Summary - Cardiovascular PDF

Summary - Cardiovascular Tuesday, November 26, 2024 7:28 PM Layers of the heart :...

Summary - Cardiovascular Tuesday, November 26, 2024 7:28 PM Layers of the heart : Endocardium Location: Innermost layer of the heart wall ( lines chambers/valves ) Structure: Thin layer of endothelial cells (simple squamous epithelium). Supported by a thin layer of connective tissue and subendocardial layer containing small blood vessels, nerves, and Purkinje fibers (involved in conducting electrical signals in the heart). It's rich in collagen fibers Myocardium Location: Middle and thickest layer of the heart wall. Structure: Made primarily of cardiac muscle tissue, which is striated, branched, and involuntary. Contains specialized cells like cardiomyocytes and a network of blood vessels and nerves. Epicardium Location: Outermost layer of the heart wall. Structure: A thin layer of connective tissue covered by mesothelium (simple squamous epithelium), part of the visceral layer of the serous pericardium. Contains adipose tissues , blood vessels, and nerves supplying the heart. AV shunts are direct connections between an artery and a vein that bypass the capillary bed. They allow blood to flow directly from the arterial system to the venous system without passing through capillaries. A venous portal system refers to a network where blood passes through two sequential capillary beds before returning to the heart The lymphatic system is essential for: Returning excess interstitial fluid to the bloodstream. Histological Features of Vascular Circulation Preventing tissue swelling (edema). Filtering and immune surveillance. 1. Arteries (e.g., aorta): ○ Tunica intima: Endothelium and subendothelial layer. ○ Tunica media: Thick, containing smooth muscle and elastic fibers and collagen The thoracic duct and right lymphatic duct connect the lymphatic and circulatory systems, ○ Tunica adventitia: Outer connective tissue with vasa vasorum (small vessels supplying larger arteries). ensuring lymph eventually rejoins the bloodstream near the heart. 2. Veins: ○ Thinner tunica media compared to arteries. Lymphatic vessels contain one-way valves that ensure lymph flows in one direction, preventing ○ Larger lumens with valves to prevent backflow. backflow. ○ Prominent tunica adventitia with connective tissue. 3. Capillaries: ○ Composed of a single endothelial layer with a thin basement membrane. Formation of Lymph ○ Types: § Continuous (tight control of permeability). Interstitial Fluid: This is the fluid that surrounds cells in tissues. It originates from blood plasma § Fenestrated (increased permeability for filtration). that leaks out of capillaries during nutrient and gas exchange. § Sinusoidal (large openings for exchange in liver, spleen, and bone marrow). ↠A portion of this fluid is not reabsorbed by venules (due to colloidal osmotic pressure). Lymph Formation: This excess interstitial fluid enters lymphatic capillaries and is called lymph. Lymphatic Capillaries: ↠These are blind-ended vessels (closed at one end). ↠They have thin endothelial cell walls with gaps between cells, allowing interstitial fluid, proteins, and waste products to enter.