Hematopoiesis

1
Hematopoiesis

• Blood cell formation
• Occurs in red bone marrow
• Adult red marrow is found in ribs, vertebrae,
  sternum, pelvis, proximal humeri, and proximal
  femurs.

2
Hematopoiesis

• All blood cells are derived from a common stem
  cell (hemocytoblast)
• Hemocytoblast differentiation
• Lymphoid stem ?lymphocytes
• Myeloid stem cell ?all other formed elements

Figure 10.4
3
Formation of Erythrocytes

• Mature RBC are anucleate NO NUCLEUS. Therefore,
  Unable to divide, grow, or synthesize proteins
  ?Wear out in 100 to 120 days
• When worn out, RBCs are eliminated by phagocytes
  in the spleen or liver
• Lost cells are replaced by division of
  hemocytoblasts in the red bone marrow

4
Control of Erythrocyte Production
Rate is controlled by a hormone
(erythropoietin) Kidneys produce most
erythropoietin as a response to reduced oxygen
levels in the blood Homeostasis is maintained by
negative feedback from blood oxygen levels
Figure 10.5
5
Control of Erythrocyte Production
Figure 10.5, step 1
6
Control of Erythrocyte Production
Figure 10.5, step 2
7
Control of Erythrocyte Production
Figure 10.5, step 3
8
Control of Erythrocyte Production
Figure 10.5, step 4
9
Control of Erythrocyte Production
Figure 10.5, step 5
10
Control of Erythrocyte Production
Figure 10.5, step 6
11
Control of Erythrocyte Production
Figure 10.5, step 7
12
Control of Erythrocyte Production
Figure 10.5, step 8
13
Formation of White Blood Cells
Colony stimulating factors (CSFs) and
interleukins prompt bone marrow to generate
leukocytes
14
Formation of Platelets
The stem cell (megakaryocyte) undergoes mitosis
without cytokinesis many times, forming a large,
multinuclear cell, which then fragments into
platelets.
15
Hemostasis

• Stoppage of bleeding resulting from a break in a
  blood vessel
• Hemostasis involves three phases
• Vascular spasms
• Platelet plug formation
• Coagulation (blood clotting)

16
Hemostasis
Figure 10.6
17
Hemostasis- STEP 1

• Vascular spasms
• Vasoconstriction causes blood vessel to spasm
• Spasms narrow the blood vessel, decreasing blood
  loss

Figure 10.6, step 1
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Hemostasis- Step 2

• Platelet plug formation
• Collagen fibers are exposed by a break in a blood
  vessel
• Platelets become sticky and cling to fibers
• Anchored platelets release chemicals to attract
  more platelets
• Platelets pile up to form a platelet plug

Figure 10.6, step 2
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Hemostasis step 3

• Coagulation
• Injured tissues release tissue factor (TF)
• PF3 (a phospholipid) interacts with TF, blood
  protein clotting factors, and calcium ions to
  trigger a clotting cascade
• Prothrombin activator converts prothrombin to
  thrombin (an enzyme)

Figure 10.6, step 4
20
Hemostasis coagulation continued

• Thrombin joins fibrinogen proteins into hair-like
  molecules of insoluble fibrin
• Fibrin forms a meshwork (the basis for a clot)

Figure 10.6, step 7
21
Hemostasis

• Blood usually clots within 3 to 6 minutes
• The clot remains as endothelium regenerates
• The clot is broken down after tissue repair

Figure 10.7
22
Summary of hemostasis

• Hemostasis is initiated by a break in the blood
  vessel wall (or lining), initiating vascular
  spasms and causing platelets to cling to the
  damaged site. Once attached, the platelets
  release serotonin, which enhances
  vasoconstriction.
• Injured tissue cells release thromboplastin,
  which interacts with platelet phospholipids
  (PF3), Ca2 and plasma clotting factors to form
  prothrombin activator.
• Prothrombin activator converts prothrombin to
  thrombin. Thrombin, an enzyme, then converts
  soluble fibrinogen molecules into long fibrin
  threads, which form the basis of the clot.

