Body Fluids and Circulation - Advanced

The largest reservoir of body water is the intracellular fluid (ICF), which is the fluid inside cells. It accounts for approximately 60% of total body water.

Extracellular and intracellular fluids are referred to as 'fluid compartments' because they are separated by cell membranes and maintain different internal compositions.

Fluid movement in the capillary bed is determined by a combination of osmotic and hydrostatic pressures. Osmotic pressure pulls fluid into the capillaries, while hydrostatic pressure pushes fluid out.

Osmotic pressure is the force driving water movement across a semipermeable membrane to equalize solute concentration.

Water that filters from capillaries into the interstitial fluid is reabsorbed directly back into the bloodstream or via the lymphatic system.

The extracellular fluid (ECF) and intracellular fluid (ICF) are in osmotic equilibrium, meaning they have the same osmotic pressure. This ensures no net movement of water occurs between the two compartments.

Only total body water (TBW) can be directly measured.

The hypothalamus plays a crucial role in regulating water balance through two mechanisms: control of drinking behavior and control of ADH release.

Dehydration and water intoxication primarily affect the extracellular fluid concentration of sodium (Na+).

An effective buffer is an ion that can absorb excess H+ ions to prevent pH changes.

Calcium ions (Ca2+) play a pivotal role in haemostasis (blood clotting).

Haemostasis, the process of stopping bleeding, is initiated by a factor released from injured tissue.

Platelet activation leads to platelets becoming sticky and adhering to each other and injured tissue, forming a plug to stop bleeding.

In the intact circulatory system, blood doesn't clot because of endogenous inhibitory mechanisms that prevent clotting.

Clotting disorders lead to an excessive tendency to bleed, making it difficult to stop bleeding from even minor injuries.

Non-specific immune defenses, also known as innate immunity, include a variety of mechanisms that protect the body against a wide range of pathogens. These defenses are present from birth and do not require prior exposure to a specific pathogen.

Antibodies are specific proteins produced by the adaptive immune system to target specific pathogens.

Innate immunity is inherited and present from birth, providing the body with an initial line of defense against pathogens.

Immunity can be acquired through natural active exposure, natural passive exposure, and artificial means (immunization). It cannot be acquired through chemicals like antibiotics.

The first line of defense against invaders includes physical barriers like skin, tears, and saliva, as well as chemical defenses. Neutrophils are part of the second line of defense, which is the innate immune system.

Allergy involves an excessive immune response to usually harmless substances, known as allergens.

The nervous system regulates fluid balance in the body, receiving input from the hypothalamus and autonomic nervous system.

The lymphatic system plays a vital role in maintaining fluid balance by collecting excess fluid from the interstitial space and returning it to the bloodstream.

The kidneys are the primary organs responsible for regulating fluid and electrolyte balance in the body. They excrete excess water, electrolytes, and waste products in the urine.

Hormones like antidiuretic hormone (ADH) and aldosterone play crucial roles in regulating fluid balance in the body. ADH promotes water reabsorption in the kidneys, while aldosterone regulates sodium and potassium balance.