Session 5.1a - Pre-Reading - Skin Functions Flashcards
https://www.youtube.com/watch?v=sEqSFWjj2_Q Function of the Skin
What is the largest organ of the body?
Skin
Skin is the largest organ of the body by what ___
Mass and size
What type of organ is the skin?
A multifunctional organ
What is a multifunctional organ?
A set of tissues that work together to carry out a certain set of functions
Name the functions of the skin.
7 functions
1) Protection
2) Sensation
3) Thermal Regulation and Insulation
4) Excretion and Secretion
5) Immunity
6) Endocrine
7) Growth
What is the outermost portion of the skin called?
Epidermis
What is found in our epidermis?
Four specialised cells
What are the 4 specialised cells of the epidermis?
- Keratinocytes
- Melanocytes
- Langerhans cells
- Merkel cells
What is the middle section of our skin called?
Dermis
What does our dermis contain?
- Blood vessels (arteries and veins)
- Excretory glands e.g. sebaceous (oil) gland, sweat gland
Where are the arteries of our skin located?
The dermis
Where are the veins of our skin located?
The dermis
Where are our excretory glands located?
Dermis
Where do we find keratinocytes?
Epidermis
Where do we find melanocytes?
Epidermis
Where do we find Langerhans cells?
Epidermis
Where do we find Merkel cells?
Epidermis
Give 2 examples of excretory glands found in the dermis.
Sebaceous (oil) gland
Sweat gland
What does sebaceous mean?
Relating to oil or fat
- Relating to a sebaceous gland or its secretion
What does a sebaceous gland do?
Exocrine glands which secrete oily or waxy matter.
What is the lowest portion of the skin?
Hypodermis
Name the layers of the skin.
Epidermis
Dermis
Hypodermis/subcutaneous layer
(from superficial to deep)
Label these in order of superficial to deep.
Dermis, Epidermis, Hypodermis
Epidermis
Dermis
Hypodermis/subcutaneous layer
(from superficial to deep)
What is the hypodermis also known as?
The subcutaneous layer
Which layer does the subcutaneous layer of the skin correspond to?
The hypodermis
What does the hypodermis/subcutaneous layer contain?
Adipose cells
Macrophages
Where are adipose cells found?
Hypodermis/subcutaneous layer
Where are macrophage cells found?
Hypodermis/subcutaneous layer
What is the function of adipose cells?
To insulate our body
Which cells function to insulate our body?
Adipose cells
What is the function of macrophages?
To engulf bacterial cells
Which cells engulf bacterial cells?
Macrophages
What is arguably the most obvious function of the skin?
Protection
How does the skin provide protection?
Skin creates a physical barrier that protects us from a wide range of harmful things
What do keratinocytes do?
Secrete a protein fibre called keratin
Where is keratin secreted from?
Keratinocytes in the epidermis
What sort of molecule is keratin?
A protein fibre
What is the function of keratin?
- Gives skin strength
- Protects skin from water (makes skin impermeable to water)
How does keratin protect skin from water?
It makes it impermeable to water.
What fibres are found in the dermis?
A network of collagen and elastin fibres (also in the hypodermis)
Where are collagen fibres found?
In the dermis and hypodermis
Where are elastin fibres found?
In the dermis and hypodermis
What fibres are found in the hypodermis?
A network of collagen and elastin fibres (also in the dermis)
What do keratin, collagen and elastin work together to do?
Give the skin strength and elasticity
What gives the skin strength and elasticity?
Keratin, collagen and elastin
What does having strength and elasticity allow the skin to do?
Resist physical and mechanical pressures and forces.
How does the skin resist physical and mechanical pressures and forces.
Strong and elastic protein fibres such as keratin, collagen and elastin, found in the dermis/hypodermis of the skin, gives the skin strength and elasticity. This is able to resist physical/mechanical pressures/forces.
What types of fibres are keratin, collagen and elastin?
Strong and elastic protein fibres
Name 3 strong and elastic protein fibres.
Collagen
Keratin
Elastin
What is the relationship of the skin to our internal organs?
Ensures they are well protected and not damaged
How does the skin protect the heart (for example)?
The heart is not only protected by the sternum bone and the rib cage, it is also actually protected by the layer of skin that exists on top of our sternum and ribcage
Name 5 things the skin protects us from.
