Skin, Fascia, Muscles PDF

SKIN, FASCIA, MUSCLES  THE SKIN The largest organ in the body The outer layer covering the body Divided into 2 parts: I.EPIDERMIS: - Keratinized stratified squamous epithelium. -Formed of several layers of cells. -Uppermost layer is thick and formed of keratinized cells. -Basal...

SKIN, FASCIA, MUSCLES  THE SKIN The largest organ in the body The outer layer covering the body Divided into 2 parts: I.EPIDERMIS: - Keratinized stratified squamous epithelium. -Formed of several layers of cells. -Uppermost layer is thick and formed of keratinized cells. -Basal layer contains melanocytes to form melanin pigments. -Ectodermal in origin Thick epidermis: - Palms of the hands Soles of the feet - To withstand the wear and tear that occurs in these regions. -Thin epidermis: Anterior surface of the arm and forearm II. DERMIS: - Deep connective tissue layer. - Contains many blood vessels, lymphatic vessels and nerves. -Mesodermal in origin -Thinner: - on anterior than posterior surface and in women than on men - Connected to the underlying deep fascia or bones by superficial fascia (subcutaneous tissue). Appendages Of The Skin: 1. Nails 2. Hair follicles 3. Sebaceous glands 4. Sweat glands - Nails: Keratinized plates on dorsal surfaces of tips of fingers and toes. Has root of the nail, nail folds and nail bed Hairs: - Hair follicles - Hair bulbs - Hair papilla. Sites Of Skin Having No Hairs: 1. Lips 2. Palms of the hands 3. Sides of the hands 4. Sides of fingers 5. Sole of the feet 6. Sides of the feet 7. Sides of the toes 8. Glans penis 9. Clitoris 10. Labia minora 11. Internal surface of the labia majora Sebaceous Glands: - Pours sebum (oily material) helps preserve flexibility of emerging hair and oils surface of epidermis around mouth of follicle. Sweat Glands: Most deeply penetrating structure of all epidermal appendages. Sites Of Skin Having No Sweat Glands: 1. Red margin of the lips 2. Nail beds 3. Glans penis 4. Clitoris Rule Of Nines: Burns 9% head and neck 18% upper limbs (9X2) 36% lower limbs (18X 2) 18% front of the trunk 18% back of the trunk 1% external genitalia ……………………………………… 100% Total Skin Creases: The skin is thinner at these sites than elsewhere and is firmly attached to underlying structures by fibrous tissue. Finger Prints: - Dermatoglyphics Langer’s (cleavage) lines: - The bundles of collagen fibres are mostly arranged in parallel rows. - Their direction is called lines of cleavage or Langer’s lines. - They tend to run longitudinally in the limbs and circumferentially in the neck and trunk. Function of The Skin: 1. Protection: of the body from environmental effects such as abrasions, fluid loss, ultraviolet radiations, micro-organisms 2. Sensation (pain, temperature, touch) by way of superficial nerves and their sensory endings 3. Heat-regulation: through evaporation of sweat and/or dilation or constriction of superficial blood vessels. 4. Synthesis and storage of vitamin D. 5. Containment for the body’s structures (tissues and organs) and vital substances (extra-cellular fluids) preventing dehydration. Skin Ligaments (Retinacula Cutis): - They extend from deep surface of dermis to underlying deep fascia. - Their length and density determines mobility of skin over deep structures; more mobile on back of hand than its palm. FASCIAE  FASCIAE They lie between the skin and underlying muscles and bones. I. SUPERFICIAL FASCIA (SUBCUTANEOUS TISSUE): Mixture of loose areolar and adipose tissues, unites dermis of the skin to underlying deep fascia. Consists of: 1. Superficial fatty layer 2. Deep membranous layer - Main factor responsible for smooth external contour of female. Sites of superficial fascia having numerous bundles of collagen fibres (dense C.T.): 1. Scalp 2. Back of the neck 3. Palms of the hands 4. Sole of the feet Sites of superficial fascia devoid of adipose tissue: 1. Eyelids 2. Auricle of the ear 3. Penis 4. Scrotum 5. Clitoris 6. Nipple and areola of the breast Functions of Superficial Fascia: 1. Acts as a distributing layer in which blood vessels, lymphatics and nerves can travel before entering the dermis. 2. Allows for mobility of the skin on underlying structures particularly over the joints since its loss as in severe burns can lead to restriction of movement. 3. Provides a depot for food storage. 4. Forms a useful insulating layer over body.  