1. Chapter 5
Integumentary System

2. I. The Skin A. General Information Skin, Hair, Nails, Glands
Skin is the largest organ of the body (1.2 to 2.2 m2 or 22 ft2)
Ranges in thickness from 1.5 to 4.0 mm with an average thickness of 1-2 mm
It consists of the epidermis and the dermis
Attached by fibers to the underlying layer or subcutaneous layer known as the hypodermis, which is mainly areolar and adipose connective tissues

3. Hair shaft
Dermal papillae
Epidermis
Subpapillary
vascular plexus
Papillary
layer
Pore
Appendages
of skin
Dermis
Reticular
layer
• Eccrine sweat
gland
• Arrector pili
muscle
Hypodermis
(superficial fascia)
• Sebaceous
(oil) gland
• Hair follicle
Nervous structures
• Hair root
• Sensory nerve fiber
Cutaneous vascular
plexus
• Pacinian corpuscle
• Hair follicle receptor
(root hair plexus)
Adipose tissue

4. II. Epidermis
It’s a keratinized stratified squamous epithelial tissue that includes four different cell types, and four to five distinct layers
Avascular; nourished by diffusion from capillaries of the papillary layer of the dermis
Separated from dermis by basement membrane

5. . Melanocyte Melanin granule Tactile (Merkel) cell Sensory nerve
ending
Epidermal
dendritic
Dermis
Keratinocytes
Desmosomes
(b)
(a)
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Stratum granulosum
Three to five layers of flattened cells, organelles
deteriorating; cytoplasm full of lamellated gran-
ules (release lipids) and keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
Stratum basale
Deepest epidermal layer; one row of actively
mitotic stem cells; some newly formed cells
become part of the more superficial layers.
See occasional melanocytes and epidermal
dendritic cells.

6. A. Cells of the Epidermis
The epidermis contains the following four types of cells:
1. Keratinocytes
They are arranged in 4 layers and represent the majority of the cells in the epidermis
They start as cuboidal cells and become squamous as they reach the apical surface
They produce keratin for strength as well as a water repellent sealant

7. Melanocyte
Melanin granule
Tactile
(Merkel) cell
Sensory
nerve ending
Epidermal
dendritic cell
Dermis
Keratinocytes
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Stratum granulosum
Three to five layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) and
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
Stratum basale
Deepest epidermal layer; one row of actively
mitotic stem cells; some newly formed cells
become part of the more superficial layers. See
occasional melanocytes and epidermal
dendritic cells.
Desmosomes
(b)

9. 2. Melanocytes
Produce the pigment melanin which contributes to skin color
Melanin granules cluster at the apical surface of the nucleus of keratinocytes and protect them from UV light
Other cells present in the epidermis are:
Langerhans cells and Merkel cells

11. B. Layers of the Epidermis
1. The Stratum basale (germinativum)
It’s the deepest layer of the epidermis
It consists of a single row of stem cells alternating with melanocytes (10-25%) and merkel cells
The stem cells in this row are actively dividing (highly mitotic) and producing new keratinocytes that replace the cells that are lost at the apical surface of the skin

12. . Keratinocytes Stratum corneum
Melanocyte
Melanin granule
Tactile
(Merkel) cell
Sensory
nerve ending
Epidermal
dendritic cell
Dermis
Keratinocytes
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Stratum granulosum
Three to five layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) and
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
Stratum basale
Deepest epidermal layer; one row of actively
mitotic stem cells; some newly formed cells
become part of the more superficial layers. See
occasional melanocytes and epidermal
dendritic cells.
Desmosomes
(b)

15. 2. The stratum spinosum
It consists of several (8-10) rows of keratinocytes that may still be able to divide
Projections or extensions of the melanocytes are located in this layer
3. The stratum granulosum
Consists of 3-5 layers of flattened keratinocytes that begin to die (apoptosis) at the upper layers
Keratin (provide strength) and Lamellar granules (produce water repellent) are produced in this layer

