Blood functions to transport gases, nutrients, waste products, regulatory molecules, and protects the body. It is composed of plasma and formed elements including red blood cells, white blood cells, and platelets. Red blood cells contain hemoglobin and transport oxygen and carbon dioxide. White blood cells protect against pathogens and remove dead cells. Platelets help form blood clots to prevent blood loss from injuries. Blood typing involves antigens on red blood cells and antibodies in plasma to avoid transfusion reactions.

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Chapter 16
Blood
Blood Clot

2. Functions and Composition of Blood
• Blood helps maintain homeostasis in
several ways:
1.Transport of gases, nutrients, waste products
2.Transport of processed molecules
3.Transport of regulatory molecules
4.Regulation of pH and osmosis
5.Maintenance of body temperature
6.Protects against foreign substances such as
microorganisms and toxins
7.Blood clotting prevents fluid and cell loss and
is part of tissue repair

3. Functions and Composition of Blood
• Blood is a connective tissue consisting of
plasma and formed elements
• Blood is the body’s only fluid tissue
• It is composed of liquid plasma and formed
elements
• Formed elements include:
– Erythrocytes, or red blood cells (RBCs)
– Leukocytes, or white blood cells (WBCs)
– Platelets
• Hematocrit: the percentage of RBCs out of the
total blood volume

4. Functions and Composition of
Blood
• Total blood
volume is
approximately
5 liters
Fig. 16.1

5. Functions and Composition of Blood
• Blood is a sticky, opaque fluid with a
metallic taste
• Color varies from scarlet to dark red
• The pH of blood is 7.35–7.45
• Temperature is 38C
• Blood accounts for approximately 8% of
body weight
• Average volume: 5–6 L (1.5 gallons) for
males, and 4–5 L for females

6. Plasma
• Pale yellow fluid containing over 100 solutes
• Mostly water (91%)
• Contains proteins (7%)
– Albumin (58% of the plasma proteins)
• Helps maintain osmotic pressure
– Globulins (38% of the plasma proteins)
• Immunity: antibodies and complement
• Transport: bind to molecules such as hormones
• Clotting Factors
– Fibrinogen (4% of the plasma proteins)
• Converted to fibrin during clot formation
• Other substances (2%)
– Ions (electrolytes): sodium, potassium, calcium, chloride,
bicarbonate
– Nutrients: glucose, carbohydrates, amino acids
– Waste products: lactic acid, urea, creatinine
– Respiratory gases: oxygen and carbon dioxide

7. Plasma
Tab. 16.1

8. Formed Elements
• Erythrocytes or red blood cells (RBCs)
– About 95% of formed elements
– RBCs have no nuclei or organelles
• Leukocytes or white blood cells (WBCs)
– Most of the remaining 5% of formed elements
– Only WBCs are complete cells
– Five types of WBCs
• Platelets
– Just cell fragments
• Most formed elements survive in the bloodstream
for only a few days

9. Tab. 16.2

10. Production of Formed Elements
• Most blood cells do not divide but are renewed
by stem cells (hemocytoblasts) in bone marrow
• Hematopoiesis: blood cell production
– Occurs in different locations before and after birth
• Fetus
– Liver, thymus, spleen, lymph nodes, and red bone marrow
• After birth
– In the red bone marrow of the
» Axial skeleton and girdles
» Epiphyses of the humerus and femur
– Some white blood cells are produced in lymphatic tissues
• Hemocytoblasts give rise to all formed elements
– Growth factors determine the type of formed element
derived from the stem cell

11. Fig. 16.2
Hematopoiesis

12. Red Blood Cells
• Biconcave discs, anucleate, essentially no organelles
• RBCs are dedicated to respiratory gas transport
– Filled with hemoglobin (Hb), a protein that functions in gas
transport
• RBCs are an example of how structure fits function
– Biconcave shape has a huge surface area relative to volume
• Structural characteristics contribute to its gas transport function
– Biconcave shape also allows RBCs to bend or fold around their
thin center
• Gives erythrocytes their flexibility
• Allow them to change shape as necessary

