Skin and Sensory Receptors Flashcards
The skin makes up what percentage of total body weight
15-20% of total body weight is skin
Three main layers of the skin
- Epidermis - what you can actually touch.
- Dermis
- Hypodermis or subcutaneous tissue
Epidermis
- Tissue type
- Main cell type
- Special cell types
- Are nerves present?
Epidermis- SSK epithelium. Main cell is keratinocytes (80%) and other cells include melanocytes, lagerhans, and merkel cells (light touch sensory receptors). Contains free nerve endings (typically pain receptors)
Dermis
- Tissue type
- Are vessels present?
- Are glands present?
Dermis- Dense irregular connective tissue with several types of sensory receptors such as Meissner’s corpuscle and pacinian corpuscle.
Small vessels (arterioles and venues) and lymphatics (run alongside vein system) are present.
Glands: sweat and sebaceous (associated with hair follicle)
Piloerector units- Hair follicle, sebaceous gland, and errector pili muscle
Role of the errector pili muscle
Muscle associated with hair follicle. Stands hair up when scared or cold
Meissner’s corpuscle
Sensory receptor found in the superior dermis (papillary layer). Detects light touch.
Only in thick skin.
Pacinian corpuscle
Found in the deep dermis (reticular dermis). Detects vibrations and heavy touch.
Only in thick skin.
Piloerctor units includes
- Hair follicle
- Errector pilli muscle
- Sebaceous gland
Adipose tissue
- Tissue type?
- What is found in this layer?
Loose connective tissue and adipose tissue.
Large(r) blood vessels (arteries and veins), lymphatics, and nerves
What does it look like histologically where the epidermis and dermis meet?
Squiggly appearance, not a straight line. Increases surface area of contact and creates friction so it is hard to separate the two layers.
Glabrous
Hairless
Difference between thick and thin epidermis
Thick- Smooth, glabrous (hairless) with 5 layers. Palms of hand and soles of feet.
Thin- Thin, hairy, has 4 layers (strata= layer)
Layers of the epidermis
Big spiders get (L) crushed
Basale- Adjacent to basement membrane. Single layer of cells. Cube shaped appearance. Innermost layer with keratinocytes that are highly mitotically active.
Spinosum- Stellate shaped cells. Cell with a bunch of spine. Cell to cell junctions are forming. Mitotically active, but less than basale.
Granulosum- Cells become more flattened like stratified squamous. Keratin is now produced. Stained well with hematoxylin.
Lucidium- Only found in thick skin. Cell is pretty much dead, no nucleus. Too far away from blood supply. Appears pale, white.
Corneum- Super dead cells. No nucleus. Shloffed off.
Is the epidermis vascular or avascular
Avascular. Gets its blood supply from the underlying dermis.
Waterproofing
As the cell mitosis, lamellar granule lipids are secreted into the intercellular space between cells. The lipid barrier waterproofs the skin, preventing water loss to evaporation. Lasts until the cell it surrounds are shed off.
Waterproofing occurs in which layer of the skin
The epidermis. Released at the basale cell layer as cells go through mitosis.
Cell bodies and cytoplasmic extensions of melanocytes are located where
Cell bodies are located in the stream basale with their cytoplasmic extensions into the stratum spinosum. Granules of melanin are released from the cytoplasmic extensions.
Does sex and race have any influence on the number of melanocytes?
No.
How are melanocytes bound to the stratum basale?
Bound to underlying basal lamina of the stratum basale layer via hemidesmosomes.
UNLESS you have a melanoma. Then located elsewhere.
Role of melanocytes in skin
Granules absorb UV light/radiation.
Langerhans cells are typically found where?
Star-shaped cell located within the stratum basale and spinous.
APC type of dendritic cells derived from bone marrow (monocytes)
Langerhans are a type of ___ cell
Dendritic cell, which is derived from monocytes in the bone marrow.
Hair follicles found in the dermis are composed of which tissue type?
