5 - Integument

Integumentary System

the largest system of the body

The Integument is how much % of body weight?

16%

How much area is the Integument?

1.5 to 2 m²

The integument is made up of two parts

1. Cutaneous membrane (skin)

2. Accessory structures

What are the parts of the Cutaneous Membrane?

1. Epidermis (superficial)

2. Dermis (deep to epidermis)

Epidermis (superficial) consists of

Epithelial tissues (ectoderm)

Dermis (deep to epidermis) consists of

Connective tissues (mesoderm)

Superficial = papillary layer

Deep = reticular layer

Hypodermis (Superficial Fascia or Subcutaneous Layer)

Loose connective tissue

Deep to dermis

Accessory Structures to the Integumentary System

Hair

Nails

Exocrine glands

Where do accessory structures to the Integumentary System originate in?

the dermis and extend through epidermis

Functions of integument

Protection

Thermoregulation

Immune defense

Protection of the integument system

Acts as a Physical and Chemical barrier

Protects against UV via melanin

Secretion

The integument acts as a

Physical and Chemical barrier

The integument acts as protection against

UV via melanin

Thermoregulation of the integument system

Blood flow and sweat

Immune defense of the integument system consists of

dendritic cells

Functions of integument system

Water resistance

Metabolic regulation

Storage

Sensory

Water resistance involves the

production of keratin

Metabolic regulation involves

vitamin D3 production

Integument system consists of storage of

lipids

Integument system consists of sensory of

Touch, Pressure, Pain, Temperature

What are cells of the Epidermis

stratified squamous epithelium

stratified squamous epithelium

Avascular - nutrients and oxygen diffuse from the dermis

What do keratinocytes Produce/Contain?

large amounts of keratin

What are keratinocytes?

most abundant cells in the epidermis

Other Specialized Cells close to basement membrane

Melanocytes

Dendritic (Langerhans) cells

Merkel cells

Melanocytes produce

melanin

Dendritic (Langerhans) cells are part of the

immune system

Merkel cells are part of the

nervous system

Merkel cells react to

touch/pressure

Epidermis is divided into 2 skins

Thin skin

Thick skin

Thin skin

Covers most of the body

four layers of keratinocytes

Thick Skin

Covers the palms of the hands and soles of the feet

five layers of keratinocytes

“hairless'“ skin

The five strata of keratinocytes

From basal lamina (deep) to free surface (superficial)

1. Stratum basale

2. Stratum spinosum

3. Stratum granulosum

4. Stratum lucidum*

5. Stratum corneum

What is the most superficial strata?

Stratum corneum

What is the 2nd most superficial strata?

Stratum lucidum

What is the 3rd strata?

Stratum granulosum

What is the 2nd most deep strata?

Stratum spinosum

What is the most deep strata?

Stratum basale

Stratum Basale consist of

Epidermal ridges (form fingerprints)

Dermal papillae

Stratum Basale

not smooth/flat (wavy)

adds surface area to connections

Dermal papillae

Strengthen attachment between epidermis and dermis

The Stratum Basale has many basal cells

germinative cells (mitosis begins)

The Stratum Basale also contains

Melanocytes

Stratum Spinosum

“spiny layer”

Eight to ten layers of keratinocytes in the stratum spinosum are bound by

desmosomes

In the stratum spinosum cells shrink

cytoskeletons stick out (spiny)

When cells continue to divide in the stratum spinosum, the thickness of the epithelium _________

increases

The stratum spinosum contains what kind of cells?

Dendritic cells

Stratum Granulosum

“grainy layer”

The Stratum Granulosum is where cells

stop dividing

The Stratum Granulosum starts producing

Keratin

Keratohyalin

Keratohyalin forms:

Dense granules

Cross-link keratin fibers

The Stratum Granulosum is the layer where

Eventually cells die

Stratum Lucidum

“clear layer”

Stratum Lucidum is found only in what skin?

thick skin

Stratum Lucidum covers the

stratum granulosum

Stratum Lucidum contains

3-5 layers of dead keratinocytes

Stratum Corneum

“horn layer”

The Stratum Corneum is the

exposed surface of skin

The Stratum Corneum contains

15 to 30 layers of dead keratinized cells

The Stratum Corneum is resistant to what?

water

The Stratum Corneum sheds and replaces itself every:

2 weeks

What is keratinization (cornification)?

formation of a layer of dead, protective cells filled with keratin

Where does Keratinization occur?

on all exposed skin surfaces except eyes

Keratinization takes how many days from the stratum basale to the stratum corneum?

15–30 days

Skin Color is Influenced by Two Pigments

Carotene

Melanin

Carotene pigment color:

yellowish/brown (Orange-yellow pigment)

Melanin pigment color:

brownish/black (Yellow-brown or black pigment)

Blood circulation (red blood cells)

Hemoglobin

What does Hemoglobin contributes to?

red color

Where is Carotene found?

orange vegetables

Carotene is nonpolar

hydrophobic; interact with lipids/dissolve in lipids

Carotene gets converted into

vitamin A

vitamin A acts in the

Maintenance of epithelia

Photoreceptor pigments

What is melanin produced by?

melanocytes in stratum basale

Where is melanin stored?

in vesicles - melanosomes

Keratinocytes incorporate melanosomes by

endocytosis

Keratinocytes eat melanin/incorporate it into cells; this leads to melanin getting packed together

develops a dark ring/layer and absorbs UV radiation, which gets absorbed into dead cells

Function of Melanocytes

Melanin protects skin from sun damage

Ultraviolet (UV) radiation

Skin color depends on melanin production, not number of melanocytes

What does Melanin protects skin from?

sun damage

Ultraviolet (UV) radiation causes

DNA mutations and burns that lead to cancer and wrinkles

Skin color depends on

melanin production, not number of melanocytes

(all skin has the same number of melanocytes)

Blood contributes to skin color

Erythema

Cyanosis

Pallor

Hematoma

Hemoglobin is a

red pigment

Erythema

increased blood flow in the dermis

Blush/Flush, reddish

Cyanosis

low oxygenated blood; bluish tint due to light reflecting off it

Pallor leads to

Pale, low blood flow to skin

Pallor indicates

reduced blood flow

Hematoma

Bruising, black->blue->green->yellow

What is jaundice caused by?

bilirubin buildup when body breaks down RBC

Jaundice

Yellow, first in the eyes

Pituitary tumor

Excess MSH (melanocyte stimulating hormone)

Addison’s disease

bronzing (tanning of the skin)

Vitiligo

Autoimmune destruction of melanocytes

Melasma etc.

“Mask of pregnancy”

Albinism

Lack of melanin production

UV Damage can cause

actinic keratosis

What is actinic keratosis?

scaley sun damaged areas

Skin cancers

Basal cell carcinoma – #1

Squamous cell carcinoma - #2

Malignant melanoma