Lymphatic System Disorders
Lymphedema is an accumulation of interstitial fluid in tissues as a result of a blocked lymphatic vessel. Elephantiasis is a severe form of lymph- edema, caused by a mosquito-borne parasite that colonizes the lymphatic vessels. Lymphoma is a tumor of a lymph gland. Hodgkin’s disease is a type of lymphoma.
Because they provide passageways for mobile cells, lymphatic vessels provide a route for the spread of metastatic cancer cells, which may either take up residence in a lymph node or pass out of the lymphatic system to invade surrounding tissue.
For this reason, biopsy of nearby lymph nodes is often performed to determine whether a cancer has metastasized.
IMMUNE SYSTEM
The immune system involves the coordinated action of many cell types, along with the circulating pro- teins of antibodies and complement. In addition, it includes physical barriers to the entry of infection, such as the skin and the epithelial lining of the lungs, gut, and urinary tract.
Nonspecific Immunity
Nonspecific immunity refers to defense against in- fectious agents independent of the specific chemical
Cervical lymph nodes
Axillary lymph nodes Thymus
Thoracic duct Spleen Cisterna chyli
Inguinal lymph nodes Popliteal lymph nodes Red bone
marrow
Lymph vessels
Submandibular nodes Tonsils Right
lymphatic duct
Parasternal lymph nodes
FIGURE 7-13 The lymphatic system permeates the body, collecting interstitial fluid and returning it to the circulation. Lymph nodes are important components of the immune system. (From Patton KT, Thibodeau GA: The human body in health & disease, ed. 6, St. Louis, Mosby, 2014.)
markers on their surfaces. This includes physical barriers, the complement system, and phagocytes (monocytes and neutrophils), which engulf and destroy foreign cells without regard to their exact identity.
Inflammation is a coordinated, nonspecific de- fense against infection or irritation. It combines increased blood flow and capillary permeability, activation of macrophages, temperature increase, and the clotting reaction to wall off the infected area. These actions also activate the mechanism of specific immunity.
Specific Immunity
Specific immunity involves the molecular recogni- tion of particular markers, called antigens, on the surface of a foreign agent. Recognition of these antigens in the appropriate context triggers activa- tion of T and B cells, while also increasing the activity and accuracy of nonspecific defenses, such as complement and macrophages.
In one form of antigen recognition, antigens are taken up by a macrophage, which displays them on its surface in a receptor complex controlled by genes in the major histocompatibility complex (MHC). The proteins in these complexes are also known as human leukocyte antigens (HLAs). The antigen complex is presented to T cells, which are activated when they recognize the HLA–antigen combination. Activated T cells influence the pro- duction of both cytotoxic T cells, which recognize antigens and destroy both foreign and infected host cells, and memory T cells, which are primed to respond more rapidly if the antigen is encountered again later in life. Other T cells, called helper T cells, are important regulators of the entire immune response. They are needed to make both antibodies and cytotoxic T cells. Helper T cells are also known as T4 or CD41 cells, named after one of their sur- face receptors; these are the cells infected by human immunodeficiency virus (HIV). T cell–based im- munity is also called cellular immunity.
Antigens can be recognized in another way. An antigen can bind to an antibody, a product of a B cell. Each B cell makes an antibody of a slightly different shape, allowing recognition of an enor- mous variety of antigens. If the antibody shape is complementary to the antigen shape, it will activate the B cell under the influence of helper T cells and macrophages to undergo rapid cell division. Most of the offspring are plasma cells, which produce and release large numbers of antibodies into the lym- phatic system and, ultimately, into the circulation.
These antibodies bind to antigens at the site of in- fection and elsewhere, directly inactivating them;
they also act as flags for targeting by macrophages.
The remaining B-cell offspring become memory cells, which serve a similar function to memory T cells. This is the basis of immunization. Antibody- based immunity is also called humoral immunity, after humor, the antiquated term for a body fluid.
In addition to the direct contact between cells, immune cells communicate through cytokines, chemical messengers that include interferons and interleukins. Functionally, these molecules are hormones, released by one cell to influence the behavior of another.
