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What is the primary function of the stratum corneum in the epidermis?
What is the primary function of the stratum corneum in the epidermis?
Which layer of the epidermis is responsible for the process of keratinization?
Which layer of the epidermis is responsible for the process of keratinization?
What is the main characteristic of keratinocytes in the epidermis?
What is the main characteristic of keratinocytes in the epidermis?
Which statement about the layers of the epidermis is true?
Which statement about the layers of the epidermis is true?
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Which function of the epidermis is not performed by the stratum basale?
Which function of the epidermis is not performed by the stratum basale?
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What primarily determines the amount of melanin produced in individuals?
What primarily determines the amount of melanin produced in individuals?
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Which skin cancer is associated with melanocytes?
Which skin cancer is associated with melanocytes?
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What is the primary method of heat loss from the body?
What is the primary method of heat loss from the body?
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What effect does UV radiation have on melanocytes?
What effect does UV radiation have on melanocytes?
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What layer of the dermis is primarily made of areolar connective tissue?
What layer of the dermis is primarily made of areolar connective tissue?
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Which of the following happens when the body temperature rises?
Which of the following happens when the body temperature rises?
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Which factor is NOT considered a physiological factor affecting skin color?
Which factor is NOT considered a physiological factor affecting skin color?
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What is the hypothalamus responsible for in terms of body temperature regulation?
What is the hypothalamus responsible for in terms of body temperature regulation?
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What is a primary role of dermal blood vessels?
What is a primary role of dermal blood vessels?
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What can be a symptom of hyperthermia?
What can be a symptom of hyperthermia?
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What pigment can accumulate in the skin as a result of diet?
What pigment can accumulate in the skin as a result of diet?
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Which of the following contributes to heat production in the body?
Which of the following contributes to heat production in the body?
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What type of sensory receptors in the dermis detect pressure?
What type of sensory receptors in the dermis detect pressure?
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What response occurs when the body experiences hypothermia?
What response occurs when the body experiences hypothermia?
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What results from prolonged exposure to cold without intervention?
What results from prolonged exposure to cold without intervention?
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What role does the skin play in temperature regulation?
What role does the skin play in temperature regulation?
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What is the function of sebaceous glands?
What is the function of sebaceous glands?
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Which part of a nail is considered the most active growing region?
Which part of a nail is considered the most active growing region?
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What is a common cause of pattern baldness in adults?
What is a common cause of pattern baldness in adults?
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Which structures can regenerate if accessory structures of the skin remain intact?
Which structures can regenerate if accessory structures of the skin remain intact?
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Where are hair follicles NOT present?
Where are hair follicles NOT present?
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What does the hair papilla contain that is essential for hair nourishment?
What does the hair papilla contain that is essential for hair nourishment?
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Which of the following is a characteristic of alopecia areata?
Which of the following is a characteristic of alopecia areata?
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Which part of a hair is dead and consists of epidermal cells?
Which part of a hair is dead and consists of epidermal cells?
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What mechanism is overwhelmed during hyperthermia?
What mechanism is overwhelmed during hyperthermia?
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How does fever contribute to fighting infections?
How does fever contribute to fighting infections?
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What are common characteristics of inflamed skin?
What are common characteristics of inflamed skin?
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What is the first step in the healing process of a deep cut?
What is the first step in the healing process of a deep cut?
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Which cells are primarily responsible for signaling the immune response during an infection?
Which cells are primarily responsible for signaling the immune response during an infection?
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What is the outermost layer of the epidermis called?
What is the outermost layer of the epidermis called?
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Where is the stratum lucidum primarily located?
Where is the stratum lucidum primarily located?
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What is a consequence of extreme vasodilation in a hot environment?
What is a consequence of extreme vasodilation in a hot environment?
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What forms the basis of a scar after wound healing?
What forms the basis of a scar after wound healing?
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Which layer of the epidermis is responsible for cell division and growth?
Which layer of the epidermis is responsible for cell division and growth?
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What is the primary role of inflammation in response to injury?
What is the primary role of inflammation in response to injury?
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What characteristic is associated with the stratum granulosum?
What characteristic is associated with the stratum granulosum?
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What is the primary function of melanocytes in the stratum basale?
What is the primary function of melanocytes in the stratum basale?
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Which layer of the epidermis contains cells with large, oval nuclei?
Which layer of the epidermis contains cells with large, oval nuclei?
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What is the role of melanin produced by melanocytes?
What is the role of melanin produced by melanocytes?
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Which characteristic does the stratum lucidum exhibit?
Which characteristic does the stratum lucidum exhibit?
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Study Notes
Chapter 06 Lecture Outline
- PowerPoint slides contain figures and tables, omitting notes.
Skin and Its Tissues
- Two or more tissue types grouped together, performing specialized functions, make up an organ.
- Skin is the largest organ in the body by weight.
- Another name for skin is the cutaneous membrane.
- Skin, along with its accessory structures (hair, nails, glands, and sensory receptors), constitutes the integumentary system.
- Skin is composed of several tissue types.
- Skin has two layers: epithelial tissue atop connective tissue.
