Blood Vessels and Circulation Notes

  • Blood Vessel Layers: Tunica interna (endothelium), tunica media (smooth muscle), tunica externa (connective tissue). Blood vessels consist of three layers:

  • Types of Blood Vessels:

    • Arteries: Carry blood away from the heart; thick walls, internal elastic membrane.

    • Veins: Return blood to the heart; thin walls, lacking elastic membrane.

    • Lymphatics: Return lymph to the heart; very thin-walled with valves.

  • Blood Distribution: 15% in heart/lungs, 20% in brain/arteries/capillaries, 65% in skin/gut/liver/veins.

  • Control of Blood Flow:

    • Tunica Media: Vasoconstriction (decrease), vasodilation (increase).

    • Fight/Flight (Sympathetic): Muscle dilation, gut restriction.

    • Rest/Digest (Parasympathetic): Gut dilation.

  • Naming Blood Vessels: Arteries away, veins toward heart; named after bones/regions.

  • Arterial Supply of Limbs & Skin: Aorta supplies body wall; issues: arteriosclerosis, aneurysm, embolus/embolism, ischemia, infarction, CVA.

  • Venous Drainage of Limbs and Skin: Superficial/deep veins with valves; issues: varicose veins, hemorrhoids.

  • Circulation of the Head:

    • Arterial Supply: External carotid (skin/muscles), internal carotid/vertebral arteries (brain).

    • Arterial Circle (Circle of Willis): Anastomotic ring for brain supply.

    • Blood-Brain Barrier: Astrocytes/endothelial cells restrict permeability; exceptions in choroid plexus, hypothalamus, epithalamus.

    • Venous Drainage: Dural sinuses to internal jugular veins; brain stem to vertebral veins; scalp to external jugular vein.

  • Arterial Supply to Gut:

    • Celiac Trunk: Hepatic, left gastric, splenic arteries.

    • Superior Mesenteric Artery: Intestinal, right colic, middle colic arteries.

    • Inferior Mesenteric Artery: Left colic, sigmoidal, rectal arteries.

  • Hepatic Portal System: Liver receives blood from hepatic artery and portal vein, filters, drains to inferior vena cava. Veins: splenic, superior/inferior mesenteric.

  • Fetal Circulation: Placenta for exchange, umbilical cord attachment, shunts (foramen ovale, ductus arteriosus, ductus venosus).

  • Circulatory Changes at Birth: Loss of umbilical vessels, ductus arteriosus closes, lungs expand, foramen ovale closes.

  • Circulatory Problems at Birth: Foramen ovale/ductus arteriosus doesn't close ('blue baby'), coarctation of aorta.

  • Lymphatic System: Functions: lymphocyte production, interstitial fluid return, osmotic balance.

  • Lymphopoiesis: Lymphocyte production in bone marrow, thymus, lymphoid tissues.

  • Lymphatic System Components: Lymphoid organs, vessels, capillaries; lymph fluid.

  • Lymphatic Vessels: Larger than capillaries, valves ensure one-way flow; ducts drain to subclavian veins; edema = fluid accumulation.

  • Lymph Nodes: Filter lymph, remove antigens, contain macrophages.

  • Tonsils: Encircle respiratory/digestive openings; pharyngeal, palatine, lingual; identify pathogens.

  • Spleen: Largest lymphoid mass, removes abnormal cells, stores iron, initiates immune responses.

  • GALT: Immune response in GI tract; Peyer's patches.

  • MALT: Immune response in mucosal linings.