Question

A current working hypothesis is that diseases characterized by incurable weakness and lethargy may sometimes arise in part from loss of blood capillaries. Basing your answer on the laws of diffusion, explain how transport to and from a tissue would be affected if \(20 \%\) of its capillaries were lost.

Short answer

The loss of 20% of the capillaries would reduce the surface area for diffusion, thereby slowing down the transport of materials to and from tissues. This reduction could lead to insufficient provision of nutrients and oxygen to the tissues, resulting in weakness and possibly leading to certain diseases.

Step-by-step solution

Understanding capillaries and their role

Capillaries are the smallest blood vessels in the body and they serve the purpose of exchanging materials (like oxygen, nutrients, and waste products) between blood and tissues. This exchange happens via diffusion. Diffusion is a process that involves movement of particles from an area of higher concentration to an area of lower concentration.

The impact of losing 20% capillaries

If 20% of the capillaries were lost, there would be fewer pathways for the exchange of materials. This reduction in the surfaces for diffusion would slow down the movement of substances from blood to tissues and vice versa. As a result, despite having a need for nutrients and oxygen, tissues may not receive them in adequate quantity.

Application of the laws of diffusion

According to the laws of diffusion, the rate of diffusion is directly proportional to the surface area. With the loss of 20% of capillaries, the surface area for diffusion reduces considerably. Consequently, this will bring down the diffusion rate, resulting in slow transport of materials to and from tissues.

Connection with diseases characterized by weakness

This slower movement of nutrients and oxygen would not adequately meet a tissue's energy needs, leading to weakness. If this condition persists, it may cause certain diseases characterized by incurable weakness and lethargy.

Key concepts

Capillary Function

Capillaries play a crucial role as the body's smallest blood vessels, essentially serving as the interface between the bloodstream and tissues. Their primary function is to facilitate the exchange of vital substances, such as oxygen and nutrients, as well as the removal of metabolic waste products.

Due to their thin walls, which are only one cell thick, capillaries are particularly well-suited for the process of diffusion. This thin barrier allows for a short diffusion path, making the transfer of substances efficient. If a significant portion of capillaries was lost, as in the case of a 20% reduction, the body's ability to perform these exchanges would be impaired, leading to potential tissue starvation and the accumulation of waste products.

Laws of Diffusion

The laws of diffusion are fundamental principles that dictate how particles move in a solution. Fick's laws, which are often used to describe diffusion, state that the diffusion rate is directly proportional to the surface area available and the concentration gradient, and inversely proportional to the distance over which diffusion must occur.

In the context of capillaries, these laws imply that any reduction in the number of capillaries diminishes the overall surface area for diffusion, thereby slowing down the rate at which substances are exchanged. This slower exchange rate can have detrimental effects on the health and function of the tissues.

Tissue Oxygenation

Oxygenation of tissues is a vital process that ensures cells have the oxygen necessary to produce energy for all physiological functions. Capillaries are central to tissue oxygenation, delivering oxygen-rich blood directly to tissues.

When diffusion is compromised by the loss of capillaries, tissues suffer from reduced oxygen supply. Persistently low oxygen levels within tissues can lead to hypoxia, a state where insufficient oxygen reaches the cells, which may result in symptoms such as fatigue, weakness, and in severe cases, organ dysfunction.

Nutrient Transport

Just as with the oxygenation of tissues, nutrient transport through capillaries is essential for maintaining the health and function of cells. Nutrients such as glucose, amino acids, and fatty acids are transported from the bloodstream through capillary walls into the tissues to fuel cellular activities.

A decrease in the number of capillaries translates to a decreased capacity for nutrient transport, potentially leading to nutrient deprivation in tissues. This scarcity can impair cell function and growth, exacerbating conditions associated with weakness and lethargy, as there is not enough fuel for cells to function optimally.