Respiratory

Question 1

What type of sensitivity is asthma associated with and why ?

Answer 1

Type 1 hypersensitivity

This is mediated by IgE binding to mast cells this leads to an inflammatory response

Question 2

Explain the bodies initial reaction during type 1 sensitivity in asthma

Answer 2

1- usually an environmental trigger eg smoke
2- dendritic cells pick this up and present it to the TH2 cells
3 - TH2 cells produce the cytokines IL-4
4 - IL-4 produces IgE antibodies, these coat mast cells and stimulate them to release granules like histamine, luekotrines and prostaglandins
5 - This causes constriction of smooth muscle in the bronchioles and increase secretions

Question 3

What’s involved in the atopic triad

Answer 3

Asthma
Atopic dermatitis
Allergic rhinitis

Question 4

What’s the name of the sputum you might see in asthmas patients ?

Can it be dangerous

Answer 4

Curshmann spirals

These are spiral shaped mucus plugs which are essentially elongated mucus casts from the small bronchi of people with bronchial asthma - these not only block exchange of air but can block inhaled medicines getting to the site of inflammation

The sputum may also have Charcot-Leyden crystals which are needle shaped and are from the break down of eosinophils

Question 5

Explain methemoglobinemia

Answer 5

Within the red blood cell the iron is usually in a ferrous state, this means that the iron has lost two electrons to form Fe2+

Methemoglobin is an oxidised form and normally forms spontaneously. In methglobin one of the iron molecules is in the ferric state which means that the iron has lost three electrons instead of two to form Fe3+

The other three heme groups still have iron in Fe2+ and try to componsate and hold onto the o2 but this can be detreimental because they don’t let it go again leading to tissue hypoxia