Histo - Skin Flashcards
What are the 5 Functions of Skin?
-
Protection from…
- abrasion, water loss/gain, bacterial invasion, sunlight
- Sensory
-
Thermoregulatory
- Either insulation or mechanism for heat loss
-
Metabolic
- Vitamin D
-
Sexual signaling
- Visual or pheromones
What are the 3 Layers of Skin (Integument)?
-
Epidermis
- Keratinized SS
- Epidermal ridges
- Keratinized SS
-
Dermis
- Papillary dermis (loose CT)
- Reticular dermis (dense irregular CT)
- Dermal papillae
-
Hypodermis
- Loose CT
- Abundant fat
- Subcutaneous tissue = superficial fascia
What are the 2 Types of Skin?
-
Thick skin
- Example: palm/foot
- thicker keratin
- no hair follicles
- Example: palm/foot
-
Thin skin
- Example: arms/legs
- thinner keratin
- hair follicles
- Example: arms/legs
What type of skin is this?

Thin skin
What type of skin is this?
Thick skin
Identify the 3 layers of skin
What are the 5 Layers of Epidermis?
Basics:
- Main cells = keratinocytes
Layers:
-
Stratum Basale = cuboidal or columnar cells
- Proliferative
- Binds BL via hemidesmosomes & integrins
- Binds BL vs anchoring fibrils of Type VII collagen
-
Stratum Spinosum
- Lower layer = proliferative
- Numerous desmosomes & tight junctions
-
Stratum Granulosum
- Filled w/ keratohyline granules
- Filaggin/cytokeratin
- Lamellar granules (exocytosed)
- Lipids/glycolipid
- Filled w/ keratohyline granules
-
Stratum Lucidum (Anucleated)
- only in THICK skin
-
Stratum Corneum (Anucleated)
- form the keratin layer
- dead squames filled w/ cytokeratin
- surrounded by protective layer
What are the layers can you see in this image?
What is this?
Keratinocytes in Stratum Spinosum
What can we see in this picture?

- C = Stratum corneum
- L = Stratum lucidum
- G = Stratum granulosum
- S = Stratum spinosum
What are the 5 Main Issues with the Skin that can arise?
-
Blisters
- Friction blisters
- Blistering diseases
- bullus pemphigoid (hemidesmosome disruption)
- pemphigus (autoimmune–> damage to keratinocyte jxns)
-
Cancers
- Basal cell carcinoma
- Squamous cell carcinoma
- Merkel cell (tactile) carcinoma
-
Psoriasis
- increased proliferation & differentiation
-
Pigment disorders
- albinism
- vitiligo (loss of pigment)
-
Moles or Nevi
- from melanocytes
What are the 3 other cells found in the Epidermis?
-
Melanocytes
- Derivative: Neural crest
-
Location: Stratum Basale
- 1 per 5-6 keratinocytes
- Pale staining
-
Structure: Long Projections/granules
- Extend into invaginations of keratinocytes
-
Function: cytocrine secretion
- inject melanin –> keratinocytes
- cluster over nucleus & protect from UV
-
Langerhans Cells
- Derivative: Monoocytes
-
Location: Stratum Spinosum (mostly)
- Rare/difficult to see
- Structure: Dendritic cells
- Function: Ag presenting cell
-
Merkel Cells
- AKA: Epithelial tactile cells
- Location: Stratum Basale
-
Structure: look like keratinocytes (but no melanin)
- dense core granules
- mechanoreceptors
-
Fucnction: light touch/texture
- base interacts w/ unmyelinated sensory fibers
What cell type is this?
Langerhans Cells
What cell type is this?
Merkel Cells
What cell type is this?
Melanocytes
What are the 2 Layers of the Dermis?
-
Papillary layer
- Loose CT
- Made from:
- Collagens I & III
- Elastic fibers
- Fibroblasts
- Other cells
-
Reticular layer
- Dense Irregular CT
- Made from:
- Collagen I
- Elastic fibers
Notes:
-
Highly innervated
- Tactile receptors
-
Can include:
- Sweat glands
- Hair follicles
- Blood vessels
- Immume cells
What are the 3 Plexi of the Dermis/Hypodermis?
-
Subpapullary plexus
- Btw papillary & reticular layers
- Extends INTO papillary layer
- Thermoregulatory
- AV shunts
-
Dermal/Cutaneous plexus
- within the Dermis
-
Deep plexus
- Btw Dermis & Hypodermis

What features of the dermis can you see?

-
Dermis showing Elastic Fibers
- Elastic stain w/ fibers darkly stained
- Diameter decreases closer to epidermis
- Insert into BL
What are the 7 Tactile Receptors in Skin?
-
Free nerve endings
- Tactile
- Light touch
- Pain
- Temp extremes
- Itching
-
Nerve fibers w/ tactile discs
- interact w/ Merkel cells
-
Root hair plexus
- Nerve senses movement of hair & touch
-
Krause end bulbs
- Nerve senses low freq. vibration or movement
- Mainly on penis/clitoris
-
Ruffini corpuscles
- Tissue distortion
-
*Meissner’s corpuscle
- Light touch
- Papillary dermims
- Most numerous in fingertips, palms, feet
- how we use braille
-
*Pacinian corpuscle
- Pressue & high-freq vibration
- In deep dermis/hyperdermis
* = only tactile receptors that can be easily identified histologically
What are the Characteristics of Hair?
Basics:
- Long, keratinized structures
- Made via hair follicles
- Location: thin skin (w/ exceptions)
- Originates: in the Dermis –> Epidermis
- Arrector pili (smooth muscle)
- make hair “stand on end”
Hair Follicles:
- Dermal papilla = hair
- Root + bulb
- Matrix, medulla, cortex of root
- Have stem cells
- can regenerate keratinocytes
- Melanocytes = cause hair pigmentation
What are the 3 Stages of Hair Growth?
-
Anagen
- Growing hair (length)
-
Catagen
- Arrests growth
- Hair regresses
-
Telogen
- Hair is lost
- Causes alopecia (baldness)
What are the Characteristics of Nails?
Basics:
-
Nail root
- covered by eponychium (cuticle)
-
Nail plate
- Hard keratin
- Has lunula (white semi-circle)
-
Nail bed
- Has only basal & spiny layers of dermis
Growth:
- Fom nail matrix
- most proximal part of nail
- Hyponychium
- “Free” nail is no longer connected to the skin
What parts of the nail can we see?

What are the 3 Glands in the Skin?
-
Sebaceous glands (aka Sebocytes)
- Thin skin (mostly)
- Secrete = Sebum
- Holocrine secretion
- Looks like clusters of squamous cells (fried eggs)
- Secreted into hair follicles
- Can be antibacterial/antifungal
- Gland can look scalloped
-
Eccine sweat glands
- Round/Oval acinar organization of cells
- around central lumen
- can be stratified
- Secretory part
- Merocine section
- Dermis/Hypodermis
- More lightly stained than ducts
- Duct part
- secretory part to surface of the skin
- open at sweat pore
- Round/Oval acinar organization of cells
-
Apocrine sweat glands
- Round/oval acinar organization
- cells around central lumen
- Larger lumen than eccrine sweat glands
- develop in presense of sex hormones (after puberty)
- Secretory part
- MEROCRINE secretion
- Apical part of duct = opens into hair follicles
- not skin surface
- Round/oval acinar organization
What is this?

Apocrine Sweat Glands
What is this?
Eccrine Sweat Glands
What is this?
Sebaceous Glands