Composition of Blood : Composition of Blood Consists of formed elements (cells) suspended & carried in plasma (fluid part)
Total blood volume is about 5L
Plasma is straw-colored liquid consisting of H20 & dissolved solutes
Includes ions, metabolites, hormones, antibodies 13-7
Plasma Proteins : Plasma Proteins Constitute 7-9% of plasma
Three types of plasma proteins: albumins, globulins, & fibrinogen
Albumin accounts for 60-80%
Creates colloid osmotic pressure that draws H20 from interstitial fluid into capillaries to maintain blood volume & pressure
Globulins carry lipids
Gamma globulins are antibodies
Fibrinogen serves as clotting factor
Converted to fibrin
Serum is fluid left when blood clots 13-8
Formed Elements : Formed Elements Are erythrocytes (RBCs) & leukocytes (WBCs)
RBCs are flattened biconcave discs
Shape provides increased surface area for diffusion
Lack nuclei & mitochondria
Each RBC contains 280 million hemoglobins Fig 13.3 13-9
Leukocytes : Leukocytes Have nucleus, mitochondria, & amoeboid ability
Can squeeze through capillary walls (diapedesis)
Granular leukocytes help detoxify foreign substances & release heparin
Include eosinophils, basophils, & neutrophils Fig 13.3 13-10
Leukocytes continued : Leukocytes continued Agranular leukocytes are phagocytic & produce antibodies
Include lymphocytes & monocytes Fig 13.3 13-11
Platelets (thrombocytes) : Platelets (thrombocytes) Are smallest of formed elements, lack nucleus
Are fragments of megakaryocytes; amoeboid
Constitute most of mass of blood clots
Release serotonin to vasoconstrict & reduce blood flow to clot area
Secrete growth factors to maintain integrity of blood vessel wall
Survive 5-9 days Fig 13.3 13-12
Hematopoiesis : Hematopoiesis Is formation of blood cells from stem cells in marrow (myeloid tissue) & lymphoid tissue
Erythropoiesis is formation of RBCs
Stimulated by erythropoietin (EPO) from kidney
Leukopoiesis is formation of WBCs
Stimulated by variety of cytokines
= autocrine regulators secreted by immune system 13-13
Erythropoiesis : Erythropoiesis 2.5 million RBCs are produced/sec
Lifespan of 120 days
Old RBCs removed from blood by phagocytic cells in liver, spleen, & bone marrow
Iron recycled back into hemoglobin production Fig 13.4 13-14
RBC Antigens & Blood Typing : RBC Antigens & Blood Typing Antigens present on RBC surface specify blood type
Major antigen group is ABO system
Type A blood has only A antigens
Type B has only B antigens
Type AB has both A & B antigens
Type O has neither A or B antigens 13-15 Click here to play
ABO Blood Types
RealMedia Movie
Transfusion Reactions : Transfusion Reactions People with Type A blood make antibodies to Type B RBCs, but not to Type A
Type B blood has antibodies to Type A RBCs but not to Type B
Type AB blood doesn’t have antibodies to A or B
Type O has antibodies to both Type A & B
If different blood types are mixed, antibodies will cause mixture to agglutinate Fig 13.5 13-16
Transfusion Reactions continued : Transfusion Reactions continued If blood types don't match, recipient’s antibodies agglutinate donor’s RBCs
Type O is “universal donor” because lacks A & B antigens
Recipient’s antibodies won’t agglutinate donor’s Type O RBCs
Type AB is “universal recipient” because doesn’t make anti-A or anti-B antibodies
Won’t agglutinate donor’s RBCs Insert fig. 13.6 Fig 13.6 13-17
Hemostasis : Hemostasis Is cessation of bleeding
Promoted by reactions initiated by vessel injury:
Vasoconstriction restricts blood flow to area
Platelet plug forms
Plug & surroundings are infiltrated by web of fibrin, forming clot 13-19
Role of Platelets : Role of Platelets Platelets don't stick to intact endothelium because of presence of prostacyclin (PGI2--a prostaglandin) & NO
Keep clots from forming & are vasodilators 13-20 Fig 13.7a
Role of Platelets : Role of Platelets Damage to endothelium allows platelets to bind to exposed collagen
von Willebrand factor increases bond by binding to both collagen & platelets
Platelets stick to collagen & release ADP, serotonin, & thromboxane A2
= platelet release reaction 13-21 Fig 13.7b
Role of Platelets continued : Role of Platelets continued Serotonin & thromboxane A2 stimulate vasoconstriction, reducing blood flow to wound
ADP & thromboxane A2 cause other platelets to become sticky & attach & undergo platelet release reaction
This continues until platelet plug is formed 13-22 Fig 13.7c
Role of Fibrin : Platelet plug becomes infiltrated by meshwork of fibrin
Clot now contains platelets, fibrin & trapped RBCs
Platelet plug undergoes plug contraction to form more compact plug Role of Fibrin 13-23
Conversion of Fibrinogen to Fibrin : Can occur via 2 pathways:
Intrinsic pathway clots damaged vessels & blood left in test tube
Initiated by exposure of blood to negatively charged surface of glass or blood vessel collagen
This activates factor XII (a protease) which initiates a series of clotting factors
Ca2+ & phospholipids convert prothrombin to thrombin
Thrombin converts fibrinogen to fibrin which polymerizes to form a mesh
Damage outside blood vessels releases tissue thromboplastin that triggers a clotting shortcut (= extrinsic pathway) Conversion of Fibrinogen to Fibrin 13-24
Slide 18 : Fig 13.9 13-25
Dissolution of Clots : Dissolution of Clots When damage is repaired, activated factor XII causes activation of kallikrein
Kallikrein converts plasminogen to plasmin
Plasmin digests fibrin, dissolving clot 13-26
Anticoagulants : Anticoagulants Clotting can be prevented by Ca+2 chelators (e.g. sodium citrate or EDTA)
or heparin which activates antithrombin III (blocks thrombin)
Coumarin blocks clotting by inhibiting activation of Vit K
Vit K works indirectly by reducing Ca+2 availability 13-27
Prostaglandins (PGs) : Prostaglandins (PGs) Are produced in almost every organ
Belong to eicosanoid family -- all derived from arachidonic acid of plasma membrane Fig 11.34 11-72
Prostaglandins (PGs) continued : Have wide variety of functions
Different PGs may exert antagonistic effects in tissues
Some promote smooth muscle contraction & some relaxation
Some promote clotting; some inhibit
Promotes inflammatory process of immune system
Plays role in ovulation
Inhibits gastric secretion in digestive system Prostaglandins (PGs) continued 11-73
Prostaglandins (PGs) continued : Cyclooxygenase (COX) 1 & 2 are involved in PG synthesis (Fig 11.34)
Are targets of a number of inhibitory non-steroidal anti-inflammatory drugs (NSAIDs)
Aspirin, indomethacin, ibuprofen inhibit both COX 1 & 2 thereby producing side effects
Celebrex & Vioxx only inhibit COX 2 & thus have few side effects Prostaglandins (PGs) continued 11-74