- Physical damage
- Excessive UV radiation
- Bacterial and viral microorganisms
- Dehydration
- Dangerous chemicals
Why do we need the skin protect us from UV radiation?
Excessive UV radiation is dangerous
Do we need UV radiation?
Excessive UV radiation is dangerous but our skin actually needs UV radiation to ultimately synthesise vitamin D
What does our skin use UV radiation for?
Synthesising vitamin D
How is vitamin D synthesised?
In the skin via UV radiation
What is vitamin D?
A hormone that is used to basically regulate calcium and phosphate ions in our blood
Which hormone used to regulate calcium and phosphate ions in our blood is synthesised from UV radiation?
Vitamin D
What is UV radiation?
UV radiation is a type of electromagnetic wave and it carries more energy than normal visible light waves, and that’s because it has a slightly higher frequency
Why is excessive UV radiation dangerous?
When UV rays (high-energy rays) hit the cells of our skin they can end up damaging the organelles and the biological molecules, such as DNA found inside our skin cells
What biological molecules can UV radiation damage?
Organelles and DNA found inside skin cells.
What can excessive UV radiation ultimately lead to?
Cancer
How can excessive UV radiation ultimately lead to cancer?
UV rays are high-energy, so when these rays hit the cells of our skin, our DNA and organelles of the skin are susceptible to damage. Damage to the DNA can ultimately lead to cancer.
What natural defence do we have against UV radiation?
Melanocytes (specialised cells found in the epidermis), which release melanin
Which layer of skin protects us from UV radiation?
Epidermis - melanocytes found there.
What do melanocytes do?
Release a chemical/pigment known as melanin
What type of molecule is melanin?
A chemical/pigment
What is the function of melanin?
- Gives us our skin colour
- Absorbs UV radiation which protects us from damaging our skin
What gives us our skin colour?
Melanin released from melanocytes in the epidermis of our skin.
What absorbs UV radiation protecting us from skin damage?
Melanin released from melanocytes in the epidermis of our skin.
How does the skin prevent bacterial cells and viral agents getting into our body?
By creating a physical barrier
What is the skin a physical barrier against?
Bacterial cells and viral agents
Other than bacteria and viral miroorganisms, what else does the skin protect us from?
A wide variety of different types of harmful chemical agents
How does the skin protect us from dangerous molecules?
If some type of harmful molecule gets onto our skin, there is a very high probability that the skin will not allow that harmful chemical to actually go through the skin and into our organs found inside our body.
Explain how the different layers of the skin aid in protection.
Epidermis - keratinocytes secretes keratin which makes the skin strong and impermeable to water
- melanocytes release melanin which protects us from UV radiation
Dermis - network of collagen and elastin which (together with keratin) gives skin strength and elasticity, allows the skin to resist physical/mechanical pressures/forces
Hypodermis - collagen and elastin also found here.
How is the epidermis involved in protecting the skin?
- keratinocytes secretes keratin which makes the skin strong and impermeable to water
- melanocytes release melanin which protects us from UV radiation
How is the dermis involved in protecting the skin?
Network of collagen and elastin which (together with keratin from the epidermis) gives skin strength and elasticity, allows the skin to resist physical/mechanical pressures/forces. This also occurs in the hypodermis.
How is the hypoepidermis involved in protecting the skin?
Network of collagen and elastin which (together with keratin from the epidermis) gives skin strength and elasticity, allows the skin to resist physical/mechanical pressures/forces. This also occurs in the dermis.
How does our skin aid in sensation?
- On/in our skin we have a wide variety of different types of sensory/somatic sensory receptors.
- We also have Merkel cells. mechanoreceptors in our epidermis, which are believed to be involved in sensation
What receptors aid in sensation?
Somatic sensory receptors
Where are our somatic sensory receptors found?
On our skin
Give examples of somatic sensory receptors.
- Pressure
- Light
- Thermal (including heat and cold)
- Pain
- Many other
Receptors
Give two types of thermal receptors.
- Heat receptors
- Cold receptors
What allows us to feel it when we pinch our skin?
- Somatic sensory receptors in that skin that is connected to our nervous system and that allows me to basically sense that pinch/touch
- Merkel cells
What do somatic sensory receptors do?
Allow us to feel sensation in our skin.
What are Merkel cells?
Specialised cells (oval-shaped mechanoreceptors) found in the epidermis that are (believed to be) involved in sensation.
What are the specialised cells found in the epidermis that are (believed to be) involved in sensation?
