The skin is the largest organ of the body, weighing approximately 4 kg. It has two layers - the epidermis and dermis. The skin protects the body, regulates temperature, and has sensory functions. The fascia is a fibrous tissue that surrounds muscles and organs. It has three types - superficial, deep, and subserous fascia. The deep fascia encloses muscles and sends intermuscular septa. It has several modifications like retinacula, aponeurosis, and sheaths. The fascia has functions like muscle gliding, organ suspension, and transmitting movement.

2. SKIN
• SKIN IS THE LARGEST SENSORY ORGAN OF THE BODY. ITS WEIGHT IS 16% OF BODY WEIGHT
AND IS ABOUT 4 KG IN WEIGHT. THE SKIN FORMS AN OUTER PROTECTIVE COVER FOR THE
ENTIRE SURFACE OF THE BODY. THE THICKNESS OF SKIN VARIES IN DIFFERENT PARTS OF THE
BODY. ACCORDINGLY, THERE ARE TWO TYPES OF SKIN.
1. THICK SKIN: IT COVERS THE BACK OF THE BODY, PALMS AND SOLES. IT IS HAIRLESS.
2. THIN SKIN: AT OTHER PLACES OF BODY, THE SKIN IS THIN AND HAIRY. VERY THIN SKIN IS
PRESENT ON EYELIDS.
• MUCOCUTANEOUS JUNCTION
IT IS THE PLACE WHERE THE SKIN IS CONTINUOUS WITH THE MUCOUS MEMBRANE.
• EXAMPLE: LIPS, ANUS, AND EYELIDS.

3. • THE SKIN IS THE OUTER COVERING OF THE BODY. IT PROVIDES THE DYNAMIC
INTERPHASE BETWEEN THE BODY AND THE EXTERNAL ENVIRONMENT.
• THE SKIN IS CONSIDERED AS AN ORGAN SINCE IT CONSISTS OF SEVERAL KINDS
OF TISSUES THAT ARE STRUCTURALLY ARRANGED TO FUNCTION TOGETHER.
• IT IS THE LARGEST ORGAN OF THE BODY, COVERING OVER 7600 SQ. CM (3000
SQ. IN) AREA IN AN AVERAGE ADULT AND ACCOUNTS FOR APPROXIMATELY 7%
OF THE PERSON'S TOTAL BODY WEIGHT.
• THE GENERAL APPEARANCE AND CONDITION OF THE SKIN IS CLINICALLY
IMPORTANT BECAUSE IT PROVIDES CLUES TO CERTAIN BODY FUNCTIONS AND
DYSFUNCTIONS. THUS, SKIN REFLECTS OUR GENERAL HEALTH. A HEALTHY SKIN
INDICATES A HEALTHY BODY.

4. STRUCTURE OF SKIN
• THE SKIN CONSISTS OF TWO PRINCIPAL LAYERS: THE EPIDERMIS AND THE
DERMIS.
• THE SURFACE EPITHELIUM OF SKIN IS EPIDERMIS. IT IS OF THE STRATIFIED
SQUAMOUS VARIETY. THE VARIOUS APPENDAGES OF SKIN, VIZ. SWEAT GLANDS,
SEBACEOUS GLANDS, HAIR AND NAILS ARE SPECIALIZED DERIVATIVES OF THIS
EPIDERMIS. THE DEEPER DERMIS CONSISTS MAINLY OF BUNDLES OF COLLA- GEN
FIBRES TOGETHER WITH SOME ELASTIC TISSUE, BLOOD VESSELS, LYMPHATICS
AND NERVE FIBRES.

5. FUNCTIONS
• PROTECTION: PROTECTS THE BODY FROM CHEMICALS, ULTRAVIOLET RAYS, INJURY AND
MICROORGANISMS. MECHANICAL
• BARRIER: ACTS AS A BARRIER AND PREVENTS WATER ABSORPTION.
• TEMPERATURE REGULATION: IT HELPS IN MAINTAINING NORMAL BODY TEMPERATURE.
IN SUMMER BY SECRETION AND EVAPORATION OF SWEAT. IN WINTER DUE TO THE
PRESENCE OF SUBCUTANEOUS FAT, IT MAINTAINS BODY TEMPERATURE.
• SENSORY: PRESENCE OF VARIOUS SENSORY NERVE ENDINGS IN THE SKIN FACILITATES
PERCEPTION OF PAIN, TEMPERATURE, TOUCH, ETC. SENSATIONS.
• EXCRETORY: EXCRETION OF UREA.
• VITAMIN D: IT SYNTHESIZES VITAMIN D

6. FASCIA
THE WORD FASCIA IS DERIVED FROM LATIN = "BAND FASCIA IS SINGULAR AND FASCIAE ARE PLEURAL.
• DEFINITION
FIBROUS TISSUE NETWORK IN THE FORM A SHEET OR FLAT BAND.
• LOCATION
• BELOW THE SURFACE OF THE SKIN, COVERING AND SEPARATING MUSCLES, ORGANS AND OTHER
TISSUES.
• STRUCTURE
• DENSE REGULAR CONNECTIVE TISSUE. CONTAINS CLOSELY PACKED BUNDLES OF COLLAGEN FIBERS.
IT IS ORIENTED IN A WAVY PATTERN PARALLEL TO THE DIRECTION OF PULL.

