The correct option is 1, 2 and 3 only.
Explanation
Lymph, also known as tissue fluid or interstitial fluid, is a mobile connective tissue that circulates within the lymphatic system. It acts as an intermediary between blood and tissue cells, facilitating the exchange of nutrients, gases, and hormones while playing a vital role in immune defense.
Statement-wise Analysis:
- Statement 1 is Correct: Lymph is formed when water and small water-soluble substances move out of blood capillaries into the intercellular spaces. It is chemically similar to blood plasma but is colourless (due to the absence of Red Blood Cells) and contains a significantly lower concentration of proteins compared to plasma.
- Statement 2 is Correct: The lymphatic system consists of an elaborate network of vessels that collect interstitial fluid. These vessels eventually drain the lymph back into the circulatory system through larger veins, specifically the subclavian veins.
- Statement 3 is Correct: Lymph plays a specific role in the digestive system. Fats are absorbed into specialized lymph capillaries called lacteals located in the intestinal villi.
- Statement 4 is Incorrect: The lymphatic system returns excess tissue fluid to the blood to maintain blood volume and prevent edema. It does not actively increase blood pressure in the arteries; arterial pressure is primarily generated by the heart's pumping action and vascular resistance.
Key Takeaway:
Lymph is a colourless fluid similar to plasma but with fewer proteins and no RBCs. Its primary functions are the maintenance of fluid balance, transport of absorbed fats (via lacteals), and immune protection.