Merkel cells
How is our skin involved in insulation?
Adipose cells in our hypodermis/subcutaneous layer create a layer of insulation
Which layer of the skin is involved in insulation?
Our hypodermis/subcutaneous layer, as this contains adipose cells.
Our skin aids us in insulation. What does this do?
Keeps us cool in the summer days and keeps us warm in the winter nights
What keeps us cool in the summer days and keeps us warm in the winter nights?
Adipose cells in our hypodermis/SC tissue (insulation).
What is our body in a constant state of?
Homeostasis
What is one of the functions involved in maintaining homeostasis?
Maintaining a constant core temperature
What is the core temperature of the body?
36.7 degrees Celsius
What happens if our core temperature increases or decreases even slightly?
Our proteins basically lose their efficiency and cannot function properly
How does the skin maintain thermal regulation?
Via the process of
- sweating/perspiration
- evaporation
- radiation
Sweating, perspiration, evaporation and radiation are processes which do what in the body?
Processes that our skin does to maintain thermal regulation.
What does every exothermic process that occurs in the body do?
Produces excessive amounts of energy/heat.
What produces excessive amounts of energy/heat in the body?
Exothermic processes
Give an example of an exothermic process.
Cellular respiration
What happens if heat from exothermic processes is not expelled by the body?
It will increase the core temperature
How can the core temperature be increased by natural processes?
If heat from exothermic reactions is not expelled by the body.
Where is the heat from exothermic processes ‘stored’?
In the blood
How is blood involved in cooling the core temperature down?
It takes the heat and it stores that heat in our blood, and as the blood actually travels in these blood vessels in the dermis section of our skin this blood radiates the heat outward to the outside of our skin
How is the dermis involved in cooling the core temperature down?
The blood vessels are contained in the dermis, which are involved in radiating the heat out of our body
What process does blood lose heat by?
Radiation
Where does blood radiate heat to?
Outward to outside of our body/skin.
What do sweat glands do?
Produce sweat
Where does sweat come from?
Sweat glands
What does sweat contain?
Predominantly water
How does sweat cool our skin?
Sweat consists predominantly of water - and as the water gets onto the surface of our skin, the heat that basically rises and radiates from the moving blood in our blood vessels is used to actually vaporise that water from our skin
What vaporises sweat?
The heat in our blood vessels
As well as radiate heat out, what does blood do to cool the body down?
Vaporise the water from our skin
What type of process is water vaporisation?
An endothermic process
Why is water vaporisation highly endothermic?
Because water has a very high specific heat capacity (needs a lot of energy before it gets hot)
How are endothermic processes involved in regulating the core temperature and homeostasis of the body?
Sweat (which is predominantly filled with water) gets to the surface of our skin, and is vaporised from the heat in blood vessels that is radiating out. Water vaporisation is a highly endothermic process due to its high specific heat capacity, thus this is an important process in controlling homeostasis.
What do we need to do in the body after exothermic processes have finished?
Every exothermic process in the body produces excessive energy that must be dissipated by the body to prevent overheating
How does heat from exothermic processes rise to the top portion of our skin?
Blood vessels in the dermis store some of that excess heat and expel it out of the body and skin via radiation, so the heat simply rises to the top portion of our skin.
Why does heat rising to the top portion of our skin cool our core temperature down?
Blood vessels in the dermis store some of that excess heat and expel it out of the body and skin via radiation, so the heat simply rises to the top portion of our skin and is expelled by radiation.
What is the endothermic process involved in cooling our body down?
Evaporation of water (sweat) which gets rid of excess heat
What is the endothermic process involved in cooling the body down?
The skin can also expel heat via the endothermic process of evaporation, so sweating takes place and that rising heat basically vaporises
Which two energy processes are involved in cooling the skin down?
- Radiation
- Evaporation (endothermic process)
How does the skin conserve heat if it’s cold outside?
Constricts our blood vessels found in the dermis and that redirects, that shunts, the blood away from the skin and that conserves energy because there is very little blood that actually radiates the energy out from our skin
What process does the skin act to minimise to prevent heat loss when it’s cold?
Radiation - constricts blood vessels so less heat is lost by radiation.
How is the dermis involved in thermal regulation?
The dermis contains the blood vessels.
When the body is too hot, blood stores the heat and it is lost via radiation to the outside of the body.
