Dr. Al Skin, Hair, Lip VMED 5127
Terms in this set (66)
What are 3 important functions of the skin (integument)?
1. Enclosing barrier
3. Vitamen D synthesis
What is the origin of the epidermis? dermis?
What are the 5 layers of epidermis stratum?
1. Stratum Corneum
2. Stratum Lucidum
3. Stratum Granulosum
4. Stratum Spinosum
5. Stratum Basale
2 Layers of the dermis
1. Papillary layer
2. Reticular layer
What does the thickness of the skin depend on? (4 things)
1. Region of the body
What are the 3 layers of the skin (simply)?
Stratum Basale (epidermis)
- Single layer of cubical or columnar epithelium
- Has STEM CELLS that divide to provide keratinocytes.
- Attached to stratum spinosum by (lateral) desmosomes.
- Attached to the basal membrane (at the dermoepidermal junction) by hemidesmosomes.
- COMMON SITE FOR BASAL CELL CARCINOMA. Due to ultraviolet radiation (SUV).
Stratum Spinosum (epidermis)
- The thickest layer of the epidermis
- Cells joined by desmosomes
- During tissue processing its cells shrink, which pulls at the DESMOSOMAL SPOTS and forms spine-like extensions= Prickle cell layer.
- Its top layer has lamellar granules= keratinization/cornification sign
What is the thickest layer of the epidermis?
What layer is the most common site of basal cell carcinoma in the skin?
Stratum Basale (epidermis)
- Has keratohyalin granules and lamellar granules.
- Keratohyalin granules contain the precursor to Fillagrin (which plays a role in keratinization and barrier function)
- Lamellar granules secrete a lipid-rich substance that coats the cell membrane of the Stratum Corneum and acts as a waterproof barrier and prevents nutrients from reaching the Stratum Corneum, causing its dlls to die.
- Thin, translucent layer
- Found in thick and hairless skin
- Cells lack organelles and nuclei
- Cells plasma membrane has involucrin protein (provides physical protection against microorganism and environmental injuring agents)
- Outermost layer
- Dead keratinized cells
- Its superficial cells are known as a Stratum Disjunctum (sheds continuously)
- Cells lack nuclei and organelles
- Dead cells are surrounded by involucrin protein (made in the Stratum Spinosum)
What does involucrin do? Where is it found?
- Provides structural support against microorganism invasion
- Found in cells plasma membrane in the Stratum Lucidum and surrounding deas cells in the Statum Corneum
What is the Stratum Malpighi?
- The Stratum Basale and the lower cells of the Stratum Spinosum form this mitotically active layer
What are the four epidermal resident cells?
3. Merckel Cells
4. Langerhan Cells
What is Filaggrin a clinical marker for?
Profilagrinn deficiency causes ---?
Which is a scale-like disease as fish skin.
- Largest cell population of the epidermis.
- Conatins keratinohyalin granules that contain profilaggrin (promote keratinization)
- Undergo keratinizaion as they move towards the skins surface.
- Eventually keratinize and slough off as Stratum Disjunctum
Where did Melanocytes originate?
The neural crest
- Origin= neural crest
- They settle between Stratum Basal cells.
- NO desmosomes
- Form hemidesmosomes with the basal lamina
- Contain and produce Melanosome granules (give color to the skin and hair).
- The enzyme Tyrosinase is processed by melanocytes
- Melanin granules occupy a supranuclear position to protect the nucleus from solar UV radiation.
What are the 2 pigment types found in melanocytes in the epidermis?
1. Eumelanin (dark brown)
2. Phaeomelanin (yellow/red- found in red hair)
What does the enzyme tyrosinase do? Where is it processed? How is it activated?
- This enzyme is necessary for melanin synthesis
- Albinos lack this enzyme
- It is processed by melanocytes in the epidermis
- Activated by ultraviolet light
Albinos lack the enzyme ----, therefore----.
- Lack tyrosinase
- so, melanocytes cannot produce melanin granules even though there is a normal amount of melanocytes.
- Epidermis resident cell
- Function as mechanoreceptors
- Have sensory nerve contacts called Merkel's Corpuscle
- Epidermis resident cells
- Participate in cutaneous immune reactions
- They are antigen-presenting cells to the T-lymphocytes
- Skin basement membrane zone
- Plays a role in maintaining epidermal-dermal adhesion
- Selective barrier between the epidermis and dermis
- Influences cell behavior in wound healing.
- Target for= skin injury and Bullosis diseases
- Bulla= vesicle/blister filled with blood or fluid.
- Like Herpes simplex
What 4 structures does the dermis contain?
1. SEBACEOUS glands
2. Sweat glands
3. Arrector pili muscles
4. Hair follicles
What are the 8 dermis resident cells?
