Physiology Flashcards
3 ways the integumentary system protects the body
- chemical barrier
- mechanical barrier
- biological barrier
How is integument a chemical barrier
- low pH
- antibacterial secretions (defensin) destroy bacterial cells
How is integument a mechanical barrier
keratinized surface and glycolipids waterproof skin
How is integument a biological barrier
immune cells such as Langerhan’s cells (phagocytes stationed in epidermis)
What else is a part of the integumentary system that helps provide protection
normal flora - 1000 species of resident bacteria
How does integument system provide body temp regulation
- endotherms: body temp regulated internally
- Sweat allows for evaporative cooling, heat release
- Arrector pili muscles generate heat at skin surface
Overview of integument role in cutaneous sensation
- skin receptors sense the environment
- Meissner’s corpuscles and Merkel discs sense light touch
- Pacinian corpuscles in dermis and hypodermic sense pressure
- hair movement senses wind
- raw nerve endings sense cold, heat, pain
Integument role in Vitamins
- modified cholesterol molecules circulate through dermal blood vessels
- converted via solar energy into vitamin D precursor
- liver and kidneys finish activation
- Vitamin D aids in ca absorption
How is the integument system related to CVS?
blood reservoir
- dermal blood holds about 5% of total body volume
- blood vessels can constrict to shunt blood flow as needed (will cool skin surface)
What is the role the integument system plays in excretion
- small amt nitrogen-containing waste from protein metab are eliminated via the skin
- eliminate electrolytes in sweat
Keratinocytes
- location
- function
- outer layer of stratified squamous epithelium
- most abundant epidermal cell
- produce keratin, a fibrous protein
- cell differentiation occurs as progress from deep to outer layers of epidermis “keratinization”
List the four layers of keratinocytes in the epidermis that are always present
deepest to outermost
- Stratum basale
- Stratum spinousum
- Stratum granulosum
- Stratum corneum
Stratum Basale
- deepest layer
- single row of cuboidal/columnar cells
- epidermal stem cells that become stem cells or keratinocytes
- keratinocytes start to express keratin which form intermediate filaments
What are two types of cell connections found in stratum basale
- hemidesmosomes attach cells to basal lamina
- desmosomes attach cells to each other
Stratum spinosum
- several cell layers thick
- active keratin production
- full of weblike keratin filaments: provides strength in many directions
- tonofibrils give spiky appearance (protein filaments that lock keratin fibers together, esp around desmosome connections)
Stratum granulosum
- 2-5 layers of cells
- cells in terminal differentiation
- Keratin granules: dehydration of the cell and cross-linking of keratin fibers
- laminated granules: layers of membrane (from golgi), spaces filled with lipids and glycolipids. Exocytosis creates a lipid-rich waterproof layer around keratinocytes
Stratum corneum
- horny layer (tough)
- 20-30 cells thick, outermost layer
- keratinized: masses of keratin fibrils and protein aggregates
- keratinocytes have lost nuclei and organelles, are dead, dry, flat
- waterproof outer surface
- desmosomes degrade, cells slough off
(keratinocyte processes take 15-30 days)
Thick skin
- location
- what is special about the epidermis
- palms and soles
- additional layer: Stratum lucidum
Stratum lucidum
- under stratum corneum
- flattened, differentiated layers of keratinocytes
- held together by desmosomes
- appears clear
- 2-3 layers of cells
Melanocytes
- specialized epidermal cell
- in stratum basale and hair follicles
- attached to basal lamina by hemidesmosomes, not attached to neighboring cells
- cytoplasmic extensions reach through basal and spiny layers
What does sun exposure of skin do to melanocytes
- darkens existing melanin
- stimulates keratinocyte paracrines
- stimulates melanin production in melanocytes
Melanin production from tyrosine
- melanin is aggregated to structural proteins
- accumulates in melanosomes
- melanosomes are transported to termini of cellular extensions
- keratinocytes phagocytize tips of extensions
- granules are transported to keratinocyte nuclei
- shields nucleus from UV radiation
Langerhans cells
- monocytes derived from cells in epidermis
- most abundant in spiny layer
- phagocytize foreign particles, enter circulation, present antigen to lymphocytes in lymph nodes
- immune defense and surveillance role
Describe the dermis
- CT layer deep to epidermis
- cells and matrix (ECF embedded with fibers)
- rich with nerve fibers, blood vessels, lymphatic vessels (NOT in the epidermis)
- contains most hair follicles and glands
- form dermal papillae
Dermal papillae
- extensions or interdigitations of dermis into epidermis
- fingerprints!
