Besides protection, the skin contributes to:
Regulation of body temperature
" Sensory perceptions
" Synthesis of vitamin D
" Emotional expression
! It also serves as an important reservoir of blood.
The skin is composed of both a superficial epidermis and a deeper dermis. The epidermis is highly vascularized, while the dermis is avascular.
A) True B) False
The skin has 3 major layers:
-The outer, thinner layer is called the EPIDERMIS and consists of epithelial tissue.
-The inner, thicker layer is called the DERMIS and consists of C.T.
- The SUBCUTANEOUS (subQ) layer (also called the hypodermis) is located underneath the dermis. (" It is a loose areolar/adipose C.T. that attaches the skin to the underlying tissues and organs. )
About 90% of the cells of the epidermis are of which type?
a) melanocytes b) adipocytes c) keratinocytes d) Merkel cells e) Langerhans cells
The epidermis is composed of which type of tissue?
Keratinized stratified squamous epithelium
The epidermis is composed of keratinized stratified squamous epithelium which contains four major types of cells:
" Langerhans cells
" Merkel cells
These cells have an immune function in the epidermis.
make up 90% of the cells. They produce keratin - a tough fibrous protein that provides protection.
produce the pigment melanin that protects against damage by ultraviolet radiation.
are macrophages that originated in the red bone marrow. They are involved in the immune responses.
function in the sensation of touch along with the other adjacent tactile discs (receptors).
The pigment-producing cells of the epidermis are located in which layer?
Which layer is only present in thick skin?
Which epidermal layer marks the transition between metabolically active cells of lower layers and the dead layers of keratinocytes of the upper layers.
Produced from stem cells in the basale, this layer of cells has course bundles of keratin intermediate filaments, but more rounded in shape in living tissue?
Which layer consists on average of 20 to 30 layers of flattened dead keratinocytes.
Which layer of the epidermis contains Langerhans cells?
You would find this type of skin on all surfaces accept the palms of the hands and soles of the feet.
c) thick, hairy
d) thin, hairy
d. thin, hairy
types of skin
Thin (hairy) skin covers all body regions except the palms, palmar surfaces of digits, and soles.
" Thick (hairless) skin covers the palms, palmar surfaces of digits, and soles.
Which of the following is not a correct statement about melanin?
a) granules of melanin are produced and exported by melanocytes
b) melanin granules are the source of skin pigmentation
c) melanin is necessary for the production of vitamin D by the skin
d) melanin pigment protects DNA from damaging UV light e) melanin granules are taken up by keratinocytes
Melanin is produced by melanocytes in the stratum basale
Eumelanin (brown to black)
• Pheomelanin (yellow to red)
(“birthmarks” or moles) are chronic lesions of the skin – they are, by definition, benign.
a cancer of melanocytes
Which statement is not correct about the dermis?
a) it is made up of dense, irregular connective tissue
b) it is thinner in men than in women
c) it contains collagen and elastin fibers
d) it provides the blood supply and many sensory receptors for the epidermis
e) it has a smaller papillary layer, and a thicker reticular layer
The dermis is composed of connective tissue containing collagen and elastic fibers. ! It contains two regions:
The papillary region lies just below the epidermis and consists of areolar connective tissue containing thin collagen and elastic fibers, dermal papillae (including capillary loops), corpuscles of touch and free nerve endings.
Which of the following would be found in the papillary layer but not the reticular layer of the dermis?
a) capillary loops
b) adipose cells
c) lamellated corpuscles (pacinian corpuscles)
d) the root of hair follicles
e) sweat glands
The reticular region
The reticular region consists of dense irregular connective tissue containing collagen and elastic fibers, adipose cells, hair follicles, nerves, sebaceous (oil) glands, and sudoriferous (sweat) glands.
• Tears or excessive stretching in this region cause stretch marks (also called striae).
If you were to cut yourself deep enough to penetrate into the dermis, which orientation would you want the cut to be in, in relation to lines of cleavage, to minimize scaring?
a) perpendicular b) parallel c) tangental d) ipsolateral
lines of cleavage
Lines of cleavage are “tension lines” in the skin that indicate the predominant direction of underlying collagen fibers that resist pulling in that dir.
What types of sensory receptors would you find in the reticular region of the dermis?
B. pacinian corpuscles
sensory receptors found superficially
Merkel discs, free nerve endings (detect many stimuli), Meissner corpuscles, and hair root plexuses
sensory receptors found deep
The subcutaneous layer
! The subcutaneous layer is also called the hypodermis, and it attaches the skin to underlying tissues and organs.
" It contains blood vessels and nerves in transit to the more superficial layers.
" It also contains lamellated (pacinian) corpuscles that detect external pressure applied to the skin.
Hair is associated with the word “pili”.
" It is present on most surfaces except the palms, anterior surfaces of fingers, and the soles of the feet.
" It is composed of dead, keratinized epidermal cells.
" Genetics determines thickness and distribution. ! Hair helps with touch sensations and protects the body against the harmful effects of the sun and against heat loss.
