The Integumentary System

Objectives: 1. Name the tissue types of composing the epidermis and the dermis. List

the major layers of each and describe the functions of each layer.

2. Describe the factors that normally contribute to skin color. Briefly describe

how changes in skin color may be used as clinical signs of certain disease

states.

3. Compare the structure and locations of sweat and oil glands. Also

compare the composition and functions of their secretions.

4. Compare and Contrast eccrine and apocrine glands.

5. Describe the distribution, growth, and replacement of hairs and their

changing nature of hair during the life span.

6. Describe the functional relationship of arrector pili muscles to the hair

follicle.

7. Describe how skin accomplished at least five different functions.

8. Summarize the characteristics of the three major types of skin cancer.

9. Explain why serious burns are life threatening. Describe how to

determine the extent of a burn and differentiate first-, second- and third-

degree burns.

10. Outline the process of tissue repair involved in normal healing of a

superficial wound.

The Integumentary System Integument is skin

Skin and its appendages make up the

integumentary system

A fatty layer (hypodermis) lies deep to it

1.5-4.0mm in epidermis and dermis.

Two distinct regions

Epidermis (nutrients reach epidermis by diffusion

from interstitial fluid from blood vessels.)

Dermis (only this layer is vascularized)

Functions of skin

Protection

Cushions and insulates and is waterproof

Protects from chemicals, heat, cold, bacteria

Screens UV

Synthesizes vitamin D with UV

Regulates body heat

Prevents unnecessary water loss

Sensory reception (nerve endings)

Subcutaneous Layer (Hypodermis) “Hypodermis” (Greek) = below the skin

“Subcutaneous” (Latin) = below the skin

Also called “superficial fascia” “fascia” (Latin) =band; in anatomy: sheet of connective

tissue

Made of adipose and areolar connective tissue

Fatty tissue which stores fat and anchors skin (areolar tissue

and adipose cells); acts as a shock absorber and an

insulator.

Thickens as we gain weight. Different patterns of

accumulation

(male in anterior abdomen/female in thighs and breasts)

Epidermis:

Keratinized stratified squamous epithelium

Four types of cells Keratinocytes

Melanocytes

Merkel cells

Langerhans cells

Layers (from deep to superficial) Stratum basale or germinativum – single row of cells attached to

dermis; youngest cells

Stratum spinosum – spinyness is artifactual; tonofilaments (bundles of protein) resist tension

Stratum granulosum – layers of flattened keratinocytes producing keratin (hair and nails made of it also)

Stratum lucidum (only on palms and soles)

Stratum corneum – horny layer (cells dead, many layers thick)

(see figure on next slide)

I. Keratinocytes

deepest, produce keratin (tough fibrous protein)

Produce keratin, a fibrous protein that helps the

epidermis protect.

They are connected by desmosomes in the

stratum basale; also continuous mitosis there.

As they are pushed up, they secrete keratin and

become flattened, scale-like and dead.

II. Melanocytes, Merkel cells

and Langerhans cells: Melanocytes -

make dark skin pigment melanin

Spider-shaped cells that make melanin in stratum basale.

Melanin is moved to end of arms of cell and transferred to keratinocytes.

The melanin then collects on the superficial side of the nucleus.

Merkel cells – associated with sensory nerve endings

Langerhans cells – macrophage-like dendritic cells

Cells come from the bone marrow to become macrophages.

Layers of Epidermis: A. Thick vs. Thin skin: palms of hands and soles of feet contain an additional layer of skin, giving them five. The rest of the skin has four distinct layers.

B. Stratum basale or germinativum – The deepest layer of the dermis. Made of a single row of cells attached to dermis; youngest cells (keratinocytes); rapid mitosis occurs here; melanocytes present here.

C. Stratum spinosum – spinyness is artifactual; tonofilaments (bundles of protein) resist tension; several layers thick; consists primarily of tension-resisting bundles of prekeratin filaments; the cells flatten and become spiny because the cells shrink in death but desmosomes hold tight.

Layers of Epidermis continued… D. Stratum granulosum – layers of flattened keratinocytes producing keratin (hair and nails made of it also); Consists of 3-5 layers, cells continue to flatten, internal structures disintegrate, granules develop that help form keratin in upper layers. Cells are now too far from blood vessels and are dead.

E. Stratum lucidum (only on palms and soles---making thick skin); Forms a thin, translucent band of clear, dead keratinocytes.

F. Stratum corneum – horny layer (cells dead, many layers thick); 20-30 cell layers, keratin and plasma membrane protect skin against abrasion, penetration from pathogens and now is waterproof.

Epithelium: layers (on left) and cell types (on right)

Remember…

Four basic types of tissue

Epithelium – epidermis just discussed

Connective tissue - dermis

Muscle tissue

Nervous tissue

Dermis

Strong, flexible connective tissue: your “hide”

Cells: fibroblasts, macrophages, mast cells, WBCs (white blood cells)

Fiber types: collagen, elastic, reticular

Rich supply of nerves and vessels

Critical role in temperature regulation (the vessels)

Two layers (see next slides) Papillary – areolar connective tissue; includes dermal

papillae

Reticular – “reticulum” (network) of collagen and reticular fibers

Layers of the Dermis 1. Papillary Layer–

areolar connective tissue; includes dermal papillae

The upper layer of the dermis where areolar connective tissue with collagen and elastic fibers and blood vessels form a mat.

Its superior surface or borders forms peg like projections called dermal papillae into the epidermis.

These are filled with blood vessels and nerve endings (pain and touch receptors).

Palms and soles have dermal ridges to increase friction (fingerprints.)

2. Reticular Layer – “reticulum” (network) of collagen and reticular fibers

Makes up 80% of dermis; made of dense irregular connective tissue (aka DICT).

Collagen fibers are found in bundles parallel to the surface.

Produces lines of cleavage in between.

Stretch marks develop from this layer.

Fingerprints, palmprints, footprints

Dermal papillae lie atop dermal ridges

Elevate the overlying epidermis into epidermal ridges

Are “sweat films” because of sweat pores

Genetically determined

Flexion creases Deep dermis, from continual folding

Fibers Collagen: strength and resilience

Elastic fibers: stretch-recoil Striae: stretch marks

Tension lines (or lines of cleavage) The direction the bundles

of fibers are directed

The dermis is the receptive

site for the pigment of tattoos

*Dermis layers

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*Dermal papillae

Epidermis and dermis of (a) thick skin and (b) thin skin (which one makes the difference?)