The Integumentary System

The integument (skin) is the largest organ in the body. Structurally, the skin can be divided into two parts:-

  1. Epidermis Рthinnest and outer portion of the skin. Generally made of 5 layers of keratinocytes (skin cells) of different stage of differentiation i.e. stratum corneum, startum lucidum, startum granulosum, startum spinosum, and stratum basale (stratum=layer)). On top of these, there are other specialized cells in the epidermis: melanocytes, Langerhans, Merkel cells.
  2. Dermis – thickest and deeper part of the skin. Is connective tissue which contains skin accessories such as hair and hair follicles, skin glands, sensory receptors, and nails.

Deeper than dermis is the subcutaneous / hypodermis layer which contains adipose (fat) tissue and areolar connective tissue. The hypodermis is not part of the skin but function as anchor for the skin. It also contains blood vessels.

 

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The skin carry several functions and is important at maintaining body homeostasis:

  1. thermoregulation
  2. protection
  3. vitamin D synthesis
  4. blood reservoir
  5. sensation
  6. excretion and absorption

 

 

Here are detailed explanation on the integumentary system:

 

 

 

Exercises

 

1- Explain how the skin regulate body temperature when a person is jogging in a hot day and a person taking a quick swim in cold weather.

2- Explain what causes the different skin colour in a Caucasian (e.g. an English man) and an Asian. Why do skin cancer (malignant melanoma) happens more often in people with lighter skin compared to people with darker skin colour.

3- Explain why some drugs can be delivered through the skin.

4- Identify the reflex pathway involved when a hand touches a hot kettle.

 

 

 

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