Unit 8 Lymphatic system

Question 1

What is lymph?

Answer 1

• Lymph is the interstitial fluid that is filtered but not reabsorbed at the venous end of the capillary during capillary exchange.
• It is a clear, pale-yellow fluid.
• Amounts to about 3 Litres/day.
• Transported by the lymphatic vessels.

Question 2

Structure and function of lymph capillaries

Answer 2

• Located in the spaces between tissue cells, into which interstitial fluid flows.
• Lymph capillaries are blind-ended structures.
• Are slightly larger in diameter than blood capillaries.
• Adjacent endothelial cells overlap forming flap-like mini valves
• Valves allow lymph to flow INTO them but NOT OUT of them.

Question 3

describe lymphatic vessels

Answer 3

• Lymph flows from lymphatic capillaries progressively larger lymphatic vessels
• Collecting lymphatic vessels resemble veins (circulatory) but have thinner walls and more valves.
• in the skin these vessels follow superficial veins
• in the viscera the vessels follow arteries and form networks around them.

Question 4

what is capillary exchange?

Answer 4

• Process by which most cells obtain their oxygen and nutrients and dispose of their wastes.
• It involves filtration and reabsorption

Question 5

describe capillary filtration

Answer 5

Takes place at the arterial end of the capillary where a portion of the plasma is filtrated through the capillary wall producing Interstitial fluid.

Question 6

describe capillary reabsorption

Answer 6

Takes place at the venous end of the capillary where a large proportion of the filtrate is reabsorbed back into the plasma

Question 7

describe BHP (Blood Hydrostatic Pressure)

Answer 7

• The pressure in the blood generated by ventricular systole.
• This pressure is much lesser in capillaries than when the blood left the heart.
• This force is pushing fluid OUT of the blood.

Question 8

describe IFHP (Interstitial Fluid Hydrostatic Pressure)

Answer 8

• The pressure in the fluid that has already been filtered

* This force is pushing fluid INTO the blood.

Question 9

describe BOP (Blood Osmotic Pressure)

Answer 9

• The osmotic pressure in the blood due to the presence of cells and large solutes.
• This force is pulling fluid INTO the blood.

Question 10

describe IFOP (Interstitial Fluid Osmotic Pressure)

Answer 10

• The osmotic pressure in the interstitial fluid due to the presence of solutes.
• This force is pushing fluid OUT of the blood.

Question 11

what is Net filtration pressure (NFP)

Answer 11

• Is the total of the forces pushing fluid outwards minus the total of the forces pulling fluid inwards.

Question 12

What is the flow of lymph through the body

Answer 12

Lymph passes from lymph capillaries > collecting lymphatic vessels > several lymph nodes > Lymph Trunks > Lymph ducts

Question 13

what are the 5 lymph trunks

Answer 13

1. Lumbar
2. Intestinal
3. Broncho mediastinal
4. Subclavian (R&L, collect lymph from shoulder region)
5. Jugular trunks (R &L , collect from

Question 14

what are the 2 lymph ducts

Answer 14

1. Right lymphatic duct: Lymph from right upper limb, right side of the head and thorax
2. Thoracic duct (=left lymphatic duct): Lymph from the rest of the body – Both the lower limbs, abdomen, left upper limb, left side of the head and thorax

Question 15

what are the 4 main driving forces behind lymph flow through the body

Answer 15

1. Skeletal Muscle pump
2. Respiratory pump
3. Smooth muscle contraction in the lymphatic vessel wall
4. Lymphatic vessels share sheaths with arteries and veins

Question 16

how does the Skeletal Muscle pump aid in lymph flow?

Answer 16

• When skeletal muscle contracts it squeezes blood and lymphatic vessels running through it.
• Lymph & blood are forced towards subclavian veins & heart.
• Valves ensure that flow continues in correct direction.

Question 17

how does the respiratory pump aid in lymph flow?

Answer 17

• During inspiration, pressure in the thoracic cavity decreases whilst pressure in the abdominal cavity increases.
• Hence flow is from high pressure (abdomen) to low pressure (thorax) and towards the heart.

Question 18

how does the smooth Muscle pump aid in lymph flow?

Answer 18

• When a lymphatic vessel expands because of lymph flowing into it, smooth muscle in the vessel wall contracts and helps propel lymph towards the heart.

Question 19

structure and function of lymph nodes

Answer 19

Structure:
• Bean shaped structures
• Covered with a capsule

Function:
• Purification of Lymph: Macrophages remove and destroy microbes and other debris
• Immune system activation

Question 20

process of lymph flowing through lymph node

Answer 20

• Lymph enters via the afferent vessels and leaves via the efferent vessel.
• Efferent vessels are lesser in number than the afferent vessels.
• Lymph flows slowly through the node, allowing time for phagocytosis of foreign substances and prevent them from entering the blood stream.

Question 21

where are the main clusters of lymph nodes located?

Answer 21

• Cervical nodes - Neck
• Axillary nodes - Armpits
• Inguinal nodes - Groin

Question 22

how does the composition of lymph change as it passes through the lymph nodes?

Answer 22

• As lymph flows through the body its composition changes slightly.
• As it passes through lymph nodes, it acquires lymphocytes.
• It may also acquire microorganisms and/or cancer cells.
• Fats and fat-soluble vitamins may be added to lymph from the small intestines.

Question 23

What are the 4 main functions of the lymphatic system?

Answer 23

• Maintaining water/fluid balance
• Maintaining protein balance
• Defending the body against infection and disease
• Transport of dietary fat