chapter 5- the integumentary system Flashcards
integumentary system
Covers entires outer surface of the body
Includes skin, hair, nails, various glands, and sensory receptors
Most visible organ of the body
Failing liver- skin turning yellow
Heart failure- pink\light red colour (blood is not being pumped efficiently)
skin
Is the largest organ of the body by surface area (22 square feet) and weight (7% of average body weight)
what are the functions of skin?
Protects the body against:
- dehydration (keratin layer)
- impact and friction injuries
- mold and bacterial invasion
- UV light damage (melanin production)
- Acts as a receptor organ for sensory input
- some sensors are sensitive to temp, touch,
- Regulates body temp (capillary network and sweat glands)
- capillary networks are found near the surface of the skin.
- Secrets some wastes —> urea, salts and water
- Synthesizes vitamin D from cholesterol molecules under action of sunlight
- vit. D helps to absorb calcium. Which is needed for muscle contraction, nerve impulse
structures of the skin
epidermis and dermis
epidermis
outer, thinner layer
dermis
inner, thicker layer
- vascularized (has direct blood flow)
subcutaneous layer
The subcutaneous layer is NOT part of the skin.
also called hypodermis
Located underneath the dermis
epidermis - detailed
composed of keratinized stratified squamous epithelium
Squamous epithelium: flattened irregular shaped cell (looks like a “fried egg”)
Stratified: multiple layers
Keratinized: made up of dead cells that help to protect the living cells underneath
Contains four major types of cells and five cell layers
Epidermis is renewed every 30 to 40 days
Basal cells: basal meaning bottom layer. They are constantly diving by mitosis. Constantly creating new cells.
keratinocytes (90%)- epidermal cell type
produce keratin (fibrous protein) useful for protection
Protect skin and underlying tissues from heat, microbes and chemicals
Also produce lamellar granules: lipid rich secretion, fills spaces around and coats the same. Acts like a waterproofing agent. Helps to make sure we don’t lose water.
Surface cells die and only contain keratin (you can see)
melanocytes (8%)- epidermal cell type
spider-shaped epithelial cells
Secrete and transfer the pigment melanin to keratinocytes
Found near basal surface and their cell projections extend between keratinocytes
langerhas cells (or dendritic cells)- epidermal cell type
rise from red bone marrow and migrate to epidermis
Involved in immune responses
Merkel cells (or tactile epithelial cells) - epidermal cell types
least numerous
Contact sensory neurons and function in touch sensations
Loaded deep in epidermis
epidermal cell layers
Sole of feet, palms of hands thick skin have 5 layers, thin skin like on eyelids have 4 layers
stratum basale
deepest layer, attached to dermis by wavy border
Single row of cuboidal/columnar keratinocytes
cuboidal cells look like a cube. Columnar cells look like a column.
Cells divide by mitosis
Contains melanocytes and Merkel cells
stratum spinosum
8 to 10 layers of irregular-shaped keratinocytes
Cells contain many keratin filaments
Contains langerhans cells and projections of melanocytes (“spider arms”)
The cells are attached to one another very strongly.
stratum granulosum
3 to 5 layers of flattened keratinocytes; nucleus and organelles disintegrate
Cells contain kerayphyalin (protein) and lamellar granules
Lamellar graniles release a lipid-rich, water repellent secretion
Transition layer between living cells below and dead cells above
stratum lucidum
present only in thick skin (fingertips, palm and soles)
Consists of 3-5 layers of clear, flat, dead keratinocytes
Clear because they don’t have any organelles in them.
stratum corner
25 to 30 layers of flat, dead keratinocytes containing keratin
Lamellar secretion (lipids) between the cells waterproofs this layer
dermis
Connective tissue with fibroblasts, adipocytes, macrophages, mast cells, and embedded with fibres
Contains blood vessels, hair follicles, glands and nerves
Consist of two regions: papillary region and reticular region
papillary region
upper 1/5 of dermis
Has dermal papillae at junction with epidermis
These papillae contain capillaries, free nerve endings and meissners corpuscles
what is the purpose of fingerprints?
to create friction
Reticular region
lower portion of dermis
Collagen fibres give skin strength and resiliency and bind water to keep skin hydrated
Elastic fibres provide strech-recoil properties
Stretch marks can appear if the skin is stetted too much.
