Integumentary System Flashcards
It covers the body and is the major external barrier between the outside world and the body.
skin
It represents the interface between the internal body and the external environment.
Skin
It has important protective functions and is constantly renewing itself.
Skin
The primary role of the skin
protection (this includes protection from physical injury, including UV light, and providing a barrier to pathogens)
It is crucial to an animal’s thermoregulation, sensing of its environment, and energy and metabolic functions.
skin
Skin is crucial to?
*to an animal’s thermoregulation
*sensing of its environment
*energy and metabolic functions
It also provides environmental protection, producing pigment and vitamin D, and sensory perception.
skin
The skin also provides what?
*environmental protection
*producing pigment and vitamin D
*sensory perception
It is the body’s largest organ and may represent 12%–24% of an animal’s body weight depending on the species and age.
Skin
Skin may represent how many percent of an animal’s body weight depending on the species and age?
12%–24%
skin consists of the following structures: (5)
*epidermis
*basement membrane zone
*dermis
*appendageal system
*subcutaneous muscles and fat
a genetic disorder that affects the skin, in which there is no melanin production
Albinism
It is a secretion involves exocytosis of membrane-bound secretory vesicles.
Apocrine
This is the major secretion form of epitrichial glands (often referred to as just “apocrine glands”) and eccrine glands.
Apocrine
Apocrine is the major secretion form of what glands?
apocrine glands and eccrine glands
a type of stem cell found in the stratum basale and in the hair matrix that continually undergoes cell division, producing the keratinocytes of the epidermis
Basal cell
extension of the papillary layer of the dermis that increases surface contact between the epidermis and dermis
Dermal papilla (plural = dermal papillae)
the dermis layer of skin between the epidermis and hypodermis, composed mainly of
what?
connective tissue containing blood vessels, hair follicles, and sweat glands
a structure that forms an impermeable junction between cells
elastin fibers made of the protein elastin that increase the elasticity of the dermis
Desmosome
A secretion involves the rupture of the secretory cell, thereby releasing the cytoplasmic contents.
Holocrine
This is the major secretion form of sebaceous glands.
Holocrine
It is a fibers made of the protein elastin that increase the elasticity of the dermis
Elastin fibers
It is a clear protein-bound lipid found in the stratum lucidum that is derived from keratohyalin and helps to prevent water loss epidermis outermost tissue layer of the skin
Eleidin
Eleidin is derived from?
keratohyalin
It is a connective tissue connecting the integument to the underlying bone and muscle
Hypodermis
skin and its accessory structures
Integumentary system
A structural protein produced by keratinocytes that contribute significantly to the structural integrity of the epidermis.
Keratin
It is a granulated protein found in the stratum granulosum
Keratohyalin
A general term referring to epithelial cells of the epidermis, including those of the stratum basale, stratum spinosum, stratum granulosum, and stratum corneum.
Keratinocytes
A specialized dendritic cell found in the stratum spinosum that functions as a macrophage
Langerhans cell
A pigment that determines the color of hair and skin
Melanin
Cells derived from the neural crest produce the pigment melanin.
Melanocytes
It reside within the basal layers of the epidermis, producing and then transferring melanin to keratinocytes.
Melanocytes
An intercellular vesicle that transfers melanin from melanocytes into keratinocytes of the epidermis
Melanosome
It is receptor cell in the stratum basale of the epidermis that responds to the sense of touch
Merkel cell
A superficial layer of the dermis, made of loose, areolar connective tissue
reticular layer deeper layer of the dermis; it has a reticulated appearance due to the presence of abundant collagen and elastin fibers
Papillary layer
A secretory epithelial cells that contribute to the production of sebum, a lipid-rich fluid that coats hair and the epidermis. Clusters of these comprise sebaceous glands.
