The Integumentary System: Skin Structure and Superficial Fascia

THE INTEGUMENTARY SYSTEM

B M 5 R 5 Dr Valeriano Vinci

WHY DO WE CALL IT "SYSTEM"?

Skin forms the entire external body covering and consists of different tissues, joined to perform specific functions

Facts about Skin

• Weight 12-15% of total body weight
• surface = 1.5-2m2
• 1 cm2 has 70 cm blood vessels, 55 cm nerves, 100 sweat glands, 15 oil glands, 230 sensory receptors

Skin turnover: 25-45 days

AN ORGANIZED GROUP OF TISSUE THAT FORMS A PA

Hair shaft Pore of sweat gland duct Epidermis Arrector pili muscle - Dermis Hair follicle Sebaceous (oil) gland - Hypodermis Hair root Hair follicle receptor Eccrine sweat gland Pacinian corpuscle Adipose tissue Sensory nerve fiber Cutaneous vascular plexus

Sawrosi tuberosa (adenomi sebeon] Clinica Dermatologica - UNINA "Federico II" Dermatology OFRESEARCH www.visualdx.com ( Logical Images, Inc

SKIN FUNCTIONS

1- Protection

• physical barrier that protects underlying tissues from injury, UV light and bacterial invasion.
• mechanical barriers part non specific immunity (skin, tears and saliva).
• prevent water loss.

2- Regulation of body temperature

• hypothalamus reacts to afferent stimuli from the skin
• In case of high temperature or strenuous exercise sweat is evaporated from the skin surface to cool it down.
• vasodilation and vasoconstriction regulate body temperature.

3-Sensation

• nerve endings and receptor cells that detect stimuli to temperature, pain and pressure.

4- Excretion

• sweat removes water and small amounts of salt, uric acid and ammonia from the body surface

5- Blood reservoir

• dermis houses an extensive network of blood vessels carrying 8-10% of total blood flow in a resting adult.

6- Synthesis of Vitamin D (cholecalciferol)

• UV rays in sunlight stimulate the production of Vit. D. Enzymes in the kidney and liver modify and convert to final form; calcitriol (most active form of Vit. D.) aids in absorption of calcium from foods and is considered a hormone.

SKIN STRUCTURE

The human skin (integument) is composed of at least two major layers of tissue: the epidermis and dermis.

Layers Of The Skin

Epidermis

Protects underlying tissue from infection, dehydration, chemicals, and mechanical stress.

Dermis

Contains tough connective tissue as well as different types of cells and glands.

Subcutaneous tissue

Made up of fat and connective tissue, this layer plays many important roles in your body.

Superficial Burn Classification

Epidermis Dermis Subcutaneous tissue CHistirwina, Incorporadid

Superficial Partial-Thickness Burn

Epidermis Dermis Subcutaneous tissue

Full-Thickness Burn

Epidermis Dermis Cheattivive, Incorporates Subcutaneous tissue Healthwise, Incorporated

BURNS

FIRST DEGREE BURN

EPIDERMIS

SECOND DEGREE BURN

DERMIS-

THIRD DEGREE BURN

HYPODERMIS 1 06

EPIDERMIS: KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM WITH FOUR DISTINCT CELL TYPES AND FIVE DISTINCT LAYERS

Dead cells flaking off at the skin surface Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale Dermis

THE DERMIS

Flexible and strong connective tissue -cells: fibroblasts, macrophages (WBC), mast cells (histamine). - fibers: Collagen - provide tensile strength Elastin - provide for restoration of shape after a deformation - oil and sweat glands origin - nerves, blood and lymphatic vessels

THE DERMIS LAYERS

Hair Dermal papillae Capillary loop of papillary plexus Papillary plexus Papillary layer Reticular layer Cutaneous plexus

Papillary layer:

Loose connective tissue with nipple like surface projection called dermal papilla. provides epidermis: -mechanical anchorage -metabolic support -trophic maintenance Dermo-epidermal innction Epithelial cells Hemidesmosome C Keratin intermediate filament Cytoplasmic plaque (BPAG 1, plectin) Transmembrane anchoring proteins (c64 integrin, collagen XVII/BPAG 2) -Lamina lucida Plasma membrane - Basal lamina -Lamina densa Basal lamina, lamina densa (laminins 1 and 5, collagen IV) Collagen fibril of dermis (collagen III) -Reticular lamina Anchoring fibrils (collagen VII)

Reticular layer:

Merges with the deep aspect of papillary layer and is composed of dense irregular connective tissue - bundles of collagen fibers are thicker - elastic fibers are well represented - orientation of fibers is related to local mechanical forces (skin lines) - include appendages , nerves and vessels

Subcapillary neural Opening (poie) of sweat duet Shat of hair Swort duct Subpspillery vascular Friction ridge Dorral papilas Epidermis I Ders Hypodermis Deep culançous vascular plexus Popikuy lıyor of demis Pacin an corpusche of comes Sweat gand Sesat duet Subcutaneous Seveal gand Hairfollicle Aznice pili muscin Sabesnous gland

Hypodermis:

Loose connective tissue of variable thickness also known as Superficial Fascia - mainly composed of adipose tissue (thermal insulation, shock absorber, storing energy) - mediates attachment of dermis to underlying tissues and mobility of the skin - Superficial Musculo-Aponeurotic System (SMAS)

SUPERFICIAL FASCIA

Skin Subdermal "vertical" fat Fascia superficialis Lymphatic vessels Fascia superficialis fused with premuscular fascia Deep "horizontal" lamellar fat Premuscular fascia Muscle

Elastic Fiber Properties

elastic fiber Elastin fibre - branched and wavy - contain protein elastin - low tensile strength and high deformation range (>100% ) but return to original length STRETCH RELAX single elastin molecule cross-link-

