Skin Anatomy Quiz
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Questions and Answers

What are the primary components of the skin, and what are their embryonic origins?

The primary components of the skin are the epidermis derived from ectoderm and the dermis and hypodermis derived from mesoderm.

What percentage of the epidermis is made up of keratinocytes, and where do they primarily proliferate?

95% of the epidermis consists of keratinocytes, which primarily proliferate in the basal layer of the epidermis.

Name the four types of epidermal cells and their respective systems.

The four types of epidermal cells are keratinocytes (keratinizing system), melanocytes (pigmentary system), Langerhans cells (Langerhans's system), and Merkel cells (Merkel system).

What characterizes the stratum basale and why is it crucial for the epidermis?

<p>The stratum basale consists of a single layer of cubical or columnar cells that serve as stem cells for new keratinocytes, making it crucial for epidermal regeneration.</p> Signup and view all the answers

Describe the structural features of the stratum spinosum.

<p>The stratum spinosum contains several layers of polyhedral cells with intercellular 'spines' due to desmosome connections, and features tonofilaments around the nucleus.</p> Signup and view all the answers

What is the role of desmosomes in the stratum spinosum, and what do they connect?

<p>Desmosomes in the stratum spinosum connect adjacent cells, providing structural stability and resistance to mechanical stress.</p> Signup and view all the answers

What is the significance of the basement membrane in skin anatomy?

<p>The basement membrane serves as an interface between the epidermis and dermis, providing structural support and facilitating nutrient exchange.</p> Signup and view all the answers

Explain the function of melanocytes within the epidermis.

<p>Melanocytes produce melanin, which gives color to the skin and protects against UV radiation damage.</p> Signup and view all the answers

What is the primary structural orientation of collagen fibers in the skin?

<p>Collagen fibers primarily lie horizontally to the surface and parallel to Langer's lines.</p> Signup and view all the answers

What types of cells are most abundant in the deep reticular layer of the skin?

<p>The most abundant cells in the deep reticular layer are fibroblasts.</p> Signup and view all the answers

How do eccrine sweat glands differ in distribution compared to other types of sweat glands?

<p>Eccrine glands are widely distributed throughout the body, excluding the lips and certain genital areas.</p> Signup and view all the answers

What physiological factors control the sweating process?

<p>Sweating is controlled by the thermoregulatory center in the hypothalamus and can be initiated locally or through axon-reflex.</p> Signup and view all the answers

What role does the hypodermis play in relation to the skin?

<p>The hypodermis provides support for the skin, serves as a fat storage depot, and connects to deeper tissues.</p> Signup and view all the answers

What is the function of the rete ridges in the skin?

<p>Rete ridges are epidermal in origin and help interlock the epidermis with the underlying dermis.</p> Signup and view all the answers

Describe the unique structural features of eccrine sweat glands.

<p>Eccrine sweat glands have a coiled secretory portion, a straight dermal duct, and a spiral epidermal duct.</p> Signup and view all the answers

What types of sensory components are contained within the dermal papillae?

<p>Dermal papillae contain sensory nerve endings, blood vessels, and lymphatics.</p> Signup and view all the answers

What is the primary role of melanin in the skin?

<p>The primary role of melanin is to protect the skin from UV rays and prevent malignant tumors.</p> Signup and view all the answers

How does skin color relate to the incidence of skin cancer?

<p>Darker skin has a lower incidence of skin cancer due to higher melanin levels that provide better UV protection.</p> Signup and view all the answers

What processes can lead to skin darkening after sun exposure?

<p>Skin can darken through immediate oxidation of melanin or an increase in melanin synthesis over several days.</p> Signup and view all the answers

What is the origin and function of Langerhans cells?

<p>Langerhans cells originate from the bone marrow and function as antigen presenting cells that process allergens.</p> Signup and view all the answers

Describe the role of Merkel cells in the skin.

<p>Merkel cells are involved in touch reception and transmit tactile information to sensory nerves.</p> Signup and view all the answers

Identify the key structures found at the dermo-epidermal junction.

<p>Key structures include tonofilaments, attachment plaques, lamina lucida, and basal lamina.</p> Signup and view all the answers

What is the relative thickness of the dermis compared to the epidermis?

<p>The dermis is approximately 15 to 40 times thicker than the epidermis.</p> Signup and view all the answers

List some components that the dermis supports.

<p>The dermis supports glands, hair follicles, blood vessels, lymphatics, and nerves.</p> Signup and view all the answers

What is the primary composition of hair and how does it relate to its strength?