23
Undesirable Clotting

• Thrombus
• A clot in an unbroken blood vessel
• Can be deadly in areas like the heart
• Embolus
• A thrombus that breaks away and floats freely in
  the bloodstream
• Can later clog vessels in critical areas such as
  the brain

Coagulation can be promoted by i. Roughened
vessel lining, which attracts/activates
platelets. ii. Pooling of blood within vessels
can result in the activation of clotting factors
and the initiation of the coagulation process.
24
Bleeding Disorders

• Thrombocytopenia
• Platelet deficiency
• Even normal movements can cause bleeding from
  small blood vessels that require platelets for
  clotting
• The liver is the source of fibrinogen and several
  other factors that are necessary for clotting.
  When the liver is damaged and dysfunctional, it
  becomes unable to synthesize the usual amounts of
  clotting factors. When this situation happens,
  abnormal and often severe bleeding episodes can
  occur
• Hemophilia
• Hereditary bleeding disorder
• Normal clotting factors are missing
• http//www.sciencecases.org/hemo/hemo.asp

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The Royal Disease
26
Review Questions 1

1. What is the name of the stem cell that gives rise
   to all other formed elements?
2. Name the formed elements that arise from myeloid
   stem cells. Name those arising from lymphoid
   stem cells.
3. What property of RBCs dooms them to a limited
   life span of only 120 days?
4. What WBC type resides primarily in the tissues of
   the body?
5. How is the production of platelets different from
   that of all other formed elements?
6. Describe the process of hemostasis. Indicate what
   starts the process.
7. What factors enhance the risk of thrombus
   formation in intact blood vessels?
8. How can liver dysfunction cause bleeding
   disorders?

27
Blood Groups and Transfusions

• Large losses of blood have serious consequences
• Loss of 1530 causes weakness
• Loss of over 30 causes shock, which can be fatal
• Transfusions are the only way to replace blood
  quickly
• Transfused blood must be of the same blood group

28
Human Blood Groups

• Blood contains genetically determined proteins
• Antigens (a substance the body recognizes as
  foreign) may be attacked by the immune system
• Antibodies are the recognizers
• Blood is typed by using antibodies that will
  cause blood with certain proteins to clump
  (agglutination)

29
Human Blood Groups

• There are over 30 common red blood cell antigens
• The most vigorous transfusion reactions are
  caused by ABO and Rh blood group antigens

30
ABO Blood Groups

• Based on the presence or absence of two antigens
• Type A
• Type B
• The lack of these antigens is called type O

31
ABO Blood Groups

• The presence of both antigens A and B is called
  type AB
• The presence of antigen A is called type A
• The presence of antigen B is called type B
• The lack of both antigens A and B is called type
  O

32
ABO Blood Groups

• Blood type AB can receive A, B, AB, and O blood
• Universal recipient
• Blood type B can receive B and O blood
• Blood type A can receive A and O blood
• Blood type O can receive O blood
• Universal donor

33
ABO Blood Groups
Table 10.3
34
Rh Blood Groups

• Named because of the presence or absence of one
  of eight Rh antigens (agglutinogen D) that was
  originally defined in Rhesus monkeys
• Most Americans are Rh (Rh positive)
• Problems can occur in mixing Rh blood into a
  body with Rh (Rh negative) blood
• Percentage of Population with Each Blood Type

  Rh Rh-
O 38.5 6.5
A 34.3 5.7
B  8.6 1.4
AB  4.3 0.7
35
Rh Dangers During Pregnancy

• Danger occurs only when the mother is Rh and the
  father is Rh, and the child inherits the Rh
  factor
• RhoGAM shot can prevent buildup of anti-Rh
  antibodies in mothers blood

36
Rh Dangers During Pregnancy

• The mismatch of an Rh mother carrying an Rh
  baby can cause problems for the unborn child
• The first pregnancy usually proceeds without
  problems
• The immune system is sensitized after the first
  pregnancy
• In a second pregnancy, the mothers immune system
  produces antibodies to attack the Rh blood
  (hemolytic disease of the newborn)

37
Blood Typing

• Blood samples are mixed with anti-A and anti-B
  serum
• Coagulation or no coagulation leads to
  determining blood type
• Typing for ABO and Rh factors is done in the same
  manner
• Cross matchingtesting for agglutination of donor
  RBCs by the recipients serum, and vice versa

Figure 10.8
38
Review Questions 2

• What are the classes of human blood groups based
  on?
• What are agglutinins?
• Name the four ABO blood groups.
• What is a transfusion reaction? Why does it
  happen?
• 10. What is the probable result from infusion of
  mismatched blood?
• 11. Cary is bleeding profusely after being hit
  by a truck as he was pedaling his bike home. At
  the hospital, the nurse asked him whether he knew
  his blood type. He told her he had the same
  blood as most other people. What is his ABO
  blood type?
• What is the difference between an antigen and an
  antibody?
• Explain why a Rh- person does not have a
  transfusion reaction on the first exposure to Rh
  blood? Why is there a transfusion reaction the
  second time he or she receives the Rh blood?