SKIN AND APPENDAGES OF SKIN Dr Iram Tassaduq

THE INTEGUMENT The integument is the body’s most The integument is the body’s most massive organ. massive organ. It is composed of skin that covers It is composed of skin that covers the entire body, together with certain accessory organs which are derivatives of the skin, such as nails, hair, sweat and sebaceous glands. the entire body, together with certain accessory organs which are derivatives of the skin, such as nails, hair, sweat and sebaceous glands.

ESSENTIAL FUNCTIONS Acts as a barrier Provides immunologic information Participates in homeostasis Conveys sensory information Performs endocrine functions Functions in excretion

LAYERS OF SKIN

1. STRATUM BASALE/ STRATUM GERMINATIVUM Single layer of cells Cuboidal / Columnar cells Closely spaced nuclei Basophilic cytoplasm Contains melanin Cell junctions Contains stem cells Provides epidermal cell renewal

2. STRATUM SPINOSUM Several cells thick Larger cells Cytoplasmic processes or spines Desmosomes Prickle cells Flattening of cells towards surface

3. STRATUM GRANULOSUM Most superficial layer of nonkeratinized portion of epidermis One to three cell layers thick Keratohyalin granules

4. STRATUM LUCIDUM A subdivision of stratum corneum Normally well seen in thick skin Refractile appearance Stains poorly Eosinophilic cells

5. STRATUM CORNEUM Cells are flattened, desiccated, anucleated Most differentiated cells in the skin Filled almost entirely with keratin filaments Thick plasma membrane Water barrier in epidermis Variation in the thickness of layer

Dermis varies from 0.2 to 4 mm in thickness Composed of dense, irregularly arranged C.T. Contains three types of C.T. fibres plus fibroblasts and macrophages Two layers can be distinguished Junction between dermis and epidermis

LAYERS OF DERMIS 1. THE PAPILLARY LAYER Consists of loose C.T. Thickness of collagen fibres Contains type I and type III collagen Irregular network of elastic fibres Dermal papillae and ridges Blood vessels Nerve processes

THE RETICULAR LAYER Always considerably thicker and less cellular than the papillary layer (although its thickness varies) Characterized by thick irregular bundles of mostly type I collagen and by coarse elastic fibres Langer’s lines

THIN HAIRY SKIN THICK NONHAIRY SKIN

FLEXOR OR JOINT LINES Major markings found in the vicinity of synovial joints where the skin is attached strongly to underlying deep fascia. Prominent on the flexor surfaces of palms, soles and digits. Skin lines don't necessarily coincide with the underlying joint line.

PAPILLARY/EPIDERMAL/FRICTON/RIDGES A friction ridge is a raised portion of the epidermis on the fingers and toes, the palm of the hand or the sole of the foot.

WRINKILE LINES Caused by contraction of underlying muscles, present perpendicular to their axis of shortening. On face, they are known as lines of facial expression, aging makes them permanent due to loss of skin elasticity.

BLOOD SUPPLY OF SKIN The dermis contains horizontally arranged superficial and deep plexuses, which are interconnected via communicating vessels oriented perpendicular to the skin surface.

INNERVATION OF SKIN

APPENDAGES OF SKIN Nails Hair follicles Sweat glands Sebaceous glands

HAIR Hairs are elastic keratinized threads that develop from epidermis Has free shaft and root embedded in skin Length: 1 mm. to 5 feet Humans: hair covers entire body except: palm, sole, region of anal & urogenital apertures

Hair Bulb

NAILS The nails are horny plates that form a protective covering on the dorsal surface of the terminal phalanges of the fingers and toes

SWEAT GLANDS(SUDIFEROUS GLANDS widely distributed on body Sweat – is a blood filtrate 99% water with some salts Contains traces of metabolic wastes Vital for thermoregulation Also influence water and ion balance

SEBACOUS GLANDS One to several sebaceous glands always connect with a hair A gland usually is located in the angle between the follicle and its muscle Its short duct empties into the follicle at a level three- fourths of the way up.

Occur over entire body Except palms and soles Secrete sebum – an oily substance Simple alveolar glands Most are associated with a hair follicle Functions of sebum Collects dirt; softens and lubricates SEBACOUS GLANDS