<p>Hair is primarily composed of hard keratin, which contains high sulphur bonds making it strong and resistant to breakage.</p> Signup and view all the answers

Explain the three phases of the hair growth cycle and their significance.

<p>The three phases are the Anagen (growth), Catagen (regression), and Telogen (resting) phases; they regulate hair length and shedding.</p> Signup and view all the answers

Discuss the impact of aging on the number of hair follicles.

<p>With advancing age, there is a significant loss of hair follicles, contributing to thinning hair and baldness.</p> Signup and view all the answers

What distinguishes terminal hair from vellus hair in terms of structure and development?

<p>Terminal hair is longer, coarser, and often pigmented, while vellus hair is soft, unmedullated, and less pigmented, developing into terminal hair due to androgens.</p> Signup and view all the answers

How does the growth rate of nails compare to that of hair, and what are the implications for their respective growth cycles?

<p>Nails grow at a rate of 0.1 mm/day continuously, while hair grows cyclically at 0.3 mm/day during the Anagen phase, affecting their overall length and development.</p> Signup and view all the answers

Identify and explain two functions of skin beyond its protective role.

<p>The skin synthesizes vitamin D from 7-dehydrocholesterol when exposed to sunlight and regulates body temperature through sweat glands.</p> Signup and view all the answers

What characterizes lanugo hair and under what conditions might it be retained into adulthood?

<p>Lanugo hair is fine, soft, unmedullated, and usually unpigmented; it may be retained in adulthood in conditions like hypertrichosis lanuginosa.</p> Signup and view all the answers

Analyze how seasonal changes can influence hair growth rates.

<p>Hair growth rates are typically faster in summer and in children due to environmental factors and biological adaptability.</p> Signup and view all the answers

What distinguishes petechiae from ecchymosis in terms of size?

<p>Petechiae are less than 1 cm, while ecchymosis is larger than 1 cm.</p> Signup and view all the answers

Define ulcer in the context of skin lesions.

<p>An ulcer is a circumscribed loss of tissue involving the epidermis, dermis, or deeper tissue.</p> Signup and view all the answers

What characterizes telangiectasia?

<p>Telangiectasia is characterized by permanent dilatation of blood vessels in the dermis.</p> Signup and view all the answers

How does a keloid develop in relation to scars?

<p>A keloid develops from hypertrophic scars that last longer than three months.</p> Signup and view all the answers

What are the typical characteristics observed during the palpation of skin lesions?

<p>During palpation, the characteristics may include consistency, temperature, mobility, and tenderness.</p> Signup and view all the answers

What is lichenification and in what circumstances does it commonly occur?

<p>Lichenification is the hypertrophy and hyperpigmentation of the skin, usually occurring in chronic skin diseases.</p> Signup and view all the answers

Explain how diascopy helps differentiate between erythema and purpura.

<p>Diascopy involves applying pressure on the skin, which will abolish erythema but purpura will persist.</p> Signup and view all the answers

What does the presence of scales on the skin indicate?

<p>Scales indicate shaded desquamating epidermal cells on the skin surface.</p> Signup and view all the answers

What is the primary function of melanin in the skin?

<p>Protecting from UV rays</p> Signup and view all the answers

Darker skin tones have a higher incidence of skin cancer caused by UV light.

<p>False</p> Signup and view all the answers

Name the cells in the skin that act as antigen presenting cells.

<p>Langerhans cells</p> Signup and view all the answers

The dermis is approximately ____ to ____ times thicker than the epidermis.

<p>15 to 40</p> Signup and view all the answers

Match the following skin cells with their primary function:

<p>Melanocytes = Produce melanin Merkel cells = Touch reception Langerhans cells = Antigen presentation Fibroblasts = Produce collagen and elastin</p> Signup and view all the answers

What structure is primarily involved in touch sensation in the skin?

<p>Merkel cells</p> Signup and view all the answers

Exposure to sunlight can lead to immediate darkening of the skin due to oxidation of melanins.

<p>True</p> Signup and view all the answers

What is the primary structural orientation of collagen fibers in the skin?

<p>Network or interwoven</p> Signup and view all the answers

What type of cells primarily make up the stratum basale?

<p>Cubical or columnar cells</p> Signup and view all the answers

Langerhans cells are primarily involved in the pigmentary system of the skin.

<p>False</p> Signup and view all the answers

What is the primary function of the basement membrane in the skin?