Sebocytes
Clusters of sebocytes comprise of what?
sebaceous glands
It is the deepest layer of the epidermis, made of epidermal stem cells
Stratum basale
It is the most superficial layer of the epidermis
Stratum corneum
It is the layer of the epidermis superficial to the stratum spinosum
Stratum granulosum
It is a layer of the epidermis between the stratum granulosum and stratum corneum, found only in thick skin covering the palms, soles of the feet, and digits
Stratum lucidum
It is the layer of the epidermis superficial to the stratum basale, characterized by the presence of desmosomes
Stratum spinosum
A skin condition in which melanocytes in certain areas lose the ability to produce melanin, possibly due an autoimmune reaction that leads to loss of color in patches
Vitiligo
Three primary components of the skin
a. Epidermis
b. Dermis
c. Subcutaneous tissue (also known as the hypodermis or subcutis)
two layers of the skin
Epidermis and Dermis
an outer part, which originates from the ectoderm
epidermis
A deeper layer, which is a derivative of mesenchyme.
dermis
It differentiate into follicles, from which hairs arise
Hair buds
Hair buds differentiate into ________, from which hairs arise
follicles
It form as outgrowths of the walls of hair follicles.
Sebaceous and sweat glands
These are highly keratinized epidermal structures enclosing the distal phalanx.
Hooves and claws
It is derive from surface ectoderm, cover most of the skin
Avian species, feathers
Avian species, feathers, which derive from __________ , cover most of the skin
surface ectoderm
The integumentary system comprises the following: (8)
skin
hair
skin glands
hooves
claws
digital pads
horns
feathers
Although it is a modified skin gland, its development is included in association with the female reproductive system.
mammary gland
It is the body’s external covering and largest organ.
skin
This is a complex structure that functions as a protective layer against physical, mechanical, chemical, and biological injury.
Skin
functions of the skin
- as a protective layer against physical, mechanical, chemical, and biological injury
- body temperature regulation, reception of external sensory stimuli, secretion, immune responses, vitamin D synthesis, and body surface pigmentation
- protects internal organs and serves as a barrier to infectious organisms and to noxious and injury-producing agents.
prevents dehydration from the loss of water and is an important part of the immune system.
number of appendages, including hair, sweat glands, feathers, and scales develop from _______.
ectoderm
Through __________ in the skin, we are able to detect temperature, pain, touch, and pressure.
sensory receptors
Through ___________ and _____________, the skin is able to cool the body and regulate its internal temperature.
sweat glands and superficial blood vessels
It provides the first line of defense against infection by sealing and protecting the underlying organ systems from the invasion of pathogenic organisms.
skin
Because the _________ is avascular, the cells begin to die.
epidermis
It is the outermost layer of the epidermis which is continuously flaking off in as much as it contains the oldest dead cells that have been pushed up and away from the blood supply of the dermis several weeks ago.
corneum
It contains highly organized receptors discriminately distributed throughout the body surface dedicated to signaling the central nervous system (CNS) of changing environmental conditions such as temperature or the compression.
Skin
It is the most important in maintaining an internal homeostatic environment so the body organs can function in an orchestrated way. If the temperature is increasing due to the contraction of muscles in sporting activities or in life-threatening reactions, many sweat glands must be activated to increase water evaporation which will prevent the temperature from increasing to levels unsupportable for living functions.
Maintenance of body temperature
The sweat glands on the palms of the hand and soles of the feet are designed to what?
increase grasping effectiveness
Sweat glands on the hands and most of the body are classified as what?
eccrine or merocrine type
The sweat glands under the arms and in the genital areas are classified as what?
apocrine sweat glands
This gland secret body fluids containing unique body chemicals which generate characteristic odors which become our signature. These odors are easily recognized by family dogs and other animals
apocrine sweat glands
It is a multilayered epithelial structure composed of keratinocytes that produce the structural protein keratin.
epidermis
Epidermis is composed of what?
Keratinocytes
It produce the structural protein keratin.
keratinocytes
It is reminiscent of a brick wall, with the keratinocytes representing _____, and intercellular matrix representing the _______.
epidermis
bricks
mortar
From innermost (young) to outermost (old) the layers of the EPIDERMIS are:
stratum basale
stratum spinosum
stratum granulosum
stratum lucidum
stratum corneum
The deepest/innermost layer of the epidermis.
stratum basale
It is a single layer of cuboidal keratinocytes that directly above and attach to the dermis
stratum basale
The two primary functions of the stratum basale are:
1) proliferation
2) attachment of the epidermis to the dermis.
