3bio 261 skin lecture_sp 2011

7/28/2019 3BIO 261 Skin Lecture_SP 2011

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Skin(IntegumentarySystem)

PLEASE NOTE: Only images surrounded by a thick black

border in the following lecture slides will be included on

Practical 1. The skin model at the end of this lecture

series is also fair game for P1.

APR 3.0 Module 4. Integumentary

Histology & Dissection Sections


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Skin (Integument) Outer covering of the body

Largest organ of the body An organ is a group of

tissues that work together

and have specific functions.

Functions of the skin:

Protection = Barrieragainst drying, bacteria,

UV light, water, physical

abuse

Temperature regulation

Sensory perception

Excretory organ

Formation of vitamin D


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Consists of three major

regions:

1. Epidermis

Outermost

superficial region

2. Dermis

Middle region

3. Hypodermis

(Subcutaneous) Deepest region

Skin (Integument)

APR 3.0 Module 4. Integumentary (Dissection)Topic: Thin skin and subcutaneous tissues View: Layers

1

2 31

2 3


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Layers of Skin


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Epidermis Keratinized stratified

squamous epithelium ofvariable thickness

Avascular

Thick skinhas fivelayers (superficial todeep):

1. Stratum corneum2. Stratum lucidum

3. Stratum granulosum

4. Stratum spinosum

5. Stratum basale

Thin skinhas four layers(stratum lucidum ismissing)

Cells of stratum lucidumand stratum corneum lacknuclei


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Thick Skin High Magnification

SC = Stratum Corneum

SL = Stratum Lucidum

SG = Stratum GranulosumSS = Stratum Spinosum

SB = Stratum Basale

P = Papillary Layer of Dermis

SC

SL

SS

PP

SG

SB


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Thin Skin High Magnification

SC = Stratum CorneumSG = Stratum Granulosum

SS = Stratum Spinosum

SB = Stratum Basale

SC

SB

SSSG


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Stratum Corneum

Description:

Outermost layer of epidermis Up to 30 layers of cornified, dead cells

Dead cells contain keratin

Functions:

Creates barrier to fluids = waterproofing

Protection from abrasion and penetration, wear

and drying

Rendering the body relatively insensitive to

biological, chemical, and physical assaults

Cells sloughed (shed) from surface and continually

replaced from deeper layers


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In epidermis, between stratumgranulosum and stratum corneum

Present onlyin skin of palm (hand)and sole (foot) = THICK SKIN

Description:

Thin translucent layer composed of three

to five layers of keratinocytes withoutnuclei or organelles (clear layer)

Stratum Lucidum


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Above this layer, the capillaries in the

dermis can not supply the cells resulting

in cell death

Description:

Three to five layers of flattened

keratinocytes

Keratinocytes contain dark staining

keratohyalin granules (precursor of keratin)

Keratohyalin granules release a protein that binds

keratin filaments together into coarse, tough

bundles

Nuclei of keratinocytes in various stages of

degeneration

Stratum Granulosum


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Histological fixatives shrink keratinocytes so theypull away from each other; they remain attached

at desmosomes giving shrunken cells appearance

of porcupines attached to their neighbors = spiny

cells

Description:

Many layers of keratinocytes

Deepest cells can divide

Cells firmly attached to each other by

desmosomes (cell junctions)

Stratum Spinosum


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Deepest layer of epidermis firmly attached to dermis

Description:

Single layer of columnar or high cuboidal cells

resting on basement membrane

Keratinocyte is predominant cell

Also contains melanocytes, and stem cells

Skin color - the more active the melanocytesthe darker the skin

Stem cells produce keratinocytes and melanocytesvia mitosis.

All new epidermal cells are formed in this layer!!!

Stratum Basale (Basal Layer)


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Cells of Epidermis

Keratinocytes: Most abundant cell type in epidermis (90% of cells)

Produce keratin and arise from stratum basale every 20-45 days

Melanocytes:

Produce melanin pigment

Have long, branching cytoplasmic processes and are scattered among the keratinocytes within

stratum basale

Processes continually shed melanin-containing fragments from their tips

Keratinocytes phagocytize these fragments and accumulate melanin granules on the sunny

side of the nucleus. This shields the DNA within the nucleus from UV radiation.