<p>To anchor the epidermis to the underlying dermis and provide structural support.</p> Signup and view all the answers

The cells responsible for skin pigmentation are called __________.

<p>melanocytes</p> Signup and view all the answers

Match each epidermal cell type with its corresponding function:

<p>Keratinocytes = Form the outer layer of skin Melanocytes = Produce melanin Langerhans cells = Act as immune responders Merkel cells = Serve as mechanoreceptors</p> Signup and view all the answers

Which layer of the epidermis contains several layers of polyhedral cells with spines?

<p>Stratum spinosum</p> Signup and view all the answers

The epidermis is a vascular tissue that relies on blood vessels for its nutritional needs.

<p>False</p> Signup and view all the answers

What is the average thickness of the epidermis?

<p>About 0.2 mm.</p> Signup and view all the answers

What is the primary role of Langerhans cells in the skin?

<p>Antigen presentation</p> Signup and view all the answers

Skin lesions that only affect the epidermis typically heal without scarring.

<p>True</p> Signup and view all the answers

What are macules and how do they appear?

<p>Macules are circumscribed discolorations of the skin less than 0.5 cm in diameter.</p> Signup and view all the answers

A _____ is characterized by a transient circumscribed elevation of the skin, which is usually whitish or pinkish.

<p>wheal</p> Signup and view all the answers

Which of the following skin symptoms can indicate a possible skin disease?

<p>Pruritus</p> Signup and view all the answers

Match the type of skin lesion with its description:

<p>Papule = A circumscribed palpable elevation less than 0.5 cm Bullae = Visible accumulation of fluid greater than 1 cm Pustule = Visible accumulation of pus Nodule = A circumscribed mass larger than 1 cm involving deeper skin layers</p> Signup and view all the answers

Skin serves no role in personal recognition and sexual attraction.

<p>False</p> Signup and view all the answers

List two primary characteristics of a cyst.

<p>A cyst is a cavity lined by epithelium and should have its entire cavity removed to avoid recurrence.</p> Signup and view all the answers

What is the primary function of eccrine sweat glands?

<p>Temperature regulation</p> Signup and view all the answers

The hypodermis contains primarily muscular tissue.

<p>False</p> Signup and view all the answers

What are rete ridges?

<p>Epidermal projections into the dermis.</p> Signup and view all the answers

Sweating may be initiated locally after eating spicy foods, a phenomenon known as __________ sweating.

<p>gustatory</p> Signup and view all the answers

Match the type of sweat gland with its characteristic:

<p>Eccrine glands = Widely distributed except lips and nails Apocrine glands = Found mainly in axillary and genital areas Sebaceous glands = Secrete oil to lubricate skin Mammary glands = Specialized for milk secretion</p> Signup and view all the answers

Which layer of the skin contains the most sensory nerve endings, blood vessels, and lymphatics?

<p>Superficial papillary layer</p> Signup and view all the answers

Collagen fibers in the skin are arranged parallel to the lines of tension.

<p>True</p> Signup and view all the answers

What role do fibroblasts play in the skin?

<p>They are responsible for producing collagen and other extracellular matrix components.</p> Signup and view all the answers

What defines a tumor in the skin?

<p>A circumscribed mass of varying size in the epidermis or dermis</p> Signup and view all the answers

Purpura can refer to both petechiae and ecchymosis.

<p>True</p> Signup and view all the answers

What type of skin lesion results from scratching?

<p>Excoriation</p> Signup and view all the answers

A ____, which is a secondary skin lesion, is described as a circumscribed loss of tissue that may involve the epidermis and dermis.

<p>ulcer</p> Signup and view all the answers

Match the skin lesions with their descriptions:

<p>Scales = Shaded desquamating epidermal cells Crust = Dried scales, sebum, or purulent exudates Fissure = Linear cut forming deep discontinuation Scar = Fibrous tissue replacement of destroyed skin</p> Signup and view all the answers

Which of the following describes telangiectasia?

<p>Permanent dilatation of blood vessels in the dermis</p> Signup and view all the answers

Atrophy results in hypertrophy of the skin.

<p>False</p> Signup and view all the answers

What color can skin lesions present?

