Skin

Where is the skin thickest and where thinnest

Thinnest : eyelids
Thickest : heels

What type of tissue is the epidermis?

Epithelial

Another name for hypodermis

Subcutaneous layer

What type of epithelium is the epidermis composed of?

Keratinized stratified squamous epithelium

Keratinocytes

Produce keratin

Melanocytes

Melanin

in the stratum basale

Langerhans cells

Immune responses, arise from red bone marrow

Merkel cells

Sensation to touch

Tactile Discs

Sensitive to pressure

Meissner’s corpuscle

Fine touch, low frequency vibration

Pacinian corpuscle

Pressure, high frequency vibration

Merkel cells

Pressure, position, sensation for shapes and edges

Name the cells of the epidermis

1. keratinocytes

2. Melanocytes

3. Langerhans cell

4. Merkel cell

Layers of the epidermis

Stratum basale (stratum germinativum)

Stratum spinosum

Stratum granulosum

Stratum lucidum

Stratum corneum

Stratum basale

deepest layer

cell division occurs here and it produces all the other layers

Stratum spinosum

layers of keratinocytes

Stratum granulosum

Includes keratohyalin and lamellar granules

Stratum lucidum

present only in thick skin

Stratum corneum

sublayers of flat, dead keratinocytes called corneocytes or squames

continuously shed

Dandruff

Keratinzed cells

What kind of tissue is the dermis composed of?

Connective tissue (collagen and elastic fibers)

Two regions of the dermis

Papillary and reticular

Papillary region

Areolar connective tissue, thin collagen and elastic fibers, dermal papillae, corpuscles of touch and free nerve endings

Reticular region

Dense irregular connective tissue , collagen and elastic fibers, adipose cells, hair follicles, nerves, sebaceous glands and sudoriferous glands

Epidermal ridges

form basis of fingerprints

function - increased firmness of grip by increasing friction

Carotene

yellow-orange pigment

found in the stratum corneum, dermis and hypodermis

How is melanin made?

through interaction with tyrosine present in melanocytes

What stimulates melanin production?

UV light

Solar elastosis (clumped elastin fibers)

from excessive UV light that can damage DNA

Where is carotene formed from?

Vitamin A

(orange tone in the skin)

Dark hair

melanin

Blond and red hair

melanin with Fe and SG

gray hair

loss of pigment

white hair

air bubbles in the medullary hair shaft

Lamellated corpuscles

In the hypodermis

detect external pressure applied to the skin

What does the hypodermis contain?

Adipose tissue and blood vessels

Which site is most common for injection?

hypodermis

What is the function of hairs?

1. protection

2. reduction of heat loss

3. sensing light touch

What is hair composed of ?

Dead, keratinized epidermal cells

Vellus hair

fine hair

Terminal hair

coarser hair

in the axilla pubic region

grow because of sex hromones

Hirsutism

excessive hairiness

Lanugo hair

very fine, soft hair

on foetuses or new-borns

Where does the blood supply nourish the hair?

At the papilla (in the bulb)

Arrector pili

smooth muscle

in the dermis

attached to the side of the hair shaft

the one that gives us “goose bumps”

Sebaceous (oil) glands

secret sebum which prevents dehydration of hair and skin, inhibits bacterial growth

connected and open to hair follicles

Sudoriferous (sweat) glands

Eccrine and Apocrine

Eccrine

help cool the body by evaporating and also eliminate small amounts of wastes

ducts empties on skin surface

Apocrine

In the axilla or groin, their excretory ducts open into hair follicles

causes body odor when bacteria break down

How does the whitehead of a pimple occur?

When the sebum and bacteria stay below the skin surface

How does the blackhead of a pimple occur?

When the sebum and bacteria partially open to the surface and turn black due to melanin

Ceruminous Glands

modified sweat glands located in the ear canal

produce earwax (cerumen) which provides a sticky barrier that prevents entry of foreign bodies into the ear canal

protects tympanic membrane

Nails

keratinized epidermal cells

Functions of the skin

1. regulates body temp

2. acts as a blood reservoir

3. protection

4. cutaneous sensations

5. excretion and absorption

6. synthesis of vit d

Where does the epidermis develop from?

Ectoderm

Where does the dermis develop from?

mesoderm

By what is the epidermis of the fetus protected?

Vernix caseosa

What happens to the Integumentary System when aging?

Wrinkling

decreased of skin’s immune responses

dehydration = cracking of skin

decreased sweet production

low on melanocytes so gray hair and weird skin pigmentation

loss of hypodermic fat

skin is thinner

higher risk of developing pathological conditions

less hair

nails grown slowly and are brittle