Anatomy and Physiology (Tortora) Chapter 5

Elements of integumentary system

Skin, hair, oil and sweat glands, nails, sensory receptors

What skin is also known as

Cutaneous membrane

Layer of skin that is composed of epithelial tissue

Epidermis

Functions of the integumentary system

1- Regulates body temp

2- Stores blood

3- Protects body from external environment

4- Detects cutaneous sensations

5- Excretes and absorbs substances

6- Synthesizes vitamin D

2 layers of skin

Epidermis and dermis

What portion of skin is made of connective tissue?

Dermis

What are the 2 regions of the dermis?

Papillary and reticular

Which layer of the dermis is more superficial?

Papillary

Which layer of the dermis is deeper?

Reticular

Why do some cuts not bleed?

Only the epidermis is damaged, and this layer is avascular, so there is no damage to blood vessels

Subcutaneous layer (AKA subQ or hypodermis)

What is deep to the dermis, but not actually part of the skin (or the integumentary system)?

Fibers that extend from the dermis anchor the skin to the subcutaneous layer, which in turn attaches it to the underlying fascia

What anchors the dermis to the hypodermis?

Define fascia

The connective tissue around muscles and bones

1- Serves as storage depot for fat

2- Contains large blood vessels that supply the skin

3- Contains nerve endings called lamellated corpuscles that are sensitive to pressure

What does the subcutaneous layer do?

Nerve endings in the hypodermis (sometimes the dermis) that are sensitive to pressure

What are lamellated corpuscles?

Keratinized stratified squamous epithelium

What type of tissue is the epidermis composed of?

Keratinocyte, melanocyte, Langerhans cells (intraepidermal macrophage), Merkel cells (tactile epithelial)

4 types of cells in epidermis

About 90% of epidermal cells are

Keratinocytes

dermatology

Medical specialty that deals with the structure, function, and disorders of the integumentary system

Skin

What is the largest organ in the body (by weight)?

Epidermis

Superficial, thinner portion of skin

About 8% of epidermal cells are

Melanocytes

About 2% of epidermal cells are

Merkel cells and Langerhans cells

keratinocytes

4-5 layers, produce keratin (tough, fibrous protein that helps protect skin and underlying tissue from abrasions, heat, microbes, and chemicals), produce lamellar granules, which release a water-repellent sealant that decreases water energy and loss and inhibits the entry of foreign materials

Keratinocytes

What protects skin from microbes?

What protects the skin from abrasion?

Keratinocytes

What protects the skin from heat?

Keratinocytes

What protects the skin from chemicals?

Keratinocytes

What inhibits evaporation?

Lipids

Sebum

What inhibits dryness of skin and hair and kills some bacteria?

Sweat

What retards growth of some bacteria on skin?

Is sweat acidic or basic?

Acidic

What do the pigments that melanocytes produce protect skin from?

UV damage

What skin cells alert the immune system?

Langerhans cells

What specifically releases a water-repellent sealant that decreases water entry and loss, and also inhibits the entry of foreign materials?

Lamellar granules (produced by keratinocytes)

What cells produce melanin?

Melanocytes

Where are melanocytes developed from?

Ectoderm of a developing embryo

How do melanocytes work?

Their long, slender projections extend between the keratinocytes and transfer melanin granules to them

What is melanin?

Yellow-red or brown-black pigment that contributes to skin color and absorbs damaging UV light

How does melanin work?

The granules form a protective veil over the nucleus, on the side toward the skin surface, shielding the DNA from UV light

Where do Langerhans cells come from?

Red bone marrow

What do Langerhans cells?

Participate in immune response to help other cells of the immune system recognize an invading microbe and destroy it

What do Merkel cells do?

Connect to the flattened process of a sensory neuron (known as a tactile disc). They detect touch sensations

Where are Merkel cells located?

In the deepest layer of the epidermis

What epidermal cells are the fewest in number?

Merkel cells

List the layers of thin skin from deepest to most superficial

Stratum basale, stratum spinosum, stratum granulosum, stratum corneum

List the layers of thick skin from the deepest to the most superficial

Stratum basale, stratum spinosum, stratum granulosum, stratum lucidium, stratum corneum

What are the mnemonic devices for the layers of thick and thin skin?

Bad Skin Gets Care, Bad Skin Gets Less Care

Deepest layer of epidermis

Stratum basale

What is the stratum basale composed of?

A single row of cuboidal or columnar keratinocytes. Some are stem cells that divide continually

What do the keratinocytes in the stratum basale contain?

Large nuclei, many ribosomes, a small Golgi complex, a RER, and a few mitochondria

What type of junctions are in the keratinocytes in the stratum basale?

Desmosomes, which attach the keratin intermediate filaments to adjacent keratinocytes and to the cells of the adjacent stratum spinosa. Hemidesmosomes attach the keratinocytes to the basement membrane that is between the stratum basale and the dermis

What cells besides keratinocytes are within the stratum basale?

Melanocytes and tactile epithelial cells (Merkel) with their associated tactile discs

Does the stratum basale divide to form new cells?

YES!!!

When the stratum basale is damaged, what can be done to fix the overlying tissue?

