The Integumentary System: Structure, Functions, and Accessory Structures - Prof. Louis M. , Study notes of Physiology

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The Integumentary System

What do you get from studying the skin?

Goosebumps? Well maybe but what about…

• Bloodflow is critical to its function
• It’s protective functions are diverse:
  • It responds to sunlight
  • It actively participates in control of body temperature
  • Receptors critical to senses found here
• Layering is a common approach in this and

other body systems

The Integumentary System

• Combination of the four tissues
• Varies in thickness
• Structures that are part of the

integument:

• Skin – technically the epidermis and dermis only
• Hair
• Nails
• Glands

Functions

• Protection
  • Covering
  • Protects parts from
    • Trauma
    • Infection
    • Ultraviolet radiation
    • Water loss
  • Nails for scratching
• Thermoregulation
• Sensation
• Synthesizes vitamin D
• Excretion (insignificant)

Epidermis

• Avascular
• Composed of cells arranged into layers or strata.
• Separated from dermis by basement membrane

Epidermal Cells

Cell types

• Keratinocytes

• Keratinization

• Melanocytes

• Skin color

• Langerhans’ cells

• Merkel’s cells

Desquamate

Epidermal Layers and Keratinization

Back to Epidermis

Dermis

Dermis

Two layers variable in thickness

• Reticular : some adipose, hair follicles, nerves, oil glands, ducts of sweat glands, heat sensors.
• Papillary : capillary beds Irregular fibrous connective tissue fiber orientation results in cleavage lines Rich blood supply
• Important in thermoregulation
• Decubitus or bed sores Nervous tissue and sensory receptors Hair follicles Nail bed

Hypodermis

• Deep to skin
• Consists of loose connective tissue with collagen and elastic fibers
• Types of cells
  • Fibroblasts
  • Adipose cells
  • Macrophages
• Contains about one-half of body’s fat. Functions as
  • Energy source
  • Insulation
  • Padding

Cleavage (Tension) Lines and

Striae

• Cleavage ( tension ) lines : elastin and collagen fibers oriented in some directions more than in others
• Important in surgery
• If skin is overstretched, striae (stretch marks) occur

Back to Dermis

Skin Color

Determined by 3 factors

• Pigments
• Blood circulating through the skin
  • Imparts reddish hue and increases during blushing, anger, inflammation
  • Cyanosis : blue color caused by decrease in blood oxygen content
• Thickness of stratum corneum

Pigments

Pigments

• Carotene: yellow pigment. From vegetables. Accumulates in stratum corneum, in adipose cells of dermis, and in hypodermis.
• Melanin: provides for protection against UV light

Albinism: Production determined by genetics, hormones, exposure to light Back to Epidermis

Thick and Thin Skin

• Thick skin
  • Has all 5 epithelial strata
  • Found in areas subject to pressure or friction
  • Fingerprints and footprints = Papillae of underlying dermis in parallel rows
  • No hair
• Thin skin
  • More flexible than thick skin
  • Has hair
  • Covers rest of body
• Skin thickness varies from 0.5 to 5.0 mm

Accessory Skin Structures: Hair

• Found everywhere on human body except palms, soles, lips, nipples, parts of external genitalia, and distal segments of fingers and toes
• Shaft protrudes above skin surface
• Root located below surface; base of root is the hair bulb

Hair Functions

• Sign of sexual maturity
• Wick for secretions
• Protection for eyes and nose
• Protection against friction
• Insulation

Accessory Skin Structures:

Glands- Sebaceous (Oil)

• Holocrine (death of

secretory cells)

• Oily secretion
• Prevents drying and

may inhibit bacteria

• Most empty into hair

follicle

Accessory Skin Structures:

Glands- Sudoriferous (Sweat)

Merocrine or eccrine. Most common.

Apocrine. Active at puberty.

Ceruminous glands

Mammary glands