Chapters 12 Blood & the Cardiovascular System Human Anatomy & Physiology P. Wilson1

Human Anatomy & Physiology P. Wilson 1

Chapters 12Blood & the Cardiovascular System


II. 12.1 IntroductionThe functions of the blood are:• to transport nutrients, oxygen, wastes, & hormones• to help maintain the stability of interstitial fluid (the fluid

between cells)• to distribute heat• to transport substances between body cells & the external

environment (helping to maintain homeostasis)


III. 12.2 A. Blood & Blood Cells1. The solid elements of blood (aka “formed” elements)are:

• red blood cells (RBCs)• white blood cells (WBCs)• platelets

2. The blood volume of an average sized male is 5 liters. • males have more blood than females (1.500 gallons to 0.875 gallons)

3. Plasma (a clear, straw-colored liquid) makes up about 55% of blood.

4. Plasma consists of water, amino acids, carbohydrates, lipids, vitamins, hormones, electrolytes, & cellular wastes


III. 12.2 B. Blood & Blood CellsRed Blood Cells

1. The shape of RBCs is a biconcave disc

2. The shape is an adaptation for transporting gases – it increases the surface area through which gases can diffuse.



3. The color of an RBC is due to the presence of hemoglobin (makes up about 1/3 of the cell’s volume).

• Red blood cells are bright red when carrying oxygen (oxygen-rich) because that is the color of oxyhemoglobin;

• deoxyhemoglobin is formed when the oxygen has been released (oxygen-poor blood) and it is a darker red color.



4. Mature RBCs lack a nucleus. • the main function of RBCs is to carry oxygen so once the RBC has

completed development the nucleus is extruded, providing more space for hemoglobin

The average life span of a RBC is 120 days.The combined surface area of all the RBCs in the human body is roughly 200 times as great as the body’s exterior surface!


III. 12.2 C. Blood & Blood CellsRed Blood Cell Counts

1. The typical red blood cell count is 4,600,000-6,2000,000 cells per mm3 for males and 4,500,000-5,100,000 cells per mm3 for females.

2. When prolonged exposure to low oxygen levels are experienced, the kidneys & liver release the hormone erythropoietin which stimulates hematopoiesis (production of RBCs)


III. 12.2 C. Blood & Blood Cells

Red Blood Cell Counts

3. Dietary factors that influence the production of RBCs are • folic acid & vitamin B – essential for DNA synthesis; new

blood cells are constantly being produced to replace worn out & damaged cells – DNA is necessary for the cell production

• iron – essential for the production of hemoglobin




4. RBCs are produced• in the early embryo & fetus, RBCs are produced in the yolk sac• in late fetal stages, RBCs are produced in the liver & spleen• after birth, RBCs are produced in red bone marrow




5. RBC production is controlled by negative feedback using the hormone erythropoietin. The kidneys & liver release erythropoietin in response to prolonged oxygen deficiency.1) Oxygen deficiency is detected2) Kidneys & liver release erythropoietin which travels to target cells in red bone

marrow3) Erythropoiesis begins & within a few days new RBCs appear in circulating

blood4) Oxygen levels increase; when “normal” set point is reached, erythropoietin

release decreases & the rate of RBC production returns to normal



Red Blood Cell Counts6. In individuals affected with sickle-cell anemia, a single DNA base

change causes an incorrect amino acid to be added to the globin protein chain. The defective hemoglobin crystallizes in a low oxygen environment, causing the RBCs to bend into a sickle shape.• The sickle-shaped cells cause circulation blockage in small blood vessels

causing joint pain and damaging organs




III. 12.2 D. Destruction of RBCs

1. As RBCs age they become less elastic, less flexible, & more fragile and are damaged as they pass through capillaries.

2. Damaged RBCs are phagocytized (destroyed) by macrophages located in the spleen and liver.• The hemoglobin breaks down into heme (the iron-containing portion)