16. . Keratinocytes Stratum corneum
Melanocyte
Melanin granule
Tactile
(Merkel) cell
Sensory
nerve ending
Epidermal
dendritic cell
Dermis
Keratinocytes
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Stratum granulosum
Three to five layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) and
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
Stratum basale
Deepest epidermal layer; one row of actively
mitotic stem cells; some newly formed cells
become part of the more superficial layers. See
occasional melanocytes and epidermal
dendritic cells.
Desmosomes
(b)

17. 4. The stratum lucidum
It consists of 2-3 rows of dead, flattened, keratin rich keratinocytes
It is present only in thick skin
5. The Stratum corneum
This layer consists of rows of keratinocytes that are made up mainly of keratin
These cells are continuously being shed and protect the inner layers

19. C. Thick and Thin Skin 1. Thick skin Has all 5 epithelial strata
Found in areas subject to pressure or friction
Palms of hands, fingertips, soles of feet
2. Thin skin
More flexible than thick skin
Covers rest of body

20. III. The Dermis It’s the deeper portion of the skin
It consists mainly of connective tissue containing collagen and elastic fibers
The dermis gives skin its structural strength.
It contains the skin funtional accessories and organelles: nerves, blood vessels, hair follicles, smooth muscles, glands, temperature sensors, touch receptors, free nerve endings (pain receptors), and lymphatic vessels.

21. Epidermis
Hair shaft
Dermis
Reticular
layer
Papillary
Hypodermis
(superficial fascia)
Dermal papillae
Pore
Subpapillary
vascular plexus
Appendages
of skin
• Eccrine sweat
gland
• Arrector pili
muscle
• Sebaceous
(oil) gland
• Hair follicle
• Hair root
Nervous structures
• Sensory nerve fiber
• Pacinian corpuscle
• Hair follicle receptor
(root hair plexus)
Cutaneous vascular
plexus
Adipose tissue

22. A. The Layers of the Dermis
1. Papillary: Superficial (outer) 20% of the dermis.
Consists of areolar c.t. with lots of elastic fibers. Arranged in dermal papillae
2. Reticular: Deep (inner) 80% of the dermis
Consists of dense irregular C.T. with collagen and elastic fibers.
May have pockets of adipose cells

23. B. Skin Color Skin color comes from the combination of three pigments present in the skin: 1) Melanin: produced by melanocytes with help of the enzyme tyrosinase 2) Carotene: from diet 3) Hemoglobin: the pigment in red blood cells (RBC’s) What is cyanosis? What is jaundice? What are decubitus ulcers or bedsores?

31. IV. Appendages of the Skin
1. Sweat (sudoriferous) glands
They are very numerous (3 million) and distributed throughout the body
There are two types of sweat glands: eccrine an apocrine sweat glands
a) Eccrine sweat glands:
They are the most widely distributed sweat glands; become active shortly after birth
produce about 600 ml of sweat per day, which is a filtrate from blood
Eccrine glands release sweat through pores in the skin

32. Epidermis
Hair shaft
Dermis
Reticular
layer
Papillary
Hypodermis
(superficial fascia)
Dermal papillae
Pore
Subpapillary
vascular plexus
Appendages
of skin
• Eccrine sweat
gland
• Arrector pili
muscle
• Sebaceous
(oil) gland
• Hair follicle
• Hair root
Nervous structures
• Sensory nerve fiber
• Pacinian corpuscle
• Hair follicle receptor
(root hair plexus)
Cutaneous vascular
plexus
Adipose tissue

33. The main function of eccrine sweat glands is thermoregulation: to assist in the regulation of body temperature and to a minor extent, the removal of waste (urea, uric acid, ammonia and lactic acid)
b) Appocrine sweat glands: Found mainly in the axillary region, the groin and the bearded regions of adult males
The sweat of apocrine glands contains the same components as sweat from eccrine glands but it also has lipids and proteins
Apocrine glands start functioning at puberty and play no significant role in thermoregulation

