Superior phrenic artery

  
• Branches of the abdominal aorta

  • Celiac trunk (left gastric, splenic, hepatic)
  • Superior and inferior mesenteric (small and large intestine)
  • Inferior phrenic (diaphragm)
  • Renal (kidneys)
  • Gonadal (ovaries/testes)
  • Lumbar (muscles of abdomen)

  
• There is one brachiocephalic artery
• Branches of the abdominal aorta

  • Common iliac arteries
  • Internal iliac arteries (pelvic organs)
  • External iliac arteries (continue into thigh as femoral artery)

  
• Arteries that branch to the arm and head

  • External carotid artery (thyroid gland, face, neck, scalp)
  • Internal carotid artery (eye, part of brain)
  • Vertebral artery (posterior of brain)
  • Axillary artery (armpit and upper limb)
  • Brachial artery (longest part of axillary, subdivides into radial and ulnar)

  
• Anastomoses


  Communication/connection between two vessels, allows vital organs to receive blood by more than one route

  
• Examples of anastomoses


  • Cerebral arterial circle (circle of Willis)
  • Superficial palmar arch
  • Mesenteric arches
  • Arterial arches (foot)

  
• Superficial veins


  Found near the surface, located in the extremities
• Deep veins


  Tend to parallel arteries & usually have the same names as the corresponding arteries
• Examples of deep veins

  • Femoral and iliac vessels
  • Brachial, axillary, subclavian vessels
  • Jugular veins
  • Brachiocephalic veins
• Components of the superior vena cava

  • Union of the right & left brachiocephalic veins
  • Veins of head, neck, arms and chest drain into it
  • Azigos vein (drains veins of chest wall)

  
• Components of the inferior vena cava

  • Paired veins from structures & organs (diaphragm, kidneys, gonads etc)
  • Unpaired veins from the spleen & digestive tract (stomach & intestine, empties into hepatic portal vein)
• Hepatic portal system


  Includes veins that carry blood from abdominal organs to the liver, allows products from one organ to pass directly to another organ
• Tributaries of the hepatic portal system

  • Superior mesenteric vein (largest)
  • Splenic vein
  • Gastric, pancreatic, inferior mesenteric veins

  
• Cava


  Union of the right & left brachiocephalic veins
• Veins that drain into the cava


  • Veins of head, neck, arms and chest
• Azigos vein


  Drains veins of chest wall & empties into superior vena cava
• Inferior vena cava


  Returns blood from areas below the diaphragm, beginning in the lower abdomen and includes the lower extremities