Guess the topic of the next presentation…
* Its total surface is 1.80 m2
* It is the first line of defense from external factors.
* It’s water resistant
* *It keeps our extra kilos in secret, although it weighs 3 - 4 kilos
* We “gotta feeling” thanks to it
Some English idioms with it
be --------- and bone/bones : to be extremely thin
Beauty is only ----------- deep : a person's character is more
important than his/her appearance
by the ----------------- of one's teeth Fig. just barely.
give someone some -------------------- Sl. [for two people]
to touch two hands together in a special greeting, like a handshake.
(One hand may be slapped down on top of the other, or they may be
slapped together palm to palm with the arms held vertically.
There's more than one way to --------------- a cat. Prov.
You can always find more than one way to do something.
(nearly) jump out of one's ---------------- Fig. to react
strongly to shock or surprise.
• Epidermis Basal layer
•The deepest layer, one cell thick.
• made up of basal keratinocyte
cells (stem cells of the epidermis)
that produce keratin and
melanocytes that produce MELANIN
• Cells % by mitosis, move towards
surface, die and fill up with
*Hard and waterproof
*Made of dead cells
*Always worn away (every
28days) and replaced
Melanin UV rays
Fold Hair follicle
CONNECTIVE TISSUE + elastic fibres COLLAGEN/ ELASTIN
+sebaceous glands produce sebum keeps the skin and hair from
drying out and inhibits the growth of certain harmful bacteria
Layer of adipose tissue Food reserve/ insulation
Differences in skin color result from differences in
the amount of melanin produced and how
melanosomes, packets of melanin, are arranged
in the keratinocytes.
Particularly in people with light skin, melanin
sometimes accumulates in patches, forming
freckles, age spots, or liver spots.
A total lack of
melanin, a genetic
sensitive to the sun.
People with albinism
have very light skin,
hair, and eyes.
The color of hair is due to melanin. Dark
hair contains true melanin like that found in
Blond and red hair result from types
of melanin that contain sulfur and
Hair goes grey when melanocytes age and lose
the enzyme necessary to produce melanin.
Nails on the fingers and
toes are made of hard,
cells. They protect the
ends of the digits from
injury, help us grasp
small objects, and
enable us to scratch.
Functions of the skin
1.Protection: a)an anatomical barrier from pathogens and damage between
the internal and external environment
b)it reduces WATER LOSS
c)Melanin protects from UV rays
2.Sensation: contains a variety of nerve endings that jump to heat and cold,
touch, pressure, vibration, and tissue injury SENSITIVITY
3.Heat regulation: increase perfusion and heatloss, while constricted vessels
greatly reduce cutaneous blood flow and conserve heat.
4.Control of evaporation: the skin provides a relatively dry and semi-
impermeable barrier to fluid loss.
5.Storage :acts as a storage center for lipids and water
6.Water resistance: barrier so essential nutrients aren't washed out of the
body. The nutrients and oils that help hydrate our skin are covered by our
most outer skin layer, the epidermis. This is helped in part by the sebaceous
glands that release sebum, an oily liquid.
How long could the people have
remained alive in the water?
On the night of the Titanic sinking, the temperature of the
salt water was likely around 28° F(-2 °C). The human body
loses heat to the water about 30 times faster than it does to
the air. When the core body temperature falls to approximately (31°C), a
decrease in consciousness occurs. If the core temperature cools to below
86° F(30°C) then heart failure becomes a major concern, as it is the most
common cause of hypothermia-related deaths. The people in the -2 °C
water above the sinking Titanic would have had anywhere from several
minutes to an hour to live, depending on their physical condition and
how much they flailed. Some people in the water might have believed
that swimming would help their body to generate heat. In reality, people
who swam or moved around a lot would have lost heat 35-50% faster
and been susceptible to exhaustion. There were even several people who
died from hypothermia in the Titanic lifeboats, because they were open
and gave no protection against the cold. Regulations have since been put
in place that require lifeboats to be fully or partially enclosed.
* Normal human body temperature varies between -------------- and ---------
* CORE TEMPERATURE
* Heat is lost by * Heat is gained by
The term ‘homeostasis’ is derived from two Greek words; Homeo which
means ‘unchanging’ and Stasis which means ‘standing’
In its simplest form it means ‘staying the same’
It is an organism’s internal environment which ‘stays the same’
The ‘internal environment’ refers to the conditions inside an organism. These
conditions remain more or less constant despite changes such as pH or temperature
in the outside environment
So, a better definition of ‘homeostasis’ is t ---- m----------------------- o- t----
i ----------------------------- e---------------------- w-------------------- n-------------------
Homeostasis and negative feedback
How do they regulate
* They are -------------------
* They regulate their temperature by----
If their body temperature falls-------------
*We are -------------------
*The “price” we pay is ----------
*The ----------------------------- is the thermoregulatory centre.
It has TWO functions: a)
Why is the process of controlling the temperature
is an example of NEGATIVE FEEDBACK????
The skin, kidneys, liver,
endocrine system, nervous
system and sensory system all
play a part in maintaining the
internal environment within
2)To carry out its living processes, every cell in the body needs a supply of
oxygen and food. Waste products such as carbon dioxide have to be removed
before they reach harmful levels and damage the cell
These conditions are maintained by tissue fluid bathing the cells. Tissue fluid is
derived from the blood
1) The skin is a homeostatic organ which helps maintain the body temperature
within the limits given in the previous slide
3) In the cells, the chemical breakdown of proteins produces the
nitrogenous compound, urea. If this were allowed to accumulate in the cells
it would damage or kill them. The concentration of the blood and tissue
fluids tends to vary. If water is lost through evaporation and sweating, the
fluids become more concentrated. The intake of water dilutes the fluids
These homeostatic functions are carried out by the kidneys
4)The LUNGS keep the concentration of Oxygen and Carbon dioxide in the blood
for the cell’s reactions (respiration)
5) The glucose concentration in the blood is controlled by the pancreas
The pancreas contains cells which produce digestive enzymes but it also contains cells
(alpha and beta cells) which produce the hormones insulin and glucagon
If the glucose concentration rises, the beta cells release insulin
If the glucose concentration falls, the alpha cells release glucagon
In this way, the concentration of glucose in the blood is kept within narrow
Insulin stimulates and to remove excess glucose from
the blood and store it as glycogen
Glucagon stimulates to convert its stored glycogen into glucose
which is then released into the bloodstream
The blood system maintains the composition of the tissue fluid
carbon dioxideglucose oxygen carbon dioxidetissue fluid
fluid filtered out of
blood flowBlood and tissue fluid