Exploring the bodys biggest organ

1
Exploring the bodys biggest organ

• An organ is a portion of the body that has
  special functions to perform for the entire body.
• When you think of an organ you may think of the
  heart, brain, or liver but the skin is also an
  organ and in fact is the largest organ.
• The skin is connected to the rest of the body and
  it functions and communicates through nerves and
  three kinds of vessels, arteries, veins and
  lymphatics.

2
What the skin does

• Protection
• Against larger organisms - Lice, worms
• Against smaller organisms - bacteria, viruses
• Against powers and fluids - dirt, water,
  chemicals
• Ultraviolet light
• Controls body temperature
• Makes Vitamin D for the body
• Heals itself
• Lasts for your entire life but changes with age
• Acne, wrinkles, hair changes

3
Organisms that affect the skin come in different
sizes-

• Look in the louse box-and pick some lice (dont
  worry not real just celery seeds) and put on
  your skin. Use the surface microscope and compare
  the size of the louse with that of a hair. On
  the scalp lice lay eggs on hairs. These are the
  small grey nits that infected people may have.
• The fake lice on your skin are approximately the
  same as a real louse that can be spread from
  person to person and causes infections and severe
  itching.
• A bacterium is about 1/1000 the size of the louse
  and a large virus is about 1/10,000 the size of
  the louse.

4
Find sweat glands on the palms

• Where on the palm can you see sweat glands must
  easily?
• Their opening is seen along the ridges that form
  the fingerprints-
• Use higher power-to see small glistening drops of
  sweat.
• How regular is the distance between sweat glands
  on the skin ridges?
• Do you see openings in the depressed portions
  between the ridges?
• Try to see sweat glands on other parts of the
  body.
• What are the functions that the ridges might
  have-think about the ridged soles on some sports
  shoes?
• Sweat contains amino acids, the building blocks
  of proteins, and can be stained with special
  chemicals - this is used by crime scene
  intelligence agents.

5
Skin is essential for controlling the bodys
temperature

• Sweat glands, blood vessels and nerves for a
  system to control temperature.
• Sweat glands deliver a watery fluid (sweat)
  with small amounts of salt and amino acids to
  the skin surface.
• The heat brought to the skin by large and small
  blood vessel evaporates the sweat on the skin
  surface and lowers the body temperature.
• If sweat glands are lacking because of genetic
  diseases children get very hot and sick during a
  fever or exercise. Certain drugs can block
  sweating. Some drugs leave the body in the sweat.
• Botox, a drug to decrease skin wrinkling is
  sometimes used when people have excess sweating
  on their hands, feet, or armpits.

6
Body Temperature

• Sweats glands are over entire body except for
  special locations like the lips.
• Sweat is formed in a coiled portion of the gland
  in the fatty layer from the glands that are close
  to small blood vessels.
• Nerves near the blood vessels control blood flow
  and also release small chemicals that control
  sweating.

• Sweat glands lie deep in the skin in the fatty
  layer-the subcutaneous layer, each gland has a
  duct that carries the sweat across the dermis of
  the skin and the duct crosses the epidermis to
  exit on the skin surface.

Figure from http//www.nature.com/milestones/skin
bio/subjects/index.html
7
Sunlight-

• Sunlight and the skin have important
  relationships-
• The skin is the only part of the body that uses
  sunlight to make Vitamin D from a
  cholesterol-like chemical
• Too much sunlight, or suntan beds, causes redness
  and pain in the skin, scaling, darkening of the
  skin color, wrinkling, aging and skin cancer.
• The epidermis blocks the most dangerous shorter
  UV rays but longer UV enters the dermis (Layer
  II) and damaged the molecules collagen and
  elastin that form the bulk of the dermis and
  give skin its characteristic feel. These
  molecules require special electron microscopes to
  be seen.

8
Sunlight

• Look at the skin the with scope on the outside
  and inside portions of the upper arm.
• Which side is darker?
• What might the reasons be?
• Look at some freckles and see if someone has a
  mole.
• What do you see in the mole?
• Different structures such as globules and a
  netlike pattern are often seen.

9
Hair

• Hair follicles are over the entire skin except
  for special locations like the lips and the palms
  and soles.
• People used to think that hair on the palms was
  the skin of a werewolf.
• Look at the hair under high magnification and
  look for an overlapping patterns of cells on the
  outside cuticle layer of the hair.
• The hair is dead - what will happen if the hair
  is exposed to too damage or chemicals.
• Look at the very fine hairs that are on the face.
  Acne starts when these hair follicles get
  blocked.
• Hair follicles, if completely lost can not
  regrow, See if someone in your group has a scar
  and what that skin looks like.

10
Conclusion

• Skin is the largest organ and serves many
  functions
• You should now have a better understanding of how
  the skin protects us from bugs, the location and
  function of sweat glands, sun damage spots, and
  hair.