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140 - Foundations of anatomy > Week 4 - Lymphatics and the immune system > Flashcards

Week 4 - Lymphatics and the immune system Flashcards

1
Q

Capillary structure and function?

A

→ Thin walls - decreases diffusion distance
→ Numerous and highly branched - large surface area for exchange
→ Lumen narrow - RBC squashed against side of capillary, reducing diffusion distance
→ Space between lining (endothelium), therefore white blood cells can pass through

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2
Q

How is interstitial fluid created?

A

(Due to hydrostatic pressure being greater than osmotic pressure)
→3L of fluid extra each day pushed out of capillaries compared to fluid held in.

Lymphatic system aims to remove some of this fluid.

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3
Q

What is osmotic pressure?

A

Exerted by proteins
Aims to keep fluid in the capillaries

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4
Q

What is hydrostatic pressure?

A

Pressure within blood vessels - driven by arterial blood pressure

This pressure pushes fluid out of capillaries

Hydrostatic pressure higher than osmotic pressure

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5
Q

What are the 2 components of the lymphatic system?

A
  1. Conducting system
  2. Lymphoid tissue
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6
Q

What does the conducting system involve?

A

Conducting (tubular) vessels → pick up interstitial fluid and carry fluid (“lymph”) to and from lymph nodes .

The tubular vessels include the lymphatic capillaries, the lymphatic vessels and the right and left thoracic ducts.

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7
Q

What does lymphoid tissue involve?

A

Primarily involved in immune responses and consists of lymphocytes and other white blood cells enmeshed in connective tissue through which the lymph passes.

Can be primary, secondary or tertiary.

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8
Q

What are lymphatic capillaries? (part of conducting system)

A

→ blind-ended bulbous tubes
→ endothelial cells in walls
→ allow entry of fluids, proteins and bacteria but prevent exit
→ merge into collecting lymphatics
→ lymphatic vessels contain smooth muscle and unidirectional valves to stop fluid moving backwards

AS BODY MOVES, HELPS TO PUMP LYMPH FLUID AWAY FROM CAPILLARIES AND TOWARDS LYMPH NODES

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9
Q

What does PRRs stand for?

A
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10
Q

What are the primary lymphoid organs and their function?

A

Thymus and bone marrow
→ production and early selection of lymphocytes
→ generate lymphocytes from immature cells

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11
Q

What are the secondary lymphoid organs and their function?

A

Lymph nodes, spleen, Peyer’s patches, adenoids, tonsils, appendix
→ maintain mature naive lymphocytes and initiate an acquired immune response
→ sites of lymphocyte activation

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12
Q

What is odema?

A

→ swelling in the tissues due to the excess fluid in the interstitial space
→ caused when filtration is increased to the extent that the lymphatics are unable to remove fluid fast enough or caused by dysfunctional lymphatic drainage

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13
Q

What is elephantiasis?

A

Nematode worm in lymphatic vessels

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14
Q

Why may lymph node filtration be increased?

A

The net flow of water across capillary wall = determined by balance between osmotic pressure and the hydrostatic pressure.

SO diseases such as kwashiorkor increase filtration

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15
Q

What is kwashiorkor?

A

→ Protein in capillaries reduced due to malnutrition
→ Less water held onto inside capillaries - more water pushed out due to hydrostatic pressure
→ Lymphatic system cannot deal with it fast enough
→ Leads to swelling in the abdomen

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16
Q

What physical defence is provided by the body?

A

Skin, epithelium of the airways, gut and mucocilary escalator

→protects against infection by bacteria, viruses, fungi and parasites
→skin contains sweat glands and sebaceous glands that secrete fatty acids that inhibit the growth of bacteria on the skin surface
→ cilia beat and get rid of pathogens entering lungs

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17
Q

Function of the immune system?

A

To distinguish self from non-self

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18
Q

Why do autoimmune diseases occur?

A

The immune system has malfunctioned and it starts to attack healthy tissues in the body.
e.g. rheumatoid arthritis, crohn’s disease

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19
Q

What are the 2 parts to the immune system?

A

Innate immune system

Acquired immune system

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20
Q

Key points to innate immune system?

A

→ present from birth
→ inflammatory response
→ fast
→ non-specific

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21
Q

Key points to acquired immune system?

A

→ specific
→ slower
→ powerful
→ builds over time

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22
Q

What are the 4 cardinal signs of inflammation?

A

heat
swelling
pain
redness

23
Q

What are chemical mediators?

A

Communicating chemicals in the body
Interact with other chemicals to cause response

24
Q

Examples of chemical mediators?

A

histamine
complement
kinins
prostaglandins

25
Q

What 2 response chains can tissue injury lead to?

A

Release of chemical mediators

Release of leukocytosis inducing factor

26
Q

What is leukocytosis?

A

Increased numbers of white blood cells in the bloodstream

(they migrate to the injured area)

27
Q

What is margination?

A

Leukocytes cling to capillary walls

28
Q

What is diapedesis?

A

Leukocytes pass through capillary walls

→ leads to phagocytosis of pathogens and dead tissue cells
(neutrophils - short-term, macrophages - long-term)

29
Q

What does phagocytosis of pathogens and dead tissue cells lead to?

A

(pus may form)
The area is cleared of debris which leads to healing

30
Q

What does the release of chemical mediators lead to?

A

Vasodilation of arterioles

Increased capillary permeability

Attraction of neutrophils, monocytes and lymphocytes to the area (chemotaxins)

31
Q

What do leaked clotting proteins in the inflammatory process lead to (post exudate formation)?