<p>White, red, pink, violaceous, brown, black, blue, grey, yellow, purpuric</p> Signup and view all the answers

Study Notes

Epidermis

  • Contains a variety of cell types: keratinocytes, melanocytes, Langerhans cells and Merkel cells.
  • Keratinocytes undergo constant mitosis in the basal layer and migrate upwards, differentiating into cornified cells.
  • Melanocytes produce melanin, which protects the skin from UV radiation, with darker skin pigmentation having a lower incidence of skin cancer.
  • Melanocytes also absorb harmful substances, metals and drugs.
  • Langerhans cells are dendritic cells scattered throughout the stratum Malpighi, acting as antigen presenting cells, trapping allergens and stimulating the production of specifically sensitized lymphocytes.
  • Merkel cells are neural crest derived cells involved in touch reception, found in large numbers in the fingers, oral mucosa and hair roots, secreting neurotransmitters after physical stimulation.

Dermis

  • Lies beneath the epidermis, about 15-40 times thicker.
  • Consists mainly of fibrous tissue (collagen and elastin) that supports glands, hair follicles, blood vessels, lymphatics, and nerves.
  • Contains two layers: superficial papillary layer and deep reticular layer.
  • Papillary layer contains small fibrous tissue bundles, sensory nerve endings, blood vessels and lymphatics, with inter-papillary spaces called rete ridges.
  • Reticular layer contains a network of collagenous bundles and elastic fibers, encasing sebaceous and sweat glands, hair follicles and erector pili muscles.

Hypodermis

  • Subcutaneous loose connective tissue, acting as a transition zone containing fat cells, white and yellow connective tissue, sweat gland coils and hair roots.
  • Provides support for the skin and attachment to deeper tissues.
  • Serves as a storage depot for fat and contains large blood vessels supplying the skin.

Sweat glands

  • Eccrine glands are widely distributed, except at the lips, beneath the nails and on the glans penis, clitoris and labia minora.
  • Consists of a coiled secretory portion in the dermis and hypodermis, a dermal duct and an epidermal duct, opening at the apex of epidermal ridges.
  • Innervated by sympathetic cholinergic fibers and controlled by the thermoregulatory center in the hypothalamus.
  • Play a vital role in temperature regulation.

Hair follicles

  • Total of 5 million hair follicles in the human body, with one million in the head and 100,000 in the scalp.
  • Significant loss of hair follicles with advancing age.
  • Hair contains hard keratin, with high sulfur bonds influencing its stretching properties.
  • Three types of hair: lanugo (prenatal coat), vellus (soft, unmedullated), and terminal (longer, coarser, often pigmented).
  • Hair growth cycle includes anagen (growth), catagen (regression), and telogen (resting) phases.
  • Anagen phase varies greatly, with the scalp having over 90% of hair in this phase, and a growth rate of 0.3 mm/day.
  • Catagen phase involves regression, while the telogen phase is the resting phase.

Nails

  • Composed of nail plate, nail matrix and nail bed.
  • Nail plate is made of modified horny cells.
  • Nail matrix consists of modified cells from the stratum Malpighi.
  • Nail bed underlies the nail plate, attaching it firmly.
  • Nails grow continuously at a rate of 0.1 mm/day.

Skin functions

  • Acts as a protective shield against chemical, physical and biological insults.
  • Screens against ultraviolet radiation.
  • Possesses regenerative capacity.
  • Synthesizes vitamin D from 7-dehydrocholestrol under light influence.
  • Regulates body temperature.
  • Represents the largest sensory organ.
  • Functions as a secretory organ through sweat glands.

Skin lesions

  • Tumor: circumscribed mass in the epidermis, dermis or both.
  • Purpura: free red blood cells (RBCs) in the dermis, less than 1 cm (petechae) or bigger than 1 cm (ecchymosis).
  • Telangiectasia: permanent dilatation of blood vessels in the dermis.
  • Scales: shed desquamating epidermal cells.
  • Crust: dried scales, sebum or purulent exudates on the skin surface, characteristic of pyogenic infections.
  • Ulcer: circumscribed loss of tissue involving the epidermis alone or epidermis, dermis, and underlying tissue.
  • Excoriation: discontinuation of the skin produced by scratching, either superficial linear or deep.
  • Fissure: linear cut forming a deep linear discontinuation with sharply defined walls or inflamed basis.
  • Pigmentation: skin discoloration due to melanin, phaeomelanin, haemoglobin, oxyhaemoglobin and carotenoids.
  • Scar: fibrous tissue replacement of skin substance destroyed by disease or trauma, differing in color and texture from normal skin, can be atrophic or hypertrophic.
  • Lichenification: hypertrophy of the skin, hyperpigmentation and exaggeration of normal skin lines, usually occurring in chronic skin diseases.
  • Sclerosis: diffuse or circumscribed induration of the subcutaneous tissue, potentially involving the dermis.
  • Atrophy: skin surface depression resulting from thinning of the epidermis or dermis.
  • Erythema: redness of the skin caused by increased blood flow in the superficial blood vessels.
  • Diascopy: applying pressure on the skin with a finger or glass slide abolishes erythema while purpura persists.

