The First Line of Defence

[blank_start]Keratinised[blank_end] Cells are the strong, outermost layer of skin cells in the [blank_start]epidermis[blank_end]. They stop pathogens from getting into the body through the skin and get replaced often by new cells.

In a [blank_start]Keratinocyte[blank_end] Cell, the [blank_start]Cytoplasm[blank_end] hardens to become [blank_start]Keratin[blank_end]. We now call this the Keratinised Cell.

When the skin is damaged, pathogens find it easier to get in. The body needs a fast way to repair, forming blood clots and scabs.

When damaged cells and torn capillaries are exposed to [blank_start]air[blank_end], they release enzymes like [blank_start]thrombin[blank_end] to signal to the protein [blank_start]fibrinogen[blank_end] to enter the broken tissue.

If enough clotting agent is present, the protein [blank_start]fibrinogen[blank_end] becomes [blank_start]fibrin[blank_end] that allows red blood cells to be "tied up" and trapped, forming a clot. The clot dries, becoming a protective scab until the skin cells can regrow.

Some parts of the body are unfortunately more open to pathogens. One of these areas is the eye. Luckily, the eye has ways of getting rid of foreign bodies. First, [blank_start]eyelashes[blank_end] capture the pathogen, and then an enzyme called [blank_start]lysozyme[blank_end], found in tears, destroys it.

The respiratory system, leading to the [blank_start]lungs[blank_end] is another part of the body that needs a lot of protection thanks to the open spots of the [blank_start]mouth[blank_end] and nose.

Two types of cells protect the respiratory system. [blank_start]Goblet[blank_end] cells release sticky mucus from their vacuoles. They carry [blank_start]mucin[blank_end] proteins that become mucus upon excretion. [blank_start]Ciliated Epithelial[blank_end] Cells are covered in many [blank_start]cilia[blank_end] (tiny, hair-like structures) that beat back and forth to remove mucus from the respiratory tract.

What is the role of the mucus? (Tick AT LEAST ONE option)

Stomach (Gastric) Acid Contains:

When we ingest food, we also often ingest pathogens like salmonella. Gastric acid excretes [blank_start]enzymes[blank_end] to destroy these pathogens. The [blank_start]high PH[blank_end] of the stomach acids can also help to destroy pathogens and speed up enzyme activity.