Ch6 Ppt Lect
Transcript of Ch6 Ppt Lect
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Chapter 6
Skin and the Integumentary System
PowerPoint Presentation to accompany Hole’s Human Anatomy and Physiology, 10th edition, edited by S.C. Wache for Biol2064.01
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You are responsible for the following figures and tables:
Fig. 6.1 - skin consists of CT and ET.ET - stratified squamous epitheliumCT - irregular dense connective tissueET - glandular epitheliumCT - adipose tissueRead TB, p.159-164 on 'epidermis', 'dermis', 'subcutaneous layer'.Tab. 6.1 - Layers of the EpidermisFig. 6.2 - Skin.Fig. 6.4 - Melanocytes.Fig. 6.7 - Nails.Fig. 6.9 - Eccrine and apocrine sweat glands. Hair.Read on cuts and burns, TB, pp. 173-175. Which epidermal layer has regenerative function ?Fig. 6.13 - Wound Healing.Fig. 6.14 - Extent of skin damage.
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Epithelial Membranes (EM)
• There are three types of EM:
Serous / Mucous / Cutaneous
• The skin or cutaneous epithelial membrane, consisting of layers of ET called the epidermis and a layer of CT called the dermis, is an organ of the integumentary system.
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Cutaneous Membrane = Skin
• Skin contains two layers, the epidermis and the dermis.
• The hypodermis is the layer underneath the skin.
Figure 6.2
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Cutaneous Membrane
• Beneath the dermis is loose connective and adipose tissue that binds the skin to underlying organs. This is the hypodermis / subcutaneous layer.
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Cutaneous Membrane Function• Skin is a protective covering that prevents
harmful substances from entering the body.
• It helps regulate body temperature and water loss.
• It houses sensory receptors and contains immune system cells.
• It synthesizes chemicals and excretes some wastes.
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Epidermis
• It is composed of stratified squamous epithelium (ET).
Figure 6.3
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Epidermis
• It is composed of stratified squamous epithelium (ET) and a simple basal layer of cuboidal cells.
• It lacks blood vessels, but the deepest layer, the stratum basale, is close to the dermis and receives nutrients.
• The thickness of the epidermis varies with region of the body.
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Layers of the Epidermis from deepest to top layer
• Stratum basale: deepest layer, single row of cells that divide and grow
• Stratum spinosum: flat cells specialize and synthesize keratin
• Stratum granulosum: flat keratinized cells mature and nuclei appear shriveled
• Stratum lucidum: clear cells• Stratum corneum: many layers of flat, dead, keratinized,
nonnucleated cells that are shed
* The epidermis, like most epithelial tissues, regenerates. Epidermal cells exhibit high mitotic activity. They divide, grow, and die, while the new cells are already progressing through the same process.
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Melanin – A Pigment• It is a dark
pigment produced by melanocytes in the basal layer.
• Melanin absorbs UV light and prevents mutations and damage to cells. Figure 6.4
basal layer
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Skin CancersClinical Applications 6.1 (textbook p. 163)
Problem: Need balance between too much UV and
skin cancer and too little UV and Vit. D deficiency
due to lack of Vit. D synthesis in the absence of
sunlight.
Types of Skin Cancers:
Squamous cell carcinoma
Basal cell carcinoma
Malignant melanoma
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Carcinoma: a malignant tumor of epithelial origin
Melanoma: a benign or malignant skin tumor containing dark pigment;sometimes it is a tumor of high malignancy that starts in melanocytes of normal skin or moles and metastasizes rapidly and widely -- called also malignant melanoma, melanocarcinoma, melanoepithelioma, melanosarcoma
Sarcoma: a malignant neoplasm arising from connective tissue, bone, cartilage, or striated muscle that spreads by extension into neighboring tissue or by way of the bloodstream
From: http://www.nlm.nih.gov/medlineplus/mplusdictionary.html
Skin Cancers and Other Cancers
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Dermis Structure• The dermis is separated from the epidermis by the
basement membrane.• Epidermal ridges = dermal papillae project into the
dermis. These dermal papillae are responsible for fingerprints.