7. • FUNCTIONS
• SLIDING AND GLIDING SURFACE FOR MUSCLES TO REDUCE FRICTION.
• SUSPENDS ORGANS IN THEIR ANATOMICAL LOCATION.
• TRANSMITS MOVEMENT FROM MUSCLES TO THE BONES TO WHICH THEY ARE
ATTACHED.
• SUPPORTIVE AND MOVABLE WRAPPING FOR NERVES AND BLOOD VESSELS AS THEY PASS
THROUGH AND BETWEEN THE MUSCLES.

8. TYPE
• THREE DIFFERENT TYPES DEPENDING ANATOMICAL LOCATION
AND FUNCTION.
• SUPERFICIAL FASCIA
• DEEP FASCIA
• SUBSEROUS FASCIA

9. SUPERFICIAL FASCIA
• IT IS A SUBCUTANEOUS LAYER OF LOOSE AREOLAR TISSUE WHICH UNITES DERMIS OF SKIN TO
THE UNDERLYING DEEP FASCIA. IT ALLOWS MOBILITY OF THE DERMIS ON THE UNDERLYING
STRUCTURES. IT IS HEAVILY INFILTRATED WITH FAT. THE AMOUNT OF FAT VARIES IN DIFFERENT
PARTS OF THE BODY. THE SUPERFICIAL FASCIA ALMOST EVERYWHERE IN THE BODY CONTAINS
FAT EXCEPT IN THE
1. EYELIDS
2. EXTERNAL EAR/PINNA
3. PENIS
4. SCROTUM
5. FLEXION CREASES OF THE DIGITS

10. • THE AMOUNT OF FAT IN SUPERFICIAL FASCIA IS MORE IN FEMALES AND CHILDREN. THE FAT BEING A BAD
CONDUCTOR OF HEAT, THE FEMALES AND CHILDREN FEEL LESS COLD. FURTHER, IT IS THE MAIN FACTOR
RESPONSIBLE FOR THE SMOOTH EXTERNAL CONTOURS OF THE FEMALES. SPECIAL FAT DEPOSITS AT
CERTAIN SITES IN WOMEN FORM THEIR SECONDARY SEXUAL CHARACTERISTICS.
• THESE SITES ARE
1. GLUTEAL AND LUMBAR REGION
2. FRONT OF THIGH
3. ANTERIOR ABDOMINAL WALL BELOW THE NAVEL (UMBILICUS)
4. BREASTS

11. 5. POST-DELTOID REGION
6. CERVICAL THORACIC REGION
• THE SUPERFICIAL FASCIA ACTS AS A DISTRIBUTING LAYER, IN WHICH THE BLOOD
VESSELS, LYMPHATICS AND NERVES CAN TRAVEL BEFORE ENTERING THE DERMIS.

12. THE SUBCUTANEOUS FASCIA IN THE LOWER ANIMAL CONTAINS A THIN SHEET OF MUSCLE CALLED
PANNICULUS CARNOSUS. ITS FIBRES ARE INSERTED INTO THE SKIN. THE TWITCH OF ITS FIBRES PROMPTS THE
INSECTS TO GO AWAY OR FLY OFF.
• IN HUMANS, THE PANNICULUS CARNOSUS IS REPRESENTED BY:
-MUSCLES OF FACIAL EXPRESSION (SKELETAL MUSCLES)
- PLATYSMA IN THE NECK (SKELETAL MUSCLE)
- SUBAREOLAR MUSCLE OF THE BREAST (SMOOTH MUSCLE)
- PALMARIS BREVIS (SKELETAL MUSCLE)
-DARTOS IN THE SCROTAL WALL (SMOOTH MUSCLE)
-CORRUGATOR CUTIS ANI (SMOOTH MUSCLE).