and globin (the protein potion). • The heme is further decomposed into biliverdin (a green pigment)

bilirubin (an orange pigment) which are excreted in bile• the iron from hemoglobin may be transported to the red bone marrow

tissue responsible for hematopoiesis to be reused in the production of RBCs


III. 12.2 E. Types of WBCs


Types of White Blood Cells aka Leukocytes

White blood Cell Description % of Total Function

Granulocytes Have granular cytoplasm (3 types). About twice the size of RBCs

Develop in red bone marrow. Life span about 12 hours

Neutrophil lobed nucleus (2-5 lobes) 54-62% of WBC

Most mobile & active of the phagocytes; ingest bacteria

Eosinophil bi-lobed nucleus 1-3% of WBCs

Weakly phagocytic; attracted to & lethal to certain parasites; helps control inflammation & allergic reactions

Basophil Similar appearance to eosinophils

<1% of WBCs

Releases heparin (prevents clots) and histamine (increases blood flow to injuries); histamines play major roles in allergic reactions

Normal WBC count is 5000 – 10000 per mm3

Functions: destroy pathogenic microorganisms & parasites, and remove worn out cells


Types of White Blood Cells aka Leukocytes

White blood Cell Description % of Total Function

Agranulocytes Cytoplasm lacks granules

Monocyte Largest WBC (2-3x size of RBC)Nuclei vary in shape

3-9% of WBC

Aka macrophage; phagocytize large particles (ex: foreign proteins)Life span: several weeks to months

Lymphocyte Slightly larger than RBC; large, round nucleus & small rim of cytoplasm

25-33% of WBCs

Produce antibodies that attack specific foreign substances.Life span: years


III. 12.2 F. WBC Counts

1. Normal WBC count is 5000 – 10000 per mm3.

2. Causes of WBC count changes:• Leukocytosis (> 10000 per mm3) indicates an acute infection such as

appendicitis• Leukopenia (< 5000 per mm3) may indicate measles, mumps, typhoid

fever, influenza, AIDS, or poliomyelitis.


III. 12.2 F. WBC Counts

3. A differential WBC count list the percentages of the various types of leukocytes. The relative proportions of WBCs help with diagnoses. • Ex: increase in neutrophils indicates a bacterial infection, while an

increase in eosinophils indicates the presence of a parasite or an allergen.


III. 12.2 G. Platelets

• Platelets (aka thrombocytes) arise from large cells in the marrow called megakaryocytes.. The megakaryocytes shatter into small fragments (platelets) that contain cytoplasm but no nucleus.

• Megakaryocytes & platelets increase in numbers in response to the hormone thrombopoietin.

• Platelets move like an amoeba, have a life span of about 10 days, and play a vital role in blood clotting.


IV. 12.3 Blood Plasma

Protein Description % of Total Function

Albumins • Smallest of the plasma proteins• Synthesized in the liver

60% Helps maintain osmotic pressure

Globulins • alpha & beta are synthesized in the liver • gamma- synthesized in lymphatic tissue

36% • alpha & beta: transport of lipids & fat-soluble vitamins

• gamma- these are antibodiesFibrinogen • Largest of the plasma proteins

• synthesized in lymphatic tissue4% Blood coagulation

A. Plasma Proteins


IV. 12.3 B. Blood Plasma: Nutrients & Gases

1. Oxygen, nitrogen, carbon dioxide are the gases found on blood plasma.

2. The nutrients found in blood plasma are amino acids, simple sugars, nucleotides, & lipids.

3. Non-protein nitrogenous substances found in plasma are amino acids, urea, & uric acid (these are products of protein & nucleic acid digestion)• Levels of these substances in the plasma can be used as a measure

of kidney & liver function.


