Integumentary System - Skin, Nails, Glands, Hair PDF

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Summary

Notes from integumentary system lecture...

Description

Integumentary System The integumentary system is composed of the nails, skin, sweat glands, hair, oil and sensory receptors. The structure of the skin is made of 2 main parts: - The Epidermis o The Epidermis is the superficial thinner portion which is composed of epithelial tissue. - The Dermis o The Dermis is the thicker portion and is made of dense irregular connective tissue.

Below the Dermis but not part of the skin is the Subcutaneous (hypodermis)

Figure 1: Structure of the Integumentary System The Epidermis

The Epidermis is composed of keratinized stratified (multiple layers) squamous (flattened) epithelium

The Epidermis contains 4 principal types of cells: - Keratinocytes o Make up 90% of the epidermal cells and are arranged in 4-5 layers and produce Keratin. Within Keratinocytes are lamellar granules which release lipid rich secretion that acts as a water-repellent sealant. Which prevent loss of body fluids and entry of foreign materials. -

Melanocytes o Make up 8% of the cells and produce the pigment melanin

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Intraepidermal Macrophages o (Langerhans Cells) Participate in Immune Responses

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Tactile Epithelial Cells o Responsible for Touch Sensations

Keratinization is the process of newly formed cells in the stratum basale which are slowly pushed to the surface. As the cells move from one epidermal layer to the next, they accumulate more and more keratin. Eventually the keratinized cells are disposed and replaced by underlying cells. Layers of the Epidermis The epidermis that has 4 strata layers make up the thinner types of skin: - Stratum Basale – Deepest Layer - Stratum Spinosum – Provides strength & Flexibility - Stratum Granulosum – Keratinocytes undergo apoptosis (genetic programmed cell death) - Stratum Corneum – Most Superficial Layer The epidermis that has 5 strata layers make up the thicker types of skin found on your palms and soles. - Stratum Lucidum – Only found in thick skin and is located between Granulosum & Corneum

Figure 3: Layers of the Epidermis The Dermis The deeper part of the skin and is composed mainly of connective tissue which contains collagen and elastic fibres. The superficial part of the dermis is about one-fifth of the thickness of the total layer, it consists of areolar connective tissue which contain elastic fibres. Its surface area is increased by small finger like projections called dermal papillae, touch receptors and fine nerve endings.

The deeper part of the dermis, which is attached to the subcutaneous layer, consists of dense irregular connective tissue which contain bundles of collagen and coarse elastic fibres. Adipose cells, hair follicles, nerves, oil glands and sweat glands are found between fibres. Melanin, Haemoglobin and Carotene are three skin pigments that make up the skins colour. Melanin is responsible for the skin colour to vary between pale yellow to – reddish-brown – black.

Figure 4 : Sectional view of skin and subcutaneous layer Accessory Structures of the Skin Accessory structures of the skin that develop from the epidermis are hair, glands and nails. Hair and Nails protect the body, while sweat glands regulate body temperature. Hair (pili) are present on most skin surfaces except the palms, palmar surfaces of the fingers, soles and plantar surfaces. Hair is a thread of fused, dead, keratinized epidermal cells that consist of a shaft (superficial) and a root (in the dermis) and the follicle. Associated with hair are bundles of smooth muscle called arrector pili & sebaceous gland (oil glands). Sebaceous glands are usually connected to hair follicles, there job is to produce sebum which moistens hair and waterproofs skin. Hair colour is a result of melanin. Grey Hair occurs with a decline of melanin while White hair results from the accumulation of air bubbles in the hair shaft.

Glands A single or group of epithelial cells that secrete a substance. The glands associated with the skin include: - Sebaceous Glands – secrete sebum (on oily substance) that keeps hair from drying out. Sebum also keeps the skin soft and inhibits certain bacteria. -

Ceruminous Glands – found in the outer ear canal secrete a yellowish substance called cerumen (ear wax)

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Sudoriferous (Sweat Glands) o Apocrine - found in the skin of the axilla (armpit), groin, areolae (skin surrounding nipples) and the bearded regions of the face in adult males. o

Eccrine - are distributed throughout most of the body, especially the forehead, palms and soles.

Nails Are hard, dead, keratinized epidermal cells that cover the terminal portions of the fingers and toes. The nail is made up of the following parts: - Nail Body - Free Edge - Nail Root - Lunula - Cuticle - Nail Matrix The Nail Matrix is the proximal portion of the epithelium that is deep to the nail root. Cell division of the matrix cells produce new nails.

Functions of the Skin The skin has 5 major functions: - Body Temperature Regulation - Protection – Keratin in the skin protects underlying tissues from microbes, abrasion, heat and chemicals. Lipids released by lamellar granules inhibit evaporation of water from the skin surface. - Cutaneous Sensations - tactile sensations (touch, pressure, vibration and tickling), thermal sensations (warmth and coolness) and pain. - Excretion and absorption - Synthesis of Vitamin D Body Temperature Regulation – the skin contributes to homeostatic regulation of the body temperature by liberating sweat at its surface and by adjusting the flow of blood in the dermis

Aging and The Integumentary System Most age-related changes occur around the 40’s and occur within the protein in the dermis. - Collagen fibres – decrease in number, stiffen, break apart and disorganize into a shapeless, matted tangle - Elastic fibres – loose elasticity, thicken into clumps and fray. This is greatly accelerated by smokers. - Fibroblasts – which produce collagen and elastic fibres, decrease in number which results in wrinkles.

Moles

Burns

Rule of Nines

The rule of nines assesses the percentage of burn and is used to help guide treatment decisions.

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