Anatomy Chapter 4

Functions of Integumentary System

1. Protects deeper tissues

2. Aids in heat relocation

3. Aids in excretion of urea and uric acid

4. Synthesizes Vitamin D

Types of damage to the integument

1. Mechanical damage

2. Chemical damage

3. Bacterial damage

4. Thermal damage

5. UV Radiation

6. Desiccation

Development of skin

develops where superficial ectoderm and mesoderm meet

Surface ectoderm becomes the

epidermis

mesoderm becomes the

dermis and hypodermis

Each pair of somites

provides the tissue for its own segment of the skin

CT found in skin

1. Areolar CT

2. Dense Irregular CT

3. Adipose

Epidermis

1. stratified squamous

2. 4-5 layers

Dermis

Papillary layer of areolar ct and reticular layer of dense irregular ct

Hypodermis

Adipose Tissue

Epidermal Cell types

1. Keratinocytes

2. Melanocytes

3. Langerhans cells

4. Merkel cells

Keratinocytes

Produce keratin and provide protection

Melanocytes

produce melanin

Langerhan Cells

Form from bone marrow and part of the immune response

Merkel Cells

Contact sensory neurons and form tactile receptors

Keratinocyte life cycle

1. Stem cells divide at basal lamina

2. They push towards the suface

3. fill with keratin and oils

4. Slowly die

Keratinocyte life cycle span

15-30 days

Layers of Epidermis

1. stratum basale

2. stratum spinosum

3. stratum granulosum

4. stratum lucidum

5. stratum corneum

Stratum basale

1. single layer of stem cells, melanocytes, and Merkel cells

2. Keratinocytes reproduce here

Stratum spinosum

1. Several cells thick of keratinocytes, melanocytes, and langerhans

2. Tonofibrils develop to support cells

Stratum granulosum

1. keratin is produced and forms dark staining keratin granules

2. High lipid production makes cells water resistant but kills the cells

Stratum Lucidum

1. only found in thick skin

2. doesn't stain well

3. several layers of flat parallel keratin filaments

stratum corneum

1. Flat, dead, dry cells with no organelles

2. Thickest layer

Thick Skin

Has 30 layers of stratum corner and all 5 epidermal layers

Location of thick skin

Palmer and plantar surfaces

Thin Skin

Has fewer layers of the stratum corner and no stratum lucidity

Papillary layer

Areolar CT penetrated by capillaries and neurons

Sub papillary plexus

capillary network from small arteries in papillary layer

Dermal Papillae

1. Projections of superficial dermis

2. Often have touch receptors and capillaries

Dermal papillae in thin skin

small pegs

Dermal papillae in thick skin

large whorls resulting in finger prints

Reticular Layer

Dense irregular CT with bundles of collagen and elastic fibers

Reticular Layer characteristics

1. glands and hairs penetrate into this layer

2. deep touch receptors

3. Blood received from the cutaneous plexus

Tension Lines

Dermal protein fibers are arranged in semi parallel bundles that differ throughout the skin

Characteristics of Tension Lines

1. Resist tension best in those directions

2. Surgeons try to cut along them

3. Unprepared damage to the due to hormones or UV can result in wrinkles

Stretching of the skin may cause tension lines to separate and break resulting in

scar tissue filling the space and forming stretch marks

Hypodermis (subcutaneous layer)

Consists of areolar and adipose CT

Hypodermis characteristics

1. No distinct boundaries with dermis

2. adipose acts as an insulator

3. houses major blood vessels and nerves

Melanin

1. Melanocytes release vesicles called melanosomes into keratinocytes

2. everyone has same amount

Melanin production

1. UV light increases local melanin production

2. UV converts a steroid in the skin into Vitamin D

3. Too much UV can damage fibrocytes and mutate DNA

Other skin pigments

1. Carotene

2. Hemoglobin

Carotene

yellow orange pigment found in the epidermis, hypodermis, and carrots

Hemoglobin

Red oxygen carry pigment in blood cells that cause pinkness in the skin if no other pigments are present

Race

Often based on skin pigmentation, hair, and facial features

Accessory structure development

As the ectoderm develops into the epidermis, small areas of epidermal tissue grows into the future dermis

Epithelial columns

cords of epidermal cells that grow into the dermis

Hair and glands from from

epithelial columns

Functions of Hair

1. Protection

2. Reduction of Heat Loss

3. Sensing light touch

Hair

A stalk of keratinized dead epithelial cells

Location of Hair

1. About 5 million

2. All surfaces except plantar/palmer surfaces, digits, lips, eyelids, and external genitalia

Vellus Hair

Peach fuzz

Terminal Hair

Thicker with darker pigment

Hair Follicle

1. extends deep into dermis

2. consists of epithelial and CT sheaths

Hair matrix

Base of follicle that grows the hair

Hair papilla

Provides blood and sensation to the hair follicle

Cuticle

Outermost layer of hair

Cortex

Middle layer of hair

Medulla

Innermost layer of hair

Root Hair Plexus

Sensory neuron surrounding follicle that detects hair movement

Arrector Pili

Smooth muscle that moves hair

Bulb of Hair

part at base of follicle

Root of Hair

Lower region of the hair attached to the bulb

Shaft of Hair

the portion where the skin separates from the hair

Hair replacement

1. Every 2-5 years

2. Follicle undergoes regression and detaches

3. Follicle then reactivates and grows a new hair

Sebaceous Gland

oil-secreting gland in the dermis that is associated with hair follicles (holocrine)

Sebum

An oily lipid compound that decreases evaporation and bacterial growth

Simple Alveolar Gland

A gland that is shaped like a flask and does not branch

Characteristics of Simple Alveolar gland

1. holocrine secretion

2. Short duct

3. typically associated with a hair follicle

Without a hair the gland is called a

sebaceous follicle

Eccrine Sweat Glands

Coiled tubular simple gland

Eccrine Sweat Gland Characteristics

1. Use merocrine secretion

2. Not associated with hair follicle

3. On most body surfaces especially palm

4. Active at birth

5. secrete perspiration

Perspiration of eccrine sweat glands

1. Water NaCl and Urea

2. Function in cooling, excretion, and protection

Apocrine Sweat Glands

Coiled, tubular, simple gland

Characteristics of Apocrine Sweat Glands

1. Use merocrine secretion

2. associated with hair follicle

3. active at puberty

Location of apocrine sweat glands

Axilla, groin, and nipple region

Secretion of Apocrine Sweat glands

thick, cloudy, and viscous secretion that functions in lubricating, cooling, and possible pheromones

Modified Apocrine Sweat Glands

Mammary and Ceruminous Glands

Mammary Glands

Under the nipple and secretes milk

Ceruminous Glands

1. External ear

2. secretes cerement that mixes with sebum and dead cells to create ear wax

Function of ear wax

traps particles and keeps out water

Nails

keratinized plate of epithelium growing from distal digits

Functions of nails

1. protects and supports tips of digits

2. Helps manipulate environment

Nail Body

Keratinized plate

Nail bed

Surface of the skin covered by nail body

Nail root

Source of nail production

Lunula

White half moon region at the base of the nail plate due to obscured blood vessels

Burn

Tissue damage and cell death caused by heat, electricity, UV radiation or chemicals

Associated dangers of burns

dehydration, electrolyte imbalance, circulatory shock

1st degree burn

Skin is red and swollen, only epidermis damaged

2nd degree burn

Skin red with blisters, epidermis and upper dermis damaged

3rd degree burn

Gray- white or black, destroys entire layer