Integument Semester 1 lecture
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Questions and Answers

What function does hair serve in addition to insulation and camouflage?

  • Regulation of body temperature
  • Detection of pain and itch
  • Secretion of sebum
  • Social display and sense/protect (correct)

    • What is the function of Meissner's corpuscles?

  • Detection of deep pressure
  • Detection of stretch
  • Detection of light pressure/touch (correct)
  • Detection of itch and temperature

    • What is produced by a hair follicle?

  • Sebum
  • Keratin
  • Sweat
  • Hair shaft (correct)

    • What is the function of Ruffini corpuscles?

    <p>Detection of stretch</p> Signup and view all the answers

    What is the function of apocrine sweat glands?

    <p>Sweat production</p> Signup and view all the answers

    What is the function of sebaceous glands?

    <p>Production of sebum</p> Signup and view all the answers

    What is the location of the hair root?

    <p>Within the hair follicle</p> Signup and view all the answers

    What is the function of hair in terms of social behavior?

    <p>Social display</p> Signup and view all the answers

    What is the primary function of hemidesmosomes?

    <p>Binding cells to basal lamina</p> Signup and view all the answers

    What is the characteristic of cells in the Stratum Spinosum?

    <p>They retain some capacity for division</p> Signup and view all the answers

    What is the function of lamellar granules?

    <p>To secrete waterproof lipid sheets</p> Signup and view all the answers

    Which layer is present in thick skin only?

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

    What is the main component of cells in the Stratum Corneum?

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

    What is the process by which keratinocytes differentiate?

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

    What is the definition of Cornification?

    <p>The production of stratum corneum by terminal epidermal differentiation</p> Signup and view all the answers

    What is the purpose of desmosomes in the Stratum Spinosum?

    <p>To increase cell cohesion</p> Signup and view all the answers

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

    <p>To present antigens to T-Cells and mediate tolerance</p> Signup and view all the answers

    Where are Merkel's cells typically located in the skin?

    <p>In the stratum basale of thick skin</p> Signup and view all the answers

    What is the origin of melanocytes in the skin?

    <p>Neural crest</p> Signup and view all the answers

    What is the role of tyrosinase in melanocytes?

    <p>To produce melanin pigment</p> Signup and view all the answers

    What is the function of melanin in the skin?

    <p>To absorb harmful UV radiation</p> Signup and view all the answers

    What type of nerve endings are seen at the base of Merkel's cells?

    <p>Free nerve endings</p> Signup and view all the answers

    What is the role of Langerhans cells in antigen presentation?

    <p>They process and present antigens to T-Cells</p> Signup and view all the answers

    What is the purpose of immunohistochemistry in relation to Langerhans cells?

    <p>To identify macrophages</p> Signup and view all the answers

    What is the characteristic of compound follicles?

    <p>They merge at the level of the sebaceous gland</p> Signup and view all the answers

    What is the role of the arrector pili muscle?

    <p>To cause hair to stand up</p> Signup and view all the answers

    What is the characteristic of sinus hairs/whiskers?

    <p>They have a blood-filled sinus between the inner and outer dermal root sheath</p> Signup and view all the answers

    What is the mode of secretion of sebaceous glands?

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

    What is the function of the uropygial gland?

    <p>To aid in preening and waterproofing in birds</p> Signup and view all the answers

    What is the characteristic of apocrine sweat glands?

    <p>They secrete by apical budding or pinches</p> Signup and view all the answers

    What is the location of the apocrine sweat glands?

    <p>Throughout most of the skin in domestic animals</p> Signup and view all the answers

    What is the role of the myoepithelial cells in apocrine sweat glands?

    <p>To help express the secretory product</p> Signup and view all the answers

    What is the main characteristic of the skin that forms the equine hoof?

    <p>It is heavily keratinized</p> Signup and view all the answers

    Which layer of the skin is absent in the equine hoof?

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

    What is the term for the junction where the hoof wall meets the sole?

    <p>White line</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the equine hoof?

    <p>It has a thick stratum lucidum</p> Signup and view all the answers

    What is the term for the layer of skin that is rich in blood vessels and supports the epidermis?

