Blood Composition & Blood Vessels - Biology Pre-lab PDF

**[Blood Pre-lab Reading: What is Blood?]** **[Blood Composition]** Blood is composed and solid elements. The solid elements are cells or cell fragments. The liquid portion of blood also has very important substances that help the body to function properly. The following illustration shows how the...

**[Blood Pre-lab Reading: What is Blood?]** **[Blood Composition]** Blood is composed and solid elements. The solid elements are cells or cell fragments. The liquid portion of blood also has very important substances that help the body to function properly. The following illustration shows how the liquid and solid parts of blood are separated by centrifugation (spinning tube of whole blood which causes the heavy solid parts to be collected at the bottom of the tube while the liquid part is the upper layer) The liquid part that is collected is called **Plasma.** Plasma must contain the correct amounts of solutes (dissolved substances to allow for it to maintain the correct osmotic composition to keep the blood functioning properly. For example, if the osmolality of the blood is too LOW, then the water (H2O) in blood will not easily be able to move into tissue where it is needed. Likewise, if the osmolality is too high, the water will easily leave the blood into tissues even if it is not needed there causing swelling in that tissue. **Plasma** composes about 55% of the total blood volume. Plasma is about 90% water. The remaining portion of plasma is made up of proteins, ions, glucose, amino acids, dissolved gases, and wastes. **Illustration of a blood sample (a) non-centrifuged (solids and liquids not separated) and (b) centrifuged.** **Plasma composition and its functions are shown in the following picture. You need to know these.** 1. **Water-** Solvent for carrying other substances. Absorbs heat. 2. **Salts-** Ionic solutes that are carried in blood and are important for many cellular functions. a. **sodium-** major cation outside of cells (important for establishing the resting membrane potential in neurons and muscle cells and it also maintains osmotic balance in cells and the blood by regulating blood volume and urine formation) b. **potassium-** important cation inside cells that works in reestablishing the resting membrane potential after depolarization in neurons and muscle cells c. **chloride-** the predominant extracellular anion and contributes to the osmotic pressure gradient between the ICF and ECF, and plays an important role in maintaining proper hydration. d. **magnesium-** needed for proper muscle, nerve, and enzyme function, as well as to maintain blood sugar and blood pressure levels. Magnesium is also essential for protein, bone, and DNA synthesis e. **calcium-** necessary for muscle contraction, enzyme activity, and blood coagulation. It helps to stabilize cell membranes and is essential for the release of neurotransmitters from neurons and of hormones from endocrine glands. It is stored in bone and teeth making them stronger. f. **bicarbonate**- the second most abundant anion in the blood and its main function is to maintain your body's acid-base balance by being part of buffer system 3. **Plasma proteins**- Proteins dissolved in blood. g. **Albumin-** Important for maintaining osmotic balance and viscosity. pH buffering (- charges act as H+ acceptors) h. **Fibrinogen-** Important for blood clotting. i. **Globulins**- Important for the defense of the body(antibodies) and lipid transport. 4. **Nutrients-** glucose, fatty acids, amino acids, vitamins 5. **Waste products-**metabolic waste products like urea, uric acid, lactic acid, and bilirubin. 6. **Respiratory gases-** oxygen and carbon dioxide 7. **Hormones-** endocrine hormone transport to target tissues **Formed Elements in Blood** The solid components of blood are known as formed elements, which account for about 45% of the total blood volume. Formed elements include **erythrocytes** (red blood cells), **leukocytes** (white blood cells), and **thrombocytes** (platelets). Red blood cells (RBCs) are by far the most numerous of the formed elements. There are approximately 4--6 million/mm^3^ RBCs; they outnumber white blood cells (WBCs) by about 600 to 1. The RBC to platelet ratio is approximately 16 to 1. Blood cell **morphology** (visual identification using, size, shape, and nuclear characteristics) is determined using a blood smear. This a process where blood is smeared on a glass slide after being treated with tissue stains to help us to detect blood cells that have nuclei. This process can be used to determine the numbers of different formed elements and whether they appear "normal". The identification of each blood cell type is important is medical pathology. **Red blood cells (RBC)** do not need to be stained because they contain a protein called hemoglobin (Hg). This is a very important protein from RBC function. It is the molecule that is coordinated with **iron (Fe**) and this complex blinds oxygen as blood passes through the lungs and carries it until it is delivered to tissues that need oxygen. In addition to its function the Hg appears red under the microscope which is hoe RBCs got their name. All other formed elements need staining to help to visualize them under the microscope. Specifically, the nuclei and some cytoplasmic structures are stained to aide identification of their structural features. The table below is summarizing their morphology identifying features, functions, relative size and relative numbers in normal states. For this lab, you will need to know how to identify each cell type, unique features, and functions. A close-up of a cell Description automatically generated Table of Types of Formed Elements 1. Red blood cells -- Transports oxygen on Hemoglobin and binds a limited amount of carbon dioxide. 2. Platelets- Megakaryocyte fragments that promote blood clotting 3. Granulocytes- Blood cells that contain dark staining granules in their cytoplasm. a. Neutrophil- release chemicals that recruit more leukocytes and they destroy bacteria by phagocytosis b. Eosinophil- Release chemicals to protect your body from infections by parasites (like worms), and fungi as well as allergens. c. Basophil-  Release histamine to improve blood flow to damaged tissue and heparin to prevent unwanted blood clots during infections. 