Blood and lymphatic Physiology

Composition of BloodPlasmaProteins albumin, globulins, clotting proteins, and othersWastes lactic acid, urea, creatinineNutrients glucose, carbohydrates, amino acidsElectrolytes sodium, potassium, calcium, chloride, bicarbonate Respiratory gases oxygen and carbon dioxideFormed elements: Erythrocytes, or red blood cells (RBCs)Leukocytes, or white blood cells (WBCs)Platelets

Functions of BloodSubstance distributionOxygen Metabolic wastesHormonesRegulationBody temperatureNormal pH in bodyAdequate fluid volumeBody protectionclottingBlood prevents infection with: antibodiescomplement proteinsWBCs

Physical Characteristics and VolumePlasma-straw coloredBlood -scarlet (oxygen-rich) dark red (oxygen-poor)Neutral pH (7.357.45)average volume of blood is 56 L for males, and 45 L for femaleswww.ethal.org.my/.../ 021rmgBloodComposition.html

Formed ElementsCells, incomplete cells, cell fragmentsWBCs are complete cellsRBCs have no nuclei or organellesplatelets are just cell fragmentsVariable survival rates120 days RBCs?? Days neutrophilsDerived from a common hematopoietic stem cell

Erythrocytes (RBCs)Physical appearanceShapeSurface area: volume ratio~ 4-6 million/mm3Contain hemoglobin (Hb)FunctionsCarry gases (CO2, O2)

Hemoglobin Structurecomposed of the protein globinmade up of 4 protein chains (a, b) 4 heme groupsironEach hemoglobin molecule can transport four molecules of oxygen

HematopoiesisHematopoiesis blood cell formationRed bone marrow ofAxial skeleton and girdlesEpiphyses of the humerus and femurHemocytoblasts give rise to all formed elements http://sprojects.mmi.mcgill.ca/immunology/immuno3.htm

Controlling RBC count Figure 17.6ImbalanceReduces O2 levels in bloodErythropoietin stimulates red bone marrowEnhanced erythropoiesis increases RBC countNormal blood oxygen levelsStimulus: Hypoxia due to decreased RBC count, decreased availability of O2 to blood, or increased tissue demands for O2Kidney (and liver to a smaller extent) releases erythropoietinIncreases O2-carrying ability of blood

Life Cycle of ErythrocytesThe life span 100120 daysOld erythrocytes become rigid and fragile, and their hemoglobin begins to degenerateDying erythrocytes are engulfed by macrophagesHeme and globin are separated and the iron is salvaged for reuse

Erythrocyte DisordersAnemia too few red blood cells decreased hemoglobin contentabnormal hemoglobin

Erythrocyte DisordersToo few RBCsHemorrhagic anemia Hemolytic anemiaAplastic anemia

Erythrocyte DisordersDecreased Hb:Iron-deficiency anemia Pernicious anemia / Megaloblastic anemia Vitamin B12 deficiency

Erythrocyte DisordersAbnormal hemoglobinThalassemiaSickle cell anemia

Erythrocyte DisordersPolycythemiaToo many rbcs

RBCs have antigens on their external surfacesUnique to the individual Recognized as foreign if transfused into another individualaka : agglutinogens Presence or absence of these antigens is used to classify blood groupsHuman Blood Groups

ABO blood group:Two antigens (A and B) on the surface of the RBCs Two antibodies in the plasma (anti-A and anti-B)4 blood types: A, B, AB, ORh blood group:8 different antigens+ indicates presence; - indicates lack of antigen2 Human Blood Groups

ABO Blood GroupsTable 17.4

Transfusion reactionsDonors cells are attacked by the recipients plasma antibodiesHemolytic disease of the newbornRh- mom x Rh+ dad1st pregnancyMom raises antibodies against Rh+ fetus2nd pregnancy Rh+ antibodies of a sensitized Rh mother cross the placenta and attack and destroy the RBCs of an Rh+ baby