35. 1. Sebaceous (Oil) glands
Distributed throughout the body, most of them associated with hair follicles
Produce an oily secretion (sebum), which lubricates the skin and the hair, prevents water evaporation, and inhibits the growth of certain bacteria (bactericidal)
2. Hairs and Hair Follicles
The main functions of the hair are: protection, sensation and filtering out of particles
The root hair plexus: generates nerve impulses when the hair shaft is moved

36. . Sweat pore Sebaceous gland Dermal connective tissue Eccrine
gland duct
Eccrine
gland
Hair in
hair follicle
Secretory cells
(a) Photomicrograph of a sectioned
sebaceous gland (220x)

37. Epidermis
Hair shaft
Dermis
Reticular
layer
Papillary
Hypodermis
(superficial fascia)
Dermal papillae
Pore
Subpapillary
vascular plexus
Appendages
of skin
• Eccrine sweat
gland
• Arrector pili
muscle
• Sebaceous
(oil) gland
• Hair follicle
• Hair root
Nervous structures
• Sensory nerve fiber
• Pacinian corpuscle
• Hair follicle receptor
(root hair plexus)
Cutaneous vascular
plexus
Adipose tissue

38. V. Functions of the Integumentary System
1. Protection:
a) Chemical barriers: protection against UV light by melanin and against microorganisms by sebum
b) Physical / mechanical barriers: protects against dehydration, abrasion or penetration of microorganisms; nails protect ends of digits
c) Biological barriers: WBC’s

39. 2. Temperature Regulation
1) Sweat produced by sudoriferous glands causes evaporative cooling.
2) Arterioles in dermis change diameter as temperature changes. More or less blood flows through the dermis.
3. Cutaneous Sensation
Pressure, temperature, pain, heat, cold, touch, movement of hairs.

42. 4. Metabolic Functions
The precursor molecule of vitamin D is produced in the skin with the help of sunlight
It is then turned into calcitriol by the liver and kidneys
Calcitriol is a hormone that aids in the absorption of calcium from the GI tract
5. Blood Reservoir
6. Excretion: Removal of waste products from the body. Sweat. Water, salt, urea,
ammonia, uric acid

43. VI. Homeostatic imbalances of the Skin
A. Skin Cancer
Occurs from mutations in the in the epidermal cells caused mainly by sun radiation (UV light)
The three most common types of skin cancer are:
1) Basal cell carcinoma: which originates in the keratinocytes of the stratum basale
It’s the most common but the least malignant accounting for 80% of skin cancers and developing relatively slowly

45. 2) Squamous cell carcinoma: it’s the second most common skin cancer occurring in the keratinocytes at the stratum spinosum
3) Melanoma: which involves the melanocytes is the least common skin cancer
It’s the most dangerous skin cancer because is highly metastatic and resistant to chemotherapy
1/3 of them develop from peexisting moles
Assessment through the ABCD rule

47. B. Burns Classifications First-degree Second-degree Third-degree
Skin Grafts
Split skin
Artificial skin
Cadavers or pigs

51. Figure 5.10 Partial thickness and full thickness burns.
Skin bearing partial
thickness burn (1st and
2nd degree burns)
(b)
Skin bearing full
thickness burn
(3rd degree burn)
1st degree
burn
2nd degree
3rd
degree

55. Assessing burns - the "rule of nines"
Burns are assessed in terms of total body surface area (TBSA), which is the percentage affected by partial thickness or full thickness burns (superficial thickness burns are not counted).
Head - 9%
Anterior Torso - 18%
Posterior Torso - 18%
Each Leg - 18%
Each Arm - 9%
Genitalia/perineum - 1%

56. Anterior and posterior
head and neck, 9% 4 1 / 2 %
upper limbs, 18%
lower limbs, 36%
100%
Totals
trunk, 36%
Anterior
trunk,
18% 9%
(Perineum, 1%)