19. Blood

Question 1

Blood functions:

Answer 1

1) Transport: O2 and nutrients to cells, CO2 and metabolic wastes away from cells
2) Regulate: body temp, pH, water content of tissues
3) Protect: against blood loss (clotting), against infection (WBC)

Question 2

What is blood composed of

Answer 2

Plasma (55%)
Formed elements (45%)
> red blood cells (erythrocytes)
> white blood cells (leukocytes)
> platelets (thrombocytes) are cell fragments

Question 3

Blood Plasma

Answer 3

Fluid portion of blood; straw-colored
Composed of 90% water and 10% solutes
Solutes: electrolytes, nutirents, enzymes, hormones, gases, metabolic wastes

Question 4

Plasma Proteins

Answer 4

account for 8% of the 10% of dissolved solutes in plasma
1) Albumin 60% - maintenance of osmotic pressure,
blood pH buffer, carrier molecule of fatty acids and steroid hormones
2) ) Globulins 36% -
3) Fibrinogen 4% - fibrin precursor acts in blood clotting

Question 5

Red Blood Cells

Answer 5

• Eurythrocyte
• Function: transport of respiratory gases - O2, CO2
• Biconcave disc, anucleated
• Contain about 250 million molecules of hemoglobin (Hb) per cell
• Each heme binds one O2 molecule reversibly, globin binds CO2
• Formed constantly by erythropoiesis in red bone marrow

Question 6

What happens when homeostatis is distrubed and RBS are low (Low 02 transportation ability)

Answer 6

homeostasis is disrupted as oxygen levels in blood decrease

kidney cells detect low oxygen levels and release erythropoietin (a hormone)

erythropoietin stimulates increased red blood cell formation in red bone marrow

increased number of red blood cells enter the circulation

increase in oxygen levels in the blood and homeostasis is restored

Question 7

Blood cell formation is called

Answer 7

hematopoiesis

Question 8

How are blood cells formed?

Answer 8

• arise from a Pluripotent stem cell in red bone marrow (hemocytoblast)
• form 2 stem cell lines:
1) myeloid stem cells (RBC’s, Platelets, Eosinophils, Basophils, Neutrophils & Monocytes)
2) lymphoid stem cells (lymphocytes)

Question 9

How are RBS recycled/broken down

Answer 9

• anucleate so can’t grow and divide
• old or damaged RBC’s destroyed by macrophages in the spleen, liver, and bone marrow
• hemoglobin is salvaged –> degraded to heme + globin
• globin broken down to amino acids (reused)
• heme iron released/stored in liver/spleen (reused)
• heme pigment degraded to bilirubin
• bilirubin secreted into bile in liver

Question 10

White Blood Cells + types

Answer 10

• Leukocytes
• less numerous
• nucleus
• Generally function to combat pathogens by phagocytosis or immune responses

Granulocytes: contains granules

• Neutrophil: highly phagocytic, ingest bacteria and fungi
• Eosinophil: phagocytic cells that destroy antigen-antibody complexes
• Basophil: release histamine and heparin in allergic reactions

Agranulocytes: no granules

• Lymphocyte: mediate immune responses
• Monocyte: become wandering macrophages

Question 11

Platelets

Answer 11

• Anucleate fragments of megakaryocytes
• Function: blood clotting by forming a platelet plug and release chemicals that promote clotting

Clotting:

1) Vascular spasm - SM contracts –> vasoconstriction
2) Platelet plug formation - platlet adhere, chemical relases, nearby platlet becomes sticky
3) Coagulation - fibrin forms mesh trap

Question 12

Hemostasis

Answer 12

• Sequence of events which stop bleeding when a blood vessel is damaged
• Response must be fast, localized and carefully controlled
3 steps:
> Vascular Spasm
> Platelet Plug Formation
> Clot formation (Coagulation)

Question 13

Hemostasis: Vascular Spasm

Answer 13

• in response to injury, damaged vessel constricts and blood flow is reduced
• SM contracts –> vasoconstriction

Question 14

Hemostasis: Platelet Plug Formation

Answer 14

• platelets touch + stick to collagen fibers → platelet adhesion
• once attached, platelets are ‘activated’
• releases chemicals become “sticky”
• release serotonin + thromboxane + ADP to enhance vascular spasm and platelet aggregation
• attracks platelets –> activated → platelet aggregation
form a mass → platelet plug within 1 min

Question 15

Hemostasis: Clot formation (Coagulation)

Answer 15

• complex cascade of chemical reactions involving enzyme-like substances known as “Factors”
• transform blood from a liquid to a gel
• clot completed in 3-6 minutes
• Fibrinogen (a soluble protein in the blood plasma ) → Fibrin (an insoluble thread-like molecule)

Question 16

Steps in Clot formation (Coagulation)

Answer 16

Phase 1. Two pathways lead to formation of prothrombin activator (enzyme)

a) Intrinsic pathway (blood trauma): blood is exposed to damaged endothelium “inside a vessel”
- Factor XII is activated & in the presence of Ca2+ and PF3 activates Factor X
b) Extrinsic pathway (tissue trauma): Blood is exposed to damaged tissue “outside a vessel”
- Tissue cells release Factor III which in the presence of Ca2+ directly activates Factor X

Phase 2.
- Factor X combines with Ca2+, PF3 and Factor V to form prothrombin activator. Converts prothrombin –> thrombin

Phase 3.

• Thrombin converts fibrinogen –> fibrin
• fibrin forms the threads of the clot

Question 17

Once a blood clot has formed

Answer 17

Once clot has formed:
• clot retracts - edges of torn vessel are pulled closer together
• permanent repair of vessel occurs

Clot dissolves (fibrinolysis) after the wound has healed
plasmin, a fibrin-digesting protein becomes activated

Question 18

TRANSFUSION RULE

Answer 18

Recipients antibodies must not match donor’s antigens!

• Antibody in plasma
• Antigen on surface of RBC

Question 19

Rh System

Answer 19

• Antigen D is the most common of the Rh factors
• Term Rh positive signifies the presence of antigen D on the RBC (85% of North American population)
• There are no naturally occurring Rh antibodies in the blood plasma
• People who are Rh negative (lack D antigen) will form antibodies against antigen D if it is introduced into their blood
• Problem can occur if an Rh- mother has an Rh+ child