The Circulatory System. Blood and Blood Pressure

Transcription

1 The Circulatory System Blood and Blood Pressure

2 Blood Total volume = 8-9% of body mass Average person = 5 L of blood DYK? Blood is actually a tissue! Plasma: - water, proteins, salts, gases, nutrients, urea, hormones, vitamins, etc. Formed Elements: (ratio) - RBC (600) - WBC (1) - Platelets (40)

3 A Drop of Blood: Contains ~: - 5 million RBC - 10,000 WBC - 250,000 platelets

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5 Haemopoiesis The Formation of Blood All blood cells originate from cells in the bone marrow called PLURIPOTENT stem cells In red bone marrow found in the long bones (ie. humerus and femur), flat bones (ribs and cranial bones), vertebrae, and pelvis, and joints.

6 White Blood Cells (WBC) AKA: Leukocytes Larger than RBC Fewer in # than RBC Lobed nucleus Lifespan = few hours to 14 days (only a few liver longer than this) Have amoeboid movement Spherical shape Colourless

7 White Blood Cells (WBC) Functions: 1. Fight infections 2. Phagocytize forgein particles 3. Develop immunity

8 White Blood Cells (WBC) Granulocytes: (granules in cytoplasm; phagocytic cells) 1. Neutrophils - phagocytic: ingesting bacteria and other pathogens - most common WBC 2. Basophils - contain heparin and histamines (increases blood flow to injured sites in body) - active participants in hypersensitivity reactions 3. Eosinophils - control of allergic and inflammatory response

9 White Blood Cells (WBC) Agranulocytes: (NO granules in cytoplasm; typically found in lymph tissue e.g. spleen) 1. Lymphocytes - produce antibodies and provide secondary immunity - B-cells (B-lymphocytes) - T-cells (T-lymphocytes) 2. Monocytes - largest WBC (become large MACROPHAGES) - phagocytize pathogens during infection

10 Immune Response Animation /student_view0/chapter22/ animation the_immune_response.html

11 Red Blood Cells (RBC) AKA. Erythrocytes - produced in red marrow - Lifespan = 120 days - Free floating - Contain Hemoglobin - RED in colour - Round; smaller than WBC - Lacks mitochondria - Nucleus dissolves as they mature (Anucleate) - Hence the biconcave shape! (cell collapses inward) - Nucleus is replaced with HEMOGLOBIN

12 Hemoglobin Protein composed of 4 polypeptide chains Each chain has a heme group containing IRON Heme group binds to oxygen and releases it into the tissues of the body If hemoglobin levels in blood DECREASE (anemia) body produces more erythropoietin (a hormone) This stimulates the # of RBC s produced in the bone marrow.

13 Function: Red Blood Cells (RBC) - Carries oxygen (oxyhemoglobin - HBO 2 ) - Carries carbon dioxide (carbaminohemoglobin HbCO 2 ) - Buffers blood by taking up excess H + Recall: How RBC s are Recyced of RBC s /student_view0/chapter19/ animation hemoglobin_breakdown.html

14 Thrombocytes (Platelets) - Small irregular cell fragments - Lack a nucleus Function: - form blood clots to prevent bleeding following tissue damage

15 Formation of a Blood Clot: 1. Platelets travel along the bloodstream ensuring all is well. 2. Platelets chemically change in reaction to an injury. 3. They become sticky and joining together at the site of the cut. (Clot would be white at this point). 4. Now that a white clot has formed, fibrin will join with the platelets at the clotting site to form a weblike structure. 5. RBCs catch on the sticky web of platelets and fibrin and become trapped. This is the formation of the final clot that effectively seals the cut so further bleeding is not possible.

16 Albumin A plasma protein Synthesized in the liver Functions: Maintain fluid balance in the blood (osmotic pressure) Role in maintaining blood pressure Regulates fatty acid, bilirubin and many drugs by acting as a transport protein Hormone transport (e.g. thryoxine) May act as a buffer

17 Human Blood Typing A-B-O system is a way of classifying blood according to ANTIGENS located on the RBC surface Antigens stimulate the production of antibodies Type A: Antigen on RBC: A Type B: Antigen on RBC: B Type AB: Antigen on RBC: A and B on each Type O: Antigen on RBC: neither (hence O) Blood type O is a universal donor! Blood type AB is a universal acceptor!

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21 Human Blood Typing Rhesus Factor (Rh factor) Another blood antigen 85% of N.Am. Population is Rh + meaning they have the Rh antigen If Rh + blood is given to someone that is Rh -, antibodies to the Rh antigen will react with the antigen and agglutination will occur.

22 Blood Pressure (P) P exerted by blood on the walls of BV. drops with distance from the heart due to the branching of blood vessels and the corresponding increase in X-sectional area. once P in the capillary beds drops, it cannot until the blood returns to the heart. low P in veins explains the importance of oneway valves and muscular movement to return blood to the heart

23 Blood Pressure Consider a blood pressure of 120/80. What do these numbers mean? mmHg = the systolic pressure 1. occurs during the contraction of the ventricles of the heart. 2. pressure at which the ventricles begin to force blood in the brachial artery past the arm cuff 2. 80mmHg = the diastolic pressure 1. occurs when the ventricles of the heart are relaxed. 2. pressure at which the blood in the brachial artery can move past the arm cuff continuously.

24 Blood Pressure Consider a blood pressure of 120/80. What do these numbers mean? 1. Hypertension Blood Pressure over 140/90. Causes: salty diet, hi sodium reabsorption, atherosclerosis and nerve activity that constricts blood vessel diameter 2. Hypotension VERY low blood pressure Problems with autonomic nervous system, trauma Fainting often occurs to compensate