Skin Glands

Skin glands
Sebaceous Glands
           - also known as "Oil Glands"
Most are associated with hair follicles.
They secret either into the neck of a hair follicle, or directly onto the surface of the skin via a pore.
Location
-
Sebaceous glands are located over most of the surface of the skin/body but not in the palms of the hands or the soles of the feet.
Secretion(s):
-
Sebaceous glands secret an oily substance called sebum.
Importance
-
Sebum helps to protect skin and hair by:
preventing hairs from becoming too dry and brittle
preventing the skin from becoming too dry (by preventing excessive evaporation of water from the surface of the skin), hence also helping to keep the skin soft and effective
restricting the growth/development of certain bacteria.
 Sudoriferous Glands
-          also known as "Sweat Glands"
Different Types:
  • Apocrine Glands - ducts open in hair follicles
  • Eccrine Glands - ducts terminate at a sweat pore at the outer surface of the epidermis
Location
-
Apocrine Glands :-
Eccrine Glands :-
  • Armpits (skin of the axillae)
  • Pubic region
  • Pigmented areas of breasts (areolae)
  • Throughout the skin
    (except for margins of lips, eardrums, nailbeds of finger and toe nails)
Secretion(s):
-
Sudoriferous glands secret sweat, which is also called "perspiration". Apocrine glands secret a sticky viscous secretion while the secretion from eccrine glands is thinner; watery by comparison.
Importance:
-
The main functions of the secretion of sweat are to help regulate body temperature and to help eliminate from the body some of the waste products of metabolism (i.e. metabolic reactions).


Ceruminous Glands 
                        - the "Wax Glands" of the ear
Ducts open either directly onto the surface of the external auditory canal or into the ducts of sebaceous glands.
Location
-
The external auditory canal, also known (colloquially) as simply the "outer ear"
Secretion(s):
-
The prefix "cer-" means "wax".
The secretions from ceruminous glands combines with sebum secreted by nearby or associated sebaceous glands to form cerumen which is also known colloquially as "ear wax".
Importance
-
Cerumen, assisted by the hairs in the outer ear, protects the ear from particles originating outside of the body e.g. of dust, fine sand, or similar in the air getting into the ear itself. Cerumen provides a sticky barrier that prevents many such particles from going further into the ear.


Scent gland
Scent glands are exocrine glands found in most mammals. They produce semi-viscous secretions which contain pheromones and other semiochemical compounds. These odor-messengers indicate information such as status ,territorial marking, mood, and sexual power. The odor may be subliminal—not consciously detectable. Though it is not their primary function, the salivary glands may also function as scent glands in some animals.

How we determine the age of a rock?
RADIOMETRIC AGE-DATING
Radiometric dating or radioactive dating is a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay. The use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and can be used to date a wide range of natural and man-made materials.
Some elements have forms (called isotopes) with unstable atomic nuclei that have a tendency to change, or decay. For example, U-235 is an unstable isotope of uranium that has 92 protons and 143 neutrons in the nucl eus of each atom. Through a series of changes within the nucleus, it emits several particles, ending up with 82 protons and 125 neutrons. This is a stable condition, and there are no more changes in the atomic nucleus. A nucleus with that number of protons is called lead (chemical symbol Pb). The protons (82) and neutrons (125) total 207. This particular form (isotope) of lead is called Pb-207. U-235 is the parent isotope of Pb-207, which is the daughter isotope.
Many rocks contain small amounts of unstable isotopes and the daughter isotopes into which they decay. Where the amounts of parent and daughter isotopes can be accurately measured, the ratio can be used to determine how old the rock is.

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