Chapter 5: Skin

Question 1

What does the integumentary system consist of?

Answer 1

1. Skin
2. Hair
3. Nails
4. Sweat glands
5. Sebaceous oil glands

Question 2

What are the three sections of the skin?

Answer 2

1. Epidermis
2. Dermis
3. Hypodermis

Question 3

What is the epidermis?

Answer 3

The top of the skin containing four layers of thin skin. It has mostly keratinized(produce fibrous keratin) stratified squamous epithelium which are the major cells of epidermis.

Question 4

What types of cells are in the epidermis?

Answer 4

1. Melanocytes: produces brown to black pigment called melanin. It allows the skin to tan when melanin production is increased.
2. Melanosomes: transfer keratinocytes which help protect again UV.
3. Keratinocytes: Produces keratin, protects the skin, and allows durability.
4. Dendritic cells: macrophages(ingests foreign substances) that are key for the immune system
5. Tactile cells: sensory receptors that sense touch

Question 5

What is the difference between thin and thick skin?

Answer 5

Thick skin contain 5 strata and is located in the hands and feet.
Thin skin contains 4 strata.

Question 6

How many strata are there in the epidermis?

Answer 6

1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum (only in thick skin)
5. Stratum corneum

Question 7

What is the stratum basale?

Answer 7

It is the deepest of all epidermal layers(base layer). This Layer that is firmly attached to dermis. As the cells die they move toward surface. The other daughter cells remains in stratum basale as stem cells.

Question 8

What is the stratum spinosum?

Answer 8

It is several cell layers thick. Allows for resistation from tension and pulling. The Keratinocytes in this layer appear spikey, so they are called prickle cells.

Question 9

What is the stratum granulosum?

Answer 9

Four to six cells thick, but cells are flattened, so layer is thin. The cells flatten, nuclei and organelles disintegrate.
Cells accumulate keratohyaline granules in this layer. Cells also accumulate lamellar granules, a water-resistant glycolipid that slows water loss. It helps form keratin fibers in upper layers.

Question 10

What is the stratum lucidum?

Answer 10

It lies superficial to the stratum granulosum and is found only in thick skin. Consists of thin, translucent band of two to three rows of clear, flat, dead keratinocytes.

Question 11

What is stratum corneum?

Answer 11

Has 20–30 rows of flat, anucleated, keratinized dead cells. It protects deeper cells from the environment, prevents water loss, and protects from abrasion and penetration. It acts as a barrier against biological, chemical, and physical assaults.

Question 12

What is the dermis?

Answer 12

A strong and flexible connective tissue. It has fibers in matrix that bind the body together. Contains nerves, blood vessels, and lymphatic vessels. Also has epidermal hair follicles, oil glands, and sweat glands. It has two layers the papillary and the reticular.

Question 13

What is the papillary layer?

Answer 13

The more superficial layer of the the dermis composed of areloar connective tissue. It has loose fibers that allow phagocytes to patrol for microorganisms. Contains dermal papillae; superficial region of dermis that sends fingerlike projections up into epidermis. These projections have capillary loops, free nerve endings, and 
touch receptors (tactile corpuscles, also called Meissner’s corpuscles). 

In thick skin, dermal papillae lie on top of dermal ridges, which give rise to epidermal ridges. These ridges Collectively ridges are called friction ridges enhance gripping ability, contribute to sense of touch, and the
sweat pores in ridges leave unique fingerprint pattern.

Question 14

What is the reticular layer?

Answer 14

The deepest skin layer it has coarse, dense irregular fibrous connective tissue and has many arteries, veins, sweat/sebaceous glands, and pressure receptors(lamellar corpuscles). The elastic fibers provide stretch-recoil properties. The collagen fibers provide strength and resiliency. Cleavage (tension) lines in the reticular layer are caused by many collagen fibers running parallel to skin surface. It also binds water, keeping skin hydrated, while being externally invisible. Flexure lines of reticular layer are dermal folds at or near joints. Skin’s inability to slide easily for joint movement causes deep creases visible on hands, wrists, fingers, soles, and toes.

Question 15

What causes skin color?

Answer 15

1. Melanin is the only pigment made in skin; made by melanocytes. They are packaged into melanosomes that are sent to shield DNA of keratinocytes from damaging UV sunlight. It comes in two forms reddish yellow to brownish black. Freckles and pigmented moles are local accumulations of melanin.
2. Carotene is a yellow to orange pigment. It is most obvious in palms and soles. It accumulates in stratum corneum and hypodermis.

