2.2 The integumentary system Flashcards
What makes up the integumentary system?
The tissues are arranged into an organ
(epidermis + dermis = skin), while together with
its accessory structures (hair follicles, adipose
tissue, sweat glands, nails etc.) form the
integumentary system.
For these accessory structures of the skin, state which types of tissues is it made of:
Accessory structures of skin
Hairs
Arrector pili muscles
Sebaceous glands
Sweat glands
Sensory receptors
Blood vessels
Hairs (E)
Arrector pili muscles (M)
Sebaceous glands (E)
Sweat glands (E)
Sensory receptors (N)
Blood vessels (E-CT-M-N)
For these parts of skin and part of subcutaneous layer, state which types of tissues they are made of:
Skin:
Epidermis –
Dermis -
Subcutaneous layer:
Subcutis/hypodermis
Skin
Epidermis – epithelium (E)
Dermis - connective tissue (CT)
Subcutaneous layer
Subcutis/hypodermis (CT)
What kind of epithelium is the epidermis?
A stratified squamous keratinised epithelium
What kind of tissues makes up the dermis?
Loose and dense connective tissue
What are the two layers of skin?
Epidermis and dermis
What’s beneath the dermis?
more CT in the form of adipose tissue, called the
subcutis or hypodermis
Skin diagram fill in
photos
What are the layers of the dermis and what are they made of?
Papillary layer (Papillary dermis)
* Loose connective tissue
*Reticular layer (Reticular dermis)
*Dense irregular connective tissue
What is the hypodermis layer and what is it made of?
Hypodermis (Subcutaneous tissue/Subcutis)
*Adipose and dense irregular connective tissue
thick skin microscope slide fill in
photos
where can you typically find the dense regular connective tissue?
tendons/ ligaments (only these places)
Which of the following statements about the tissues in the integumentary system is INCORRECT?
The subcutaneous layer (hypodermis) is predominantly connective tissue
Nervous tissue largely exists as sensory receptors in the integumentary system
The epidermis is predominantly made of epithelium
The reticular dermis only contains connective tissue
The papillary layer of the dermis is primarily composed of loose connective tissue
the reticular dermis has glands and hair (epithelium), sensory receptors (nervous) and arrector pili muscles (muscle). It’s not only CT.
What is the classification of the papillary dermis?
Dense regular connective tissue
Dense irregular connective tissue
Loose connective tissue
White adipose tissue
Brown adipose tissue
Loose connective tissue
- not dict: thats reticular dermis
- not drct: that’s only tendons and ligaments
Epidermis is
A layer of stratified squamous keratinised epithelium
sitting on a basement membrane.
Describe the lifespan of a keratinocytes in various situations.
Turnover from basal cell to
keratin layer varies:
* 25-30 days in areas with lots of
friction (e.g. soles)
* 40-50 days in areas of less
friction
* This turnover period is
considerably shortened: 10-15 days in some disease states (e.g.
psoriasis)
- not enough time to form protective layer, sore skin, bleeding)
What are the layers that the epidermis can be subdivided into? Briefly describe their outlook/ functions.
Stratum basale: separates layers from loose connective tissue
Stratum spinosum: spine
Stratum granulosum: granules
Stratum lucidum: dead cells
Stratum corneum: the intermediate layer between living cell layer and dead, consists transitional cell overcoming cell death
When is the stratum lucidum visible?
in thick skin
epidermis layers diagram
photos
What are keratinocytes?
- The cells that constitute the layers of the epidermis.
What do keratinocytes do?
- they play multiple roles essential for skin repair
- They divide (mitosis) in the stratum basale and move upwards towards the
surface.
-> change structure as they do – accumulating more intermediate
filaments, keratohyalin and lamellar granules - Eventually die, their organelles breakdown and the intermediate filaments
and keratohyalin granules fuse to form keratin - Lamellar granules are released to produce waterproofing
describe what keratohyalin is.
a protein that assembles keratin intermediate filaments into keratin.
list the layers of the epidermis and what they do.
