Chapter 5: The Integumentary System Flashcards
Functions of the integumentary system
- maintain a constant body temperature
- protects the body
- provides sensory information about the environment
- Stores Blood
- Excretes and absorbs
- Synthesizes vitamin D
This system is composed of the skin, hair, oil and sweat glands, nails and sensory receptors
The integumentary system
What is the cutaneous membrane commonly known as?
Covers approx 2 swuare meteres and weight apprx 10-11 lbs (7% of body weight)
Skin
The superficial, thinner portion, composed of epithelial tissue - keratinized stratified squamous cells
Avascular
Epidermis
The deeper, thicker connective tissue portion
Vascular
The Dermis
Layer deeper to the dermis,but not part of the skin. AKA hypodermis
Areolar and adipose tissue
Storage depot for fat and contains large blood vessels that supply the skin
Subcutaneous Layer
Nerve endings contained in the Hypodermis (subcutaneous layer) and sometimes the dermis, that are sensitive to pressure, are called:
Lamellated corpuscles
Lamellated corpuscles are
Nerve endings in the hypodermis and sometimes the dermis that are sentsitve to pressure
This layer of the integumentary system is composed of keratinized stratified squamous cells
Epidermis
What are the 4 principle types of cells in the epidermis?
- Keratinocytes
- Melanocytes
- Macrophages (langerhan cells)
- Tactile epithelialc cells (merkel cells)
Which type of cell makes up approximately 90% of the epidermal cells?
These cells are also arranged in four or five layers and produce the protein keratin
Keratinocytes
This protein is a tough, fibrous substance that helps protect the skin and underlying tissues from abrasions, heat, microbes, and chemicals
Keratin
What do keritanocytes produce that realease a water repellent sealant taht decreases water entry and loss and inhibits entry of foreign materials
Lamellar granules
This is a yellow-red or brown-black pigment that contributes to skin color and absorbs damaging ultraviolet light
Melanin
These cells produce melanin and make up about 8% of epidermal cells
They have long slender projections that exxtend between the keratinocytes and transfer melanin granules to them
Are susceptible to damage from uv light
melanocytes
What do melanin granules do in the keratinocytes?
Cluster over the skin side of the nucleus to sheild it from damage from uv light
These cells arise from red bone marrow and migrate to the epidermis
The help with immune responses against microbes on the skin and they are easily damaged by uv light
Intraepidermal macrophages (langerhans cells)
These cells are the epidermis tactile epithelial cells
Located in the deepest layer of the epidermis where they contact the flattened process of a sensory neuron (merkel or tactile disc)
Detect touch sensations
Merkel Cells and merkle discs
or tactile cells and tactile discs
The 4 strata (layers) of the epidermis that makes up “thin skin”
- Stratum basale
- Statum spinosum
- Stratum granulosum
- Thin Stratum corneum
The 5 strata (layers) of the epidermis for thicker skin (heels, palsm, soles, fingertips)
- Stratum basale
- Stratum Spinosum
- stratum granulosum
- Stratum laucidum
- Thick stratum corneum
What layer does 5 strata thick skin have that 4 layer thin skin does not?
Stratum lucidum
What Strata is thicker in 5 layer than 4 layer skin?
Strata Corneum
This is the deepest layer of the epidermis
Composed of a single row of cuboidal or columnar keratinocytes
Contains stem cells that divide to continually produce new keratinocytes
Stratum Basale
Describe the keratinocytes of the basale layer
- nuclei
- mitochondria
- Rough ER
- cytoplasm re: ribosomes
- single large nuclei
- a few mitochondria
- cytoplasm has many ribosomes
- the golgi complex is small
-some rought Er
This strata of the epidermis is superficial to the basale stratum
Mainly consists of keratinocytes arranged in 8-10 layers
The same organelles of the basale layer, cells are just a little flatter
Stratum Spinosum
What do keratinocytes produce in the stratum spinosum layer?
