Integumentary System Flashcards
What are the functions of the integumentary system?
- Protect against physical, chemical & biological insults (e.g. bacteria/virus)
- Water proof barrier (both ways - in & out)
- Absorb UV radiation (lessen impact)
- Excretion & thermoregulation
- Sense the external environment (external stimulus)
- Synthesis of vitamin (esp. Vit D) & pigments (e.g. melanin)
What % of adult body weight is skin?
15%
Largest organ in body
What is skin?
Cutaneous membrane the forms the external body surface
What are the two main layers of skin?
- Epidermis
- Dermis
What is Epidermis?
Ectodermally derived epithelial tissue
Outer layer
What is Dermis?
Mesodermally derived connective tissue
Inner layer
What is the basement membrane?
AKA Epidermo-dermal junction
Separates epidermis from dermis
What is the hypodermis?
Subcutaneous layer of fascia (superficial fascia - loose connective tissue) & fat
Below the Dermis
What are some accessories found in skin?
In the Epidermis: Glands, Hair, Nails
In the Dermis: Smooth muscle, Bld. vessels, lymphatics, sensory organs
What accessories are found in the epidermis?
Glands
Hair
Nails
What accessories are found mainly in the dermis and some in the hypodermis?
Blood vessels
Smooth muscle
Lymphatics
Sensory organs
What are the two types of skin?
Hairy skin (aka ‘thin’ skin)
Glabrous skin (aka ‘thick’ skin)
What is present in hairy skin?
Hair & certain types of glands
(‘thin’ skin)
What is NOT present in hairy skin?
Encapsulated sense organs in the dermis X present
(‘thin’ skin)
BUT have free nerve endings
Where is hairy skin usually found?
Most regions of the body EXCEPT palms & soles
(‘thin’ skin)
Is the epidermis in the hairy skin or in the glabrous skin thinner?
Epidermis in hairy skin is thinner
Where is glabrous skin usually found?
Confined to palms & soles; fingertips & toes
(‘thick’ skin)
What is present in glabrous skin?
Encapsulated sense organs in the dermis are present (more sensitive)
(‘thick’ skin)
What is not present in the glabrous skin?
Lack of hair & certain types of glands
(‘thick’ skin)
What characteristic does glabrous skin have?
Furrows & ridges
Caused by the basement membrane - very wavy & causes the indentions that make up our fingerprints (e.g.)
= Dermatoglyphics (study of ridges on our skin - e.g. fingerprints for forensic science)
Are there blood vessels in the epidermis?
No bld vessels but have nerve endings
O2 & nutrients diffuses from bld vessels in the dermis through the basement mbn (vv thin)
Is hair derived from the epidermis, the dermis or the hypodermis?
Derived from the epidermis (even though it dips into the dermis & hypodermis)
What is the stratum basale?
Single layer of cuboidal/columnar epithelium
Cells attached to (sitting on) the basement mbn
What are the cells that make up the stratum basale?
Keratinocytes
Stem cells
Melanocytes
Merkel cells
What is the stratum spinosum?
Thickest layer of the epidermis
Several layers of spiny keratinocytes
In each layer, cells attached to each other by desmosomes (cellular ‘cement’)
What are the individual layers of the epidermis? (5 layers)
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- [Stratum lucidum - only in ‘thick’ skin]
- Stratum corneum
What do the keratinocytes in the stratum spinosum produce?
Keratin
Keratin filaments are called tonofilaments = very tightly bound tgt (bundles of filaments)
What is the stratum granulosum?
A few layers of keratinocytes containing granulosomes
Basically keratin becomes dominant component & cells start to lose organelles)
Lamellar Granules: contain lipid-like substances
Cells start to die
What happens when the cells start to die in the stratum granulosum? (with regards to the lamellar granules)
Lamellar granules secrete the lipid-like substances within = these substances are deposited = act like the waterproof barrier (prevents H2O from evaporating from deeper layers & H2O enter)
What is the stratum corneum?
Thick layers of dead keratinocytes
Cross-linked keratins dominate these layers
What is the stratum luciderm?
It is only found in ‘thick’ skin!
