How many tissue layers make up the skin?

2 Layers

epithelial tissue overlying connective tissue

Name the OUTER layer of the skin.

Epidermis

Name the DEEPER layer of the skin.

Dermis

What are the 5 layers of the Epidermis?

1. stratum corneum
2. stratum lucidum
3. stratum granulosum
4. stratum spinosum
5. stratum basale

What are the 2 layers of the Dermis?

1. Papillary layer
2. Reticular layer

Describe the composition of the Epidermis.

• outer layer of the skin
• composed of epithelial cells
• outermost protective shield of the body
• avascular
• gets nutrients through the diffusion of tissue fluid from blood vessels in the dermis
• stratified squamous epithelium

Describe the composition of the Dermis.

• inner layer of skin
• makes up the bulk of the skin
• tough thick layer, composed of mostly dense connective tissue
• contains collagenous and elastic fibers
• only the dermis is vascularized

Which layer of the skin is better nourished?

The dermis is connective tissue, which is vascular, so its cells are better nourished than those of the epidermis, which is avascular epithelium.

Name the subcutaneous tissue that lies just deep to the skin.

Hypodermis or superficial fascia

What is the structure and functions of the Hypodermis?

The Hypodermis is not a part of the skin, but it shares some of the skin's protective functions.

• consists of mostly adipose tissue
• contains some areolar connective tissue
• acts as a shock absorber
• acts as an insulator that reduces heat
• contains blood vessels that supply skin

Which part of the skin acts as an insulating layer?

Hypodermis

Where is the thick skin of the body located?

1. The Palms
2. The Fingertips
3. The Soles of Feet

True or False:

In the thin skin, which covers the rest of the body, the stratum lucidum is absent and the other layers are much thinner?

true

True or False:

The stratum lucidum is only found in the thick skin?

true

Describe the Stratum Lucidum layer.

• Clear-thin translucent layer just above the stratum granulosum
• consists of a few rows of flat, dead keratinocytes
• through electron microscope, its cells are identical to those at the bottom of the next layer- stratum cormeum

Describe the Stratum Corneum layer.

• horny layer
• outermost epidermal layer- 20-30 cells layers thick
• keratin and proteins accumulated inside the plasma membrane and function to protect the skin against abrasion and penetration
• nearly waterproof because of the glycolipid between its cells
• cells shed regularly- dandruff from scalp and flakes of dry skin

Describe the Stratum Granulosum layer.

• thin layer
• consists of 1-5 layers
• keratinocytes appearance change drastically; process of keratinization begins

What is the function of granules in the Stratum Granulosum?

The cells of the Stratum Granulosum accumulate dense basophilic keratohyalin granules. These granules contain glycolipids, which along with desmosomal connections, help to form a waterproof barrier that functions to prevent fluid loss from the body.

Name the 2 types of granules found in the Stratum Granulosum.

• The keratohyalin granules help to form keratin in the upper layers.
• The lamellar granules contain a water-resistant glycolipid that is secreted into the extracellular space. Tight junctions & the glycolipid play a major part in slowing water loss across the epidermis.

What is the Stratum Spinosum layer composed of?

The Stratum Spinosum (or spinous layer/prickle cell layer) is
a layer of the epidermis found between the Stratum
Granulosum and stratum Basale. This layer is composed
of polyhedral keratinocytes. These are joined together with
desmosomes. Scattered among the keratinocytes are
dendritic cells, which are most abundant in this epidermal
layer.

How did the Stratum Spinosum layer get its name?

The Stratum Spinosum is several cell layers thick.
This layer gets its name from the many spine-like
extensions of its keratinocytes as seen under a
microscope.

Describe the Stratum Basale layer of the epidermis.

• The Stratum Basale, the deepest epidermal layer (Stratum Germinativum)
• The many mitotic nuclei seen in this layer reflect the
  rapid division of these cells.
• A single row of cuboidal or columnar cells that divide
  and grow; this layer also includes melanocytes

What is the difference between the Stratum Basale and the Stratum Corneum layers?

The cells in the Stratum Basale divide and grow, whereas the cells in the Stratum Corneum are dead and keratinized.

An individual using a sharp knife notices a small amount of blood where he just cut himself. Which layer of skin did he have to cut into in order to bleed?

Papillary Dermis layer

Which tissue types are located in the subcutaneous layer
beneath the skin?

The subcutaneous layer contains areolar connective tissue and adipose tissue.

Name the tissues in the outer and inner layers of
the skin?

• The epidermis is composed of stratified squamous epithelium.
• The dermis has connective tissue, smooth muscle tissue, and nervous tissue.

What are the functions of the subcutaneous layer?

The subcutaneous layer conserves heat and has major blood vessels that supply the skin.

What cells populate in the epidermis?

• keratinocytes
• melanocytes,
• dendritic cells
• tactile epithelial cells

What is the role of keratinocytes in the integumentary system?

The chief role of keratinocytes ("keratin cells") is
to produce keratin, the fibrous protein that helps
give the epidermis its protective properties.

What is the function of Merkel (tactile) cells?

