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Cell And Tissue Biology > Lymphatic System > Flashcards

Lymphatic System Flashcards

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1
Q

What is the lymphatic system?

A

A group of cells, tissues, and organs that monitor the body and react to a presence of potentially harmful substances and infectious agents

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2
Q

What are lymphocytes?

A

These are the definitive cell type and the effector cells in the immune system response

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3
Q

What is the immune system?

A

An interconnection of blood and lymphatic circulation through various organs, tissues, and cells

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4
Q

What are the primary lymphatic organs?

A

Bone marrow

Thymus

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5
Q

What are the secondary lymphatic organs?

A

Lymph nodes
Spleen
Diffuse lymphatic tissue nodules (such as MALT, tonsils, and appendix)

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6
Q

The lymphatic system is composed of ______ vessels that transport interstitial fluid (referred to as ____)

A

Lymphatic, lymph

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7
Q

What is innate immunity (natural, nonspecific) ?

A

This is the first line of defence against microbial invasion ]. You are born with this ability and it does not change over time

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8
Q

What are mediated cells within the lymphatic system?

A

Phagocytic, neutrophils, macrophages/monocytes, and also NK cells

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9
Q

What is adaptive immunity?

A

Adaptive defence that targets specific invaders and foreign proteins. Acquired by gradual exposure.

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10
Q

With regards to adaptive immunity, what type of lymphocytes are involved? What is their purpose?

A

Involves B and T lymphocytes, these activate and work against specific antigens.

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11
Q

Specific molecules are presented to lymphocytes by ______ ______ cells

A

Phagocytic APC (antigen presenting cell)

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12
Q

What are APC cells derived from?

A

Mostly derived from monocytes, macrophages, kupffer cells, dendritic cells, langerhans cells

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13
Q

What are the two types of specific defences of adaptive immunity?

A

Humoral immunity—> production of proteins called antibodies (immunoglobulins) by B lymphocytes which have differentiated into plasma cells

Cell mediated immunity—> response targets transformed cell and infected cell (viral, fungal) for destruction by specific killer cells. These involve T lymphocytes

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14
Q

What are antigenic determinants (Epitopes)?

A

These are small molecular domains of the antigen immune cells that can be recognized and reacted to

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15
Q

What are major histocompatability? What are the two types (don’t describe)? And where does this originate?

A

Major Histocompatability (MHC) is produced by a super gene located on chromosome 6 in humans. It has MHC I and MHC II

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16
Q

Explain what MHC I means

A
  • expressed on the surface of all nucelated cells and platelets
  • presents peptide fragments to cytotoxic CD8+ T lymphocytes
  • acts as a target to allow elimination of abnormal host cells
  • express they are actively synthesized by the cell
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17
Q

Explain what MHC II is

A
  • limited in distribution, expressed on surface of all APCs
  • critical in immune interactions
  • MHC II partially digest endocyted foreign peptides to CD4+ T lymphocytes
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18
Q

How are cells identified within the immune system?

A

They are identified by specific clusters of differentiation (CD) markers on their surface

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19
Q

What are cluster differentiation (CD) molecules?

A

These are designated by numbers according to an international system that relate them to antigens expressed on their surface at different stages in their differentiation

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20
Q

True or false:

MHC occur in strict species, variety within these species is genetic.

A

False, MHC proteins occur in many species

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21
Q

What is the humans version of MHC?

A

HLA—>Human leukocyte Antigen

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22
Q

Explain in detail some characteristics of T-Lymphocytes (T cells)

A
  • differentiate in the thymus (but are produced in bone marrow)
  • accounts for 75% of circulating lymphocytes
  • involved in cell mediated immunity
  • recognize antigenic epitopes via T cell receptors (TCRs)
  • only recognize antigens when presented as part of MHC molecules
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23
Q

What are some important subsets of T Lymphocytes? (Don’t explain)

A
  1. helper T lymphocytes express CD4 markers, CD4+T cells
  2. Cytotoxic T lymphocytes (Killer T cells)
  3. Regulatory (suppressor) Lymphocytes
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24
Q

Helper T lymphocytes express CD4 markers, CD4+T. Explain how this is important in subset T lymphocytes.

A
  • TCRs and CD4 bind MHC class II molecules
  • assist with the immune response by producing cytokines

Activates the following 3:

  • cytotoxic CD8+T cells (further activates CD4+T cells)
  • activates macrophages to become phagocytic and produces cytokines
  • Promotes differentiation of B cells into plasma cells
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25
Q

Cytotoxic T lymphocytes (Killer T cells) express CD8 marker and create CD8+ cells, How is this an important subset of T lymphocytes?

A 
TCRs with CD8 bind to specific antigens on cancer transformed cells
- MHC class 1 molecules are altered from the norm, these put on display microorganisms, parasites, and transported cells
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26
Q

What is the importance of regulatory (suppressor) lymphocytes for subsets of T lymphocytes?

