Download MBBS Anatomy PPT 26 Skin Superficial Fascia And Deep Fascia Notes

SKIN

DEFINITION

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? GENERAL COVERING OF THE EXTERNAL
? SURFACE OF THE BODY
? FORMS 15% OF THE TOTAL BODY WEIGHT
? THICKNESS-1.5 to 5.0 mm
? LARGEST ORGAN OF THE BODY

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INTEGUMENTARY SYSTEM

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Some Facts about Skin

? Surface area: 1.5-2.0 sq meters
? Growth rate of nail: 0.1mm per day
? Growth rate of hair: 1.5-2.2 mm per week

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? Life span of hair:
Eyelashes, axilla- 4 months
Scalp ? 4 years

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STRUCTURE OF SKIN

? TWO DISTINCT LAYERS
* EPIDERMIS
* DERMIS

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? EPIDERMIS : SUPERFICIAL AND AVASCULAR
? DERMIS : DEEP AND VASCULAR

TERMS USED FOR MOVEMENTS

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TYPES OF SKIN

? THICK SKIN - EPIDERMIS VERY THICK
USUALLY HAIRLESS ON
PALMS OF HAND & SOLES

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OF FEET
? THIN SKIN ? COVERS GREATER PART OF
BODY & IS USUALLY HAIRY
? EXCEPTION ? SCALP : THICK AND HAIRY

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Layers Of Skin

Epidermis:
? Composed of keratinized

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stratified squamous epithelium.

Dermis:
? Papillary region composed of

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loose connective tissue.

? Reticular region composed of

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dense irregular connective tissue.

Hypodermis:
? Composed of areolar tissue with

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abundant adipocytes

Cells

? Keratinocytes

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? Melanocytes-pigment forming cells from

neural crest cells

? Merkel cells-sensory mechanoreceptors

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? Langerhans cells-antigen presenting cells from

bone marrow

? Free nerve endings

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LAYERS OF THE EPIDERMIS

Stratum Basale (Germinal/

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Malpighian layer):

? Single layer of cuboidal cells resting on

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basement membrane.

? High mitotic activity.
Stratum Spinosum:
? Several layers of polygonal cells.

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? Cells are held together by

desmosomes.

Stratum Granulosum:

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? 3-5 layers of flattened polygonal cells.
? Cells contain keratohyaline granules.

contd....

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Stratum Lucidum:

? Seen only in non-hairy or thick skin.

? Cel s are flattened, translucent,

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eosinophilic with indistinct

boundaries & nucleus.

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? Contains a product of

keratohyaline i.e. eleidin.

Stratum Corneum:

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? Composed of structureless

dehydrated dead cel s.

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? Flattened & scale-like.

? Fil ed with keratin.

? Superficial layer is continuosly

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sloughed off.

Stratum Basale

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Stratum Spinosum

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Stratum Granulosum

Stratum Lucidum

Stratum Corneum

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SPECIALIZED CELLS OF THE EPIDERMIS

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Keratinocytes:
? Most common cel s of the epidermis.
? Provides protection and

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waterproofing sealant.

Melanocytes:
? Rounded cel s with dendrite-like

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branches.

? Present in Stratum basale.
? Produces melanin pigment

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responsible for the colour of skin.

? Melanin is a brown/black pigment

that absorbs UV-light.

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SPECIALIZED CELLS OF THE EPIDERMIS

Langerhans Cells (antigen presenting

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cells):

? Non-pigmented granular dendrocytes.

? Present in Stratum spinosum.

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? Nucleus is indented at many places &

cytoplasm contains rod-shaped

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granules.

? They participate in immune responses

against bacteria and viruses.

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Merkel Cells:

? Found in Stratum basale.

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? Sensory cells innervated by sensory

nerves.

? Abundant in fingertips, oral mucosa &

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hair follicles.

? Function as mechanoreceptors.

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PIGMENTATION OF SKIN

The colour of skin depends upon fol owing factors:

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? Carotene: yellow-orange pigment (precursor of vitamin A)

found in stratum corneum & dermis.

? Melanin: produced in epidermis by melanocytes

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gives black colour to the skin.

? Hemoglobin (in blood vessels of dermis): gives pink colour

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to the skin.

LAYERS OF THE DERMIS

?

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Papil ary layer:

-Narrow band of loose connective tissue.

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-In contact with basement membrane of

stratum basale.

-Dermal papil ae (finger- like processes)

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- provide mechanical anchorage and supply

nerves and blood vessels

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?

Reticular layer:

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-

4

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Dense irregular connective tissue.