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

    What is the function of the coronary band in the equine hoof?

    <p>It marks the boundary of the hoof wall and sole</p> Signup and view all the answers

    What is the term for the hard, outer layer of the epidermis that forms the hoof?

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

    Which of the following is a characteristic of the skin that forms the equine hoof?

    <p>It is heavily keratinized</p> Signup and view all the answers

    What is the term for the sensitive layer of skin that meets the insensitive layer of the hoof?

    <p>Sensitive laminae</p> Signup and view all the answers

    Which of the following is a characteristic of the distal phalanx in the equine hoof?

    <p>It is a bone that encases the hoof</p> Signup and view all the answers

    What percentage of hairs are in the telogen phase?

    <p>10-15%</p> Signup and view all the answers

    Where are nociceptors found in hair follicles?

    <p>In the follicular epithelium and dermal sheath</p> Signup and view all the answers

    What is one of the functions of nociceptors in hair follicles?

    <p>To regulate hair growth and cycling</p> Signup and view all the answers

    Integument = ______________ + _________________

    <p>Integument = Skin + Epidermal Derivatives</p> Signup and view all the answers

    What are examples of epidermal derivatives?

    <p>Foot pads, claws, hooves, horns, glands (including anal sacs), uropygial gland (birds), wattles, combs, spurs and feathers.</p> Signup and view all the answers

    List the functions of the skin (Hint: 9 total)

    <p>Protection, Prevents water and electrolyte loss, calcium homeostasis, energy storage, sensation, temperature regulation, and immune regulation</p> Signup and view all the answers

    What type of epithelium is found in the epidermis?

    <p>Stratified squamous keratinized epithelium</p> Signup and view all the answers

    Which layer of the skin contains loose connective tissue and may be rich in adipocytes?

    <p>Hypodermis (subcutis)</p> Signup and view all the answers

    Which layer of the dermis is located closest to the epidermis?

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

    Which of the following correctly describes the dermis?

    <p>Contains papillary and reticular layers</p> Signup and view all the answers

    What is the primary characteristic of the hypodermis?

    <p>It may be rich in adipocytes.</p> Signup and view all the answers

    Thick skin characteristics include: thick epidermis, hair is present, and it contains merocrine/eccrine sweat glands

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

    Examples of thick skin include paw pads and muzzle

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

    What type of glands are present in thin skin? (More than one may apply)

    <p>Apocrine sweat glands</p> Signup and view all the answers

    What is the structure that separates the dermis from the epidermis?

    <p>Basement membrane</p> Signup and view all the answers

    Which of the following structures increases the surface area between the dermis and epidermis?

    <p>Dermal papillae</p> Signup and view all the answers

    Where are examples of the dermo-epidermal junction typically found?

    <p>Footpads and nasal planum</p> Signup and view all the answers

    What are downward projections of the deep epidermis called?

    <p>Epidermal pegs</p> Signup and view all the answers

    What role do dermal papillae serve in relation to the epithelium?

    <p>Bring blood supply closer to the epithelium</p> Signup and view all the answers

    What are the two zones in the dermis?

    <p>The two zones are the papillary and reticular zones.</p> Signup and view all the answers

    The papillary zone is the superficial layer, comprised of dense irregular connective tissue whereas the reticular zone is the deep layer that’s comprised of loose connective tissue

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

    The papillary zone is especially prominent in thick skin

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

    What are the two types of cells OF the epidermis.

    <p>Keratinocytes and non keratinocytes</p> Signup and view all the answers

    What is the most common cell in the epidermis?

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

    Which of the following are non-keratinocyte cells of the epidermis?

    <p>All the above</p> Signup and view all the answers

    The epidermis is composed of several distinct layers. List the layers in order from DEEP to Superficial

    <p>Stratum basale, Stratum spinosum, Stratum granulosum, Stratum lucidum, Stratum corneum</p> Signup and view all the answers

    Match the correct function the cell carries out.

    <p>Langerhan cells = Immunity Merkel cells = Mechanoreception Melanocytes = UV protection Free bee = Free bee</p> Signup and view all the answers

    Match the epidermal layer to its correct description of activity of cells.

