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Lecture 11

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Biological Sciences
Connie Potroff

1 Lecture 11 The Cardiovascular System: Heart and Blood **Assigned Readings: p.580 (fig 22.9) + p.593 (fig 22.20) –responsible for ALL ARTERIES/VEINS in the diagrams!!!! Introduction • The cardiovascular system functions as a system to transport numerous substances throughout the body such as: nutrients, oxygen and carbon dioxide, hormones and ions  Transports metabolic wastes to the kidneys  Transports leukocytes to aid in fighting infectious agents Composition of the Blood • Whole blood 4-6 liters • Blood consists of two components  Plasma - liquid matrix of blood  Formed elements: blood cells and cell fragments that are suspended in the plasma, and include:  Erythrocytes (red blood cells): transport oxygen and carbon dioxide  Leukocytes (white blood cells): function in the immune system  Platelets: involved in blood clotting • Plasma - makes up about 55% of the volume of whole blood  Consists of: 92% water 7% proteins (albumin, globulins, fibrinogen, regulatory proteins) 1% other solutes (electrolytes, organic nutrients, organic waste) • Plasma proteins: there are three major classes of protein in the blood  60% Albumin – contributes to the osmotic pressure, transports fatty acids and steroids, smallest of the proteins  35% Globulins - act as immunoglobulins (antibodies) and act as transport proteins (transport ions and hormones)  4% Fibrinogen - involved in blood clotting, largest of the proteins • Formed elements - makes up about 45% of whole blood  Platelets (<0.1% of formed elements)  Leukocytes (White Blood Cells WBC) (<0.1% of formed elements)  Neutrophils (50–70% of the WBCs)  Eosinophils (2–4% of the WBCs)  Basophils (<1% of the WBCs)  Lymphocytes (20–30% of the WBCs)  Monocytes (2–8% of the WBCs)  Erythrocytes (Red Blood Cells RBC) (99.9% of formed elements) • Red Blood Cells (RBCs) or Erythrocytes Structure of RBCs  Biconcave disc  Thin central region  Measure about 7.7 microns in diameter  Lack cell organelles  Lack a nucleus (anucleated) 2 RBC Life Span  Since RBCs lack a nucleus and all the organelles, have a life span of about 120 days  Significance of a lack of a nucleus:  Allows the cell to be flexible as it travels through the circulatory system  Allows for more room for hemoglobin  Significance of a lack of mitochondria:  Mitochondria use oxygen to manufacture ATP  Without mitochondria, oxygen can be transported to the tissues instead of being “used” by the mitochondria RBCs and Hemoglobin  A developing erythrocyte loses its nucleus and organelles  A mature erythrocyte is mainly a cell membrane surrounding water and protein o The water accounts for 66% of the RBC’s volume o The protein accounts for 33% of the RBC’s volume of which >95% is hemoglobin o Hemoglobin is responsible for transporting oxygen and carbon dioxide (the main function of RBCs) Life Cycle of RBC - finite lifespan of 120 days since no nucleus or cellular organs to repair itself or replace damaged membrane regions – then phagocytized in spleen and stored in liver - molecular components are broken down and recycled or eliminated from the body - when RBC destroyed by macrophage in spleen, hemoglobin is recycled into heme and globin - **heme – the iron portion is transported in the blood by the protein transferrin and stored by the protein ferritin in the liver; the non-iron portion of heme gets converted into biliverdin and then to bilirubin in the liver and is converted to pigments that are part of feces - **globin is broken down into amino acids, some of which are used to make new RBCs Hemoglobin  Consists of four polypeptide subunits  Each subunit contains a molecule of heme  Heme is a porphyrin ring  Each heme consists of an iron ion o Iron binds to oxygen o The polypeptide units bind to carbon dioxide o Oxygen and carbon dioxide do not compete with each other for binding sites • Leukocytes or White Blood Cells (WBCs)  There are two major classes of leukocytes consisting of a total of five types of leukocytes o Granulocytes: neutrophils, eosinophils, basophils o Agranulocytes: monocytes, lymphocytes  WBCs have a short life span (usually a few days)  When the body is compromised, the white blood cells multiply to combat the invading agent or allergen, etc. o Granulocytes 3 • Neutrophils (normal range is 50–70%) • Granules contain chemicals to kill bacteria • Typically the first WBC at the bacterial site • Very active phagocytic cells • Nucleus is multi-lobed • **Eosinophils (normal range is 2–4%) • Granules release chemicals that reduce inflammation • Attack a foreign substance that has reacted with circulating antibodies (such as an allergic reaction or parasites) • Typically have a bilobed nucleus • **Basophils (normal range less than 1%) • Granules release histamine and heparin • Histamine dilates blood vessels • **Heparin prevents abnormal blood clotting • Nucleus is usually hidden due to all the granules o Agranulocytes  **Monocytes (normal range is 2–8%)  start as precursor cells in the blood and exit blood vessels move into tissues where they then differentiate into macrophages (clean up debris, eat damaged tissue, engulf bacteria, dead cells etc.) • Large phagocytic cells • Release chemicals to attract other phagocytic cells • Release chemicals to attract fibroblasts • Fibroblasts produce collagen fibers to surround an infected site • These collagen fibers can produce scar tissue • Nucleus is kidney-shaped or large oval-shaped  Lymphocytes (normal range is 20–30%) • Responsible for specific immunity • Can differentiate to form T cells, B cells, and NK cells • Nucleus is typically large and round leaving a small halo around the entire nucleus or part of it  T cells - attack foreign cells directly  B cells - antibodies to
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