Integumentary System

Question 1

What are the two main parts of the skin?

Answer 1

The epidermis which is the superfixial, thinner, avascular portion which is composed of epithelial tissue.

The dermis which is the deeper, thicker, vascular portion which is composed of connective tissue.

There is also the subcutaneous layer which is deep to the dermis which consists of areolar and adipose tissue. It serves as a storage depot for fat and contains large numbers of blood vessels. It is not, however, part of the skin.

Question 2

What is the structure of the epidermis?

Answer 2

The epidermis is composed of keratinised stratified squamous epithelium.

Question 3

What are the four main cell types in epithelium?

Answer 3

• Keratinocytes:* are the most common cell type. They produce kerain and lamellar granules. There are several distinct layers of keratinocytes in various stages of development.
• Melanocytes*: produce melanin and have long, slender proection which extend between the keratinocytes and transfer melanin granules to them.
• Langerhans cells:* are epidermal dendritic cells which participate in the immune response against microbes that invade the skin, by helping other cells recognise an invading microbe and destroy it.
• Merkel cells* are located in the deepest layer of the epidermis, where they contact the flattened process of a sensory neuron which detects touch sensation.

Question 4

What is the structure of the dermis?

Answer 4

The dermis is composed of dense, irregular connective tissue containing collagen and elastic fibres. It is much thicker than the epidermis.

Question 5

What are the cellsand structure found in the dermis?

Answer 5

The cells found in the dermis are fibroblasts (predominant), macrophages (few) and adipocytes* *(around th boundary with the subcutaneous layer).

The structures found in the dermis are blood vessels, nerves, glands and hair folicles.

Question 6

What are the functions of the integumentary system? What other systems are involved in these function?

Answer 6

• Sensation:* sensory receptors and nerves in the epidermis and dermis percieve sensation (nervous system)
• Thermoregulation*: temperature change is detected by sensory receptors (nervous system) which stimulates a response. High temperatures will result in the nervous system increasing the activity of eccrine sweat glands. Vasodilation also is initiated (cardiovascular) which increases the amount of heat lost. Low body temperature decreases the activity of eccrine sweat glands (nervous system), causes vasoconstriction (cardiovascular) and also causes skeletal muscles to contract producing heat (muscular). All these processes are controlled by the nervous system.
• Vitamin D synthesis:* synthesis of vitamin D requires the activation of a precursor moleule (cholesterol) in the skin by UV light. Subsequent steps for the synthesis of vitamin D occur in the liver and kidney (digestive). Vitamin D is essential for the absorption of calcium from the GIT (digestive) as it actually acts as a hormone (endocrine) and hence the maintenance of blood calcium levels and bone health (skeletal).
• Protection:* the skin protects infiltration from many pathogens (immune).