Human Anatomy & Physiology

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Week4-SkinCondensed.pptx

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Week 4: Skin

Jonathon Odom MS

Levels of Organization

Learning Objectives

Understand the key components of the epidermal layers and which regions they are associated with

Understand what makes fingerprints

Understand the difference in skin color and the contributing factors

Understand key components of the dermis

Understand key components of hypodermis

Understand hair distribution and anatomy

Understand what is produced by each type of sweat gland

Be familiar with the components of nails

Functions of the Integumentary System

Functions include

Protection

Excretion

Temperature regulation

Nutrient storage

Vitamin D3 synthesis

Sensory detection

Components of the Integumentary System

Cutaneous membrane

Epidermis

Dermis

Subcutaneous layer (also called superficial fascia or hypodermis)

Accessory structures

Hair

Nails

Glands

Functions of Epidermis

Provides mechanical protection

Prevents fluid loss – water resistant

Keeps microorganisms from invading the body

Gives each person unique skin color

Integument Organization and Structure

The skin can be divided into two main components, a thin superficial layer called the epidermis and a deeper thicker layer called the dermis. Each can be further divided into layers and structural components

Layers of the Epidermis (superficial to deep):

Stratum corneum

Stratum lucidum (found only in thick epidermis)

Stratum granulosum

Stratum spinosum

Stratum germinativum (basale)

Contains stem cells that replenish cells as

superficial layers slough off

http://www.physioweb.org/IMAGES/epidermis_mag.jpg

Remembering the order of the layers: “Can Lucy Get Some Gum?”

-Tell them to pay attention to superficial and deep! On the quiz, we may ask them to list the layers deep to superficial OR superficial to deep, so they should be prepared to list them either way.

-spinosum is keratin added to cells

Layers of the Epidermis

Thin vs Thick Skin

Thin (epidermis = 0.08 mm)

4 layers

Most of the body

Lips, scrotum & penis, eyelids exceptionally thin

Thick (epidermis = 0.5 mm)

5 layers

Palms of hands, soles of feet

Stratum corneum

Stratum granulosum

Stratum spinosum

Stratum germinativum (basale)

Stratum corneum

Stratum lucidum (found only in thick epidermis)

Stratum granulosum

Stratum spinosum

Stratum germinativum (basale)

Real-Quick-Review Multiple Choice

1. The stratum of epidermis found only in thick skin is the:

A) Stratum corneum

B) Stratum lucidum

C) Stratum granulosum

D) Stratum spinosum

E) Stratum germinativum

2. This stratum of epidermis contains stem cells that replenish cells as superficial layers slough off

A) Stratum corneum

B) Stratum lucidum

C) Stratum granulosum

D) Stratum spinosum

E) Stratum germinativum

B, Lucidum

E, Germinativum

Fingerprints

The epidermis is firmly attached to underlying dermis via egg-carton-like structures formed by

The epidermal ridges on the epidermis

The dermal papillae on the dermis

Fingerprints

The epidermis is secured to the dermis through a series of epidermal ridges and dermal papillae that act as a lock

Such structures are more prevalent in areas with high frictional stress such as the sole of the feet

Excessive friction may cause the two layers to separate, filling the space with interstitial fluid thus creating a blister

Epidermal ridges that extend into the stratum corneum are known as fingerprints and found in areas of extreme friction

Biological Function: increased grip

Skin Color

The base layer of the epidermis is the stratum germinativum. This layer contains special cells called melanocytes that dictate the color of our skin

Melanocytes produce melanin which absorbs UV radiation

Pale ivory skin=low melanocyte activity

Dark ebony= high melanocyte activity

For those who have low melanocyte activity, skin color is determined by two other factors:

Carotene: orange pigment

Dermal blood supply: rosy appearance

Melanocytes

Dark skin is the result of increased melanocyte activity not melanocyte number // the cells are just more active & produce more melanin

Pathologic Skin Color

Cyanosis: blue color, blue-lips, blue-fingertips, due to lack of blood supply

Jaundice: increased bilirubin, yellow skin appearance

Real-Quick-Review Fill-In-The-Blank

1. Melanocytes produce _________, which absorbs UV radiation

2. The orange pigment in skin is called _________

3. What is responsible for the rosy appearance skin can take on?

4. The 2 types of extracellular fibers in skin which provide strength and stretch are called

_________ and _________

Melanin

Carotene

Dermal blood supply

Collagen and Elastin

Epidermal Physiology

Protection:

Melanin – protects against excessive or intense UV radiation

Keratin – Keratinize the skin cells for protection

Nutrients:

Vitamin D3 (cholecalciferol) – Synthesized from UV radiation (sunlight)

Replacement:

Epidermal cells respond to epidermal growth factor (EGF)

Repair injury

Growth/differentiation

Secretions from glands

Components of the Integumentary System

Cutaneous membrane

Epidermis

Dermis

Subcutaneous layer (also called superficial fascia or hypodermis)

