Accessory Structures of the Skin
The accessory structures of the skin are usually included in human biology course modules about the skin (integumentary system). An alternative name for the accessory structures of the skin is the accessory structures of the integumentary system.
Definition of the Accessory Structures of the Skin
The accessory structures of skin (see also the structure of skin) are the structures that develop from the epidermis of an embryo.
List of the Accessory Structures of the Skin
- Hairs (which extend from hair follicles),
- Glands located within the layers of the skin - there are 3 types:
- Sebaceous Glands, also called "oil glands" - secret sebum
- Sudoriferous Glands, also called "sweat glands" - produce and secret sweat
- Ceruminous Glands, in the outer ear - (in combination with sebaceous glands) secret cerumen = "earwax"
- Nails.
As is true of most structures within the body, it is possible to describe the accessory structures of the skin in various levels of detail according to the level of study and the marks allocated for the answer (or answer to part of a question) in a test or exam.
Structures and Functions of the Accessory Structures of Skin
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Accessory Structure |
Structure (brief description) |
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Functions |
1. |
Hair(s) |
It is useful to be able to describe the structure of hair by drawing a diagram of a hair follicle. |
|
Protection, e.g. |
- Hair on scalp protects the scalp from potentially harmful effects of solar radition (i.e. sun damage).
- Eyebrows and eyelashes protect the eyes from small particles e.g. fine grains of sand or smoke - not total protection.
- Hair in the nostrils protects against inhalation of small particles such as dust, dirt, or even small insects.
|
2. |
Glands - in general |
Pressure / touch, heat / cold, pain |
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See following functions of these types of glands: |
|
2a. |
Sebaceous Glands |
Most sebaceous glands are connected to hair follicles. |
|
- Secrets an oily substance called sebum.
Sebum prevents hair becoming too dry, prevents skin becoming too dry (due to exessive evapouration of water from the skin) and so helps keep the skin soft and
able to perform functions of the skin well.
- Sebum also inhibits growth and reproduction of certain bacteria.
|
2b. |
Sudoriferous Glands |
There are two types of sweat glands: |
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Production of sweat, also called perspiration |
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- Apocrine sweat glands - apocrine sweat gland ducts open into hair follicles. Apocrine sweat glands are located in the armpits, pubic regions and areolae (pigmented areas) of breasts and are active from puberty.
- Eccrine sweat glands - eccrine sweat ducts terminate at sweat pores at the surface of the epidermis (= outer layer of skin). Eccrine sweat glands are located throughout most of the skin (exceptions nail beds, margins of lips, eardrums).
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The functions of sweat / perspiration include:
- Temperature regulation of the body
(an important function of the skin).
- Elimination from the body of certain waste products/substances.
Also, lactation = secretion of milk from breasts (breasts = mammary glands) are modified sudoriferous glands. |
2c. |
Ceruminous Glands |
Located only in the external auditory canal, also known as the "outer ear". Some ducts of the ceruminous glands open directly onto the surface of the outer ear. Other open into ducts of sebaceous glands - see 2a., above.
The combined secretion of both the ceruminous and sebaceous glands is earwax.
The medical term for 'ear wax' is cerumen. |
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- Cerumen provides a sticky barrier that helps protect the ear against "foreign bodies" such as particles of dust, soot or anything else that floats in the air.
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3. |
Nails |
It is useful to be able to draw a diagram of the structure of a nail (structure of nails).
A page about nail structure will be added here soon. |
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- Protects the ends of fingers and toes.
- Facilitates grasp and manipulation of small objects.
- Enables scratching / grooming.
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See also pages about the structure of skin, the functions of skin, skin pigmentation, skin lesions and skin disorders.