A

These have CD4+ and CD25+

-serve to inhibit excessive immune responses by inhibiting other immune cells

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27
Q

What does the activation of T lymphocytes cause?

A

This produces clones of memory cells. This means there is a faster response on subsequent exposures

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28
Q

Explain in detail some characteristics of B lymphocytes (B-cells)

A
  • differentiate in bone marrow (bursa equivalent organs)
  • accounts for 20-30% of circulating lymphocytes
  • involved in humoral immunity
  • each cell is covered with many B-Cell receptors (BCRs) which are monomers of IgM and IgD
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29
Q

How do IgM and IgD function?

A

Bind antigen—>endocytosed—>processed—>presenting on the MHC class II molecule of the B cell—> presenting to a T helper cell—> T helper stimulates gene recombination— >maturation into plasma and memory B cells

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30
Q

What are the function of plasma cells?

A
  • produce anitbodies against the specific antigen that was originally bound and processed
31
Q

What is the function of memory B cells?

A

These are long lived, allow a rapid response upon subsequent exposure

32
Q

What does the activation of B lymphocytes cause?

A

This produces clones of memory B cells which means a faster response on subsequent exposure

33
Q

What is the basic structure of an antibody?

A

Two light chains and two heavy chains form an antibody monomer

34
Q

What are the two chains in an antibody connected by? What do their various ends connect?

A

The chains are linked by a disulfide bond.

The variable portions (Fab) bind the antigen (at a specific epitope)

The constant region (Fc) of the molecule binds to the surface receptor of the cell

35
Q

Wha are the five major classes of antibodies? (Don’t explain them)

A

G A M E D

  1. IgG
  2. IgA (secretory)
  3. IgM
  4. IgE
  5. IgD
36
Q

Describe the antibody IgG and its characteristics

A

This is the most abundant, and smallest monomer

  • highly soluble and confers passive immunity
  • activates phagocytosis, opsonization, neutralizes antigen
  • major memory immunoglobulin
  • found in fetal circulation in women
37
Q

Describe the antibody IgA and its characteristics

A

This is present in most secretions (milk, tears, saliva)

  • produced by plasma cells mainly near mucosal surfaces for protection against organisms
  • can be found in a diametric form (J, joining chains) that holds two monomers together
  • has a secretory piece
  • mainly protects mucosae
38
Q

Describe the antibody IgM and its characteristics

A

This is the largest immunoglobulin and exists in a pentameric form

  • mainly produced in the initial response to an antigen response
  • most effective antibody in activating compliment
  • serves as an antigen receptor (BCR) as monomers
  • found in B lymphocyte surfaces
39
Q

Describe the antibody IgE and its characteristics

A
  • these have Fc receptors on the basophils and mast cells
  • when IgE binds to these cells it triggers release of substances resulting in an allergic reaction
  • destroys parasitic worms and participates in allergies
40
Q

Describe the antibody IgD and its characteristics

A
  • this is the least abundant
  • bound to the surface of B lymphocytes, acts as an antigen receptors (BCR) triggering B cell activation
  • found in surface of B lymphocytes
41
Q

What are the three actions of antibodies? (Do not describe them)

A
  1. Compliment activation
  2. Opsonization
  3. NK cell activation
42
Q

Explain what “compliment activation” is

A

This is a system or group of roughly 20 plasma proteins that when activated, will cause a cascade of enzymatic reactions that result in cell membrane rupture of invading cells.

43
Q

Explain what “opsonization” is

A

This is receptors on macrophages, neutrophils, and eosinophils. These allow for the facilitation of phagocytosis by Leukocytes

44
Q

Explain what “NK cell activation” is

A

This is when antibodies bound to antigens on virus infected cells are recognized ny NK cells. NK cells; release protein that cause death of infected cells.

45
Q

What are NK cells?

A

Constitutes for 5-10% of circulating lymphocytes

  • neither T nor B cells
  • these are specialized to kill certain types of targeted cells
46
Q

What are lymph nodes?

A

Small bean shaped encapsulated lymphatic organs located along the pathway of lymphatic vessels

47
Q

What are the two types of lymphatic vessels? Explain them.

A

Afferent lymphatic vessels: brings lymph’s into the lymph node

Efferent lymphatic vessels: brings lymph away from the lymph node at the heilum.

48
Q

What is a hilum?

A

Concave depression on the concave surface that serves as an entrance/exit for blood and lymphatic vessels and nerves

49
Q

What are the three supporting elements of lymph nodes?

A

Capsule—> composed of dense irregular connective tissue

Trabeculae (CT septa)—> CT extension from the capsule that extends into lymph node forming a supportive framework

Reticular tissue—> reticular cells and reticular fibres form a fine supporting mesh work

50
Q

What does the parenchyma divide itself into?

A

The cortex and the medulla

51
Q

Explain the outlayer of the lymph node, the cortex.