13. Fig. 16.3

15. Red Blood Cells
• Hemoglobin (Hb)
– Accounts for about a third of the cell’s volume
– Consists of
• The protein globin, made up of two alpha and two beta
chains, each bound to a heme group
• Each heme group bears an atom of iron, which can bind to
one oxygen molecule
• Heme molecules transport oxygen (Iron is required)
– Oxygen content determines blood color
» Oxygenated: bright red
» Deoxygenated: darker red
• Globin molecules transport carbon dioxide
• One RBC contains 250 million Hb groups thus it
can carry 1 billion molecules of O2

16. Hemoglobin
Fig. 16.4

17. Red Blood Cells
• Transport of Oxygen and Carbon Dioxide
– Oxygen
• Transported bound to hemoglobin ~98.5%
• Dissolved in plasma ~1.5%
• Each Hb molecule binds four oxygen atoms in a
rapid and reversible process
– Carbon dioxide
• Dissolved in plasma ~7%
• Transported as bicarbonate(HCO3
–) ~70%
• Chemically bound to hemoglobin ~23%

18. • Transport and Exchange of Carbon Dioxide
– Carbon dioxide diffuses into RBCs and combines with
water to form carbonic acid (H2CO3), which quickly
dissociates into hydrogen ions and bicarbonate ions
•
– In RBCs, carbonic anhydrase reversibly catalyzes the
conversion of carbon dioxide and water to carbonic
acid
CO2 + H2O  H2CO3  H+ + HCO3
–
Carbon
dioxide
Water
Carbonic
acid
Hydrogen
ion
Bicarbonate
ion
Red Blood Cells

19. Red Blood Cells
• Erythropoiesis is the production of RBCs
– A hemocytoblast is transformed into a
proerythroblast
– Proerythroblasts develop into early erythroblasts
– The developmental pathway consists of three
phases
1. Ribosome synthesis in early erythroblasts
2. Hb accumulation in intermediate erythroblasts and
late erythroblasts
3. Ejection of the nucleus from late erythroblasts and
formation of reticulocytes
– Reticulocytes are released from the red bone marrow
into the circulating blood, which contains ~1-3%
reticulocytes
– Reticulocytes then become mature erythrocytes

20. Red Blood Cell Production
• Circulating erythrocytes: The number remains constant
and reflects a balance between RBC production and
destruction
– Too few RBCs leads to tissue hypoxia
– Too many RBCs causes undesirable blood viscosity
• Erythropoiesis is hormonally controlled and depends on
adequate supplies of iron, amino acids, and B vitamins
(folate and B12)
– Erythropoietin (EPO) release by the kidneys is triggered by
• Hypoxia due to decreased RBCs
• Decreased oxygen availability
• Increased tissue demand for oxygen
– Enhanced erythropoiesis increases the
• RBC count in circulating blood
• Oxygen carrying ability of the blood

21. Red Blood Cell Production
Fig. 16.5

22. Red Blood Cells
• The life span of an erythrocyte is 100–120 days
• Old RBCs become rigid and fragile, and their Hb begins to
degenerate
• Dying RBCs are engulfed by macrophages located in the
spleen or liver
• Heme and globin are separated and the iron is salvaged
for reuse
– Globin chains are broken down to individual amino acids and are
metabolized or used to build new proteins
– Iron released from heme is transported to the red bone marrow
and is used to produce new hemoglobin
– Heme becomes bilirubin that is secreted in bile
• In the intestines bilirubin is converted by bacteria into other pigments
– Gives feces its brown color
– Gives urine its yellow color

23. Hemoglobin Breakdown
Fig. 16.6

25. White Blood Cells
• Only blood components that are complete cells
• Are less numerous than RBCs
• Make up 1% of the total blood volume
• Can leave capillaries via ameboid movement and move
through tissue spaces
• Two functions of WBCs
– Protect the body against invading microorganisms
– Remove dead cells and debris from tissues by phagocytosis
• Named according to their appearance in stained
preparations
– Granulocytes: contain large cytoplasmic granules
– Agranulocytes: very small granules that cannot be easily seen
with the light microscope

