10.8 Health Issues Related to the Human Lymphatic System
The lymphatic system plays a vital role in maintaining fluid balance by returning excess tissue fluid to the blood circulatory system. When this system fails to function properly, excess fluid accumulates in the spaces between cells, resulting in a medical condition called oedema. Understanding the causes of oedema highlights the importance of the lymphatic system in human health.
Learning Objectives
- Define oedema and describe how it forms in body tissues.
- Identify the main causes of oedema, including pregnancy, plasma protein deficiency, prolonged immobility, and parasitic infections.
- Explain how the parasitic worm Brugia sp. causes lymphatic filariasis.
Causes and Manifestations of Oedema
Compare a normal limb with a swollen limb, and explore the four main causes of oedema.
Normal limb
Excess tissue fluid drains into lymphatic capillaries and returns to the blood circulatory system.
Swollen limb
Excess tissue fluid accumulates in the intercellular space, causing swelling known as oedema.
Short Explanation
Definition
Oedema — When excess tissue fluid is not returned to the blood circulatory system, it accumulates in the intercellular space. This accumulation causes swelling of the body tissues, a condition known as oedema.
How does oedema form?
Under normal conditions, excess fluid drains into the lymphatic capillaries to be returned to the bloodstream. However, if drainage is blocked or fluid dynamics are disrupted, fluid gathers in the tissues.
What can disrupt fluid dynamics?
Systemic factors include increased fluid production during pregnancy, decreased plasma proteins such as albumin, lack of physical movement in bedridden or paralysed patients, or physical blockage of lymphatic vessels by the parasitic worm Brugia sp.
Pregnancy
The maternal body produces more body fluid to fulfill the physiological needs of the growing foetus.
Deficiency in plasma protein
A deficiency of albumin in the blood reduces the osmotic pressure of blood, leading to fluid accumulation in tissues.
Prolonged bedridden patients
Paralysed or stroke patients who experience limited mobility can suffer from oedema in their legs due to reduced muscular contractions aiding fluid flow.
Parasitic infection
The parasitic roundworm Brugia sp. infects lymphatic vessels and prevents the normal flow of lymphatic fluid. The blocked lymphatic vessel leads to severe swelling in the infected body part, especially the legs. This medical condition is known as lymphatic filariasis. The parasite Brugia sp. is transmitted to humans through mosquito bites.
Try to Answer First
Answer in your mind, then press “Check Answer”.
What causes tissue fluid to accumulate in the intercellular space?
Which parasite causes lymphatic filariasis, and how is it transmitted?
Why do patients who are bedridden for long periods often develop swollen legs?
Common Mistakes
- Confusing oedema with fat accumulation or ordinary muscle growth rather than fluid accumulation in intercellular spaces.
- Forgetting that Brugia sp. is a parasitic worm, or misidentifying its transmission vector — it is transmitted by mosquito bites, not houseflies or contaminated food.
- Identifying oedema as a single independent disease rather than a condition or symptom resulting from various underlying causes.
Concept Misunderstandings
Oedema only occurs when someone is bitten by a mosquito.
Parasitic infection via mosquito bite is only one cause of oedema. Other non-infectious causes include pregnancy, deficiency of albumin in the blood, and prolonged immobility in bedridden patients.
The fluid that accumulates in oedema is blood.
The accumulating fluid is tissue fluid (interstitial fluid) in the intercellular spaces, not whole blood.
Summary
- Oedema is the swelling of tissues due to the accumulation of excess tissue fluid in the intercellular space when it is not returned to the blood circulatory system.
- Four main causes of oedema: pregnancy (increased fluid production for foetus), deficiency in plasma protein (low blood albumin), prolonged bedridden status (limited mobility in stroke/paralysed individuals), and parasitic infection (Brugia sp. blocking lymphatic vessels via mosquito bites, causing lymphatic filariasis).
Short Activity
Objective: identify the causes of oedema and the role of the lymphatic system.
A. Objective Quiz
Which parasitic organism infects lymphatic vessels and blocks the flow of lymphatic fluid, causing lymphatic filariasis?
A deficiency of which plasma protein in the blood can lead to oedema?
B. Fill in the Blanks
Tissue fluid that is not returned to the blood circulatory system accumulates in the intercellular space, leading to a swelling condition known as .
The parasite worm Brugia sp. is transmitted to humans through bites.
C. Matching / Drag and Drop
Match each cause of oedema with its corresponding mechanism or condition described in the textbook. On a phone, tap a choice first, then tap the matching box. Tap the Answer Choices area to return a selected item.
C. Match the Cause of Oedema to Its Description
Write the correct cause of oedema next to each description.
| Description / Mechanism | Cause of Oedema |
|---|---|
| 1. Body produces more fluid to fulfill the needs of a growing foetus. | |
| 2. Deficiency of albumin in the blood. | |
| 3. Limited mobility in paralysed or stroke patients causing leg swelling. | |
| 4. Brugia sp. blocks the lymphatic vessel causing lymphatic filariasis. |
Answer choices: Pregnancy • Deficiency in plasma protein • Prolonged bedridden condition • Parasitic infection