- Stratum basale (Basal layer)
* Mitosis of keratinocytes, basal and spot adhering junctions, keratinocytes may
contain melanin granules
* Merkel cells and Melanocytes are found in this layer - Stratum spinosum (Spiny or Prickle cell layer)
* Keratinocytes held together by intercellular bridges and spot adhering
junctions giving them a “spiky” appearance
* Langerhans cells easiest identified in this layer - Stratum granulosum (Granular layer)
* Keratinocytes have accumulated numerous keratohyalin granules,
intermediate filaments, and lamellar bodies
* Cells die – keratohyalin granules combine with intermediate filaments to form
keratin; lamellar bodies are released providing waterproofing substance - Stratum lucidum/corneum (Corny layer)
* Dead keratinocytes filled with keratin
Are all cells found in the epidermis keratinocytes?
No.
Some other cells include:
* Melanocytes
* Tactile epithelial (Merkel) cells
* Intraepidermal macrophages
(Langerhans cells)
epidermal cell layers and non-keratinocytes diagram
photos
What are melanocytes?
dendritic cells that produce melanin and then transfer the
melanin to the keratinocytes.
Explain what melanoma is and its cause
Cancer that develops from melanocytes
Primary cause = UV radiation
what are intraepidermal macrophages and its function
- Macrophages of the skin (Langerhans cells)
- Form a network within the epidermis
- Function as antigen-presenting cells
- Important component of the innate immune system
- Capture and phagocytose invading microorganisms, leave the skin, go to lymph node and present it to lymphocytes to
initiate an immune response
What are tactile epithelial (merkel) cells and their function?
Sensory receptors (touch or mechanoreceptors) within
the stratum basale
* Associated with a sensory nerve ending
* Particularly numerous in thick skin (palms, soles) and lips of the face
what is the dermis and what does it contain?
- Layer of connective tissue underlying the epidermis
- both loose and dense irregular connective tissue
- it supports the epidermis and gives great strength and
flexibility to the skin. - can find collagen and elastic fibres that give flexibility
What is the function of collagen bundles in the dermis and epidermis layer?
collagen bundle have accompanying elastic fibre: control elasticity of skin- wrinkles
What are some skin accessory structures that can be found in the dermis?
- hair follicles
- nerve fibres and sensory receptors
- sebaceous glands
- sweat glands
- blood and lymphatic vessels
What are the two regions that the dermis can be divided into? State where they’re located, what they form and what they’re made out of.
They form interdigitation!
Papillary layer
* immediately below the epidermis
* forms the dermal papilla between the epidermal pegs
* a layer of loose connective tissue (areolar connective tissue)
Reticular layer
* between the papillary layer and the hypodermis/subcutis
* the ‘true’ dermis and is a dense irregular connective tissue
Epidermis, dermis, and hypodermis layer diagram
photos
Thick skin epidermis, dermis diagram
photos
What’s below the dermis? Describe its composition.
the subcutaneous layer/ hypodermis
- a layer of adipose tissue and connective tissue
Why are degrees of burn important?
Stem cells move to produce new from dermis layer if not very burnt
What are the levels of burns and what parts of the skin layer do they impact? How long do they take to recover? Provide an example of each.
- First degree burns:
- ust damage to the epidermis (e.g., sunburn)
- usually does not result in blistering
- These are usually repaired after a week.
- e.g. sunburn - Second degree burns:
- typically involve both the epidermis and dermis.
- The skin appears red, blistered, and is swollen and painful, often require medical treatment.
- Depending upon the severity of the burn, epidermal stem cells may survive within deeper hair follicles and glands and regrow the epidermis over time. - Third-degree burns
- classified as full-thickness burns, involving all three layers - the epidermis, dermis, and subcutis (hypodermis).
- Underlying structures (e.g., bones, muscles) may also be damaged.
- All accessory structure of the skin are removed, meaning that no epidermal stem cells survive and skin grafts are required for severe cases. Sensory receptors are also removed.
- The integumentary system loses its homeostatic ability to prevent water loss and infection, which can be life-threatening depending upon how much of the body is injured.
Describe the role of 9s
The front and back of the head and neck equal 9% of the body’s surface area.
The front and back of each arm and hand equal 9% of the body’s surface area.
The chest equals 9% and the stomach equals 9% of the body’s surface area.
