Chapter 4: Membranes/Integument Flashcards
What are membranes?
continuous sheets of tissue composed of
1. a surface epithelium
2. underlying layer of connective tissue
What is the function of membranes?
cover and protect the internal and external structures and tissues of the body
What are the 4 types of membranes?
- serous membranes
- mucous membranes
- cutaneous membranes
- synovial membranes
What is the integumentary system composed of?
composed of a cutaneous membrane and the associated accessory structures (nails, hair, NS, exocrine glands)
composed of all 4 tissue types
What are the 2 principal components of the cutaneous membrane?
epidermis & dermis
serous membranes
line body cavities and organs that reside within them (pleural, pericardial, peritoneal membranes)
-thin sheets of simple squamous ET
-produce lubricating surface fluid: serous/transudate fluid
mucous membranes
line cavities that are open to body’s exterior.
(digestive, reproductive, respiratory, urinary tracts)
-impede entrance of pathogens
-usually simple columnar or cuboidal ET
cutaneous membranes
forms majority of skin
-stratified squamous ET
(epidermis and dermis)
synovial membranes
line and enclose movable joints (elbow, knee, hip).
secrete synovial fluid to reduce joint friction
Epidermis
outer (superficial) layer of epithelial cells
-stratified squamous ET
what are the 5 layers (Strata) of the epidermis (thick skin)?
- stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum germinativum (basale)
stratum corneum
-outer most layer of keratinocytes
-thickness depends on location and physical stress
(highly keratinized in thick skin. nucleus remains in thin skin.)
stratum lucidum
lucid = clear (this thin layer appears clear)
-contains form of keratin-eleidin; may or may not have nucleus
-only apparent in thick skin
stratum granulosum
-flattened keratinocytes containing protein (keratohyalin granules; granular appearance
stratum spinosum
relatively thick cell layer
-spindle-shaped keratinocytes beginning keratin production process
stratum germinativum (basale)
single layer of active simple cuboidal stem cells capable of cell division
-replaces epithelium every 20-30 days
-growth and maintenance of accessory structures (glands, nails, hair).
-melanocytes and tactile epithelial (Merkel) cells reside here
Basement membrane
binds all epithelial tissue to underlying connective tissue
-thin layer of proteoglycans and extracellular protein fibers acting as glue.
(not visible unless stained)
Dermis
connective tissue housing integuments accessory structures and blood vessels
-connects epidermis to underlying structures
-composed of CT fibers (collagen, elastin) & many cell types
What are the 2 layers of the dermis?
- papillary region
- Reticular region
Papillary layer of the dermis
“nipple”
-Areolar CT
-dermal papillae invade epidermis, bringing papillary plexus close to epithelial cells
Reticular layer of dermis
“net”
-dense irregular CT, elastic fibers, fibroblasts, adipose cells, hair follicles, nerves, blood vessels, glands
-strong attachment for epidermis
-support for accessory structures (hair, glands, nerves, blood vessels)
Subcutaneous layer (Sub-O), hypodermis, or superficial fascia
-areolar and adipose CT
-firm attachment for skin to the underlying tissue (muscle and bone)
Glabrous skin
areas devoid of hairs
-lips, palms, fingers, sole of feet
Hair follicle- function
Hair production:
- Produce hairs that protect skull
- Produce hairs that provide delicate touch sensations on general body surface
hair bulb
contains actively dividing stratum germinativum cells that produce and elongate hair
-enlarged region of hair at base of follicle
hair (Dermal) papilla
supplies follicles with nutrient rich blood & sensory nerve fibers
-cone shaped projection of dermis into hair bulb
hair root
incompletely keratinized hair epidermal cells that will become mature hair
hair shaft
completely keratinized epithelial cells from middle of follicle to hair tip (exposed)
What are 2 types of glands?
- sebaceous gland
- sweat gland
Sebaceous gland
“grease”
-associated with hair follicles, secreting oil on hair shaft or tissue surface
-secrete sebum
-holocrine mechanism- whole cell ruptures to release contents
-blockage of this can cause inflammation; folliculitis>acne
Sweat glands
secrete watery liquid to skin’s surface.
2 types:
- eccrine (merocrine) : thermoregulation
- Apocrine : axilla, breast areola,… stimulated by emotional stress/ sexual excitement
Cutaneous sensory structures
nerve fibers in skin control blood flow, adjust glandular secretions, and monitor sensory reception in dermis and epidermis
(5 main types are free nerve endings, Tactile (meissner’s) corpuscles, lamellar (Pacinian) corpuscles, Merkel discs, and bulbous corpuscles (Ruffini endings)
Free nerve endings
non-specialized nerve fibers capable of pain sense, hot or cold, light touch, movement of hair shaft
Tactile (meissner’s) corpuscles
specialized nerve fibers that perceive light touch and pressure; in lips, finger tips…
Lamellar (Pacinian) corpuscles
specialized nerve fibers, respond to deep vibration and deeper pressure (look like onion with many layers)
Merkel discs
perceive light touch where hair is lacking, like finger tips.
-high tactile discrimination, reading braille..
bulbous corpuscles (ruffini endings)
encapsulated nerve endings; around fingernails; detect skin stretch and modulate grip strength
Pneumonic device to remember the 5 layers of the epidermis in order:
Come
Lets
Get
Sun
burnt
= top down
Before
Signing
Get
Legal
Counsel
=bottom up
What 4 cell types is the epithelium made of?
Keratinocytes
melanocytes
tactile epithelial (Merkel) cells
Langerhans cells
Keratinocytes
-form majority of epithelium
-specialized cell producing water proofing protein: keratin
-also produce carotene and vitamin A
melanocytes
-found in deepest layers of epidermis
-secretes Melanin into adjacent cells which absorbs damaging UV light on skin
Tactile epithelial (Merkel) cells
specialized sensory cells
in sensitive areas lacking hair, cells perceive pressure & release chemical messengers
Langerhans cells
tissue-resident macrophages of skin
-help initiate immune responses upon pathogen exposure
Strata
Distinct layers (of epidermis)
the reticular layer of the dermis is made of ___________
denise irregular CT
the papillary layer of dermis is made of __________
Areolar CT
The epidermal cells that protect other cells from invading microbes are _________
langerhan’s cells
What is the most superficial layer of the epidermis?
stratum corneum
The glands that secrete a waxy substance in the skin are ____________
sebaceous glands
Identify:
Tactile Meissner’s corpuscle
identify:
Sebaceous gland
Identify:
Hair papilla
Identify both parts:
- epidermis
- papillary layer of dermis
Melanocytes are found in which layer of the skin?
stratum basale
Which skin layer are Langerhans found?
statrum spinosum
Exocrine Glands: functions
- Assist in thermoregulation
- Excrete wastes
- Lubricate epidermis
nails: function
- Protect and support tips of fingers and toes
Tattoos
-where are they in the skin layers?
initially, in epidermis and through basement membrabe, down to dermis.
After 2-3 months, basement membrane of epidermis is fully re-formed, so ink is only present in the dermis.
