Questions and Answers
What is the primary structure that keratinocytes produce?
Which layer of the dermis is characterized by thick, irregular bundles of Type I collagen?
Which cells primarily originate from the mitosis of stem cells in the stratum basale?
What two functions do keratinocytes serve in the epidermis?
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What type of connections hold keratinocytes together?
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What causes the cytoplasm of immature keratinocytes to appear basophilic?
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What is the primary function of filaggrin and trichohyalin in keratinocytes?
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As keratinocytes move into the upper part of the stratum spinosum, what significant change occurs?
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In which layer do keratinocytes begin to synthesize keratohyalin granules?
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What do tonofilaments develop into as keratinocytes progress in their differentiation?
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Study Notes
Connective Tissue in Dermis
- Found in two layers: papillary layer and reticular layer.
- Papillary layer consists of thinned irregular bundles of Type I collagen and coarse elastic fibers.
Epidermis Cell Types
- Keratinocytes are the dominant cell type in the epidermis.
- Originate through mitosis of stem cells located in the stratum basale.
- Key functions include producing keratin (85% of fully differentiated keratinocytes) and forming an epidermal water barrier.
- Connected by desmosomes, contributing to epidermal structure.
Keratinocyte Development
- Immature keratinocytes near the stratum basale appear basophilic due to numerous ribosomes involved in keratin synthesis.
- As keratinocytes ascend to stratum spinosum, they produce tonofilaments, which group into tonofibrils, causing cells to appear more eosinophilic.
- Keratohyalin granules containing filaggrin and trichohyalin are synthesized in upper stratum spinosum, promoting keratin aggregation.
Hair Structure and Development
- Hair is a filamentous structure made of keratinized cells formed in hair follicles.
- Comprises concentric zones:
- Cuticle (outermost layer)
- Cortex (middle layer or inner layer in thin hair)
- Medulla (innermost layer, present in thick hair only).
- Hair formation occurs in the bulb of hair follicles with basal stem cells giving rise to cortex and cuticle.
Sweat Glands
- Eccrine glands contribute to thermoregulation by releasing sweat that cools the skin.
- Sweat is primarily an ultrafiltrate of blood, with sodium and water reabsorbed in the duct to produce hypotonic sweat.
- Eccrine glands are responsive to heat and emotional stimuli via the sympathetic nervous system.
Types of Cells in Eccrine Glands
- Clear cells are the main secretory cells, characterized by abundant glycogen and producing the watery component of sweat.
- Ducts lined by stratified squamous epithelium connect to hair follicles, facilitating sebum transfer to the skin.
Sebaceous Glands
- Develop as outgrowths of the external root sheath of hair follicles.
- Produce sebum through a holocrine secretion method, whereby cells fill with sebum and release upon apoptosis.
- Secretory cells accumulate lipids as they progress towards the gland opening, while basal cells serve as precursors in the secretory unit.
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Description
Test your knowledge on the connective tissue found in the dermis and the various cell types within the epidermis. This quiz covers the layers of connective tissue, the role of keratinocytes in skin structure, and their developmental stages. Perfect for understanding the foundational aspects of skin biology.
