1. Chapter 6
Integumentary System

2. Pretest The nails are part of the integumentary system.
True or False
The nails are part of the integumentary system.
The thickest layer of the epidermis is the stratum corneum.
Cerumen provides waterproofing for the skin.
Sensory receptors allow the body to detect changes in the environment.
The subcutaneous layer cushions underlying organs.

3. Pretest, cont.
True or False
The ultraviolet rays of the sun increase melanocyte activity.
The face does not contain hair.
Hair is produced by hair follicles.
The neck and chest have the most sweat glands.
Vitamin A is necessary for the absorption of calcium in the body.

4. Structure of the Skin
Includes glands, hair, nails, and other structures that are derived from it
Sometimes called the cutaneous membrane
Consists of two layers:
Epidermis: outer layer
Dermis: inner layer
Anchored to underlying structures by subcutaneous tissue

5. Structure of the Skin, cont.
From Jarvis C: Physical examination and health assessment, ed 5, St. Louis, 2008, Saunders

6. Epidermis Consists of stratified squamous epithelium
No blood vessels present
Cells receive nutrients by diffusion from vessels in the underlying tissue
Cells on the bottom actively grow and divide

7. Epidermis, cont. Cells are pushed upward Receive fewer nutrients
Undergo keratinization
Keratin is deposited in the cell
Cell changes shape
By the time the cells reach the surface, they are:
Flat (squamous)
Dead
Cells are sloughed off and replaced by other cells

8. Epidermis, cont.
As cells are pushed upward: take on different appearances and characteristics
Form distinct regions
Five regions (strata) of cells: thick skin (soles of feet and palms of hand)
Four strata: skin that covers the rest of body

9. Epidermis, cont. Strata of the epidermis Stratum basale
Consists of actively dividing columnar cells and melanocytes (produce melanin)
Stratum spinosum
Consists of several layers of cells with spiny processes
This layer combined with the stratum basale is called the stratum germinativum

10. Epidermis, cont. Stratum granulosum Stratum lucidum
Thin region consisting of two or three layers of flattened cells
Keratinization begins in this layer
Stratum lucidum
Translucent band consisting of a few layers of flattened, anucleate cells
Present only in thick skin

11. Epidermis, cont. Stratum corneum Outermost region
Makes up 3/4 of the epidermal thickness
Consists of layers of flattened, dead, keratinized cells
Cells are continually shed and replaced
Keratin present is a tough, water-repellent protein: provides protection against water loss

12. Epidermis, cont.

13. Dermis Dense connective tissue
Contains hair, nails, and certain glands
Contains both collagenous and elastic fibers: provide strength and elasticity
If skin is overstretched: dermis may be damaged
Leaves white scars called striae (“stretch marks”)

14. Dermis, cont. Sensory receptors are present in the dermis
Detect changes in the environment, such as heat, cold, pain, pressure, and touch

15. Dermis, cont. Layers of the dermis Papillary layer: upper layer
Contains numerous papillae (projections) that extend into the epidermis
On the palms, fingertips, and soles of feet: papillae form distinct patterns
Genetically determined and unique for each individual
Basis of fingerprints and footprints
Reticular layer: deeper and thicker than papillary layer

16. Subcutaneous Layer Not actually a part of the skin
Loosely anchors skin to underlying organs
Also known as:
a. Hypodermis
b. Superficial fascia
4. Consists of loose connective tissue and adipose tissue
5. Functions:
Cushions underlying organs
Heat insulator in temperature regulation
Provides energy when necessary

17. Skin Color Melanin: responsible for skin color
Produced by melanocytes (located in stratum basale)
Everyone has same number of melanocytes
Activity of the melanocytes: genetically controlled
Large number of melanin granules: results in dark skin
Fewer granules: result in lighter skin

18. Skin Color, cont. Inability to produce melanin: results in albinism
Very light skin, white hair, and unpigmented irises in the eyes
Ultraviolet light increases melanocyte activity: more melanin is produced
Skin becomes darker or tanned

19. Skin Color, cont. Carotene: yellowish pigment
Some people have carotene (in addition to melanin)
Causes yellow tint to the skin
Pinkish tint: due to blood vessels in the dermis

20. Epidermal Derivatives
Derived from the stratum basale of epidermis
Embedded in the reticular layer of dermis

21. Hair and Hair Follicles
Location of hair
Found on nearly all body surfaces
Absent: Palms of the hands, soles of the feet, lips
Hair is composed of dead, keratinized epithelial cells

22. Hair and Hair Follicles, cont.
Hair is made up of:
Shaft: portion that extends beyond the surface of the epidermis
Root: portion that is below the surface of the skin
Enclosed in a hair follicle: extends through epidermis and embedded in dermis

23. Hair and Hair Follicles, cont.
c. Medulla: central core of the hair
d. Cortex: several layers of cells surrounding medulla
e. Cuticle: outermost covering of the hair
Consists of a single layer of overlapping, keratinized cells