Cells of the stratum basale essentially represent _________ responsible for the generation of all cells of the epidermis.
germinal cells
These cells are the most mitotically active keratinocytes and are the least differentiated
Germinal cells
Stratum basale keratinocytes divide and then “push up” towards the surface, differentiating into cells of the _________.
stratum spinosum
It forms the “floor” of the epidermis and the junction of the epidermis and dermis.
basement membrane
Three major functions of the basement membrane include:
1) forming an adhesion interface between the epidermis and underlying dermis
2) acting as a physical barrier
3) forms the foundation for the generation, differentiation, and repair of the epidermal keratinocytes.
Cells of the stratum basale attach to the basement membrane via protein structures.
hemidesmosomes
These are additional fibrils, which connect the keratinocytes of the stratum basale to the dermis, and the basement membrane to the dermis also provide structural integrity of the dermal-epidermal interface.
Hemidesmosomes
Two other cell types are found dispersed among the basal cells in the stratum basale.
a. Merkel cell
b. Melanocyte
It is the first cell which functions as a receptor and is responsible for stimulating sensory nerves that the brain perceives as touch.
Merkel cell
These cells are especially abundant on the surfaces of the hands and feet.
Merckel celld
It is the second cell. A cell that produces the pigment melanin.
melanocyte
It gives hair and skin its color, and also helps protect the DNA in the nuclei of living cells of the epidermis from ultraviolet (UV) radiation damage.
Melanin
It is located directly above the stratum basale.
stratum spinosum
Cells of the stratum spinosum have prominent cell-to-cell junctions, termed _________, that appear as spiky membrane projections on histology. For this reason, these are referred to as “prickle cells”.
desmosomes
Cells of the stratum spinosum have prominent cell-to-cell junctions, termed desmosomes, that appear as spiky membrane projections on histology. For this reason, desmosomes are referred to as __________.
prickle cells
These are protein complexes that firmly attach keratinocytes to their surrounding cells (intercellular, between cells), thereby providing significant structural integrity.
Desmosomes
These are intracellular (within cells) protein complexes that anchor desmosomes to the cell membranes.
Tonofilaments
The stratum spinosum of canine inguinal skin is ____________, whereas the stratum spinosum of the canine footpad is often ___________.
1-2 cell layers thick
>20 cell layers thick
What is the primary function of the skin?
protection
It sits above the stratum spinosum and directly below the stratum corneum.
stratum granulosum
It is a thin layer of keratinocytes containing dense, basophilic (blue/purple) cytoplasmic structures called keratohyalin granules.
stratum granulosum
dense, basophilic (blue/purple) cytoplasmic structures called __________
keratohyalin granules
It contain components responsible for keratinization, including fibrous proteins (keratohyalin) and a lipid-rich secretory product.
Keratohyalin granules
It should be noted that the stratum granulosum is not apparent in all regions of the skin, particularly in regions of _________.
thin skin (e.g. canine inguinal and axillary skin)
It is a thin, transparent layer of keratinocytes that are becoming less round and have a flatter shape.
stratum lucidum
This is only present in the thicker skin of the palms, soles and digits.
stratum lucidum layer
Its main function is to reduce friction between the stratum corneum and stratum granulosum.
Stratum lucidum
• The stratum lucidum layer is only present in the what areas?
thicker skin of the palms, soles and digits.
What is the main function of stratum lucidum?
to reduce friction between the stratum corneum and stratum granulosu
The name itself comes from the Latin for “clear layer,” which describes the transparency of the cells themselves.
Stratum lucidum
The name stratum lucidum comes from the Latin for “_________,” which describes the transparency of the cells themselves.
clear layer
The ___________ that compose the stratum lucidum are dead and flattened.
keratinocytes
These cells are densely packed with eleiden, a clear protein rich in lipids, derived from keratohyalin, which gives these cells their transparent (i.e., lucid) appearance and provides a barrier to water
Stratum lucidum
Stratum lucidum are densely packed with _________, a clear protein rich in lipids, derived from keratohyalin, which gives these cells their transparent (i.e., lucid) appearance and provides a barrier to water
eleiden
Eleidin derived from what?
