Dr. Mustafa Saad (2021)

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Epidermis

Dermis

Hypodermis

The Skin

(mostly fatty tissue)

The Skin

Fig.1: The layers of the skin.

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• Stratified squamous

keratinized epithelium.

• The epidermal-dermal

junction is not a smooth

line. It is irregular and

characterized by the

interdigitation of

epidermal ridges and

dermal papillae.

• This may be reflected

on the surface.

epidermal

ridges

dermal

papillae

Fig.2: The epidermal-dermal junction.

The Epidermis

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Fig.3: Epidermal-dermal junction. Parts of dermis.

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Layers of the Epidermis

Stratum

basale

Stratum

lucidum

Stratum

corneum

Stratum

spinosum

Stratum

granulosum

Fig.4: Layers of the epidermis. Since we can see 5 layers, this skin is classified

as thick skin. This type of skin can be found in the palms and soles.

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Fig.5: Stratum basale of the epidermis. The deepest layer. The lightly stained

cells seen are melanocytes.

stratum

basale

Melanocytes

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stratum

spinosum

Fig.6: Stratum spinosum of the

epidermis. Thick layer. When

the tissue is prepared, the cells

of this layer will shrink; the

keratin tonofilaments will

produce spine-like structures

on the surface of these cells

(image below).

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Fig.7: Stratum granulosum and stratum lucidum of the epidermis. Cells of the

stratum granulosum characterized by the presence of several darkly stained

granules in the cytoplasm. Stratum lucidum is a lightly colored layer seen only

in thick skin.

Stratum

lucidum

Stratum

granulosum

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Fig.8: Stratum corneum of the epidermis. A thick layer, especially in thick skin.

The cells here have no nuclei or organelles. They are nothing more than cell

membranes filled with keratin fibers.

stratum

corneum

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Stratum

basale

Stratum corneum

Stratum

spinosum

Stratum

granulosum

Fig.9: In this image, only 4 layers are seen in the epidermis. Stratum lucidum is

not present. This skin is classified as thin skin.

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Fig.10: Thick skin.

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Fig.11: Thin skin.

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The Dermis (= Connective tissue)

Formed of two regions:

Papillary region:

• Superficial

• Correspond to dermal

papillae

• Formed of loose areolar

connective tissue

Reticular region:

• Deeper

• Formed of dense

irregular collagenous

connective tissue

Fig.12: The dermis and its regions.

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Sensory Receptors in the dermis

Fig.13: Left: Meissner’s corpuscle.

Elliptical structures found in dermal

papillae. Below: Pacinian (lamellated)

corpuscle. Onion shaped, formed of

concentric circles. Found in deep parts of

dermis.

Sweat

gland

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Fig.14: Hair shaft and root.

The Hair

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Medulla

Cortex – Cells

have darkly

stained dots

Cuticle – Thin

pinkish layer

Parts of

the hairDRS

ERS

Glassy

membrane

Fig.15: Cross section through the

hair root and follicle. The glassy

membrane is a thick red line

between the epithelial and dermal

root sheaths. ERS = epithelial

root sheath. DRS = dermal root

sheath.

Hair

follicle

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Fig.16: Identify parts of hair.

Identify parts of hair follicle.

Section through hair shaft or

root?

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Fig.17: Hair Bulb.

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Structures associated with the hair

Fig.18: Longitudinal section through hair. Note how the follicle is derived from

the epidermis.

Hair

follicle

Sebaceous

gland

Arrector pili

muscle

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Hair

follicleArrector pili

muscle

Sebaceous gland

Fig.19: Magnified view of the previous slide. Cells of the sebaceous glands appear

clear/white because their secretions (sebum) is rich in lipids which disappear during

tissue preparation. Arrector pili muscle is a smooth muscle attached to the dermal

root sheath.

• Cells appear clear

/ white

• Located in the

angle between the

hair follicle and

the arrector pili

muscle

Sweat gland

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Fig.20: Identify the hair

follicle and associated

structures.

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Fig.21: Previous slide magnified.