• The dermis binds the epidermis to the underlying tissues.
• The dermis is composed of irregular dense connective tissue with collagen and elastin in a gel-like ground substance.
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Dermis Function• Dermis contains muscle fibers. Smooth
muscles are associated with follicles and glands.
• Motor and sensory nerves and sensory receptors are found throughout the dermis.
• The dermis contains blood vessels, hair follicles, sebaceous and sweat glands.
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Subcutaneous Layer • The subcutaneous layer or hypodermis is made up
of loose connective tissue and adipose tissue.
• Collagenous and elastic fibers are continuous with those in the dermis.
• The adipose tissue conserves body heat.
• The subcutaneous layer contains the major blood vessels that supply the skin with oxygen, nutrients, and immune cells.
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Accessory Organs: Hair Follicles• Hair develops
from epidermal cells at the base of the hair follicle.
• Epidermal cells keep dividing continuously, grow, and die. Figure 6.6
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Hair Follicles
• Hair develops from epidermal cells at the base of the hair follicle.
• Epidermal cells keep dividing continuously, grow, and die.
• The dead cells make up the shaft of the hair.
• The arrector pili muscle is a smooth muscle attached to the follicle.
• It causes hair to stand upright on the skin.
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Accessory Organ: Nails
• consist of nail plate over a growing epithelium of the nail bed on the skin surface.
Figure 6.8
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Nails
• Nails consist of a nail plate over a growing epithelium of the nail bed on the skin surface.
• The white lunula at the base of the nail is the region of most active growth.
• Epithelial cells divide and become keratinized.
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Sweat Glands
• These glands respond to increased body temperature and
function in evaporative cooling.
Figure 6.10 – Eccrine Sweat Gland
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Sweat Glands
• Sweat or sudoriferous glands are epithelial glands widespread in the skin.
• Eccrine sweat glands respond to increased body temperature and function in evaporative cooling.
• Apocrine sweat glands become active at puberty and secrete sweat that produces body odor when metabolized by bacteria.
They can respond to pain, fear, and emotions.
• Modified sweat glands:
Ceruminous glands secrete ear wax.
Mammary glands secrete breast milk.
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Sebaceous Glands
• Sebaceous glands are holocrine glands associated with hair follicles.
• Sebum , a mixture of fatty material and cellular debris, is secreted to keep hair and skin soft and waterproof.
• Acne results from excess sebum secretion.
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Figure 6.11
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Problems in Temperature Regulation
• Hypothermia or lowered body temperature is a dangerous condition resulting from cold exposure.
• Hyperthermia or increased body temperature can result from inadequate body cooling during exercise or in extreme heat.
* Clinical Application 6.4
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Skin Color
• Heredity and environment determine skin color.
• The number of melanocytes is the same in all races, but more melanin is released in darker skinned individuals.
• People who inherit mutant melanin genes do not produce this pigment and have nonpigmented skin and hair, albinism.
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Other Factors Influencing Skin Color
• Ultraviolet light and X-rays stimulate melanocytes to synthesize melanin.
• Oxygenated blood creates a pink tint to skin while lack of oxygen results in cyanosis where the skin appears bluish.
• Carotene, found in yellow vegetables, can create a yellow or sallow tint to skin.
• Jaundice due to liver malfunction can create a bright yellow color in the skin.
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Skin Healing
• Superficial cuts heal due to increased epithelial cell division.
• Dermal cuts involve clotting and scab formation. Growth factors stimulate cell division and growth and scars may form.
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Skin Healing - Burns
• Superficial partial-thickness (first degree) burns involve redness of the epidermis.
• Deep partial-thickness (second degree) burns destroy the epidermis and some of the dermis. Fluid escapes causing blisters.
• Full-thickness (third degree) burns destroy the epidermis, dermis, and accessory skin organs.
• Treatment of burns involves estimating the burn surface area by the “rule of nines” (Fig. 6.14)