Chapter 6: The lymphatic system

Question 1

The body cells are bathed in?

Answer 1

interstitial (tissue) fluid, which leaks constantly out of the bloodstream through the permeable walls of blood capillaries.

Question 2

Lymph passes through what?

Answer 2

vessels of increasing size and a varying number of lymph nodes before returning to the blood. The lymphatic system consists of:

• lymph
• lymph vessels
• lymph nodes
• lymph organs, e.g., spleen and thymus
• diffuse lymphoid tissue, e.g., tonsils
• bone marrow.

Question 3

Functions of the lymphatic system

Answer 3

Your lymphatic system, part of your immune system, has many functions. They include protecting your body from illness-causing invaders, maintaining body fluid levels, absorbing digestive tract fats, and removing cellular waste.

Question 4

Adsorption in the small intestine

Answer 4

Fat and fat-soluble materials, e.g., the fat-soluble vitamins, are absorbed into the central lacteals (lymphatic vessels) of the villi.

Question 5

Immunity

Answer 5

The lymphatic organs are concerned with the production and maturation of lymphocytes, the white blood cells responsible for immunity. Bone marrow is therefore considered to be lymphatic tissue since lymphocytes are produced

Question 6

Lymph

Answer 6

Lymph is a clear watery fluid, similar in composition to plasma, with the important exception of plasma proteins, and identical in composition to interstitial fluid.
Lymph transports the plasma proteins that seep out of the capillary beds back to the bloodstream. It also carries away larger particles, e.g., bacteria and cell debris from damaged tissues, which can then be filtered out and destroyed by the lymph nodes.

Question 7

Lymph capillaries

Answer 7

Lymph capillaries are the finest, smallest branches of the lymphatic vessels. They run through nearly all body tissues.

Question 8

Larger lymph vessels

Answer 8

Lymph vessels are often found running alongside the arteries and veins serving the area. Their walls are about the same thickness as those of small veins and have the same layers of tissue
Like veins, lymph vessels have numerous cup-shaped valves to ensure that lymph flows in a one-way system towards the thorax.
There is no ‘pump’, like the heart, involved in the onward movement of lymph, but the muscle layer in the walls of the large lymph vessels has an intrinsic ability to contract rhythmically (the lymphatic pump).

Question 9

Thoracic duct

Answer 9

The largest lymphatic vessel within the human body and plays a key role in the lymphatic system.
T drains lymph from both legs, the pelvic and abdominal cavities, the left half of the thorax, head, and neck, and the left arm

Question 10

Right lymphatic duct

Answer 10

The right lymphatic duct is one of the vessels in the lymphatic system of the body.
The right lymphatic duct drains lymph from the right upper limb and right half of the thorax and head.

Question 11

lymph nodes

Answer 11

A small bean-shaped structure that is part of the body’s immune system. Lymph nodes filter substances that travel through the lymphatic fluid, and they contain lymphocytes (white blood cells) that help the body fight infection and disease.

Question 12

The structure of lymph nodes

Answer 12

Lymph nodes have an outer capsule of fibrous tissue that dips down into the node substance forming partitions, or trabeculae.
The main substance of the node consists of reticular and lymphatic tissue containing many lymphocytes and macrophages. Reticular cells produce the network of fibers that provide internal structure within the lymph node.
The lymphatic tissue contains immune and defense cells, including lymphocytes and macrophages

Question 13

Filtering and phagocytosis

Answer 13

Lymph is filtered by the reticular and lymphatic tissue as it passes through lymph nodes.
Organic material is destroyed in lymph nodes by macrophages and antibodies. Some inorganic inhaled particles cannot be destroyed by phagocytosis. These remain inside the macrophages, either causing no damage or killing the cell.
Material not filtered out and dealt with in one lymph node passes on to successive nodes and by the time lymph enters the blood it has usually been cleared of foreign matter and cell debris.

Question 14

Proliferation of Lymphocytes

Answer 14

Activated T- and B-lymphocytes multiply in lymph nodes. Antibodies produced by sensitized B-lymphocytes enter lymph and blood draining the node.

Question 15

Spleen

Answer 15

The spleen contains reticular and lymphatic tissue and is the largest lymph organ.

Question 16

Organs associated with the spleen

Answer 16

Superiorly and posteriorly – diaphragm
Inferiorly – left colic flexure of the large intestine
Anteriorly – fundus of the stomach
Medially – pancreas and the left kidney
Laterally – separated from the 9th, 10th, and 11th ribs and the intercostal muscles by the diaphragm.

Question 17

Phagocytosis

Answer 17

Phagocytosis, the process by which certain living cells called phagocytes ingest or engulf other cells or particles

Question 18

storage of blood

Answer 18

the spleen contains up to 350 mL of blood, and in response to sympathetic stimulation can rapidly return most of this volume to the circulation, e.g., in hemorrhage.

Question 19

immune response

Answer 19

The spleen contains T- and B-lymphocytes, which are activated by the presence of antigens, e.g., in infection. Lymphocyte proliferation during serious infection can cause enlargement of the spleen (splenomegaly).

Question 20

erythropoiesis

Answer 20

The spleen and liver are important sites of fetal blood cell production, and the spleen can also fulfill this function in adults in times of great need.

Question 21

thymus gland

Answer 21

The thymus gland is a secretory gland that has an important role in immune function.

Question 22

Thymus structure

Answer 22

The thymus is an organ that is critically important to the immune system which serves as the body’s defense mechanism providing surveillance and protection against diverse pathogens, tumors, antigens and mediators of tissue damage.

Question 23

Mucosa-associated lymphoid tissue

Answer 23

Mucosa-associated lymphoid tissue (MALT) is scattered along with mucosal linings in the human body and constitutes the most extensive component of human lymphoid tissue. These surfaces protect the body from an enormous quantity and variety of antigens.

Question 24

Tonsils

Answer 24

These are in the mouth and throat and will therefore destroy swallowed and inhaled antigens.

Question 25

Aggregated lymphatic follicles

Answer 25

Aggregated lymphatic follicles (Peyer’s patches).

These large collections of lymphoid tissue are found in the small intestine and intercept swallowed antigens.

Question 26

 Lymph vessel pathology (spread of disease)

Answer 26

The materials most spread via the lymph vessels from their original site to the circulating blood are fragments of tumors and infected material.

Question 27

 Malignant disease

Answer 27

Malignant tumors shed cells into the surrounding interstitial fluid, which drains into local lymphatic vessels and carries the tumor cells to the nearest set of lymph nodes. Here, if tumor cells arrive in sufficient numbers, they can establish secondary growths (metastases). From local lymph nodes, the tumor usually spreads to further lymph nodes and/or via the bloodstream to distant organs.

Question 28

Infection

Answer 28

Infectious material may enter lymph vessels from infected tissues. If phagocytosis is not effective the infection may spread from node to node, and eventually reach the bloodstream.

Question 29

Lymphangitis

Answer 29

Inflammation of lymph vessels

Question 30

Lymphadenitis

Answer 30

Infection of lymph nodes

Question 31

Lymphadenopathy

Answer 31

Enlargement of lymph nodes

Question 32

Splenomegaly

Answer 32

Enlargement of the spleen

Question 33

Lymphoedema

Answer 33

Swelling in tissues whose lymphatic drainage has been obstructed in some way

Question 34

tumors

Answer 34

may grow into, and block, a lymph vessel or node, obstructing the flow of lymph. A large tumor outside the lymphatic system may also cause sufficient pressure to stop the flow of lymph.