Integumentary System

What can the integumentary system be referred to as?

The integumentary system can be referred to as your built in outfit that you can never take off

What is the integumentary system made up of?

The integumentary system is made up of skin, hair, nails, sebaceous tissues, sweat glands, and sensory receptors

What do all of the structures of the integumentary system do?

Together, all of the structures of the integumentary system help to protect the body, they help regulate temperature, and they allow you to interact with the outside world

How many layers does the integument have?

The integument is comprised of 3 main layers:

1. Epidermis

2. Dermis

3. Subcutaneous tissues

What is the epidermis?

The epidermis is the top layer that is thin, made up of epithelial tissue, and is avascular

What is the dermis?

The dermis is just underneath the epidermis, it is thicker, it is made up of connective tissue, and it is vascular

What is the subcutaneous tissue?

The subcutaneous tissue is just below the dermis, it is technically not part of the skin, but together with the skin, it forms the integument

What is the integumentary system in terms of defence?

The integumentary system is your first line of defence against physical injuries, invading microbes, UV radiation, and environmental pollutants

What is the integumentary system also important for in terms of detection?

The integumentary system is also important in signalling if there are underlying problems within the body by changing the colour or texture of the skin

What is the largest organ in the body?

The skin is the largest organ in the body

How much area does the skin cover?

The skin can cover about 2 square meters which is about the size of a small blanket

How much does the skin weigh?

The skin weighs about 4.5-5kg

What are the accessory structures of the integumentary system?

The accessory structures of the integumentary system are the hair, the nails, and the skin glands (sweat and oil glands)

What do all accessory structures develop from?

All accessory structures are going to develop from the ectoderm of the embryonic epidermis

What does the hair do?

The hair helps with protection, temperature regulation, and it is one of the aspects of sensory input

How many major types of glands are there?

There are 2 major types of glands:

1. Sweat glands

2. Sebaceous glands (oil glands)

What do the sweat glands do?

The sweat glands help regulate the body temperature

What do the sebaceous/oil glands do?

The sebaceous/oil glands help keep the hair and skin from drying out

What do the nails do?

The nails protect the tips of the fingers and toes and they help with fine motor tasks

How many major functions are there for the integumentary system?

There are 6 major functions of the integumentary system:

1. Temperature regulation

2. Blood reservoir

3. Protection

4. Cutaneous sensations

5. Excretion and absorption

6. The synthesis of vitamin D

How does the integumentary system function in terms of temperature regulation?

The integumentary system functions in terms of temperature regulation because the skin is the body’s thermostat

How does the integumentary system function in terms of blood reservoir?

The integumentary system functions in terms of blood reservoir because the skin holds a significant amount of blood supply

How does the integumentary system function in terms of protection?

The integumentary system functions in terms of protection because the skin protects from physical damage, it protects from bacteria and pathogens, it protects from UV radiation, and it helps prevent dehydration

How does the integumentary system function in terms of cutaneous sensations?

The integumentary system functions in terms of cutaneous sensations because the skin is packed with sensory receptors that can detect touch, pressure, pain, and temperature

How does the integumentary system function in terms of excretion and absorption?

The integumentary system functions in terms of excretion and absorption because the skin helps excretes small amounts of wastes through sweat, and it also absorbs certain substances such as medications

How does the integumentary system function in terms of the synthesis of vitamin D?

The integumentary system functions in terms of the synthesis of vitamin D because the skin has a precursor molecule called 7-dehydrocolestrol that is activated by UV light which causes it to travel to the liver and kidneys to be converted into calcitrol which is the active form of vitamin D

What is the outermost layer of skin?

The epidermis is the outermost layer of skin

What is the epidermis made up of?

The epidermis is made of keratinized stratified squamous epithelium

What is the overall structure of the epidermis?

Overall, the epidermis is multi-layered, it is durable, and it is water-resistant

How many main cell types are there in the epidermis?

There are 4 main cell types in the epidermis:

1. Keratinocytes

2. Melanocytes

3. Dendritic cells

4. Tactile epithelial cells

How many layers are there in the epidermis?

There is up to 5 layers in the epidermis

Which type of cell is the most abundant?