Dermal

papil a

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-Thick elastic fibres.

-may be involved in development of skin lines

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3

1

2

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TYPES OF SKIN

Th

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Thin Skin

in Skin

Th

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Thick i

Skck

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in Skin

Layers of epidermis

St. corneum &

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St. corneum & spinosum are

spinosum are thin while thick while lucidum is

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lucidum is absent.

present.

Thickness of epidermis

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0.10-0.15 mm

0.6-4.5 mm

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Epidermal ridges

Absent

Present (well developed

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dermal paplillae)

Hair fol icles, arrector pili Present

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Absent

muscle & sebaceous

gland

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Sweat glands

Few

Many

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Sensory receptors

Less

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More

Distribution

Covers all parts of body Present in palms, palmar

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except palms & soles

surface of digits & soles

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APPENDAGES OF THE SKIN


HAIRS:

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? Keratinized filaments derived from

invagination of the basal layer of

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epidermis into the dermis.

? Parts-

a) Root: enclosed by hair follicle.

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b) Shaft: projects above the surface.

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? Hair fol icle: tubular invagination,
partly epidermal and partly dermal in

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origin.



contd.....

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Structure of shaft and root:
? Medul a
? Cortex
? Cuticle

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Hair fol icle:
? Tubular invagination of epidermis

& dermis in which hair root

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resides.

? Layers: 3 (inner root sheath, outer

root sheath, connective tissue

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sheath).

contd.....

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? Hair bulb: lower expanded

end of hair follicle.

? Hair papil a: the

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indentation at the base of
hair bulb by part of the
dermis.

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contd.....

Arrector Pilorum Muscle:

? Smooth muscle innervated

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by sympathetic nerves.

? Extends from papil ary

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layer of dermis to the

connective tissue sheath of

a hair fol icle.

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? Contraction of muscle

presses the sebaceous

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gland which squeezes out

sebum.

? Formation of "goose flesh".

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APPENDAGES OF THE SKIN

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NAILS:

? Hardened keratin plates on

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the dorsal surface of the

tips of fingers & toes.

? Parts:

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a) Root

b) Free border

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c) Body

? Nail bed: tissue on which

the nail rests. Made up of

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stratum basale & spinosum.

APPENDAGES OF THE SKIN

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SEBACEOUS GLANDS:

? Distributed all over the

dermis of the skin, except

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for the palms & soles.

? Abundant in the scalp,

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face, around the

apertures of the ear, nose,

mouth & anus.

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APPENDAGES OF THE SKIN

SEBACEOUS GLANDS:

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? Holocrine in nature.

? Number of alveoli

connected to broad duct

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that opens into hair

follicle.

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? Produces an oily

secretion called sebum.

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SWEAT GLANDS (SUDORIFEROUS GLANDS)

? Absent from lips, glans & nail bed.

? Mode of secretion: merocrine

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? Simple tubular gland

? 2 parts:

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(a) Secretory portion

(b) Excretory duct

Secretory portion:

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? Twisted coil like structure with simple

cuboidal epithelium.

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? 3 types of cel s: clear cel s, dark cel s,

myoepithelial cel s.

Excretory duct:

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? Long & extends from secretory portion to

surface of epidermis.

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contd....

2 types:
Eccrine:
? Most numerous in the soles &

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palms.

? Produces thin watery secretion.
Apocrine:

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? Confined to axil a, eyelids (Moll's

glands), nipple & areola of breast,

perianal region, and the external

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genitalia.

? Produces thick odourous secretion.
? Ceruminous glands & lactating

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mammary glands are modified

apocrine sweat glands.

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Sweat Gland


SURFACE IRREGULARITIES

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? FLEXURE LINES - Permanent lines along

which

the skin folds during habitual

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movements of joints

? CLEAVAGE LINES - According to arrangement

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of fibres in deep fascia, horizontal in

trunk, in old age fibres atrophy and skin

wrinkles

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PAPILLARY RIDGES

PAPILLARY RIDGES
? Palms and soles and digits

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? Form narrow ridges separated

by fine paral el grooves,

? corrospond to dermal papil ae

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? Study is cal ed dermatoglypics
? Pattern of finger prints- loops ,

whorls and arches and

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composite

Langer's lines(Cleavage lines)

? Langer lines of skin tension, or

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sometimes called cleavage lines

? Correspond to the natural orientation

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of collagen fibers in the dermis,

? Are generally parallel to the orientation of

the underlying muscle fibers.

