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Questions and Answers
What is the primary function of keratinocytes in the epidermis?
What is the primary function of keratinocytes in the epidermis?
What substance do sebaceous glands secrete?
What substance do sebaceous glands secrete?
Which structure is responsible for the sensation of touch?
Which structure is responsible for the sensation of touch?
Which layer of skin is absent in thin skin compared to thick skin?
Which layer of skin is absent in thin skin compared to thick skin?
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What is the main function of melanocytes in the skin?
What is the main function of melanocytes in the skin?
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What is the primary component of the dermis that provides durability and limits stretch?
What is the primary component of the dermis that provides durability and limits stretch?
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Where are Merkel's cells located in the skin, and what is their function?
Where are Merkel's cells located in the skin, and what is their function?
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Which of the following is NOT a function of the skin?
Which of the following is NOT a function of the skin?
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Which type of sweat gland secretes directly onto the skin's surface?
Which type of sweat gland secretes directly onto the skin's surface?
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Which type of cells synthesize melanin and transport it to keratinocytes?
Which type of cells synthesize melanin and transport it to keratinocytes?
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What is the primary responsibility of the skin in relation to UV protection?
What is the primary responsibility of the skin in relation to UV protection?
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What type of connective tissue is found in the papillary layer of the dermis?
What type of connective tissue is found in the papillary layer of the dermis?
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What characterizes the Langerhan’s cells in the epidermis?
What characterizes the Langerhan’s cells in the epidermis?
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Which type of skin ending is responsible for the sensation of pressure?
Which type of skin ending is responsible for the sensation of pressure?
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Which layer of skin is primarily responsible for the protection against water loss?
Which layer of skin is primarily responsible for the protection against water loss?
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What is the primary reason for preparing the skin before surgery?
What is the primary reason for preparing the skin before surgery?
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What is the primary function of sebaceous glands?
What is the primary function of sebaceous glands?
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Where are sweat glands most abundant in the human body?
Where are sweat glands most abundant in the human body?
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What causes hair to stand up and create goosebumps?
What causes hair to stand up and create goosebumps?
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What unique feature do the ridges formed by the dermal papillae create?
What unique feature do the ridges formed by the dermal papillae create?
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What type of tissue primarily comprises the hypodermis?
What type of tissue primarily comprises the hypodermis?
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Which of the following correctly describes the structure of hair?
Which of the following correctly describes the structure of hair?
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Sweat glands are differentiated into which two types?
Sweat glands are differentiated into which two types?
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What is the primary role of hair follicles?
What is the primary role of hair follicles?
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What is the defining characteristic of a third degree burn?
What is the defining characteristic of a third degree burn?
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Which of the following correctly describes the rule of nines used for assessing burnt areas?
Which of the following correctly describes the rule of nines used for assessing burnt areas?
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What type of ulcer develops over pressure points due to long-term compression?
What type of ulcer develops over pressure points due to long-term compression?
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Which of the following statements about second degree burns is true?
Which of the following statements about second degree burns is true?
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What is a key function of the skin?
What is a key function of the skin?
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What type of cells predominantly compose the stratum basalis of the epidermis?
What type of cells predominantly compose the stratum basalis of the epidermis?
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Which layer of skin is not typically present in thin skin?
Which layer of skin is not typically present in thin skin?
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What is the primary function of membrane-coating granules in the stratum granulosum?
What is the primary function of membrane-coating granules in the stratum granulosum?
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Which specialized cell type is responsible for the production of melanin in the epidermis?
Which specialized cell type is responsible for the production of melanin in the epidermis?
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What type of connective tissue is found in the papillary layer of the dermis?
What type of connective tissue is found in the papillary layer of the dermis?
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In which layer of the epidermis do desmosomes create a spiny appearance?
In which layer of the epidermis do desmosomes create a spiny appearance?
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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 provides the primary structural support?
Which layer of skin provides the primary structural support?
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Study Notes
Skin Types
- Two types of skin: thick and thin
- Thick: covers palms of hands and soles of feet.
- Thin: covers the rest of the body, mostly hairy.
Skin Layers
-
Epidermis:
- Stratified squamous keratinizing epithelium.
- Five layers (from deepest to outermost):
- Stratum basalis
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
-
Dermis:
- Papillary layer: loose connective tissue, supports and nourishes the epidermis, contains sensory nerves, lymphatics, and capillaries.
- Reticular layer: dense irregular connective tissue, tough, fibrous layer, collagen fibers limit stretch, elastic fibers provide flexibility.
-
Hypodermis (Subcutaneous Tissue):
- Loose connective tissue, contains adipose tissue.
Epidermis Layers
-
Stratum basalis:
- Single layer of columnar epithelial cells resting on a basement membrane.
- Contains many mitotic figures and cells with melanin, which can be either melanocytes or keratinocytes.
-
Stratum spinosum:
- Polygonal cells with central nuclei attached by desmosomes, giving a spiny appearance.
- Contains membrane-coating granules (Odland bodies).
-
Stratum granulosum:
- Flattened elongated cells containing keratohyalin granules (non-membrane bound).
- Membrane-coating granules are discharged into the intercellular spaces, forming a skin barrier.
-
Stratum lucidum:
- Prominent in thick skin, not in thin skin.
- Clear, thin layer of flattened, non-nucleated cells.
-
Stratum corneum:
- Outermost layer of the epidermis.
