Lecture 36 - Immune System Overview Flashcards

1
Q

What is the immune system?

A

It’s a diffuse collection of cells and organs that are responsible for the ability to resist infection and disease

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2
Q

Name 3 examples that the immune system protect the body against?

A
  1. Pathogens
  2. Toxic material
  3. Own misfunctioning cells
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3
Q

Function of physical barriers against infection

A

Anatomical and physiological mechanisms prevent entry of foreign organisms and substances

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4
Q

Function of cell-mediated immune responses

A

Innate and adaptive defence responses that rely on WBC activity

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5
Q

What are physical barriers made of?

A

Structural features - work to prevent a pathogen from entering the body (ex. skin and hair)

Chemical secretions - used to neutralize and destroy pathogens (ex. lysozyme, stomach acid)

These defences are created by non-immune cells

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6
Q

What is the most important physical barrier of the body? Why?

A

The integument. It has:

  1. Secretions - washes away/destroys potential pathogens
  2. Hair - keeps away potential hazards away from the skin surface
  3. Stratified squamous epithelium - many closely interlocked layers which keep intruders out
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7
Q

What is the purpose of mucous membranes?

A

It lines the digestive, respiratory, urinary, and reproductive tracts and provide protection against foreign substances and pathogens

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8
Q

What are immune system responses mediated by?

A

WBCs - both innate and adaptive immune responses rely on the activation and signalling of specialized immune cells

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9
Q

Where do WBCs come from and how are different WBCs divided?

A

They all come from red bone marrow

WBCs are divided based on:
- Function
- Anatomy
- Developmental history

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10
Q

What are the 3 functions of immune responses that are mediated by WBCs?

A
  1. Detection/recognition of invaders or abnormality
  2. Secretion of chemicals that alter the local environment or signal to other cells
  3. Destruction of foreign particles, pathogens, and diseased cells

No one type of WBCs performs all of these functions, but some are involved in more than one

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11
Q

What are the 2 types of immune responses

A

Innate responses - nonspecific responses that react to any threat they detect. They are present from birth

Adaptive responses - specific and powerful responses triggered by exposure to particular antigens. They must be “learned” over the lifetime

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12
Q

What does the lymphatic system consist of?

A

It consist of vessels that move lymph through the body, and tissues that produce or house lymphocytes

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13
Q

What is lymph?

A

It’s a connective tissue that resembles blood, but lacks most of the cells and plasma proteins

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14
Q

T/F? The lymphatic system is synonymous with the immune system

A

False - it is not synonymous with the immune function

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15
Q

What are the 2 main non-immune functions of the lymphatic system?

A
  1. Return of filtered fluid from ISF to plasma
  2. Transport of digested and absorbed lipids
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16
Q

What are similarities of lymphatic vessels and blood vessels?

A
  • blood and lymph vessels have an endothelial wall around a lumen
  • larger vessels have a smooth muscle layer and contain valves that keep lymph flowing one way
17
Q

What are 3 differences of lymphatic vessels and blood vessels?

A
  • lymph capillaries have blind ends
  • all lymph vessels are typically more permeable along their length
  • there is no equivalent of a heart to create pressure gradients to move lymph; it relies on smooth muscle contraction (and skeletal muscle pumps)
18
Q

What does the lymphatic system consist of?

A

Lymphocytes, lymph nodes, and lymphoid tissues and organs

19
Q

T/F? Lymphoid organs and lymphoid tissues all belong to the immune system and contain lymphocytes (a subset of WBCs)

A

True

20
Q

Examples of primary organ/tissue and their function

A

They are involved in production and maturation of lymphocytes

  • Bone marrow
  • Thymus
21
Q

Examples of secondary organ/tissue and their function?

A

Contains mature and functional lymphocytes

  • Lymphoid tissue
  • Lymph nodes
22
Q

Characteristic of tissues and organs

A

Tissues - lack a distinct capsule
Organs - have a distinct fibrous capsule

23
Q

Are all WBCs lymphocytes? Why?

A

No:
Lymphocytes are a developmental classification; all lymphocytes come from lymphoid stem cells

All other WBCs develop from myeloid stem cells (like RBC and platelets)

24
Q

T/F? All lymphocytes are associated with adaptive immune responses

A

False - Most are, but not all, lymphocytes are associated with adaptive immune responses

Ex. T and B cells are associated with the adaptive immune response, but NK cells are associated with the innate immune response

25
Q

Describe the structural make up of lymph nodes

A

They are encapsulated structures which are connected to lymph vessels and house mature lymphocytes

26
Q

How does lymph flow in lymph vessels?

A

Lymph within lymph vessels flows through lymph nodes, which are often clustered at joints and where peripheral lymph vessels meet the torso

27
Q

How do lymph nodes stimulate immune responses?

A

They filter lymph and act as staging posts for generating adaptive immune responses to antigens detected by the innate immune system

28
Q

Where do antigens that WBCs have detected enter?

A

They enter the lymph node through afferent vessels and encounter B and T cells in the cortex and paracortex

29
Q

What are activated lymphocytes?

A

Activated lymphocytes that have acquired specific adaptive immune responses leave the lymph nodes through efferent vessels

30
Q

Function of marcophages and where are they located?

A

They are in the medulla and help destroy pathogens that make it into the lymph vessels, before they reach the bloodstream

31
Q

What are secondary lymphoid tissues?

A

They are mature lymphocytes that are not associated with lymph nodes. These tissues contain aggregations of lymphocytes that act like lymph nodes, but possess structural differences

32
Q

What are lymphoid nodules?

A

Regions of lymphoid tissue that are typically associated with mucosa

33
Q

What are Mucosa Associated Lymphoid Tissue (MALT)?

A

They are lymphoid nodules that are aggregations of lymphocytes. They lack a distinct capsule

34
Q

What are 4 ways lymphoid nodules distinguished from lymph nodes?

A

Lymph nodules:

  • have no capsule
  • no afferent vessels
  • are found in areolar tissue within mucous membranes
  • have the highest density where there are many live pathogens in the lumen (ex. colon)
35
Q

How do lymph nodes and lymph nodules generate adaptive immune responses?

A

They contain B and T cells that generate the adaptive immune responses

36
Q

What is the spleen?

A

It is a secondary lymphoid organ containing large amounts of lymphoid tissue that filters and monitors the blood

37
Q

What are the 3 functions of the spleen?

A
  1. It has non-lymphoid functions, such as recycling old RBCs in its red pulp
  2. Like a lymph node, it contains clusters of lymphocytes within its white pulp, which can generate adaptive immune responses
  3. It filters blood plasma, not lymph. It acts like a lymph node for the blood
38
Q

Describe the path of lymph flow through a lymph node

A

Afferent lymphatics -> Subcapsular space -> Outer cortex -> Paracortex -> Medullary sinus -> Efferent lympathics