- The outer layer is the epidermis.
- The deeper layer is the dermis.
Epidermis Tissues
- The outer layer is composed of stratified squamous epithelium.
- A basement membrane separates the epidermis from the dermis.
- The dermis is the thicker of the two skin layers, composed of connective tissue.
- The dermis contains collagenous and elastic fibers. (subcutaneous layer/hypodermis)
- The subcutaneous layer/hypodermis is beneath the dermis; acting as an insulating layer. This layer contains areolar and adipose connective tissue.
- The subcutaneous layer is not considered part of the skin.
Figure 6.1 Skin and Its Tissues
- Pictures are included of stratified squamous epithelium, dense irregular connective tissue, and adipose tissue.
Figure 6.2 Basic Structure of the Skin
- Diagram showing the epidermis, dermis, and subcutaneous layer.
- Components such as sweat glands, hair follicles, sebaceous glands, and nerve cells are identified within the dermis layer.
Epidermis
- Stratified squamous epithelium that rests on the basement membrane
- Lacks blood vessels
- Deepest layer, stratum basale, is nourished by blood vessels in the dermis
- Cells migrate toward the free skin surface, away from the nutrient supply.
- Keratinization: cells harden, dehydrate, and accumulate keratin as they move outward.
- Keratin is a tough, fibrous, waterproofing protein produced and stored in cells.
- Cells form a tightly packed stratum corneum outer layer, with desmosomes binding the cells together
- Stratum corneum cells slough off the skin surface.
- Thickest on palms and soles (0.8-1.4 mm), thinner elsewhere (0.07-0.12 mm).
Figure 6.3 Epidermis
-
Diagram of the five layers of the epidermis:
- Stratum corneum (outermost layer); dead keratinized cells.
- Stratum lucidum (only in thick skin); palms and soles.
- Stratum granulosum
- Stratum spinosum
- Stratum basale (deepest layer); mitotic layer.
-
Function is to protect against water loss, harmful chemicals, mechanical injury, and pathogens.
Table 6.1 Layers of the Epidermis
- Details about each layer of the epidermis, including locations and characteristics.
Figure 6.4 Epidermis
- Melanocytes in the stratum basale produce melanin, the dark pigment that absorbs UV light and provides skin color.
- Melanin protects skin cells from UV light damage (DNA damage, fibroblast damage, and skin cancer).
Epidermis: Skin Color
- Factors affecting skin color:
- Hereditary factors include the number of melanocytes and the amount and distribution of melanin granules. Albinos lack melanin.
- Environmental factors include sunlight, UV light, and X-rays.
- Physiological factors include oxygenation in the blood of dermal blood vessels (pinkish, cyanosis), vasodilation/vasoconstriction, and accumulation of carotene.
Clinical Application 6.1 Indoor Tanning and Skin Cancer
- Exposure to sunlight or tanning beds increases melanin production, darkening the skin.
- Tanning beds deliver high doses of UV radiation overwhelming the body's natural defense against skin cancer.
- Skin cancers (basal cell carcinoma and squamous cell carcinoma) arise from epithelial cells.
- Melanomas, arising from melanocytes, are the least common skin cancer but cause 80% of skin cancer deaths.
Dermis
- Inner layer of skin, average thickness is 1-2 mm.
- Contains dermal papillae between epidermal ridges that bind epidermis to underlying tissues.
- Contains connective tissue and muscle fibers.
- Contains nerve cell processes.
- Dermal blood vessels supply nutrients to skin cells.
- Contains hair follicles, sweat glands, and sebaceous glands.
- Contains sensory receptors (lamellar and tactile corpuscles).
Dermis Layers
- Papillary layer: Superficial layer composed of areolar connective tissue; thinnest layer; location of dermal papillae.
- Reticular layer: Deeper layer made of dense irregular connective tissue; thicker layer than the papillary layer.
Accessory Structures of the Skin
- Accessory structures extend into the dermis or hypodermis from the epidermis.
- Include hair follicles, nails, and skin glands (sweat and sebaceous).
- If accessory structures remain intact, the injured/burned dermis can regenerate.
Nails
- Protective coverings on ends of fingers and toes.
- Three parts: nail plate, nail bed, and lunula (most active growing region).
Figure 6.7 Hair Follicles
- Hair is found on all skin surfaces except palms, soles, lips, parts of external reproductive organs.
- A hair follicle is a tube-like depression from which hair develops, extending into the dermis or subcutaneous layer.
- Three parts of hair: hair bulb (dividing cells), hair root, and hair shaft (dead, keratinized cells).
- Hair follicles contain blood vessels to nourish hair.
- Hair color is related to the type and amount of melanin in the shaft produced by melanocytes.
- Arrector pili muscle (goosebumps) cause hair to stand erect.
Clinical Application 6.2 Hair Loss
- Common type of baldness is pattern baldness (androgenic alopecia), caused by lowered testosterone levels in men and estrogen levels in women.
- Progenitor cells are lacking in bald spots, but stem cells are present.
- Alopecia areata: autoimmune hair loss caused by antibodies attacking hair follicles.
