Lymphatic System Flashcards

1
Q

What does the lymphatic system do?

A

Returns interstitial fluid that has leaked from the vascular system and plasma protein back to the blood.

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2
Q

What are the three parts of the lymphatic system?

A
  1. Lymphatics: Network of lymphatic vessels
  2. Lymph: The fluid in vessels
  3. Lymph nodes: Cleanse the lymph
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3
Q

Once interstitial fluid enters lymphatics, it is called?

A

Lymph

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4
Q

What do lymphoid organs and tissues provide?

A

Structural basis of immune system by housing phagocytic cells and lymphocytes
(e.g. spleen, thymus, tonsils, lymph nodes, other lymphoid tissues)

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5
Q

Why do lymphatic vessels offer a one-way system?

A

To ensure lymph flows only toward heart

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6
Q

What 2 things do lymphatics (lymph vessels) include?

A

Lymphatic capillaries
Larger lymphatic vessels

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7
Q

What are lymphatic capillaries?

A

Blind-ended vessels that weave between tissue cells and blood capillaries.

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8
Q

Lymphatic capillaries are absent from what?

A
  • Bones
  • Teeth
  • Bone marrow
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9
Q

How do lymphatic capillaries differ from blood capillaries?

A
  • Similar but more permeable
  • Can take up larger molecules and particles
    (e.g. proteins, cell debris, pathogens and cancer cells)
  • Can act as a route for pathogens to travel throughout the body
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10
Q

What 2 specialized structures allow increased permeability of lymphatic capillaries?

A
  1. Endothelial cells overlap loosely to form one-way minivalves
  2. Minivalves are anchored by collagen filaments to matrix, hence increases in ECF volume opens minivalves more
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11
Q

What happens to the minivalves when the extracellular fluid decreases?

A

Close

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12
Q

What are lacteals and their functions?

A
  • Specialized lymph capillaries present in the intestinal mucosa.
  • Absorb digested fat and deliver fatty lymph (chyle) to blood
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13
Q

What do larger lymphatic vessels consist of and what’s its structure like?

A
  • Collecting vessels, trunks and ducts.
  • Similar to veins, except have thinner walls with more internal valves and anastomose more frequently.
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14
Q

What are the main functions of lymphatic vessels?

A
  • Return excess tissue fluid to the blood
  • Return leaked proteins to the blood
  • Carry pathogens to lymph nodes
  • Carry absorbed fat from the intestine to the blood (via lacteals)
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15
Q

Where do lymph capillaries drain into?

A

Collecting lymphatic vessels

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16
Q

Collecting vessels in skin travel with ______ veins, but deep vessels travel with _______.

A
  • superficial
  • arteries
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17
Q

What are lymphatic trunks formed by?

A

Union of largest collecting vessels
to drain large areas of the body

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18
Q

Name regions where larger lymphatic trunks drain.

A
  • Paired lumber
  • Paired broncho-mediastinal
  • Paired subclavian
  • Paired jugular trunks
  • Single intestinal trunk
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19
Q

Lymph is delivered from trunks into what?

A

Two large lymphatic ducts

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20
Q

What does the right lymphatic ducts drain?

A

Right upper arm and right side of head and thorax

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21
Q

What does the thoracic duct drain?

A

The rest of the body; starts out as an enlarged sac aka cisterna chyli

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22
Q

What do lymphatic vessels do?

A
  • Return excess tissue fluid to the blood
  • Return leaked proteins to the blood
  • Carry pathogens to lymph nodes
  • Carry absorbed fat from the intestine to the blood (via lacteals)
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23
Q

What mechanisms are lymph propelled by?

A
  • Milking action of skeletal muscle
  • Pressure changes in the thorax during breathing
  • Valves to prevent backflow
  • Pulsations of nearby arteries
  • Contractions of smooth muscle in walls of lymphatics
24
Q

What do lymphoid cells consist of?

A
  1. Immune system cells found in lymphoid tissue
  2. Supporting cells that form lymphoid tissue structures
25
Q

What are the two main types of immune system cells?

A
  1. Lymphocytes: cells of the adaptive immune system; mature into a) T cells and b) B cells
26
Q

What do lymphocytes (T cells and B cells) do?

A

Protect against antigens
E.g. bacteria, toxins, viruses, mismatched RBCs, cancer cells

27
Q

What do T cells do?

A
  • Manage immune response
  • Attack and destroy infected cells
28
Q

What do B cells do?

A

Produce plasma cells that secrete antibodies

29
Q

Antibodies mark antigens for destruction by ______ or other means

A

phagocytosis

30
Q

What do macrophages do?

A

Phagocytize foreign substances and help activate T cells

31
Q

What do dendritic cells do?

A

Capture antigens and deliver them to lymph nodes.
Help activate T cells

32
Q

What is a supporting lymphoid cell and what does it do?

A

Reticular cells: Produce reticular fibers (stroma) in lymphoid organs

33
Q

What is a stroma?

A

Network like support that acts as scaffolding for immune cells

34
Q

What are the main functions of lymphoid tissue?