Coarser bundles of keratin in intermediate filaments compared to the basale layer
Why is this layer called spinosum?
The keratinocytes join together in certain places with desmosomes which makes the appearance of them being covered with thornlike spines
This layer is at about the middle area of the epidermis
Consists of 3-5 layers of flattened keratinocytes that are undergoing apoptosis
Nuclei and organelles of these cells begin to degenerate as they move farther from connective tissue source of life
DEsmosomes and intermediate filaments become more prominent as cells shrink and shrivel
Stratum granulosum
These darkly staining granules of protein are a distinct feathure of cells in the stratum granulosum and they assemble keratin intermediate filamints into keratine
Keratohyalin
These granules are present in the keratinocytes in the granulosum layer and they bind the cell membrane and produce a lipid rich secretion to water proof
lamellar granules
The secretions of lamellar granules are deposited into the spaces between cells in which 3 layers of the epidermis?
- stratum granulosum, stratum lucidium, and stratum corneum
This strata is the transistion space between the living, metabolically active strata and the dead cells of the more superficial strata
Stratum Granulosum
This strata is only present in thick 5 layer skin
consists of 4-6 layers of flattened, clear, dead, keratinocytes that contain a large amount of keratin and thickened plasma membranes
Provides additional toughness to the thick skin
Stratum Lucidum
This layer contains an average of 25-30 layers of dead, flattened keratinocytes
Can range in thickness from a few cells in thin skin to 50 or more cell layers in thick skin
The cells are thin, flat, plasma membrane enclosed packages of keratin
Stratum Corneum
thin or thick
Describe the distribution/layout of the cells in the corneum
- each layer of cells overlaps cells in the next layer like scales
-firmly connected to neighboring cell layers
- plasma membranes of adjacent cells are arranged in complex, wavy folds that fit togehter like a puzzle to hold layers together
- cells are continuously shed and replaced by cells in the previous layer
What is formed by constant exposure of skin to friction that stimulares increased cell production of keratin
A callus(abnormal thickening of the stratum corneum)
The process of cells accumulating more and more keratin as they move into more supericial layers of the epidermis
Keratinization
How often is full thickness of epidermis replaced
4-6 weeks
A hormone like protein that plays a role in the increase of keratinocyte production in the stratum bassale that is a response to damage where epidermis layers are stripped away (burns and abrasions)
Epidermal Growth factor
Second, deeper part of skin; composed of dense irregular connective tissue containing collagen and elastic fibres
Has great tensile strength
Dermis
The cells found in the dermis
fibroblasts, macrophages, adipocytes
Other structures embedded in dermal layer
blood vessels, nerves, glands, hair follicles
2 layers of the dermis
Papillary region
reticular region
This region makes up about 1/5th of the dermis
contains collagen and fine elastic fibres
contains dermal papillae
Papilary region
small, nipple shaped structures that project into the undersurface of the epidermis
dermal papillae
What can/do dermal papillae contain?
All: capillary loops
Some: corpuscles of touch (meissner corpuscles) - tactile receptors
free nerve endings
What do corpuscles of touch (meissner corpuscles) do?
They are tactile receptors and are sensitive to touch
What do free nerve endings do?
No structural specialization; different ones initiate signals that give rise to sensations of warmth, coolness, pain, tickling, and itching
This region of the dermis is attached the subcutaneous or hypodermal layer.
It contains bundles of thick collagen fibres, scattered fibroblasts, and various wandering cells (eg. macrophages)
Some adipose cells and coarse elastic fibres near subQ layer
Reticular region of dermis
These fibres are arranged in a netlike manner and have a more regular arrangements than those in the papillary region
The more regular orientation of these fibres help the skin resist stretching
Collagen fibres
What occupies the spaces between the thick collagen fibres of the reticular region of the dermis?
blood vessels, hair follicles, nerves, sebaceous glands, sudoriferous glands
What is an oil gland also called?
sebasceous gland
What is a sweat gland also called?
sudoriferous gland
What do the combination of collagen and elastic fibres provide for skin?
