Lecture #5: Integumentary System

Structure of the Skin

1. Epidermis

2. Dermis

3. Hypodermis (Subcutaneous fat)

Epidermis

• Keratinized Stratified Squamous

• Thick or thin skin

Dermis layers

1. Papillary layer

2. Reticular layer

Papillary Layer

• Superficial layer of dermis

• Blood vessels for nutrients and temperature

• Areolar C.T.

Reticular Layer

• Dense Irregular C.T.

Hypodermis

• Not part of the skin

• Adipose C.T. (Subcutaneous fat)

Epidermal Cells

1. Stem Cells

2. Keratinocytes

3. Dendritic (Langerhans) Cells

4. Melanocytes

5. Merkel Cells

Stem Cells

• Where every cell came from

• Keratinocytes

Keratinocytes

• 90% of epidermal cells

• Produce protein keratin

Keratin

Protein that helps protect the skin

Lamellar Granules

• Lipid rich

• Acts as a water-repellent

Melanocytes

• 8% of epidermal cells

• Synthesizes pigment melanin

Melanin

• Tan-brown-black pigment

• Absorbs UV light

Dendritic (Langerhans) Cells

• Immune response

• Macrophage cause phagocytosis (eating cells)

Merkel Cells

• Touch receptors that work together with nerve cells

• Touch sensations

Epidermal Skin Categories

1. Thin

2. Thick

Thin Skin

• Throughout the body

• 22 ft²

• Largest organ

• 16% body weight

Thick Skin

• Palms and soles

• Has sweat glands but no sebaceous glands

• Sebum (Natural oils)

• Epidermis thicker

Epidermis Layers

1. Stratum Basale

2. Stratum Spinosum

3. Stratum Granulosum

4. Stratum Lucidum

5. Stratum Corneum

How long does cells go from stratum basale to dead tissue

4 weeks

Stratum Basale

• Single layer

• Deepest layer

• Lot of stem cells, some melanocytes and merkel cells

Stratum Spinosum

• 8-10 layers

• Superficial to Basale

• Keratinocytes close to each other

• Some dendritic

Stratum Granulosum

• 3-5 layers

• Keratinocytes going through apoptosis

• Granular keratinocytes

Stratum Lucidum

• Present in thick skin

• 3-5 layers

• Dead Keratinocytes

Stratum Corneum

• Most superficial skin

• 25-30 layers

• Dead Keratinocytes

Callus

Abnormal thickening of the stratum corneum

Keratinization

Keratinocytes going up, more keratin

Layers of Dermis

1. Papillary Layer

2. Reticular Layer

Papillary Layer

• Areolar C.T.

• Dermal Papillae

• Epidermal ridges on fingerprints

Meissner Corpuscles

Nerve endings, touch receptors

Free Nerve Endings

Sensations of warmth, pain, itching

Reticular Layer

Made of dense irregular C.T.

Pacinian Corpuscles

Deep pressure receptors

Subcutaneous Layer

• Fats

• Pacinian Corpuscles

• Large Blood vessels

Melanin

Beige to tan to black color

Dark-Skinned

More melanin

Light-Skinned

Less melanin

Carotene

• Yellow-orange pigment

• Found in stratum corneum, fatty areas of dermis, subcutaneous

Vitamin A

• Synthesize pigments

• Vision

Abnormal Skin Colors

1. Pallor

2. Cyanosis

3. Jaundice

Pallor

• White

• Decrease blood flow

Cyanosis

• Bluish

• Airway obstruction and lung disease

Jaundice

• Yellowish

• Bilirubin

• Cancer/hepa

Skin Color Disorders

1. Albinism

2. Vitiligo

Al

Albinism

Inability to produce melanin

Vitiligo

Depigmentation resulting in lighter patches

Parts of the Hair (Pili)

1. Shaft

2. Root

3. Bulb

Shaft

Superficial portion we can see

Root

Below surface of the skin, penetrates to dermis and subcutaneous

Bulb

• Matrix (mitotically active cells)

• Papilla (blood vessels)

Arrector Pili (Piloerector Muscle)

• Muscle attached to hair follicle

• Produce goosebumps

Glands

1. Sebaceous

2. Sudoriferous

3. Modified (ceruminous & mammary)

Sebaceous Glands

Oil glands

Sebum

Oily substance keeps hair drying out

Sudoriferous Glands

Sweat glands E

Eccrine Sweat Glands (Merocrine)

Most common, throughout skin

Apocrine Sweat Glands

• Axilla, groin, areolae of breasts, beards

• Begins to function in puberty

Ceruminous Glands

• Ear canal

• Cerumen (earwax)

Mammary Glands

Breast (produces milk)