When the body is too cold, our blood vessels constict, which redirects the blood away from the skin, conserving energy and minimising loss of heat via radiation.
What can excrete things in our body?
Kidneys
- waste products
- ions
- water
Skin
- molecules
- ions
What do the kidneys excrete?
- Waste products
- Ions
- Water
What does the skin excrete?
- molecules
- ions
As well as skin, what can excrete waste products?
Kidneys
As well as the kidneys, what can excrete waste products?
Skin
What does sweat contain?
- Water (predominantly)
- Waste products, e.g. urea
- Ions, e.g. sodium
Give an example of what waste products sweat contains.
Urea
Give an example of what ions sweat contains.
Sodium
What do sweat glands produce?
Sweat
What do sweat glands do with sweat?
They secrete and excrete it onto the surface of the skin
How is sweat secreted?
Via sweat glands onto sweat pores
What is sweat secreted through in the skin?
Sweat pores
How is sweat vaporised?
Sweat glands produce sweat and secrete and excrete this substance onto the surface of the skin via sweat pores. The heat that rises from the blood vessels moving that blood along the dermis is used to actually vaporise that water from the surface of our skin.
What does blood do to sweat?
Heat from the blood vessels vaporises sweat.
Other than sweating, how else can water be lost on our skin?
Via transepidermal water loss.
What is transepidermal water loss?
So actually, water can actually diffuse across the upper portion of our skin (transepidermal), so basically, water is lost as a result of this process of diffusion that takes place through the skin, and this is different than sweating.
What is the main process involved in transepidermal water loss?
Diffusion
Where do transepidermal water loss occur?
Water diffuses across the upper portion of our skin (hence, transepidermal)
What is the process of excreting water to the skin’s surface by DIFFUSION called?
Transepidermal water loss
- This is different to sweating!
Key word: diffusion
How is the skin involved in excretion and secretion?
- Excretion of water, waste products (e.g. urea) and salts, (e.g. sodium) via SWEATING and TRANSEPIDERMAL WATER LOSS (TEWL)
- Secretion of sweat onto skin surface via sweat pores
What are two types of immune cells found in the skin?
- Langerhans cells (epidermis)
- Macrophages (hypodermis)
What do Langerhans cells do?
Responsible for interacting with T cells of our immune system and that basically helps us protect from bacterial agents.
What cells in our skin interact with T cells of our immune system?
Langerhans cells
What is the function of Langerhans cells?
Responsible for interacting with T cells of our immune system and that basically helps us protect from bacterial agents.
How do Langerhans cells protect us from bacterial agents?
Responsible for interacting with T cells of our immune system and that basically helps us protect from bacterial agents.
Which cells produced in the skin protect us from bacterial agents?
Langerhans cells
What do Langerhans cells interact with?
T cells (immune system)
Which immune cell is found in the epidermis?
Langerhans cells
Which immune cell is found in the hypodermis?
Macrophages
How is the skin involved in immunity?
- Langerhans cells (epidermis): interacts with T cells of our immune system which helps us protect from bacterial agents
- Macrophages (hypodermis): engulfs bacterial cells
How does our skin use UV radiation?
Skin actually needs UV radiation – so certain cells are responsible for using UV radiation: the energy stored in UV radiation
Which cells require UV radiation?
Certain cells in the epidermis of the skin (melanocytes)
What does the skin make from UV radiation (inactive form)?
Cholecalciferol (inactive form of Vitamin D3)
What is cholecalciferol?
Inactive form of Vitamin D3
What is the inactive form of Vitamin D3 called?
Cholecalciferol
What happens to cholecalciferol once it is produced by the skin?
It travels into our liver.
What happens to cholecalciferol in our liver?
It is transformed into calcidiol
Where is calcidiol found?
It is produced in the liver and then travels to the kidneys.
What metabolite of the vitamin D pathway is found in the liver?
Calcidiol
What happens to calcidiol after it is produced?
It travels to the kidney
What happens to calcidiol in the kidney?
Calcidiol is transformed into calcitriol - the active form of Vitamin D (D3?)
What metabolite of the vitamin D pathway is found in the kidney?
Calcitriol (vitamin D)
What is calcitriol?
The active form of vitamin D
What is the active form of vitamin D3 known as?