Keratohyalin
It is the variably thick (15-30 layers) outermost layer of the skin.
stratum corneum
How thick is the stratum corneum?
15-30 layers
Its cells are flattened eosinophilic keratinocytes that lack nuclei (anuclear).
stratum corneum
What do you call the cell of stratum corneum
Corneocytes
The increased keratinization (also called cornification) of the cells in this layer gives it its name.
Stratum corneum
It is often considered “dead”, retain some metabolic and signaling functions despite having no organelles or nuclei.
Corneocytes
have a thickened, insoluble, hydrophobic, cell membrane and contain abundant keratin
Keratinocytes
This dry, dead layer helps prevent the penetration of microbes and the dehydration of underlying tissues, and provides a mechanical protection against abrasion for the more delicate, underlying layers.
Stratum corneum
Cells in this layer are shed periodically and are replaced by cells pushed up from the stratum granulosum (or stratum lucidum in the case of the palms and soles of feet).
Stratum corneum
The cells in this layer can still be anchored to each other by desmosomes which is why the peeling that occurs with a sunburn peels the damaged epidermal layers in one sheet.
Stratum corneum
The entire layer of the stratum corneum is replaced during a period of about _________.
4 weeks
Desmosomal attachment become more sparse in superficial layers, resulting in sloughing of keratinocytes, a process known as __________.
desquamation
It is essentially a layering of differentially mature keratinocytes, going from least differentiated (stratum basale) to most differentiated (stratum corneum).
epidermis
vitamin and mineral deficiencies (e.g. Vitamin A, zinc, copper, et al.) manifest with integumentary changes including the ff;
hyperkeratosis, defective hair coat quality, and bacterial infections of the skin
These are melanin synthesizing cells located within the basilar c9 deeper region of the epidermis and are histologically recognized as poorly staining “ clear cells”.
Melanocytes
It is therefore largely dependent on the amount of melanin produced by melanocytes.
Pigmentation
Have complex dendritic processes that lie adjacent to keratinocytes and facilitate the transfer of melanin to keratinocytes.
Melanocytes
These are the producers of melanin
melanocytes
It is the process of melanin generation
Melanogenesis
melanocyte-specific organelles called __________.
melanosomes
It is an amino acid required for melanogenesis.
Tyrosine
Within melanosomes, tyrosine is converted into intermediate compounds (e.g. dihydroxyphenylalanine, DOPA) by __________.
tyrosinase
It is a copper-containing enzyme. For this reason, copper deficiency in sheep and cattle results in a characteristic loss of hair coat pigmentation.
Tyrosinase
It serves unique protective roles in the epidermis, including the ability to both scatter and reflect ultraviolet (UV) rays, and as a scavenger of potentially damaging free radicals.
Melanin
It is also a dynamic process, and increased pigmentation (hyperpigmentation) or reduced pigmentation (hypopigmentation) may be associated with various disease cutaneous processes.
Melanization
These are dendritic cells sparsely located within the stratum basale. Although they are functionally different from melanocytes, they also appear histologically as “clear cells”.
Langerhans cells
As dendritic cells, the primary function of Langerhans cells is the ff:
*to take up antigens and present them to
*activate cells of the immune system, such as T cells
It serve as “sentinels” at the interface of the external environment and the immune system.
Langerhans cells
Langerhans cells serves as what?
sentinels
2 Cells of the Epidermis
- Melanocytes
- Langerhans Cells
It might be considered the “core” of the integumentary system (derma- = “skin”), as distinct from the epidermis (epi- = “upon” or “over”) and hypodermis (hypo- = “below”).
dermis
It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands.
Dermis
It is avascular and cells of this layer must get their oxygen and nutrients from capillaries in the dermis
Epidermis
Derma means
Skin
Epidermis (epi)
upon or over
hypodermis (hypo)
below
It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands.
