10.6 The Lymphatic System Flashcards

1
Q

What is the lymphatic system?

A

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

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2
Q

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

A
  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
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3
Q

What do lymphatic vessels do?

A
  • 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
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4
Q

What are lymphatic capillaries?

A

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

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5
Q

What do lymphatic capillaries do?

A

absorb excess tissue fluid

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6
Q

What is tissue fluid?

A

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

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7
Q

What is lymph?

A

tissue fluid contained within lymphatic vessels

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8
Q

What do lymphatic capillaries join to form?

A

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

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9
Q

What does the larger, thoracic duct do?

A

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

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10
Q

What does the right lymphatic duct do?

A

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

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11
Q

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

A

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

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12
Q

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

A

circulatory veins

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13
Q

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

A

skeletal muscle contraction

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14
Q

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

A

prevented from flowing backward by one-way valves

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15
Q

What is edema?

A

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

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16
Q

When does edema occur?

A

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

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17
Q

What can edema lead to?

A
  • tissue damage

- death

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18
Q

What are lymphoid organs?

A

organs that contain large numbers of lymphocytes

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19
Q

What are lymphocytes?

A

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

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20
Q

What are primary lymphoid organs?

A

where lymphocytes develop and mature

ie. red bone marrow and thymus

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21
Q

What are secondary lymphoid organs?

A

where some lymphocytes become activated

ie. lymph nodes and spleen

22
Q

What is red bone marrow?

A

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

23
Q

Describe the cells produced by the red bone marrow.

A
  • 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
24
Q

Where is red bone marrow present in children?

A

most bones

25
Q

Where is red bone marrow present in adult?

A

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

26
Q

What are B cells (B lymphocytes)?

A

lymphocytes that remain in the bone marrow until they mature

27
Q

What are T cells (T lymphocytes)?

A

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

28
Q

What is thymus?

A

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

29
Q

Where is the thymus located?

A

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

30
Q

When does the thymus grow the largest, and shrink?

A

grows around the time of puberty

shrinks as we get older

31
Q

What does connective tissue do for the thymus?

A

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

32
Q

What are the lobules of the thymus lined with?

A

epithelial cells that secrete hormones called thymosins

33
Q

What does thymosin do?

A

aid in the differentiation of T cells packed inside the lobules

34
Q

How many T cells exit the thymus?

A

about 5%

35
Q

What is apoptosis?

A

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

36
Q

What undergoes apoptosis?

A

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

37
Q

What are T cells that leave the thymus capable of?

A

reacting to foreign molecules

38
Q

What happens in secondary lymphoid organs?

A
  • 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
39
Q

Where is the spleen?

A

upper left side of the abdominal cavity behind the stomach

40
Q

What does most of the spleen consist of?

A
  • 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
41
Q

What happens to a person with no spleen?

A
  • 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

42
Q

What are lymph nodes?

A

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

43
Q

What does connective tissue do for nodes?

A

divide the nodes into nodules

44
Q

What are nodules packed with?

A

B and T cells, contains sinus

45
Q

What happens as lymph courses through the many sinuses?

A

resident macrophages engulf pathogens

46
Q

What are pathogens?

A

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

47
Q

What are lymph nodes named for?

A

their location

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

48
Q

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

A

swollen or tender lymph nodes

49
Q

What is metasis?

A

the spreading of cancer far from its place of origin

50
Q

Why does the lymphatic system sometimes inadvertently assist metasis?

A

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