Accessory structures

Hair

Nails

Glands

Dermal Organization

Divided into two layers

Papillary layer

Areolar tissue

Contains blood and lymph vessels, lymph nodes and sensory nerves of epidermis

Reticular layer

Dense Irregular CT

Contains network of collagen and elastic fibers to resist tension

Dermis Organization and Structure

The dermis lies below the epidermis and contains many structures such as blood vessels, nerves, sensory receptors, extracellular fibers, hair follicles, and glands

Blood Vessels (arteries and veins) are divided by location:

Superficial

Deep

Lymph

Nerves interpret information from specialized sensory receptors:

Extracellular fibers

Collagen: strength

Elastin: stretch

http://classconnection.s3.amazonaws.com/49/flashcards/491049/jpg/f450061362111508057.jpg

For nervessometimes coming up with weird ways to remember their names helps (ie. if mice were running across your skin, your Meissner’s corpuscles would detect it; pacific ocean is really heavy, etc ;)

Dermal Innervation

Nerve Distribution & Function

Superficial

Free nerve ending- pain, temperature

Meissner’s corpuscles: light pressure

Merkel cells: soft touch or stroke

Deep:

Pacinian corpuscles: heavy pressure

Free nerve ending on hair follicle-motor control

Skin Elasticity

Elastin fibers allow the skin to stretch and then return to original shape & location

Collagen fibers (normally) prevent the skin from stretching too far

Elastin, Collagen and Water maintain skin properties called skin turgor

Dehydration causes a loss of skin turgor

Diagnosed by the pinch test

Stretching the skin beyond its limits causes damage called stretch marks

Components of the Integumentary System

Cutaneous membrane

Epidermis

Dermis

Subcutaneous layer (also called superficial fascia or hypodermis)

Accessory structures

Hair

Nails

Glands

The Hypodermis

The hypodermis is a connective tissue and not considered part of the integument though it lays adjacent to the dermis (hypo=below).

Content and distribution of areolar and adipose tissue, gives shapes the body giving each person a somewhat unique superficial appearance.

In comparison to the epidermis and dermis, the hypodermis is typically quite thick depending on the bodily location.

Superficial layers: high blood supply

Deep layers: low blood supply

Clinical Correlation: SubQ injection would be deep to this tissue

http://www.dartmouth.edu/~anatomy/Histo/lab_4/skin/DMS033/01.gif

Components of the Integumentary System

Cutaneous membrane

Epidermis

Dermis

Subcutaneous layer (also called superficial fascia or hypodermis)

Accessory structures

Hair

Nails

Glands

Anatomy of Hair

Structure and Function

Arrector pili muscle: nervous stimulation lifts the shaft, increasing skin sensitivity

Papilla: vascular structure that provides nutrients

Matrix: location of new hair growth

Sebaceous gland: coat hair with oily protectant

Shaft Layers (superficial to deep)

Cuticle-soft exterior made of dead cells

Cortex-hard interior for support

Medulla-middle most structure, center of hair shaft

Types of Hair

Vellus hairs (short & thin)

covers most of the body (vellus, think “all over us”)

Terminal hairs (long & thick)

head, eyebrows, eyelashes

pubic hair is a special terminal hair that’s generally thicker & more curly

Club hair (cessation of growth)

Forms when a hair stops growing

Shed and replaced with new hair according to hair growth cycle

Types of Hair

Vellus hairs (short & thin)

covers most of the body (vellus, think “all over us”)

Terminal hairs (long & thick)

head, eyebrows, eyelashes

pubic hair is a special terminal hair that’s generally thicker & more curly

Club hair (cessation of growth)

Forms when a hair stops growing

Shed and replaced with new hair according to hair growth cycle

Nails

Nails function to strengthen the distal portion of digits.

Structure and Function

Nail Matrix: mitotically active zone of nail growth

Lunula: newly formed and undifferentiated white cells of nail body

Eponychium: epidermal cells dragged forward along the body as the nail grows, otherwise known as the cuticle

Hyponychium: epidermal cells dragged beneath the body as the nail grows

Free edge of nail extends over hyponychium

http://www.lrn.org/Popup/Skin/figure4_4.html

They need to know 5-9 in their lab manual, which is similar to this image

Glands

Secretory glands are located in the dermis and empty onto the surface of the skin. There are four types found on the human body:

Sudoriferous Glands: produces watery secretion called sweat

Eccrine: found abundantly across the body and excrete mostly water

Apocrine: found in the armpits, groin, and surrounding the nipples, this gland produces a more concentrated secretion

Sebaceous Glands: produces oily secretion called sebum

Typically associated with hair follicles

Ceruminous Glands: produce waxy secretion called cerumen

Found exclusively in the ear

Mammary Glands: produce milk

Found in the breast but only active in pregnant and nursing women

Secretions function to cool, lubricate, and protect the skin.

They need to know the main types of glands and the subtypes and what they produce (so basically this whole slide…)

Real-Quick-Review Fill-In-The-Blank

1. Hair and nails are composed of a protein called _____________

2. Long, thick hair is called _________ hair; while short, thin hair is called __________ hair

3. The deepest shaft layer of hair is called the ___________

4. The newly formed and undifferentiated white cells of a nail body are called the _________

5. What type of gland produces the waxy secretion, called cerumen, found exclusively in the ear?

Keratin

Terminal, Vellus

Medulla

Lunula

Ceruminous