Immune System Disorders
Autoimmunity is an attack by the immune system on the body’s own tissues. Autoimmune disorders include rheumatoid arthritis, systemic lupus ery- thematosus, myasthenia gravis, and multiple scle- rosis. Allergy is an inappropriately severe immune reaction to an otherwise harmless substance. Se- vere combined immune deficiency (SCID) is an inherited disorder marked by an almost total lack of B and T cells. Acquired immunodeficiency syndrome (AIDS) is caused by HIV infection.
REVIEW FOR CERTIFICATION
The pulmonary circulation carries blood between the heart and lungs for gas exchange, and the sys- temic circulation carries blood between the heart and the rest of the body’s tissues.
The heart is a muscular double pump located in the thoracic cavity. It is surrounded by the peri- cardium. The epicardium, myocardium, and endo- cardium are the three layers of the heart. Blood from the systemic circulation passes from the venae cavae into the right atrium and through the tricuspid valve into the right ventricle. From there, blood passes out through the pulmonary semilunar valve, through the pulmonary trunk, into the left and right pulmonary arteries, and on to the lungs. It returns via the pulmonary veins to the left atrium and then through the mitral valve into the left ventricle.
It passes out through the aortic semilunar valve into the aorta, which branches to form the major arteries. Arteries branch further into arterioles, which lead to capillary beds within the tissues, where oxygen exchange occurs. Blood then enters venules and veins, which empty into the venae cavae. Blood pressure is higher in the arteries than in the veins. Arteries are thick and muscular; veins
are thinner and contain valves to prevent backflow.
Capillaries are composed of a single layer of endo- thelial cells.
Blood is composed of plasma and cellular com- ponents. RBCs carry hemoglobin. WBCs protect the body against infection. There are five types of WBCs: neutrophils, eosinophils, basophils, lym- phocytes, and monocytes. Platelets play a critical role in blood coagulation. Serum is plasma minus its clotting factors. Hemostasis occurs in four phases: the vascular phase (muscular contraction of the vessel walls), the platelet phase, the coagulation phase (clot formation), and fibrinolysis (removal of
the clot). The coagulation phase includes the intrin- sic and extrinsic pathways, which unite to enter the common pathway.
The lymphatic system returns interstitial fluid to the circulatory system through lymphatic ducts, screening it for signs of infection at lymph nodes.
Lymph organs include the tonsils, the spleen, and the thymus.
Nonspecific immunity includes physical barriers, the complement system, inflammation, and phago- cytes. Specific immunity involves recognition of an- tigens, which triggers activation of T cells (cellular immunity) and B cells (humoral immunity).
BI BLIOG R AP HY
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STUDY QUESTIONS
See answers in Appendix F.
1. Describe the different functions of the circulatory system.
2. Discuss the difference between pulmonary and systemic circulation.
3. Explain the functional difference between veins and arteries.
4. Name the four valves of the heart.
5. Contraction of the heart is known as ________, and relaxation is known as ___________.
6. Name the three layers surrounding the lumen of veins and arteries.
7. The yellow liquid portion of whole blood, containing fibrinogen, is known as ___________.
8. The formed elements constitute __________% of blood volume.
9. What is the role of a phagocyte?
10. Which type of lymphocyte produces antibodies?
11. Describe the two pathways in the coagulation cascade.
12. Define and give an example of autoimmunity.
13. Describe the lymph organs and their functions. Give one lymphatic system disorder, and explain its due process.
14. Name the types of immunity, how they differ, and how they are similar.
15. Explain the function of enzymes in the coagulation process.
See answers in Appendix F.
1. In the circulatory system, gas exchange occurs in the
a. capillaries.
b. veins.
c. arteries.
d. venules.
2. Which blood vessels are a single cell in thickness?
a. Capillaries b. Veins c. Arteries d. Arterioles
3. Veins and arteries are composed of how many layers?
a. 1 b. 2 c. 3 d. 4
4. A characteristic of arteries is
a. they are composed of a single layer of endothelial cells.
b. they have a thick muscle layer lining the lumen.
c. they have valves along the lumen.
d. they carry blood toward the heart.
5. An average adult has _______ L of blood.
a. 1 to 2 b. 3 to 4 c. 5 to 6 d. 7 to 8
6. Plasma constitutes _______ % of total blood volume.
a. 45 b. 55 c. 80 d. 92
7. Another name for a WBC is a. leukocyte.
b. reticulocyte.
c. erythrocyte.
d. electrolyte.