II.DEEP FASCIA: Membranous layer of connective tissue that invests muscles and other deep structures. Different forms and names of deep fascia: - In some places, it splits to enclose structures as glands; submandibular and parotid glands. - In anterior wall of axilla, it forms clavipectoral fascia. - Extensions of the investing layer pass deeply to form intermuscular septa and sheaths for neurovascular bundles such as axillary sheath. - In thorax and abdomen, it is merely a thin film of areolar tissue covering the muscles and aponeurosis. - It is replaced by membranous layer of superficial fascia (Scarpa’s fascia). - In thigh, it is called fascia lata and thickened on lateral side of thigh to form iliotibial tract. - In region of the joints, it is thickened to form bands (retinacula) to hold the underlying tendons in position or to serve as pulleys around which the tendons may move - Deep fascia, contracting muscles and venous valves work together as musculo-venous pump to return blood to heart, as in lower limbs where blood must move against pull of gravity. MUSCULAR SYSTEM  MUSCULAR SYSTEM Muscles represent fleshy tissue of the body which have a power of contraction. TYPES OF MUSCLES: I. VOLUNTARY, SKELETAL, STRIATED: 1. Under control of will and desire voluntary Controlled by special nerve or nerves which connect them to central nervous system, 2. Attached either origin or insertion to skeleton, skeletal 3. Composed of groups of parallel bundles of muscle fibers, striated or stripped. 4. Represent more than 40% of whole body weight. 5. Total number is 620 muscles all over the body. Structure of Voluntary Muscles: Origin: Beginning part of the muscle - Rigid and less mobile part - Single or multiple Insertion: Terminal mobile part Attached to bone, skin, cartilage or contralateral muscle; lumbricals, levator ani Belly of the muscle: Fleshy part of the muscle Tendon of the muscle: Non-fleshy part by which the muscle is commonly inserted. Forms of tendons: 1. Cord-like 2. Sheet-like (aponeurosis) 3. Raphe: interdigitate fibers Forms of Voluntary Muscles: (According to shape and arrangement of fibers):- 1- Strap or parallel muscles: Parallel fibers; sartorius 2- Quadrate muscle: Quadrangular in shape; pronator quadratus 3- Triangular muscle: Triangular in shape; temporalis 4- Fusiform muscle: Spindle-shaped; biceps, flexor carpi radialis 5- Pennate muscle: Fibers, in oblique direction, feathery shape, taking many forms: a. Uni-pennate: Its fibers come from one side of a tendon; flexor pollicis longus b. Bi-pennate: Its fibers come from both sides of a tendon; rectus femoris c. Multi-pennate: Series of bi-pennate fibers lie side by side; deltoid muscle d. Circum-pennate: Fibers come from central tendon in different directions; tibialis anterior MUSCLE TONE - When resting, every skeletal muscle is in a partial state of contraction (muscle tone). - Dependant on integrity of monosynaptic reflex arc, composed of 2 neurons in nervous system. - Nervous impulses travel in afferent neurons to spinal cord and synapse with anterior horn cells to give impulses along their axons (efferent) to muscle fibers. - Cut reflex arc leads to paralysis of the muscle. MOTOR UNIT: Motor neuron and all the muscle fibers supplied by it. - Gluteus maximus; motor neuron supplies about 200 muscle fibers. - Small muscles of the hand, extrinsic muscles of the eyeball, one nerve fiber supplies few muscle fibers. MUSCLE MOVEMENT: All movements are the result of coordinated action of many muscles Muscle Action; muscles may work in:- 1. Prime mover: The chief muscle or a member of a chief group of muscles responsible for particular action; quadriceps femoris is a prime mover in extension of the knee. 2. Antagonist: Any muscle opposes action of prime mover; biceps femoris opposes action of quadriceps femoris.  3. Fixator: Muscle contracts isometrically (increase tone of the muscle but no movement) to stabilize action of prime mover. - Muscles attaching shoulder girdle to trunk contract as fixators to allow deltoid to act on shoulder 4. Synergist: - To prevent unwanted movements in intermediate joints when the prime mover crosses number of joints before reaching the joint where its main action takes place. - Flexor and extensor muscles of carpus contract to fix wrist joint to allow flexor and extensor muscles of fingers to work efficiently. MOTOR POINT: - Place of entrance of nerve to the muscle, about mid-point of its deep surface MOTOR END PLATE: - Each motor fibre ends by dividing into branches. - Each branch and muscle fibers supplied by it are called motor end plate II. UNVOLUNTARY, UNSTRIPPED, SMOOTH PLAIN GROUP: Less common than voluntary Characters of involuntary group: 1. Not controlled by will 2. Lies under control of autonomic nervous system 3. Not attached to bones 4. Their fibers are smooth, plane, not stripped 5. They contract and relax in ring fashion (peristalsis) Examples: Smooth muscles in wall of gastrointestinal tract, respiratory tract, urinary and genital systems and wall of the blood vessels III- THE CARDIAC MUSCLE: - Single and the most important muscle in the body Characters of cardiac muscle: 1. Not voluntary 2. Not smooth 3. Single 4. Contracts in rhythmic fashion (pumping)