What is the largest organ
in the human body?
The brain
The liver
The skin
The Skin as a Receptor for Stimuli
Three basic layers of skin
Subcutaneous
Layers of the Skin
• Epidermis (2 parts):
1) dead layer (outermost)
• Cells we see on the surface of the skin
2) living layer (under the dead layer):
• cells are continually multiplying,
healing of wounds and contains melanin.
MELANIN
• Melanin is the cellular chemical produced by our
skin to help fight the sun’s UV Rays. We get
darker for protection – “sun tan”.
• Melanocytes are cells that produce Melanin.
• Melanoma is skin cancer! .
Lack of Melanin?
• Albinos don’t produce melanin and therefore
have white or pinkish skin (due to the presence
of blood)
• African people have a high concentration of
melanin in their skin; the dark pigment.
Layers of the skin
The Dermis contains:
– Nerve endings
– Blood vessels
• These supply the skin with
oxygen and nutrients
• Help regulate body temperature
– Roots of the hair
• At the base of the hair follicle are
muscle fibers known as erector
pili muscles
• These muscles cause the hair to
stand up when the body shivers
from cold
Dermis (continuation):
– Sebaceous glands (secrete sebum)
• an oily substance to make the skin and
hair waterproof and to protect them from
drying out
– Sweat glands
Subcutaneous layer contains:
– Fat cells (lipids)
• Energy storage
• Insulates the body against variations in
air temperature
Three basic layers of skin
Subcutaneous
The Subcutaneous Tissue is mostly fat.
Non-sensory functions of the skin
(ie. What does the skin do, other than
allow you to feel things?)
1. Protection from burns, infections, the sun,
insects, etc.
2. Excretion of sweat and nitrogenous wastes
3. Vitamin D production
•
Vitamin D is a fat-soluble vitamin that is used by the body in
the absorption of calcium.
•
Sun’s UV rays convert fatty deposits of subcutaneous layer
into Vit. D
•
It is recommended people get 10 to 15 minutes of sunshine
3 times a week
The main sensations perceived by the
receptors (nerve endings) in the skin
1. Tactile sensations
(touch/pressure)
2. Painful sensations
3. Thermal sensations (hot & cold)
The structures responsible for the
sensations perceived by the skin:
• Specialized nerve endings
– Also known as “DENDRITES”
• Most are covered by a protective oval
capsule = called corpuscles
Sensory Skin Sensors Video
•
Different sensations you feel are due to different
types of nerve endings (receptors)
(these are distributed unevenly over the entire surface of
the body)
1. Tactile sensations: received by touch & pressure
receptors
2. Thermal sensations: received by heat & cold
receptors
3. Painful sensations: received by pain receptors
How are sensations (touch, temperature, pain)
transmitted to the brain?
1. Receptors (tactile corpuscles) are excited
(electrical impulse) by a stimulus (temp, pain,
touch).
2. The nerve impulse then travels to the brain via
the sensory nerve in the spinal cord.
3. Only when the brain receives the nerve impulse,
is the sensation perceived.
The sense of touch involves:
• Receiver = the skin
– Receives sense of touch (light, soft, hot, cold, painful)
• Transformer = Nerve endings of the skin
– Transforms touch into a nerve impulse (action potential).
• Conductor = Sensory nerves of the spinal cord
– Conduct the nerve impulses.
• Analyzer = the brain (centre for sensory information)
– Analyses the incoming nerve impulses.
Levels of burns (fire, sun, etc.)
•• Damage
The depth
a burn
determines
itsinto
severity.
fromof
Third
degree
burns extend
the
hypodermis
(sub-cutaneous),
causing
destruction
of skin
the full
– First degree
burns damages
the outer
layer of
(epidermis)
and its
cause
pain,
redness
and swelling.
thickness
of skin with
nerve
supply
(numbness).
Third
degree burns leave scars and may cause loss of function
and/or sensation.
– Second degree burns damage the epidermis and the
inner layer, the dermis, causing swelling and blistering.
Skin
Diagram
to
Label
Dermis
Hair
Sebaceous
Gland
Blood Vessels
Fat
Erector Muscle
Epidermis
Follicle
Structures of the Skin Worksheet
Science and Technology 3
Structures of the Skin Worksheet
Part 1: Match the word with the appropriate definition
Dermis,
Melanocyte,
Blood vessels,
Erector pili muscle,
1. Tubes that carry blood as it circulates.
Subcutaneous tissue,
Sweat gland
Sensory Receptor
Sebaceous gland,
Epidermis,
Hair Shaft
2. The layer of the skin just beneath the epidermis.
3. The outer layer of the skin.
4. A tube-shaped sheath that surrounds the part of the hair that is under the skin. It is located in the epidermis and the dermis.
The hair is nourished by the follicle at its base (this is also where the hair grows).
5. A muscle is connected to each hair follicle and the skin - it contracts (in response to cold, fear, etc.), resulting in an erect hair
and a "goosebump."
6. A cell in the epidermis that produces melanin (a dark-colored pigment that protects the skin from sunlight).
7. Nerve receptors that respond to pressure and vibration; they are oval capsules of sensory nerve fibers located in the
subcutaneous fatty tissue
8. A small, sack-shaped gland that releases oily (fatty) liquids onto the hair follicle (the oil lubricated and softens the skin).
These glands are located in the dermis, usually next to hair follicles.
9. A tube-shaped gland that produces perspiration (sweat). The gland is located in the epidermis; it releases sweat onto the
skin.
10. Fatty tissue located under the dermis
Part B: Label the diagram with the structures from above