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Lymphatic Pump Mechanism
What role do valves play in lymphatic vessels?
A) They prevent fluid from entering the vessels
B) They allow fluid to flow in both directions
C) They ensure unidirectional flow of lymph
D) They increase the pressure within the vessels
E) They are not present in lymphatic vessels
C) They ensure unidirectional flow of lymph
Explanation: Valves in lymphatic vessels are crucial for maintaining unidirectional flow of lymph, preventing backflow and ensuring efficient transport towards the bloodstream.
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Lymphatic Pump Mechanism
What occurs when interstitial fluid hydrostatic pressure exceeds atmospheric pressure?
A) Lymph flow continues to increase indefinitely
B) Lymph flow reaches a maximum rate
C) Lymph flow stops completely
D) Lymph flow decreases
E) Lymph flow becomes erratic
B) Lymph flow reaches a maximum rate
Explanation: When interstitial fluid hydrostatic pressure becomes greater than atmospheric pressure, lymph flow does not increase further due to the balance of increased entry of fluid and compression of lymphatics, resulting in a maximum flow rate.
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Factors Influencing Lymph Flow
What are the primary factors that determine lymph flow?
A) Blood pressure and heart rate
B) Interstitial fluid pressure and activity of the lymphatic pump
C) Oxygen levels and carbon dioxide levels
D) Temperature and humidity
E) Nutrient concentration and waste accumulation
B) Interstitial fluid pressure and activity of the lymphatic pump
Explanation: The rate of lymph flow is primarily determined by interstitial fluid pressure and the activity of the lymphatic pump, indicating their crucial roles in lymphatic dynamics.
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Edema and Interstitial Fluid Pressure
What condition occurs when tissues lose their negative interstitial fluid pressure?
A) Hypertension
B) Edema
C) Dehydration
D) Hemorrhage
E) Shock
B) Edema
Explanation: When tissues lose their negative interstitial fluid pressure, fluid accumulates in the spaces, leading to a condition known as edema, which is characterized by swelling.
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Factors Influencing Lymph Flow
What happens to lymph flow as interstitial fluid pressure rises to 0 mm Hg?
A) It decreases significantly
B) It remains constant
C) It increases more than 20-fold
D) It becomes negative
E) It stops completely
C) It increases more than 20-fold
Explanation: As the interstitial fluid pressure rises to 0 mm Hg (atmospheric pressure), lymph flow increases dramatically, more than 20-fold, indicating a strong relationship between interstitial fluid pressure and lymph flow.
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External Factors Affecting Lymph Flow
What external factor can significantly increase lymph flow during exercise?
A) Increased body temperature
B) Contraction of surrounding skeletal muscles
C) Decreased heart rate
D) Increased blood pressure
E) Relaxation of tissues
B) Contraction of surrounding skeletal muscles
Explanation: The contraction of surrounding skeletal muscles during exercise compresses lymph vessels, significantly increasing lymph flow, often by 10- to 30-fold.
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Factors Influencing Lymph Flow
Which of the following factors does NOT increase lymph flow?
A) Elevated capillary hydrostatic pressure
B) Decreased plasma colloid osmotic pressure
C) Increased interstitial fluid colloid osmotic pressure
D) Increased permeability of the capillaries
E) Decreased interstitial fluid volume
E) Decreased interstitial fluid volume
Explanation: Decreased interstitial fluid volume would not favor lymph flow; rather, increased volume and pressure in the interstitium promote lymph flow.
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Protein and Fluid Regulation
What happens to proteins that leak from blood capillaries into the interstitium?
A) They are immediately absorbed by surrounding tissues
B) They accumulate in the interstitial fluid
C) They are converted into glucose
D) They are excreted through urine
E) They are transported back to the blood capillaries
B) They accumulate in the interstitial fluid
Explanation: Proteins that leak from blood capillaries tend to accumulate in the interstitial fluid, which increases the colloid osmotic pressure and affects fluid dynamics in the interstitium.
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Role of Interstitial Fluid Pressure
What effect does increasing colloid osmotic pressure have on fluid movement?
A) It decreases fluid filtration into the interstitium
B) It causes fluid to be reabsorbed into the blood
C) It shifts the balance of forces favoring fluid filtration into the interstitium
D) It has no effect on fluid movement
E) It causes fluid to evaporate
C) It shifts the balance of forces favoring fluid filtration into the interstitium
Explanation: Increasing colloid osmotic pressure in the interstitial fluid promotes fluid filtration from the blood capillaries into the interstitium, thereby affecting interstitial fluid volume and pressure.
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Physiological Role of Lymphatic System
How does the lymphatic system help control interstitial fluid?
A) By increasing blood pressure
B) By returning excess proteins and fluid to circulation
C) By filtering out toxins from the blood
D) By producing more red blood cells
E) By absorbing nutrients from the intestines
B) By returning excess proteins and fluid to circulation
Explanation: The lymphatic system functions as an overflow mechanism, returning excess proteins and fluid volume from tissue spaces back to the circulation, thus regulating interstitial fluid concentration, volume, and pressure.
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Lymphatic Capillary Function
How do anchoring filaments in lymphatic capillaries assist in lymph flow?
A) They prevent fluid from entering the capillaries
B) They pull on the capillary walls when tissue swells
C) They close the capillary openings
D) They increase the pressure inside the capillaries
E) They are not involved in lymph flow
B) They pull on the capillary walls when tissue swells
Explanation: Anchoring filaments adhere to surrounding tissue and pull on the walls of lymphatic capillaries when excess fluid enters the tissue, facilitating the flow of lymph into the capillaries.
