8.3 - Blood, Tissue fluid, and Lymph Flashcards
What is the main transport medium of the human circulatory system, and what is its primary function?
Blood is the main transport medium. Its primary function is to carry oxygen, nutrients, hormones, and waste products throughout the body to maintain homeostasis and support cellular function.
What is tissue fluid, and how does it differ from blood?
Tissue fluid is a fluid that surrounds the cells in tissues, providing a medium for the exchange of substances between the blood and the cells. It is formed from blood plasma but lacks large proteins and blood cells, unlike blood.
What is the role of tissue fluid in the exchange of substances?
Tissue fluid allows for the exchange of gases (like oxygen and carbon dioxide), nutrients (like glucose and amino acids), and waste products (like urea) between the blood in capillaries and the cells. It is crucial for cellular metabolism and function.
What is lymph, and how does it fit into the circulatory system?
Lymph is a clear fluid that is part of the lymphatic system. It is formed when tissue fluid is collected into lymphatic vessels. Lymph helps to return excess tissue fluid back to the bloodstream and plays a key role in immune response by carrying white blood cells.
How is lymph formed from tissue fluid, and where does it go after being collected?
Lymph is formed when tissue fluid enters the lymphatic capillaries, which are small, thin-walled vessels. After being collected, lymph flows through larger lymphatic vessels and is eventually returned to the bloodstream at the subclavian veins.
What is the relationship between blood, tissue fluid, and lymph in the circulatory system?
Blood supplies oxygen, nutrients, and hormones to the tissues. The exchange of substances occurs in the capillaries, where blood pressure forces plasma and small solutes into the surrounding tissue, forming tissue fluid. This fluid exchanges materials with cells and is then collected as lymph, which is returned to the blood circulation to maintain fluid balance and immune function.
Why is the exchange between blood, tissue fluid, and lymph crucial for cellular function?
This exchange allows cells to receive necessary nutrients, oxygen, and signaling molecules while also eliminating metabolic waste products like carbon dioxide and urea. Maintaining proper fluid balance and immune surveillance also helps in preventing tissue damage and infection.
What factors influence the movement of substances between the blood, tissue fluid, and lymph?
The movement is influenced by factors such as blood pressure, osmotic pressure (due to plasma proteins), and the permeability of capillary walls. The lymphatic vessels help transport excess tissue fluid and immune cells to support immune function and fluid balance.
What are the components of blood, and how do they contribute to its function in the circulatory system?
Blood consists of plasma, red blood cells, white blood cells, and platelets. Plasma carries nutrients, waste, hormones, and proteins; red blood cells transport oxygen; white blood cells defend against infections; and platelets are involved in clotting to prevent excessive bleeding.
How does the lymphatic system support the immune system?
The lymphatic system transports lymph, which contains white blood cells (especially lymphocytes). It acts as a filter, removing pathogens and debris from the lymph before it is returned to the bloodstream, and plays a central role in immune surveillance and response.
What are the main functions of blood in the body?
The blood functions primarily in transport, immune defense, clotting, and homeostasis, including temperature regulation and pH buffering.
How does blood transport oxygen and carbon dioxide?
Red blood cells contain hemoglobin, which binds to oxygen in the lungs and carries it to respiring cells. Carbon dioxide is transported back to the lungs as bicarbonate ions, dissolved in plasma, or bound to hemoglobin.
How does blood transport digested food?
Blood carries absorbed nutrients, such as glucose and amino acids, from the small intestine to cells where they are used for energy and growth.
What nitrogenous waste product does blood transport, and where does it go?
Blood transports urea, a nitrogenous waste product from protein metabolism, from the liver to the kidneys for excretion.
What role does blood play in hormone transport?
Blood carries hormones, which are chemical messengers produced by endocrine glands, to target cells and organs to regulate body processes.
How does blood transport stored food molecules?
Blood carries glucose from glycogen stores in the liver and fatty acids from adipose tissue to cells that require energy.
How does blood contribute to wound healing?
Blood transports platelets to damaged areas, where they form clots to prevent excessive bleeding and initiate tissue repair.
How does blood help in the immune response?
Blood contains white blood cells and antibodies that help identify and destroy pathogens, protecting the body from infections.
How does blood help regulate body temperature?
Blood distributes heat throughout the body. When body temperature is high, blood vessels near the skin dilate (vasodilation) to release heat; when cold, they constrict (vasoconstriction) to retain heat.
What role does blood play in pH regulation?
Blood acts as a buffer, helping to maintain a stable pH by neutralizing excess acids and bases, ensuring that enzyme activity and cellular processes function properly.
