Chapter 5

Epidermis

is made of Avascular stratified squamous epithelium Is where the nutrients and oxygen diffuse from capillaries in the dermis

Where are the capillaries and sensory neurons that supply the epidermis located?

The capillaries and sensory neurons that supply the epidermis are located in the papillary layer of the dermis.

What happens to the cells of Stratum Granulosum?

The cells produce protein fibers, dehydrate and die, and create tightly interlocked layer of keratohyalin

What term describes the combination of fibrin clots, fibroblasts, and the extensive network of capillaries in healing tissue?

The combinations of fibrin clots, fibroblasts, and the extensive network of capillaries In tissue that is healing is called granulation tissue.

What happens when the arrector pili muscle contracts?

The contraction of the arrector pili muscle pulls the hair follicle erect, depressing the area at the base of the hair and making the surrounding skin appear higher. The result is known as a "goose bump"

Describe the location of the dremis

The dermis lies between the epidermis and the hypodermis

Keratinization

The formation

In some cultures, women must be covered completely, except for their eyes, when they go outside. Explain why these women may develop bone problems later in life

The hormone cholecalciferol (vitamin D3) is needed to form strong bones and teeth. When the body surface is covered, UV light cannot penetrate to the blood in the skin to begin vitamin D3 production, resulting in fragile bones.

Identify the common purpose that the integumentary system serves for all body systems.

The integumentary system provides the whole body, and thus all its systems, mechanical protection against environmental hazards

identify the layers of the epidermis

The layers of the epidermis are the stratum germinativum, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum

Dandruff is caused by excessive shedding of cells from the outer layer of skin in the scalp. Thus, dandruff is composed of cells from which epidermal layer?

the stratum corneum

Describe a Typical strand of hair

A typical hair is keratinous strand produced by epithelial cells of the hair follicle.

Which type of skin gland is most affected by the hormonal changes that occur during puberty?

Apocrine sweat glands enlarge and increase secretory activity in response to the increase in sex hormones that occurs at puberty.

Older individuals do not tolerate the summer heat as well as they did when they were young, and they are more prone to heat-related illness. What accounts for these changes?

As a person ages, the blood supply to the dermis decreases and merocrine sweat glands become less active. These changes make it more difficult for the elderly to cool themselves in hot weather.

Name the sources of epidermal growth factor in the body

Salivary glands and duodenal glands produce epidermal growth factor (EGF)

Why can skin regenerate effectively even after considerable damage?

skin can regenerate effectively even after undergoing considerable damage because stem cells persist in both the epithelial and connective tissue components of skin. When injury occurs, cells of the stratum germinativum replace cells lost from the dermis.

Connections

1. Blood vessels in the dermis(cardiovascular system) 2.sensory receptors for pain, touch, and temperature( nervous system)

What are the specialized cells of Stratum Germinativum explain?

1. Merkel cells are found in hairless skin and respond to touch 2. Melanocytes are scattered throughout the Stratum germinativum and contain the pigment melanin

Functions of skin

1. PROTECTS underlying tissue 2. EXCRETES salts, water, and organic wastes (glands) 3.MAINTAINS body temperature (insulation and evaporation) 4. SYNTHESIZES vitamin D3 5. STORES lipids 6.DETECTS touch, pressure, pain, and temperature

Structures of the Epidermis from basal lamina to apical surface

1. Stratum germinativum 2. Stratum spinosum 3. Stratum granulosum 4. Stratum lucidum - only present in thick skin 5. Stratum corneum-thicker in thick skin compared to thin skin

2 components of cutaneous membrane

1.Outer epidermis 2.Inner dermis

thin skin vs. thick skin

1.Thin skin- covers most of the body, and has 4 layers of keratinocytes 2.Thick skin- covers palms of the hands and soles of the feet, it has 5 layers of keratinocytes and the stratum corneum is extremely thick

Describe a typical fingernail

A fingernail is a keratinous structure produced by epithelial cells of the nail root that protects the fingertip.

Inner dermis

Connective tissues

Deodorants are used to mask the effects of secretions from which type of skin gland?

Deodorants are used to mask the odor of apocrine sweat gland secretions, which contain several kinds of organic compounds; some of these compounds have an odor, and others produce an odor when metabolized by skin bacteria.

identify some roles of epidermal growth factor pertaining to the epidermis

Epidermal growth factor promotes the division of germinative cells in the stratum germinativum and stratum spinosum, accelerates the production of keratin in differentiating keratinocytes, stimulates epidermal development and epidermal repair after injury, and stimulates synthetic activity and secretion by epithelial glands.

