Integumentary System - Skin and Fascia PDF

Integumentary System Skin and Fascia Dr. Nisreen Faizo, MBBS, MSc., PhD Department of Anatomy, College of Medicine King Abdulaziz University, Jeddah  The Integumentary System The Skin The skin is considered as the lar...

Integumentary System Skin and Fascia Dr. Nisreen Faizo, MBBS, MSc., PhD Department of Anatomy, College of Medicine King Abdulaziz University, Jeddah  The Integumentary System The Skin The skin is considered as the largest organ of the body, with a surface area of about 1.5-2 m2 in adults. The skin contains appendages as: glands (sebaceous and sweat), hairs and nails. The skin has a rich blood supply that reaches it via the subcutaneous tissues. The blood vessels form a freely anastomosing plexuses, which are important in maintaining the circulation during undercutting of the skin.  Functions of skin Protection of the body from environmental effects, such as abrasions, fluid loss, harmful substances, ultraviolet radiation, and invading microorganisms. Containment for the body’s structures (e.g., tissues and organs) and vital substances (especially extracellular fluids), preventing dehydration, which may be severe when extensive skin injuries (e.g., burns) are experienced. Thermal regulation through the evaporation of sweat and/or the dilation or constriction of superficial blood vessels. Sensation (e.g., pain) by way of superficial nerves and their sensory endings. Synthesis and storage of vitamin D. Protection Containment from Thermal for body Sensation Vitamin D environmental regulation structures stresses  Structure of the skin (Histology) The skin consists of 2 principal layers: The epidermis ‫البشرة‬: It is keratinized epithelium, nonvascular superficial layer of the skin that provides a protective outer surface. It is sensitive to touch, pain and temperature. Its thickness is varied in different parts of the body: In the palms of the hands and the soles of the feet, it is thick to withstand the wear and tear in these regions. In other areas of the body, it is thin. The dermis ‫اآلدمة‬: It is the deep layer, dense contains collagen and elastic fibers. It provides skin tone, strength and toughness. It is connected to the underlying deep fascia or bones by the superficial fascia (or subcutaneous tissue). The hypodermis, or subcutaneous layer, is located beneath the skin.  Specialized structures of skin Dermis contains: Hair follicles. Smooth arrector muscles. Sebaceous glands. Sweat glands. Contraction of the arrector muscles causes the hairs to stand up straighter (goose bumps), thereby compressing the sebaceous glands and helping them secrete their oily product onto the skin surface. Sweat glands secrete sweat which evaporates from skin providing thermoregulatory mechanism for heat loss (cooling).  Langer lines (Tension/Cleavage lines) They are skin tension lines and are topological lines drawn on a map of the human body. They correspond to the natural orientation of collagen fibers in the dermis. They tend to spiral longitudinally in the limbs and run transversely in the neck and trunk. Tension lines at the elbows, knees, ankles, and wrists are parallel to the transverse creases that appear when the limbs are flexed. Why are cleavage lines important to surgeons? They are an important consideration in surgery and if incisions are made in the direction of Langer lines they tend to heal better and produce less scarring than those that cross them.  Rule of nines According to the rule of nines, which gives a guide to the size of body parts in proportion to the whole: Head = 9% Upper limb = 9% Lower limb = 18% Front of thorax and abdomen = 18% Back of thorax and abdomen =18%; Perineum = 1%.  Fascia The fascia of the body is the tissue that lies between the skin and the underlying muscles and bones. It is divided into, superficial & deep layers: A. Superficial fascia: It is found immediately under the skin uniting it to the underlying deep fascia. It consists of a layer of loose connective tissue, which contains a variable amount of fat, blood vessels, lymphatics and nerves of the skin. It is extremely thin or absent in the eyelids, external ear, penis and scrotum.  Fascia Function of superficial fascia: Its fat content keeps the body temperature and fills up the hollows and irregularities so give the body a rounded contour especially in females. Also, it provides a depot for food storage and forms an insulating layer over the body retaining the heat. It acts as a distributing layer in which blood vessels, lymphatics and nerves can traverse to the dermis. It allows free mobility of the skin on the underlying structures. Contents of superficial fascia:  Superficial (subcutaneous) fat  Superficial vessels  Superficial nerves  Superficial lymphatics B. Deep fascia: Fascia Deep fascia is a dense, inelastic fibrous membrane, devoid of fat, which separates the superficial fascia from the deeper structures. It covers most of the body. However, it absent in certain regions e.g. in the face, scalp and anterior abdominal wall. It invests the muscles and other deep structures. In the limbs it forms a definite sheath around the muscles of similar functions and nerve supply and sends intermuscular septa that attach to bones to separate the muscle groups forming Fascial compartments.  Fascia B. Deep fascia: In certain sites, deep fascia is thickened for protection e.g. the palmar aponeurosis of the hand and plantar aponeurosis of the foot. Near some joints (e.g. wrist & ankle), it is thickened forming a retinaculum to hold tendons in place.  Bursae They are closed sacs or envelops of serous membrane which is a delicate connective tissue membrane capable of secreting fluid to lubricate a smooth internal surface. They are normally collapsed. They present in locations of friction allowing free movement. When fluid is secreted in excess, they become prominent which is a pathological condition. Types: Subcutaneous bursae between skin and bony prominences (elbow & knee) Subfascial bursae beneath deep fascia Subtendinous bursae facilitate movement of tendons over bone Synovial tendon sheaths elongated, wrap around tendons Clinical Notes  Skin Incisions and Scarring The skin is always under tension. Lacerations or incisions that parallel the tension lines usually heal well with little scarring because there is minimal disruption of collagen fibers. Laceration across the tension lines disrupts more collagen fibers. The disrupted lines of force cause the wound to gape, and it may heal with excessive (keloid) scarring.  Stretch marks in skin Skin can strech to accommodate gradual weight gain. Stretch marks can appear due to fast increase in size as in pregnancy causing damage in collagen fibers. Stretch marks are bands of thin wrinkled skin, initially red but later becoming purple or white—may appear on the abdomen, buttocks, thighs, and breasts.  Burns Causes thermal trauma, radiation, chemical agents. Classification:  1st degree superfiscial (sunburn), limited to epidermis erythema (hot & red skin), pain, edema (swelling), desquamation (peeling)  2nd degree partial thickness, epidermis & dermis (superficial or deep) blistering or loss, damage nerve endings, painful, contracture  3rd degree full thickness, entire thickness marked edema, numbness (sensory ending destroyed), require skin graft  4th degree entire skin thickness and fascia, muscle or bone life threatening Burns are classified as severe if they cover 20% or more of the total body surface area (excluding superficial burns like sunburn), are complicated by trauma or inhalation injury, or are caused by chemicals or high-voltage electricity.