1 / 24

Structure of Blood Vessels

Structure of Blood Vessels. Composed of three layers (tunics) Tunica intima – composed of simple squamous epithelium Tunica media – sheets of smooth muscle Contraction – vasoconstriction Relaxation – vasodilation Tunica externa – composed of connective tissue Lumen

macario
Download Presentation

Structure of Blood Vessels

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Structure of Blood Vessels • Composed of three layers (tunics) • Tunica intima – composed of simple squamous epithelium • Tunica media – sheets of smooth muscle • Contraction – vasoconstriction • Relaxation – vasodilation • Tunica externa – composed of connective tissue • Lumen • Central blood-filled space of a vessel

  2. Structure of Arteries, Veins, and Capillaries

  3. Structure of Arteries, Veins, and Capillaries Figure 19.1a

  4. Types of Blood Vessels • Arteries – carry blood away from the heart • Capillaries – smallest blood vessels • The site of exchange of molecules between blood and tissue fluid • Veins – carry blood toward the heart

  5. Types of Arteries • Elastic arteries – the largest arteries • Diameters range from 2.5 cm to 1 cm • Includes the aorta and its major branches • Sometimes called conducting arteries • High elastin content dampens surge of blood pressure Figure 19.2a

  6. Types of Arteries • Muscular (distributing) arteries • Lie distal to elastic arteries • Diameters range from 1 cm to 0.3 mm • Includes most named arteries • Tunica media is thick • Unique features • Internal and external elastic laminae Figure 19.2b

  7. Types of Arteries • Arterioles • Smallest arteries • Diameters range from 0.3 mm to 10 µm • Larger arterioles possess all three tunics • Diameter of arterioles controlled by • Local factors in the tissues • Sympathetic nervous system Figure 19.2c

  8. Capillaries • Smallest blood vessels • Diameter from 8–10 µm • Red blood cells pass through single file • Site-specific functions of capillaries • Lungs – oxygen enters blood, carbon dioxide leaves • Small intestines – receive digested nutrients • Endocrine glands – pick up hormones • Kidneys – removal of nitrogenous wastes

  9. RBCs in a Capillary Figure 19.3

  10. Capillary Beds • Network of capillaries running through tissues • Precapillary sphincters • Regulate the flow of blood to tissues • Tendons and ligaments – poorly vascularized • Epithelia and cartilage – avascular • Receive nutrients from nearby CT

  11. Capillary Beds Figure 19.4a

  12. Capillary Beds Figure 19.4b

  13. Capillary Permeabillity • Endothelial cells – held together by tight junctions and desmosomes • Intercellular clefts – gaps of unjoined membrane • Small molecules can enter and exit • Two types of capillary • Continuous – most common • Fenestrated – have pores

  14. Structure of Capillaries – Cross Section Figure 19.5a

  15. Structure of Capillaries – Cross Section Figure 19.5b

  16. Routes of Capillary Permeability • Four routes into and out of capillaries • Direct diffusion • Through intercellular clefts • Through cytoplasmic vesicles • Through fenestrations

  17. Low Permeability Capillaries • Blood-brain barrier • Capillaries have complete tight junctions • No intercellular clefts are present • Vital molecules pass through • Highly selective transport mechanisms • Not a barrier against • Oxygen, carbon dioxide, and some anesthetics

  18. Sinusoids • Wide, leaky capillaries found in some organs • Usually fenestrated • Intercellular clefts are wide open • Occur in bone marrow and spleen • Sinusoids have a large diameter and twisted course

  19. Sinusoids Figure 19.5c

  20. Veins • Conduct blood from capillaries toward the heart • Blood pressure is much lower than in arteries • Smallest veins – called venules • Diameters from 8 – 100 µm • Smallest venules – called postcapillary venules • Venules join to form veins • Tunica externa is the thickest tunic in veins

  21. Mechanisms to Counteract Low Venous Pressure • Valvesin some veins • Particularly in limbs • Skeletal muscle pump • Muscles press against thin-walled veins Figure 19.6

  22. Vascular Anastomoses • Vessels interconnect to form vascular anastomoses • Organs receive blood from more than one arterial source • Neighboring arteries form arterial anastomoses • Provide collateral channels • Veins anastomose more frequently than arteries

  23. Vasa Vasorum • Tunica externa of large vessels have • Tiny arteries, capillaries, and veins • Vasa vasorum vessels of vessels • Nourish outer region of large vessels • Inner half of large vessels receive nutrients from luminal blood

  24. Pulmonary Circulation • Pulmonary trunk leaves the right ventricle • Divides into right and left pulmonary arteries • Superior and inferior pulmonary veins • Carry oxygenated blood into the left atrium

More Related