Dermis
Dermis contains the ff:
blood and lymph vessels, nerves, hair follicles and sweat glands
It serves as the structural support foundation of the brick wall that is the epidermis.
dermis
It is composed of a meshwork of collagen-rich fibrous connective tissue.
dermis
It is the primary structural protein of the dermis.
Collagen
An elastic protein, is present in lesser amounts but contributes to flexibility of the dermis.
Elastin
It is made of two layers of connective tissue that compose an interconnected mesh of elastin and collagenous fibers, produced by fibroblasts.
dermis
3 Layers of the Dermis
- Papillary Layer
- Reticular Layer
- Hypodermis
This is made of loose, areolar connective tissue, which means the collagen and elastin fibers of this layer form a loose mesh with abundant ground substance supporting the hydration of the skin.
Papillary layer
This superficial layer of the dermis projects into the stratum basale of the epidermis to form finger-like dermal papillae.
Papillary layer
It contains phagocytes, defensive cells that help fight bacteria or other infections that have breached the skin.
papillary layer
This layer also contains lymphatic capillaries, nerve fibers, and touch receptors called the Meissner corpuscles.
Papillary layer
A defensive cells that help fight bacteria or other infections that have breached the skin.
phagocytes
Papillary layer also contains what?
lymphatic capillaries, nerve fibers, and touch receptors
Touch receptors present in papillary layer
Meissner corpuscles
Are form where the cells of the stratum basale of the epidermis meet the papillae of the underlying dermal layer (papillary layer).
fingerprints
These are unique to each individual and are used for forensic analyses because the patterns do not change with the growth and aging processes.
Fingerprints
Underlying the papillary layer is the much thicker layer, composed of dense irregular connective tissue which resists forces in many directions attributing to the flexibility of the skin.
Reticular layer
This layer makes up around 80% of the dermis and is well vascularized and has a rich sensory and sympathetic nerve supply.
Reticular layer
Reticular layer makes up how many percent of the dermis?
80%
It appears reticulated (net-like) due to a tight meshwork of fibers.
reticular layer
It provide some elasticity to the skin, enabling movement.
Elastin fibers
It provide structure and tensile strength, with strands of collagen extending into both the papillary layer and the hypodermis.
Collagen fibers
It binds water to keep the skin hydrated.
Collagen
It is a layer directly below the dermis and serves to connect the skin to the underlying fascia (fibrous tissue) surrounding the muscles.
hypodermis/subcutaneous layer/superficial fascia
It is not strictly a part of the skin
Hypodermis
It consists of well-vascularized, loose, areolar connective tissue and abundant adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument.
hypodermis
It is a thick connective tissue wrapping that surrounds skeletal muscles anchoring them to surrounding tissues and investing groups of muscles.
Fascia
It is where most of the fat concerns people when they are trying to keep their weight under control.
hypodermis
Adipose tissue present in the hypodermis consists of fat-storing cells called ________. This stored fat can serve as an energy reserve, insulate the body to prevent heat loss, and act as a cushion to protect underlying structures from trauma.
adipocytes
Where the fat is deposited
Hypodermis
Men tend to accumulate fat in what areas?
neck, arms, lower back, and abdomen
Women tend to accumulate fat in what areas?
breasts, hips, thighs, and buttocks
produced by dermal fibroblasts
Dermal collagen, elastin, and ground substance
It does not only generate the structural proteins of the dermis but also play a major role in dermal inflammation and wound healing.
Dermal fibroblasts
The vascular supply for the epidermis and dermal adnexal structures is located within the _________.
dermis
Three distinct layers of vasculature
a. subcutaneous/deep dermal
b. cutaneous plexus
c. papillary plexus
The largest blood supply and is composed of arteries and veins that branch superficially into the middermis to form the cutaneous plexus.
subcutaneous/deep dermal supply
subcutaneous/deep dermal supply is composed of what?
