Integument Flashcards
What are the functions of the skin
-Protection
- Temperature regulation
- prevents water and electrolytes loss
- Energy storage
- Calcium Homeostasis
- Sensation
- Immune function
What are the components of the skin
Epidermis - stratified squamous keratinized epithelium
Dermis - Papillary layer and reticular layer
Hypodermis - loose connective tissue that may be rich in adipocytes —- panniculus adipose
Characteristics of skin layer epidermis
- Ectoderm derived
- avascular
- thick barrier
- composed of epithelium
Characteristics of skin layer dermis
-**. more active part of the cell
- mesoderm derived
- contains blood vessels and nerves
- composed of connective tissue
- supports the epidermis
Thick skin
Epidermis
Hairless
contains merocrine sweat glands
Paws pads and muzzles
Thin Skin
Epidermis is thin
Contains hair follicles often with the arrector pili
sebaceous and sweat glands
Thin Skin
Epidermis is thin
Contains hair follicles often with the arrector pili
sebaceous and sweat glands
What is the dermo-epidermal junction
interface between the dermis and the epidermis
What are the epidermal pegs/ridges
Part of the dermo-epidermal junction
- Downward projections of the deep epidermis into the dermis
What are the dermal papillae
Part of the dermo-epidermal junction
- Upward projections of the superficial dermis
- increase the surafce area of the layers
- provides blood supply closer to the epithelium
What are the two layers of the dermis?
Papillary layer and the reticular layer
Describe the papillary layer
Loose connective tissue
Type 1 and 3 collagen
Mast cells and macrophages
Vessels and Nerves
Describe the Reticular layers
Dense irregular CT
Type 1 collagen
Elastic fibres
Blood vessels and nerves
Cells of the epidermis
Keratinocytes
Langerhans cells - immunity
Merkles cells - mechanoreception
Melanocytes
What are the non-kerainocytes
Langerhans cells - immunity Merkles cells - mechanoreception Melanocytes
Describe the layers of the epidermis
- Stratum basale: active and alive
- Stratum spinosum: active and alive
- Stratum granulosum: non-active, alive
- Stratum lucidum (not always present): deceased
- Stratum corneum: very deceased
British & Spanish Grannies Lucidum Cornflacks
Desomosomes
bind neighbouring cells and connect intermediate filaments
Hemidesosomes
bind cells to the basement membrane or the basal lamina
Statum Basale
** ACTIVE and ALIVE
Deepest layer of the epidermis, located at the dermo-epidermal junction
- Single layer of cuboidal to columnar epithelium
- attached to the basal lamina via hemidesmosomes
- actively dividing
- Basal keratinocytes are functionally heterogenous. (stem cells or/and anchor the epidermis)
- may see melanocytes
Statum Spinosum
** ACTIVE AND ALIVE
- Cuboidal or slightly flattened
Thin skin: 1-2 cells-thick
Thick skin: many layers thic
- Increased number of tonofilaments and desmosomes give SPINY appearance
- Cells are cohesive and they resist abrasion
- Cells in this layer retain some capacity for the division if needed
What are tonofilaments
import of the intermediate filaments
Statum Granulosum
** NON- ACTIVE but ALIVE
- Layers that is 3-5 cells thick
- Cells begin to flatten
- Contain basophilic keratohyalin granules (bind with keratin filaments)
- 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
Where do Keratohyalin granules exist
primarily exist within the stratum granulosum
Stratum Lucidum
** NOT ALWAYS PRESENT; DEAD
- Translucent layer
- Present in thick skin only
- Many keratin filaments, desmosomes present
- Cellular organelles are gone – cells are fully keratinized
- Cytoplasm contains eleidin
What is eleidin
Densely packed and held together by a derivate of keratohylain which acts as a barrier to water and gives rise to its transparent or lucid properties
Statum Corneum
** DECEASED
- outermost layer
- many layers thick, thickness varies by location
- cells consist entirely of KERATIN, a water-resistance protein
- no nuclei or organelle
- HORNY cells surrounded by a thicker plasma membrane coated by the exterior lipid matrix
Keratinization
process by which keratinocytes differentiate, about 21 days in length in the dog
Cornification
Production of stratum corneum by terminal epidermal differentiation
formation of a dead cells (corneocytes) layer to create a physical barrier for the skin.
Where do you find Langerhans cells
Located in the startum basal and the stratum spinosum
Describe Langerhans cells
Endocrine Cells
- Stratum Basale and Spinosum
- Intra-epidermal (within the epidermis)
What are Langerhan cells derived from?
Bone Marrow monocytes
Langerhans cells role?
