Ch17-Blood

What is the Pathway of blood……..oxygenated vs deoxygenated, etc

O2 loading in the lungs → Produces oxyhemoglobin (ruby red); O2 unloading in the tissues → Produces deoxyhemoglobin or reduced hemoglobin (dark red); CO2 loading in the tissues → Produces carbaminohemoglobin (carries 20% of CO2 in the blood)

Blood is composed of what

Plasma and formed elements

Plasma

55% of whole blood; 90% water; proteins; nitrogenous by-products; nutrients; electrolytes; respiratory gases; hormones

Formed elements

Erythrocytes (RBCs), leukocytes (WBCs), and platelets

What is a hematocrit?

Percent of blood volume that is RBCs; 47% ± 5% for males; 42% ± 5% for females

What is plasma pH?

7.35–7.45

What is plasma temperature?

38°C

What % of body weight is blood?

~8% of body weight

What is male blood volume?

5–6 L

What is female blood volume?

4–5 L

What functions does blood have?

Distribution, regulation, and protection

Distribution

O2 and nutrients to body cells; metabolic wastes to the lungs and kidneys; hormones from endocrine organs to target organs

Regulation

Body temperature; normal pH using buffers; adequate fluid volume in the circulatory system

Protection

Blood loss—plasma proteins and platelets initiate clot formation; infection—antibodies, complement proteins, and WBCs defend against foreign invaders

What types of things are found in plasma?

90% water; proteins; nitrogenous by-products of metabolism; nutrients; electrolytes; respiratory gases; hormones

What are the three types of formed elements?

WBCs, RBCs, and platelets

What is an erythrocyte?

Biconcave disc, anucleate, essentially no organelles

What is an erythrocyte filled with?

Hemoglobin (Hb) for gas transport

What other protein is in the RBC cytoplasm?

Spectrin

Why is an RBC a biconcave disc?

Huge surface area relative to volume

What is the greatest mass in an RBC?

97% hemoglobin (not counting water)

Why does an RBC use anaerobic metabolism?

No mitochondria; ATP production is anaerobic; no O2 is used in generation of ATP

What is the major RBC function?

RBCs are dedicated to respiratory gas transport; hemoglobin binds reversibly with oxygen

What is the structure of hemoglobin (Hb)?

Protein globin: two alpha and two beta chains; heme pigment bonded to each globin chain; iron atom in each heme can bind to one O2 molecule; each Hb molecule can transport four O2

How are RBCs produced?

Hematopoiesis (hemopoiesis): blood cell formation

Where are RBCs produced?

Red bone marrow of axial skeleton, girdles, and proximal epiphyses of humerus and femur

RBC production pathway

hemocytoblast >> proerythroblast >> early erythroblast >> late erythroblast >> normoblast >> reticulocyte >> erythrocyte

How are RBC numbers regulated?

Balance between RBC production and destruction depends on hormonal controls and adequate supplies of iron, amino acids, and B vitamins

What things are needed for RBC production?

Iron, amino acids, B vitamins, and hormonal controls

Under what conditions is EPO released?

The kidneys release EPO in response to hypoxia

What does increased RBCs do?

Increases O2-carrying ability of blood

How long-lived are RBCs?

100–120 days (3–4 months)

What happens to old RBCs?

Macrophages engulf dying RBCs in the spleen; iron is salvaged for reuse; heme is degraded to bilirubin; globin is metabolized into amino acids

What is anemia?

Blood has abnormally low O2-carrying capacity; a sign rather than a disease itself

What are symptoms of anemia?

Fatigue, paleness, shortness of breath, and chills

What is hemorrhagic anemia?

Acute or chronic loss of blood

What is hemolytic anemia?

RBCs rupture prematurely

What is aplastic anemia?

Destruction or inhibition of red bone marrow

What is iron deficiency anemia?

Secondary result of hemorrhagic anemia or inadequate intake of iron-containing foods or impaired iron absorption

What is pernicious anemia?

Deficiency of vitamin B12; lack of intrinsic factor needed for absorption of B12

What are thalassemias?

Absent or faulty globin chain (alpha or beta); RBCs are thin, delicate, and deficient in hemoglobin

What is sickle-cell anemia?

Defective gene codes for abnormal hemoglobin (HbS); causes RBCs to become sickle shaped in low-oxygen situations

What is polycythemia?

Excess of RBCs that increase blood viscosity

What is polycythemia vera?

Bone marrow cancer

What is secondary polycythemia?

When less O2 is available (high altitude) or when EPO production increases

What is blood doping?

Blood doping

What are leukocytes?

WBCs; make up <1% of total blood volume

What is the normal leukocyte number?

