The second line of defence

The second line of defence

The second line of defence

1. Fever

2. Phagocytosis

3. Inflammation

Fever

1. Increases phagocytic activity

2. Fights against microorganisms

Phagocytosis

A process in which microorganisms or dead cells are trapped and digested by phagocytes (neutrophil/monocyte)

Explain the first stage of phagocytosis.

Phagocyte extends its pseudopodium towards the bacteria and envelops it

Explain the second stage of phagocytosis.

Bacterial ingestion forms phagosome.

Explain the third stage of phagocytosis.

Phagosome combines with lysosome that secretes lysozyme into the phagosome

Explain the fourth stage of phagocytosis.

Bacterium in the phagosome is destroyed by the lysozyme.

Explain the fifth stage of phagocytosis.

Phagocyte expels the remains of the digested microorganism out of the cell through exocytosis.

Inflammation

The immediate response that destroys and neutralises harmful actions of microorganisms and toxins at the early stages of infection

Explain the first stage of inflammation.

Damaged tissue releases histamine. Histamine stimulates an immediate inflammatory response.

Explain the second stage of inflammation.

1. Histamine causes blood capillaries to expand for more blood flow to the infected area.

2. Histamine increases the permeability of blood capillaries to phagocytes.

3. Phagocytes and clotting factors will accumulate in the infected area.

Explain the third stage of inflammation.

The blood clotting mechanism is triggered.

Explain the fourth stage of inflammation.

Phagocytes carry out phagocytosis.