Lymphatic Vessels, Nodes, and Fluid Return - Anatomy and Physiology
- Lymph has no central pump. What mechanisms move it toward the heart?
- Skeletal muscle contraction, pressure changes during breathing, contraction of smooth muscle in lymphatic walls, and valves that prevent backflow.
- After surgical removal of axillary lymph nodes, the arm on that side swells. What is this called, and why does it occur?
- Lymphedema. Interstitial fluid accumulates because lymph drainage from the limb is impaired.
- Where does the thoracic duct empty lymph into the blood?
- At the junction of the left subclavian and left internal jugular veins.
- In which region of a lymph node are the B cell follicles with germinal centers located?
- The outer cortex. T cells are concentrated in the deeper cortex.
- What is the main role of lymphatic vessels in fluid balance?
- They return excess interstitial fluid and leaked plasma proteins to the venous blood.
- What saclike structure at the start of the thoracic duct collects lymph from the abdomen and lower limbs?
- The cisterna chyli.
- Which body regions are drained by the right lymphatic duct?
- The right upper limb and the right side of the head, neck and thorax. The thoracic duct drains everything else.
- What are lacteals, and what do they absorb?
- Lymphatic capillaries in intestinal villi that absorb dietary fat as chylomicrons; the resulting milky lymph is called chyle.
- What feature of lymphatic capillaries lets fluid enter easily but not leak back out?
- Overlapping endothelial cells form flaplike minivalves that open when interstitial pressure is higher than pressure inside the capillary.
- Why do more afferent than efferent lymphatic vessels serve a lymph node?
- Fewer exit vessels slow lymph flow through the node, giving macrophages and lymphocytes more time to act.
- What is lymph?
- Interstitial fluid once it has entered lymphatic vessels.
- What are the main functions of lymph nodes?
- They filter lymph: macrophages remove pathogens and debris, and lymphocytes are activated against antigens in the lymph.