IV. 12.3 C. Blood Plasma: Electrolytes

1. Sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, & sulfate ions are the electrolytes found in blood plasma.• Sodium and chloride ions are the most abundant ions in plasma

2. The function of electrolytes is to regulate the acid-base balance and they have role in nerve and muscle function.


V. 12.4 HemostasisA. The mechanisms of hemostasis, or stoppage of bleeding,

are:• vasospasm – cutting a blood vessel causes the muscle in its walls to

contract in a reflex, or engage in vasospasm. This reflex lasts only a few minutes, but it lasts long enough to initiate the 2nd & 3rd steps of hemostasis.

• platelet plug formation - platelets stick to the exposed edges of damaged blood vessels (and to each other), forming a net with spiny processes protruding from their membranes; a platelet plug is most effective on a small vessel.

• blood coagulation - is the most effective means of hemostasis & is a very complex process using clotting factors

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V. 12.4 Hemostasis

C. Major events in the blood-clotting mechanism:• in the presence of calcium, prothrombin converts to thrombin

• thrombin catalyzes the conversion of fibrinogen to long strands of fibrin

• fibrin sticks to exposed surfaces of blood vessels forming a mesh to trap other blood elements (WBCs, RBCs, & platelets).

• the mass formed is a blood clot.


V. 12.4 Hemostasis

D. Normal blood flow prevents the concentration of thrombin from too low to cause clotting.• When blood flow is diminished or when blood pools, the

concentration of thrombin increases and can lead to a blood clot or a thrombus.

E. Thrombi & emboli can be formed • A thrombus is a blood clot abnormally formed in a blood vessel

that is not moving.• An embolus is a fragment of a clot that breads off & is carried

away by blood flow.


V. 12.4 Hemostasis

E. Thrombus vs embolus:• A thrombus is a blood clot abnormally formed in a blood vessel that

is not moving.• An embolus is a fragment of a clot that breads off & is carried away

by blood flow.

Thrombi or emboli can be formed under any of the following circumstances:

• atrial fibrillation (the most common type of cardiac arrhythmia – rate or rhythm of heartbeat)

• incompetent venous valves• immobility• the formation of plaques in atherosclerosis


VI. 12.5 Blood Groups & TransfusionsA. Agglutinogens & Agglutinins

1. Antigens (Agglutinogens) are molecules on the surface of RBCs that determine the ABO blood type. Antibodies (agglutinins) are molecules found in the plasma that react with antigens, and if incompatible, will “clump” together (or agglutinate).Note: ABO antibodies form in an infants blood within 2 to 8 months following

birth. These antibodies are specific for blood type. Whenever A antigen is absent from the body anti-A antibodies form; when B antigen is absent, anti-B antibodies form.

2. Agglutinogens are on the surface of RBCs; agglutinins on in the plasma.


VI. 12.5 Blood Groups & Transfusions

B. ABO Blood Group

1. The presence, or lack, of specific antigens determine blood type:• A antigen only – type A blood• B antigen only – type B blood• both A & B antigens - type AB blood• Neither A nor B antigen – type O blood

2. If incompatible antigens and antibodies are mixed “clumping” and transfusion reactions can occur (may have serious & life threatening consequences – see blue box on p. 317)



C. Rh Blood Group

1. There are several Rh antigens that determine if a blood type is Rh+ or Rh-. The most important is antigen D.

2. Anti-Rh antibodies do not form spontaneously. Anti-Rh antibodies form only in Rh- individuals in response to stimulation (through exposure to Rh antigen).





3. Rh Blood Group

Erythoblastosis fetalis occurs when a woman who has already developed anti-Rh antibodies (previous exposure) becomes pregnant with an Rh+ fetus. The woman’s antibodies will cross the placental membrane & destroy the fetal red blood cells.

This condition is rare today because physicians carefully track Rh status of pregnant females. A Rh- female who might carry a Rh+ fetus is given a RhoGAM shot. Antibodies in the injection bind to & shield any Rh+ fetal cells.

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Chapters 12 Blood & the Cardiovascular System Human Anatomy & Physiology P. Wilson1