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Dermis

Second major skin regioncontaining strong, flexibleconnective tissue

Composed of two layers

1. Papillary layercomposed of areolar(loose) connectivetissue

2. Reticular layercomposed of dense

irregular connectivetissue

Papillary

Layer

Reticular

Layer


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Relationship between epidermis and dermis


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Thick Skin Low Magnification

R = Reticular Layer of dermis

P = Papillary Layer of dermis

Epidermis

Dermis

R

P P


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Papillary Layer (Dermal Papilla)

Location:

Interface between dermis andepidermis

Description: Projection of papillary (external)

layer of dermis

Forms core of epidermal ridge Numerous and often branched

Contains capillary loops

Function: Provides nourishment to avascular

epidermis

APR 3.0 Module 4. Integumentary (Histology)

Topic: Thick skin View: LM: Low Magnification


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Reticular Layer Deep layer of dermis composed of

dense irregular connective tissue

Dense concentration of collagen and

elastin gives skin strength

Elastic fibers provide stretch-recoil

properties

Cleavage lines in this layer produce the

visible lines in our skin (Langers lines)

Cuts heal faster when the incision is

made parallel

Flexure lines create the folds in our

skin. Tears in this layer lead to stretch marks

APR 3.0 Module 4. Integumentary (Histology)

Topic: Thick skin View: LM: Low Magnification

Reticular Layer


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Hypodermis (Subcutaneous layer)

Not a part of the skin, but connectsskin to the muscles which liebeneath

Composed of areolar (loose)connective tissue and adipose tissue

Functions: Absorbs shock

Prevents heat loss from body;insulates the deep bodystructures

Common site of drug injectionbecause extensive vascularnetwork allows for rapidabsorption

Sub Q


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Summary of Skin Layers

f h k


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Burns of the Skin Partial-Thickness

First-degree Only the epidermis is damaged

Symptoms include localizedredness, swelling, and pain

Heals in 2 3 days = sunburn

Second-degree Epidermis and upper regions of

dermis are damaged

Symptoms mimic first degreeburns, but BLISTERS alsoappear; healing in 3 4 weeks

Full-Thickness = Third-degree

Entire thickness of the skin is

damaged

Burned area appears gray-white,cherry red, or black;

There is no initial edema or pain

(since nerve endings are destroyed)

Heals from the edges inward

Fluid loss is great, grafting often

necessary in larger burns


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Rule of Nines

Estimates the severity of burns

Burns considered critical if:

Over 25% of the body has second-degree

burns

Over 10% of the body has third-degree

burns

There are third-degree burns on face,

hands, or feet

Different areas of the body are calculated

as specific percentages (see figure)


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Appendages of the Skin


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Sweat Glands Different types prevent overheating of the body, secrete cerumen, and secrete

milk

Eccrine/Merocrine sweat glands found in palms, soles of the feet, andforehead. This sweat is water-like

Apocrine sweat glands found in axillary and genital areas. This sweatcontains fat and protein leading to body odor

Ceruminous glands modified apocrine glands in external ear canal thatsecrete cerumen (ear wax)

Mammary glands specialized apocrine glands that secrete milk.


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Merocrine Sweat Gland Low Magnification

SwG = Sweat Gland

SD = Sweat Gland Duct

SD

SwG


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Sebaceous Glands

Simple alveolar (holocrine) -secrete sebum (oil)

Most commonly found on face,

neck and trunk

Not present on palms or soles

Function - softens and lubricates

hair & skin bactericidal

Controlled by hormones

androgens; become activeduring puberty


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Sebaceous Gland Low Magnification

AP = Arrector Pili

SeG = Sebaceous Gland

AP

AP

AP

SeG


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Summary of Glands of Skin

H i & H i F lli l


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Hair & Hair Follicle Shaft = superficial portion of hair; above epidermis

Root sheathextending from the epidermal surface into the dermis (epidermal cells)

Deep end is expanded forming a hair bulb (location of active production of hair)

Hair Papilla= indentation of hair bulb containing blood vessels A knot of sensory nerve endings (a root hairplexus) wraps around each hair bulb Bending a hair stimulates these endings, hence our hairs act as sensitive touch receptors

Arrector pili- bundle of smooth muscle cells, makes hair stand on end, goose bumps, fear,insulation purposes, sympathetic nervous system


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Hair Follicle Medium Magnification

H = Hair

HB = Hair Bulb

HB

H


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Summary of Hair

S R i Ski


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Sensory Receptors in Skin Meissners (Tactile)corpuscle - superficial part of dermis (dermal papillae); touch,

tickle

Pacinian (Lamellated) corpuscle - larger and deeper in dermis/hypodermis; pressure Bare nerve endings (Afferent nerve endings)- pain sensation, heat and cold are also

perceived here.

ki d l i b


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Skin Model in Lab - KeyE = Epidermis

D = Dermis

H = HypodermisSeG = Sebaceous Gland

AP = Arrector Pili

HF = Hair Follicle

A = Adipose

SB = Stratum BasaleSD = Sweat Gland Duct

SwG = Sweat Gland

BV = Blood Vessels

HP = Hair Papilla

HB = Hair BulbSC = Stratum Corneum

M= Meissners Corpuscle

P = Pacinian Corpuscle

This model ill be part of P1

3bio 261 skin lecture_sp 2011

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