Contains pacinian corpuscles (look like a onion cut in half)
extensibility
collagen fives us the ability to strech
elasticity
not only stretch but recoil
Skin Colour
many pigments contribute to skin colour but the most important one is melanin
Melanocytes produce melanin
The number of melanocytes are about the same in all people but the amount of melanin produced differs
Exposure of UV light increases melanin production
Melanin absorbs UV radiation
A mole is a benign localized overgrowth of melanocytes
hair and hair follicles
Hair (pili) is present on most skin surfaces
The hair shaft protrudes from the skin while the root is embedded in the skin
Eyebrow, eyelash and nose hairs protect structures from foreign objects
Keep dust out of eyes or nose
Dogs and cats with fur are for thermal benefits
Scalp hair protects from rays and sun
Hair provide touch sensations in certain areas
Light and touch sensation. Ex sitting outside and feel something on your arm (like a bug), you sense this because the bug is moving some of your hairs.
hair shaft and root structures
Consist of three concentric rings of dead keratinized cells:
Thin hair the medulla can be missing
medulla
core of large cells.
two to three rows of irregular shaped cells
cortex
several layers of flattened cells
makes up most of the hair
Single layer of cells that overlap one another from below (like shingles on a roof)
Hair pigment is made by melanocytes at the base of the hair follicle and is transferred to cortex and medulla cells.
Hair can become grey because of progressive decline of melanin production.
White hair, there is no pigment
hair follicle structure
The follicle is a tube-like in-pocketing of epidermis that extends into the dermis
The base of the follicle is expanded as the hair bulb
The hair papilla protrudes into the hair bulb and contains capillaries and a layer of cells called the matrix (matrix are the only ones still living and dividing.)
Matrix cells divide mitotically as the hair grows
Newly created cells move upwards and become dead keratinized cells
growth stage
cells of matrix divide
regression stage
matrix cells stop dividing
resting stage
nothing happens
what happens after the resting stage (give example of scalp hair)
the old hair root falls out of the follicle and a new hair begins to grow
Ex. Scalp hair- has a growth stage from 2-6 years (single hair). Can grow 0.3 mm a day. Regression stage last 2-3 weeks (stops growing, starts to break down). After 3 months (nothing happens in these 3 months) you lose that strand. You lose 90 strands a day.
Ex. Eyebrow hair- follicles are actively growing for 3-4 months, then goes to regression stages, stopes growing and falls out.
Arrestor pili muscle
This is smooth muscle which attaches to the hair follicle and raises the hair
Sensory nerve endings are also found around the hair bulb
Eccrine sweat glands
simple coiled tubular glands emptying into a pore (eg. Palms, soles, forehead)
Functional from birth
Sweat is composed of stare, ions, urea, uric acid, ammonia, amino acids, glucose, and lactic acid (pH 4-6)
Helps to regulate body temperature and has a small role in eliminating wastes
Average person has 3 to 4 million sweat glands.
Produce 600 ml of sweat
apocrine sweat glands
are larger and empty into hair follicles
Found in skin of axilla (arm pits) and groin
Begin to function at puberty
Secretion also contain lipids and proteins (organic components)
When sweat glands on the skin, the bacteria living on skins breaks down lipids and protein, which then causes body odour.
ceruminous glands
are modifies apocrine glands found in skin lining the external ear canal
They secrete the sticky earwax (cerumen)
Helps prevent foreign substances from entering ear
sebaceous glands
simple branched alveolar glands connected to hair follicles
Produce and secrete an oily substance called sebum
Sebum softens and lubricates hair and skin to prevent hair from being brittle
Also prevents dehydration of hair and skin
Also inhibits growth of certain bacteria on the skin
nails
are hard, keratinized epidermal cells
More compacted, and there are other proteins that from cross link tens
the deeper layer of epidermis from the nail bed under the nail
Proximal portion of the nail bed is the nail matrix and is responsible for nail growth
Nails functions to protect the distal phalanx (last bone on finger) and aid in grasping
Nails on average grow 1mm
free edge
extends over digit
nail body
is the visible portion
nail root
embedded in a fold of skin
body temperature regulation
Homeostasis
normal body temperature is 37 +/- 0.5 °C
At normal body temp., conditions are optimal for enzymatic activity
The body core (organs in skull, thoracic and abdominal cavities) temp. Is relatively constant
The shell (skin) temp. Can fluctuate.body can use this to regulate body temp.
vitamin d synthesis
vitamin D is actually a group of closely related compounds
Synthesis of vitamin D begins in the skin with the formation of a precursor molecule, cholecalciferol
It’s required to increase calcium absorption from food.