A
  • Houses and provides proliferation sites for lymphocytes
  • Offers surveillance vantage points for lymphocytes and macrophages as they filter through lymph
35
Q

What are lymphoid tissues composed of?

A

Reticular connective tissues.
- Macrophages live on reticular fibers
- Spaces b/w fibers offer a place for lymphocytes to occupy when they return from patrolling body

36
Q

What are the two main types of lymphoid tissues?

A
  1. Diffuse lymphoid tissues
  2. Lymphoid follicles (nodules)
37
Q

What are diffuse lymphoid tissues?

A

Loose arrangement of lymphoid cells and some reticular fibers
- Found in every body organ
- Larger collections in lamina propria of mucosae

38
Q

What are lymphoid follicles (nodules)?

A

Solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers
- Contain germinal centers of proliferating B cells
- Found in nodes, spleen, MALT
- Isolated aggregations of Peyer’s patches and in the appendix

39
Q

What is mucosa?

A

The combination of an epithelial tissue and a connective tissue, lamina propria

40
Q

What are primary lymphoid organs?

A

Areas where T and B cells mature.
- Red bone marrow: B cells
- Thymus: T cells

41
Q

What are secondary lymphoid organs?

A

Areas where mature lymphocytes first encounter their antigen and become activated
E.g. Nodes, spleen, MALT, and diffuse lymphoid tissues

42
Q

What are lymph nodes?

A

Principal secondary lymphoid organs of body
- Found throughout body
- Most embedded deep in connective tissue in clusters along lymphatic vessels
- Some near to body surface in inguinal, axillary, and cervical regions where collective vessels converge into trunks

43
Q

What are the two main functions of lymph nodes?

A
  1. Cleansing the lymph as filters
    - Macrophages remove and destroy microorganisms and debris
  2. Immune system activation
    - Offer a place for lymphocytes to become activated and mount an attack against antigens
44
Q

Structure of a lymph node

A
  • Surrounded by external fibrous capsule
  • Capsule fibers extend inward as trabeculae that divide node into compartments
  • Two distinct regions: cortex and medulla
45
Q

What does the medulla of lymph node contain?

A

B cells, T cells, and plasma cells are found.

46
Q

What does lymph sinusus found throughout the node consist of?

A
  • Large lymphatic capillaries spanned by crisscrossing reticular fibers.
  • Macrophages reside on fibers, checking for and phagocytizing any foreign matter
47
Q

How do lymph nodes circulate?

A
  1. Enters convex side of node via afferent lymphatic vessels
  2. Travels through medullary sinuses
  3. Exits concave side at helium via efferent lymphatic vessels
48
Q

What is a spleen and the two areas within?

A
  • Largest lymphoid organ
  • White and red pulps
49
Q

What are the two main functions of the spleen?

A
  1. White pulp: immune; site of lymphocyte proliferation and immune surveillance and response.
  2. Red pulp: cleaning; cleans old cells and platelets in the blood; macrophages remove debris in the red pulp. The cemetery of RBC
50
Q

What are the additional functions of the spleen?

A
  • Recycles the breakdown products of red blood cells for later reuse. Releases the breakdown of the iron salvaged from hemoglobin
  • Stores blood platelets and monocytes for release into the blood when needed
  • Site of erythrocyte production in the fetus
51
Q

What is MALT? What does it do and where is it found?

A
  • Lymphoid tissues in mucous membranes throughout body
  • Protects from pathogens trying to enter body
  • Found in the mucosa of the respiratory tract, genitourinary organs, and digestive tract. Large collection found in tonsils, Peyer’s patches and appendix
52
Q

What is the function and characteristics of tonsils?

A
  • To gather and remove pathogens in food or air
  • Contain follicles with germinal centers; scattered lymphocytes
  • Not fully encapsulated
  • Form tonsillar crypts; crypts trap and destroy bacteria
  • Allows immune cells to become activated and build memory cells against pathogens
53
Q

What are Peyer’s patches? What does it do.

A
  • Clusters of lymphoid follicles in wall of distal portion of small intestine (aka aggregated lymphoid nodules)
  • Destroy bacteria, preventing them from breaching intestinal wall.
  • Generate memory lymphocytes
54
Q

What does the appendix consist of?

A

A large number of lymphoid follicles
- Destroy bacteria, preventing from breaching intestinal wall
- Generate memory lymphocytes

55
Q

What does thymus do?

A

Functions as lymphoid organ where T cells mature
- Most active and largest in childhood
- Stops growing during adolescence, then atrophies
- Still produces immunocompetent cells, slowly
- Does not directly fight antigens
- Most thymic cells are lymphocytes
- No follicles due to lack of B cells
- Contains blood thymus barrier which prevents premature activation
- The stroma of the thymus consists of epithelial cells instead of reticular fibers to provide the right conditions for T cells to mature

56
Q

What are thymic corpuscles?

A
  • Sites of T cell destruction
  • Involved in the development of regulatory T cells, important for preventing autoimmune responses