10.6 The Lymphatic System

Question 1

What is the lymphatic system?

Answer 1

a system closely associated with the circulatory system and consists of lymphatic vessels and the lymphoid organs

Question 2

What are the 3 main functions of the lymphatic system that contributes to homeostasis?

Answer 2

1. lymphatic capillaries absorb excess tissue fluid and return it to the bloodstream
2. lymphatic capillaries absorb fats from the digestive tract and transport them to the bloodstream
3. lymphoid organs help to defend the body against disease

Question 3

What do lymphatic vessels do?

Answer 3

• form a one-way system that begins with lymphatic capillaries
• drain excess fluid from the tissues and return it to the circulatory system
• have valves to prevent backflow

Question 4

What are lymphatic capillaries?

Answer 4

tiny, closed-ended vessels whose walls consist of simple squamous epithelium, richly supplied in most regions of the body

Question 5

What do lymphatic capillaries do?

Answer 5

absorb excess tissue fluid

Question 6

What is tissue fluid?

Answer 6

mostly water, but contains solutes (ie. nutrients, electrolytes, oxygen) derived from the plasma and cellular products (ie. hormones, enzymes, wastes) secreted by cells

Question 7

What is lymph?

Answer 7

tissue fluid contained within lymphatic vessels

Question 8

What do lymphatic capillaries join to form?

Answer 8

form lymphatic vessels that merge before entering one of two ducts, the thoracic duct or the right lymphatic duct

Question 9

What does the larger, thoracic duct do?

Answer 9

returns lymph collected from the body below the thorax and the left arm and the left side of the head and neck, into the left subclavian vein

Question 10

What does the right lymphatic duct do?

Answer 10

returns lymph from the right arm and right side of the head and neck into the right subclavian vein

Question 11

What does lymph do on its way back to the circulatory system?

Answer 11

percolates through various lymph nodes, where any foreign material present can be recognized by the immune system

Question 12

What is the structure of the larger lymphatic vessels similar to?

Answer 12

circulatory veins

Question 13

What is the movement of lymph within lymphatic capillaries largely dependent on?

Answer 13

skeletal muscle contraction

Question 14

What happens to lymph forced through lymphatic vessels as a result of muscular compression?

Answer 14

prevented from flowing backward by one-way valves

Question 15

What is edema?

Answer 15

a localized swelling caused by the accumulation of tissue that has not been collected by the lymphatic system

Question 16

When does edema occur?

Answer 16

if too much tissue fluid is made and/or if not enough is drained away

Question 17

What can edema lead to?

Answer 17

• tissue damage

- death

Question 18

What are lymphoid organs?

Answer 18

organs that contain large numbers of lymphocytes

Question 19

What are lymphocytes?

Answer 19

the type of white blood cells that is mainly responsible for adaptive immunity

Question 20

What are primary lymphoid organs?

Answer 20

where lymphocytes develop and mature

ie. red bone marrow and thymus

Question 21

What are secondary lymphoid organs?

Answer 21

where some lymphocytes become activated

ie. lymph nodes and spleen

Question 22

What is red bone marrow?

Answer 22

contains a network of connective tissue fibres, along with stem cells that are ever capable of dividing and producing blood cells

Question 23

Describe the cells produced by the red bone marrow.

Answer 23

• some become the various types of white blood cells
• packed around thin-walled sinuses filled with venous blood
• differentiated blood cells enter the bloodstream at these sinuses

Question 24

Where is red bone marrow present in children?

Answer 24

most bones

Question 25

Where is red bone marrow present in adult?

Answer 25

mainly in the bones of the skull, sternum, ribs, clavicle, pelvis, and vertebral column

Question 26

What are B cells (B lymphocytes)?

Answer 26

lymphocytes that remain in the bone marrow until they mature

Question 27

What are T cells (T lymphocytes)?

Answer 27

lymphocytes that migrate from bone marrow through the bloodstream to the thymus where they mature and differentiate

Question 28

What is thymus?

Answer 28

soft, bilobed, primary lymphoid organ that secretes the hormone thymosins, which aids in the differentiation of T cells

Question 29

Where is the thymus located?

Answer 29

in the thoracic cavity between the trachea and the sternum above the heart

Question 30

When does the thymus grow the largest, and shrink?

Answer 30

grows around the time of puberty

shrinks as we get older

Question 31

What does connective tissue do for the thymus?

Answer 31

divides the thymus into lobules, which are filled with T cells and supporting cells

Question 32

What are the lobules of the thymus lined with?

Answer 32

epithelial cells that secrete hormones called thymosins

Question 33

What does thymosin do?

Answer 33

aid in the differentiation of T cells packed inside the lobules

Question 34

How many T cells exit the thymus?

Answer 34

about 5%

Question 35

What is apoptosis?

Answer 35

involves a cascade of specific cellular events leading to the death and destruction of the cell

Question 36

What undergoes apoptosis?

Answer 36

T cells that are capable of reacting to the body’s own cells

Question 37

What are T cells that leave the thymus capable of?

Answer 37

reacting to foreign molecules

Question 38

What happens in secondary lymphoid organs?

Answer 38

• may encounter foreign molecules or cells, after they proliferate and become activated
• these activated cells usually reenter the bloodstream, where they search for sites of infection and inflammation

Question 39

Where is the spleen?

Answer 39

upper left side of the abdominal cavity behind the stomach

Question 40

What does most of the spleen consist of?

Answer 40

• blood vessels and sinuses where macrophages remove old and defective blood cells
• small areas of lymphoid tissue, where lymphocytes can react to foreign invaders in the blood

Question 41

What happens to a person with no spleen?

Answer 41

• more susceptible to certain types of infections

- because the spleen also removes older red blood cells and platelets, the numbers of both types of cells may increase

Question 42

What are lymph nodes?

Answer 42

small, ovoid strictures occurring along lymphatic vessels, through which the lymph must pas

Question 43

What does connective tissue do for nodes?

Answer 43

divide the nodes into nodules

Question 44

What are nodules packed with?

Answer 44

B and T cells, contains sinus

Question 45

What happens as lymph courses through the many sinuses?

Answer 45

resident macrophages engulf pathogens

Question 46

What are pathogens?

Answer 46

disease-causing agents such as viruses and bacteria, as well as any debris present in the lymph

Question 47

What are lymph nodes named for?

Answer 47

their location

ie. inguinal nodes are in the groin, axillary nodes are in the armpits

Question 48

What do physicians feel for as evidence the body is fighting an infection?

Answer 48

swollen or tender lymph nodes

Question 49

What is metasis?

Answer 49

the spreading of cancer far from its place of origin

Question 50

Why does the lymphatic system sometimes inadvertently assist metasis?

Answer 50

cancer cells sometimes enter lymphatic vessels and move undetected to other regions of the body, where they may produce secondary tumours