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? Langer's lines have relevance to forensic

science and the development of surgical

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techniques

Langer's lines

? Langer lines of skin tension, or

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sometimes cal ed cleavage

lines

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? Correspond to the natural

orientation of collagen fibers

in the dermis,

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? Are general y paral el to the

orientation of the underlying

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muscle fibers.

? Langer's lines have relevance

to forensic science and the

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development of surgical

techniques
Applications of Langer Lines

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? Incisions made parallel to Langer's lines may

heal better and produce less scarring than

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those that cut across. Conversely, incisions

perpendicular to Langer's lines have a

tendency to pucker and remain obvious,

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although sometimes this is unavoidable

? In old age, elastic fibres atrophy and skin

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becomes wrinkled

Linea gravidarum

? Rupture of fibre bundles

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of dermis due to

excessive stretching

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result in prominent

white lines.

? Seen in anterior

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abdominal wall in

pregnancy.

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Rule of Nine: To estimate

the extent of damaged skin

in burn injuries.

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? First degree burn-

only epidermis.

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? Second degree burn-

epidermis + upper region of

dermis.

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? Third degree burn-

entire thickness of skin.

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Dermatomes

? The strip of skin

supplied by a single

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spinal nerve is called

dermatome.
FUNCTIONS OF SKIN

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? Protective shield for the body
? Barrier to water
? Thermoregulation
? Important sense organ (pain, touch,

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temperature & pressure)

? Absorption of ultraviolet radiation from sun

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for the production of vitamin D

APPLIED ANATOMY

? Skin is pale in anemia, yel ow in

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jaundice and blue in cyanosis

? Skin incisions should be made paral el to

lines of cleavage to have the smal est scar

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? Sebaceous cyst is common in scalp
due to obstruction to sebaceous
duct

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SUPERFICIAL FASCIA

SUPERFICIAL FASCIA

? DEFINITION- General coating of the body

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beneath the skin made up of loose

areolar tissue and fat

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? ABUNDANCE OF FAT- Front of thigh and

anterior abdominal wal

? ABSENCE OF FAT- Eyelids & external ear

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? In females there is more fat and it is
evenly distributed

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TERMS USED FOR MOVEMENTS

IMPORTANT FEATURES

? Most distinct in lower part of

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anterior abdominal wal & limbs
? Very thin on dorsal aspect of hands &

feet, sides of neck, face.

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? Very dense in scalp, palms and soles.


IMPORTANT FEATURES

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? IT CONTAINS
1. Cutaneous nerves &

vessels

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2. Groups of lymph nodes
3. Subcutaneous muscle in
neck

FUNCTIONS

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? Helps in movements of skin
? Allows for the passage of the vessels &

nerves to the skin

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? Conserves body heat as fat is a bad
conductor of heat
? Fat fills hollow spaces like axilla &
orbits

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DEEP FASCIA

? Deep fascia is a fibrous sheet which

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covers the body beneath the superficial
fascia.

? It is devoid of fat, and is usual y inelastic

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and tough


DISTRIBUTION OF DEEP FASCIA

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? Best seen in limbs where it forms tough and

tight sleeves

? Well defined in the neck where it

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? forms a collar
? Not well formed on the trunk and face
? Blends with periosteum of a subcutaneous

bone

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MODIFICATIONS OF DEEP FASCIA

? Inter muscular septa which divides limbs

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into compartments

? Thickenings form retinacula around joints

like wrist and ankle

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? Forms sheath around large arteries
? In palms & soles form aponeurosis
? Form investing layer of fascia in region of

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neck giving it shape.

INTERMUSCULAR SEPTA

RETINACULA

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INVESTING LAYER OF FASCIA

FUNCTIONS

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? Keeps underlying structures in position
? Provides extra surface for muscle
attachment
? Helps in venous return

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? Helps muscles in action by applying tension

and pressure

? Retinacula keep tendons in position

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MCQ

Q1. Which layer is present only in thick skin:

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a. Stratum basale
b. Stratum spinosum
c. Stratum granulosum
d. Stratum lucidum

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MCQ

Q2. The characteristic feature of reticular layer of
dermis is:

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a. High mitotic activity
b. Contains keratin granules
c. Dense irregular connective tissue
d. Finger like processes
MCQ

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Q3. Secretion of sebaceous glands is aided by
contraction of:

a. Arrector pilorum muscle

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b. Myoepithelial cells
c. Papillary layer of dermis
d. Reticular layer of dermis

MCQ

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Q4. Langerhans cells are present in:

a. Stratum basale
b. Stratum spinosum

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c. Stratum granulosum
d. Stratum lucidum