Chapter 5: The Integumentary System Flashcards
The integumentary system
Function: to cover the entire outer surface of the body
Includes: skin, hair, nails, certain glands, and sensory receptors
Skin functions
Functions:
- protects the body from injuries, mold/bacterial invasion, UV damage, and dehydration
- acts as a receptor for sensory input
- regulates body temp (sweat glands)
- secretes waste (salts, water, urea)
- creates vitaminD from cholesterol when under sunlight
What are the structures of the skin?
2 layers:
1) the epidermis (upper layer)
2) the dermis (lower layer)
3) the subcutaneous layer (fat layer under dermis)
(Note - the subcutaneous layer is not part of the skin, but it helps to support the skin)
Epidermis
Composed of keratinized stratified squamous epithelium. It will renew itself every 30-40 days
Contains 4 major cells and 5 cell layers:
4 Cells - Keratinocytes, Melanocytes, Langerhans cells, Merkel cells
5 Cell layers - Stratum basale, Stratum spinosum, Stratum granulosum, Stratum lucidum, Stratum corneum
Keratinocytes
90% of the epidermis
Functions:
- Produces keratin (fibrous protein)
- protects skin and underlying tissues from heat and chemicals
(Note: the surface cells are dead and only contain keratin)
Melanocytes
8% if the epidermis
Function:
- will secrete melanin to keratinocytes
- made of spider-shaped epithelial cells
- found near the basal surface of their cell
Langerhans cells
Function:
- alert other immune cells about potential invaders
(Note: they come from red bone marrow and make their way into the epidermis)
Merkel cells
Function:
- help with touch sensations, and contacting sensory neurons
(Found deep in the epidermis)
Stratum basale
Deepest layer which is attached to the dermis by the wavy border
Contains a single row of cuboidal/columnar keratinocytes. As well as melanocytes and Merkel cells
Function: help in renewing the epidermis by constantly going through mitosis (pushing up new cells)
Stratum spinosum
Contains 8-10 layers of keratinocytes. Also Langerhans cells and melanocytes.
Function:
- provide structural support
- fight against invaders (using langerhans cells)
Stratum granulosum
Contains 3-5 layers of flattened keratinocytes; the cells will lose their nucleus and organelles (apoptosis)
Also contains keratohyalin protein and lamellar granules which release lipid, water-repellant secretions.
Function: it is the transition layer between living cells below and dead cells above.
Stratum lucidum
Present on in thick skin (palms/soles).
Consists of 3-5 layers of clear, flat, dead keratinocytes
Stratum corneum
The outermost layer of skin
Contains 25-30 layers of dead keratinocytes
The lamellar secretions between cells allow for this layer to be waterproof.
Keratinization
The accumulation of more and more protective keratin.
This occurs as more cells move from the deepest layer to the surface layer.
Dandruff
An excess of keratinized cells that shed from the scalp
Dermis
Connective tissue with fibroblasts, adipocytes, macrophages, mast cells, and many fibres.
Contains blood vessels, hair follicles, glands, and nerves.
2 regions:
1) Papillary region
2) Reticular region
Papillary region
It is the upper 1/5th of the dermis
Contains dermal papillae at the junction with the epidermis. These papillae contain capillaries, nerve endings, and Meissners corpuscles (which help transmit touch sensations)
Reticular region
The lower portion of the dermis.
Contains collagen fibres which give skin strength and bind water to keep hydrated, elastic fibres which provide stretch recoil.
Contains pacinian corpuscles (which help for vibration and pressure sensations)
Melanin
Produced by melanocytes; contributes to skin colour.
- amount of melanin produced deciphers colour
- more melanin = more UV protection
- melanin is a buffer that protects our keratin by absorbing UV rays
Albinism
An inherited inability to produce melanin.
Vitiligo
Partial or complete loss of melanocytes from patches of skin
(Michael Jackson)
Hair (or pili)
Present of most skin surfaces (includes eyelashes, eyebrows)
Hair shaft = the visible portion
Hair root = embedded in skin
Hairs can provide slight touch sensations since they have nerve endings attached.
Hair shaft / root structure
Contains 3 rings of dead keratinized cells:
1) medulla - core of large cells
2) cortex - several layers of flattened cells
3) cuticle - single layer of cells that overlap one another.
Hair pigment: controlled by melanocytes at base of the follicle
Hair follicle
A tube-like pocket of epidermis that extended into the dermis.
Hair bulb = base of follicle
Hair papilla = protrudes into bulb and contains capillaries and layers of cells called the matrix.
(These matrix cells divides as hair grows and new king created cells move upwards pushing the old dead cells up and out of the epidermis)
Hair growth cycle
Growth stage - cells of matrix are dividing
Regression stage - matrix cells stop dividing
Resting stage - nothing happens
(After resting stage, old hair root falls out of follicle and new hair grows)
Arrector pili muscle
Smooth muscle which attaches to the hair follicle and raises the hair.
Sweat glands
2 types:
1) Eccrine - a coiled tubular gland emptying into a pore. Helps to regulate body temp. Found in forehead, palms…etc), functions from birth.
2) Apocrine - larger, and empty into hair follicles. Found on head and groin, only starts it function at puberty
Ceruminous glands
Modifies apocrine glands found in skin lining the external ear canal which secretes ear wax.
Sebaceous glands
Alveolar glands connected to hair follicles which secrete sebum which helps soften and lubricate the hair and skin.
Nails
Hard, keratinized epidermal cells.
Consists of:
1) Free edge - extends over digit (white part)
2) Nail body - the visible portion attached to digit
3) Nail root - embedded in skin fold
Nail bed
The skin that is under the nail found in the deeper layers of the epidermis
Nail matrix
Responsible for nail growth by constantly undergoing mitosis to produce more keratin nail cells.
Special functions of the skin
-
Body temp regulation:
- changes in temp slow down metabolic processes, so the surface of the skin stands against the temp. And sweat glands provide evaporative cooling. -
Vitamin D synthesis:
- begins in the skin using cholecalciferol which helps increase calcium absorption