Strength, extensibility, elasticity
Skins ability to stretch
extensibility
Skins ability to return to original shape after stretching
elasticity
Series of ridge or grooves that appear as either straight lines or as a pattern of loops and whorls (eg finger tips)
Produced during third month of fetal development
Formed by epidermis adhering to dermis between dermal papillae
Create a strong bond between layers
Epidermal Ridges
Function of epidermal ridges
strong bond between dermis and epidermis in areas of higher mechanical stress
greater surface area and therefore better friction and grip
greater surface area also increases the number of corpuscles of touch and therefore incresaes tactile sensitivity
What feature of sweat glands combine with epidermal ridges to produce finger prints
the sweat gland pores open on the tops of the ridges
What three pigments impart a wide variety of colors to the skin?
melanin, hemoglobin and carotene
This pigment causes the skins color to vary from yellow to reddish-brown to black
melanin
These cells produce melanin and are most plentiful in the epidermis of the penis, nipples of the breasts, areaola, face and limbs ; also present in mucous membranes
melanocytes
What determines the difference in skin color if the number of melanocytes is roughly the same for everyone?
the amount of pigment produced by melanocytes and the transfer to keratinocytes
What are the accessory structures of the skin?
hair, skin glands and nails
develop from the embryonic epidermis
This is present on most skin surfaces
This on scalp protects from injury and sun rays and decreases heat loss from the scalp
also detects touch in the hair root follicle
Hair
What is hair composed of?
Keratinized epidermal cells bonded together by extracellular proteins
The superficial portion of hair that projects above the skin surface
the hair shaft
The portion of hair deep to the shaft that penetrates into the dermis and sometimes hypodermis
Hair root
What are the 3 concentric layers of cells of the shaft and hair root
- medulla
- cortex
- cuticle
This concentric layer of the hair shaft and root is composed of two or three rows of irregularily shaped cells that contain large amount of of pigment granules in dark hair, small amount in greay and lack granules in white hair
The medulla
This concentric layer of the hair shaft and root is the middle layer and forms the major part of of the shaft and consists of elongated cells
The cortex
Outermost concentric layer of hair shaft and root that consists of a single layer of thin, flat cells that are the most heavily keratinized
Cells are arranged like shingles with free end pointing toward the end of hair
Cuticle layer
What surrounds the hair root and is made up of an external sheath and an internal sheath?
Hair follicle
Sheath of the hair folicle that is a downward continuation of the epidermis
the external hair follicle sheath
sheath of the hair follicle that is produced by the matrix and forms a cellular tubular sheath of epithelium between the external root sheath and the hair
the internal root folicle sheath
The internal and external root sheath
Epithelial root sheath
the dense dermis surrounding the hair follicle
dermal root sheath
This structure is the base of each hair folicle and its surrounding dermal root sheet and houses the papilla of the hair
The hair bulb
What does the papilla of the hair contain?
blood vessels and areolar connective tissue and hair matrix
This is a germinal layer of cells in the hair bulbl that airses from the stratum basale and these cells are responsible for the growth of existing hairs and producing new hairs
Also produces the cells of the internal root sheath
hair matrix
Bundle of smooth hair associated with hair
Extends from teh superficial dermis of the skin to the dermal root sheath around the side of the hair follicle.
arrector pili
Dendrites of neurons that surround each hair follicle that are sensitive to touch
Hair root plexus
Three kinds of exocrine glands in the skin
- sebasceous
- sudoriferous
- ceruminous
These glands are simple, branched, acinar glands that are usually connected to hair follicles
The secreting portion usually is in the dermis and opens to the hair follicle nexk
Some locations open directly to the suface of skin (where there is no hair like lips)
Sebasceous glands
Where are sebaceous glands absent? small? large?
absent - palms and soles
small - most areas of trunk and limbs
- large in skin of breasts, face, neck, and superior chest
What is sebum?
