Anatomy of the skin

1
Anatomy of the skin

• Integument System

2
Composed of three layers

• 1. Epidermis
• a. composed of several thin layers
• b. stratum basale, stratum spinosum, stratum
  granulosum, stratum lucidum, stratum corneum
• c. the several thin layers of the epidermis
  contain the following

3
The several thin layers of the epidermis contain
the following

• (1). melanocytes, which produce melanin, a
  pigment that gives skin its color and protects it
  from the damaging effects of ultraviolet
  radiation
• (2). keratinocytes, which produce keratin, a
  water-repellent protein that gives the epidermis
  its tough, protective quality

4
2. Dermis

• a. composed of a thick layer of skin that
  contains collagen and elastic fibers, nerve
  fibers, blood vessels, sweat and sebaceous
  glands, and hair follicles

5
3. Subcutaneous tissue

• a. Beneath the dermis is subcutaneous layer. It
  is also called the superficial fascia or
  hypodermis.
• b. This consists of areolar and adipose tissue
• c. composed of a fatty layer of skin that
  contains blood vessels, nerves, lymph, and loose
  connective tissue filled with fat cells

6
B. Functions of the integument

• 1. Protection
• a. intact skin prevents invasion of the body by
  bacteria
• b. water loss
• c. ultraviolet light

7
B. Functions of the integument- Thermoregulation

• a. intact skin facilitates heat loss and cools
  the body when necessary through the following
  processes
• (1) production of perspiration which assists in
  cooling the body through evaporation
• (a) Sweat glands are stimulated in response to
  heat and are inactive in the cold temperatures

8
B. Functions of the integument- Thermoregulation

• (2) production of vasodilatation to increase the
  blood supply to the skin surface which assists in
  facilitating heat loss from the body through
  radiation and conduction

9
B. Functions of the integument- Thermoregulation

• b. intact skin prevents heat loss and warms the
  body when necessary through the following
  processes
• (1). prevention of the production of
  perspiration which inhibits cooling the body
  through evaporation
• (2). production of vasoconstriction to decrease
  the blood supply to the skin surface which
  assists in preventing heat loss from the body
  through radiation and conduction

10
B. Functions of the integument- Thermoregulation

• (3). production of gooseflesh by contraction of
  the arrector pili muscles attached to hair
  follicles in order to stand skin hairs on end
  thus allowing them to entrap a thick layer of
  "insulator air" next to the skin which assists in
  preventing heat loss from the body through
  radiation and conduction

11
B. Functions of the integument

• 3. Fluid and electrolyte balance
• a. intact skin prevents the escape of water and
  electrolytes from the body
• 4. Vitamin D synthesis
• a. intact skin facilitates the synthesis of
  vitamin D through conversion of the initial
  precursor of the vitamin to the second precursor
  of the vitamin in the skin by the sun's
  ultraviolet rays

12
Functions of the Integument

• 5. Sensation
• a. intact skin assists the body in receiving
  sensory stimuli from the environment by
  activation of skin receptors for pain, touch,
  pressure, and temperature

13
C. Epidermis

• The epidermis is composed of four to five layers,
  depending on its location in the body. Where the
  exposure to friction greatest, such as the palms
  and soles, the epidermis has five layers.

14
5 Layers of the Epidermis

• 1. Stratum basale bottom layer (innermost
  layer)
• Also known as Stratum Germanitivum
• 1 to 2 cell layers thick
• Closest to the blood supply
• Actively mitotic
• As these cells multiply, they push up toward the
  surface and become part of the layers.
• Their nuclei degenerate, and the cells die.
• Eventually, the cells are shed from the top layer
  of the epidermis.
• Contains melaocytes the cells that produce
  melanin, a pigment that ranges in color from
  yellow to brown to black.

15
(No Transcript)
16
5 Layers of the Epidermis

• 2. Stratum spinosum
• The layer of the epidermis contains eight to ten
  rows of polyhedral (many-sided) cells that fit
  closely together.
• The surfaces of these cells assume a prickly
  appearance when prepared for microscopic
  examination.
• The stratum basale and the stratum spinosum are
  sometimes collectively referred to as the stratum
  germinativum to indicate where the new cells are
  germinating.

17
(No Transcript)
18
5 Layers of the Epidermis

• 3. Stratum granulosum
• The third layer of the epidermis consists of
  three to five rows of five rows of flattened
  cells that contain darkly staining granules of a
  substance called Keratin.
• Keratin is a waterproofing protein found in the
  top layer of the epidermis.
• The nuclei of the cells in the stratum granulosum
  are in various stages of degeneration. As these
  nuclei breakdown, the cells are no longer capable
  of carrying out vital metabolic reactions and
  die.