A

The cortex is comprised of the sub scapular sinus—immediately below the capsule and receives lymph from the afferent lymphatics

52
Q

What is the function of cortical sinuses in lymph nodes?

A

These branch among the lymphatic nodules within the trabeculae

53
Q

What are lymphatic (lymphoid) nodules?

A

These are round aggregations of lymphocyte, which are mostly B-Lymphocytes

54
Q

What are the two types of lymphatic nodules? Explain them.

A
  1. Primary lymphatic nodule—> currently no immune response
  2. Secondary lymphatic nodules—> immune response to antigen presentation; these are paler and germinal centre of proliferating lymphocytes surrounded by cornea (mantle) of small mature lymphocytes
55
Q

What is the paracortex? What does it contain?

A

This is a deeper extension of the cortex, there is no lymphatic nodule, diffuse. These are mostly T cells.

This contains highendothelial venules (HEVs) that are specialized post capillary venules, entry point for most circulating lymphocytes.

56
Q

What is the medulla? (Not the brain portion)

A

The medulla is the inner region of the lymph node

57
Q

What are the three components of medulla? Explain them.

A
  1. Medullary cords—> branching cordlike masses (reticular fibre) contain mostly B lymphocytes and plasma cells, T lymphocytes, Macrophages, and dendritic cells
  2. Medullary sinuses—> dilated lymphatic vessels that contain lymph with a discontinued endothelium and extends from the cortical sinuses. These converge and empty into the efferent lymphatic vessel at the hilum
  3. Thymus—> bi lobed organ in superior mediastinum. These are the site of T cell differentiate (thymocytes) and proliferation. Only T lymphocytes resides in the thymus. These are fully formed and functional at birth.
58
Q

What is the general description of the thymus?

A
  • Bi lobed organ in superior mediastinum anterior to the heart
  • site of T cell differentiation (thymocytes) and proliferation
  • only T lymphocytes reside in thymus
  • fully formed at birth
  • around puberty is when T cells differentiate and proliferate
60
Q

What is the general architecture of the thymus? Only give a brief outline.

A 
—A connective tissue capsule surrounds the thymus
—trabeculae CT septa 
—epithelioreticular cells
—cortex 
—medulla
61
Q

What are epitheliorecticular cells?

A

These are features of reticular cells and epithelial cells that are supportive cells.

62
Q

What is the function of epithelioreticular cells?

A

Line capsule, trabeculae, and surround microvasculare to form blood thymus barrier. These form a cytoreticulum to support thymocytes

63
Q

Are there true CT fibres within a thymic lobule?

A

No

64
Q

Each lobule has an outer darker staining region, more densely packed thymocytes is found here. What is this called?

A

Cortex

65
Q

What is the medulla?

A

This is a paler inner staining area. It has epithelioreticular cells. This also contains Hassan’s corpuscles.

66
Q

What are Hassalls corpuscles?

A

These are large aggregates of concentrically wrapped epithelioreticular cells. These are thought to produce factors that promote T cell development

67
Q

What is the largest lymphatic organ in the body? What is the function of this?

A

THE SPLEEN!

This functions as a filter for blood and reacts immunologically to blood borne antigens (white pulp) . This is the main site of destruction and removes old and damaged RBC.

68
Q

What is the general architecture to the spleen? What are the two features?

A

This has a connective tissue capsule that surrounds the spleen as well as a trabeculae (CT septa).

The CT septa branches extends into parenchyma of spleen and contains myofibroblasts and is contractile which helps release RBCs

69
Q

What is the hilum of the spleen?

A

This is the indentation on the medial surface where the splenic artery entres

70
Q

What does the parenchyma of the spleen consist of? (3 factors)

A

Red pulp and white pulp

71
Q

What is white pulp?

A

This is a lymphatic nodule that may be primary or secondary, but mainly B lymphocytes.

72
Q

What are the two features of White Pulp?

A

Central artery—> a branch of the trabecular arteries.

Periarterial Lymphatic Sheath (PALS)—> cylindrical aggregation of lymphocytes around central artery. Mainly T lymphocytes.

73
Q

What is the pathway for the central artery in white pulp?

A

Here is the pathway: Splenic artery—> Trabecular Arteries—> Central Arteries—>Penicullar Arterioles—>Sinusoids

74
Q

What is red pulp made of? (3 factors)

A
  1. Splenic cords (billroth cords)—> reticular tissue that contains large numbers of RBCS rich in macrophages and lymphocytes.
  2. Splenic sinusoids (sinuses)—> sinusoidal capillaries that are discontinuous where old RBCs are removed
  3. Diffuse lymphatic tissue—> this includes MALT and the tonsils.
75
Q

What is MALT?

A

Mucosa Associated Lymphatic Tissue:
-this is where lymphocytes are dispersed diffusely throughout connective tissue or aggregated into nodules. These are not permanent cells.

Cell And Tissue Biology (4 decks)

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