Aims Lymphatics. Blood composition Blood clotting Readings; Sherwood, Chapter 10 & 11; Robbins, pages 84-90

Sherwood’s Human Physiology ( th Edition) Lymphatics Carry proteins and large particles out of tissues. 1/10 of fluid that leaves the capillaries enter the lymphatics. Lymph fluid is derived from excess interstitial fluid.

Sherwood’s Human Physiology ( th Edition) Lymphatic Capillary Valves –Overlap of the endothelial cells allow for large particles to enter lymphatics. –High pressure inside the lymph vessel will seal it.

Lymph Flow Interstitial fluid pressure –Increase in Interstitial fluid pressure => ____________ lymph flow. Lymphatic Pump –Smooth muscle cells around the lymph vessels contract in response to stretch (primary force) –Contraction of skeletal muscle (secondary force) –Internal valves function similar to veins to prevent backflow.

Guyton’s Textbook of Medical Physiology Lymph Flow Lymph flow increases as the interstitial pressure increases. Plateau is due to the compression of larger lymphatic vessels.

Sherwood’s Human Physiology ( th Edition) Lymphatic System Main Functions Return excess filtered fluid. Defense against disease. Transport of absorbed fat. Return of filtered protein.

Sherwood’s Human Physiology ( th Edition) Edema Accumulation of _____________________ fluid. Reduced conc. of plasma proteins. –Decreased colloid pressure Increased capillary permeability. Increased venous pressure. Blockage of lymph vessels.

Sherwood’s Human Physiology Table 11-1 Blood Composition Plasma is the non-cellular portion. –Water –electrolytes –proteins

Sherwood’s Human Physiology Table 11-1 Blood Composition Cellular portion –leukocytes –erythrocytes –platelets

Sherwood’s Human Physiology 11-1 Blood Composition Separate blood by centrifugation Plasma is the liquid top portion. –55% Cellular portion is the bottom half. –“Buffy coat” leukocytes platelets

Blood Plasma Water –Transport medium. –Carries heat. Electrolytes –Ions necessary for membrane potential regulation (Na +, K +, etc.). –pH buffer. –Osmosis regulation between outside and inside cells. Proteins –Transportation (Albumin). –Blood clotting (Fibrinogen). –Immunity (Ig). –Colloid osmotic pressure

Blood Cells Leukocytes –___________________. Erythrocytes –Transport O 2 and some CO 2. Platelets –Plugging and clotting.

Sherwood’s Human Physiology 11-2 Erythrocytes (RBCs) Functions –Transport hemoglobin (which carries O 2 ). –Convert CO 2 to bicarbonate ion (HCO 3 - ) via carbonic anhydrase. –Acid-base buffering.

Sherwood’s Human Physiology 11-3 Hemoglobin A Most common form 4 subunits –2  peptides –2  peptides –each contain a _________________ group which has an iron atom. –The iron atom interacts with two oxygen atoms (one oxygen molecule).

Guyton’s Textbook of Medical Physiology 32-1 Location of Erythrocyte Production After birth the bone marrow is the source of erythrocytes. Initially, the bone marrow of every bone produces erythrocytes, with time that is narrowed to membranous bones.

Guyton’s Textbook of Medical Physiology 32-4 Erythropoiesis Production of erythrocytes Erythropoietin –circulating hormone –90% by ________________ –10% by liver –Mediates hypoxia induced erythrocyte production

Sherwood’s Human Physiology 11-4 Regulation of Erythropoiesis Decreased blood oxygenation results in increased erythropoietin production. Increased erythropoietin production results in more RBCs. More RBCs results in increased blood oxygenation.

10 10 cells destroyed/hour new cells made/hour RBCs in the circulation ~10 13 Bone Marrow Reticulo- endothelial system Iron Amino acids Iron Amino acids From Diet Iron Amino acids Stool and urine RBC Life Cycle

Abnormal Hematocrit Anemia –____________________________ RBC’s (Nutritional, Pernicious, Aplastic, Renal, Hemorrhagic, Hemolytic) Polycythemia –Increased RBC’s (Primary and Secondary) Sherwood’s Human Physiology 11-5

Hemostasis The regulation of blood fluidity and clotting in response to a broken blood vessel (ie. stop the bleeding). –Under normal conditions blood is maintained in a fluid clot-free state. –At the site of a vascular injury this state is rapidly changed with the formation of a platelet plug. The opposite of normal hemostasis is thrombosis in which a blood clot forms and occludes an uninjured or mildly injured blood vessel.

Hemostasis The 3 components of hemostasis are: –The vessel wall –________________________ –The coagulation cascade The 3 major steps of hemostasis are: –Vascular Spasm (initial response, constricts) –Platelet plug formation –Blood coagulation (clotting)

Platelets Oval discs 1-4  m in diameter. No nuclei. 1/2 life of 8-12 days. Play a major role in hemostasis. Can synthesize important proteins: ADP, Thromboxane A2, Fibrin stabilizing factor. Coat glycoprotein repels normal endothelium, but adheres to exposed collagen on the injured vessel walls.

Sherwood’s Human Physiology 11-9 Origin of Platelets Derived from megakaryocytes in the bone marrow.

Sherwood’s Human Physiology Platelet Plugs Accumulation of platelets to seal small holes in a vessel wall.

Sherwood’s Human Physiology Formation of Platelet Plugs Step 1 –When platelets see damaged vessel wall they adhere to it and swell. Step 2 –They release granules containing ADP and thromboxane A2 (also a vasoconstrictor) which activate nearby platelets to also adhere.

Next Time Blood clotting (cont.). Regulation of blood pressure. Regulation of blood volume. Reading; Sherwood, Chapters 10 &11, Chapter 15 pages ; Robbins, pages 84-90

Objectives Describe the structure and function of lymphatics. Know the components of blood (plasma and cellular components). Describe the function of these blood components. Describe erythropoiesis and its regulation. Know what hemostasis is, as well as its components and steps involved. Describe how platelet plugs form.