4. Agranulocytes d. Monocyte- By turning into macrophages or dendritic cells when a pathogen enters your body it either kills the invader by phagocytosis or alert other blood cells to help destroy it and prevent infection. e. Lymphocytes i. T Lymphocyte- Control your body's immune system response and directly attack and kill infected cells and tumor cells.. ii. B Lymphocyte- make antibodies that target viruses, bacteria and other foreign invaders. Important for long-term immunity. Normal Blood Smear (1000x) showing different formed elements.  **Hematology** is the study of blood, blood-forming-tissues, and blood disorders. Blood disorders include any number of inherited or acquired disorders that affect one or more parts of the blood and prevent them from properly performing their job. Examples are shown below. Blood disorders can be chronic or acute and may or may not be curable. Many disorders can be identified by viewing a blood smears. Look at the following micrographs and compare them to the normal smears above. **[Abnormal Blood Clotting]** Hemostasis refers to the stopping of blood flow. Hemostasis consists of three steps: blood vessel spasm, platelet plug formation, and coagulation. Blood coagulation should only occur in response to injury. A healthy person's body has mechanisms in place to ensure that abnormal blood clots do not form spontaneously. An abnormal clot is called a **thrombus**. A clot that breaks away from the vessel wall and travels through blood vessels is referred to as an **embolus.** Any type of abnormal clot can be extremely dangerous because it can block flow to critical organs such as the brain, heart, and lungs. **[Blood Vessels: Structure and Function]** Blood vessels are a closed system of passages that transport blood around the body. 1. The heart pumps blood [away from the heart through a series of arteries]. 2. Arteries branch as they pass through organs and tissues to form progressively smaller vessels until they branch into [tiny capillary beds, where gas, nutrient, and waste exchange take place. ] 3. The blood is drained from the capillaries via a series of [veins that return the blood to the heart.] **[Structure of the different types of Blood Vessels]** Three distinct tissue layers make up the walls of arteries and veins. 1. **Tunica interna.** The innermost lining consists of a specialized type of [simple squamous epithelium called endothelium]. It rests on top of a thin layer of connective tissue called the [basal lamina]. 2. **Tunica media.** The middle layer of the blood vessel wall consists of [smooth muscle tissue] and [elastic fibers]. a. The smooth muscle, innervated by the sympathetic nervous system, controls the diameter of the vessel and plays an important role in regulating tissue perfusion and blood pressure. The elastic fibers allow the vessel to expand with changing pressure and return to its original diameter. 3. **Tunica externa.** The outermost layer consists of [dense irregular connective tissue with abundant collagen fibers.] The collagen fibers reinforce the blood vessel wall and prevent it from rupturing when the pressure in the vessel increases. A photomicrograph and anatomical model of the artery and vein. Artery and vein: (A) photomicrograph; (B) blood vessel structure, anatomical model photo. **The 3 types of blood vessels each have differences that are related to their functions.** 1. **Arteries** have a much thicker tunica media, with more smooth muscle and large elastic fibers that typically appear as wavy purple lines. a. They appear circular in cross sections because of their thick walls. b. Arteries closer to the heart are under high pressure and so have more elastic fibers in the tunica media and more collagen fibers in the tunica externa. c. Since arteries have more smooth muscle, diameter of their lumen (the inside of the blood vessel that carries the blood), is changed by stimulation from the sympathetic nervous system. This is an important mechanism for regulating blood flow to tissue and the blood pressure. i. Decreased diameter is caused by sympathetic stimulation which causes: 1. Decreased blood flow in the blood vessels (capillaries and veins) that are downstream of the blood flow. This decreased flow to the tissues served by these capillaries. 2. Decreased diameter of the artery lumen also increased the pressure inside that artery. a. This is because the amount of blood that is in the vessel is compressed, and it resists compression thus increasing the internal pressure of the vessel. d. Arteries branch as they carry blood further form the heart into smaller vessels called **arterioles.** e. Arterioles will continue branching until they are very small and no longer have the tunica media. These are the smallest vessels and are called **capillaries.** 2. Capillaries are extremely thin walled and consist only of a thin tunica interna with a basal lamina. f. The smallest capillaries are wide enough for only one red blood cell to fit through at a time. 3. **Veins** have a thin tunica media with few elastic fibers and [little smooth muscle]. Because the wall is so much thinner, the lumen is wider, and the vein typically is collapsed on the slide. **Atherosclerosis** The smooth lining of blood vessels usually discourages the accumulation of platelets and clotting factors. **Atherosclerosis** results when fatty deposits called plaque buildup in and on the vessel. **Plaque** consists of cholesterol, fatty substances, calcium, cellular waste, and fibrin (a clotting material). If plaque is exposed in the lumen, a clot may form. Anticoagulant drugs may be used to prevent clot formation or to dissolve existing clots. Some cells such as basophils and mast cells secrete heparin, an anticoagulant compound that works to prevent the formation of abnormal clots. If a blood vessel forms a plaque, then the blood flow through the lumen of the vessel is decreased. If the plaque becomes large enough, the flow can be completely blocked. This starves the tissues that are downstream from the occlusion of oxygen and nutrients. This can cause the tissue to be injured and sometimes die. Atherosclerosis is a disease that is the result of these plaques and atherosclerosis in the coronary arteries of the heart can lead to heart damage which is a heart attack. If not corrected quickly the damage to the heart muscle may be irreversible or even lethal.  Figure 19.5 Cross section of an artery showing atherosclerosis with thrombosis (20×).