Question 16

What is hair and what does it do?

Answer 16

It consists of dead keratinized cells. The functions include
warn of insects on skin, hair on head guards against physical trauma, protects from heat loss, and shields skin from sunlight.

Question 17

What does hair consist of?

Answer 17

Hairs (also called pili) are flexible strands of dead, keratinized cells. They contain hard keratin, not like soft keratin found in skin. The hard keratin is tougher and more durable, and cells do not flake off. The shaft area that extends above scalp, where keratinization is complete. Lasty, the root area within scalp, is where keratinization is still going on.

Question 18

What are the three parts of hair shaft?

Answer 18

1. Medulla: central core of large cells and air spaces
2. Cortex: several layers of flattened cells surrounding medulla.
3. Cuticle: outer layer consisting of overlapping layers of single cells.

Question 19

What are hair follicles?

Answer 19

Extends from epidermal surface to dermis. It has hair bulbs that are at the deep end of the follicle, and hair follicle receptor sensory, which is the nerve endings that wrap around bulb. The hair matrix actively divides the area of bulb that produces hair cells. It is connected by the arrector pili that are a small band of smooth muscle attached to follicle. The hair papilla is a dermal tissue containing a knot of capillaries that supplies nutrients to growing hair. The wall of follicle is composed of the peripheral connective tissue sheath that is derived from dermis. It also contains the glassy membrane and is the thickened basal lamina. Lastly, it has the epithelial root sheath that is also derived from epidermis.

Question 20

What are nails and what do they do?

Answer 20

They are scale-like modifications of epidermis that contain hard keratin. They act as a protective cover for distal, dorsal surface of fingers and toes. Consist of free edge, nail plate, and root. The nail bed is epidermis underneath keratinized nail plate. The nail matrix is the thickened portion of bed responsible for nail growth. Nails normally appear pink because of underlying capillaries
It has..
-Nail folds: skin folds that overlap border of nail
-Cuticle: nail fold that projects onto surface of nail body
-Hyponychium: area under free edge of plate that accumulates dirt
-Lunule: thickened nail matrix, appears white

Question 21

What are sweat glands?

Answer 21

All skin surfaces except nipples and parts of external genitalia contain sweat glands. There are two main types
eccrine and aporcine sweat glands. They contain myoepithelial cells that contracts upon the nervous system stimulation to force sweat into ducts.

Question 22

What are eccrine sweat glands?

Answer 22

Most abundant throughout the human body. Found mostly on palms, soles, and forehead. It functions in thermoregulation, which regulates by sympathetic the nervous system. They secrete sweat.

Question 23

What are aporcine sweat glands?

Answer 23

They are confined to axillary and anogenital areas. Secreting viscous milky or yellowish sweat that contains fatty substances and proteins that starts at puberty.
Types of these glands include..
-Ceruminous glands: lining of external ear canal; secrete cerumen(earwax).
-Mammary glands: secretes milk

Question 24

What are sebaceous glands?

Answer 24

Mostly glands that develop from hair follicles and secrete into hair follicles. They are stimulated by hormones, especially androgens. It softens the hair and skin. Also secrete sebum which is the oily holocrine secretion.

Question 25

What are the functions of the skin?

Answer 25

1. Skin is first and foremost a barrier
2. Protection
3. Body temperature regulation
4. Cutaneous sensations
5. Metabolic functions
6. Blood reservoir
7. Excretion of wastes

Question 26

How does skin protect us?

Answer 26

1. Chemical barrier
2. Skin secretes many chemicals, such as: sweat, which contains antimicrobial proteins, sebum and defensins, which kill bacteria, and cells also secrete antimicrobial defensin.
3. Acid mantle low pH of skin retards bacterial multiplication.
4. Melanin provides a chemical barrier against UV radiation damage.
5. Physical barrier
6. Some chemicals have limited penetration of skin
7. Lipid-soluble substances
8. From plants (e.g., poison ivy), organic solvents (acetone, paint thinner), salts of heavy metals (lead, mercury), Some drugs (nitroglycerin), Drug agents (enhancers that help carry other drugs across skin
9. Biological barriers
10. Epidermis contains phagocytic cells and dendritic cells that engulfs foreign antigens (invaders) and present to white blood cells, activating the immune response. Also contains dermal macrophages; activate immune system by presenting foreign antigens to white blood cells
11. DNA can absorb harmful UV radiation, converting it to harmless heat.