Located between the stratum granulosum & stratum corneum
A few layers of keratinocytes that appear ‘clear’ (therefore named luciderm)
This clear appearance is due to the protein eleidin
What is hair made of?
Dead epidermal cells that have been converted to keratin
How does hair growth occur?
When cells in the hair matrix (base of bulb) divide & push upwards
When the cells reach the surface (shaft), they have been completely converted to keratin
What are always seen with hair?
Sebaceous gland
Smooth muscle (sebaceous gland sits on the smooth muscle - arrector pili muscle)
How is acne caused?
Sex hormones (esp androgen) stimulates the sebaceous gland
Overstimulation (hyperstimulation) can lead to blockage of outlet in hair follicle
What are nails made of?
Dead epidermal cells that have been converted into keratin
Derived from the epidermis
Where are sweat glands derived from?
DERIVED from the epidermis
LOCATED in the dermis
Where are sweat glands located?
Throughout the body
In the dermis
What are the functions of sweat glands?
Secrete sweat (water, salts, urea)
Thermoregulation (dissipate heat)
Excretion of wastes & toxins
Which sweat glands are the majority?
Eccrine sweat glands
Eccrine sweat glands are innervated by ________
Cholinergic innervation (by acetylcholine)
Where do eccrine sweat gland ducts open into?
Opens into the skin surface
Ducts have their own openings
What are the types of sweat glands?
Eccrine sweat glands
Apocrine sweat glands
Where are apocrine sweat glands found?
Axilla (armpiti), areola (ard the nipple) & genital areas
(ear area also?)
Apocrine glands are innervated by ___________
Adrenergic innervation (adrenaline neurotransmitter)
Where do the apocrine sweat gland ducts open up into?
Opens into hair follicles
What is the mechanism of apocrine secretion like?
During secretion, a portion of the cell is pinched off and secreted
So basically the sweat will contain vesicles from the secretory cells
What are the differences between eccrine & apocrine sweat glands?
- Eccrine found throughout the body but apocrine found at axilla, areola, genital areas
- Eccrine has cholinergic innervation while apocrine has adrenergic innervation
- Eccrine ducts open into skin surface while apocrine ducts open into hair follicles
- Secretory product from apocrine contains vesicles from the secretory cells while secretory product from eccrine does not
Which is considered thin sweat and thick sweat?
Thin sweat - eccrine gland
thick sweat - apocrine gland
Where are melanocytes located?
Basal layer (stratum basale)
2-3% are melanocytes
What is the ratio of melanocytes to keratinocytes like?
1 melanocyte : 4 keratinocyte
to
1 melanocyte : 15 keratinocytee
What is the function of melanocytes
Production of melanin pigment
What are the types of melanin?
Pheomelanin - red/yellow
Eumelanin - brownish-black (better at protecting skin against UVB)
Neuromelanin (prod. in brain)
What does melanin do?
Protects against UV radiation
UVA - carcinogen
UVB - shorter wavelength than UVA; stimulates prod. of melanin
UVC - blocked by ozone layer
Melanin produced is donated to ____________
Melanin produced is donated to keratinocytes as melanosomes (prod. by melanocytes
Melanin + keratinocytes = form a unit
Do albino people have less melanocytes?
Number of melanocytes are the same in everyone
Colour of skin differs based on degree of activity of melanocytes
Where are Langerhans cells found?
Epidermal layers
Most likely found in stratum spinosum BUT migratory in nature
2-4% of epidermis
What is the function of Langerhans cells?
Immunity; antigen presentation
Antigen stimulus (Sense foreign pathogens) = process these pathogens = migrate to lymph node = develop an immune response
No. of langerhans cells inc in skin inflammation
Where are Merkel cells found?
Basal layer (stratum basale)
Hair follicle
What is the function of Merkel cells?
Sensory to touch
Detect deformations of skin & movement of hair
Why are Merkel cells able to detect touch stimuli?
Basal surface contacts an axonal terminal (has nerve endings)
May have neuroendocrine function
What are other sources of skin colour?
Beta-Carotene (source for Vit A)
Jaundice (Bilirubin stains the dermal fibres & conjunctiva)
Hemoglobin (e.g. lack of O2)
What are the layers of the dermis?
Papillary layer
Reticular layer
What is the papillary layer?