13. FUNCTIONS OF SUPERFICIAL FASCIA
• THE FUNCTIONS OF SUPERFICIAL FASCIA ARE AS FOLLOWS:
• 1. FORMS AN INSULATING LAYER DEEP TO SKIN
• 2. RESPONSIBLE FOR SMOOTH EXTERNAL CONTOURS OF FEMALES AND CHILDREN
• 3. ALLOWS MOBILITY OF THE SKIN ON THE UNDERLYING STRUCTURES
• 4. PROVIDES EASY PASSAGE TO NERVE, VESSELS AND LYMPHATICS
• 5. ACTS AS CUSHION AT CERTAIN SITES (DUE TO EXCESSIVE ACCUMULATION OF FAT,
E.G. BUTTOCKS)

14. CLINICAL CORRELATION
• SUBCUTANEOUS INJECTIONS:
• SUBCUTANEOUS INJECTIONS ARE PAINFUL DUE TO PRESENCE OF PAIN
RECEPTORS IN IT. DRUGS ADMINISTERED BY THIS ROUTE ARE ABSORBED
SLOWLY BECAUSE SUBCUTANEOUS TISSUE HAS POOR BLOOD SUPPLY. ONLY
SMALL DOSES (0.5-1 ML) OF WATER-SOLUBLE DRUGS ARE GIVEN
SUBCUTANEOUSLY. FOR EXAMPLE, INSULIN INJECTIONS IN DIABETIC PERSONS
ARE GIVEN SUBCUTANEOUSLY IN SMALL DOSES FOR SLOW RELEASE OVER A
LONG DURATION.

15. SITES OF SUBCUTANEOUS INJECTIONS:
• THE IDEAL SITES OF SUBCUTANEOUS INJECTIONS ARE
(A) POSTERIOR ASPECT OF ARM
(B) ANTERIOR ASPECT OF FOREARM
(C) ANTERIOR ABDOMINAL WALL
(D) ANTERIOR ASPECT OF THIGH.

16. DEEP FASCIA
• THE DEEP FASCIA IS A TOUGH, INELASTIC MEMBRANE OF FIBROUS
TISSUE WHICH ENCLOSES THE BODY DEEP TO SUBCU- TANEOUS
TISSUE, LIKE A TIGHT SLEEVE. IT KEEPS THE SOFT TISSUES IN PLACE
AND MAINTAINS THE SHAPE OF THE BODY. THE DEEP FASCIA IS BEST
MARKED IN THE LIMBS AND NECK. IN THE LIMBS, IT SENDS SEPTA
(INTERMUSCULAR SEPTA) BETWEEN THE GROUPS OF MUSCLES TO
ATTACH WITH THE PERIOSTEUM OF THE BONE. THESE SEPTAE ENABLE
A GROUP OF MUSCLES TO CONTRACT INDIVIDUALLY AND SLIDE FREELY
OVER THE ADJACENT MUSCLE GROUPS.

17. • IN THE NECK, IT FORMS THREE LAYERS:
1. GENERAL INVESTING LAYER, WHICH ENCLOSES THE STRUCTURES OF THE NECK LIKE
A COLLAR
2. PRETRACHEAL FASCIA, WHICH PASSES IN FRONT OF THE TRACHEA
3. PREVERTEBRAL FASCIA, IN FRONT OF THE CERVICAL OF PART THE VERTEBRAL
COLUMN.
THUS, THE NECK IS DIVIDED INTO TWO COMPARTMENTS: VISCERAL COMPARTMENT
AND MUSCULOSKELETAL COMPARTMENT.

18. MODIFICATIONS OF DEEP FASCIA
• RETINACULA. AT CERTAIN SITES, DEEP FASCIA
THICKENS TO FORM THICK BANDS TO RETAIN THE
TENDON OF LONG MUS- CLES IN PLACE AND
PREVENT THEIR BOWSTRINGING DURING ACTION
OF THESE MUSCLES. THESE BANDS ARE CALLED
RET- INACULA, VIZ. FLEXOR AND EXTENSOR
RETINACULA AROUND WRIST AND ANKLE JOINTS.

19. APONEUROSIS. IN PALMS AND SOLES, IT
THICKENS TO FORM PALMAR AND PLANTAR
APONEUROSIS TO PROTECT THE UNDERLYING
STRUCTURES. IN TRUE SENSE, AN
APONEUROSIS IS A THICK, WIDE SHEET OF
FIBROUS TISSUE THAT PROVIDES ATTACHMENT
TO MUSCLES. THE PALMAR AND PLANTAR
APONEUROSIS REPRESENT THE DEGENERATED
TENDONS OF PALMARIS LONGUS AND
PLANTARIS MUSCLES, RESPECTIVELY.