Adverse reactions involving blood groups

Rh Dangers During PregnancyDanger is only when the mother is Rh and the father is Rh+, and the child inherits the Rh+ factorCause severe jaundice, hydrops fetalis, stillbirth

Rh Dangers During PregnancyThe mismatch of an Rh mother carrying an Rh+ baby can cause problems for the unborn childThe first pregnancy usually proceeds without problemsThe immune system is sensitized after the first pregnancyIn a second pregnancy, the mothers immune system produces antibodies to attack the Rh+ blood (HDN=hemolytic disease of the newborn)

Development of Erythroblastosis Fetalis

Development of Erythroblastosis Fetalis

Prevention of erythroblastosis fetalis Injecting a mother who is at risk with anti-Rh immune globulin (RhoGAM) during her first Rh+ pregnancy helps to inactivate and remove the fetal Rh+ cells before her immune system can react and develop sensitivity.

Leukocytes (WBCs)Physical appearanceNucleatedGranules = granulatocytesNo granules - agranulocytesCan leave capillaries via diapedesis & move through tissue spacesFunctionNormal response to bacterial or viral invasion

Granulocytes

NeutrophilsEosinophilsBasophilsgranules stain pink, blue or purple (Wrights stain)larger and usually shorter-lived than RBCsHave lobed nucleiAre all phagocytic cells

Agranulocyteslymphocytes and monocytes:Lack visible cytoplasmic granulesHave spherical (lymphocytes) or kidney-shaped (monocytes) nucleiwww.biology.eku.edu/ RITCHISO/301notes4.htm

Formation of LeukocytesFigure 17.11 Leukopoiesisred bone marrow

hematocytoblasts two lines

committed, differentiate

hormonally controlled Cytokines

Leukocytes DisordersLeukemiawhite blood cell cancerMyelocytic leukemia involves myeloblastsLymphocytic leukemia involves lymphocytesAcute leukemia - primarily affects childrenChronic leukemia - more prevalent in older peoplewww-sdc.med.nagasaki-u.ac.jp/. ../Leukemia-E.html NORMALALLAMLCML

PlateletsCell fragmentsblue-staining outer region and a purple granular centerContain chemicals important for clottingFunction Vascular plugchapters.redcross.org/. ../platelets.html

Formation of PlateletsHemocytoblastmegakaryocytesFigure 17.12

HemostasisPhases:Vascular spasms immediate vasoconstriction in response to injuryPlatelet plug formationCoagulation (blood clotting)Prothrombin activatorThrombinFibrin

Vessel damage, blood loss2. Vascular spasm.

Platelet plug forms4. Coagulation

Coagulation factors

Clot Retraction and RepairClot retraction stabilization of the clot by squeezing serum from the fibrin strandsRepairGrowth factors stimulate rebuilding of blood vessel wallFibroblasts form a connective tissue patchendothelial cells multiply and restore the endothelial liningwww.venousaccess.com/ thrombolysis.htm

ClotsFloating, persistant, widespreadThrombus a clot that develops and persists in an unbroken blood vesselEmbolus a thrombus freely floating in the blood streamDisseminated Intravascular Coagulation (DIC): Too few plateletsThrombocytopeniaBleeding disordersMissing liver procoagulantHemophilias genetic; missing clotting factors

Clotting Disorders

Lymphatic System: OverviewConsists of two semi-independent partsA meandering network of lymphatic vesselsLymphoid tissues and organs scattered throughout the bodyReturns interstitial fluid and leaked plasma proteins back to the bloodLymph interstitial fluid once it has entered lymphatic vessels

Lymphatic System: OverviewFigure 20.2a

Lymphatic System: OverviewFigure 20.1a

Lymphatic VesselsA one-way system in which lymph flows toward the heartLymph vessels include:Microscopic, permeable, blind-ended capillariesLymphatic collecting vesselsTrunks and ducts

Lymphatic CapillariesSimilar to blood capillaries, with modificationsRemarkably permeableLoosely joined endothelial minivalvesWithstand interstitial pressure and remain openThe minivalves function as one-way gates that:Allow interstitial fluid to enter lymph capillariesDo not allow lymph to escape from the capillaries