19
(No Transcript)
20
5 Layers of the Epidermis

• 4. Stratum lucidum
• present only in thick skin
• This layer is quite pronounced in the thick skin
  of the palms and soles.
• It consists of several rows of clear, flat, dead
  cells that contain droplets of a substance called
  eleidin(this is translucent) and eventually
  becomes transformed into keratin.

21
(No Transcript)
22
5 Layers of the Epidermis

• 5. Stratum corneum
• Continually sloughed off and replaced by cells
  from the deeper layers. Cells remain for 2 weeks
  before shedding.
• This layer consists of 25 to 30 rows of flat,
  dead cells completely filled with keratin and
  cornied(hardened) in order to prevent water loss.
• These cells are continuously shed and replaced.
  They peel off in sheets(sunburn)
• The stratum corneum serves as an effective
  barrier against light and heat waves, bacteria,
  and many chemicals.

23
(No Transcript)
24
D. Dermis

• 1. The dermis consists of
• a. Blood vessels
• b. Nerves
• c. Accessory structures in it

25
The Dermis

• 2. The second principal apart of the skin, the
  dermis, is composed of two layers
• 1. Papillary layer
• a. The upper region of the dermis, about 20
  of the thickness of the total layer, is named
  papillary region or layer.

26
Papillary layer- cont.

• b. The papillary region consists of loose
  connective tissue containing fine elastic fibers
  and is fragile.
• c. It is uneven and has fingerlike projections
  from its superior surface called dermal papillae,
  which indent the epidermis above. This increases
  friction and enhance gripping ability of the
  fingers and feet. They have sweat pores and leave
  unique identifying films of sweat called
  fingerprints on almost any surface.

27
(No Transcript)
28
The Dermis

• 2. Deeper reticular layer
• a. It consists of dense, irregularly arranged
  connective tissue containing interlacing bundles
  of collagenous and coarse elastic fibers.
• b. It is highly vascularized (blood)
• c. It is called reticular layer because the
  bundles of collagenous fibers interlace in a
  netlike manner.

29
Deeper reticular layer- cont.

• d. spaces between the fibers are occupied by a
  small quantity of adipose tissue, hair follicles,
  nerves, oil glands, and ducts of sweat glands.
• e. Various thickness of the reticular region is
  responsible for differences in the thickness of
  the skin.

30
Deeper reticular layer- cont.

• f. The combination of collagenous and elastic
  fibers in the reticular region provides the skin
  with strength, extensibility, and elasticity.
• The ability of the skin to stretch can seen in
  pregnancy, obesity, and edema.

31
E. Subcutaneous Layer

• 1. Also called the Superficial Fascia
• 2. The hypodermis anchors the skin to the
  underlying organs
• 3. The hypodermis has adipose tissue in it, which
  acts as
• a. heat insulator
• b. used as an energy source

32
(No Transcript)
33
F. Skin Color

• 1. The color of the skin is due to melanin, a
  pigment in the epidermis carotene, a pigment
  mostly in the dermis and blood in the
  capillaries in the dermis.
• a. The amount of melanin varies the skin color
  from pale yellow to black.
• b. The pigment is found primarily in the basale
  and spinosum layers.
• c. Melanin is synthesized in cells called
  melanocytes. Since the number of melaocytes is
  about the same in all races, differences in skin
  color are to the amount of pigment the
  melanocytes produce and disperse.

34
Skin Color- cont.

• 2. An inherited inability of an individual in any
  race to produce melanin is called albinism.
• a. The pigment is absent in the hair and eyes
  as well as the skin.
• b. An individual affected with albinism is
  called an albino.

35
Skin Color- cont.

• 3. In some people, melanin tends to form in
  patches called freckles.
• a. Melanocytes synthesize melanin from the
  amino acid tyrosine in the presence of an enzyme
  called tyrosinase. Exposure to ultraviolet
  radiation increases the enzymatic activity of
  melaocytes and leads to increased melanin
  production.

36
(No Transcript)
37
Skin Color- cont.

• 4. Melanin serves a vital protective function
  against radiation.
• a. Overexposure of the skin to the ultraviolet
  light of the sun may lead to skin cancer. Among
  the most malignant and lethal skin cancers is
  melanoma(dark tumor), cancer of the melanocytes.
  Fortunately, most skin cancers are operable.

38
Skin Color- cont.

• 5. Another pigment, called carotene is found in
  the stratum coreum and fatty areas of the dermis
  in Oriental people. Together carotene and melanin
  account for the yellowish hue of their skin.