Keratinocytes are the most abundant cells in the epidermis

What do the keratinocytes of the epidermis produce?

The keratinocytes produce keratin

What do the melanocytes of the epidermis produce?

The melanocytes produce pigment called melanin

What are dendritic cells part of?

Dendritic cells are part of the immune system

What are the tactile epithelial cells involved in?

The tactile epithelial cells are involved in touch sensations

Is the epidermis just sitting on top of the dermis?

No, the epidermis is not just sitting on top of the dermis, it has downward projections that extend into the dermis and the dermis has matching dermal papillae that project upward to lock into each other

What are epidermal pegs?

Epidermal pegs are the downward projections from the epidermis into the dermis that holds them together

What does the interlocking connection between the dermis and epidermis prevent?

This interlocking connection prevents the layers from separating under stress like friction or pulling

What % of epidermal cells do keratinocytes make up?

Keratinocytes make up about 85% of the epidermal cells

What is the main job of keratinocytes?

The main job of keratinocytes is to produce keratin

What is keratin?

Keratin is a tough fibrous protein that protects the body form things like abrasion, heat, microbes, and chemicals

What are keratinocytes doing?

Keratinocytes are constantly building the body’s protective armour

What do keratinocytes produce?

Keratinocytes produce keratin as well as lamellar granules

What do lamellar granules do?

Lamellar granules release a lipid or fatty sealant that reduces water loss from the body, it prevents excess water fron entering, and it blocks foreign substances form entering

What happens to keratinocytes as they become more superficial?

As keratinocytes become more superficial, they start to change

What happens as keratinocytes reach the top layer?

At the top layer (the stratum corneum), keratinocytes become flat, dead, overlapping cells

What are the keratinocytes in the stratum corneum like?

The keratinocytes in the stratum corneum are like shingles on a roof

What does the arrangement of overlapping keratinocytes in the stratum corneum allow?

This overlapping arrangement of keratinocytes in the stratum corneum allows for protection and water resistance

What are melanocytes responsible for?

Melanocytes are the cells that are responsible for the pigment in the skin

What % of epidermal cells do melanocytes make up?

Melanocytes make up about 8% of the epidermal cells

What is the main job of melanocytes?

The main job of melanocytes is to produce melanin

What is melanin?

Melanin is the pigment that contributes to skin colour and protect against UV radiation

What does melanin do inside keratinocytes?

Inside keratinocytes, melanin forms a protective shield over the nucleus to prevent the DNA from damage

What are melanocytes vulnerable to?

Although melanocytes protect nearby keratinocytes from UV radiation, they themselves are vulnerable to UV damage

What is the shape of melanocytes?

Melanocytes have a unique shape, they have a central body, but they also have long arm like processes that extend out and connect with nearby keratinocytes

What is the ratio of melanocytes to keratinocytes?

The ratio is about 1 melanocyte to about 30 keratinocytes

How do melanocytes share melanin?

The melanocytes package the melanin into granules and transport it to keratinocytes via their long arm-like processes

What are dendritic cells also known as?

Dendritic cells are also known as Langerhans cells

What are dendritic cells?

Dendritic cells are the immune defenders of the epidermis

What % of epidermal cells do dendritic cells make up?

Dendritic cells make up about 5% of the epidermal cells

What is the key role of dendritic cells?

The key role of dendritic cells is recognizing invading microbes

How do dendritic cells recognize microbes?

The dendritic cells use specialized receptors which are pattern recognition receptors (PRRs), that include toll-like receptors (TLRs) that are able to recognize specific chemical patterns shared by many pathogens

Dendritic cells also have long branching processes that extend between the keratinocytes which allows them to survey a large area of epidermis

What can dendritic cells be easily damaged by?

Dendritic cells can be easily damaged by UV light which means excessive UV exposure can weaken the skins immunity in addition to damaging DNA

What are tactile epithelial cells also known as?

Tactile epithelial cells are also known as Merkel cells

What is the least abundant cell of the epidermal cells?

The tactile epithelial cells are the least abundant of the epidermal cells

What % of epidermal cells do the tactile epithelial cells make up?

The tactile epithelial cells make up about 2% of the epidermal cells

What are the tactile epithelial cells involved in?

