Ch. 4 Skin and Body Membranes

Epithelial Membranes Cutaneous membrane (skin) (a) Cutaneous membrane (the skin) covers the body surface. Figure 4.1a

Epithelial Membranes Mucous membranes (mucosa) Line body cavities that open to exterior (e.g., digestive and respiratory tracts) Mucosa of nasal cavity Mucosa of mouth Esophagus lining Mucosa of lung bronchi Figure 4.1b

Epithelial Membranes Serous Membranes Paired membranes that line closed ventral body cavities Parietal layer –lines body walls Visceral layer- covers internal organs Serous Membranes are named based on their location: Pleural membranes surround: lungs Pericardial membranes surround: heart Peritoneal membranes surround: viscera

Epithelial Membranes Parietal peritoneum Parietal pleura Visceral pericardium Visceral pericardium Figure 4.1c

Skin (Integument) Consists of three major regions Epidermis—superficial region Dermis—middle region Hypodermis —deepest region Mostly adipose tissue

Epidermis Papillary layer Dermis Reticular layer Hypodermis

Epidermis Keratinized stratified squamous E.T. Cells of epidermis Keratinocytes—produce fibrous protein keratin Melanocytes Produce brown pigment melanin

Layers of the Epidermis: Stratum Basale Deepest epidermal layer firmly attached to dermis One cell layer Mitotic cells that travel from basal layer to surface Takes 25–45 days Contains melanocytes

Layers of the Epidermis: Stratum Spinosum ~5-6 cell layers Living, flatter cells Mostly filled with keratin

Layers of the Epidermis: Stratum Granulosum 2-3 cell layers Living cells Mostly filled with keratin

Layers of the Epidermis: Stratum Lucidum A few rows of flat, dead keratinocytes Thin, transparent band superficial to the stratum granulosum Only in soles and palms

Layers of the Epidermis: Stratum Corneum 20–30 rows of dead, flat, keratinized cells 3/4 of the epidermal thickness Protects from abrasion and penetration & waterproofs the skin

Keratinocytes Stratum corneum Stratum granulosum Stratum spinosum Stratum basale Dermis Sensory nerve ending Melanin granule Epidermal dendritic cell Melanocyte Tactile (Merkel) cell (b) Figure 5.2b

Dermis Made up of Two layers: Papillary Layer Reticular Layer Composed of areolar C.T. Reticular Layer Composed of dense irregular C.T.

Epidermis Papillary layer Dermis Reticular layer Hypodermis

Layers of the Dermis: Papillary Layer Contains dermal papillae which may have: Capillary loops Meissner’s Corpuscles Free nerve endings

Hair shaft Dermal papillae Epidermis Subpapillary vascular plexus Papillary layer Pore Appendages of skin Dermis Reticular layer • Eccrine sweat gland • Arrector pili muscle Hypodermis (superficial fascia) • Sebaceous (oil) gland • Hair follicle Nervous structures • Hair root • Sensory nerve fiber Cutaneous vascular plexus • Pacinian corpuscle • Hair follicle receptor (root hair plexus) Adipose tissue

Layers of the Dermis: Reticular Layer Most glands, hair follicles, emerge from the dermis

Skin Color Three pigments contribute to skin color: Melanin Carotene Yellow to reddish-brown to black, responsible for dark skin colors Carotene Yellow to orange, most obvious in the palms and soles Hemoglobin Responsible for the pinkish hue of skin

Appendages of the Skin Appendages are derived from the epidermis Sweat glands Oil glands Hairs and hair follicles Nails

Sweat Glands Two main types of sweat glands Eccrine sweat glands—abundant on palms, soles, and forehead Sweat: 99% water, NaCl, vitamin C, antibodies, metabolic wastes Ducts connect to pores Thermoregulatory function

Sweat pore Eccrine gland Sebaceous gland Duct Dermal connective tissue Secretory cells

Sweat Glands Apocrine sweat glands—confined to axillary and anogenital areas Sebum: sweat + fatty substances and proteins Ducts connect to hair follicles Functional from puberty onward

Sebaceous (Oil) Glands Most develop from hair follicles Secrete Sebum: Oily secretion Bactericidal Softens hair and skin

Sweat pore Sebaceous gland Dermal connective tissue Eccrine Sebaceous gland duct Eccrine gland Hair in hair follicle Secretory cells Figure 4.6

Hair Functions Alerts the body to presence of objects on the skin Guards the scalp against physical trauma, heat loss, and sunlight Consists of three layers of squamous keratinocytes: cuticle (outermost layer), cortex, medulla Surrounded by a hair follicle

Follicle wall Hair shaft Hair • Cuticle • Cortex • Medulla Arrector pili Sebaceous gland Hair root Hair bulb

Hair Follicle Two layered wall consisting of CT and ET Hair bulb: expanded deep end Hair follicle receptor (root hair plexus): Sensory nerve endings around each hair bulb

Hair Follicle Arrector pili Smooth muscle attached to follicle Contraction of these muscles causes the hairs to stand on end (forming “goose bumps”)

Subcutaneous adipose tissue (c) Hair shaft Arrector pili Sebaceous gland Hair root Follicle wall Hair bulb Hair root • Cuticle • Cortex • Medulla Hair matrix Hair papilla Melanocyte Subcutaneous adipose tissue (c) Figure 4.7

Structure of a Nail Scalelike modification of the epidermis Structures of the nail: Free edge, body, nail matrix, nail bed, hyponichium, eponichium,

Lateral nail fold Lunule (a) Free edge of nail Body of nail Eponychium (cuticle) Proximal nail fold Nail bed Root of nail Nail matrix (b) Hyponychium Phalanx (bone of fingertip)

Functions of the Integumentary System Protection Chemical Low pH secretions retard bacterial activity Physical/mechanical barriers Keratin and glycolipids block most water and water- soluble substances Biological barriers Macrophages

Functions of the Integumentary System Body temperature regulation At elevated temperature, dilation of dermal vessels and increased sweat gland activity cool the body Cutaneous sensations Temperature, touch, and pain

Functions of the Integumentary System Metabolic functions Synthesis of vitamin D precursor Blood reservoir—up to 5% of body’s blood volume Excretion—nitrogenous wastes and salt in sweat

Basal Cell Carcinoma Least malignant, most common Appearance: Red, shiny, raised nodule Stratum basale cells proliferate and slowly invade dermis and hypodermis Cured by surgical excision in 99% of cases

Squamous Cell Carcinoma Second most common Appearance: flat and scaly Involves keratinocytes of stratum spinosum Good prognosis if treated by radiation therapy or removed surgically

Melanoma Most dangerous type Appearance: black/brown spreading patch; may develop from pre-existing moles Highly metastatic and resistant to chemotherapy; most dangerous Treated by wide surgical excision accompanied by immunotherapy

Melanoma Characteristics (ABCD rule) A: Asymmetry; the two sides of the pigmented area do not match B: Border exhibits indentations C: Color is black, brown, tan, and sometimes red or blue D: Diameter is larger than 6 mm (size of a pencil eraser)

Partial-Thickness Burns First degree Epidermal damage only Localized redness, edema (swelling), and pain Second degree Epidermal and upper dermal damage Blisters appear

1st degree burn 2nd degree burn (a) Skin bearing partial thickness burn (1st and 2nd degree burns)

Full-Thickness Burns Third degree Entire thickness of skin damaged Gray-white, cherry red, or black No initial edema or pain (nerve endings destroyed) Skin grafting usually necessary

3rd degree burn (b) Skin bearing full thickness burn (3rd degree burn)