The upper back equals 9% and the lower back equals 9% of the body’s surface area.
The front and back of each leg and foot equal 18% of the body’s surface area.
The genital area equals 1% of the body’s surface area.
Which of the following (in whole or in part) would you NOT find in the papillary dermis?
Elastic fibres
Meissner’s corpuscle
Collagen bundle
Capillaries
Collagen bundle
Correct answer.
Correct. The papillary dermis is loose CT so you would only find individual fibres of collagen and elastin, not bundles of collagen.
Which of the following is the most superficial of the layers in the integumentary system?
Subcutis
Stratum granulosum
Papillary dermis
Stratum spinosum
Correct answer: stratum granulosum
Correct. Superficial means closest to the surface and so this layer would be most superficial out of the layers presented. Well done!
Which of the following would you find in the dermis?
Elastic bundle.
Tactile epithelial cell
Keratinocyte
Basal adhering junction
Correct answer: elastic bundle
Correct! Well done. Just like collagen bundles, elastic fibres form bundles in the reticular dermis too. It gives skin its elasticity
Which of the following would NOT be found within the subcutis?
White adipose tissue
Collagen bundles
Lamellated (Pacinian) corpuscles
Tactile epithelial cell
Correct answer: tactile epithelial cell
Correct, this is found within the stratum basale of the epidermis. Well done!
free nerve endings (what are they, function of them)
These are the dendritic ends of unipolar neurons that exist in either the epidermis or dermis. They sense temperature (hot/cold; thermoceptors) or pain (nociceptors).
Tactile epithelial cells (merkel cells) (what are they, function of them)
These are found within the stratum basale of the epidermis. They detect touch (mechanoreceptors) and are associated with the ending of a sensory (afferent) axon.
Meissner’s corpuscles (what are they, function of them)
Meissner’s corpuscles are found within the papillary dermis (loose CT), particularly within the dermal papillae of thick skin. They detect touch (mechanoreceptors). They are considered “encapsulated sensory receptors” as they have a CT capsule around them and an afferent axon running away back to the CNS.
Lamellated (Pacinian) corpuscles (what are they, function)
Lamellated or Pacinian corpuscles are found within the reticular dermis and/or subcutis. They detect pressure and vibration (mechanoreceptors). They are an encapsulated sensory receptor that has an appearance of an onion cut in half - lamellae = layers; like the rings within an onion.
sensory innervations diagram
photos
What are the appendages of the skin?
- Hair, Hair Follicles, Arrector pili (arrector- stand on end (thermal regulatory role) goosebumps from these muscles pulling on hair to trap warm air on skin surface) muscles and
Sebaceous Glands - Nails
- Sweat Glands
Describe what hair is made of and its associated structures.
- Hair shaft
- cuticle
- cortex
- medulla - Hair bulb - growing point
- Arrector pili muscle
- smooth muscle - Sebaceous gland
Describe sebaceous glands. (what do they secrete, structure, type of gland, what can control it, how’s it important, properties of secretion)
- Sac like glands that secrete an oily thick substance called
sebum. - Open onto the skin surface via a hair follicle
– Except for regions of hairless skin, e.g. penis, nipples, lips - They are holocrine glands:: whole cell becomes secretion, accumulate product and then burst and becomes secretion
- Secretion is viscous and may become secondarily infected by
bacteria - acne (pimples). - Secretion is controlled by the ANS.
- Activity may be controlled by sex hormones.
- Important lubricant of the epidermis.
process of secretion by sebasceous gland
basal cells ungo mitosis, accumulate lipid droplets, cell death, future, release secretion
stem cells produce sebastoeus gland cells
Describe sweat glands (eccrine)
- Simple coiled glands.
- Open onto the skin surface via a duct at a sweat pore.
- They are merocrine secreting glands: merocrine= secrete through exocytosis
- The secretory portion of the gland lies deep in the dermis.
- Sweat is a mixture of secretory and excretory products.
- There are different forms of sweating:
Emotional
Thermoregulatory - Sweating controlled by the ANS.
What are the two types of triggers for sweating?