Lymphatic CapillariesDuring inflammation, lymph capillaries can absorb:Cell debrisPathogensCancer cells Cells in the lymph nodes:Cleanse and examine this debris Lacteals specialized lymph capillaries present in intestinal mucosaAbsorb digested fat and deliver chyle to the blood

Lymphatic TrunksLymph is delivered into one of two large trunksRight lymphatic duct drains the right upper arm and the right side of the head and thoraxThoracic duct arises from the cisterna chyli and drains the rest of the body

Lymphatic TrunksFigure 20.2b

Lymph TransportThe lymphatic system lacks an organ that acts as a pumpVessels are low-pressure conduitsUses the same methods as veins to propel lymphPulsations of nearby arteriesContractions of smooth muscle in the walls of the lymphatics

Lymphoid CellsLymphocytes are the main cells involved in the immune response The two main varieties are T cells and B cells

LymphocytesT cells and B cells protect the body against antigensAntigen anything the body perceives as foreignBacteria and their toxins; virusesMismatched RBCs or cancer cells

LymphocytesT cells Manage the immune responseAttack and destroy foreign cellsB cells Produce plasma cells, which secrete antibodiesAntibodies immobilize antigens

Other Lymphoid CellsMacrophages phagocytize foreign substances and help activate T cellsDendritic cells spiny-looking cells with functions similar to macrophagesReticular cells fibroblastlike cells that produce a stroma, or network, that supports other cell types in lymphoid organs

Lymph NodesTheir two basic functions are:Filtration macrophages destroy microorganisms and debrisImmune system activation monitor for antigens and mount an attack against them

Structure of a Lymph NodeFigure 20.4a, b

Other Lymphoid OrgansThe spleen, thymus gland, and tonsilsPeyers patches and bits of lymphatic tissue scattered in connective tissue All are composed of reticular connective tissue and all help protect the bodyOnly lymph nodes filter lymph

SpleenLargest lymphoid organ, located on the left side of the abdominal cavity beneath the diaphragm It extends to curl around the anterior aspect of the stomachIt is served by the splenic artery and vein, which enter and exit at the hilusFunctionsSite of lymphocyte proliferationImmune surveillance and responseCleanses the blood

Additional Spleen FunctionsStores breakdown products of RBCs for later reuseSpleen macrophages salvage and store iron for later use by bone marrowSite of fetal erythrocyte production (normally ceases after birth)Stores blood platelets

Structure of the SpleenFigure 20.6a-d

ThymusA bilobed organ that secrets hormones (thymosin and thymopoietin) that cause T lymphocytes to become immunocompetentThe size of the thymus varies with ageIn infants, it is found in the inferior neck and extends into the mediastinum where it partially overlies the heartIt increases in size and is most active during childhood It stops growing during adolescence and then gradually atrophies

TonsilsSimplest lymphoid organs; form a ring of lymphatic tissue around the pharynxLocation of the tonsilsPalatine tonsils either side of the posterior end of the oral cavityLingual tonsils lie at the base of the tonguePharyngeal tonsil posterior wall of the nasopharynxTubal tonsils surround the openings of the auditory tubes into the pharynx

TonsilsLymphoid tissue of tonsils contains follicles with germinal centersTonsil masses are not fully encapsulatedEpithelial tissue overlying tonsil masses invaginates, forming blind-ended cryptsCrypts trap and destroy bacteria and particulate matter

Aggregates of Lymphoid FolliclesPeyers patches isolated clusters of lymphoid tissue, similar to tonsilsFound in the wall of the distal portion of the small intestineSimilar structures are found in the appendixPeyers patches and the appendix:Destroy bacteria, preventing them from breaching the intestinal wallGenerate memory lymphocytes for long-term immunity

MALTMALT mucosa-associated lymphatic tissue is composed of:Peyers patches, tonsils, and the appendix (digestive tract)Lymphoid nodules in the walls of the bronchi (respiratory tract)MALT protects the digestive and respiratory systems from foreign matter