26. White Blood Cells
• Granulocytes: neutrophils, eosinophils,
and basophils
– Contain cytoplasmic granules that stain
specifically (acidic, basic, or both) with
Wright’s stain
– Are larger and usually shorter-lived than
RBCs
– Have lobed nuclei
– Are all phagocytic cells

27. White Blood Cells
• Neutrophils most common type of WBC
– Have two types of granules that:
• Take up both acidic and basic dyes
• Give the cytoplasm a lilac color
• Contain peroxidases, hydrolytic enzymes, and
defensins (antibiotic-like proteins)
• Neutrophils are our body’s bacteria slayers
• Pus is an accumulation of dead
neutrophils, cell debris and fluid at sites of
infections

28. White Blood Cells
• Basophils account for 0.5% of WBCs
– Have large, purplish-black (basophilic)
granules that contain
• Histamine: inflammatory chemical that acts as a
vasodilator and attracts other WBCs
(antihistamines counter this effect)
• Heparin: prevents the formation of clots

29. White Blood Cells
• Eosinophils account for 1–4% of WBCs
– Have red-staining, bilobed nuclei connected
via a broad band of nuclear material
– Have red to crimson (acidophilic) large,
coarse, lysosome-like granules
– Lessen the severity of allergies by reducing
inflammation
– Lead the body’s counterattack against
parasitic worms

30. White Blood Cells
• Agranulocytes: lymphocytes and
monocytes
– Lack visible cytoplasmic granules
– Are similar structurally, but are functionally
distinct and unrelated cell types
– Have spherical (lymphocytes) or kidney-
shaped (monocytes) nuclei

31. White Blood Cells
• Lymphocytes account for 25% or more of WBCs
– Have large, dark-purple, circular nuclei with a thin rim
of blue cytoplasm
– Are found mostly enmeshed in lymphoid tissue (some
circulate in the blood)
• There are two types of lymphocytes: T cells and
B cells
– B cells
• Stimulated by bacteria or toxins
• Give rise to plasma cells, which produce antibodies
– T cells
• Protect against viruses and other intracellular
microorganisms
• Attack and destroy the cells that are infected

32. White Blood Cells
• Monocytes account for 4–8% of
leukocytes
– They are the largest leukocytes
– They have an abundant pale-blue cytoplasm
– They have purple-staining, U- or kidney-
shaped nuclei
– They leave the circulation, enter tissue, and
differentiate into macrophages
• Are highly mobile and actively phagocytic
• Activate lymphocytes to mount an immune
response

33. Tab. 16.2

34. Fig. 16.7

35. Identification of WBCs
Fig. 16.8

36. Platelets
• Fragments of megakaryocytes with a
blue-staining outer region and a purple
granular center
• Function in clotting by two mechanisms
1. Formation of platelet plugs, which seal holes
in small vessels
2. Formation of clots, which help seal off larger
wounds in the vessels
• Their granules contain ADP and
thromboxanes

37. Preventing Blood Loss
• A series of reactions for stoppage of
bleeding
• Three phases occur in rapid sequence
– Vascular spasms: immediate vasoconstriction
in response to injury
• Thromboxanes and endothelin can cause vascular
spasms
– Platelet plug formation
– Coagulation (blood clotting)

38. Preventing Blood Loss
• Platelet Plugs
– Platelets do not stick to each other or to blood vessels
– Upon damage to blood vessel endothelium platelets:
• With the help of von Willebrand factor (VWF) adhere to
collagen
• Are stimulated by and then release more thromboxane and
ADP, which attract still more platelets
• Stick to exposed collagen fibers and form a platelet plug
– The platelet plug is limited to the immediate area of
injury by prostacyclin
– Can seal up a small breaks in a blood vessels that
occur many times each day

39. Platelet Plug Formation
Fig. 16.9

40. Blood Clotting
• Blood clotting, or coagulation, is the
formation of a clot (a network of protein
fibers called fibrin)
• Blood clotting begins with the extrinsic or
intrinsic pathway
– Both pathways end with the production of
activated factor X
• Extrinsic pathway begins with the release of
thromboplastin from damaged tissue
• Intrinsic pathway begins with the activation of
factor XII