A

→ Walling - off process (blood clots wall off area to prevent injury to surrounding area)
→ A temporary fibrin patch forms scaffolding for repair

Allows for healing

32
Q

What are the stages of injured tissue healing ?(simplified)

A
  1. Damaged tissues attract mast cells which release histamine, which diffuses into the blood vessels.
  2. Histamine causes the vessels to dilate and become leaky; complement proteins leave the vessels and attract phagocytes.
  3. Blood plasma and phagocytes move into infected tissue from the vessels.
  4. Phagocytes engulf bacteria and dead cells.
  5. Histamine and complement signalling cease; phagocytes are no longer attracted.
  6. Growth factors from white blood cells and platelets stimulate cell division in skin cells, healing the wound.
33
Q

What causes the cardinal signs of heat and redness?

A

Chemical mediators produce vasodilation of arterioles (small blood vessels).

This leads to local hyperemia - increased blood flow to the area.

As a result, this leads to heat and redness.

The increased temp. increases the metabolic rate of cells, aiding the healing process.

34
Q

Examples of chemical mediators?

A

histamine, complement, kinins, prosteglandins etc

35
Q

What causes the cardinal signs of swelling and pain?

A

Chemical mediators produce increased capillary permeability which leads to capillaries leaking fluid (exudate formation).

This fluid leads to many things, one being leaked protein-rich fluid in tissue spaces.

This can result in temporary limitation of joint movement before healing can occur.

36
Q

What is a fever?

A

Elevated temperature, caused by pryogen which acts on the hypothalamus

37
Q

What is the hypothalamus and what is it’s function?

A

→ Thermoregulatory centre
→ Has set temperature (36.9 degrees)
→ Resets set point
→ Mediated by prostaglandin - E2

Antipyrectics e.g. paracetamol reduce the amount of PGE2 made, therefore reducing fever.

38
Q

Benefits and drawbacks of fever?

A

B - Some leucocytes work better with increased temperature, some bacteria work worse

C - Can cause brain damage (over 42 degrees) and causes a person to feel unwell

39
Q

What are PRRs?

A

Pattern recognition receptors (embedded in phagocyte)

40
Q

What are PAMPs?

A

Pathogen associated molecular markers (found on pathogens)

41
Q

How does non-specific phagocytosis occur?

A

→ PRRs are embedded in the phagocyte and match the PAMP found on the pathogen.
→ Relatively few PRRs needed as PAMPs are common across wide range of pathogens.
→PRR on e.g. macrophage binds with PAMP, initiating phagocytosis and causing the release of cytokines and cytotoxins.
→ Phagocyte breaks up pathogen and displays an antigen on it’s MHC - in this way the antigen from the phagocytosed pathogen is being shown to other cells (T cells)

42
Q

What is an MHC?

A

Major histocompatibility complex

There are two types of MHC (1+2) - all nucleated cells have MHC-1 which are specific for that person whereas RBC’s do not have MHC-1.

43
Q

What are natural killer cells and what do they do?

A

→ Type of lymphocyte (2% of lymphocyte population).
→ Specific.
→ Identify self cells that lack MHC-1 (so don’t attack RBCs) or target injured, infected or cancer cells that are expressing PAMP like molecules.
→ All our cells should have MHC-1 - some viruses/cancers cause cells to not have this.
→ NKC’s produce perforins and granzymes.
→ The cells are killed, macrophages are then activated to remove the debris.

44
Q

What are perforins?

A

Chemicals which create pores in the cell being target

45
Q

What are granzymes?

A

Which enter the cells through channels created by perforins and then destroy the cells

46
Q

What is complement?

A

→ A group of 20 proteins that normally circulate the blood in an inactive, non-functional form.

→ They become activated in a complement cascade, a series of reactions in which each component activates the next component

→ Activated complement proteins provide protection in several ways

47
Q

How do activated complement proteins provide protection in several ways?

A

→ Some attach to form a hole in the membrane of bacteria cells, resulting in lysis (breaking up) of the cell

→ Complement proteins attached to the surface of bacterial cells also stimulate macrophages to phagocytise the bacteria

→ Attract immune system cells to sites of infection and promote inflammation

48
Q

What is the acquired immune response?

A

Slow but powerful, has a memory.

2 types:
→ Humoral (antibody-mediated)
→ Cell-mediated

49
Q

Humoral response key points?

A

Mediated by: B Lymphocytes

Originates in: Bone Marrow

Matures in: Bone Marrow

Receptor: Antibody

50
Q

Cell-mediated response key points?

A

Mediated by: T Lymphocytes

Originates in: Bone Marrow

Matures in: Thymus

Receptor: T Cell receptors

51
Q

What is an antigen?

A

A biomolecule such as a protein or sugar that binds to a specific antibody

52
Q

Stages of the humoral immune response?

A

This process fights pathogens free in bodily fluids

Step 1: Naive B cell activation → Antigen binds to Naive B cell receptor.

Step 2: Clonal selection →Division of that activated B cell.

Step 3: Differentiation → Plasma cells (make antibodies) and memory B cells (has specific antibody in cell membrane and remembers antigen 2nd time).

Step 4: Plasma cells produce antibodies that bind to the antigen memory B cells for immunologic memory/secondary response.

53
Q

Stages of the cell-mediated response?

A

1) T-Cells are mobilised when they encounter a cell such as a dendritic cell or a B cell that has digested an antigen and it is displaying antigen fragments bound to it’s MHC ii molecules.

2) Cytokines help T-cell mature

3) The MHC-antigen complex activates the T-cell receptor and the T cell secretes cytokines

4) Some cytokines spur the growth of more T-cells;

→ Some T-cells become cytotoxic cells and track down cells infected with viruses

→ Some T-cells become helper cells and secrete some cytokines that attract fresh macrophages, neutrophils, other lymphocytes and other cytokines to direct recruits once they arrive on the scene.

54
Q
A

140 - Foundations of anatomy (8 decks)

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