What substances can pass through the fenestrations in capillary walls?
Dissolved substances in plasma, except for large plasma proteins, can pass through.
Why can’t large plasma proteins pass through capillary walls?
They are too large to fit through the fenestrations in the capillary endothelium.
What effect do plasma proteins, particularly albumin, have on blood in the capillaries?
Plasma proteins lower the water potential of the blood, creating an osmotic gradient that draws water into the capillaries via osmosis.
What is oncotic pressure, and what is its typical value?
Oncotic pressure is the tendency of water to move into the capillaries by osmosis due to plasma proteins. It is around -3.3 kPa.
What is hydrostatic pressure, and how is it generated?
Hydrostatic pressure is the pressure exerted by blood against capillary walls due to the surge of blood from the heart’s contraction.
What is the hydrostatic pressure at the arterial end of the capillary, and how does it compare to oncotic pressure?
The hydrostatic pressure is 4.6 kPa, which is higher than the oncotic pressure of -3.3 kPa, causing fluid to be forced out of the capillaries.
What is the fluid that leaves the capillaries and fills spaces between cells called?
Tissue fluid.
How does tissue fluid compare in composition to plasma?
Tissue fluid has the same composition as plasma, but without red blood cells and plasma proteins.
What happens to hydrostatic pressure as blood moves through capillaries toward the venous end?
Hydrostatic pressure drops to 2.3 kPa because fluid has moved out, and the pulse pressure is lost.
Why does water move back into the capillaries at the venous end?
The oncotic pressure remains at -3.3 kPa, which is now stronger than the hydrostatic pressure, so water moves back into the capillaries by osmosis.
By the time blood reaches the veins, what percentage of tissue fluid has returned to the blood vessels?
90% of the tissue fluid is reabsorbed into the blood.
What happens to the 10% of tissue fluid that does not return to the capillaries?
It drains into the lymphatic system via lymph capillaries and is called lymph.
What are lymph capillaries, and how do they function?
Lymph capillaries are blind-ended tubes that collect excess tissue fluid and transport it into the lymphatic system.
How does the composition of lymph compare to blood plasma and tissue fluid?
Lymph is similar to plasma and tissue fluid but contains:
1. Less oxygen and fewer nutrients
2. More fatty acids, absorbed from the villi of the small intestine
How does lymph move through the lymphatic system?
Lymph is transported by:
1. Contraction of body muscles, which squeeze the lymph vessels
2. One-way valves, which prevent backflow, similar to those in veins
Where does lymph eventually return to the bloodstream?
Lymph drains into the right and left subclavian veins, located under the clavicles (collarbones).
What are lymph nodes, and what is their function?
Lymph nodes are small structures along the lymphatic vessels that:
1. Allow lymphocytes to build up and produce antibodies
2. Filter out bacteria and debris, which are then ingested by phagocytes
How does the lymphatic system contribute to the immune response?
The lymphatic system:
1. Produces lymphocytes to fight infections
2. Filters out pathogens and debris in lymph nodes
3. Provides antibodies to be released into the bloodstream
Why do doctors check lymph nodes in the neck, armpits, stomach, or groin?
Swollen lymph nodes indicate an active immune response, meaning the body is fighting an infection.
Why does some tissue fluid enter the lymphatic system instead of returning to capillaries?
The hydrostatic pressure at the venous end of capillaries is too low to reabsorb all the tissue fluid, so excess fluid drains into lymph capillaries.
How do fatty acids enter the lymph?
Fatty acids from the small intestine are absorbed into the lacteals, which are lymph capillaries found in the villi of the small intestine.
Why do lymphatic vessels have one-way valves?
Since the lymphatic system has no pump, these valves prevent backflow, ensuring lymph moves toward the subclavian veins.
What would happen if the lymphatic system did not return excess tissue fluid to the blood?
It would cause fluid accumulation in tissues, leading to swelling (oedema).
What types of white blood cells are found in lymph nodes?
Lymphocytes, which include:
1. B cells (produce antibodies)
2. T cells (help fight infections)
How do lymph nodes filter out harmful substances?
Phagocytes inside the lymph nodes engulf and digest bacteria, viruses, and debris before the lymph returns to the bloodstream.
Why do swollen lymph nodes indicate an infection?
Lymphocytes multiply in response to an infection, causing swelling in lymph nodes as they produce antibodies.
What is the medical significance of the lymphatic system?
The lymphatic system plays a role in:
1. Infection detection (swollen lymph nodes)
2. Cancer metastasis (cancer cells can spread via lymph)
3. Fluid balance (preventing oedema)