4800–10,800/l

What is leukocytosis?

WBC count over 11,000/mm3

What are neutrophils?

50–70%; very phagocytic—“bacteria slayers”

What are eosinophils?

2–4%; digest parasitic worms that are too large to be phagocytized; modulators of the immune response

What are basophils?

0.5–1%; rarest WBCs; granules contain histamine

What are lymphocytes?

25–45%; crucial to immunity; T cells act against virus-infected cells and tumor cells; B cells give rise to plasma cells, which produce antibodies

What are monocytes?

3–8%; largest leukocytes; leave circulation, enter tissues, and differentiate into macrophages; actively phagocytic cells

How are leukocytes stimulated to develop?

Chemical messengers from bone marrow and mature WBCs; interleukins (e.g., IL-1, IL-2); colony-stimulating factors (CSFs)

What is the leukocyte pathway?

Hemocytoblast → myeloid stem cell / lymphoid stem cell → myeloblast/promyelocyte/myelocytes or monoblast/promonocyte/monocytes or lymphoblast/prolymphocyte/lymphocytes

What is leukemia?

Cancerous conditions involving WBCs

What is acute leukemia?

Involves blast-type cells and primarily affects children

What is chronic leukemia?

More prevalent in older people

Where do platelets come from?

Small fragments of megakaryocytes

Are platelets cells?

Platelets are cell fragments

What three events occur in hemostasis?

Vascular spasm; platelet plug formation; coagulation (blood clotting)

What is vasospasm?

Vasoconstriction of damaged blood vessel

What triggers vasospasm?

Direct injury; chemicals released by endothelial cells and platelets; pain reflexes

What causes platelet plug formation?

Platelets stick to exposed collagen fibers with the help of von Willebrand factor; swell, become spiked and sticky, and release chemical messengers; ADP causes more platelets to stick and release their contents

What is coagulation?

A set of reactions in which blood is transformed from a liquid to a gel; reinforces the platelet plug with fibrin threads

What is the intrinsic pathway?

Triggered by negatively charged surfaces (activated platelets, collagen, glass); uses factors present within the blood

What is the extrinsic pathway?

Triggered by exposure to tissue factor (TF) or factor III; bypasses several steps of the intrinsic pathway, so is faster

What is clot retraction?

Actin and myosin in platelets contract within 30–60 minutes; platelets pull on the fibrin strands, squeezing serum from the clot

How does repair proceed?

PDGF stimulates division of smooth muscle cells and fibroblasts to rebuild blood vessel wall; VEGF stimulates endothelial cells to multiply and restore the endothelial lining

How is blood kept thin?

Swift removal and dilution of clotting factors; inhibition of activated clotting factors

How are undesirable clots kept from forming?

Smooth endothelial lining of blood vessels; antithrombic substances nitric oxide and prostacyclin; vitamin E quinine

What is a thrombus?

Clot that develops and persists in an unbroken blood vessel

How can a thrombus be deleterious?

May block circulation, leading to tissue death

What is an embolus?

A thrombus freely floating in the bloodstream

What are effects of an embolus?

Pulmonary emboli impair the ability of the body to obtain oxygen; cerebral emboli can cause strokes

What are two ways to prevent thrombi?

Aspirin and heparin

What does aspirin do?

Antiprostaglandin that inhibits thromboxane A2

What does heparin do?

Anticoagulant used clinically for pre- and postoperative cardiac care

What is DIC?

Widespread clotting blocks intact blood vessels; severe bleeding occurs because residual blood is unable to clot

What is thrombocytopenia?

Deficient number of circulating platelets; petechiae appear due to spontaneous, widespread hemorrhage

How can one get a bleeding disorder?

Impaired liver function; inability to synthesize procoagulants; vitamin K deficiency, hepatitis, and cirrhosis

What is hemophilia?

Several similar hereditary bleeding disorders

What is hemophilia A?

Deficiency of factor VIII

What is hemophilia B?

Deficiency of factor IX

What is hemophilia C?

Deficiency of factor XI

What are the blood types?

Type A, Type B, Type AB, Type O

What are the RBC antigens for Type A?

A

What are the RBC antigens for Type B?

B

What are the RBC antigens for Type AB?

A and B

What are the RBC antigens for Type O?

None

What antibodies does Type A have?

Anti-B

What antibodies does Type B have?

Anti-A

What antibodies does Type AB have?

None

What antibodies does Type O have?

Anti-A and Anti-B

Who can Type A give blood to?

A and AB

Who can Type A receive blood from?

A and O

Who can Type B give blood to?

B and AB

Who can Type B receive blood from?

B and O

Who can Type AB give blood to?

AB