24. Hair and Hair Follicles, cont.
Hair follicle: produces hair
Hair bulb: encloses root of hair
Papilla of dermis: contains blood supply
Single layer of stratum basale cells: provide mitotic cells that produce the hair
Hair color: determined by type of melanin produced by melanocytes (in stratum basale)
Yellow, brown, and black pigments: present in varying proportions to produce different hair colors
With age: melanocytes become less active
Hair in which melanin is replaced with air bubbles is white

25. Hair and Hair Follicles, cont.
c. Arrector pili muscle
Attached to hair follicles
Contraction: causes the hair to “stand on end” and “goose bumps”
Action is controlled by nervous system in response to cold and fright

26. Hair and Hair Follicles, cont.

27. Nails Thin plates of dead stratum corneum
Contain a very hard type of keratin
Nail body: visible portion of the nail
Nail root: covered with skin
Eponychium or cuticle: fold of stratum corneum
Grows onto proximal portion of nail body

28. Nails, cont.
Nail bed: formed by stratum basale growing under nail body
Nail matrix: responsible for nail growth
Lunula: the portion of the body over the matrix
Whitish, crescent-shaped area
Nails appear pink due to rich supply of blood vessels in underlying dermis

29. Nails, cont.
From Jarvis C: Physical examination and health assessment, ed 5, St. Louis, 2008, Saunders

30. Glands Sebaceous glands Generally associated with hair follicles
Found in all areas of the body that have hair
Those not associated with hair follicles: open directly onto surface of skin
Sebum: oily secretion from a sebaceous gland
Keeps hair and skin soft and pliable
Inhibits growth of bacteria on skin
Helps prevent water loss

31. Glands, cont.
From Jarvis C: Physical examination and health assessment, ed 5, St. Louis, 2008, Saunders

32. Glands, cont. 2. Sweat (sudoriferous) glands
a. Widely distributed over the body
• Except for lips, nipples, and parts of the external genitalia
• Most numerous: palms and soles

33. Glands, cont. Types of sweat glands:
Merocrine sweat glands: most numerous and widely distributed
Coiled tube embedded in the dermis
Duct opens onto surface of the skin through a sweat pore
Secretion: primarily water with a few salts
When the body’s temperature increases, glands produce sweat (perspiration): cooling effect on body

34. Glands, cont. Apocrine sweat glands: larger than merocrine glands
Located in axillae and external genitalia
Ducts open into hair follicles in these regions
Secretion: consists of water, salts, and organic compounds (fatty acids and proteins)
Become active at puberty
Stimulated by the nervous system in response to pain, emotional stress, sexual arousal
Secretion is broken down by bacteria: causes body odor

35. Glands, cont. Ceruminous glands
Modified sweat glands found in the external auditory (ear) canal
Secrete an oily, sticky substance: cerumen (earwax)
Repels insects and traps foreign material

36. Functions of the Skin Protection Forms a protective covering
Keratin in the cells: waterproofs the cells and helps prevent fluid loss from the body
Oily secretions of sebaceous glands are acidic: inhibit bacterial growth on skin
Unbroken skin: first line of defense against invading organisms
Melanin: absorbs light and helps protect underlying tissues from the damaging effects of ultraviolet light. Protects underlying tissues from mechanical, chemical, and thermal injury

37. Functions of the Skin, cont.
Sensory reception
Dermis contains sensory receptors for heat, cold, pain, touch, and pressure
Relays information about the environment to the brain
Changes can be made to prevent or minimize injury
Also a means of communication between individuals

38. Functions of the Skin, cont.
3. Regulation of body temperature
When there is excess heat in the body
Small arteries in the dermis dilate
Brings the heat to the surface: can escape into surrounding air
Sweat glands become active
Sweat evaporates to provide cooling of the body

39. Functions of the Skin, cont.
If body temperature falls below normal:
Sweat glands are inactive
Blood vessels in skin constrict
Reduces amount of heat transferred from deeper tissues to surface

40. Synthesis of Vitamin D Vitamin D
Required for absorption of calcium and phosphorus
Essential for normal bone metabolism and muscle function
Skin cells contain a precursor molecule
Converted to vitamin D when exposed to ultraviolet rays of sun

41. Posttest The epidermis consists of simple squamous epithelial tissue.
True or False
The epidermis consists of simple squamous epithelial tissue.
Skin cells grow and multiply in the stratum basale layer of the epidermis.
Melanocytes produce a yellow pigment.
Sebaceous glands are embedded in the dermis.
An individual with a large number of melanin granules in their skin will have dry skin.

42. Posttest, cont.
True or False
The part of the hair that is visible is known as the shaft.
The central core of the hair is known as the cuticle.
Shivering is caused by contraction of the arrector pili muscles.
Sebum keeps hair and skin soft and pliable.
Merocrine glands are responsible for body odor.