Catalyst Questions

• What are the five layers of the epidermis?

• List the functions of the skin.

• How does the skin respond to aging?

• What is the rule of nines?

Lets Review…

• Resistance to trauma and infection, water retention, vitamin D synthesis, sensation, thermoregulation, and nonverbal communication.

• Stratum basale, stratum spinsum, stran granulosum, stranum lucidum, and stratum corneum.

5-3

Epidermal Layers and Keratinization

5-4

Effects of Aging on the Integumentary System

• Skin more easily damaged because epidermis thins and amount of collagen decreases

• Skin infections more likely• Wrinkling occurs due to decrease in elastic fibers• Skin becomes drier • Decrease in blood supply causes poor ability to

regulate body temperature• Functioning melanocytes decrease or increase;

age spots• Sunlight ages skin more rapidly

5-5

The Rule of Nines• Used to estimate amount of body that is burned. • Note differing proportions in adult and child.

Class Updates…

• Review day on Wednesday August 24th, plus in class project!

• Test corrections on due on Monday, September 22nd.

• Test will be on Friday, 26th !

Review Sheets

• A completed review sheet will be worth +10 on the exam.

Dermis, Hypodermis, and Structures of the Integumentary

System

Objectives

• You will be able to describe the histological structure of the epidermis, dermis, and subcutaneous tissue

• You will be able to describe the function of each of the individual parts in the epidermis, dermis, hypodermis

5-10

Dermis• Gives structural strength. C.T. with many fibers, fibroblasts,

macrophages. Some adipocytes and blood vessels. • Contains nerves, blood vessels, hair follicles, smooth

muscles, glands, and lymphatic vessels.• Sensory functions: pain, itch, tickle, temperature, touch,

pressure, two-point discrimination.

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Two Layers of the Dermis• Two layers variable in thickness

– Papillary. Superficial (outer) 1/5. Areolar with lots of elastic fibers. Dermal papillae, capillary beds. Fingerprints. Whorls of ridges. Touch receptors (Meissner’s), free nerve endings sensing pain

– Reticular: Deep (inner) 4/5. Dense irregular C.T. Collagen and elastic fibers. In the figure see: some adipose, hair follicles, nerves, oil glands, ducts of sweat glands, heat sensors.

Dermis

• The dermis is directly below the epidermis and is a connective tissue layer.

• It is composed mainly of collagen but also contains other tissues like elastic and reticular fibers, fibroblasts, and other fibrous connective tissue cells.

• It is well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings.

• The hair follicles and nail roots are embedded in the dermis.

Dermis, cont’d

• Smooth muscles associated with hair follicles contract in response to such stimuli as cold, fear, and touch.

• In the face, skeletal muscles attach to dermal collagen fibers and produce such expression as a smile, a wrinkle of the forehead, and the lifting of an eyebrow.

Dermis, cont’d

• The boundary between the epidermis and dermis is very obvious and wavy. The upward waves are like finger-like extensions of the dermis called dermal papillae. – NOTE: DO NOT CONFUSE THIS WITH THE

DERMAL PAPILLA OF THE HAIR!!

• The downward waves are like extensions of the epidermis called epidermal ridges.

Dermis, cont’d

• There are two zones of the dermis called the papillary and reticular layers.

• The papillary layer is a thin zone of areolar tissue in and near the dermal papillae. – The loosely organized tissue of the papillary layer

allows for mobility of leukocytes (defense cells) and other defenses against organisms introduced through breaks in the epidermis.

• The reticular layer of the dermis is deeper and much thicker. – It consists of dense, irregular connective tissue.

Hypodermis

• Beneath the skin is a layer called the hypodermis, aka the subcutaneous tissue or superficial fascia.

• The boundary between the dermis and hypodermis is indistinct, but the hypodermis generally has more areolar and adipose tissue (fat).

• The hypodermis binds the skin to the underlying tissues and pads the body.

• Subcutaneous fat is hypodermis composed predominantly of adipose tissue. – This fat serves as an energy reservoir and thermal

insulation.

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Cleavage (Tension) Lines

• Cleavage (tension) lines: elastic and collagen fibers oriented in some directions more than in others

• Important in surgery– If incision parallel to lines,

there is less gapping, faster healing, less scar tissue

• If skin is overstretched, striae (stretch marks) occur

Structures

• -dermal papillae• -hair follicle• -sebaceous gland• -hair receptor• -apocrine sweat gland• -hair bulb• -sensory nerve fibers

• -piloerector muscle• -lamellated corpuscle-

these are receptors for deep pressure

• -Tactile corpuscles- receptors of light touch and texture

• -merocrine sweat gland• -blood capillaries• -hypodermis• -epidermis

Structures of Integumentary System

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Effects of Aging on Tissues Continued..

• Cells divide more slowly • Collagen fibers become more irregular in structure,

though they may increase in number– Tendons and ligaments become less flexible and more

fragile

• Elastic fibers fragment, bind to calcium ions, and become less elastic– Arterial walls and elastic ligaments become less elastic

• Changes in collagen and elastin result in – Atherosclerosis and reduced blood supply to tissues– Wrinkling of the skin– Increased tendency for bones to break

• Rate of blood cell synthesis declines in the elderly• Injuries don’t heal as readily