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Questions and Answers
What percentage of body weight does the skin account for?
What percentage of body weight does the skin account for?
The hypodermis is considered a layer of the skin.
The hypodermis is considered a layer of the skin.
False
Name one function of the skin.
Name one function of the skin.
Protection
The outermost layer of the epidermis is called the __________.
The outermost layer of the epidermis is called the __________.
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Match the layers of the epidermis with their descriptions:
Match the layers of the epidermis with their descriptions:
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Which type of cell is responsible for skin color?
Which type of cell is responsible for skin color?
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Thick skin contains hair follicles.
Thick skin contains hair follicles.
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What are the two main layers of the dermis?
What are the two main layers of the dermis?
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______ cells are mechano-receptors found mainly in thick skin.
______ cells are mechano-receptors found mainly in thick skin.
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Match the following skin components with their descriptions:
Match the following skin components with their descriptions:
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Which pigment is responsible for dark hair?
Which pigment is responsible for dark hair?
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Merkel's cells are primarily located in thin skin.
Merkel's cells are primarily located in thin skin.
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What type of cells are Langerhans cells classified as?
What type of cells are Langerhans cells classified as?
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The two types of skin are thin skin and __________ skin.
The two types of skin are thin skin and __________ skin.
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Match the following skin types with their characteristics:
Match the following skin types with their characteristics:
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Which layer of the epidermis is only present in thick skin?
Which layer of the epidermis is only present in thick skin?
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The epidermis consists of loose connective tissue and fat cells.
The epidermis consists of loose connective tissue and fat cells.
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What type of cells are primarily found in the stratum basale?
What type of cells are primarily found in the stratum basale?
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The projections of the dermis that interdigitate with the epidermis are called __________.
The projections of the dermis that interdigitate with the epidermis are called __________.
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Match the following components of the epidermis with their functions:
Match the following components of the epidermis with their functions:
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Study Notes
Skin and Skin Appendages (Integumentary System)
- The skin is the body's largest organ, comprising about 16% of body weight.
- The skin consists of two primary layers: the epidermis and the dermis.
- The hypodermis is not a skin layer; it's composed of loose connective tissue and fat cells.
Objectives
- Define skin.
- Describe the structure of the epidermis.
- Detail the structure of the dermis.
- Compare thin and thick skin.
Introduction
- The junction between the dermis and epidermis is irregular, featuring dermal papillae (projections) and rete ridges (epidermal evaginations).
- Appendages like nails, hairs, sebaceous glands, and sweat glands arise from the epidermis.
Functions
- Serves as a receptor organ.
- Provides defense against microorganisms, chemicals, and ultraviolet radiation.
- Plays a role in vitamin D3 synthesis.
- Aids in personal identification (e.g., fingerprints).
I - The Epidermis
- Primarily composed of keratinized stratified squamous epithelium resting on a basement membrane.
- Consists of five layers from deep to superficial:
- Stratum basale: Single layer of basophilic columnar cells, active in epidermal turnover.
- Stratum spinosum (spongiosum): Polygonal cells with surface spin-like projections (keratin filaments and desmosomes).
- Stratum granulosum: Three layers of flattened polygonal cells, containing keratohyaline granules and lamellar bodies crucial for skin sealing.
- Stratum lucidum: Present only in thick skin, a translucent layer of flat cells lacking nuclei and organelles.
- Stratum corneum (horny layer): Multiple layers of flattened, non-nucleated eosinophilic cells filled with keratin.
Cells of the Epidermis
- Keratinocytes: Epithelial cells forming the stratified squamous keratinized epithelium; most numerous.
- Melanocytes: Produce melanin, giving skin color. Melanin granules migrate to keratinocytes. Pigments include eumelanin (dark hair) and pheomelanin (red hair). Melanocytes are found in the stratum basal and spinosum.
- Langerhans cells: Star-shaped cells mainly in the stratum spinosum, derived from macrophages, and are antigen-presenting cells (APCs).
- Merkel cells: Found primarily in thick skin, similar to epidermal epithelial cells but with dense granules; mechanoreceptors.
II - The Dermis
- Principally dense, irregular connective tissue, varying in thickness.
- Consists of two layers:
- Papillary dermis: Superficial layer.
- Reticular dermis: Deeper layer.
- Contains fibroblasts, mast cells, macrophages, and leukocytes.
- Houses hair follicles, sebaceous glands, and sweat glands (skin appendages), which originate from the epidermis. The dermis also plays a role in the formation of the basement membrane.
Types of Skin
- Thin skin: Covers most of the body, characterized by irregular dermal papillae, presence of skin appendages, and the absence of stratum lucidum.
- Thick skin: Located on palms and soles, features regular dermal papillae, lacks hair follicles and sebaceous glands, and presents stratum lucidum.
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Description
Test your knowledge on the structure and functions of human skin in this quiz. Explore topics such as skin layers, functions, and cell types. Challenge yourself to match descriptions with their corresponding skin components.
