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Accessory Structures
• Accessory structures are tissues that are located in the dermis and epidermis that are not considered skin• These structures include hair,
nails and glands• These structures play a vital role
to in the function and purpose of the skin
Accessory Structures
• Accessory structures derive from the epidermis during fetal development• This means that the same cells
that create the epidermis also create all of the accessory structures• Since they come from the
epidermis during development, we often refer to them as epidermal derivatives
Accessory Structures• The accessory structures are
located in the dermis• However accessory structures
should have access to the outside environment through the epidermis• The only times this does not
happen is if a gland is blocked or a hair is ingrown
https://www.youtube.com/watch?v=zWh_eA-9S7E
https://www.youtube.com/watch?v=Aj7aRGQ0DyI
Hair
• Hair is an accessory structure that projects from the dermis to the outer environment• It covers most parts of the body• This excludes the palms, bottom
and sides of feet, lips and parts of the genitals• Only around 25% of the bodies hair
is located on the head• The rest are located around the
body
Hair
• Hair serves three main functions• Insulate the skin• Protect the skin from damage• Sense changes to the skin from
the environment
• These different functions happen all over the body in many different ways• The purpose they serve makes
sure we survive
Hair Structure
• Hairs are non living structures that are pushed upward from the dermis• Hairs originate from a point
called the hair follicle• This hair follicle is surrounded by
connective tissue (root hair plexus) and smooth muscle (arrector pili)
Hair Structure
• Hairs tissues are located below the surface and above the surface• The part that is below the
surface and anchors the hair into the skin is called the hair root• The part that is above the
surface and exposed to the environment is called the hair shaft
Hair Fun Facts
• Hairs are present for around two to five years• During this time they grow
around 8mm (1/3 of an inch) a month• When new hairs grow, they push
out the old hairs• Humans lose around 100 hairs
from their head a day
Hair Fun Facts
• There are two main different types of hair• Vellus hairs are located all over
your body and are less thick and lightly colored• Terminal hairs are heavy and
darkly pigmented• Types of hairs that are produced
can change with age and the levels of hormones produced
Hair Fun Facts
• Hair color is derived from melanin• Melaninicytes near the hair
follicle produce melanin that give the hair is color• The melanin type produced is the
color of hair• As hair grows older, less melanin
is produced and air finds its way into hair• This causes hair to have a white
or grey appearance
Hair Fun Facts
• Hair coloring can produce a false color on the shafts of hair• However these hair dyes need to
penetrate the hair so they damage the outer cuticle of the hair• This often leaves hair damaged
and thin• Conditioners and specialized
shampoos can partially restore the cuticle and leave hair hydrated
Video
• Not everyone’s hair grows the same…
• http://videos.howstuffworks.com/discovery/30742-one-step-beyond-hypertrichosis-video.htm
Video
• Even more differences… • www.youtube.com/watch?v=OU93tt3w_eQ
• http://www.dailymail.co.uk/health/article-2647395/Alopecia-big-life-doesnt-define-Teenager-15-lost-hair-disease-fronts-new-campaign.html
Nails
• Nails protect the exposed dorsal surfaces of the fingers and toes• They also provide physical
protection to the fingers when gripping an object• They give it a backing so the cells
do not distort to the point where they are not able to hold the object
Nails
• The nail body is the visible portion of the nail that covers part of your finger• This part of your finger that is
covered by the nail body is the nail bed• The nail hyponychium occurs at the
far distal edge of the nail and provides a seal to protect the nail bed• This part of your body requires
protection due to the amount of physical damage that It can and will receive over its lifetime
Nails
• The nail grows from an area called the nail root• The nail root is an epidermal fold
that is not visible from the surface• The deepest portion of the root
lies very close to the bones in the fingers and toes• The cuticle is a section of nail root
that comes over the exposed surface of the nail
Nails
• The condition of nails often tells a story of the health of an individual• Persons that have yellowing nails
might have various disorders that can inhibit or damage the nails during development• Other signs of problems are
pitted nails or nails that are concave as opposed to convex
Sebaceous Glands
• Found within the skin there are two major exocrine glands• These glands are used to
lubricate/hydrate the skin and maintain levels of temperature• Sebaceous glands are glands
that discharge an oily secretion • Sweat glands are designed to
release a
Sebaceous Glands
• Sebaceous glands are linked to a hair follicle • This means that they share their
opening to the skin with a follicle of hair• They produce a large quantity of
lipids that will dump onto the hair as it grows and the surrounding skin
Sebaceous Glands
• The mixture of lipids that are produced is called sebum• Sebum is made of cholesterols,
triglycerides, proteins and electrolytes• It serves many purposes• It inhibits microbial growth• It lubricates and protects the hair
shaft• It lubricates and protects the skin
Sebaceous Glands
• Sebaceous follicles are large sebaceous glands that are not associated with hair follicles• These are located mostly on the
face, back, chest, nipples and genitals• These are most active during
fetal development and during puberty
Sweat Glands
• There are two main types of sweat glands• Apocrine sweat glands are
secrete their products onto hair follicles• Merocrine sweat glands
discharge their products onto skin
Sweat Glands
• Apocrine sweat glands are coiled under the skin• They are located in the arm pits,
around the nipples and in the genitals• They produce a sticky and oily
secretion• They start producing at puberty
and will continue for the rest of your life
Sweat Glands
• The sweat produced by these glands is rich in nutrients and can be a good source for bacteria• This tends to create a large
amount of odor• Several different methods can be
used to neutralize these odors, however many can have side effects
Sweat Glands
• Merocrine sweat glands will produce a very watery sweat that is dumped directly on the surface of the skin• These sweat glands are designed
to help cool the surface of the skin• This robs heat from the body
and will cool the body quickly
Sweat Glands
• The sweat produced by these glands is around 99% water• Small amounts of other chemicals
are in the sweat • NaCl is the most major
• It functions to cool the skin• It also helps dissolve/dilute other
harmful chemicals that can be on the skin• It also helps excrete water or
electrolytes to maintain homeostasis
Video
• https://www.youtube.com/watch?v=IAAt_MfIJ-Y