What are the two dermis layers
- Papillary layer
2. Reticular layer
Papillary layer of dermis
- thin
- dermal papillae
- fibroblasts
- collagen fibrils: insert into basal lamina, binding dermis to epidermis
What two cells are found in the dermis
- Mast cells
- skin and mucous membrane CT granulocytes (phagocytes)
- secrete inflammatory mediators histamine, leukotriene, and prostaglandings - Dendritic cells
- derived from monocytes
- in skin, resp. tract, GI tract
- antigen presenting cells
Reticular layer of the dermis
- deep to papillary layer
- thick, dense irregular CT
- more fiber, fewer cells
- lots of collagen
- rich in elastic fibers
- elastin: produced by fibroblasts, stretch and recoil
Vasculature of dermis
- Subpapillary plexus
- Deep dermal plexus
- AV anastomoses
Subpapillary plexus in dermis
- btwn papillary and reticular dermal layers
- extensive capillary network
- extends to dermal papillae and subepithelaial basal lamina - provides nutrients and support to epidermal tissue
Deep dermal plexus in dermis
layer of vessels near interface of dermis and subcutaneous layers
AV anastomoses in dermis
- shunts blood between subpapillary and deep dermal plexi
- increased flow to papillary layer to vent heat
- decreased flow to papillary layer to conserve heat
Subcutaneous layer
- hypodermis
- deep to dermis
- loosely anchors skin to underlying muscle
- loose CT
- adipocytes make it fatty
- vascular
Sensory receptors List (6)
- Merkel cells
- Free sensory nerve endings
- Root hair plexus
- Meissner corpuscle
- Lamellated (Pacinian corpuscle)
- Ruffini corpuscle
Merkel cells
- oval epidermal cells
- stratum basal
- associated with somatosensory nerve fiber
- fn as sensory receptor for light sustained touch and texture
Free sensory nerve endings
- papillary and lower dermal layers
- sense pain, temp, itch
Root hair plexus
- sensory web at hair follicle base
- detects hair movement
Meissner Corpuscle
- disks perpendicular to epidermis in dermal papilla
- stacks of flattened Schwann cells
- single afferent nerve attached
- highly sensitive to light touch
- determines two point touch
- abundant on fingertips and lips
- rapidly adapting/phasic: action potential generated and decreased quickly, habituation
Laminated (Pacinian) corpuscles
- among adipose cells in deep dermis and subcutaneous layer
- also in walls of bladder and rectum
- singel afferent nerve at the core of 20-60 concentric lamellae of Schwann cells
- sense vibration and sudden pressure
Ruffini corpuscles
- anchored firmly to CT
- sense torque and twist
List the () types of skin gland
- Sebaceous glands
- Specialized sebaceous glands
- Sweat glands
- Specialized apocrine sweat glands
Sebaceous glands
- acinus gland structure (lots of cells around a duct)
- sebocytes produce sebum
- cells die and disintegrate, sebum is released into duct
- Duct leads to hair or skin surface
- Holocrine secretion
Sebum composition
- TG
- wax esters
- squalene
- FFA
(odorless, bacteria produce odor)
two types of specialized sebaceous glands
- Meibomian glands: tear ducts, sebum mixes with tears
2. Areolar glands: lubrication and protection of nipple
Sweat glands
- aka sudoriferous glands
- epidermal invagination into dermis
- SNS innervation
List the two types of sweat gland
- Eccrine
2. Apocrine
Eccrine sweat glands
- widely distributed (esp on forehead, palms, plantar foot)
- coiled, tubular gland opens to sweat pore
- secretes sweat which is conducted by myoepithelial cells to skin surface
- purpose: evaporative cooling
Sweat formation and composition
- filtrate from blood
- hypotonic
- 99% water with:
- NaCl
- bicarb
- K+
- glucose
- cytokines
- IgA
- dermicidin
Apocrine sweat glands
- coiled gland in dermis with sweat released to hair follicle
- sweat, FA, proteins
- odor dt bacteria
- mostly axillary and anogenital region
- sex hormone control