Immunity
- Antigen-presenting t-cells and mediator of tolerance
** not often seen with routine H&E
Where are merkel cells located?
Stratum Basale of thick skin - connected to adjacent keratinocytes via desmosomes
Merkle’s cells role?
Act as sensory mechanoreceptor for cutaneous sensation
Attract nerve ending and stimulate growth
- Free nerve endings seen at the base of these cells
Where are melanocytes presented?
Stratum Basale and originate from neural crest
What are the roles of melanocytes pigments
migrates within cytoplasmic extensions and transferred to keratinocytes of stratum basale and spinosum
Protects 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
keeps the generation of free radicals at a minimum
What is a sensory nerve of the dermis
Nociceptors - free nerve ending that reach the stratum granulosum. Detect: pain, itch and temperature
Meissner’s corpuscles: light
pressure/touch
Pacinian corpuscle: deep pressure
Ruffini corpuscle: senses stretch
Functions of hair and feathers
Insulation, camouflage, social display, sense/protect, sex recognition
How is hair produced
a hair follicle
Hair shaft
Above the surface of the skin
Hair root
Within the follicle and ends with the bulb
Components of the hair
Medulla - loose cuboidal cells with areas of air
Cortex - dense compact keratinized cells
cuticle - single layer of flat keratinized cells
Describe the anatomy of a hair follicle
Invagination of the epidermis
the basement membrane is thickened (glassy)
the hair root is within the follicle and ends with a bulb
Root Sheath of the hair follicle
- External glassy membrane = basal lamina
- External root sheath – continuous with epidermis
- internal root sheath – a few layers of squamous cells
- Cuticle – internal to internal root sheath; formed by overlapping keratinized cells but in the opposite direction from the hair cuticle
Anagen
hair bulbs = mitotically active
Catagen
Regressive stage when metabolic activity slows down and the base of the follicle migrates towards the surface
Telogen
Resting phase when growth stops, and the base of the bulb is at the level of the sebaceous canal
- new hair grown beneath the telogen follicles and old hair shaft is shed
controlled by daylight, ambient temperature, nutrition, and hormones (estrogen, testosterone, adrenal steroids, and thyroid hormone)
Primary Hair follicle
Large Diameter
Rooted dermis
Sebaceous gland, arrector pili muscle, sweat glands
Primary or Hair guard
Secondary Hair follicle
- Smaller diameter
- Rooted nearer the surface
+/-sebaceous gland; no sweat glands, no arrector pili
muscle
- Secondary or under hairs
Compound follicles
Clusters of hair follicles
The follicles merge at the level of the sebaceous gland and emerge though one external orifice
Usually one primary follicle and several secondary hair follicle
Arrector Pilli
Smooth muscle attached to follicles of primary hair
Contraction of this muscle causes hair to stand up
** plays a role in insulation
Sinus Hair 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
Sebaceous gland
- Located in the dermis
- Produce sebum a mixture of lipid and cell debris
- Holocrine secretion (secreted by rupture in the plasma membrane)
- Antibacterial and waterproofing
- Ducts empty into a follicle
- Can be simple, branched or compound glands
Uropygial/ Preen gland
Strongly developed in many water birds such as ducks
produces an oily, waxy substance that helps waterproof feathers and keep them flexible.
Apocrine Sweat glands
- Secret by apical budding/pinches
- Epithelial cells have apical secretory caps (a)
- Simple saccular or tubular glands with coiled secretory portion and straight duct with opens into the distal hair follicle.
- Contractile myoepithelial cells (m) help express the product
- In domestic animals, located throughout most of the skin.
-Function is mainly communication (attraction, marker).
Merocrine Sweat glands
- Merocrine – excrete via exocytosis
- Open directly on to skin surface vs hair follicle * Minor in domestic animals
- Thermoregulation and electrolyte balance; Secrete fluid onto skin surface when body temperature rises
Desribe Hoove and Claws
Modification of skin, variation of the stratum corneum, underlain by highly vascular dermis,
Lack stratum granulsom and lucidum
What is the purpose of the hoof
A highly specialized skin derivative that protects and encloses the end of the digit of an ungulate mammal
Two main layers of the hoof
outer epidemis
the underlying dermis (corium)
What are the layers of the Hoof Wall?
Stratum Ecternum
Stratum medium
Stratum Lamellatum/Internum
Laminar Corium
Everyone must like cornflakes
Stratum Ecternum
External layer known as “glaze”
Continuation of perioplic epidermis
Stratum medium
Main supportive layer
Tubular and intertubular horn produced by the stratum basle and spinosum of the epidermis of the coronary groove
Stratum Ecternum
Lamellar horn (insensitive)
Stratum Corium
Sensitive