The tactile epithelial cells are involved in detecting touch

What can tactile epithelial cells sense?

Tactile epithelial cells can sense things like light touch and pressure, they can detect different textures, and they can help find details

What do the tactile epithelial cells connect to?

The tactile epithelial cells connect directly to sensory neurons

What do tactile epithelial cells form?

Tactile epithelial cells form a structure called the nonencapsulated sensory corpsucle also known as the tactile meniscus

Where are the tactile epithelial cells found?

The tactile epithelial cells are found in the deepest layer of the epidermis because they are positioned close to underlying nerve endings for communication

What is the deepest layer of the epidermis?

The deepest layer of the epidermis is the stratum basale

What does the stratum basale consist of?

The stratum basale consists of a single layer of cells that are simple cuboidal to columnar in shape

What do the cells of the stratum basale sit along?

The cells of the stratum basale sit along the basement membrane

Where are new cells made?

The stratum basale is the layer where new cells are made

What does the stratum basale contain? What does this do?

The stratum basale contains epidermal stem cells that undergo mitosis to produce new keratinocytes

Where do all keratinocytes start?

All keratinocytes start in the stratum basale

What happens as new keratinocytes are produced in the stratum basale?

As new cells are produced, they get pushed up to become more superficial and they gradually change as they get closer to the surface

What are cells in the stratum basale attached to? How?

Cells in the stratum basale are strongly attached to each other via the desmosomes and to the underlying basement membrane via hemidesmosomes

What layer is just above the stratum basale?

Just above the stratum basale is the stratum spinosum

What is the stratum spinosum made up of?

The stratum spinosum is made up of 8-10 layers of keratinocytes

How are the keratinocytes different in the stratum spinosum compared to the stratum basale?

The keratinocytes in the stratum spinosum are larger and more rounded than the cells in the stratum basale

What do keratinocytes produce at the layer of the stratum spinosum? What do they do?

At the layer of the stratum spinosum, keratinocytes produce coarse bundles of keratin filaments, which anchor the desmosomes and hold the cells tightly together, this gives the skin strength and flexibility

Where does the name spinosum come from?

The name spinosum comes form the fact that under a microscope these cells have spiky attachments

What other type of cells besides keratinocytes are found in the stratum spinosum?

Other than keratinocytes, dendritic cells, and melanocyte processes are also found in the stratum spinosum

What is the epidermal layer above the stratum spinosum?

The epidermal layer above the stratum spinosum is the stratum granulosum

What happens in the stratum granulosome?

In the stratum granulosome, keratinocytes begin their final transformation

What is the stratum granulosome comprised of?

The stratum granulosome is comprised of 3-5 layers of flattened keratinocytes

Where does the degeneration and death of cells occur?

The degeneration and death of cells occurs in the stratum granulosum

What is the degeneration and death of cells called?

The degeneration and death of cells is called apoptosis

How does apoptosis occur?

Apoptosis starts to occur in the stratum granulosum. This is when the nucleus starts to breakdown, the organelle begin to degenerate, and the cells lose the ability to carry out normal metabolism

What does the stratum granulosome mark?

The stratum granulosome marks the transition where there are living cells below it and dead cells above it

What do the keratinocytes in the stratum granulosome have?

The keratinocytes in the stratum granulosome have lamellar granules that secrete and release a lipid-rich water-repellant sealant

Where is the lipid-rich, water-repellant sealant deposited?

This sealant is deposited between cells of the stratum granulosome and it is present and also involved with the stratum lucidum and stratum corneum (G, L, C)

Where are the epidermal ayers present?

All 5 layers of the epidermis are present in thick skin, but only the stratum granulosome, stratum spinosum, and stratum basale are present in thin skin like the eyelids

Where is the stratum lucidum only present?

The stratum lucidum is only present in thick skin like the palm of your hands, soles of our feet, as well as finger tips and toe pads

What is the stratum lucidum comprised of?

The stratum lucidum is comprised of 4-6 layers of flat, dead keratinocytes

What do the cells of the stratum lucidum not contain? Why?

The cells of the stratum ludicum have no nucleus and no organelles because they are dead