Skin graft. The skin won't heal itself at this point because the stratum basale is where the regeneration of cells would take place. If that's damaged, there is no way for new cells to be formed (no way for skin to heal)

Where is the stratum spinosum located?

Deep to the stratum granulosum, superficial to the stratum basale

How many layers are in the stratum spinosum?

8-10

What type of cells are mainly in the stratum spinosum?

Keratinocytes

Describe the keratinocytes in the stratum spinosum?

They have the same organelles as the cells in the stratum basale. The cells in the more superficial layers are more flattened. Some cells retain their ability to divide. They appear to have thorns when prepared, hence their name

What kind of filaments do the keratinocytes in the stratum spinosum secrete?

Coarser bundles of keratin in intermediate filaments than those of the basal layer.

What cell junctions exist within the stratum spinosum?

Desmosomes. These are what stick together to form the spiny look when this layer is viewed in a microscope

What is unique about the spine-like projections in the stratum spinosum and what qualities does it lend the layer?

Bundles of keratin intermediate filaments insert into the desmosomes, which tightly join the cells to one another, which provides both strength and flexibility to the skin.

What cells are within the stratum spinosum?

Keratinocytes, intraepidermal macrophages (Langerhans cells), and projections of melanocytes

Where is the stratum granulosum located?

Superficial to the stratum spinosum, deep to the stratum lucidum or stratum corneum

How many layers are in the stratum graulosum?

3-5

What kinds of cells are in the stratum granulosum?

Flattened keratinocytes undergoing apoptosis

Define apoptosis

Genetically programmed cell death in which the nucleus fragments before the cells die

Are there organelles in the cells in the stratum granulosum?

The organelles are dying off.

Are there more keratin intermediate fibers in the cells of the stratum granulosum?

There are the same amount of keratin intermediate filaments as in the stratum spinosum, but the filaments are more prevalent because of the death of the organelles

Define keratohyalin

The protein in the darkly staining granules of the stratum granulosum

In which layer are the lamellar granules located?

Stratum granulosum

What are lamellar granules and what do they do?

Membrane enclosed granules that fuse with the plasma membranes and release a lipid rich secretion. These secretions are deposited between the cells of the stratum granulosum, stratum lucidum, and stratum corneum. They originate from the cells of the stratum granulosum

What stratum marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial layers?

Stratum granulosum

Where is the stratum lucidum located?

Only in thick skin. Deep to the stratum corneum and superficial to the stratum granulosum

Describe the stratum granulosum

4-6 layers of flattened, clear, dead keratinocytes that contain large amounts of keratin and thickened plasma membranes

Where is the stratum corneum located?

Superficial to the stratum lucidum (thick skin), or the stratum granulosum (thin skin)

What is considered thick skin?

Palms of hands, soles of feet, fingertips

What is considered thin skin?

Everything but the fingertips, palms of hands, and soles of feet

How many layers in the stratum corneum?

25-30 layers, but it can range from a few cells to 50 or more layers

Describe the cells in the stratum corneum

The cells are extremely flat, plasma membrane-enclosed packages of keratin that no longer contain a nucleus or organelles. Final product of the differentiation process of the keratinocytes

How do the cells in the stratum corneum overlap?

The layers are like scales on a snake and the neighboring cells fit like pieces of a jigsaw puzzle

What ultimately happens to the cells of the stratum corneum?

They are shed and replaced by the cells from deeper layers

What is a callus?

An abnormal thickening of the stratum corneum because of constant exposure to friction which increases cell production and keratin production

When do the cells in the stratum basale increase their rate of division?

When the outer layers of the epidermis are stripped away, such as occurs in abrasions and burns

Define keratinization

The process by which cells accumulate more and more keratin

How does the epidermis grow?

Cells in the stratum basale divide and push upwards. Cells go through apoptosis, gain keratin, and eventually slough off.

Define dandruff

An excessive amount of keratinized cells shed from the skin of the scalp

Define psoriasis

Keratinocytes divide and move more quickly than normal from the stratum basale to the stratum corneum

Where is the dermis located?

Deep to the epidermis

What is the dermis composed of?

Dense irregular connective tissue containing collagen and elastic fibers

What qualities does the dermis have?

It has great tensile strength (resists pulling or stretching forces), and has the ability to stretch and recoil easily

What is thicker, the epidermis or the dermis?

Dermis

What cells are within the dermis?

Fibroblasts, some macrophages, a few adipocytes near its boundary of the subcutaneous layer.

What layer of skin are blood vessels embedded in?

Dermis

What layer of skin are nerves embedded in?

Dermis

What layer are glands embedded in?

Dermis

What layer are hair follicles embedded in?

Dermis

Where is the papillary region located?

The papillary layer is the superior layer of the dermis

What increases the surface area of the papillary region?

Dermal papillae

Define dermal papillae

Small, nipple-shaped structures that project into the undersurface of the dermis. Contain capillary loops. Some contain tactile receptors called corpuscles of touch or free nerve endings. Increased surface contact increases the network of small blood vessels, thus increasing the available nutrients for the overlying epidermis.