8. The main function of leukocytes is to a. transport hemoglobin.
b. transport lipids.
c. protect the body against infection.
d. recycle RBCs.
9. Which leukocyte is known as a phagocyte?
a. Lymphocyte b. Neutrophil c. Eosinophil d. Basophil
10. Platelets remain in the circulation for a. 2 to 5 days.
b. 9 to 12 days.
c. 10 to 20 days.
d. 1 month.
11. Which cellular component is responsible for the transport of hemoglobin?
a. WBCs b. RBCs c. Electrolytes d. Plasma
12. Which laboratory test does not assist in diagnosing HIV infection?
a. Western blot b. T-cell count c. aPTT
d. Anti-HIV antibody
13. A group of inherited disorders marked by increased bleeding times is known as
a. anemias.
b. leukemias.
c. polycythemias.
d. hemophilias.
14. Which organ is not included in the lymphatic system?
a. Liver b. Spleen c. Thymus d. Tonsils
15. Helper T cells are needed to make a. antigens.
b. antibodies.
c. cytokines.
d. interleukins.
CERTIFICATION EXAMINATION PREPARATION
113
Specimen Collection
UNIT 3
CHAPTER 8
Venipuncture Equipment
Anticoagulants Clot Activators Polymer Gel Color-Coded Tops Order of Draw
Needle Disposal Containers Review for Certification Phlebotomy Equipment
Organizing and Transporting Equipment
Locating Veins
Cleaning the Puncture Site Protecting the Puncture Site Needles
Features of Needles Multisample Needles
Safety Syringes and Safety Sy- ringe Needles
Winged Infusion Sets or But- terflies
Needle Safety Needle Adapters
Evacuated Collection Tubes Types of Blood Specimens Tube Additives
OUTLI N E
E
quipment for routine venipuncture includes materials needed for the safe and efficient lo- cation of a vein and collection of a blood sample, plus equipment to ensure the safety and comfort of both the patient and the user. Most venipuncture procedures are performed with a double-endedmultisample needle that delivers blood into an evacuated tube with a color-coded stopper. The stopper indicates the additives used in the tube.
Learning what each color signifies, and in what order different-colored tubes should be drawn, is essential for a phlebotomist.
1. List the equipment that should be available for venipuncture.
2. Describe the purpose of a tourniquet, and list types that may be used to locate a vein.
3. Differentiate between an antiseptic and a disinfec- tant, and list those that may be used for blood collection.
4. Locate the bevel, shaft, hub, and point of a needle, and describe safety features that may be included.
5. Define needle gauge, and explain the use of different gauges.
6. Name the parts of a syringe, and describe how the syringe system differs from the evacuated tube system.
OBJ ECTIVE S
7. Explain when a syringe system or winged infusion set (butterfly) is used in blood collection.
8. Describe the proper use of the tube holder (needle adapter).
9. Differentiate whole blood, serum, and plasma, and list at least one use for each.
10. Describe at least nine additives, including their mode of action and uses.
11. List at least 10 colors for tube tops. Identify the additive(s) in each, and state one use for each.
12. State the correct order of draw for both evacuated tube collection and syringe collection.
13. Describe the proper disposal of a used needle.
After completing this chapter, you should be able to:
KEY TE R M S
additives antiseptic bacteriostatic butterfly clot activators disinfectant
gauge glycolysis inpatients Luer adapter lumen
multisample needle
needle adapter order of draw outpatients polymer gel thixotropic gel tourniquet
tube advancement mark tube holder
whole blood winged infusion set
MRSA methicillin-resistant Staphylococcus aureus OSHA Occupational Safety and Health Administration PSTs plasma separator tubes
RBCs red blood cells
SPS sodium polyanetholesulfonate SSTs serum separator tubes stat short turnaround time
ABBR EVIATION S
ABGs arterial blood gases CBC complete blood count
CDC Centers for Disease Control and Prevention CLSI Clinical and Laboratory Standards Institute EDTA ethylenediaminetetraacetic acid
FBS fasting blood sugar (glucose) HLA human leukocyte antigen