dermis and hypodermis Flashcards
integumentary system
Dermis
The middle layer of skin, contains collagen, blood vessels, glands, hair follicles, and nerve endings support and protect the skin and deeper layers, assist in thermoregulation, and aid in sensation.
Hypodermis (subcutaneous)
The innermost layer of skin, storing energy, connecting the dermis layer of your skin to your muscles and bones, insulating your body, and protecting your body from harm.
Dermal papillae
Protrusions of dermal connective tissue into the epidermal layer.
Melanocytes
produce and distribute melanin, which is a skin pigment.
Sebaceous glands
Microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum
Sudiferous (sweat glands)
Found in the dermis, sweat duct that transports the secretion to the surface of the epidermis (eccrine glands) or into a hair follicle (apocrine glands).
Eccrine
Sweat glands that are the most numerous and widely distributed over the body.
The dermis
the middle layer of the integument. The dermis consists of loose connective tissue and houses a number of accessory structures of the skin.
The dermis connects to
the epidermis by dermal papillae
The dermis contains a variety of accessory structures of the integument. These include: 6
Hair follicles
Arrector pili muscles
Sweat glands
Sebaceous glands
Sensory receptors
Blood vessels
Hair is not alive and develops from old dead cells pushed outward by new cells. The cells contain
keratin for hardness and melanin for color.
Hairs can be very sensitive. This is due to
a tiny plexus of nerves that surround each hair follicle
A band of smooth muscle connects to each hair follicle
- arrector pili muscle
- is capable of moving each follicle causing it to stand up in times of sympathetic nervous system activity such as emotional stress.
the hair bulb
Hair begins to grow at the base of the hair follicle in a structure
There are 2 types of hair.
- Vellus hairs are the fine hairs located on much of your body’s surface.
- Terminal hairs are thicker, more pigmented and are found on your head as well as genitals and axillary region.
A small sebaceous gland surrounds each hair follicle. The sebaceous glands secrete an oily substance known as
sebum
Sebum is secreted in response to
contraction of the arrector pili muscle.
Sebum contains
triglyceride, protein, cholesterol and some electrolytes
Sebum makes
the hair more flexible and hydrated.
Sweat glands (aka sudoriferous glands) are located
the dermis
There are 2 types of sweat glands
apocrine
eccrine
Apocrine sweat glands secrete their substances into
the hair follicles
The secretions of apocrine glands can develop
odor. The odor can increase because the secretion acts as a nutrient for bacteria that enhance the odor. Apocrine glands begin to secrete substances at puberty and are located in the axilla and genital regions.
Eccrine sweat glands secrete their substances
directly onto the surface of the skin. They are coiled tubular glands that secrete a substance that mostly consists of water with a trace of some electrolytes and a peptide with antibiotic properties.
The eccrine sweat glands primary function is to
help to regulate body temperature. The sweat can evaporate and carry away heat. The sweat also excretes water and electrolytes.
The nail body is the
visible portion of the nail sits over the nail bed.
The nail begins deep in the skin proximal to
where it is seen at the nail matrix. The nail begins to grow at the nail root which is close to the bone.
A portion of the superficial epidermis (stratum corneum) extends over the proximal portion of the nail forming
the eponychium or cuticle. Blood vessels deep to the nail give it a pink color.
The skin is very important in
regulating body temperature. The skin helps keep in heat produced by skeletal muscles and liver cells. When the body gets too hot the skin opens up the sweat pores so that the sweat can carry the heat away by evaporation
Heat can be lost by the body in a number of ways. Heat always moves along a gradient from
warmer to cooler temperatures. Heat can radiate from the body to the surrounding areas at lower temperatures.
In conduction, heat moves via molecules from the warmer body to cooler objects. An example of conduction
would be to lean against a cooler concrete wall. The heat flows from your body into the wall.
In convection, heat moves via
air molecules circulating around body.
In evaporation fluid on the surface of the body
carries heat away
Body temperature is primarily regulated by an area in the brain known as
the hypothalamus. The hypothalamus sets the body’s temperature and controls it by opening and closing sweat glands and contracting muscles.
Now let’s say that you’ve finished mowing the lawn and you go inside of your air conditioned home. Your body’s temperature will begin to drop. The hypothalamus
senses this and sends a message to your sweat glands to close. If your body’s temperature continues to drop the hypothalamus may send a message to your muscles to contract or shiver. The muscles will generate heat to help maintain your core temperature. In more severe cases of cold your blood vessels will constrict in your extremities in an attempt to conserve heat at the core of your body for survival.
If your core body temperature continues to drop you may develop a condition called
hypothermia. You will progress from feeling cold to shivering, experiencing mental confusion, lethary, loss of reflexes and eventually loss of consciousness and shutting down of organs.
after hypothermia if your core body temperature increases too much, you can develop
hyperthermia. This can develop in humid conditions because of lack of evaporation. The signs of hyperthermia include light headedness, dizziness, headaches, muscle cramps, fatigue and nausea.
