Skin Structure and Functions (PDF)

## Answer: ### 1. Give a short note on the structure and functions of the skin. ### Structure of skin: #### A) Epidermis: * Formed of 2 layers: * Horny layer: Superficial water-proof keratin layer. * Germinative layer: Deeper stratified squamous epithelium. #### B) Dermis: * Formed of 2 l...

## Answer: ### 1. Give a short note on the structure and functions of the skin. ### Structure of skin: #### A) Epidermis: * Formed of 2 layers: * Horny layer: Superficial water-proof keratin layer. * Germinative layer: Deeper stratified squamous epithelium. #### B) Dermis: * Formed of 2 layers: * Superficial papillary layer. * Deep reticular layer. It contains: * Fibers: Collagen & elastic. * Vessels: Blood vessels & lymphatics of skin. * Nerves: For skin sensation. * Root of hair: With erector pili muscles and sebaceous glands * Sweat glands: Coiled tubular glands that secrets sweat which helps regulation of body temperature. ### Functions of Skin: 1. Protection: Against micro-organisms, trauma and U.V. rays of sun. 2. Keep body fluid: Preventing dehydration. 3. Regulate body temperature: By sweat glands and superficial blood vessels. 4. Synthesis: Of vitamin D. 5. Sensation: Necessary for protection of body. ## Answer: ### 2. Give a short note on the skin appendages. #### Skin appendages: 1. Hair: Primary (Lanugo) and permanent. 2. Nails: Developed from epidermis and formed of root, body and free border. 3. Sebaceous glands: Fatty glands that open into hair follicles. 4. Sweat glands: Coiled glands that open into the surface of epidermis. ## Answer: ### 3. Give a short note on the skin pigments. 1. Melanin: * Brown-black in color, present in melanocytes at dermo-epidermal junction. * Melanocytes synthesize and store a Brown pigment, melanin, that gives the tissue a dark color. Melanocytes are common in the epithelium of the skin, where they play a major role in determining skin color. 2. Carotene: * Yellowish in color, present in cells of epidermis. 3. Hemoglobin: * Pinkish in color, is an oxygen-binding found in red blood cells. The oxygenated blood flowing through superficial dermal vessels gives the skin its pinkish appearance. ## Answer: ### 6. Mention the main differences between epithelium and connective tissue. (Table) | Feature | Epithelium | Connective Tissue | |--------------|-------------|-------------------| | Development | From the 3 germ layers | From the mesoderm | | Cells | Closely packed | Widely separated | | Matrix | Minimal | Abundant | | Free surface | Usually present | Has no free surface | | Basement membrane | Present | Absent | | Vascularity | Avascular | Highly vascular (except hyaline cart.) | | Classification | 1 - Covering or lining | 1 - CT proper (non-specific) | | | 2 - Glandular | 2 - Specific CT (bone, cartilage, blood) | | | 3 - Neuroepithelium | | | | 4 - Myoepithelium | | | Example | Epidermis of skin | Dermis of skin | ## Answer: ### 7. Mention the main differences between superficial and deep fasciae. (Table) | Feature | Superficial Fascia | Deep Fascia | |---------|---------------------|-------------| | Site | Deep to skin | Around muscles, glands and vessels. | | Nature | Loose areolar C.T. rich with fat which is variable according to age, sex or nutrition. It is dense in scalp, thin in dorsum of hand. It may be composed of 2 layers. | Dense C.T. rich with collagenous fibers. It has variable forms according to site and function needed. | | Functions | - Heat insulator. | - Gives sheathes around muscles. | | | - Reservoir of fat. | - Gives intermuscular septa to separate and give more attachment of muscles. | | | - Medium for vessels and nerves. | - Formation of interosseous membrane. | | | - Easy movements of skin. | - Formation of retinacula. | | | - Contains glands or muscles. | - Formation of aponeurosis. | | | - Gives soft pads to different parts of the body. | - Formation of pulley around tendon. | | | | - Formation of check ligaments. | | | | - Formation of sheaths around glands and blood vessels. | | | | - Formation of ligaments. |