BIOL 1120 Worksheet 1) Describe the function of Hemoglobin. A Hemoglobin molecule consists of 4 heme and 4 globin molecules. The heme molecules transports O2, and the globin molecules transport CO2 and Nitric Oxide. Iron is required for O2 transport. The endothelial cells lining the blood vessels produce the Nitric Oxide. When O2 is released in tissues, so is the Nitric Oxide, which functions as a chemical messenger that induces the relaxation of the smooth muscle of the blood. By affecting the amount of Nitric Oxide in the tissues, hemoglobin may play a role in regulating blood pressure bc the relaxation of blood vessels results in decreased blood pressure

2) Describe the Life Span of an Eyrthrocyte. How are red blood cells removed from the body? The process by which new red blood cells are produces is called erythropoiesis, and the time required to produce a single red blood cell is about 4 days. Stem cells in red bone marrow give rise to proerythroblasts. After several mitotic division proerythroblasts become early (basophilic) erythroblasts. Early (basophilic) erythroblasts give rise the intermediate (polychromatic) erythroblasts. Intermediate Erythroblasts continue to produce hemoglobin and most of their ribosomes and other organelles degenerate resulting in late erythroblasts that are reddish in color bc 1/3 of their cytoplasm is hemoglobin. Late Erythroblasts lose their nuclei by a process of extrusion to become immature red blood cells called Reticulocytes. These cells reticulum, or network, can be observed in the cytoplasm. Reticulocytes are released from the bone marrow into the circulating blood. With in 2 days, the ribosomes in the cells degenerate and the reticulocytes become mature red blood cells.

Red blood cells production is stimulated by low blood O2, which typically results from decreased numbers of red blood cells, decreased or defective hemoglobin, disease of the lungs, high altitude, inability of the cardio system to deliver blood to tissues and increased tissue demand for O2 – ie: during endurance exercise.

Low blood O2 levels stimulate red blood cell production by increasing the formation of the glycoprotein erythropoietin (hormone produced mostly by Kidneys). Erythropoietin stimulates red bone marrow to produce more red blood cells by increasing the number of proerythroblasts.

Blood O2 Levels Decrease Erythropoietin Production Increases Increasing Red Blood Cells Production the greater # of red blood cells increases the blood’s ability to transport O2

Red blood cells stay in circulation for ~120 days. These cells have no nuclei and therefore can’t produce new proteins or divide. As their existing proteins, enzymes, plasma membrane components, and other structures degenerate, the red blood cells are less able to transport O2 and their plasma membranes become more fragile and eventually the red blood cells rupture. Hemoglobin from ruptured blood cells is phagocytized by Macrophages in the spleen, liver and other lymphatic tissue. Enzymes digest the hemoglobin to yield amino acids, iron and bilirubin. The heme becomes bilirubin which is secreted in bile.

3) Outline the procedure of Hemostasis. Hemostasis is the stoppage of bleeding and is very important to the maintenance of homeostasis. When a vessel is damaged, a series of events helps prevent excessive blood loss

1. Vascular Spasm : vacoconstriction of damaged blood vessels reduces blood loss

2. Platelet Plug Formation a. Platelets repair minor damage to vessels by forming platelet plugs

i. Platelet Adhesion: platelets bind to collagen in damaged tissuesii. Platelet Release Reaction: platelets release chemicals that activate

additional plateletsiii. Platelet Aggregation: platelets bind to one another to form a

platelet ringiv. Platelets also release chemicals involved with coagulation

3. Coagulation : formation of a blood clota. Extrinsic Pathway: release of thromboplastin from damaged tissues

i. Also known as TF (tissue factor), or factor IIIii. TF in the presence of Ca forms a complex with factor VII that

activates factor X, which is the beginning of a common pathwayb. Intrinsic Pathway: begins with the activation of factor XII

i. Activated XII, stimulates factor XI, which activates factor IX which joins to factor VII, platelet phospholipids, and Ca to activate facto X, which is the beginning of the common pathway

c. Activated factor X, factor V, phospholipids and Ca form Prothrombinase

d. Prothrombin is converted to thrombin by Prothrombinasee. Fibrinogen is converted to fibrin by thrombin

i. Insoluble fibrin forms the clot

4. Control of Clot Formationa. Heparin and antithrombin inhibit thrombin activity

i. Thus, fibrinogen is not converted to fibrin and clot formation is inhibited

b. Prostacyclin counteracts the effects of thrombin

5. Clot Retraction and Dissolutiona. Clot Retraction : results from the contraction of platelets, which pull the

edges of damaged tissue closer togetherb. Serum : plasma minus fibrinogen and some clotting factors is squeezed

out of the clotc. Factor XII, thrombin, tissue plasminogen activator, and urokinase

activate plasmin, which dissolves fibrin (the clot)

4) A laboratory test of a patient’s blood reveals a hematocrit of 15%. Microscopic examination of the blood also reveals several distorted and ruptured red blood cells. In addition, the reticulocyte count is 2%. Based on all of these findings, from what disorder do you think the patient is suffering?

Hematocrit is the percentage of the total blood volume that is composed of red blood cells. In males this is usually 40-54% and 38-47% in females. Anemia is a deficiency of hemoglobin in the blood. A 15% hematocrit rate is extremely low and points towards Anemia. Hemolytic Anemia occurs when red blood cells rupture or is destroyed at an excessive rate. Because of the rapid destruction of red blood cells we would expect erythropoiesis to increase in an attempt to replace lost red blood cells. The reticulocyte count would there fore be above normal (1-3% is normal); however, this patient’s reticulocyte count is normal at 2%.