Calcitriol
Explains what these compounds are:
Cholecalciferol
Calcidiol
Calcitriol
Cholecalciferol - inactive metabolite of Vitamin D3
Calcidiol - inactive precursor of Vitamin D3
Calcitriol - active form of Vitamin D3
Explains what these compounds are produced and synthesised:
Cholecalciferol
Calcidiol
Calcitriol
Cholecalciferol - skin
Calcidiol - liver
Calcitriol - kidneys
Explain how the skin uses UV radiation to make Vitamin D.
- energy stored in UV radiation produces CHOLECALCIFEROL (inactive form of Vitamin D3) in the SKIN
- cholecalciferol travels into LIVER, transforming to CALCIDIOL (inactive precursor of vitamin D3)
- calcidiol travels into our KIDNEYS, where it is transformed into CALCITRIOL (active form of Vitamin D)
Where is cholecalciferol found?
(Inactive form of Vitamin D3)
Produced in the skin and travels to the liver.
What is calcidiol?
Inactive precursor of Vitamin D3
Where is calcitriol found?
It is produced in the kidneys (from calcidiol)
Active form of Vitamin D3
What is the function of calcitriol?
To basically regulate the amount of calcium and phosphate ions found inside our skin/blood
What is the function of Vitamin D?
To basically regulate the amount of calcium and phosphate ions found inside our skin/blood
Which compound regulates the amount of calcium and phosphate ions found inside our skin/blood?
Vitamin D (calcitriol)
Why is the skin an endocrine organ?
It produces this pre-hormone known as our cholecalciferol (inactive form of Vitamin D3)
As the human grows, the bone grows, and the organs grow. What does this mean for the skin?
So we know, as the human grows, as the bone grows, and the organ grows, the skin must grow along with everything else inside the human body.
What function does the skin need in order to grow?
It must be able to expand.
What allows the skin the ability to expand?
Elastin
What is elastin?
Protein fibres ofund in the skin
What does elastin do?
Gives skin flexibility, which allows it to:
- Help skin to protect from physical and mechanical stress
- Allows the skin to grow
Fig. 1
Label this image
- epidermis
- dermis
- hypodermis
- sweat pore
- sweat gland duct
- sweat gland
- sebaceous (oil) gland
- arrector pilli muscle
- vein
- artery
- hair follicle
- adipose cells
Draw the layers of the skin and what you might find in each layer.
See Fig. 1
- epidermis
- dermis
- hypodermis
- sweat pore
- sweat gland duct
- sweat gland
- sebaceous (oil) gland
- arrector pilli muscle
- vein
- artery
- hair follicle
- adipose cells
Describe the skin’s function.
The skin, which is the largest organ of the body both by mass and by size, is a multi-functional organ that serves several important purposes.
Explain how the skin is involved in protection.
- Perhaps the most evident function of the skin is that in protection.
- The skin consists of strong and elastic protein fibres (collagen, keratin and elastin) that protect the body from physical and mechanical forces. This ensures that the internal organs are not damaged.
- Aside from protecting from physical damage, the skin also protects from (1) excessive UV radiation (2) bacterial and viral micro-organisms (3) dehydration (4) dangerous chemicals.
Explain how the skin is involved in sensation.
- The skin contains somatic sensory receptors that aid in sensation. It also contains cells called MERKEL cells that are believed to be involved in sensation. The skin contains pressure receptors, light receptors, pain receptors, thermal receptors, among others.
Explain how the skin is involved in thermal regulation and insulation.
- Every exothermic process in the body produces excessive energy (heat) that must be dissipated by the body to prevent overheating. The blood vessels that run in the dermis of the skin can expel this heat via RADIATION. The skin can also expel heat via the endothermic process of evaporation. The skin can also prevent heat loss by redirecting the blood away from the skin.
Explain how the skin is involved in excretion and secretion.
- The skin is an excretion organ. It can excrete water to the skin’s surface via diffusion. Waste products such as urea, salts such as sodium & water can also be excreted via sweating.
Explain how the skin is involved in immunity.
- Langerhans cells of the epidermis can interact with T-cells to help protect the body from bacterial agents. Phagocytic cells in the hypodermis can engulf bacterial cells.
Explain how the skin is involved in endocrine function.
- Cells in the epidermis can produce vitamin D3 (cholecalciferol) by using the energy stored in UV radiation. This can be ultimately activated to the hormone calcitriol in the kidneys.
Explain how the skin is involved in growth.
- The skin can expand due to the elastin fibres. Therefore, as the organism grows, so does the skin.