Hair follicles are invaginations of the epidermis into the dermis. If you look at the wall of the hair follicle, it will be the same as the epidermis, which is stratified squamous.
The erector pill muscle is which type of muscle tissue
Smooth. Involuntary.
Two layers of the dermis
Superior papillary layer immediately adjacent to the epidermis. Provides mechanical anchorage to the epidermis. Contains Meisser’s corpuscle.
Deep reticular layer. Contains thick bundles of collagen fibers compared to those in the papillary layer. Larger blood vessels.
Rete ridges/ Rete pegs
Found between the epidermis and the papillary layer (superior) of the dermis. Increase surface area and add friction so the two layers cannot be sheared apart.
Scar. Why is skin not as strong as it used to be
Loses Rete ridges/ rete pegs. Doesn’t require as much shearing force to remove epidermis from dermis.
Pacinian corpuscle
Mechanoreceptor for vibration and pressure. Found in thick skin located deep in the dermis (reticular dermis)
Free nerve endings from afferent axon sense what
Detects pain and temperature. Found in the epidermis. Unmeyelinted.
Ruffni corpuscles sense what
Tensional forces. Shearing force. Found throughout the dermis. Hard to see histologically. Blend in with other tissues.
Bulbs of Krause are a sensory receptor for what
Cold responsive receptors? unsure of role. In bulb shape capsule. Found in the dermis. Transparent and rare to see/pick out.
Where are Meissners corpuscle located
A type of mechanoreceptor that detects light touch. Found in thick skin. Located in the papillary (superior) layer of the dermis, found in the dermal papillae. Dermal papillae are areas in the retentions pegs where dermal tissue travels up into epidermal tissue.
3 ways to differentiate thin skin from thick skin
- Thin skin does not have lucidium layer, thick skin does.
- Thin skin has hair follicles, thick skin does not.
- Thin skin does not have pacinian corpuscles or meissners corpuscles. Thick skin does.
Primary afferent nerve ending axons relationship to size
Small size= are nerve endings. Temperature, pain and itch.
Middle size= Mechanoreceptors of skin, pain and temp.
Large size= Proprioceptors of skeletal muscles.
Pathway for pain reception
Afferent neuron enters dorsal root ganglion and immediately synapses with secondary neuron, crosses contralaterally, and travels up the spinal cord. Synapses at thalamus and then travels to the somatosensory cortex (Brodmanns 1,2,3)
Spinothalmic pathway
Pathway for sensation
Afferent nuron enters dorsal root ganglion, then stays episilateral as it passes up the spinal cord and to the medulla. Then it synapses, and crosses contra laterally in the brain stem to the thalamus. Synapses. Then goes to primary somatosensory cortex (Brodmanns 1,2,3).
Medial lenniscal pathway
Carcinoma
Cancer of epithelial cell origin
Basal cell carcinoma
In the stratum basale layer of the epithelium. High mitotic activity and cells move into lower tissues. Generally caused by UV exposure (lower eyelid, nose, forehead, cheeks).
Typically ulcerate, and will bleed a lot. Scab. Treated by excision.
Which is more likely to metastasize? Squamous cell carcinoma or basal cell carcinoma?
Squamous cell carcinoma. Cells of the squamous layer undergo more significant changes than basal cells do.
Squamous cell carcinoma
Carcinoma of the stratum spinosum.
More invasive because this layer is not protected by the melanocytes like basale cells are. More aggressive and likely to metastasize.
Treatment requires chemotherapy. Undergo more significant changes.
Melanomas originate where
Melanocytes, which are found in the epidermis basale and spinosum layers. Very metastatic. Likely to metastasize to 1) liver, and 2) lungs.
5 signs to look for to determine difference between normal mole and melanoma
- Asymmetry. Half the mole does not match the other half.
- Border. Edges are irregular= “Serpentine”
- Color. Color of the mole varies throughout.
- Diameter. If it is larger than a pencil eraser.
- Vascularization.