Arteries and veins
It is responsible for supplying blood to the adnexal structures of the dermis, including follicles and glands.
cutaneous plexus
The branches superficially to form a fine network of capillaries and venules called the papillary plexus, which lies directly subjacent to and supplies blood to the epidermis.
cutaneous plexus
Signals from the skin may be conveyed by the ff:
physical change (mechanoreceptors), temperature (thermoreceptors),
or pain (nociceptors)
It exist in all layers of the skin
Sensory receptors
There are six different types of mechanoreceptors detecting innocuous stimuli in the skin:
those around hair follicles
Pacinian corpuscles
Meissner corpuscles
Merkel complexes
Ruffini corpuscles
C-fiber LTM
It respond to physical changes including touch, pressure, vibration, and stretch.
Mechanoreceptors
Mechanoreceptors respond to what?
touch, pressure, vibration, and stretch
It can detect light touch
Hair follicles
Meissner corpuscles in the dermal papillae detect what?
indentation and slipping of objects
in the deeper dermis that detect vibration
Pacinian corpuscles
Pacinian corpuscles in the deeper dermis detect what?
vibration
A reflex in the basal epidermis create an understanding of structure and texture
Merkel complexes
Merkel complexes in the basal epidermis create an understanding of what?
structure and texture
It detect stretch
Ruffini corpuscles
Ruffini corpuscles detects what?
Stretch
It detect pleasant, light tactile sensations.
C-fiber LTMs
C-fiber LTMs detects what?
pleasant and light tactile sensations
2 Encapsulated receptors
Meissner corpuscle and the Pacinian corpuscle
In receptors that respond to stretch, there is a presence of _________ that leads to depolarization via sodium influx.
stretch-activated channels
They respond to painful temperatures, mechanical forces, and chemicals
C and A-delta fibers
thermoreceptors of the body
warm and cold
mainly sense temperatures between 25 to 30C.
Cold receptors
Cold receptors mainly sense temperatures between ____ to ____.
25 to 30C
Noxious heat is detectable by what?
TRPV1, TRPM3, or ANO1 proteins, as well as capsaicin
This may be more responsible for detecting warm temperatures.
TRPV3
for colder temperatures, it is believed that _________ are one of many receptors responsible.
TRPM8 ion channels
These receptors are capable of detecting temperatures from below _____ to ____.
TRPM8 ion channels
16C
26C
This help signal pain that is related to temperature, pressure, and chemicals.
Nociceptors
One of the ion channels families that are present on nociceptive neurons is called ________.
TRP (transient receptor potential) ion channels
fibers that relay pain information
A-delta and C fibers
Painful temperatures, uncomfortable pressures, and chemicals mostly use _______.
C-fibers
These are small and unmyelinated and are primarily involved in thermal and mechanosensitive pain.
A-delta fibers
It proposes that innocuous stimuli may trump painful stimuli if both are present simultaneously.
the gate theory of pain
Free nerve endings
Pain, Heat, Cold
Merkel disks
Touch
Krause end bulbs
Touch
Root hair plexus
Touch
Meissner corpuscles
Touch
Pacinian corpuscles
Pressure
Ruffini endings
Pressure
Accessory structures of the skin include the ff:
hair, nails, sweat glands, and sebaceous glands
It is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratinized cells.
Hair
Strands of hair originate in an epidermal penetration of the dermis called the ________.
hair follicle
It is the part of the hair not anchored to the follicle, and much of this can be exposed at the skin’s surface.
hair shaft
The rest of the hair, which is anchored in the follicle, lies below the surface of the skin and is referred to as the ________.
hair root
The hair root ends deep in the dermis at the hair bulb, and includes a layer of mitotically active basal cells called the _______.
hair matrix
It is surrounded by the hair bulb, which is made of connective tissue and contains blood capillaries and nerve endings from the dermis
hair papilla
It is made of multiple layers of cells that form from basal cells in the hair matrix and the hair root.
hair follicle
Hair serves a variety of functions:
a. including protection
b. sensory input
c. thermoregulation
d. communication.
