Integumentary System Midterm 1

Main Layers of the Integument

Cutaneous Layer (skin) and Subcutaneous Layer (beneath the skin)

Cutaneous layer (skin)

Epidermis (stratified squamous epithelium) and dermis (dense irregular connective tissue)

Epidermis vs dermis & subcutaneous layer

Doesn’t contain blood vessels, other two contain blood vessels

Largest organ in our body

The skin

Integumentary System

First line of defense against external environment, protects organs within body and prevents dehydration

How does the skin help regulate its temperature?

Hot environment: sweating (cools the body)

Cold environment: hair stands up to trap heat

Why does the integument excrete substances?

Aids our skin in waste removal (sweat contains water, salt, and other components)

What are examples of substances that can be absorbed through the skin?

Certain substances like drugs and skincare products can be absorbed through the skin

Production of Vitamin D

Begins in the skin upon exposure to sunlight (Vitamin D is crucial for bone health)

What tissue type and protective protein are found in the epidermis?

Stratified squamous epithelium containing keratin for resistance to friction and trauma

Does the epidermis contain blood vessels, and how do its cells receive nourishment?

It’s avascular (lack of blood vessels), receives its nutrients and have their waste removed via the connective tissue nearby

Why is it important for the epidermis to be stratified?

The layers make it resistant to abrasion

What type of tissue forms the dermis and how are its fibers arranged?

Dense irregular connective tissue with fibers arranged irregularly making the tissue well-suited to resist tension in ALL different directions

Is the dermis vascular, and what role do its blood vessels play regarding the epidermis?

Highly vascularized, the blood vessels in the dermis nourish the cells of the epidermis

Subcutaneous layer (hypodermis) tissues

adipose tissue and areolar connective tissue

Is the hypodermis vascularized, if so then why?

Vascularized because it’s composed of connective tissues

Adipose tissue function in the subcutaneous layer

Heat insulation, cushioning, and energy storage

How do the protective features of adipose tissue benefit the body?

Protects from heat loss to external environment and provides cushioning for body’s internal structures

Epidermal cells

Keratinocytes, line the wall of hair follicle and aids in epidermal regeneration when injured

Percentage of epidermal cells that are keratinocyte stem cells, and function:

Approx. 10%, they’re capable of dividing throughout our lives, generating new keratinocytes

Deepest layer of the epidermis

Stratum basale, which is where the keratinocyte stem cells are found

Layers epidermis has depending on skin thickness

4 or 5 layers

Skin that has 5 layers

Thick skin, found in hairless areas like palms and soles

Skin that has 4 layers

Thin skin, found in areas that have hair

(areas that have hair can ONLY have 4 layers not 5)

Skin layers found in BOTH thin skin and thick skin

Stratum corneum (most superficial), stratum granulosum, stratum spinosum, stratum basale (deepest layer)

Layer present ONLY in thick skin

Stratum lucidum

Mnemonic for skin layers

Come (corneum) Lets (lucidium) Get (granulosum) Sun (spinosum) Burned (basale)

Cells found in ALL layers of the epidermis

Keratinocytes are predominant cells, produce keratin, a tough, horny (fibrous) protein, strengthens skin and helps resist trauma and friction

What happens to keratinocytes as they are pushed upward toward the surface of the skin?

They undergo keratinization, becoming progressively more keratinized, and are gradually deprived of nutrients, leading to cell death

How often does the epidermis renew itself?

Every 8 weeks

Desmosomes

Cell junctions that use keratin, provides strength and flexibility to epidermis. Structure that holds live keratinocytes together

Since dying cells are unable to maintain desmosome connections, how do they bind together?

They’re bound by a lipid extracellular matrix that acts as a cement, it cements cells together preventing water from entering or leaving the body

Melanocytes

In stratum basale layer, produces melanin (pigment that gives our skin its specific color). As you age they cease producing pigment (gray hair)

Where is the melanin delivered to and for what purpose?

To keratinocytes in the stratum spinosum to protect the skin from UV damage

Melanin

Determined by genetics, the higher the concentration (specifically eumelanin), the darker the skin color will be

Reason for differences in human skin color

The quantity and type of melanin produced, rather than due to the number of melanocytes

Albinism

Condition where melanocytes are present in the skin but do not produce melanin

Vitiligo

An autoimmune disease where the immune system destroys melanocytes resulting in white patches on the skin

Melanoma

Most aggressive type of skin cancer, occurs when melanocytes divide uncontrollably and invade different organs and tissues of the body

Merkel cells

Found in stratum basale, serve as touch receptors, detecting light touch stimuli. Merkel disks are associated with the dermis, they’re connected to sensory neurons, transmit sensory info to central nervous system

Langerhans cells (Dendritic cells, intra-epidermal macrophages)

Found in stratum spinosum, part of the immune system, they protect our skin from pathogens

*They’re “gatekeepers” protecting our skin against invaders

How do dendritic cells act as intra-epidermal macrophages?

