Unit 10: The Lymphatic System

Question 1

What are the functions of the lymphatic system?

Answer 1

• Transports and house lymphocytes and other immune cells
• Return excess fluid in body tissues to blood to maintain blood volume
• Helps Immune System defend body against infectious agents

Question 2

What are the components of the lymphatic system?

Answer 2

• Lymph vessels, lymphoid tissues and organs
• Lymph - the fluid transported within lymph vessels

Question 3

What are the characteristics of lymph?

Answer 3

• Some fluid leaves blood capillaries and is not reabsorbed by them
• This interstitial fluid moves into lymphatic capillaries where it is then called lymph

Question 4

What are the components of lymph?

Answer 4

• Water, dissolved solutes, and small amount of protein
• Sometimes cell debris, pathogens, or cancer cells

Question 5

What are lacteals?

Answer 5

Lymphatic capillaries in GI tract, absorb lipid-soluble substances from GI Tract

Question 6

Lymphatic capillaries are

Answer 6

small, close-ended vessels that absorb interstitial fluid. They are interspread around most blood capillaries (absent in avascular tissues, spleen, and CNS)
They are slightly larger than blood capillaries and have no basement membrane.

Question 7

Lymphatic capillary walls

Answer 7

are made of endothelial cells.
They have flaps between cells through which fluid enters but can’t exit.

Question 8

Anchoring filaments

Answer 8

hold endothelial cells to nearby structures

Question 9

How does lymph move into lymphatic capillaries?

Answer 9

Hydrostatic pressure of interstitial fluid pushes lymph into the capillary. The anchoring filaments link endothelial cells to surrounding structures to prevent the vessel from collapsing and the interstitial hydrostatic pressure opens the intercellular openings between cells to allow fluid into the capillary. The pressure of lymph insides the vessel forces the flaps of the capillary wall to close with the lymph inside.

Question 10

What is the flow of lymph through vessels of larger and larger size?

Answer 10

lymphatic capillaries
lymphatic vessels
lymphatic trunks
lymphatic ducts
lymph returned to blood circulation

Question 11

What are lymphatic vessels?

Answer 11

They are fed by lymphatic capillaries and are located adjacent to arteries and veins. They have intima, media, and externa tunics containing valves to prevent pooling and backflow of lymph. Some vessels connect to lymph nodes for filtration purposes.

Question 12

How is lymph moved?

Answer 12

Since the lymphatic system lacks a pump, lymph is moved using skeletal muscles and respiratory pumps, Pulsatile movement of blood in nearby arteries and rhythmic contraction of smooth muscle in larger lymph vessel walls.

Question 13

What are lymphatic trunks?

Answer 13

They are fed by lymphatic vessels.

Question 14

What are lymphatic ducts?

Answer 14

They are fed by lymphatic trunks and are the largest lymphatic vessel. They bring lymph to the venous blood circulation.

Question 15

What are the two types of lymphatic ducts?

Answer 15

Right lymphatic duct
Thoracic duct

Question 16

The right lymphatic duct drains….?

Answer 16

The upper right quadrant of the body (right side of head and neck, right upper limbs and right side of thorax). It is located near the right clavicle and it delivers lymph to the junction of the right subclavian and right internal jugular veins.

Question 17

The thoracic duct drains….?

Answer 17

lymph from the left side of the head and neck, left upper limb, left side of thorax, abdomen, and both lower limbs. It is the largest lymphatic vessel and runs from the diaphragm to junction of the left subclavian and left jugular veins. It has a saclike cisterna chyli at its base which receives lipid-rich chyle from the gastrointestinal (GI) tract.

Question 18

What is Lymphedema?

Answer 18

It is the accumulation of interstitial fluid due to an interference with lymphatic drainage. It causes swelling and pain in affected area, can interfere with wound healing and contribute to infection. This happens from blockage or removal of a lymph vessel (trauma or infection of lymph vessels or tumors and radiation therapy scarring or surgical removal of the lymph vessel). It can be controlled by compression garments, exercise and massages. Extreme cases of lymphedema are known as elephantiasis which is caused by the infection a parasitic worms.

Question 19

What are primary lymphoid structures?

Answer 19

involved in formation and maturation of lymphocytes

Question 20

What are the 2 primary lymphoid structures?

Answer 20

Red bone marrow
Thymus

Question 21

Red Bone Marrow is…?

Answer 21

It is located between trabeculae of spongy bone (flat bones of the skull, rib, sternum, vertebrae, ossa coxae, heads of humerus and femur). It is also the site of hematopoiesis which is the production of the blood’s formed elements (T- and B-lymphocytes). The T-lymphocytes migrate to the thymus to complete maturation).

Question 22

What is the role of the thymus?

Answer 22

The thymus is involved in T-lymphocyte maturation and is located in the mediastinum. It is larger in children than adults because it grows until puberty, regresses and then it is slowly replaced by adipose tissue.

Question 23

What are secondary lymphoid structures responsible for?

Answer 23

They do not form lymphocytes by house them as well as other immune cells within a reticular connective tissue matrix. They are sites of immune response initiation.

