First, it is worth defining the difference between them. “Fluids are those substances that are permanently in the body and whose production does not depend on external stimuli”, says biologist Silvia Cristina Ribeiro de Souza, from the University of São Paulo (USP). This is the case with blood, the fluid that protects the brain and spinal cord, and the fluid that lubricates the joints. “Secretions, on the other hand, are produced according to demand”, says general practitioner Arnaldo Litchenstein, from Hospital das Clínicas in São Paulo. A good example is saliva, which is produced more intensely when we chew. Already the tear is secreted in greater quantity when we cry or when something irritates the eyes.
TEARDROP
Produced by the lacrimal glands, its main function is to keep the eyes moist, well lubricated, and protect them from bacteria and foreign bodies. An adult produces about 1 to 2 liters of tears per day
CEREBROSPINAL OR CEREBROSPINAL FLUID
It is the fluid, filtered from blood plasma, that bathes the structures of the central nervous system (the brain and spinal cord). It protects these noble and very sensitive tissues from variations in plasma and blood composition – due to external factors such as toxins, for example.
SPITTLE
Of the four secretions responsible for digestion, saliva is the first to go into action. Its acidity helps in the initial decomposition of food
MUCUS
Produced by cells in the respiratory tree (trachea and bronchi), it has the function of protecting and lubricating the entire respiratory system. The particles that come in with the air when we breathe stick to this mucus, which is then expelled through the throat and nose.
GASTRIC JUICE
It is the second digestive secretion. Once inside the stomach, the food receives a bath of gastric juice, which has the function of breaking food into small particles.
URINE
Result of the liquids filtered by the kidneys, it eliminates everything that was not useful for the organism and can be soluble in water. The minimum that an adult produces is 0.5 liters per day, but the normal is 2 to 3 liters
PANCREATIC JUICE
Thick and translucent, it performs the third stage of digestion and transforms food particles – already broken down in the stomach by gastric juice – into even smaller particles.
MILK
Their job, obviously, is to feed the babies. In its composition are all the necessary nutrients for the child, and many pediatricians do not even recommend water intake while the mother is producing milk.
BILE
Produced by the liver and stored in the gallbladder, its function is to cooperate with the pancreatic juice in the digestion of food.
SEMEN
It is the transport that sperm use to move around and survive the journey in search of the egg.
BLOOD
Produced by the bone marrow, it is the great means of transporting vital nutrients and everything that needs to be eliminated (as it carries impurities to the kidneys, which work as a filter). The liquid part of blood – its fluid itself – is called plasma. An adult has about 5 to 6 liters of blood in the body
VAGINAL SECRETION
Protects the vaginal mucosa and lubricates it, ensuring its moisture and the sensitivity of its walls, in addition to facilitating penetration
SYNOVIAL FLUID
It is the fluid that serves as oil to lubricate our joints. It is produced by cartilage cells that are found between the bones.
LYMPH OR LYMPHATIC FLUID
Blood circulates through the vascular system. When it accumulates in the extremities of the body, part of its plasma (the liquid part) ends up escaping through the walls of the vascular system and accumulates in the surrounding tissues. The lymphatic system drains the plasma and replaces it in the blood. Lymph, in addition to carrying plasma back, also carries immune system cells.
SWEAT
Its main function is to control body temperature. If it’s too hot, sweat cools the skin. In addition, it can eliminate some substances – alcohol, for example.