Once a burn on the forearm that destroys the epidermis and extensive areas of the deep dermis heals, will hair grow again in the affected area?

Even though hair is a derivative of the epidermis, the follicles are in the dermis. Where the epidermis and deep dermis are destroyed, new hair will not grow.

Why does swimming in fresh water for an extended period cause epidermal swelling?

Fresh water is hypotonic with respect to skin cells, so water moves into the cells by osmosis, causing them to swell.

Explain the relationship between sunlight exposure and vitamin D3 synthesis

In the presence of ultraviolet radiation in sunlight, epidermal cells in the stratum spinosum and stratum germintivum convert a cholesterol-related steroid into cholecalciferol, also known as vitamin D3.

Outer epidermis

Is stratified squamous tissue

Subcutaneous layer

Is the superficial fascia or hypodermis its below the dermis made of adipose tissue and is the location of hypodermic injections

what is keratin?

It is a tough fibrous protein. It makes up hair and nails

What is Keratohyalin?

It is dense granules, and cross-link keratin fibers

Where does nail growth occur?

Nail growth occurs at the nail root, an epidermal fold that is not visible from the surface.

Accessory structures

Nails, hair, and glands(exocrine) They originate in the dermis and extend through the epidermis to the skin surface

Some criminals sand the tips of their fingers so as to leave recognizable fingerprints. Would this practice permanently remove fingerprints? why or why not?

Sanding the tips of the fingers will not permanently remove fingerprints. The ridges of the fingerprints are formed in layers of the skin that are constantly regenerated, so these ridges will eventually reappear. The pattern of the ridges is determined by the arrangement of tissues in the dermis, which is not affected by sanding.

What are the functions of sebaceous secretions?

Sebaceous secretions (called sebum) lubricate and protect the keratin of the hair shaft, lubricate and condition the surrounding skin, and inhibit the growth of bacteria.

Cutaneous membrane

Skin

Stratum lucidum

The "clear layer" it covers the stratum granulosum and is only in thick skin

Stratum Granulosum

The "grainy layer" Stops dividing and starts producing keratin and keratohyalin

Stratum Corneum

The "horn layer" it is the exposed surface of skin it has 15-30 layers of keratinized cells, has water resistant, they are shed and replaced every 2 weeks

Stratum Spinosum

The "spiny layer" -produced by division of stratum germinativum -8-10 layers of keratinocytes bound by desmosomes -cells shrink until cytoskeleton sticks out (Spiny) They continue to divide, increasing the thickness of epithelium They contain dendritic cells, which are active in the immune system

What term is used to describe the thickened stratum corneum underlying the free edge of a nail?

The area of thickened stratum corneum under the free edge of a nail is called the hyponychium .

What accounts for the ability of the dermis to undergo repeated stretching?

The presence of elastic fibers and the resilience of skin turgor allowed the dermis to undergo repeated cycles of stretching and recoil (returning to its original shape).

Why is the skin important to muscular system activity?

The skin synthesizes vitamin D3, which is essential for normal calcium absorption. Calcium ions play a key role in muscle contraction

Name the 2 pigments contained in the epidermis

The two pigments contained in the epidermis are carotene, an orange-yellow pigment, and melanin, a brown, yellow-brown, or black pigment.

Where are there more nuclei in the epidermis?

There are more nuclei in the epidermis towards the basal lamina because those are where the alive skin cells are, which allows more reproduction of nuclei.

A splinter that penetrates to the third layer of the epidermis of the palm is lodged in which layer?

This stratum granulosum

Identify 2 types of exocrine glands found in the skin

Two types of exocrine glands found in the skin are sebaceous glands and sweat glands.

Why does exposure to sunlight or sunlamps darken skin?

When exposed to the ultraviolet radiation in sunlight or sunlamps, melanocytes in the epidermis and dermis synthesize the pigment melanin, darkening the skin.

Why does the skin of a fair-skinned person appear red during exercise in hot weather?

When skin gets warm, arriving oxygenated blood is diverted to the superficial dermis for the purpose of eliminating heat. The oxygenated blood imparts a reddish coloration to the skin

Why does hair turn white or gray with age?

With advancing age, melanocyte activity decreases, leading to gray or white hair.

Stratum Germinativum

is the "Germinative layer" -has many germinative/stem cells or basal cells -is attached to basal lamina by hemidesmosomes -forms a strong bond between epidermis and dermis forms epidermal ridges and dermal papillae increases the surface area of basal lamina

cells of the epidermis

keratinocytes- carry large amounts of keratin, the most abundant cell in the epidermis