The Dermis and Accessory Structures - PowerPoint Presentation

Slide1

The Dermis and Accessory StructuresSlide2

Skin Pigment

The color of your skin is due to an interaction between:

(1) epidermal pigmentation

(2) dermal circulationSlide3

Epidermal Pigmentation

Two pigments present in the epidermis:

(1) Carotene – orange-yellow pigment found in the stratum

corneum

layer and in the fatty tissues in the dermis.

(2) Melanin – brown, yellow-brown, or black pigment produced by

melanocytesSlide4

Melanocytes

In individuals with pale skin, the

melanosomes

are destroyed in the lower layers of the epidermis, and the cells of the more superficial layers lose their pigmentation.

In individuals with dark skin, the

melanosomes

are larger and the

melanosomes

are destroyed in the stratum granulosum layer, making the pigment in the upper layers darker.

*

Melanocytes

produce the pigment melanin. Melanin is transferred up through the layers via vesicles called

melanosomes

until they are destroyed.Slide5

Melanocytes

Melanin pigment in your skin protects you from UV radiation. Long amount of UV radiation can damage DNA, causing mutations and promoting the development of cancer. In the

keratinocytes

, melanin is concentrated around the nucleus, thereby protecting your DNA from UV exposure.Slide6

Melanocytes

Although

melanocytes

increase their activity and pigment production when exposed to UV radiation, the response is not rapid enough to prevent sunburn the first day of constant exposure.

Melanocyte

activity peaks about 10 days after initial exposure.

Chronic exposure to UV radiation can result in premature wrinkling, leathery consistency to skin, and skin cancers.Slide7

Dermal Circulation

Blood contains red blood cells that contain the pigment hemoglobin, that binds and transports oxygen throughout the body. Hemoglobin is bright red. If blood vessels are dilated, the red tones seen in light colored individuals gives the skin a redder tone.

Cyanosis (blue skin) can occur due to a sudden drop in blood supply to the skin.Slide8

Epidermis and Vitamin D3

When exposed to small amounts of UV radiation, epidermal cells in the stratum

basale

and stratum

spinosum

convert a cholesterol-related steroid into vitamin D3 (

choleciferol

). The liver then converts

choleciferol into the hormone calcitriol, essential for the absorption of calcium and phosphorus by the small intestine. An inadequate supply of calcitriol leads to impaired bone maintenance and growth.Slide9

The Dermis

Two major components:

(1) a superficial dermal papillary layer

(2) a deeper reticular layerSlide10

Papillary Layer

Consists of

areolar

tissue, and contains capillaries and sensory neurons that supply the surface of the skin.Slide11

Reticular Layer

Found beneath the papillary layer and consists of dense irregular tissue.

Bundles of collagen fibers extend beyond the reticular layer into the hypodermis below.Slide12

Wrinkles and Stretch Marks

Although collagen fibers are strong and resist stretching, they are easily bent or twisted. Elastic fibers permit stretching but then return to their original length. Aging, hormones, and UV radiation exposure reduce the amount of

elastin

in the dermis, producing wrinkles and sagging skin.

Decreased skin

turgor

, and a

sign of dehydration.Slide13

Stretch Marks

Distortion of the dermis over the abdomen during pregnancy of after substantial weight gain can exceed the elastic capabilities of the skin. The resulting damage prevents it from recoiling to its original size after delivery or weight loss. The skin wrinkles/creases, creating stretch marks.Slide14

Lines of Cleavage

Most of the collagen and elastic fibers are arranged in parallel bundles. These bundles are aligned in different directions to resist applied forces. The pattern of arrangement of these bundles are called

lines of cleavage

.

These lines are significant, because a cut parallel to a cleavage line will remain closed, whereas a cut at right angles to the line will be pulled open.

Surgeons chose their incision lines based on the lines of cleavage.Slide15

Dermis Layer – Sensory Receptors

Contains many sensory receptors:

(1) sensitive to light touch (

Meissner’s

corpuscles) that are located in the dermal papillae

(2) receptors sensitive to deep pressure and vibration (

Pacinian

corpuscles)Slide16

Accessory Structures - Hair

Hairs are produced from organs called hair follicles.Slide17

Accessory Structures – Types of Hair

Lanugo

– extremely fine,

unpigmented

hairs that form after three months of embryonic development

Lanugo

is shed before birth and is replaced by:

(1)

Vellus hairs – fine peach fuzz located throughout the body. Puberty causes some vellus hairs to transition to terminal (airpit, groin, etc)(2) Terminal hairs – heavy, deeply pigmented, sometimes curly hairs (head hair, eyebrows, and eyelashes)Slide18
Slide19

Function of Hair

Head hair protects scalp from UV radiation and insulates the head

Nasal hairs prevent entry of foreign particles into airway (eyelashes perform same function for eyes)

A Root hair plexus of sensory nerves allows you to feel even slight movements of each hair shaftSlide20

Arrector

Pili

Ribbons of smooth muscle called

arrector

pili

muscles pull on the hair follicles and force the hair to stand erect.Slide21

Hair Growth Cycle

Hairs grow and shed based on hair growth cycle. A scalp hair grows for 2-5 years, at a rate of about 0.33 mm/day

Collections of hair can be useful to assay for:

(1) lead poisoning

(2) arsenic poisoning

(3) heavy metal poisoning

Healthy adults lose about 50 hairs/day from your head.

In males, changing sex hormone level can change terminal hair to

vellus hair, in a process called male pattern baldness.Slide22

Glands

Two types of exocrine glands:

(1) Sebaceous glands

(2) Sweat glands – consists of

apocrine

and

ecrine

glandsSlide23

Sebaceous Glands

Sebaceous glands are oil glands that discharge a waxy, oily secretion into hair follicles

Release sebum (lipids) that inhibit bacterial growth, lubricate keratin (hair/nails), and condition the skinSlide24

Sebaceous Glands

During the last months of fetal development, the sebaceous glands are extremely active and produce secretions to form a protective layer called the

vernix

casoeseaSlide25

Apocrine

Sweat Glands

Located in the armpits, around the nipples, and in the groin attached to hairs

Produce sticky, cloudy, sometimes odorous secretions

The sweat is a nutrient source for bacteria, which intensify the odor

Begin secreting at pubertySlide26

Merocrine

/Ecrine

Sweat Glands

More numerous and widely dispersed than sebaceous glands

Palms and soles have greatest number

Discharge secretions directly onto skinSlide27

Function to:

1. Cool the skin through evaporative cooling

2. Excrete water and electrolytes3. Provide protection to environmental hazards, by diluting harmful chemicals and discouraging growth of bacteria

Merocrine

/

Ecrine

Sweat GlandsSlide28

Ceruminous

Glands

Modified sweat glands in the passageway of the external ear canal

Secretions are called

cerumen

, or earwax

Works along with tiny hairs to trap foreign particles and prevent them from reaching the eardrumSlide29

Nails

Form on the dorsal surfaces of fingers and toes

Function to protect exposed tips of fingers and toes, and limit their distortion when subjected to mechanical stress, like grabbing objectsSlide30

Nails

Nail production occurs at the nail root

Underlying blood vessels provide nail its color

Small white/pale colored moon called the

lunula

found at the base of the nailSlide31

Nails –

Indication of Health

Can be used to indicate general overall health of an individual

EX: yellow nails in individuals with chronic respiratory disorders, thyroid disorders, or AIDS

Pitted nails as a result of psoriasis

Concave nails as a result of some blood disorders