Each hair root is connected to a smooth muscle called the ________ that contracts in response to nerve signals from the sympathetic nervous system, making the external hair shaft “stand up.”
arrector pili
What is the primary purpose of the standing hair shaft?
to trap a layer of air to add insulation
It is a specialized structure of the epidermis that is found at the tips of our fingers and toes.
nail bed
It is formed on the nail bed, and protects the tips of our fingers and toes as they are the farthest extremities and the parts of the body that experience the maximum mechanical stress
nail body
When the body becomes warm, this gland produce sweat to cool the body.
sudoriferous glands (sweat glands)
Sweat glands develop from epidermal projections into the dermis and are classified as what?
merocrine glands
two types of sweat glands
- Eccrine sweat gland
- Apocrine sweat gland
It is type of gland that produces a hypotonic sweat for thermoregulation. These glands are found all over the skin’s surface, but are especially abundant on the palms of the hand, the soles of the feet, and the forehead
eccrine sweat gland
It is usually associated with hair follicles in densely hairy areas, such as armpits and genital regions.
apocrine sweat gland
These are larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis, with the duct normally emptying into the hair follicle.
Apocrine sweat glands
It is a type of oil gland that is found all over the body and helps to lubricate and waterproof the skin and hair.
sebaceous gland
Sebaceous gland functions
helps to lubricate and waterproof the skin and hair
Sebaceous glands generate and excrete ______.
Sebum
It is a mixture of lipids, onto the skin surface, thereby naturally lubricating the dry and dead layer of keratinized cells of the stratum corneum, keeping it pliable.
sebum
The importance of this system is the complex repair mechanisms that have evolved to restore tissue integrity after injury.
Wound healing
the deposited tissue is predominantly composed of fibroblasts and collagen, resulting in a patch of nonfunctional fibrotic tissue, known as a __________
scar
This tissue protects deeper structures from desiccation and foreign pathogens but lacks the original architecture and function (glands, nerves, hair follicles, etc.) present in unwounded skin.
Scar
Steps of Wound Healing
1) Injury
2) Clotting
3) Plugging
4) Scabbing
The wound breaks open cells and releases their contents. These components attract various defense and repair cells.
Injury
Blood seeps from the vessel and forms a clot. Fibroblasts multiply and migrate to the
damaged area as do white cells called neutrophils, which ingest cell debris and
foreign matter, such as dirt and germs.
Clotting
Fibroblasts multiply and migrate to the
damaged area as do white cells called ________, which ingest cell debris and
foreign matter, such as dirt and germs.
neutrophils
Fibroblasts produce a plug of fibrous
Tissue within the clot, which contracts
and shrinks. New tissue begins to form beneath.
The clot gradually hardens and expels fluid to become a scab, as the tissues heal beneath.
Plugging
The plug hardens and dries into a scab, which eventually detaches.
A scar may remain but usually fades with time.
Scabbing
Both ____________ and __________ are invisible
to human eyes, but exposure to the latter, in particular, is linked to forms of skin cancer.
UV-A and UV-B wavelengths
Skin’s self-defense
melanin
These are melanin-producing cells in the base of the epidermis. They make parcels of melanin granules,
melanosomes, which pass into
surrounding cells.
Melanocytes
When the sun’s ultraviolet rays touch the skin, they convert the precursor vitamin D to a molecule called __________.
vitamin D3
Vitamin D3 follows ametabolic pathway through the liver and finally to the kidneys, where it’s converted into a molecule called _________.
calcitriol
It is essential to healthy bones, because it helps you absorb calcium, which strengthens your skeleton.
Vitamin D
Vitamin D3 function
Helps you absorb calcium
It may form when the skin has been damaged by friction, rubbing, heat, cold or chemical exposure.
blister
Less intensive or aggressive rubbing over long periods of time may cause a _______ to form (instead of a blister).
callus
The skin is composed of two major layers:
superficial epidermis and deeper dermis
The topmost layer, consists of dead cells that shed periodically and is progressively replaced by cells formed from the basal layer.
stratum corneum
It also contains melanocytes
stratum basale
two layers of dermis:
papillary layer with papillae and reticular layer composed of loose connective tissue
deep to the dermis of skin, is the connective tissue that connects the dermis to underlying structures; it also harbors adipose tissue for fat storage and protection
hypodermis