An oily substance secreted by sebasceous glands
made of triglycerides, cholesterol, proteins and inorganic salts
Function of sebum
Coats surface of hairs to keep them from drying out and becoming brittle
prevents excessive evaporation of water from the skin
keeps skin soft and pliable
inhibits the growth of some bacteria
These glands release sweat into hair follicles or onto the skin
Divided into two main types
Sudoriferous glands
Two main types of sudoriferous glands based on their structure and type of secretion
- eccrine sweat glands
- apocrine sweat glands
These sweat glands are simple, coiled tubular glands
Most common
Most regions of body especially forehead palms and soles
secretory portion usually in deep dermis
Ends as a pore on the surface
Also produce sweat in response to emotional stress “cold sweat”
Eccrine glands
exit to surface directly
Function and compostition of eccrine sweat
thermoregulation - Regulate body temp through evaporation
water, smal amounts of ions, urea, uric acid, ammonia, amino acids, glucose, and lactic acid
Sweat that evaporates from the skin before it is perceived as moisture is called:
Sweat excreted in large amounts and is seen as moisture:
Insensible perspiration
sensible perspiration
Eccrine thermoregulatory sweating pattern
starts with forehead and scalp then extends to rest of body, palms and soles last
Eccrine emotional sweating pattern
starts with palms and soles and axillae and then spreads
Simple coiled tubular glands with larger ducts and lumens than eccrine glands
Apocrine glands
Where are apocrine glands mainly located?
Axilla, groin, areola, bearded face regions
What type of secretion from cells do apocrine cells do?
exocytosis, just like eccrine glands
Where is the secretory portion of apocrine glands?
located int eh lower dermis or upper subcutaneous layer and opens into hair follicles
What glands are modified sweat glands in the external ear that produce a waxy, lubricating substance?
ceruminous glands
Where are the secretory portions of ceruminous glands?
subQ layer
Where do the ducts open
either directly to the surgace of the auditory cancel or into ducts of sebaceous glands
Yellowish material that is a combined secretion of ceruminous glands that secrete into the duct of sebasceous glands
cerumen
Function of cerumen
sticky barrier to prevent entrace of foreign bodies and insects
waterproofs ear canal and prevents bacteria and fungi from entering cells
Plates of tightly packed, hard, dead, keratinized epidermal cells that form a clear, solid covering over the dorsal surfaces of the fingers and toes
nails
3 parts of a nail
Nail body (plate)
Free edge
Nail root
The visible portion of the nail; contain a harder type of keratin and cells do not shed
Below this is a region of epithelium and a deeper layer of dermis
Mostly appears pink due to blood flowing through capillaries in the underlying dermis
Nail body (plate)
The part of the nail body that may extend past the end of the digit; white due to no underlying capilliares
free edge
portion of the nail that is buried in a fold of skin
contains the white crescent shaped area called the lunula
Nail root
Why is crescent shaped area of nail root (lunula) white?
has a thickened region of peithelium so vasular dermis does not show through
what is the thickened region of stratum corneum under the free edge of the nail called?
hyponychium
What is the hyponychium?
The junction between the free edge and the skin of the fingertip / secures nail plate to fingertyp
What is the area that extends from the lunula to the hyponychium and is under the nail plate?
nail bed
what is the narrow band of epidermis that extends from and adheres to the lateral margin of the nail wall and consists of stratum corneum?
cuticle or eponychium
The epithelium proximal to the nail root, contains cells that divide mitotically to produce new nail cells
nail matric
Functions of nails:
- protect finger and toe ends
- provide support and counterpressure to teh palmar surface of the fingers to enhance touch perception and manipulation
- allow us to grasp and manipulate small objects; scratch and groom
Two major types of skin
- thin hairy skin
- thick hairless skin
what causes thicker skin and thicker stratus corneum
mechanical stress