- thermoregulatory – cholinergic (acetylcholine)
- parasympathetic nervous system activates this (cholinergic receptor) - emotional – adrenergic (adrenaline, noradrenaline)
- sympathetic nervous system
Hair and its associated structures diagram
photos
What are the types of glands of the skin and their functions?
- Sebaceous - holocrine secretion of sebum
- Eccrine (sudoriferous) sweat glands -
merocrine secretion of sweat
(thermoregulatory & emotional) - Apocrine (odoriferous) sweat glands –
merocrine secretion of sweat (emotional)
Sweat glands diagram
photos
Describe apocrine sweat glands.
- Simple coiled glands with wide secretory lumen.
- Open onto the skin surface via a hair follicle.
- The cells secrete by merocrine secretion (despite their name).
- The secretory portion of the gland lies deep in the dermis –
secretory product is stored. - Secretion is often viscous and may become secondarily infected
by bacteria - body odour. - Glands are concentrated in the axillary and anogenital areas;
Ceruminous glands in ear (wax), mammary glands are also
modified apocrine sweat glands. - Secretion is controlled by the ANS – not thermoregulatory, only
emotional. - Activity may be controlled by sex hormones.
What are the two broad types of skin?
Thick and thin skin
Describe thick skin.
- also referred to as friction or glabrous skin.
- It is found exclusively on the palmar (anterior hand) and plantar (soles of the feet) surfaces. - It can be up to 1.5mm thick but contains no hairs, sebaceous or apocrine sweat glands.
- The only glands present in thick skin are the eccrine (sudoriferous) sweat glands.
- It contains significant interdigitations between the epidermal pegs/ridges and dermal papillae - these are reflected in the surfaces by providing fingerprints (or toeprints) (called dermatoglyphs - “skin pictures”).
- These increase surface area of contact between the dermis and epidermis, providing great adherence and resisting abrasion.
Largest difference between thick skin and thin skin
The largest difference between thick and thin skin is the thickness of the stratum corneum (significantly thicker in thick skin), plus the added layer of the stratum lucidum.
Describe thin skin
- also referred to as hairy skin
- found on all the surface of the body, except where thick skin is found (so the palms and soles of the feet).
- It is typically 0.07-0.15mm thick
- may contain (depending upon where it’s found) all accessory structures of the skin - hairs, arrector pili muscles, sebaceous glands, eccrine (sudoriferous) and apocrine (odoriferous) sweat glands, sensory receptors.
- In certain areas, thin skin may be devoid of hairs and their associated structures - these are regions of hairless skin and are found on the lips of the face, areola of the nipples, and the genitals (labia minora, clitoral prepuce, glans clitoris and penis).
- any sebaceous glands empty directly onto the surface of the epidermis rather than via a hair follicle.
True or false:
Not all skin has dermal papillae, but all skin has a papillary dermis
True. Thick skin predominantly has dermal papillae (upward projections of the papillary dermis), but thin skin often has a flat dermal-epidermal junction
Which of the following is NOT associated with a hair/hair follicle?
Eccrine (sudoriferous) sweat gland
Apocrine (odoriferous) sweat gland
Arrector pili muscle
Sebaceous gland
Correct answer: eccrine (sudoriferous) sweat gland
Correct. Well done. These empty onto the surface of the skin, not via a hair follicle.
Functions of the integumentary system
Protect underlying tissues and organs against impact, abrasion, fluid loss, and chemical attack
Excrete salts, water, and organic wastes by integumentary glands
Maintain normal body temperature through either insulation or evaporative cooling, as needed
Produce melanin, which protects underlying tissue from ultraviolet radiation
Produce keratin, which protects against abrasion and serves as a water repellent
Synthesise Vitamin D3, a steroid that is subsequently converted to calcitriol, a hormone important to normal calcium metabolism
Store lipids in adipocytes in the dermis and in adipose tissue in the hypodermis
Detect touch, pressure, pain, and temperature stimuli, and relay that information to the nervous system
The integumentary system, and the body’s largest organ, the skin, are vital for normal homeostasis. It protects us from the external environment, it is involved in thermoregulations, it is a mechanism for excretion, it produces vitamin D (in areas where people get enough sun), it provides sensory information about the external environment, and is a store of energy.
