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btec applied science unit 12infection and diseases
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BTEC
PEARSON (PEARSON)
Applied Science 2016 NQF
Unit 12 - Diseases and Infections
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UNIT 12D
In this assignment I will explain how various components of both the specific and non-specific
defence systems, work to help protect the immune system from pathogens. The specific immune
system is the third line defence of the body and it is the supreme immune response of the body
against a particular pathogen. Whilst the non-specific immune system is within the first- and second-
line defence of the body, and is used as a response against pathogens. I will also be evaluating the
humoral and cell-mediated responses, also used to protect the body from pathogenic materials.
Section A: Non-specific immune system
The non-specific immune system
1. Physical barrier, these defences provide the bodies most basic form of non-specific defence.
they prevent microbes from reaching tissues that are susceptible to infection. The barriers
consist of tightly joined cells preventing invaders from crossing through deeper tissue.
Skin, it is composed of two main layers. The epidermis, the external layer of the skin
and the dermis. The epidermis protects inner tissues from harmful external effects
such as air pollution, smoke and dryness. The epidermis is composed of three types
of cells:
1. The keratinocyte cells, where the majority of the cells are arranged in layers,
the upper layer is caked the corneum layer, middle layer is made up of
elongated squamous cells while the bottom layer is the basal layer, as the
upper layer of skin is deeply exposed to harmful external effects, cells in the
basal layer move upwards forming the corenum layer consisting of many
dead cells adhering to one another with a biological adhesive, preventing
the penetration of harmful bodies
2. Melanocyte cells are found at the bottom of the epidermis. The cells form
melanin, a chemical substance giving the skin its pigmentation. Melanin
formed in dark skinned people is more effective in blocking the sun’s rays
than that formed in light skinned people’s skin.
3. The Langerhans’ cells are found in the upper epidermis layers, the cells
belong to the body’s immune system and their role id to identify foreign
substances that penetrate the skin such as, bacteria or viruses. The
Langerhans’ cells secrete lymphocytes, which aim to destroy foreign bodies,
protecting the body.
The dermis layer is accountable for the supply of both support and food material
to the epidermis. The layer is composed of collagen and elastin fibres. The
collagen is a type of protein built as thick interwoven fibres, facing in different
directions keeping the skin strong and allowing it to be stretched without
tearing. Whilst, the elastin fibres give the skin its elasticity, here the fibres are
thin behaving similar to rubber, allowing the skin to return to its original form.
The dermis contains blood vessels that nourish the skin and provide it with food
and oxygen, it also contains the sebaceous glands, which secrete an oily
substance coating the skin keeping it moist and protected.
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