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Questions and Answers
What type of secretion involves the entire cell breaking up to form the secretion?
What type of secretion involves the entire cell breaking up to form the secretion?
Which substance does the sebaceous glands secrete?
Which substance does the sebaceous glands secrete?
Which of the following nail structures is responsible for the nail growth?
Which of the following nail structures is responsible for the nail growth?
Which skin structure is primarily responsible for detecting vibration and pressure?
Which skin structure is primarily responsible for detecting vibration and pressure?
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What is the role of melanocytes in the skin?
What is the role of melanocytes in the skin?
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Which function of the skin involves the regulation of body temperature?
Which function of the skin involves the regulation of body temperature?
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What characterizes a third-degree burn?
What characterizes a third-degree burn?
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Which method is used to determine the area of burns on the body?
Which method is used to determine the area of burns on the body?
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What are free nerve endings primarily responsible for in the skin?
What are free nerve endings primarily responsible for in the skin?
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Which pigment is primarily responsible for the reddish-brown to brown-black color of the skin?
Which pigment is primarily responsible for the reddish-brown to brown-black color of the skin?
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Which layer of the dermis is responsible for providing support and nourishment to the epidermis?
Which layer of the dermis is responsible for providing support and nourishment to the epidermis?
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What is the primary function of keratinocytes in the epidermis?
What is the primary function of keratinocytes in the epidermis?
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Which type of cells in the epidermis synthesize melanin?
Which type of cells in the epidermis synthesize melanin?
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What contributes to the skin's immune response?
What contributes to the skin's immune response?
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Which epidermal cell type is located in the stratum spinosum and has a characteristic feature called Birbeck granules?
Which epidermal cell type is located in the stratum spinosum and has a characteristic feature called Birbeck granules?
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What type of connective tissue is found in the reticular layer of the dermis?
What type of connective tissue is found in the reticular layer of the dermis?
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What is the function of sebaceous glands in the skin?
What is the function of sebaceous glands in the skin?
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Which layer of the skin is described as tough and fibrous, containing collagen and elastic fibers for limit stretch and flexibility?
Which layer of the skin is described as tough and fibrous, containing collagen and elastic fibers for limit stretch and flexibility?
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Where are Merkel cells located and what is their primary function?
Where are Merkel cells located and what is their primary function?
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What is absent in thin skin compared to thick skin?
What is absent in thin skin compared to thick skin?
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What function do sebaceous glands serve?
What function do sebaceous glands serve?
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Where are sweat glands most numerous?
Where are sweat glands most numerous?
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What is the primary role of the arrector pili muscles?
What is the primary role of the arrector pili muscles?
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What structure arises directly from the epidermis?
What structure arises directly from the epidermis?
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Which type of sweat gland secretes directly onto the surface of the skin?
Which type of sweat gland secretes directly onto the surface of the skin?
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What are the ridged patterns on the epidermis that form fingerprints called?
What are the ridged patterns on the epidermis that form fingerprints called?
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What is the role of the hypodermis?
What is the role of the hypodermis?
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What part of the hair follicle is responsible for hair growth?
What part of the hair follicle is responsible for hair growth?
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Which sweat gland type opens into the sac of a hair follicle?
Which sweat gland type opens into the sac of a hair follicle?
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What type of gland is classified as a simple branched acinar gland?
What type of gland is classified as a simple branched acinar gland?
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Which layer of skin is primarily responsible for the barrier function?
Which layer of skin is primarily responsible for the barrier function?
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What type of tissue primarily makes up the papillary layer of the dermis?
What type of tissue primarily makes up the papillary layer of the dermis?
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In which layer of the epidermis do you find keratohyalin granules?
In which layer of the epidermis do you find keratohyalin granules?
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Which skin type contains hair follicles and sebaceous glands?
Which skin type contains hair follicles and sebaceous glands?
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What is the primary function of the stratum lucidum?
What is the primary function of the stratum lucidum?
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Which of the following cell types is primarily responsible for producing melanin?
Which of the following cell types is primarily responsible for producing melanin?
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What describes the appearance of cells in the stratum spinosum?
What describes the appearance of cells in the stratum spinosum?
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What structural feature is most associated with the stratum basalis?
What structural feature is most associated with the stratum basalis?
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What is the primary characteristic of the stratum corneum?
What is the primary characteristic of the stratum corneum?
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Which layer of skin is thicker in the palms of the hands and soles of the feet?
Which layer of skin is thicker in the palms of the hands and soles of the feet?