39
(No Transcript)
40
G. Hair

• The following are derived from the epidermis and
  are embedded in the dermis
• a. Hair
• b. Sweat glands
• c. Nails
• d. Sebaceous glands

41
Hair- continued

• 1. Hair and hair follicles
• a. Known as pili, are found on the entire body
  surface except
• a. eyelids
• b. palms of the hands
• c. soles of the feet
• d. lips
• b. They are organs of sensation and protection
  for the skin.

42
Hair- continued

• 2. Hair follicle
• a. a mass of epidermis, extending down into the
  dermis and forming a small tube
• 3. Hair fiber consists of
• a. shaft extending above the skin surface
• b. Root lying in the hair follicle
• c. bulb
• 1. connective tissue
• 2. blood vessels
• 3. nerves

43
Hair- continued

• 4. Associated with each hair is the following
• a. erector pili muscle
• b. nerve endings
• c. sebaceous gland
• 5. How does hair grow
• a. Cells divide in the hair bulb
• b. The new cells push the old cells through the
  follicle, bringing about new hair growth
• c. As the cells become keratinized, they die and
  firm hair fibers.

44
(No Transcript)
45
H. Nails

• 1. Protective plates in the fingers and toes that
  are formed from growth of the epidermis into the
  dermis
• 2. Nails are thin plates of keratinized stratum
  corneum resting on a nail bed.

46
Nails- continued

• 3. Each nail has a
• a. free edge
• b. nail body
• c. nail root
• 4. The nail bed is supplied with blood vessels

47
Nails- continued

• 5. Nail structures
• a. cuticle
• b. lunula - thick and white, near the cuticle
• 6. Functions for the distal part of the fingers
• a. protection
• b. structure
• c. support

48
(No Transcript)
49
I. Glands

• 1. The glands found in the skin are of two types
• a. Sweat glands(duct glands)
• 1. known as sudoriferous glands
• 2. most numerous skin glands

50
Sweat Glands- cont.

• 3. Divided into
• a. eccrine sweat glands
• 1. ordinary sweat glands
• Watery sweat
• 2. widely distributed over the body

51
Sweat Glands- cont.

• b. Apocrine Glands
• 1. sweat glands
• a. larger sweat glands
• b. white cloudy substance that can be
  metabolized by bacteria to produce end products
  that have odors
• c. Groin and arm pits
• d. Active during sexual and emotional encounters

52
(No Transcript)
53
2. Mammary Glands

• a. Production and secretion of milk

54
3. Ceruminous glands

• a. ear canal secretes wax
• 1. ear wax cerumin
• 2. traps foreign substances

55
c. Sebaceous glands

• 1. Secrete the substance sebum, usually into hair
  follicles
• (a). Consists primarily of lipids oils that
  keeps hair supple and the skin soft and pliant
  while preventing excess water loss from the
  epidermis.
• (b). Anti-bacteria activity
• (c). Acne is a common disorder of the sebaceous
  glands.

56
(No Transcript)
57
Burns

• Over 2,000,00 people are treated for burns each
  year, about 12,000 die of them die from their
  injury
• There are 3 levels of burns
• First-degree
• Second-degree
• Third-degree

58
First-degree burn

• Only the epidermis is burned
• Least severe of all types of burns

59
Second-degree burns

• The epidermis and upper dermis are burned
• Blisters occur

60
Third-degree burns

• Epidermis and dermis are burned
• Most severe
• Nerve damage (ends burned off)
• Skin is blanched (gray-white), red or black
• Skin must be replaced (grafting)

61
Skin Cancer

• Most often caused by UV radiation
• Can be influenced by chemicals, infections and
  physical trauma
• Three main types of skin cancer
• Basal cell carcinoma
• Squamous cell carcinoma
• Malignant melanoma

62
Basal Cell Carcinoma

• The least malignant type
• Most common type of skin cancer
• Removal of the cancer area by surgery cures 99
  of all cases

63
Squamous Cell Carcinoma

• Starts in the keratinocytes of the stratum
  spinosum
• Surgical removal and radiation therapy cures most
  cases

64
Malignant Melanoma

• Cancer of the melanocytes
• Most dangerous form of cancer
• Accounts for 5 of skin cancers
• 1/3 of cases develop from pigmented moles

65
Aging

• As skin gets older, the rate of epidermal cell
  replacement slows down
• Skin gets thinner and the susceptibility to
  injury increases
• Fewer lubricating substances are produced
• Elastic fibers lose elasticity wrinkles