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Lecture

DEV2011: Lecture 26 summary

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Department
Medicine
Course Code
DEV2011
Professor
Various

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LECTURE 26 Blood: Blood is a bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. In vertebrates, it is composed of blood cells suspended in blood plasma. Functions of Blood: - Supply of oxygen to tissues (bound to hemoglobin, which is carried in red cells) - Supply of nutrients such as glucose, amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins (e.g., blood lipids)) - Removal of waste such as carbon dioxide, urea, and lactic acid - Immunological functions, including circulation of white blood cells, and detection of foreign material by antibodies - Coagulation, which is one part of the body's self-repair mechanism (blood clotting after an open wound in order to stop bleeding) - Messenger functions, including the transport of hormones and the signaling of tissue damage - Regulation of body pH - Regulation of core body temperature - Hydraulic functions Plasma: Plasma, which constitutes 55% of blood fluid, is mostly water (92% by volume), [1]and contains dissipated proteins, glucose, mineral ions, hormones, carbon dioxide (plasma being the main medium for excretory product transportation), and blood cells themselves. Albumin is the main protein in plasma, and it functions to regulate the colloidal osmotic pressure of blood. The blood cells are mainly red blood cells (also called RBCs or erythrocytes) and white blood cells, including leukocytes and platelets. Plasma also serves as the protein reserve of the human body. It plays a vital role in intravascular osmotic effect that keeps electrolyte in balance form and protects the body from infection and other blood disorders Red Blood Cells: The most abundant cells in vertebrate blood are red blood cells. These contain hemoglobin, an iron-containing protein, which facilitates transportation of oxygen by reversibly binding to this respiratory gas and greatly increasing its solubility in blood. In contrast, carbon dioxide is almost entirely transported extracellularly dissolved in plasma as bicarbonate ion. These cells' cytoplasm is rich in haemoglobin, an iron-containing biomolecule that can bind oxygen and is responsible for the blood's red color. The cell membrane is composed of proteins and lipids, and this structure provides properties essential for physiological cell function such as deformability and stability while traversing the circulatory system and specifically the capillary network. In humans, mature red blood cells are flexible and oval biconcave disks. They lack a cell nucleus and most organelles, in order to accommodate maximum space for haemoglobin. Platelets: Platelets are small, disk shaped clear cell fragments, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days. Platelets are a natural source of growth factors. They circulate in the blood of mammals and are involved in hemostasis, leading to the formation of blood clots. If the number of platelets is too low, excessive bleeding can occur. However, if the number of platelets is too high, blood clots can form (thrombosis), which may obstruct blood vessels and result in such events as a stroke, myocardial infarction, pulmonary embolism or the blockage of blood vessels to other parts of the body, such as the extremities of the arms or legs. Neutrophils: Neutrophil granulocytes are the most abundant type of white blood cells in mammals and form an essential part of the innate immune system. Neutrophils are a type of phagocyte and are normally found in the blood stream. During the beginning (acute) phase of inflammation, particularly as a result of bacterial infection, environmental exposure, and some cancers, neutrophils are one of the first-responders of inflammatory cells to migrate towards the site of inflammation. They migrate through the blood vessels, then through interstitial tissue, following chemical signals such as Interleukin-8 (IL-8), C5a, fMLP and Leukotriene B4 in a process called chemotaxis. They are the predominant cells in pus, accounting for its whitish/yellowish appearance. Neutrophils are recruited to the site of injury within minutes following trauma and are the hallmark of acute inflammation. Being highly motile, neutrophils quickly congregate at a f
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