Engulf and destroy invading microorganisms, presents antigens to initiate immune responses against pathogens

Stratum Basale (Germinative layer)

Found at base of the epidermis, deepest epidermal layer and closest to the blood vessels of the dermis. Contains dividing cells that generate new cells throughout our lives

Way cells are held together in the stratum basale

Via desmosomes, the cell junction type that uses keratin

Stratum basale cells

Majority are keratinocytes but melanocytes, melanocytes stem cells, keratinocyte stem cells and Merkel cells are also found

*Stem cells are responsible for the generation of new skin cells

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

New keratinocytes push older ones upwards, older ones move away from nutrition supplied by the dermis and eventually die

How do melanocytes in the stratum basale protect the skin from UV rays?

Produce melanin giving our skin its color, they extend projections between cells of the stratum spinosum and store melanin within these projections to act as a protective shield

The farther the epidermal layer is from the dermis:

The greater the prevalence of dead keratinocytes

Stratum spinosum

Above the stratum basale (cells appeared to be held spiny projections). Contains numerous keratinocytes, Langerhans cells, and dendritic extensions of melanocytes containing melanin pigment

Why are Langerhans cells positioned in the stratum spinosum instead of closer to the skin's surface?

If placed nearer to the surface, they would die due to being too distant from the dermis, which is the source of vital nutrients and oxygen (essential for their survival)

Stratum granulosum

Above stratum spinosum, cells undergo apoptosis (process of programmed cell death, unwanted/damaged cells self-destruct), contains granules involved in keratinization and lipid secretion

Lipid extracellular matrix in the stratum granulosum

Acts as a waterproof layer in the upper layers

Lipid cement

Keeps stratum granulosum cells together, created by the secretion of lipid granules since dead cells cannot “hold” to each other via cell junctions. Serves as a waterproof barrier, prevents water from leaving or entering body through the skin

What happens when a specific lipid in the epidermis (7-dehydrocholesterol) is exposed to UV rays?

It’s converted into a vitamin D precursor, and is absorbed by the body and further converted into calcitriol (active form of vitamin D) primarily in the kidneys and less in the liver

Calcitriol crucial role

Regulates calcium and phosphate metabolism, promoting the absorption of calcium and phosphate from the intestines

Condition children develop if they lack vitamin D

Rickets, which leads to abnormal bone formation

Stratum Lucidium

Above the stratum granulosum, only present in thick skin (skin without hair). Consisting of clear, fat, dead keratinocytes

Stratum corneum

Top layer of the epidermis, above stratum granulosum in thin skin, and above stratum lucidum in thick skin. Consists of flat, dead keratinocytes with lots of keratin (sheds from the body)

Dermis

Dense irregular connective tissue below epidermis, offers resistance to tensile forces in multiple directions. Provides structural support and nutrients to epidermis. Contains blood vessels, nerve endings, hair follicles, and sweat glands

Fibroblasts

Abundant cells in connective tissue, produce fibers such as reticular, collagen, and elastic fibers

Sublayers of the dermis

The papillary layer, and reticular layer. Blood vessels are present in both layers

Papillary layer

The top layer of the dermis, right below the epidermis

Dermal papilla

Found at the top part of papillary layer, lines top of dermal layer, makes wavy surface between epidermis and dermis to increase surface area for nutrients and oxygen diffusion

*Papilla means nipple

Dermal Papillae

Nipple-like structures, they interlock preventing epidermis and dermis from easily separating. Friction can lead to separation and accumulation of interstitial fluid (blister)

Reticular layer

Below papillary layer, contains lots of reticular fibers

Hair shaft vs. hair follicle

One is a portion of hair that sticks out of skin. The other extends into dermis and hypodermis, innervated with sensory nerve fibers increasing sensitivity to light touch stimuli

Hair follicle subdivisions

Bulb (wider portion at bottom of follicle). Root (portion above hair bulb within skin)

Hair papilla

Structure at base of hair bulb, contains stem cells for hair growth and pigment

Arrector pili muscle

Associated with hair follicle, it contracts involuntarily causing hair to stand (goosebumps). Nerve fibers from motor neurons stimulate contraction

Sebaceous gland (Glandular epithelium)

Classified as exocrine glands, associated with hair, only found in thin skin. Produces sebum covering hair shaft and skin surface. Excessive production of sebum clogs sebaceous ducts leading to infections (main cause of acne)

Sebum

Oily, improves waterproofing preventing skin from drying. Has antibacterial properties, helps prevent bacterial infections on skin. Frequent washing removes antibacterial properties

Sweat glands

Eccrine (sudoriferous glands/sweat glands). Apocrine (scent gland/modified sweat gland). Both release secretion in an eccrine (exocytosis) manner

Eccrine sweat glands (sudoriferous gland)

Work as soon as we’re born, found all over the body deep in dermis within reticular layer. Regulates body temperature and waste secretion, also releases sweat due to emotional stress. Reaches the surface via a duct

Eccrine sweat glands (contd.)

