Chap 2 A&P II

Chap 19- The blood

*A fluid connective tissue (living cells+non-living matrix)

3 formed elements Plasma (fluid)

Functions: Transportation: O2, CO2, nutrients, waste, hormones…

Regulation: fluid levels, pH, body temp.

Protection: against disease, infection. 

pH of blood: 7.35-7.45 (slightly alkaline) 

45% formed elements, 55% plasma

Blood plasma: ~92% H2O, 8% solutes (mostly proteins). Plasma proteins are synthesized in liver. Most common is albumin, then globulins , fibrinogen.”Antibodies” are proteins called “gamma globulins” or “immunoglobulins”. 

Other solutes: electrolytes, hormones, urea, uric acid. 

3 formed elements: Erythrocytes (RBC’s), leukocytes (WBC), thermocytes (Platelets)

Blood cell formation: “Hemopoiesis” or “hematopoiesis”

Site: red bone marrow

Hemocytoblast (primary stem cell) gives rise to all 3 formed elements. 

Regulation of hemopoiesis

1. Erythroprotein (EPO) hormone secreted by kidneys that increases the rate of RBC maturation. Hypoxia stimulates EPO secretion.

2. Throbopoietin- Hormone secreted by liver. Stimulates formation of platelets.

3. Cytokines (Glycoproteins)- Chemical produced by cells that stimulate leulocyte formation. a) CSF’s b)Inter

Erythrocytes (RBC’s)

-biconcave discs

-anucleate—> cannot replicate

-sacs of hemoglobin—> O2 carrying protein

-No mitochondria

Hemoglobin (Hb): 4 “heme” groups that bind O2

( 1 hb binds 4 O2 molecules). Each RBC contains ~280 million hb molecules. So a single RCC can bind→ over a billion molecules of O2

*Hb can also bind CO2, but it binds to an a.a on globin chain not to heme group, so it does not directly compete with O2. 

RBC lifespan~ 120 days 

Old RBC’s get recycled in the spleen.

-The a.a’s and iron get reused

-The rest goes to liver—>used in bile–execreted in feces, urine. 

Hemopoiesis recap: hemocytoblast→ myeloid stem cell—> proereythroblast–reticulocyte

Regulation recap: Hypoxia in blood. (increases in altitiude, anemia, decrease in circulation). Hypoxia stimulate to secrete EPO hormone decrease rate of RBC development. 

Anemia(Symptoru)- O2 carrying capacity of blood is compromised. 

3 main types of anemia:

1. Hemorrhagic anemia- blood loss

2. Decrease in RBC production (4 examples): 

1. Lack of iron*

2. Pernicisous Anemia (autoimmune)- immune cells attack intrinisic factor secreting cells of stomach→ that compromises vitamin B12 absorption→ RBC’s don’t develop properly. (old people)

3. Renal anemia- causes a lack of EPO

4. Aplastic anemia- drugs, chemicals, viruses, irradiation. 

3. Hemolytic- distruction/distortion of RBC’s 

1. Thalassemia:genetic. A globin chain is absent (or faulty) severe. 

2. B Sickle cell anemmia: genetic 1 single amino acid is incorrectly substituted causin globin chain to fold back on itself 

Continued

Leukocytes (WBC)

-Have a nucleus (no hemoglobin)

2 main classes 

1. Granulocytes (have cytoplasmic granules that stain)

1. Neutrophils-lobed nuclei

2. Eosinphils- stain red/orange. Dumbbell shaped nucleus

3. Basophils-stain blue/purple (many granules)

      2. Agranulocytes (Granules don’t stain)

1. Lymphocytes- small w/ large purple nucleus 

2. Monocytes- large cells, horse shoe shape nucleus become macrophages when migrating out of blood.*

Leukocyle function: defend against infections. “Leukocytosis” increase in # of wbc’s/leukopenia: decrease in # of wbc’s. 

*fight infection through “diapedsis”, phagocytosis, immune responses. 

“Adhesion molecules” on endothelium of blood vessels signal leukocytes in response to injury, infection, inflamation. 

“Phagocytosis”- cell eating.

“Phagocytes”- WBC’s/macrophages that ingest/destroy foreign microorganisms. 

Specific functions: Neutrophils respond quickly to acute bacterial infections. Can release defensins (antibacterial proteins). 

Form peptide spears that penetrate bacteria. Then perform “respiratory bursts” oxidizing agents (hydrogen peroxide and bleach that destroy bacteria. 

Eosinophils: also diapedes. Granules contain digestive enzymes that destroy parasitic worms. Also release antihistamines to combat inflammation. 

Basophilis: Diapedese. Release heparin, histamine, serotonin. This increases inflammation (during allergic reactions) 

Lymphocytes: More through lymph nodes, tissue, lymph fluid and blood. Usually found outside of blood stream. 

3 types-  T-lymphocytes (kill virally infections), B-lymphocytes- become “plasma cells” that secrete antibodies. (against bacterial infections.)

Natural killer cells- a type of lymphocytes that kills tumor cells and micro-organism infections 

Monocytes: differentiate into wandering macrophages (non specific immune cells). Effective against chronic bacterial infections (TB). 

Platelets (Thrombocytes)

Hemocytoblast—-> Megakaryocytes—-> platelets.

• *Platelets are small cytoplasmic pieces of megakarocytes. Anucleate. 

• Granules in platelets release chemicals that promote “Hemostatis” (blood clotting)

• Lifepsan~ 5-10 days (if unused)

Hemostasis (short version)

1. Vascular spasm: after injury, a vessel responds by contracting (caused by damage to smooth muscle)

2. Platelet plug formation: 1st platelets stick to damaged vessel (from exposed collagen) “Platelet adhesion”  2nd-activated platelets release ADP, thromboxane, serotonin 

3. Coagulation/blood clotting