Loose connective tissue (areolar tissue) - elastic & collagen fibres
Forms ‘peg’ like projections into epidermis
Helps transfer nutrients to epidermis (diffusion)
What does the papillary layer contain?
Sensory receptors for FINE touch
What is the reticular layer?
Dense connective tissue (collagen)
What does the reticular layer contain?
Sensory receptors for deep pressure & vibration
The reticular layer is the location for:
- Hair follicles
- Sweat glands
- Sebaceous glands
- Blood vessels
Where is the hypodermis located?
Below the dermis
What is the main components of the hypodermis?
Loose connective tissue
Fat
What is the function of the hypodermis?
Act as padding - allows sliding of skin on deeper structures (reduce friction = smooth movement)
Thermal insulation
(Fatty parts) Rich in blood vessels = absorptive function (injections into subcut for fast absorption)
Where is the Meissner’s corpuscle found?
ONLY in papillary layer of dermis in fingertips
Meissner’s corpuscle
Fast-adapting receptors
sense FINE discriminatory touch
Are the merkel cells found in the dermis or epidermis?
Epidermims
but also in the dermis
Merkel cells builds upon what is felt by the Meissner’s corpuscle
What do Ruffini endings sense?
Tensile pulling of skin, torque, mechanical force on skin
What are the sensory structures found in the skin? (6 structures)
- Merkel cells
- Meissner’s corpuscle
- Ruffini ending
- Pacinian corpuscle
- Krause end bulb
- Nerve
Where is the Pacinian corpuscle found?
Reticular dermis
Look like onion skin
Fast-adapting receptors
sense deep transient pressure & vibration
Which sensory structures have fast-adapting receptors?
Meissner’s corpuscle
Pacinian corpuscle
What are dermatomes?
Skin is divided into segments
Each segment stimulates certain corresponding part of the spinal cord –> certain part of cerebral cortex senses it
E.g. if I touch the shoulder, C4 vertebrae stimulated –> cerebral cortex senses it
Why is there referred pain?
Spinal cord has to process both external (e.g. touch) & internal stimuli (from internal organs)
Some neurons that sense inner internal organ sensations also sense external sensations = get confused = “think this part pain is from skin (external) but actually from internal organ (internal)
Where is the referred pain of angina pectoris?
(pain due to lack of blood supply to mediastinum)
- Left upper limb all the way to the little finger
- Anterior chest
- Neck & Jaw
What are the steps in wound healing?
- Bleeding (1 minute)
- Inflammatory (~5 days)
- Proliferative (3 weeks)
- Remodeling (1 year)
What happens during injury inflammation?
- Tissue injury = release chemical signals (histamine)
- Dilation & increased leakiness of capillary = phagocytes migrate to area (inflammation)
- Phagocytes consume bacteria & cell debris = platelets move out of capillary to seal wounded area
In the inflammatory phase, what cells are present?
Neutrophil
Platelets
In the Proliferative phase, what cells are present?
Macrophages
Neutrophils
Platelets
Fibroblast
Main cell present in
1. Hemostasis (bleeding)
2. Inflammation
3. Proliferation
4. Remodeling
- Platelets
- Granulocytes
- Monocyte/macrophages
- Fibroblast
What happens in wound healing and scarring?
- Clotting occurs (due to clotting proteins & plasma proteins) & scab forms
- Inflammatory chemicals released from injury
- White blood cell seep into injured area
- Epithelial cells multiply & fill in over the granulation tissue
- Granulation tissue restores the vascular supply
- Restored epithelium thickens; area matures & contracts
Scar tissue due to excessive collagen deposit
Skin burns affect which skin layer:
1st degree
2nd degree
3rd degree
1st degree: Dermis
2nd degree: Dermis + Epidermis
3rd degree: Dermis + Epidermis + Hypodermis + muscle + bone
What changes are seen in the skin as we age?
Epidermis & dermis become smaller as we age
Decrease in collagen
Decrease in elastic fibres
What are skin tension lines?
Reflect internal tension within skin caused by collagen fibres in the connective tissue of the dermis (pattern of collagen fibres arrangement)
Alive vs after rigour mortis (Langer’s cleavage lines) are different
