LYMPHATIC CIRCULATION
Lymph only carries fluid away from tissues. The initial lymphatics (the prelymphatics, lymph capillaries) drain into larger lymph vessels. As discussed earlier, the lymphatic system does not have a pumping system of its own. The lymph from the upper right quadrant of the body drains into the right lymphatic duct. The remainder of the body’s lymph drains into the left lymphatic duct, commonly known as the thoracic duct. The right lymphatic duct and the thoracic duct then drain into the left subclavian vein at the base of the neck, where lymph mixes with blood plasma and becomes part of the general circulation.
Lymph enters lymph nodes through several afferent (“bringing toward”) lymph vessels. The lymph nodes filter out dangerous substances (e.g., cancer cells and bacteria), dead RBCs, and foreign matter (e.g., smoke by-products) that become trapped in the nodes. The lymph then continues to flow away from the node through one or two efferent (“taking away”) lymph vessels into the bloodstream. Plasma cells and lymphocytes that have reproduced within a lymph node can also be added to lymph for transportation to the blood.
TABLE 23-3. Effects of Aging on the Hematologic and Lymphatic Systems
|
FACTOR |
RESULT |
NURSING IMPLICATIONS |
|
Stem cells and marrow reserves decrease |
Increased vulnerability to problems with clotting, oxygen transport, and fighting infection Decreased blood volume |
Assess the aging adult for a weakened ability to compensate for illness or injury. |
|
Hemoglobin levels decrease |
May be secondary to decreased intake of iron-rich foods |
Assess for evidence of gastrointestinal or other internal bleeding before concluding that anemia is a result of aging. Ensure adequate dietary intake of iron-rich foods. Encourage regular medical check-ups, including colon and bladder examinations. Assess prostate-specific antigen (PSA) in men. |
|
Leukocyte production decreases |
Less of a response to infection; may feel less pain |
Monitor closely for early signs of infection (e.g., increased fatigue, anorexia, or mental confusion) because the body may not show fever or elevated leukocyte count. |
Disorders of the blood and lymph can be quickly life-threatening.
EFFECTS OF AGING ON THE SYSTEM
In the older adult, hematopoiesis may decline because of loss of active bone marrow. Alterations in tissue oxygenation may therefore occur, especially during periods of stress, because of ineffective RBC production. The number of platelets in older adults may also slightly decrease, although fibrinogen levels and coagulation factors may increase. WBC production typically shows no real change. However, age-related changes in organs of the immune system can result in altered antigen-antibody responses and increased incidence of infection. Blood volume is reduced in older adults because of decreased muscle mass and metabolic rate. The range for albumin also drops. Table 23-3 presents the effects of aging on these systems.
NCLEX Alert Variations of growth and development across the lifespan are common NCLEX clinical concepts. Issues related to aging may involve prenatal, infant, young adult, mature adult, or older adult concerns.
KEY POINTS
• The functions of the hematologic system include transportation, regulation, and protection.
• Hematopoiesis, the formation of blood cells, originates in stem cells in red bone marrow.
• Blood is composed of plasma and formed elements, including RBCs, WBCs, and platelets.
• Plasma is 90% water. The remaining 10% is composed of proteins, salts, nutrients, wastes, gases, hormones, and enzymes.
• Erythrocytes, or RBCs, are the most numerous of the blood cells. Each RBC contains hemoglobin, which is responsible for carrying oxygen.
• WBCs fight infection. Each of the five types (basophil, eosinophil, neutrophil, lymphocyte, monocyte) has different mechanisms for this function.
• Platelets and numerous clotting factors must react in sequence before blood clotting can occur.
• Hemorrhage is usually thought of as the loss of a considerable amount of blood. Hemostasis refers to the stoppage of bleeding.
• The ABO and Rh blood groups are inherited combinations of antigens and antibodies.
• Lymph tissues filter blood, destroy pathogens, and develop antibodies against antigens.
• Lymphatic organs include the tonsils, spleen, and thymus.
• The pulmonary circulation allows blood to be oxygenated for distribution in the systemic circulation.
• The largest circulatory route is the systemic circulation, which transports oxygen, nutrients, and wastes to and from all body cells.
• Several arteries come together in the brain to form the circle of Willis. This arterial circle helps maintain and protect cerebral blood flow to the brain.
• The blood-brain barrier selectively determines what substances will enter the brain from the blood. Its purpose is to prevent harmful substances from entering the brain.
• The hepatic-portal circulation moves venous blood from abdominal organs (gastrointestinal [GI] system, pancreas, spleen) to the liver via the portal vein. The blood travels
through the liver, where it undergoes a variety of changes before entering the hepatic vein and then the inferior vena cava that will transport blood back to the heart.
• The lymph system drains interstitial fluid into lymphatic vessels, which empty into the veins.