- 15-20 layers of dead, flattened, anucleate, keratin-filled keratinocytes.
- Provides protection against friction and water loss.
Thin Skin
- Covers the body except for palms and soles.
- Has hair, hair follicles, and sebaceous glands.
- Stratum lucidum is absent.
- Stratum spinosum, granulosum, and corneum are thinner than in thick skin.
Epidermal Cell Types
-
Keratinocytes:
- Predominant cell type in the epidermis, originating in the basal layer.
- Produce keratin and are responsible for the epidermal water barrier by making and secreting lipids.
-
Melanocyte:
- Located in the basal layer.
- Synthesize melanin in melanosomes and transport it to keratinocytes for UV protection.
-
Langerhan's Cells:
- Found in the stratum spinosum.
- Branched, star-shaped cells.
- Contain Birbeck granules in their cytoplasm.
- Function as antigen-presenting cells, contributing to skin immunity.
-
Merkel's Cells:
- Located in the basal layer.
- Contain neurosecretory granules near the cell membrane.
- Function as mechanoreceptors for tactile sensation.
Dermis Components
- Blood Vessels
- Sensory nerve endings
- Sweat glands and their ducts
- Hair follicles
- Sebaceous glands
- Arrector pili muscles
Dermis Structures
-
Sebaceous Glands:
- Secretory epithelial cells produce sebum (an oily secretion).
- Ducts open into hair follicles, softening hair.
- Most numerous in hairy areas.
-
Sweat Glands:
- Widely distributed in the skin.
- Each gland has a coiled body under the skin and a duct opening onto the skin surface (pore).
- Most numerous in palms, soles, axilla, and groin.
-
Arrector Pili Muscles:
- Small smooth muscle bundles attached to hair follicles.
- Contraction causes hair to stand and "goose flesh" appearance.
Fingerprints
- Ridges on the epidermis surface formed by projections from dermal papillae.
- Unique pattern in each person.
- Impression made by these ridges are fingerprints.
Hypodermis
- Contains adipose tissue and attaches the dermis to underlying tissues.
Epidermal Appendages
- Structures originating from the epidermis:
- Hair follicles
- Sweat glands (eccrine and apocrine)
- Sebaceous glands
- Nails
Hair Follicles
- Down growth of epidermal cells into the dermis.
- Base of follicle contains a cluster of cells called the bulb.
- Multiplication of cells in the bulb causes hair growth.
- Root: portion of hair embedded in the follicle.
- Shaft: portion of hair above the skin.
Sweat Glands
-
Eccrine Glands:
- Secrete sweat directly onto the skin surface.
-
Apocrine Glands:
- Secrete fluid into the hair follicle sac, eventually exiting onto the skin.
Sebaceous Glands
- Simple, branched acinar glands.
- Located between the hair follicle and arrector pili muscle.
- Secrete oily substance called sebum through holocrine secretion (entire cell breaks up).
- Absent in palms and soles.
Nails
- Protect the tips of fingers and toes.
- Nail root: embedded in the skin.
- Nail plate: exposed portion.
- Nail grows from a germinal part called the nail bed.
Cutaneous Nerve Endings
-
Free Nerve Endings:
- Detect pain and temperature.
-
Merkel's Cells:
- Tactile sensation in the stratum basale.
-
Meissner's Corpuscles:
- Touch.
-
Pacinian Corpuscles:
- Vibration and pressure.
-
Ruffini Endings:
- Pressure.
Skin Color Sources
-
Melanocytes:
- Produce melanin from tyrosine.
- Melanin provides UV protection.
- Responsible for reddish-brown to brown-black color.
-
Carotene:
- Contributes orange-yellow color.
- Obtained from diet (carrots, tomatoes).
-
Hemoglobin:
- Blood pigment.
Skin Functions
-
Excretion:
- Excretes water and salts in sweat.
-
Protection:
- Protects from bacteria, water, and excess heat and cold.
-
Temperature Regulation:
- Plays a major role in regulating body temperature.
-
Sensory Function:
- Organ for senses of touch, pain, temperature, and pressure.
- Vitamin D Production
Skin Clinical Notes
-
Preparation for Surgery:
- Skin harbors bacteria, so preparation is crucial to avoid infection.
- Steps include:
- Shaving hair in surgical area.
- Washing sebum with soap.
- Cleaning with an antiseptic.
-
Burns:
- Damage caused by fire, electricity, acids, etc.
- Damages skin structure, leading to infection and water loss.
- Classified by severity (depth): First, second, and third degree burns.
- First degree: epidermis damaged only, heals without scarring.
- Second degree: epidermis and upper dermis damaged, can heal without scarring if infection is prevented.
- Third degree: entire skin thickness destroyed, no pain as nerve endings are destroyed, regeneration is not possible, skin grafting is necessary.
- Rule of Nines: Method to determine the area of a burn by dividing the body into 11 areas, each representing 9% of the total body surface, plus 1% for the perineal area.
-
Ulcers:
- Occur on the skin in various regions.
- Pressure ulcers occur over pressure points, where skin is compressed between a bony prominence and a hard surface for an extended period.
- Common in bedridden patients or those confined to wheelchairs.
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Description
Test your knowledge on the different types of skin and their layers. This quiz covers the structural components and functions of the epidermis, dermis, and hypodermis. Understand the characteristics of thick and thin skin and the specific layers of the epidermis.