Skin External oblique muscle Superficial fascia- fatty layer (Camper's fascia) Internal oblique muscle Superficial fascia- membranous layer (Scarpa's fascia) Transversus abdominis muscle Transversalis fascia Parietal peritoneum Extraperitoneal fascia

GALEA APONEUROSIS AND INTRINSIC FACIAL MUSCLES

Galea aponeurotica Superior auricular muscle Occipitofrontalis, frontal belly Temporo- parietal Orbicularis oculi ior auricular muscle Nasalis rator labii superioris eque nasi rator labii superioris omaticus minor Occipitofrontalis, occipital belly rbicularis oris Posterior auricular muscle omaticus major Risorius Depressor labii inferioris Mentalis Depressor anguli oris Platysma The epicranial aponeurosis (aponeurosis epicranialis, galea aponeurotica) is an aponeurosis (a tough layer of dense fibrous tissue) which covers the upper part of the cranium in humans and various other animals. In humans, it is attached in the interval between its union with the occipitofrontalis muscle, to the external occipital protuberance and highest nuchal lines of the occipital bone; in front, it forms a short and narrow prolongation between its union with the frontalis muscle or frontal part of the occipitofrontalis muscle.

SUPERFICIAL MUSCULO-APONEUROTIC SYSTEM

1. Skin
2. Subcutaneous
3. Musculo-aponeurotic
4. Retaining ligaments and spaces
5. Periosteum and deep fascia

Superficial muscular aponeurotic system (SMAS) is an area of musculature of the face. This muscular system

SKIN VASCULAR SUPPLY

SKIN CIRCULATION

• Subepidermal + Dermal «- Subdermal - Plexuses + Subcutaneous Fascia Prefascial and subfascial -Muscle Musculocutaneous artery Regional artery Septocutaneous artery

1 - 1 warm - - hot

SKIN NERVE ENDINGS

Exteroceptors (stimulus outside of body)

• Pacinian corpuscles (lamellated) : deep pressure and stretch
• Meissner's corpuscles (tactile) : light touch, vibration and discriminative touch.
• hair root plexus
• free nerve endings(naked): nociceptors (pain) and thermoreceptors (hot - deep and cold- surface)
• Ruffini's corpuscles: deep pressure

FINGERPRINTS

What are fingerprints?

Found on fingers, palms, toes, soles of feet. Composed of ridges (hills) and furrows (valleys) - Depending on Dermal papillae distribution. ▪ ▪ . Friction ridge skin pattern Black = Ridges White = Valleys

FINGERPRINTS DEVELOPMENT

What are fingerprints?

. Develop in early embryonic life. Pattern is based on genetics and on physical compression of the fetus during pregnancy . So identical twins do not have identical fingerprints ▪

FINGERPRINTS PATTERNS

Arch Loop Whorl

1 Opening of sweat gland ducts Epidermal ridge

Cutaneous "spots"

Nevi (sing. Nevus), generally known as moles, are clusters of melanocytes that appear as small, dark spots.

Types of Nevi

Normal Ephelides (freckle) Lentigo Junctional naevus Compound naevus Intradermal naevus Blue naevus

• One melanocyte to six basal cells
• No increase in number but increase in pigment
• Increased numbers
• Nests of naevus cells
• Nests in dermis but cells get smaller with depth
• Naevus cells only in dermis
• Nodules of dendritic cells deep in dermis

The ABCDEs of Detecting Melanoma

A Asymmetry

NORMAL Symmetrical

MELANOMA Asymmetrical

B Border

Borders Are Even

Borders Are Uneven

C Color

One Color

Multiple Colors

D Diameter

Smaller Than 1/4 Inch

Larger Than 1/4 Inch

E Evolving

Ordinary Mole

Changing in Size, Shape and Color

SKIN APPENDAGES

Hairs V Glands Nails

THE PILOSEBACEOUS UNIT

The structure consisting of hair, hair follicle, arrector pili muscle and sebaceous gland.

Tsc SG Epidermis SS SB Basement membrane Sebaceous gland Permanent segment Dermis Fibroblasts Arrector pili muscle Bulge Outer root sheath Cycling segment Matrix Dermal papilla Hypodermis

Functions of Hairs

V Minor role in humans Protection Thermoregulation V Sensory

Characteristics of Hairs

Present over almost the entire body surface num > 600/cm2 lenght <1 >1 mm width 0.005 ->0.6 mm Vellus hair: fine hairs Terminal hair: hair; axillary and pubic region Distribution depends on: · Sex · Race · Hormones (sex , thyroid, suprarenal, pituitary)

Hair Follicle Structure

Follicle the whole structure surrounding hairs. Bulb is the enlargement at the end of the follicle and houses the germinal layer. Papilla (nipple like) is located in the bulb and is where the blood supply nourishes the hair. Upper part: migrated cells layer during differentiation Hair bulb (papilla) Germinal matrix: closely packed pluripotential cells Keratinocytes Melanocytes Langherans cells

Hairs Structure

Medulla

the inner most layer may even be absent (especially in fine or light blonde hair)

Cortex

provides strength, moisture, colour and texture

Cuticle

outermost layer protects the cortex a hard shingle-like layer of overlapping cells, like scales

SHAFT - ROOT - BULB Bulb contains matrix - inductive mesenchymal cells - melanocytes Hair papilla is at the base of the follicle and contains blood vessels and nerves

Hair Cuticle

Overlapping cuticle cells on the surface of hair

Cortex

Long, slender cells packed like a bundle of sticks

Medulla

A slender, hollow tube in the center of large, coarse hairs