FINAL_LABS_BIOS255_Labs_BIOS_255_Week_3_Blood_Vessels_

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Apr 3, 2024

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BIOS255 Week 3 Cardiovascular System: Blood Vessels Learning objectives:  Identify the structural layers of arteries and veins.  Distinguish between the structure of arteries and veins.  Explain the factors that affect arterial blood flow and blood pressure.  Define shock, and identify the signs of shock.  Identify key blood vessels of the cardiac, systemic, and pulmonary circulations. Introduction: Blood is transported around the body in 3 different types of blood vessels: arteries, capillaries, and veins. Arteries and veins are each composed of 3 distinct layers of tissue while capillaries only have one layer. Blood pressure and flow depend on multiple factors. There are a number of mechanisms by which shock can occur. We will track blood through the pulmonary and systemic circulations noting the major arteries and veins along the path. Enjoy the interactive 3D models for exploring the blood vessels! Assignment: Part 1 Complete the activities in the following sections of Anatomy.TV Cardiovascular system : Blood vessels, Blood flow and Pressure, Circulatory Pathways, Vessels of the Trunk, Vessels of the Head and Neck, Vessels of the Limbs To access Anatomy.TV: Resources tab>Library>Library Resources-Database A- Z>Anatomy.TV>Titles(default tab): Choose Cardiovascular system>choose assigned sections You will then work through the material and activities by scrolling down on the right. This will allow you to see and work through all activities for that section. As you complete the lab activities, have the lab report ready to record data. Part 2 Complete the lab report

Blood vessel Lab report 1. Describe the different types of blood vessels by completing the following chart: (3 points total; 1/4 point per box) Blood vessel Histological description/special characteristics Function Large arteries Large arteries exhibit distinct internal and external elastic laminae, and their thick tunica media is abundant in elastic fibers (elastic lamellae). This feature enables their walls to stretch easily in response to increased blood pressure (high compliance), particularly during systole. Large arteries eject blood from the heart during ventricular diastole. Their elasticity is crucial for accommodating the volume of blood expelled during heart contractions. As these arteries stretch, elastic fibers store mechanical energy, which is later converted into kinetic energy as the elastic fibers recoil, propelling blood away from the heart. Medium arteries Medium arteries have distinct internal elastic laminar but thin external ones. The tunica media, which varies in size, contains 3-40 layers of smooth muscle cells. The tunica externa is often thicker than the media, with longitudinally oriented fibroblasts, collagen, and elastic fibers, allowing arteries to change their diameter. Muscular arteries lack elastic fibers, so they don’t recoil like elastic arteries. Instead, smooth muscle cells maintain partial contraction (vascular tone) to sustain vessel pressure and efficient blood flow. This allows for the effective adjustment of blood flow rate through vasoconstriction and vasodilation. Arterioles Arterioles, also called resistance vessels, are tiny arteries that bring blood to capillary networks. Their diameter ranges from 15-300 µm, and the wall thickness is about half the The sympathetic nerves in arterioles control blood flow by causing either narrowing (vasoconstriction) or widening (vasodilation).

total diameter. The thin tunica interna has a porous internal elastic lamina, and as the arteriole narrows towards its end, it becomes a capillary, known as the metarteriole. The muscular tunica media consists of one to two layers of smooth muscle cells, and a smooth muscle cell at the junction acts as a precapillary sphincter, controlling blood flow between the metarteriole and its adjacent capillary. The tunica externa has unmyelinated sympathetic nerves and loose connective tissue. Smaller vessel diameter increases resistance and slows down blood flow. Capillaries Capillaries, small and interconnected vessels, create networks throughout the body, connecting arterioles and venules. They lack tunica media and tunica externa, with a thin, single- layered epithelial structure enabling swift exchange of small molecules like glucose and gases like oxygen and carbon dioxide between blood and interstitial fluid. They are also known as exchange vessels and typically range from 5-10 µm. Due to their small size, red blood cells, which are 8 µm in diameter, need to fold to fit through these capillaries. The capillary wall is about 0.2 micrometers thick, consisting of a single layer of endothelial cells attached to a basement membrane. Capillary networks cover a lot of space and touch many tissues in the body Medium veins Medium veins are around 1cm in diameter. They possess the typical three-layer structure, have a thick outer layer (tunica externa) of collagen and elastic fibers, and a thin middle layer (tunica media) without smooth muscle. Lacking internal or elastic laminar, they can’t handle high pressure. These veins rely on skeletal muscle contraction and the heart’s pumping for venous return, often featuring valves in the tunica interna to prevent backflow. The valves function to boost venous return by preventing back flow of blood due to gravity

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