Color of lesions

  • Skin lesions can present with various colors including white, red, pink, violaceous, brown, black, blue, grey, yellow, purpuric, and others.

Palpation of lesions

  • Consistency: soft, firm, hard, fluctuant, board-like.
  • Temperature: cold or hot.
  • Mobility: consistent or inconsistent.
  • Tenderness: present or absent.
  • Depth: superficial, deep, or subcutaneous.

Skin Anatomy

  • The skin is composed of three main layers: epidermis, dermis, and hypodermis.
  • The epidermis is the outermost layer, derived from the ectoderm and is avascular.
  • The dermis is the middle layer, derived from the mesoderm and contains connective tissues, blood vessels, nerves, glands, and hair follicles.
  • The hypodermis is the deepest layer, composed of loose connective tissue and fat.
  • The epidermis is about 0.2 mm thick and consists of different types of cells:
    • Keratinocytes: The most abundant cells in the epidermis, responsible for producing keratin, a protein that strengthens the skin.
    • Melanocytes: Produce melanin, a pigment that gives skin its color and protects it from UV radiation.
    • Langerhans cells: Immune cells that help protect the skin from infection
    • Merkel cells: Sensory cells that help with touch sensation.
  • The dermis is thicker than the epidermis and contains:
    • Collagen: Provides strength and support to the skin
    • Elastic fibers: Provide flexibility and elasticity to the skin.
    • Blood vessels: Supply nutrients and oxygen to the skin and help regulate body temperature
    • Lymphatics: Drain excess fluid from the skin.
    • Nerves: Provide sensory information about touch, pain, temperature, and pressure to the brain.

Epidermal Layers

  • The epidermis has 5 distinct layers:
    • Stratum basale: The deepest layer, responsible for cell division and regeneration of the epidermis.
    • Stratum spinosum: Composed of cells that are connected by desmosomes, providing structural support to the skin.
    • Stratum granulosum: The cells in this layer begin to die and produce keratin.
    • Stratum lucidum: A thin, translucent layer found only in thick skin (e.g., palms and soles)
    • Stratum corneum: The outermost layer, composed of dead, keratinized cells that protect the underlying skin.
  • The dermo-epidermal junction is the interface between the epidermis and dermis. This junction helps to hold these two layers together.

Skin Appendages

  • The skin contains several appendages, including:
    • Hair follicles: Structures that produce hair, which is made of keratin.
    • Sweat glands: Produce sweat to regulate temperature.
      • Eccrine glands: The most common sweat glands in the body.
      • Apocrine glands: Found in specific areas of the body, such as the armpits and groin, and produce a thicker sweat.
    • Sebaceous glands: Produce sebum, an oily substance that lubricates and protects the skin.
    • Nails: Protective coverings made of keratin that grow from the nail matrix.

Skin Functions

  • The skin has many functions:
    • Protection: Forms a barrier against infections, injury, and UV radiation.
    • Temperature regulation: Sweating helps to cool the body, while blood vessel dilation and constriction help regulate blood flow.
    • Sensation: Provides information about touch, pain, temperature, and pressure.
    • Excretion: Sweat helps to eliminate waste products.
    • Vitamin D synthesis: UV light converts cholesterol in the skin into vitamin D.
    • Immune function: Langerhans cells help to protect the skin from infection.

Skin Disease Diagnosis

  • History - Provides details about the patient's symptoms, habits, and medical history.
  • Physical examination: Involves inspecting the skin, hair, nails, and mucous membranes for any abnormalities.
  • Primary lesions: The initial changes in the skin that occur as a result of a disease process.
  • Secondary lesions: Changes that occur in the skin as a result of the primary lesions or as a result of scratching or infection.
  • Diascopy: Helps differentiate between erythema and purpura by applying pressure on the skin to see if the redness disappears.

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Test your knowledge on the structure and function of the skin, focusing on the epidermis and dermis. This quiz covers various cell types such as keratinocytes, melanocytes, Langerhans cells, and Merkel cells, as well as their roles and characteristics. Perfect for students studying human anatomy or dermatology.

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