Lymph (Tissue Fluid)
When blood flows through tiny capillaries in your tissues, some water and small water-soluble substances leak out into the spaces between your cells 🚰. This fluid is called interstitial fluid or tissue fluid. It has the same minerals as blood plasma but leaves behind large proteins and blood cells in the vessels.
Key Facts about Lymph:
- 💧 Acts as a “middleman” for exchanging nutrients, gases, and wastes between blood and cells.
- 🔄 Your lymphatic system (a network of special vessels) collects this fluid and returns it to major veins.
- 🩸 Once inside the lymphatic system, the fluid is called lymph.
- 🛡️ Lymph contains lymphocytes (white blood cells) that fight infections! 🦠
- 🍔 Carries nutrients and hormones. Fats from your food get absorbed into lymph via lacteals in your intestine.
Circulatory Pathways
Animals have two main types of circulation:
1. Open Circulatory System
- Found in arthropods (like insects) and molluscs (like snails).
- ❤️ Blood pumped by the heart flows into open body spaces (sinuses).
2. Closed Circulatory System
- Found in annelids (earthworms) and chordates (like humans!).
- ❤️ Blood stays inside a closed network of blood vessels.
- ✅ More efficient because flow can be precisely controlled.
Vertebrate Hearts Compared:
| Animal Group | Heart Chambers | Circulation Type | What Happens? |
|---|---|---|---|
| Fishes | 2 chambers (1 atrium + 1 ventricle) | Single circulation | Heart pumps deoxygenated blood → gills (oxygenates) → body → back to heart. |
| Amphibians & Reptiles* (*except crocodiles) | 3 chambers (2 atria + 1 ventricle) | Incomplete double circulation | Oxygenated blood (from lungs/skin) and deoxygenated blood (from body) mix in the single ventricle 😕. |
| Crocodiles, Birds & Mammals | 4 chambers (2 atria + 2 ventricles) | Double circulation | 🟦 Oxygenated and deoxygenated blood DO NOT mix 🟥! Separate pathways make this super efficient 🚀. |
NEET Power Concepts ⚡
- Lymph formation & function: How tissue fluid becomes lymph, and its role in immunity/fat absorption.
- Open vs. Closed circulation: Know examples (arthropods/molluscs vs. annelids/chordates) and why closed is better.
- Heart chambers evolution: 2-chambered (fish) → 3-chambered (frog) → 4-chambered (human).
- Blood mixing: Why 3-chambered hearts have mixed blood, but 4-chambered hearts don’t.
- Double circulation: ONLY in birds/mammals (and crocs!) – oxygenated and deoxygenated blood travel in separate loops.
Keep going! You’re doing great understanding how your body keeps everything flowing smoothly 💪❤️.
