BIOL1410 Lecture #13 Blood, Lymph and Lymphatic System PDF

Lecture #13 Blood, Lymph and the Lymphatic System Textbook Chapters 19 and 22  Extracellular Fluids There are three primary types of extracellular fluids: 1. Interstitial fluid: surrounds all cells except blood cells 2. Blood plasma: fluid that sur...

Lecture #13 Blood, Lymph and the Lymphatic System Textbook Chapters 19 and 22  Extracellular Fluids There are three primary types of extracellular fluids: 1. Interstitial fluid: surrounds all cells except blood cells 2. Blood plasma: fluid that surrounds blood cells 3. Lymph: found within lymph vessels that form a component of the lymphatic system  Blood Blood is composed of cells and plasma Cells are formed elements Plasma is the fluid that bathes the cells Blood has a much higher viscosity than water An adult human has 4-6 liters of blood Blood pH ranges from 7.35 to 7.45 The temperature of blood is steadily maintained at 38oC Slightly higher than body temperature because it is always moving and producing heat  Blood: Plasma 1. Plasma: Fluid component of the blood 90% of plasma is water 8% of plasma is protein Albumin (important for maintenance of tissue osmolarity and pH), fibrinogen (important for clot formation) globulins (important for transportà hemoglobin, and immunityà immunoglobulins) 2% of plasma is other solutes Gases such as O2 and CO2, ions (electrolytes), nutrients (ex: glucose), hormones (ex: estrogen, testosterone)  Blood: Formed Elements 2. Formed elements (cells and platelets) Consist of erythrocytes (red blood cells: RBCs), white blood cells (WBCs) and platelets a. Red blood cells (RBCs) Called erythrocytes These cells loose their nucleus once they reach maturity Become anuclear Decreases the lifespan of the cell Live for 120 days after which they are broken down by the spleen Produced in the red bone marrow of adults In the ribs and the sternum Anywhere from 4.3 to 5.8 million red blood cells per mm3 of blood  Blood: Formed Elements a. Red blood cells (RBCs) Contain large quantities of hemoglobin (Hb) Composed of heme and 4 protein chains (globin chains) Heme component is pigmented and responsible for the characteristic red color of blood Contains iron (Fe)à binds to and transports O2 gas throughout the body When red blood cells are broken down, the iron is recycled for reuse The remainder of the heme is converted into bilirubin which is used as a component of bile Bile is synthesized and released from the liver and stored in the gall bladderà released from the gall bladder when needed for digestion Iron is always attached to a carrier protein (ex: transferrin in the blood, ferritin in the spleen/liver) because free iron is toxic  Blood: Formed Elements a. Red blood cells (RBCs) The globin portion transports CO2 throughout the blood Only ~20% of total CO2 transport occurs this wayà remainder uses alternative methods The hematocrit is the percentage of blood volume that is red blood cells The normal value is ~40%  Blood: Formed Elements b. White blood cells (WBCs): Leukocytes Alive at maturity Much larger than red blood cells Function to fight off infection Live for many years ~5000-10,000 WBCs per mm3 of blood Number dramatically increases during periods of infection Two classes: granulocytes and agranulocytes  Blood: Formed Elements b. White blood cells (WBCs): i. Granulocytes: 1. Neutrophils: Function as phagocytes Account for ~60% of all white blood cells 2. Eosinophils: Function to destroy parasites Control inflammation by turning off inflammatory mediators Phagocytize antigen-antibody complexes Account for ~2.4% of all white blood cells 3. Basophils: Produce histaminesà give symptoms of allergyà stimulate inflammation Produce heparinà decreases blood clotting Account for ~0-1% of all white blood cells  Blood: Formed Elements b. White blood cells (WBCs): ii. Agranulocytes: Composed of lymphocytes and monocytes 1. Lymphocytes: Account for 20-25% of all white blood cells Responsible for adaptive immunityà very specific immune responses Numbers increase during infectionà cells are active Two types of lymphocytes: i. T lymphocytes: responsible for the activation of the immune response and the killing of infected host cells ii. B lymphocytes: develop into plasma cells that produce and secrete immunoglobulins (antibodies)  Blood: Formed Elements b. White blood cells (WBCs): ii. Agranulocytes: Composed of lymphocytes and monocytes 2. Monocytes: Called macrophages when mature Macrophages are present in tissueà not found in the blood Ex: alveolar macrophages located in the alveoli of the lungs Professional phagocytes Account for ~4-8% of all white blood cells in the body  Blood: Formed Elements c. Platelets: Key players in the formation of blood clots Produced from the fragmentation of megakaryocytes Have a very short lifespanà ~5-10 days 250,000-500,000 platelets per mm3 of blood  Hematopoiesis Hematopoiesis refers to the generation of all formed elements present in the bloodà red blood cells, white blood cells and platelets Hemocytoblasts are hematopoietic stem cells located in red bone marrow Red bone marrow in adults is located in the axial skeleton, the proximal ends of the humerus and the femur and the pectoral and pelvic girdles Hemocytoblastsà reticulocytesà red blood cells  The Lymphatic System The lymphatic system functions in the bodily defense against infection It is composed of: 1. Lymph: formed from interstitial fluidà similar to the consistency of plasma 2. Lymphatic organs and tissuesà thymus gland, lymph nodes 3. Lymphatic vessels and capillaries  The Lymphatic System 1. Lymph: Interstitial fluid that forms from blood plasma 90% of all interstitial fluid reenters the blood 10% of the interstitial fluid (extracellular fluid) enters into the lymphatic capillaries Lymphatic capillaries are blind ended Drain into collecting tubulesà thin walled and contain valves Valves prevent backflow Lymph flows unidirectionally Away from the tissues Circulation of lymph is facilitated by: Skeletal muscle movement Valves in the vessels to prevent backflow Pressure changes during breathing Smooth muscle contractions in the walls of the lymphatic vessels  The Lymphatic System Lymph nodes: Located at various spots along the length of the collecting vessels Filters the lymph that passes by, removing any microorganisms (bacteria, parasites, fungi), viruses or debris that might be present Lymphatic vessels lead into either the: Right lymphatic ductà dumps lymph into the right subclavian vein Entry point for lymph that is coming from anywhere other than the lower half of the body Thoracic ductà dumps lymph into the left subclavian vein This duct begins as the cisterna chyli in the abdomen Entry point for lymph from the lower half of the body  The Lymphatic System 2. Lymphatic Organs: There are two classes of lymphatic organs: primary and secondary i. Primary lymphatic organs and tissues: a. Red bone marrow: The location of B lymphocyte proliferation and maturation In the developing fetus this is the location of T and B lymphocyte origin b. Thymus: This is the location of T lymphocyte proliferation and maturation ii. Secondary lymphatic organs and tissues: a. The spleen: Site of T and B lymphocyte proliferation Filters blood Destroys old red blood cells, bacteria and toxins  The Lymphatic System 2. Lymphatic Organs: ii. Secondary lymphatic organs and tissues: b. The tonsils: Palatine tonsilsà 2 located in the oropharynxà commonly removed Pharyngeal tonsilsà 1 located in the nasopharynxà adenoids when enlarged Lingual tonsilsà 2 located at the base of the tongue c. Lymph nodes: These are located along the lymphatic collecting vessels Axillary lymph nodesà located under the arms Cervical lymph nodesà located in the neck Inguinal lymph nodesà located in the groin area Pelvic lymph nodeà located in the abdominal area Lymph nodes filter lymph and activate the immune system when an infectious agent is located T and B lymphocytes proliferate mitotically within the lymph node