Lined with keratinocytes, aids in epidermal regeneration. Sweat is made from filtration of blood plasma, is clear and odorless. Contains water, salts, and other components

Apocrine sweat gland (Scent gland, Modified sweat gland)

Begin to work in puberty, found in axilla, groin and genitalia. Located in dermis, associated with hair. Secretion contains lipids and proteins, bacteria on the skin metabolize them producing body odor

*Pass through ducts that open into hair follicles, secretion follows pathway of hair root and reaches skin surface

Sensory receptors

Distributed throughout the body detecting stimuli and convert them to electrical signals. Signals transmitted to brain interpret them, making us aware of sensations. Touch & pressure (mechanoreceptors), temperature (thermoreceptors), and pain (Nociceptors).

Mechanoreceptors

Detect mechanical deformation in skin and hair. Include merkel cells, tactile corpuscles, lamellated corpuscles, root hair plexus

Tactile corpuscle (Meissner corpuscle)

Found in dermal papilla, activates in response to light touch

*Light touch detected isn’t as light as the ones detected by Merkel cells

Lamellated Corpuscle (Pacinian Corpuscle)

In hypodermis, detect deep pressure, appear to have several layers

Hair Root Plexus

Wraps around hair follicles, detecting movement of hair on skin surface. Allow us to feel when mosquito lands on skin

Free nerve endings

Detect sensations (itch/tickle), found throughout the skin. Detect pain (nociceptors, in dermis, activated by tissue damage), detect temperature (thermoreceptors, in dermis).

Severity of Burns

First degree affects epidermis. Second degree (partial thickness burns) affect epidermis and part of dermis, are painful (activation of nociceptors). Third degree (full thickness burns) affects epidermis, dermis and subcutaneous tissue, less painful (nociceptors are destroyed)

Hypovolemia

Dehydration and low blood volume due to loss of lipid cement caused by burns.

A 4-year-old child touches a hot stove and sustains a full-thickness (third-degree) burn to the right palm. Despite the severity of the injury, the burned area is painless. What layer(s) of the skin is(are) more likely affected?

epidermis, dermis

A 4-year-old child touches a hot stove and sustains a burn to his right palm that is described as painless, with a yellowish aspect. What layer(s) of the integumentary system was(were) most likely affected?

epidermis, dermis, hypodermis

A 4-year-old child touches a hot stove and sustains a burn to his right palm that is described as painless, with a yellowish aspect. From superficial to deep, What layer(s) of the epidermis was(were) most likely affected?

stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale

A 4-year-old child touches a hot stove and sustains a burn to his right palm that is described as painless, with a yellowish aspect. What type of burn would this most likely be?

third-degree burn

Second-degree burns are very painful. True or False

True

Which specific layer of the epidermis is found in the skin of the sole of the foot but is absent in the epidermis of the thigh?

Stratum lucidum

Stratum ______ contains dividing stem cells, melanocytes, and Merkel cells

Basale

Stratum _______ are clear and flat, contains dead keratinocytes with a large amount of keratin; absent in areas with hair follicles

Lucidum

Stratum _______ is the last layer where cells are still alive and contains lamellar granules that release lipid-rich, water-repellent secretion

Granulosum

Stratum _______ contains many-sided keratinocytes with bundles of keratin intermediate filaments, and armlike projections of melanocytes and intraepidermal macrophages (also called Langerhans or dendritic cells)

Spinosum

Stratum ________ are rows of dead, flat keratinocytes that contain mostly keratin

Corneum

A common sign of skin cancer is very dark spots in the affected area. Based on your knowledge of the cells present in the integumentary system, overproduction of what cell type is responsible for these dark spots?

Melanocytes

A patient develops a localized rash after applying a new cosmetic lotion. A biopsy shows increased antigen-presenting activity in the epidermis and recruitment of T-cells. Which of the following cell types is most likely responsible for initiating this immune response?

Langerhans cells

A patient reports a reduced ability to detect deep pressure in their skin. Damage to which of the following dermal structures is most likely responsible?

Pacinian (lamellated) corpuscles

Which of the following best explains why a superficial papercut may bleed only slightly or not at all?

Blood vessels are primary located in the dermis

Which of the following dermal receptors would be primarily responsible for detecting a light breeze?

Meissner’s corpuscles

Dermal papillae project into the epidermis and play an important role in:

Increasing surface area for exchange between dermis and epidermis, anchoring the two layers