Spiky-hemisphere shaped Merkel cell associated with a disc-like sensory nerve ending. The combination, called a Merkel or tactile disc, functions as a sensory receptor for touch.

Name the function and location of Melanocytes in the body.

Melanocytes produce the pigment melanin and is found in deepest layer (Stratum Basale) of the epidermis.

What are Langerhans cells?

Star-shaped dendritic cells arise from bone marrow and
migrate to the epidermis. Also called Langerhans cells, they ingest
foreign substances and are key activators of our immune system.

In humans, exposure of the skin to sunlight is required for ________.

Vitamin D synthesis

If you cut yourself and bacteria enter the wound, which cells would help get rid of the bacteria?

Langerhans cells

True or False:

Squamous cell carcinoma of the skin is a common form of skin cancer?

True

True or False:

Basal cell carcinoma is the most common type of skin cancer?

True

What factors that determine skin color?

1. Hereditary Factors
2. Environmental Factors
3. Physiological Factors

What are the functions of epidermis?

Protects against water loss, harmful chemicals, mechanical injury, pathogens

What are the functions of melanin?

This is skin pigment which provides skin color and protects
against the damaging effects of ultraviolet radiation (D N A
damage, fibroblast damage, skin cancer).

Describe the keratinization.

Keratinization is the process of hardening, dehydration, and keratin accumulation that occurs in epidermal cells as they
migrate outward.

What does the Papillary layer of the Dermis consists of?

• Superficial layer
• Areolar connective tissue
• Thinner of the 2 layers
• Location of dermal papillae

What does the Reticular layer of the Dermis consists of?

• Deeper layer
• Dense irregular connective tissue
• Thicker of 2 layers

What are the impressions made by the dermal Papillae ridges on the ends of the fingers and thumbs known as?

Fingerprints

What types of tissues make up the dermis?

The papillary layer is areolar connective tissue, and the reticular layer is dense irregular connective tissue.
Blood vessels, smooth muscle tissue, and nervous tissue are found in the dermis.

What are the functions of connective tissues in the skin?

The connective tissues give the dermis toughness and elasticity.

What are the functions of nervous tissues in the skin?

Nervous tissue includes sensory receptors and send signals to the brain and organs.

What are the functions of smooth muscle tissues in the skin?

The smooth muscle tissue can cause wrinkles the skin.

Why do humans have blood vessels in the skin?

Blood vessels in the dermis supply nutrients to the skin cells.

Name the sensory receptors in the skin.

Cutaneous mechanoreceptors

• Ruffini's end organ (skin stretch)
• End-bulbs of Krause (Cold)
• (Tactile) Meissner’s corpuscle responds to light
  touch and low-frequency vibration.
• (Lamellar) Pacinian Corpuscle responds to deep
  pressure and high-frequency vibration
• Merkel's disc (sustained touch and pressure)
• Free nerve endings- sense painful stimuli (irritating chemicals, extreme heat or cold, and others).

Thermoreceptors

Nociceptors

Chemoreceptors

What is the structure and function of Nails?

Nails are the protective coverings on ends of fingers and toes.
• In contrast to soft keratin of the epidermis, nails (like
hairs) contain hard keratin
• 3 parts of a nail:
• Nail plate: overlies nail bed.
• Nail bed: surface of skin, under nail plate.
• Lunula: most active growing region; pale, half-moon-
shaped region at base of nail plate.

Why is the lunule of a nail white instead of pink like the rest of the nail?

The lunula looks white because the epidermis is thicker beneath the matrix, and it blocks the pink color from the blood vessels below.

Why are nails so hard?

Nails are hard because (like hair) they contain hard keratin.

Where can hair be found on the body?

Hair is present on all surfaces of skin except palms, soles, lips, nipples, parts of external reproductive organs.

What is a hair follicle?

Tube-like depression of epidermal cells from which hair develops; extends into dermis or the subcutaneous layer.

Name the 3 parts of hair.

• Hair bulb (dividing cells)
• Hair root
• Hair shaft (dead, epidermal cells)

True or False:

The hair papillae does not contain blood vessels.

False

Hair papilla does contain blood vessels to nourish hair

What is the function of the Arrector pili muscle?

Arrector Pili Muscle is a small band of smooth muscle that connects the hair follicle to the connective tissue of the basement membrane.

Responsible for generating heat when the body is cold, the arrector pili muscles contract all at once, causing the hair to "stand up straight" on the skin. (goosebumps).

Where are Sebaceous glands found on the body?

Found all over the body except in the thick skin of the palms and soles. They are small on the body trunk and limbs, but quite large on the face, neck, and upper chest. These glands secrete an oily substance called sebum.

What are the functions of sebum?

Sebum softens and lubricates the hair and skin, prevents hair from becoming brittle, and slows water loss from the skin. Sebum keeps hair soft, pliable, and waterproof.

True or False:

Acne is caused by a lack of sebum?

False

Acne is caused by an excess of sebum which clogs the sebaceous gland.

Name the function and location of Merocrine (Eccrine) sweat glands.

• Lower body temperature through sweating
• Originate in the deep dermis or subcutaneous layer and abundant on the palms, soles of the feet, neck, and forehead.

Name the function and location of Apocrine sweat glands.