41. Blood Clotting
• Activated factor X, factor V, phospholipids, and
Ca2+ form prothrombinase
• Prothrombin is converted to thrombin by
prothrombinase
• Fibrinogen is converted to fibrin by thrombin
– Insoluble fibrin strands form the structural basis of a clot
– Fibrin causes plasma to become a gel-like trap
– Fibrin in the presence of calcium ions activates factor XIII
that:
• Cross-links fibrin
• Strengthens and stabilizes the clot
• Away from the site of injury anticoagulants in the
blood, such as antithrombin and heparin, prevent
clot formation

42. Fig.
16.10

43. Clot Retraction and Fibrinolysis
• Clot retraction: stabilization of the clot by
squeezing serum from the fibrin strands
– Results from the contraction of platelets,
which pull the edges of damaged tissue closer
together
– Serum, which is plasma minus fibrinogen and
some clotting factors, is squeezed out to the
clot
• Thrombin and tissue plasminogen
activator activate plasmin, which dissolves
fibrin (fibrinolysis)

44. Fig.
16.11

45. Blood Grouping
• RBC membranes have glycoprotein antigens on
their external surfaces
• These antigens are:
– Unique to the individual
– Recognized as foreign if transfused into another
individual
– Promoters of agglutination and are referred to as
agglutinogens
• Presence or absence of these antigens is used
to classify blood groups

46. Blood Grouping
• Transfusion reactions occur when
mismatched blood is infused
• Antibodies can bind to the donor’s RBC
antigens, resulting in agglutination or
hemolysis of RBCs, leading to
– Diminished oxygen-carrying capacity
– Clumped cells that impede blood flow
– Ruptured RBCs that release free hemoglobin
into the bloodstream

47. ABO Blood Group
• The ABO blood groups consists of:
– Two antigens (A and B) on the surface of the RBCs
– Two antibodies in the plasma (anti-A and anti-B)
Blood type Antigens Present Antibodies Present
A B Anti-A Anti-B
AB + + – –
B – + + –
A + – – +
O – – + +

48. Fig.
16.12

49. Agglutination Reaction
Fig. 16.13

51. Rh Blood Group
• Rh-positive blood has certain Rh antigens
(the D antigen), whereas Rh-negative
blood does not
• Antibodies against the Rh antigen are
produced when a Rh-negative person is
exposed to Rh-positive blood
• The Rh blood group is responsible for
hemolytic disease of the newborn, which
can occur when the fetus is Rh-positive
and the mother is Rh-negative

52. Fig. 16.14
Hemolytic
Disease
of the
Newborn
(HDN)

53. Diagnostic Blood Tests
• Laboratory examination of blood can
assess an individual’s state of health
• Microscopic examination:
– Variations in size and shape of RBCs:
prediction of anemia
– Type and number of WBCs: diagnostic of
various diseases
• Chemical analysis can provide a
comprehensive picture of one’s general
health status in relation to normal values

54. Diagnostic Blood Tests
• Red blood cell count
(million/mL)
– Male 4.6-6.2 million/mL
– Female 4.2-5.4 million/mL
• Hemoglobin
measurement (grams of
hemoglobin per/mL of
blood
– Male 14-18 g/100mL
– Female 12-16 g/100mL
• Hematocrit measurement
(percent volume of RBCs)
– Male 40%-52%
– Female 38%-48%
• White blood cell count
(WBCs/mL)
– Male and Female 5000-
9000 WBCs/mL
• Differential white blood
cell count (the percentage
of each type of WBC)
– Neutorphils – 60%-70%
– Lymphocytes – 20%-25%
– Monocytes – 3%-8%
– Eosinophils – 2%-4%
– Basophils – 0.5%-1%
The complete blood count consists of the following

55. Fig.
16.15

56. Diagnostic Blood Tests
• Clotting
– Platelet count and prothrombin time measure the
ability of the blood to clot
• Blood Chemistry
– The composition of materials dissolved or suspended
in plasma can be used to assess the functioning and
status of the body’s systems
• Glucose
• Urea
• Nitrogen
• Bilirubin
• Cholesterol