2. Mast cells
5. Plasma cells
6. Fat cells
8. Chromatophores (color producing)
What are the 2 layers of the dermis?
1. Superficial Papillary layer
2. Deep Reticular layer
Superficial Papillary layer of the dermis.
- Loose connective tissue in contact with the epidermal stratum basal.
- The dermal papillary layer protrudes into the epidermis, forming the dermal papillae.
How are epidermal pegs (papillae) formed?
- By extension of the epidermis into the dermis
- Smooth muscle associated with hair follicles
What muscles are present in the dermis? What do they do?
1. Smooth muscles in scrotum, teat and penis
2. Arrector pili muscles (smooth muscle) associated with hair follicles
3. Skeletal muscle fibers of the cutaneous trunci penetrate the dermis and permit voluntary movement of the skin
- Not part of the skin
- Anchors the dermis to bone, muscle or cartilage.
- Has adipose tissue which forms a cushion or fat pad known as panniculus adiposis
- Structural fat in the hypodermis is a characteristic of the carpal, metacarpal, metatarsal and digital pad (acts as a shock absorber).
3 layers of the skin that blood vessels are located in?
1. Superficial layer
2. Middle layer
3. Deep layer
Nerve supply to the skin
Free nerve endings in the dermis, such as MEISSNER'S CORPUSCLES, are pressure mechanoreceptors
What 2 types of sweat glands are present in the skin?
1. Apocrine (apical part that chips off- smell)
2. Merocrine (cell stays intact and releases secretions)
What is the mode of secretion of the Sebaceous glands in the dermis?
- Whole cell disintegrates and becomes secretory material called sebum.
- Associated with hair follicle?
Apocrine sweat gland
- Has a coiled secreted portion and a straight duct
- The cells apical portions have various cytoplasmic extensions that indicate secreting activity.
- Myoepithelial cells surround the secretory unit.
- Secretion is viscous and contains scent, which is used as a sexual attractant, territorial marker or for communication.
- They don't secrete anything, used as storage.
- Their ducts open at the level of the anocutaneous junctions of the anus
- Modified sebaceous glands located around a dogs anus in the cutaneous zone.
- Site of canine tumors
What is the "hair shaft"?
The free part above the skin
What is the hair bulb?
- The terminal knob of the hair
- It houses the dermal papilla (vascular connective tissue)
What are the 3 layers of the hair shaft?
Histologically describe the hair cuticle
Keratinized, overlapping single cell layers
Histologically describe the cortex of hair.
Keratinized cells held together by desmosomes
Histologically describe the medulla of hair
Loose cuboidal cells
What does the dermal papilla do for hair?
- Provide nourishment
- It is located in the hair bulb
What does the hair matrix do?
- Covers the dermal papilla
- Provides hair layers. Produces hard keratin.
- Has melanocytes (provide hair pigment)
What are the 4 types of hair follicles?
Primary Hair Follicle
- Large diameter
- Associated with Sebaceous gland, Sweat gland and Arrector pili muscle
Simple Hair Follicle
- One hair emerges through one epidermal orifice
- In horses, cows and camels
Compound hair follicles
- One primary hair follicle surrounded by a group of secondary hair follicles.
- Up to 16 hairs pass through one orifice in the epidermis
- Dogs have these
Gray hair is due to the lack of the enzyme --- in melanocytes.
What is the telogen stage in the hair cycle?
- The resting phase
(After this stage, the new hair pushed the telogen hair upward toward the skin surface to be shed)
- During this stage, the hairs dermal papilla is out of the hair bulb
Matrix cells provide the hair --- and hair ---.
Hair layers and hair growth
What are the hair cycle stages? **
1. Anagen (active)
2. Catagen (transitional)
3. Telogen (resting)
List the seasons and their correlating "hair shedding" and "new hair coat" cycles.
- Fall= SHED
- Winter= NEW COAT
- Spring= SHED
- Summer= NEW COAT
How long does it take for a short hair dogs coat to regrow versus a long hair dog?
Short hair dog= 3 months
Long hair dog= 12 months
What does contraction of the arrestor pili muscle do?
- Provides insulation to maintain internal body temperature
- Errects hairs, which plays a role in emptying the SEBACEOUS GLANDS.
Sebaceous glands are not present in:
- Foot pads
- Acts as an ANTIMICROBIAL AGENT
- Act as a waterproofing agent in hairy mammals
- Their ducts open into the hair follicle
- Has sensory innervations
- Single hair follicles
What are the 6 types of stripes on a horses face?
2. Snip (star on nose)
4. Interupted stripe
5. Blaze (broad stripe)
6. White face
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