20. FIBROUS SHEATHS. AT CERTAIN SITES, DEEP FASCIA CONDENSES TO FORM A SHEATH AROUND
NEUROVASCULAR BUNDLES, VIZ.
(A) CAROTID SHEATH ENCLOSING COMMON CAROTID ARTERY, INTERNAL JUGULAR VEIN AND
VAGUS NERVE
(B) AXILLARY SHEATH ENCLOSING AXILLARY ARTERY AND AXILLARY VEIN (DEEP FASCIA IS DENSE
AROUND THE ARTERY AND RATHER LOOSE AROUND THE VEINS TO ALLOW THE VEINS TO DISTEND)

21. 4. FIBROUS CAPSULES. AT SOME SITES, IT SPLITS
TO ENCLOSE CERTAIN GLANDS TO FORM THEIR
CAPSULE, VIZ. PAROTID GLAND, SUBMANDIBULAR
GLAND, THYROID GLAND ETC.
5. INTEROSSEOUS MEMBRANES. IN THE
FOREARM AND LEG, THE DEEP FASCIA IS
MODIFIED TO FORM INTEROSSEOUS
MEMBRANES.
6. INTERMUSCULAR SEPTA. IN THE LIMBS, DEEP
FASCIA SENDS FIBROUS SEPTA FROM ITS DEEP
SURFACE TO HELP FORM THE COMPARTMENTS
OF THE MUSCLES.

23. 7. FIBROUS FLEXOR SHEATHS. ON THE FLEXOR
SURFACES OF FINGERS AND TOES, THE DEEP
FASCIA THICKENS TO FORM THE FIBROUS FLEXOR
SHEATH AROUND THE LONG FLEXOR TENDONS.
THESE SHEATHS PREVENT THE TENDONS FROM
BOWING OUT OF POSITION.
8. LIGAMENTS. THE LIGAMENTS OF JOINTS ARE
CONSIDERED AS LOCALIZED THICKENED BANDS
OF THE DEEP FASCIA.
9. FASCIAL SHEATH. IT FORMS SHEATH AROUND
CERTAIN MUSCLES, VIZ. PSOAS SHEATH.

24. CLINICAL CORRELATION
• SINCE DEEP FASCIA DEFINES FASCIAL PLANES BETWEEN THE MUS-CLES,
THESE PLANES FORM POTENTIAL PATHWAYS FOR INFECTION TO SPREAD.
• PUS TENDS TO FORCE ITS WAY ALONG THE LINES OF LEAST RESISTANCE
PROVIDED BY THE PLANES OF THE DEEP FASCIA.
• PUS CAN TRACK DOWN THROUGH THE FASCIAL SLEEVES FORMED BY
DEEP FASCIA AROUND THE BLOOD VESSELS AND MUSCLES, E.G. PUS
FROM ROOT OF NECK CAN TRACK DOWN INTO THE ARM THROUGH
AXILLARY SHEATH.

25. • PUS FROM TUBERCULAR THORACIC SPINE CAN TRACK DOWN IN THE INGUINAL
REGION THROUGH PSOAS SHEATH.
• SURGEONS CAN OPERATE ALONG THE FASCIAL PLANES WITH MINIMAL INJURY TO
THE ADJOINING STRUCTURES. DEEP FASCIA IS LEAST MARKED, I.E. SCARCELY
DEMONSTRABLE IN THE REGION OF ANTERIOR ABDOMINAL WALL AND IS
CONSIDERED TO BE ABSENT.

26. SITES WHERE DEEP FASCIA IS ABSENT
• THE DEEP FASCIA IS ABSENT AT THE FOLLOWING SITES:
1. FACE
2. BREAST
3. ANTERIOR ABDOMINAL WALL
4. PENIS AND SCROTUM
5. ISCHIORECTAL FOSSA

27. • THE DEEP FASCIA IS VERY SENSITIVE.
ITS NERVE SUPPLY IS DERIVED FROM
1. NERVES SUPPLYING OVERLAPPING SKIN.
2. NERVES SUPPLYING ENCLOSED MUSCLES.

28. FUNCTIONS OF DEEP FASCIA
1. KEEPS THE UNDERLYING STRUCTURES IN POSITION AND PRESERVES THE
CHARACTERISTIC SURFACE CONTOUR, VIZ. LIMBS, NECK
2. PROVIDES EXTRA SURFACE FOR MUSCULAR ATTACHMENTS
3. FACILITATES VENOUS AND LYMPHATIC DRAINAGE
4. BINDS BONES, VIZ. INTEROSSEOUS MEMBRANES
5. RETAINS THE LONG TENDONS IN PLACE TO PREVENT THEIR BOWSTRINGING AND
ALSO SERVES AS PULLEYS DURING THEIR ACTIONS