Integumentary System - Layers and Derivatives
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Questions and Answers

Which cell type in the epidermis is derived from monocytes and functions as antigen presenting cells?

  • Langerhans cells (correct)
  • Keratinocytes
  • Melanocytes
  • Merkel cells
  • What is the predominant cell type of the epidermis?

  • Langerhans cells
  • Melanocytes
  • Keratinocytes (correct)
  • Merkel cells
  • Where are Merkel cells mainly located in the skin?

  • Stratum lucidum
  • Stratum corneum
  • Stratum granulosum
  • Stratum basale (correct)
  • Which type of cells are described as neural crest derivatives that produce and distribute melanin into keratinocytes?

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

    In which layer of the dermis is the microvascular subpapillary plexus located?

    <p>Subpapillary plexus</p> Signup and view all the answers

    What is the main function of Langerhans cells in the epidermis?

    <p>Present antigens</p> Signup and view all the answers

    What is the main function of the epidermis?

    <p>Serving as a protective barrier</p> Signup and view all the answers

    Which cells in the epidermis are responsible for synthesizing pigment?

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

    What is the role of hypodermis in the skin?

    <p>Storing adipose tissue</p> Signup and view all the answers

    Which of the following is NOT a derivative of the skin?

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

    What is the main function of dermal papillae?

    <p>Connecting the dermis to the epidermis</p> Signup and view all the answers

    Which of the following is a key function of the skin's epidermal ridges?

    <p>Enhancing grip sensation</p> Signup and view all the answers

    What type of secretion do apocrine sweat glands exhibit?

    <p>Merocrine secretion</p> Signup and view all the answers

    When do the apocrine sweat glands become fully functional?

    <p>After puberty</p> Signup and view all the answers

    Which region of the body is largely associated with apocrine sweat glands?

    <p>Axillary and perineal</p> Signup and view all the answers

    What is the main function of sebum in relation to the skin?

    <p>Maintaining the stratum corneum</p> Signup and view all the answers

    What do the secretory components of apocrine glands look like?

    <p>Cells with large lumens and numerous secretory granules</p> Signup and view all the answers

    Where do the ducts of apocrine glands usually open?

    <p>Into hair follicles</p> Signup and view all the answers

    What is the outermost layer of the hair root called?

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

    Which part of the hair root completely surrounds the initial part but degenerates above the level of the attached sebaceous glands?

    <p>Internal root sheath</p> Signup and view all the answers

    In which layer of the hair bulb can two layers be recognized?

    <p>Epithelial root sheath</p> Signup and view all the answers

    What is the name of the hard plates of keratin on the dorsal surface of each distal phalanx?

    <p>Nail plate</p> Signup and view all the answers

    At what level does the external root sheath extend all the way to in the epidermis?

    <p>Basal layer</p> Signup and view all the answers

    How do hairs grow in terms of growth periods and rest periods?

    <p>At different rates in different regions</p> Signup and view all the answers

    What is the main difference between the papillary layer and the reticular layer of the skin?

    <p>The reticular layer consists of loose connective tissue while the papillary layer consists of dense irregular connective tissue.</p> Signup and view all the answers

    Which type of receptors are the unencapsulated Merkel cells in the skin?

    <p>Tonic receptors for light touch</p> Signup and view all the answers

    Where are free nerve endings primarily located in the epidermis?

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

    What is the main function of Pacinian corpuscles in the skin?

    <p>Specialized for coarse touch, pressure, and vibrations</p> Signup and view all the answers

    What is the function of root hair plexuses in the skin?

    <p>Detecting movements of the hairs</p> Signup and view all the answers

    Why are encapsulated mechanoreceptors considered phasic receptors?

    <p>They rapidly respond to stimuli on the skin</p> Signup and view all the answers

    Study Notes

    Skin Structure

    • The skin consists of two main layers: epidermis and dermis
    • Epidermis is the epithelial layer of ectodermal origin
    • Dermis is the layer of mesodermal connective tissue
    • Beneath the dermis lies the subcutaneous tissue or hypodermis, a loose connective tissue layer

    Epidermis

    • Composed of stratified squamous keratinized epithelium
    • Cells called keratinocytes make up the majority of the epidermis
    • Other cell types in the epidermis include:
      • Langerhans cells: antigen-presenting cells
      • Melanocytes: pigment-producing cells
      • Merkel cells: tactile epithelial cells

    Dermis

    • Consists of two layers: papillary layer and reticular layer
    • Papillary layer:
      • Thin
      • Includes dermal papillae
      • Composed of loose connective tissue
      • Contains types I and III collagen fibers, fibroblasts, and scattered mast cells, macrophages, and other leukocytes
    • Reticular layer:
      • Much thicker
      • Composed of dense irregular connective tissue
      • Contains a network of elastic fibers
      • Fewer cells than the papillary layer

    Subcutaneous Tissue (Hypodermis)

    • Consists of loose connective tissue
    • Binds the skin loosely to subjacent organs
    • Allows the skin to slide over underlying structures

    Epidermal Ridges and Dermal Papillae

    • Epidermal ridges: extensions of the epidermis into the dermis
    • Dermal papillae: connect the dermis to the epidermis

    Hair Follicles

    • Hair growth is asynchronous, cyclic, and occurs at different rates in different regions of the body
    • Hair growth cycle has three major phases
    • Hair follicles are surrounded by a web of sensory fibers called root hair plexuses that detect movements of the hairs
    • Each hair follicle has a hair root, a hair shaft, and a hair bulb
    • The hair root has a cortex, medulla, and cuticle

    Nails

    • Composed of heavily keratinized, densely packed cells
    • The nail plate is the hard plate of keratin on the dorsal surface of each distal phalanx
    • The proximal part of the nail is the nail root, which is covered by a fold of skin and the epidermal stratum corneum extends as the cuticle

    Sweat Glands

    • Apocrine sweat glands:
      • Confined to skin of the axillary and perineal regions
      • Development depends on sex hormones and is not complete and functional until after puberty
      • Produce pheromones
    • Eccrine glands:
      • Found all over the body
      • Produce sweat in response to heat, emotional stimuli, and other factors

    Skin Function

    • Thermoregulation: sweat production helps to cool the body
    • Metabolic: skin cells synthesize vitamin D3 through the local action of UV light on the vitamin's precursor
    • Protective: skin acts as a barrier against external factors
    • Sensory: skin contains various receptors that respond to different stimuli, such as touch, pressure, temperature, and pain

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    Description

    Learn about the layers and derivatives of the skin, specifically focusing on the epidermis and dermis. Explore structures like hair follicles, sweat glands, sebaceous glands, and nails, which are considered as separate organs or tissues. Dive into the thermoregulatory mechanisms for heat loss acceleration.

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