Blood Composition and Vessels PDF

Blood composition: Blood is made up of 55% plasma and 45% formed elements. The plasma makes up 55% of the blood: The plasma is made up of 91% water. The plasma also contains 7% proteins. The proteins contained in the plasma are 58% albumin, 38% globulins, 4% fibrinogen. The plasma contains other sol...

Blood composition: Blood is made up of 55% plasma and 45% formed elements. The plasma makes up 55% of the blood: The plasma is made up of 91% water. The plasma also contains 7% proteins. The proteins contained in the plasma are 58% albumin, 38% globulins, 4% fibrinogen. The plasma contains other solutes: ions, nutrients, waste products, gases, and regulatory substances. The formed elements make up 45% of the blood : The formed elements are platelets, white blood cells and red blood cells. Red blood cells make up the majority of the formed elements (4.2-6.2 million). The white blood cells in the formed elements are neutrophils (60-70%), lymphocytes (20-25%), monocytes (3-8%), eosinophils (2-4%) and basophils (0.5-1%). Erythrocytes - Cells in the blood: Erythrocytes are also called Red Blood cells (RBC) Red blood cells are Biconcave disc - shaped Red blood cells are 7.5 µm non-nucleated Red blood cells contain no organelles Red blood cells contain haemoglobin (Hb), a pigmented protein Red blood cells carry oxygen from the lungs to tissues. 1.5% of the oxygen is dissolved in plasma & 98.5% of the oxygen is attached to the haemoglobin protein. Red blood cells carry carbon dioxide from tissues to the lungs. 7% of the carbon dioxide is transported in plasma, 23% is attached to the haemoglobin protein, and 70% is transported as bicarbonate. Leukocytes - Cells in the blood: Leukocytes are also known as White blood cells (WBC) White blood cells are complete cells, nuclei & organelles. There are various types of WBC: e.g. neutrophils, lymphocytes, monocytes, eosinophils, basophils White blood cells mainly help in protection - phagocytosis, immune response ( both cell – mediated and antibody - mediated), white blood cells develop into macrophages, release histamines etc. Blood vessels are the arteries, the veins and the capillaries: Arteries: Arteries take blood away from the heart Arteries contain blood under pressure Arteries are elastic, and muscular, and contain arterioles. Arterioles are very small blood vessels that branch off from arteries and carry blood to the tissues and organs by linking with capillaries. Veins: Veins take blood to the heart The blood in the veins is not under pressure Veins have thinner walls than arteries. Vein walls contain less elastic tissue and less smooth muscle. Veins have venules of various sizes i.e. small, medium, large Capillaries: The capillaries are the site of exchange with tissues (interstitial fluid). The capillaries are the smallest of the three blood vessel types. The capillary wall consists of endothelial cells (simple squamous epithelium), a basement membrane and a delicate layer of loose C.T. There are three types of capillaries: continuous capillaries, fenestrated capillaries and sinusoidal capillaries. Continuous: are the least permeable capillaries type. No gaps between endothelial cells, less permeable to large molecules than other capillary types. Continuous capillaries are found in muscle and nervous tissue. Fenestrated: fenestrated capillaries have pores in endothelial cells called fenestrae. Fenestrated capillaries are highly permeable. Fenestrated capillaries are found in the intestinal villi and glomeruli of the kidney. Sinusoidal. Sinusoidal capillaries have a large diameter, and an irregular incomplete wall of endothelial cells. Sinusoidal capillaries have less basement membrane. Sinusoidal capillaries are found in endocrine glands, and liver (large molecules cross their walls). Blood vessels histology: Tunica intima (interna): is made up of Endothelium, has a basement membrane, lamina propria, Elastic tissue Tunica media: made up of smooth muscle cells and elastin arranged circularly. The smooth muscle changes the diameter of the lumen. The elastic tissue allows distension and recoil. During vasoconstriction, the smooth muscles contract causing a decrease in blood flow. In Vasodilation, the smooth muscles relax causing an increase in blood flow. Tunica externa (adventitia): is made up of connective tissue (CT), transitions from dense connective tissue to loose connective tissue as it merges with surrounding tissue.