- granules exocytose (Merocrine release)
List 2 types of specialized apocrine sweat gland
- ceruminous glands
- Mammary gland
ceruminous glands
- subcutaneous layer in outer 1/3 of EAC
- drain into larger ducts, drain into guard hairs in EAC
- produce cerumen (earwax) by mixing with sebum and dead epidermal cells
- keeps eardrum pliable, lubricates, waterproofs
- coats guard hairs, making them sticky
Mammary glands
- milk-secreting cuboidal cells
- surrounded by myoepithelial cells
- join into lobules, ea has lactiferous duct that drains to openings in nipple
- myoepithelial cells contract under oxytocin, excrete the milk
- one complex mammary gland in each breast, each contains 10-20 simple glands
Hair
- describe
- elongated keratin structure
- color is pigment from melanocytes at base of follicle
3 layers of keratin in hair
- cuticle: thin outer scales
- Cortex: inner, thickest layer
- Medulla: core, only in thick scalp hair
What is the hair follicle
the hair producing gland
Describe the anatomy of the hair follicle
- Papilla: base of follicle, CT with capillary tuft
- Hair bulb
- Rooth sheath
Hair bulb
- dilated terminus of follicle during hair growth
- houses the matrix (where hair follicle is produced)
- keratinocytes: mitotic growth through terminal differentiation
- melanocytes: produce melanin which is uptake by keratinocytes
Root sheath
- two layers
(part of follicle extending through dermis and epidermis)
- internal root sheath
- external root sheath
Internal hair root sheath
- epithelial tissue surrounding root to sebaceous gland
- two layers
External hair root sheath
- CT sheath covers internal sheath
- extends all the way through the epidermis
Three stages of hair growth
- Anagen
- Catagen
- Telogen
Anagen phase of hair growth
- 90% of active growth
- 3-4 years on scalp
- 30-4 days on appendages, eyelashes, eyebrows
- begins as progenitor cells form new bulb and matrix
Catagen phase of hair growth
- growth slows
- outer sheath shrinks, attaches to hair shaft forming club hair
Telogen phase of hair growth
- hair bulb shrinks
- club hair is shed
Arrector pili
- controlled by SNS
- smooth muscle fibers at base of hair follicle
- contraction pulls hair vertical, goose bumps
- heat production
Nails
- describe composition
- function
- anatomy
- hard keratin plate from nail bed
- fn: scratching, dexterity, defense
- nail root is beneath epidermal folds
- nail body: visible plate
- free edge: part hangs off finger
- Lunula: moon shape at proximal body
- distal extent of germinal matrix of nail bed
- dense nucleated keratinocytes (opaque)
Nail folds
- lateral
- hyponychium: below free edge
- Eponychium: cuticle, proximal fold over nail body
List four types of lesion
abrasion
laceration
puncture
surgical
Clotting phase of wound healing
- bleeding into wound
- platelets form platelet plug
- clotting factors form cross-linked fibrin mesh
- thrombus (scab)
Inflammatory phase of wound healing
- plasma and leukocytes move from blood to injured tissue
- heat, pain, redness, edema
Proliferative phase of wound healing
- mitotic activity
- granulation: fibroblasts secrete collagen foundation, vascularization creates nutrient supply and waste removal
- epithelialization: epidermal growth from all directions to cover site
Maturation phase of wound healing
- collage reorganization
- granulation tissue dies
- debris removal
- excessive collage remains as scar
Three wound healing categories
- Primary or first intention
- Second intention
- Tertiary intention
Primary intention wound healing
- clean wound, no tissue lost
- closure of wound
- heals from outside in
- can open easily
- infection, abscess formation
Second intention wound healing
- wound heals without closure
- natural process of healing from inside out
- less chance of abscess forming
Tertiary intention wound healing
close wound after all evidence of inflammation has passed