Question 24

What are the 5 secondary lymphoid structures?

Answer 24

Lymph nodes, spleen, tonsils, lymphatic nodules, and MALT (mucosa-associated lymphoid tissue)

Question 25

Lymphoid organs vs. lymphoid nodules

Answer 25

Secondary lymphoid structures are organized into lymphoid organs and aggregates of lymphoid nodules.

Question 26

What secondary lymphoid organs have a complete capsule of dense irregular connective tissue?

Answer 26

Spleen and lymph nodes

Question 27

What secondary lymphoid structures have an incomplete capsule or lack one?

Answer 27

Tonsils, MALT (mucosa-associated lymphatic tissue), and diffuse lymphoid nodules

Question 28

What are lymph nodes and what do they do?

Answer 28

Lymph nodes filter lymph and remove unwanted substances. They are small, oval, encapsulated structures located along deep and superficial pathways of lymph vessels. Occurs in clusters receives lymph from different body regions (e.g. cervical lymph nodes receive lymph from head and neck, axillary lymph nodes receive lymph from breast, axilla, and upper limb, and inguinal lymph nodes in groin receive lymph from lower limb and pelvis).

Question 29

What are the components of the lymph node?

Answer 29

Consists of afferent lymphatic vessels to bring lymph to nodes and an efferent vessel drains a lymph node which is located at the hilum (involuted portion of node). It is encapsulated in dense irregular connective tissue and the trabeculae of the capsule is subdivided into compartments. Also contains an outer cortex and inner medulla.

Question 30

Describe the flow through lymph nodes.

Answer 30

Lymph first enters through several afferent vessels which creates pressure to push the lymph through the node to the single exit vessel. The lymph is then monitored for the presence of foreign material (macrophages remove foreign debris and lymphocytes may initiate an immune response as this point). Lymphocytes proliferate especially in germinal centers than can cause enlarged nodes that can be palpated in the neck and axilla. The lymph then exits the node through the efferent vessel and may pass through neighboring lymph nodes or can continue to the lymphatic trunk.

Question 31

Describe filtration in lymph nodes.

Answer 31

Filtration requires a driving force to force the fluid through the filtration medium (e.g. the lymphatic tissue in the lymphatic node) which is applying pressure. Due to the fact that there are more afferent vessels then efferent, the pressure begins to build up. The pressure forces the lymph through the lymphatic nodules which solid materials (e.g. bacteria, viruses, dead cells) begin to be trapped. Macrophages remove the excess debris by digesting them with lysosomes.

Question 32

State the 4 functions of the spleen.

Answer 32

“Eat” foreign particles - filters and monitors blood (not lymph)
Clear defective erythrocytes and platelets
Store erythrocytes and platelets
Haematopoiesis in first 5 months of fetal life (makes blood cells, can revert back to this which certain blood disorders)

Question 33

What is the white pulp spleen?

Answer 33

It is clusters of T- and B-lymphocytes and macrophages around the central artery and monitors blood for foreign materials and bacteria.

Question 34

What is the red pulp spleen?

Answer 34

It contains erythrocytes, platelets, macrophages, and B-lymphocytes and is a storage site for erythrocytes and platelets. The macrophages in red pulp remove particles by phagocytizing bacteria, debris, and defective erythrocytes and platelets.

Question 35

What are the tonsils responsible for?

Answer 35

Immune surveillance of inhaled and ingested substances

Question 36

What are tonsillar crypts?

Answer 36

It is invaginations that trap material and they contain lymphoid nodules.

Question 37

What are lymphoid nodules?

Answer 37

They are clusters of lymphoid cells with some extracellular matrix (not completely surrounded by connective tissue capsule). Scattered nodules termed to diffuse lymphoid tissue and they are found is every body organ. They help defend against infection and in some areas they group together to form larger structures (e.g. MALT - mucosa-associated lymphatic tissue)

Question 38

What is MALT (mucosa-associated lymphatic tissue)?

Answer 38

It is located in the gastrointestinal, respiratory, genital, and urinary tracts and they help defend against foreign substances. It is very prominent in small intestines especially ileum.

Question 39

What are peyer patches?

Answer 39

They are large collections of lymphoid nodules within the wall of the gastrointestinal (GI) tract.

Question 40

Describe the role of the lymphatic system in assisting the cardiovascular system.

Answer 40

Lymphatic trunks and ducts receive lymph from lymphatic vessels. Lymphatic trunks drain into lymphatic ducts. Lymphatic ducts drain lymph into the venous circulation. Lymphatic vessels transport lymph and drain into lymph nodes (which filter the lymph). Lacteals are lymphatic capillaries in the small intestine that absorb lipid-soluble substances from the gastrointestinal (GI) tract.
Lymphatic capillaries absorb interstitial fluid that is renamed lymph when it enters the lymphatic capillaries. Red pulp spleen phagocytizes old or defective erythrocytes and platelets from circulating blood; serves as a blood reservoir and storage site for both erythrocytes and platelets.

Question 41

Describe the role of lymphatic system in immunity.