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Study Notes
The Skin
- The skin is the largest organ in the human body
- The skin is responsible for protecting the body from the environment
- Skin is composed of three distinct layers: the epidermis, the dermis, and the hypodermis
Epidermis
- The epidermis is the outermost layer of skin
- The epidermis is made of stratified squamous keratinizing epithelium
- It is comprised of five layers:
- Stratum basale: consists of a single layer of columnar epithelial cells; contains mitotically active cells; some cells contain melanin pigment
- Stratum spinosum: formed of polygonal shaped cells; cells connected by desmosomes; contains membrane-coating granules
- Stratum granulosum: consists of flattened elongated cells; contains keratohyalin granules
- Stratum lucidum: present in thick skin but not in thin skin; consists of flattened non-nucleated cells
- Stratum corneum: outermost layer of the epidermis; consists of 15-20 layers of dead, flattened, anucleate keratinocytes; protects against friction and water loss,
Cell Types in Epidermis
- Keratinocytes: the predominant cell type; originate in the basal layer; produce keratin; responsible for the epidermal water barrier
- Melanocytes: synthesize dark melanin pigment in melanosomes; transport melanosomes to adjacent keratinocytes
- Langerhans cells: located in stratum spinosum; branched star shaped cells; function as antigen presenting cells
- Merkel cells: located in the basal layer of the epidermis; contain small dense neurosecretory granules; function as mechanoreceptors for tactile sensation
Dermis
- The dermis is the layer of skin below the epidermis
- The dermis is composed of two layers:
- Papillary layer: supports and nourishes epidermis; contains sensory nerves, lymphatics, and capillaries
- Reticular layer: dense irregular connective tissue; collagen fibers limit stretch; elastic fibers provide flexibility
Structures in the Dermis
- Blood vessels
- Sensory (touch) nerve endings
- Sweat glands and their ducts
- Hair follicles
- Sebaceous glands
- Arrector pili muscles
Sebaceous Glands
- Made of secretory epithelial cells that secrete sebum (oily secretion)
- Secrete sebum via holocrine secretion (entire cell breaks up to form secretion)
- Sebaceous glands are absent in the palms and soles
Sweat Glands
- Widely distributed in the skin
- Each gland has a coiled body under the skin and a duct that opens onto the pores on the skin
- Most numerous on palms of hands, soles of feet, axilla, and groin
- Sweat glands are divided into two types:
- Eccrine sweat glands: secrete sweat directly onto the surface of the skin
- Apocrine sweat glands: secrete fluid into the sac of a hair follicle where it eventually comes out on the skin
Hair Follicles
- Down growths of epidermal cells into the dermis
- At the base of the follicle, a cluster of cells called the bulb is present
- Multiplication of cells in the bulb causes the hair to grow
- The part of the hair inside the skin is called the root
- The part of the hair above the skin is called the shaft
Arrector Pili Muscles
- Small bundles of smooth muscles that are attached to hair follicles
- Contraction causes the hair to stand erect and causes goose flesh
Nails
- Protect the tips of the fingers and toes
- Nails have a root embedded in the skin
- The exposed part is called the nail plate
- The nail grows from the epidermis from a germinal part called the nail bed
Cutaneous Nerve Endings
- Free nerve endings: perceive pain and temperature
- Merkel cells: tactile sensation
- Meissner's corpuscles: touch
- Pacinian corpuscles: vibration and pressure
- Ruffini endings: pressure
Sources of Skin Color
- Melanocytes: produce melanin, which provides UV protection; gives reddish-brown to brown-black color
- Carotene: contributes orange-yellow color; provided from diet (carrots and tomatoes)
- Hemoglobin: blood pigment
Functions of Skin
- Excretion: skin excretes some water and salts in sweat
- Protection: skin protects from bacteria, water loss, and excess heat and cold
- Temperature regulation: skin plays a major role in regulating body temperature
- Sensory function: skin is an organ of sense of touch, pain, temperature, and pressure
- Production of vitamin D
Clinical Notes About Skin
- Skin preparation for surgery: the skin harbors many bacteria; preparation involves shaving hair in the area, washing the sebum with soap, and cleaning the skin with antiseptic
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Burns: burns cause damage to the skin due to fire, electricity, or acids; structure of the skin is damaged, infection and water loss are common; burns are classified according to their severity (depth) as first, second, and third-degree burns
- First-degree burn: only epidermis is damaged; heals and leaves no scar
- Second-degree burn: damage to epidermis and upper region of the dermis; if carefully treated and infection prevented can heal without a scar
- Third-degree burn: destroys the entire thickness of the skin; there is no pain as nerve endings are destroyed; regeneration is not possible; skin grafting must be done
- Determination of the burnt area: use the rule of nines to determine the area burnt
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Description
Explore the fascinating structure of the skin, the largest organ in the human body. This quiz covers the layers of the skin with a focus on the epidermis, its components, and functions. Test your knowledge about the epidermal layers and their significance in protecting the body.
