Role of blood in maintaining homeostasis within the internal environment

What type of tissue is blood

• A fluid connective tissue

What are the three major components of blood

• Plasma

• Buffy coat

• Haematocrit (RBCs)

What is plasma and what percentage of blood does it make up

• Plasma is the liquid portion of blood; it makes up 55% of total blood volume

What is plasma composed of

• Mostly water

• Dissolved solutes

• Plasma proteins

What is the buffy coat

• What percentage of blood is the buffy coat

What percentage of blood is the buffy coat

• Less than 1% of total blood volume

What is haematocrit

• The percentage of total blood volume made up of red blood cells (RBCs)

What is the normal haematocrit range for males and females

• Males: 47 ± 5%

• Females: 42 ± 5%
  (Average ≈ 45%)

How does RBC structure enable efficient gas transport

• Biconcave shape

• Lack of organelles

• Flexibility maximises surface area

• Haemoglobin content

• Movement through vessels

Why is the biconcave shape of RBCs important

• Large surface area relative to volume for rapid gas exchange

• Allows RBCs to stack (rouleaux formation)

• Helps them move smoothly through capillaries

Why do RBCs lack organelles

• To create more space for haemoglobin, the protein that binds oxygen and some carbon dioxide

Why must RBCs be flexible

• To bend and squeeze through narrow capillaries without rupturing

What is the key protein inside RBCs

• Haemoglobin — binds O₂ and some CO₂ for transport

What are the three major functions of blood

• Distribution

• Regulation

• Protection

What does blood distribute

• Oxygen

• Nutrients (e.g., glucose)

• Hormones

• Waste products (e.g., CO₂)

What internal conditions does blood help regulate

• Interstitial fluid composition (e.g., electrolytes)

• pH

• Body temperature

• Water balance and pressure

How does blood provide protection

• Infection control (immune cells, antibodies)

• Prevention of blood loss (clotting)

How do the functions of blood relate to homeostasis

• The functions of blood maintain the internal environment within normal limits, allowing homeostasis to be maintained

Why is blood essential for maintaining stable internal conditions

• Blood transports substances, regulates internal variables, and protects the body—keeping the ECF within its normal range so cells can function

How does the distribution function of blood support homeostasis

• By delivering O₂, nutrients, and hormones, and removing wastes (e.g., CO₂), blood keeps internal conditions stable for cell survival

How does blood help regulate the internal environment

• Blood regulates pH, temperature, water balance, and electrolyte composition of interstitial fluid—key variables for homeostasis

How does the protective function of blood support homeostasis

• Blood prevents infection and blood loss, helping maintain stable internal conditions necessary for normal function

What are the levels of structural organisation in the body

• Cells → Tissues → Organs → Organ systems

What does the internal environment do for cells

• It enables the survival and normal function of cells

What do organ systems do for the internal environment

• They maintain the internal environment by regulating variables within their normal range

How are cells, tissues, organs, and organ systems linked to homeostasis

• Cells form tissues

• Tissues form organs

• Organs form organ systems

• Organ systems maintain the internal environment

• The internal environment keeps cells alive and functioning

This creates a continuous loop that supports homeostasis.

Why is the relationship between organ systems and the internal environment essential

• Because stable internal conditions allow cells to function, and functioning cells allow organ systems to operate — maintaining life