Figure 6.9 Skin Glands: Sebaceous Glands
- Holocrine glands usually associated with hair follicles.
- Produce sebum (fatty material and cellular debris) which keeps hair and skin soft and waterproof.
- Excess sebum can result in acne and is absent on palms and soles.
Clinical Application 6.3 Acne
- Acne is a sebaceous gland disorder, common at puberty due to gland response to androgens.
- Acne occurs when sebaceous glands become clogged with sebum and epithelial cells. This provides an environment for anaerobic bacteria causing inflammation.
- Occurs in 80% of people between 11 and 30.
- Treatment involves Vitamin A derivatives, systemic antibiotics, salicylic acid, and benzoyl peroxide.
Figure 6.10 Skin Glands: Sweat Glands
- Also called sudoriferous glands, widespread in skin originating in deeper dermis or hypodermis.
- Eccrine (merocrine) glands are the most numerous and respond to body temperature.
- Apocrine sweat glands are located in axillary and groin areas; respond to emotions and pain.
- Other glands include ceruminous (ear wax) and mammary (milk).
Table 6.2 Skin Glands
- Description and function of each type of skin gland.
Skin Functions
- Protective covering (barrier against harmful substances, microorganisms).
- Prevents water loss.
- Contains sensory receptors.
- Excretes wastes.
- Helps produce vitamin D.
- Helps regulate body temperature.
Regulation of Body Temperature
- Important for maintaining metabolic rates, monitored by the hypothalamus.
- Set point is ~37 °C (98.6 °F).
- Skin plays a role in homeostatic mechanisms for temperature regulation.
Heat Production and Loss
- Heat is a product of cellular metabolism (skeletal and cardiac muscles, liver cells produce most heat).
- Methods of heat loss include radiation, conduction, convection, and evaporation (sweat changes to gas).
- Vasodilation of dermal blood vessels increases heat loss when the body is too hot.
- Vasoconstriction of deep blood vessels when the body is cold to conserve heat.
Figure 6.12 Body Temperature Regulation
- Diagram illustrating mechanisms for maintaining body temperature when it rises and when it falls.
- Signals to regulate the body temperature are sent through thermoreceptors to the hypothalamus (control center).
Problems in Temperature Regulation
- Hyperthermia: occurs when sweat cannot evaporate and heat from the air increases body temperature. Signs of hyperthermia include dry skin, weakness, dizziness, nausea, and rapid pulse.
- Hypothermia: unusually low body temperature resulting from extended cold exposure or illness. Signs of hypothermia include shivering, confusion, lethargy, loss of reflexes and consciousness.
Clinical Application 6.4 Elevated Body Temperature
- When the body loses the ability to regulate temperature in extremely hot environments, it can lead to hyperthermia.
- Raising the set-point (temperature range) of the body can be part of the immune system's defense mechanism to fight infections.
- Phagocytes release pyrogens in response to pathogens, increasing the set point and thus body temperature to destroy the pathogens.
Healing of Wounds and Burns
- Inflammation is a normal response to injury or stress. Blood vessels in affected tissues dilate, becoming more permeable.
- The damaged skin may become swollen, red, warm, or painful.
Cuts
- Shallow cuts (affecting only the epidermis) cause epidermal cells to divide more rapidly to fill gaps.
- Deep cuts (affecting dermis and subcutaneous layer) result in blood vessel breakage.
- Blood creates a clot.
- Clot and dried tissue form a scab.
- Epithelial cells reproduce and fill the wound.
- Fibroblasts produce collagen fibers to bind the wound.
- Phagocytic cells remove dead cells and debris.
- Excess collagen can form a scar.
Figure 6.13 Healing of a Wound
- Diagram of the healing process in wounds showing stages of healing.
Burns
- Burns are classified by tissue damage extent.
- Superficial (first-degree) burns affect only the epidermis, causing redness, heat, and inflammation (sunburns).
- Deep partial-thickness (second-degree) burns destroy the epidermis and some dermis and may blister.
- Deep full-thickness (third-degree) burns destroy epidermis, dermis, and accessory structures. Healing occurs from the margin and often requires skin grafts.
Figure 6.15 Rule of Nines for Burn Patients
- A method for estimating the extent of burn injury by dividing the body surface into regions of 9% or multiples of 9.
- Estimations are used for fluid and electrolyte replacement and skin grafting.
Life-Span Changes
- Cell cycle slows; skin becomes scaly, age spots appear.
- Epidermis and dermis thin.
- Fat loss reduces; person feels cold.
- Skin wrinkles and sags.
- Sebaceous glands produce less oil. Skin becomes dry.
- Melanin production slows, hair whitens.
- Hair thins.
- Hair follicle numbers decline.
- Nail growth declines.
- Sensory receptors decline.
- Body temperature regulation less effective.
- Ability to produce vitamin D declines.
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Test your knowledge on the structure and function of skin and its tissues in this Chapter 06 quiz. Explore concepts such as the layers of skin, types of tissue, and the integumentary system. Perfect for students studying human anatomy!
