Skin appendages

Anatomy

1. Skin appendages Maryam Fida (o-1827)

2. Integumentary system Skin Appendages (specialized derivatives of skin) Hairs Nails Sebaceous glands Sweat glands

3. THE HAIR Hairs are elastic keratinized threads , vary in thickness Derived from an invagination of the epidermis Consist of two portions: Shaft & Root The shaft projects above the skin surface The root is embedded in the skin Hair root is surrounded by Hair Follicle Hair follicle consist of epidermal (epithelial) & dermal (connective tissue) elements Deep end of hair follicle expanded to form Hair bulb

4. Hair follicle is associated with: Sebaceous glands Arrector pili muscle (smooth muscle)  goose flesh Growth of hair, average rate 2 mm per week The production & growth depends upon the hair follicle that surrounds the root of the hair Color of the hair depends on the quantity of melanin pigment & amount of air in the hair substance

5. Hair shaft  consist of epithelial cells arranged in three regions Medulla (moderately keratinized cuboidal cells) Cortex (main bulk, heavily keratinized cells) Cuticle (single layer of flattened keratinized cells)

6. NAILS Hard, translucent, roughly rectangular plates Highly keratinized epithelium Covers the dorsal aspect of terminal phalanges Nail plate consist of: Body, Free Edge & Root Lunula (crescent-shaped whitish area) Each nail plate rests on a nail bed (skin under the nail)

7. Nail bed consist of stratum basale Epidermis (stratum basale ) of nail bed is very thick proximally and is called Nail Matrix Nail matrix is responsible for the growth of nail, exhibit high rate of cell division Growth of fingernails is 0.5 mm per week & growth of toenails is 1 mm per month Nail keratin is hard keratin  do not desquamate

8. SEBACEOUS GLANDS Sebaceous glands are usually associated with hair Located between a hair follicle and its arrector pili muscle in the dermis.

9. There are mitotically active cells giving rise to the larger sebum-producing cells in the center of the gland  accumulate fat ultimately breakdown to produce sebum Most abundant in the face and scalp, completely absent in the skin of palm and soles Function  maintenance of proper skin texture & hair flexibility . In addition, sebum may possess weak antifungal & antibacterial properties

10. Sweat glands Classified into two types Eccrine sweat glands Apocrine sweat glands Eccrine sweat glands are distributed over whole body Apocrine sweat glands are limited to certain specific regions of the body e.g. axilla

11. ECCRINE SWEAT GLANDS Simple tubular glands Abundant in the skin of palms and soles Terminal secretory portion of sweat gland is coiled and lie in dermis Sweat pore Lined by simple cuboidal epithelium Secretion is produced in response to heat and nervous strain

12. Sweat is a clear liquid, derived from blood capillaries and consist of water, potassium, sodium, chloride, urea, ammonia, uric acid & lactic acid Functions: Temperature regulation Source of excretion of waste products like ammonia, urea and uric acid

13. Which of the following is composed of loose connective tissue? a. Epidermis b. Reticular layer of dermis c. Hypodermis d. Both a and b e. Both b and c

14. A new miracle skin cream recently hit the beauty counters which is suppose to stimulate collagen production. Which cell is it supposedly stimulating? a. Langerhans cell b. Keratinocyte c. Melanocyte d. Merkel cell e. Fibroblast

15. What is the growing part of the nail? a. Lunula b. Eponychium c. Matrix d. Nail bed e. Root

16. Which cell is the most abundant cell in the epidermis? a. Langerhans cell b. Keratinocyte c. Melanocyte d. Merkel cell e. Fibroblast

17. Which cell is a mechanoreceptors? a. Langerhans cell b. Keratinocyte c. Melanocyte d. Merkel cell e. Fibroblast

18. Which layer of the epidermis is also called the stratum germinativum ? a. Stratum basale b. Stratum spinosum c. Stratum granulosum d. Stratum lucidum e. Stratum corneum

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