The secretion is odorless, but when bacteria on the skin decompose its organic molecules, it takes on a musky and generally unpleasant odor, the basis of body odor.

• Wet skin during pain, fear, emotional upset, and sexual arousal
• Near hair follicles in armpit and groin

Two important types of modified apocrine glands are:

Ceruminous glands: secrete ear wax - located external acoustic meatus

Mammary glands: s ecrete milk - located in the b reasts

What are the functions of the Skin?

Functions of the skin:

• Protective covering, barrier against harmful substances and microorganisms
• Prevents some water loss
• Contains sensory receptors
• Excretes some wastes
• Helps produce Vitamin D
• Helps regulate body temperature

What are the methods of heat loss?

Methods of heat loss:

• Radiation: Primary method, infrared heat rays escape.
• Conduction: Heat moves from the skin to cooler objects.
• Convection: Heat loss into circulating air currents.
• Evaporation: Sweat changes into a gas, carries heat away.

Which organ in the body monitors body temperature?

Setpoint of body temperature is monitored by the Hypothalamus.

What happens when body temperature rises?

When body temperature rises:

• Thermoreceptors signal the hypothalamus.
• Vasodilation of dermal blood vessels.
• Sweat glands are activated.

What happens when body temperature falls?

When body temperature falls:

• Thermoreceptors signal the hypothalamus.
• Vasoconstriction of dermal blood vessels.
• Sweat glands are inactive.
• Muscles contract involuntarily (shivering).

What is the setpoint of deep body temperature?

37 degrees Celsius or 98.6 degrees Fahrenheit

What is Hyperthermia?

Hyperthermia : abnormally high body temperature

• Can occur on hot, humid day, when sweat cannot evaporate.
• When air temperature is high, radiation is less effective.
• Body may gain heat from hotter air.
• Skin becomes dry, person gets weak, dizzy, nauseous, with headache, rapid pulse.

What is Hypothermia?

Hypothermia: abnormally low body temperature

• Can result from prolonged exposure to cold, or illness.
• Shivering is involuntary skeletal muscle contraction, caused by hypothalamus.
• Progresses to confusion, lethargy, loss of reflexes and consciousness.
• Without treatment, organs shut down.

What is the process of inflammation and is it normal?

• Inflammation is a normal response to injury or stress
• Inflammation is the body’s attempt to restrict spread of infection
• Blood vessels in affected tissues dilate and become more permeable, allowing fluids to leak into the damaged tissues

List the characteristics of inflammation.

Inflamed skin may become:

• Reddened
• Swollen
• Warm
• Painful

Explain the formation of a blood clot.

A deep cut, reaching the dermis or subcutaneous layer, results in blood

vessels breaking; released blood forms a clot.

What is the first phase of wound healing?

The first phase of wound healing is Inflammatory Phase

Initial response to injury
• Day 1-4 post injury
• Characterized by heat, pain, redness, swelling
• Platelet aggregation and activation
• Leukocyte (PMNs, macrophages) migration, phagocytosis and mediator release
• Venule dilation
• Lymphatic blockade
• Exudative

What is the third phase of wound healing?

The third phase of wound healing is Remodeling Phase

6wks-1 year

• Type III collagen replaced with type I
• Characterized by increase in tensile strength
• Scar flattens

Which phase or wound healing begins about 4 days after injury and overlaps with the inflammatory phase and involves cells called fibroblasts that help to produce new collagen, create new blood vessels, and repair the avascular epithelial tissue (epithelization)?

The second phase of wound healing is Proliferative Phase

Day 4-42

• Fibroblast proliferation stimulated by macrophage-released growth factors
• Increased rate of collagen synthesis by fibroblasts

How are burns classified?

Burns are classified by the extent of tissue damage

Which burn destroys epidermis and some dermis, as in burn from hot liquid?

Deep, partial-thickness ( second degree ) burn

True or False:

Full-thickness burns healing takes days-weeks, with no scarring?

False

Which type of burns are sunburns?

Superficial, partial-thickness (first degree) burn

Describe third degree burns.

• Destroys epidermis, dermis, accessory structures.
• Results from prolonged exposure to heat, flames, hot liquids.
• Some healing from margins.
• Often requires skin graft, skin substitutes.

The treatment of burn patients that involves estimating the extent of the injured body surface which divides body surface into regions of 9% or multiples of 9 is called_______________.

The Rule of Nines

Why is the "Rule of Nines" important?

The rule of nines assesses the percentage of burns and is used to help guide treatment decisions including fluid resuscitation, and becomes part of the guidelines to determine transfer to a burn unit.

Name 5 normal life-span changes in the body.

• Cell cycle slows, skin becomes scaly, age spots appear.
• Epidermis and dermis become thinner.
• Loss of fat in subcutaneous layer; person feels cold.
• Wrinkling, sagging of skin occur.
• Sebaceous glands secrete less oil; skin becomes dry.
• Melanin production slows; hair whitens.
• Hair thins.
• Number of hair follicles decreases.
• Nail growth becomes impaired.
• Sensory receptors decline.
• Body temperature regulation becomes less effective.
• Diminished ability to produce Vitamin D.