Which of the following is NOT a function of hair in the human body?
a) Touch sensation
c) Thermal regulation
d) Protection from UV rays
e) All of the above are functions of hair
the parts of hair include:
The shaft (above the skin surface)
" The follicle (below the level of the skin)
" A root that penetrates into the dermis includes:
• An epithelial root sheath
• A dermal root sheath
This type of exocrine gland is a simple, branched acinar gland connected to a hair follicle.
a) Sebaceous gland
b) Sudoriferous gland
c) Both sebaceous gland and sudoriferous gland
d) None of these answers are correct
The hair root plexus functions to
a) support the growing hair.
b) cause the hair shaft to become erect.
c) stimulate sweat secretion.
d) give rise to the hair matrix.
e) assist hair in touch perception.
What is the correct order of stages in hair growth? a) regression, growth, resting
b) resting, growth, regression
c) growth, resting, regression
d) resting, regression, growth
e) growth, regression, resting
e. growth, regression, resting
This is fine nonpigmented hair that covers the body of the fetus.
fine, nonpigmented, downy hairs that cover the body of the fetus
short, fine, pale hairs barely visible to the naked eye
long, coarse, heavily pigmented hairs
Two types of sweat glands
*both are simple coiled tubular glands
Eccrine sweat gland
are the most numerous. They secrete a watery solution (600 ml per day) that helps to cool the body and eliminates small amounts of waste
release sweat in response to an emotional stress such as fear or embarrassment. This type of sweating is referred to as emotional sweating or a “cold sweat”.
apocrine sweat gland
are located mainly in the skin of the axilla, groin, areolae, and bearded facial regions of adult males. They secrete a slightly viscous sweat.
located mostly in the subcutaneous layer, and the excretory duct opens into hair follicles, with sweat secreted during emotional stress and sexual excitement. " Much of body odor is due to apocrine sweat.
Along with sweating, which other responses by skin assists with thermoregulation?
a) blood vessels near the skin can dilate, increasing blood flow and heat loss
b) additional secretion of sebum coats the skin and protects it against the sun
c) apocrine sweat glands add their sweat to eccrine glands to increase evaporative cooling
d) as a response to cold, blood vessels dilate to bring more warmth to the skin’s surface
e) all of these occur
These types of glands secrete an oily substance. a) ceruminous
Sebaceous (oil) glands
are connected to hair follicles.
" They secrete an oily substance called sebum which does 2 important things:
• Prevents dehydration of hair and skin
• Inhibits growth of certain bacteria
are modified sweat glands located in the ear canal.
" Along with nearby sebaceous glands, they are involved in producing a waxy secretion called cerumen (earwax) which provides a sticky barrier that prevents entry of foreign bodies into the ear canal.
This is a mixture of triglycerides, cholesterol, proteins and inorganic salts.
a) Sweat b) Lanugo c) Vellus d) Sebum e) Mucus
Which feature(s) of the skin protect(s) us against microbes such as bacteria?
a) the many layers of keratinized cells form a barrier against microbes
b) sebum contains compounds which kill bacteria
c) sweat has an acidic pH which suppresses microbial growth
d) Langerhans cells can alert the immune system should microbes invade
e) all of these are correct
The hyponychium is the __________ of the nail.
a) free edge
c) nail bed
d) nail body
e) nail root
Actual growth of the nail occurs in the __________ .
d) nail root
e) nail matrix
e. nail matrix
Wounds that only damage the epidermis won’t bleed because the epidermis is avascular.
a) True b) False
Two kinds of wound-healing processes can occur, depending on the depth of the injury.
Epidermal wound healing
deep wound healing
Epidermal wound healing
occurs following superficial wounds that affect only the epidermis.
• Return to normal function is the rule.
Deep wound healing
occurs when an injury extends to the dermis and subcutaneous layer.
• Loss of some function and development of scar tissue is the rule.
When an epidermal wound begins the healing process, basal cells migrate away from the basement membrane, enlarge, and migrate to fill in the wounded area) As these cells migrate from different sides of the wound, and reach each other, they stop migrating. This process is called__________.
A burn is tissue damage caused by excessive heat, electricity, radioactivity, or corrosive chemicals that denature (break down) the proteins in the skin cells.
" Burns destroy some of the skin's important contributions to homeostasis—protection against microbial invasion and desiccation, and thermoregulation.
first degree burn
involves only the epidermis
" It is characterized by mild pain and erythema (redness) but no blisters and skin functions remain intact.
Second degree burn
destroys the epidermis and part of the dermis - some skin functions are lost. " Redness, blister formation, edema, and pain result.
Third degree burn
is a full-thickness burn (destroys the epidermis, dermis, and subcutaneous layer). " Most skin functions are lost, and the region is numb because sensory nerve endings have been destroyed.
Which of the primary germ layers of the embryo does the epidermis of the skin develop from?
d) All of these choices are correct.
e) Both endoderm and ectoderm.
The epidermis develops from..
The epidermis develops from the ectoderm.
" Nails, hair, and skin glands are epidermal derivatives.
The dermis develops from the..
Integumentary system changes with age:
" Dehydration and cracking occurs.
" Sweat production increases.
" An increase in the numbers of functional melanocytes results in gray hair and atypical skin pigmentation.
" Subcutaneous fat is lost, and there is a general decrease in skin thickness.
" Nails may also become more brittle.
Bed sores, or pressure ulcers develop from a constant lack of blood flow. Which layer is the most affected by this?
a) Epidermis b) Dermis c) Hypodermis
Vitamin D, following activation in the skin, is converted to the hormone calcitriol by enzymes in the liver and kidneys. People in northern climates who may not get adequate sun exposure can become deficient in vitamin D. What mineral would be especially affected by this?