    <p>Stratum basale = Very active and alive Stratum spinosum = Active and alive Stratum granulosum = Non active, alive Stratum corneum = Very deceased</p> Signup and view all the answers

    Langerhan cells are often seen with H & E

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

    Study Notes

    Sensory Receptors

    • Detect pain, itch, and temperature through encapsulated nerve endings
    • Meissner's corpuscles detect light pressure/touch
    • Pacinian corpuscle detects deep pressure
    • Ruffini corpuscle senses stretch

    Epidermal Structures/Derivatives

    • Hair follicles
      • Compound hair follicles
      • Sinus (tactile) hairs
    • Sebaceous glands
    • Apocrine (sweat) glands
    • Udders, mammary glands
    • Hooves, claws, nails
    • Footpads (with merocrine/eccrine sweat glands)
    • Anal sac glands and anal sacs
    • Circumanal glands (hepatoid glands)

    Functions of Hair/Feathers

    • Insulation
    • Camouflage
    • Social display
    • Sense/protect
    • Sex recognition

    Anatomy of Hair

    • Produced by a hair follicle
    • Hair shaft above the skin surface
    • Hair root within the follicle, ending with a bulb
    • Hemidesmosomes bind cells to the basal lamina
    • Desmosomes bind neighboring cells together
    • Both connect to intermediate filaments

    Stratum Spinosum

    • Polygonal cells, 1-2 cells thick in thin skin, many layers thick in thick skin
    • Increased number of tonofilaments (cytokeratin) and desmosomes give a spiny appearance
    • Cells are cohesive and resist abrasion
    • Cells in this layer retain some capacity for division if needed

    Stratum Granulosum

    • 3-5 cells thick
    • Cells begin to flatten
    • Contain basophilic keratohyalin granules
    • Lamellar granules (not visible via light microscopy) secreted by cells to form waterproof lipid sheets, “intercellular cement”
    • No mitotic activity, last living layer, nucleus and organelles soon to be lost

    Stratum Lucidum

    • Translucent layer
    • Present in thick skin only
    • Many keratin filaments, desmosomes present
    • Cellular organelles are gone – cells are fully keratinized
    • Cytoplasm contains eleidin – protein chemically related to keratin

    Stratum Corneum

    • Outermost layer
    • Many (up to 20) layers thick, thickness varies by location
    • Cells consist entirely of keratin, a water-resistant protein
    • No nuclei or organelles
    • Cells continually shed at the surface

    Keratinization

    • Process by which keratinocytes differentiate, taking around 21 days in dogs
    • Cornification: Production of stratum corneum by terminal epidermal differentiation

    Non-Keratinocytes of the Epidermis

    • Langerhans cells – immune system
    • Merkel’s cells – sensory
    • Melanocytes – protection

    Langerhans Cells

    • Intra-epidermal (within the epidermis) macrophages
    • Derived from bone-marrow monocytes
    • Role in immunity: antigen presenting to T-cells, mediators of tolerance
    • Not often seen with routine H&E, use immunohistochemistry to identify

    Merkel’s Cells

    • Located in the stratum basale of thick skin
    • Can act as sensory mechanoreceptors for cutaneous sensation
    • Free nerve endings seen at the base of these cells

    Melanocytes

    • Present in the stratum basale
    • Neural crest origin
    • Produce melanin pigment for keratinocytes of stratum basale and spinosum
    • Protect cells from effects of UV radiation
    • Must have tyrosinase for proper function

    Melanin

    • Absorbs harmful UV-radiation
    • Transforms the energy into harmless amounts of heat
    • Must have tyrosinase for proper function

    Sensory Nerves of the Dermis

    • Nociceptors – free nerve endings that reach the stratum granulosum

    Compound Follicles

    • Clusters of several hair follicles
    • Follicles merge at the level of the sebaceous gland and emerge through one external orifice
    • Compound follicles usually have one primary follicle with an apocrine sweat gland and several secondary hair follicles
    • Common in carnivores

    Arrector Pili

    • Smooth muscle attached to follicle of primary hairs
    • Contraction causes hair to stand up (goosebumps)
    • Role in insulation
    • ANS controls this

