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Cardiovascular System. Vessels and Circulation. Vessels and Circulation. Two groups of blood vessels PULMONARY SYSTEMIC Closed system Begins and ends at the heart Major types of vessels ARTERIES CAPILLARIES VEINS. Size and Direction.

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cardiovascular system

Cardiovascular System

Vessels and Circulation

vessels and circulation
Vessels and Circulation
  • Two groups of blood vessels
  • Closed system
  • Begins and ends at the heart
  • Major types of vessels
    • VEINS
size and direction
Size and Direction
  • Blood moves through arteries that get progressively smaller
  • Blood moves through veins that get progressively larger
  • Arteries → Arterioles → Capillaries → Venules → Veins → largest veins superior and inferior vena cava
  • Arteries carry blood AWAY from the heart
  • Veins carry blood TOWARD the heart
histology of blood vessels
Histology of Blood Vessels
  • Three layers
  • 1. Tunica intima – endothelial layer and CT
  • 2. Tunica media – smooth muscle layer
  • 3. Tunica externa – CT sheath around the vessel
how to tell an artery from a vein
How to tell an artery from a vein
  • Tunica media is thicker in arteries
  • In sections arteries will appear round, the veins tend to collapse
  • Endothelial layer of arteries often has a pleated appearance
types of arteries
Types of arteries
    • Large vessels
    • Transport large volumes of blood
    • Elastic fibers in the tunica media to tolerate blood pressure
    • Aortic trunk, common carotid, subclavian, common iliac
    • Transport blood to muscles and organs
    • Fewer elastic fibers, more smooth muscle
    • External carotids, brachials, femorals, mesenterics
    • Smaller diameter, little tunica media or tunica externa
    • Control flow of blood between arteries and capillaries
  • Very small diameter – just larger than the diameter of a red blood cell
  • Exchange between the blood and surrounding tissues
  • Capillary density directly related to the metabolic activity of its cells
    • Tissues with higher metabolic rates have more capillaries per unit area
  • A capillary is just an endothelial layer of simple squamous cells and CT
  • Capillary beds form the functional basis of the cardiovascular system
  • Human body is estimated to have about 50,000 miles of capillaries with a total exchange area of 6300 square meters – two football fields!
  • Veins collect blood from all the tissues and return it to the heart
  • High volume vessels – hold 60% of the circulating blood
  • Veins have thinner walls and very little elastic fibers
  • Venules are small veins that collect blood from the capillaries
  • Medium size veins
  • Large veins
  • Veins have valves to prevent backflow of blood
pulmonary circuit
Pulmonary circuit
  • Pulmonary arteries carry blood AWAY from the heart to the lungs
  • This blood is low in oxygen, high in carbon dioxide
  • Pulmonary veins carry blood BACK to the heart
  • This blood is high in oxygen and will be sent out to the body tissues through the systemic circuit
hepatic portal system
Hepatic Portal System
  • System of TWO capillary beds
  • Digested material is absorbed from the digestive system by one capillary bed
  • Goes to the liver for processing in a second capillary bed
  • Blood returns to venous circulation via the hepatic vein to the inferior vena cava
  • Hepatic portal vein is formed from the
    • Superior mesenteric vein
    • Inferior mesenteric vein
    • Splenic vein
fetal circulation
Fetal Circulation
  • Short circuits that bypass fetal lungs
  • Foramen ovale (fossa ovalis)
  • Ductus arteriosus (ligamentum arteriosum)
  • Both of these bypass circuits seal up at birth when the lungs become functional