    Sinus Hairs/Whiskers

    • Tactile hairs
    • Composed of a very large single follicle
    • Blood-filled sinus between inner and outer dermal root sheath
    • Attached to skeletal muscle to allow for voluntary movement
    • Nerve bundles penetrate sheath

    Sebaceous Glands

    • Located in the dermis
    • Produce sebum, a mixture of lipid and cell debris
    • Holocrine secretion
    • Antibacterial and waterproofing
    • Ducts empty into a follicle
    • Can be simple, branched, or compound glands

    Specialized Sebaceous Glands

    • Supracaudal glands – dog
    • Circumanal/Hepatoid glands
    • Mental organs/glands – cat
    • Horn glands – buck goat
    • Preputial glands – smegma in horse
    • Tarsal (Meibomian) glands – eyelids
    • Uropygial gland (the preen gland) in birds

    Uropygial/Preen Gland

    • Strongly developed in many waterbirds, such as ducks
    • The rest of bird skin is aglandular

    Apocrine Sweat Glands

    • Secrete by apical budding/pinches
    • Epithelial cells have apical secretory caps
    • Simple coiled tubular glands open into the distal hair follicle
    • Contractile myoepithelial cells help express the product
    • In domestic animals, located throughout most of the skin
    • Function is mainly communication (attraction, marker)

    Hooves and Claws

    • Modification of skin
    • Variation of the stratum corneum
    • Supported by highly vascular dermis
    • Lack stratum granulosum and stratum lucidum

    Hair Growth Cycles

    • Hair growth consists of three phases: anagen, catagen, and telogen.
    • Anagen phase lasts around 2-3 years, during which hair grows approximately 1 cm per month.
    • The majority of hairs (80-90%) are in the anagen phase.
    • Catagen phase is a short transitional phase lasting around 2-3 weeks, where hair growth slows down.
    • Only 3-4% of hairs are in the catagen phase.
    • Telogen phase is a resting phase lasting around 3-4 months, where hair is released from the follicle and a new hair grows from the same follicle.
    • 10-15% of hairs are in the telogen phase.

    Nociceptors in Hair Follicles

    • Nociceptors are sensory neurons that detect painful stimuli.
    • In hair follicles, nociceptors are found in the follicular epithelium and the surrounding dermal sheath.
    • Nociceptors in hair follicles detect mechanical and chemical stimuli, such as hair pulling or irritation.
    • They regulate hair growth and cycling through the release of neurotransmitters.
    • Nociceptors may play a role in the development of hair disorders, such as alopecia areata.

    Components of Skin

    • Epidermis: Comprised of stratified squamous keratinized epithelium, providing a protective barrier against environmental damage and pathogens.
    • Dermis: Divided into two layers:
      • Papillary Layer: Upper layer containing loose connective tissue with dermal papillae that interlock with the epidermis, enhancing nutrient supply and sensory function.
      • Reticular Layer: Deeper layer made up of dense irregular connective tissue, providing strength and elasticity to the skin due to the presence of collagen and elastin fibers.
    • Hypodermis (Subcutis): Also known as subcutaneous tissue, it consists of loose connective tissue, which may be rich in adipocytes (fat cells), forming the panniculus adiposus that provides insulation, energy storage, and cushioning for underlying structures.

    Dermo-Epidermal Junction

    • Acts as the interface between the dermis and epidermis.
    • Serves as the site where the basement membrane is split.

    Epidermal Pegs/Ridges

    • Comprised of downward projections of the deep epidermis into the dermis.
    • Contributes to the structural integrity and support of the skin.

    Dermal Papillae

    • Formed by upward projections of the superficial dermis.
    • Increases surface area between the dermis and epidermis, enhancing adhesion.
    • Brings blood supply closer to the epithelium, supporting nutrient delivery and oxygenation.

    Specific Examples

    • Dermo-epidermal junctions are notably present in footpads, nasal planum, and scrotum.
    • Particularly found in areas subjected to traction, providing resilience.
    • Not commonly observed in areas with haired skin, highlighting its specialized function.

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