Chap4: Body Membranes And Skin Flashcards
Epithelial membranes subdivisions?
- cutaneous membrane
- mucous membrane
- serous membrane
Characteristics of body membrane
- cover and line body surfaces
- protect body cavities
- lubricate body cavities
Cutaneous membrane
Dry membrane
Outermost protective membrane –> skin
Divided into 2 diff regions:
- superficial epidermis (keratinized stratified squamous ep)
- underlying dermis (mostly dense conn)
Mucous membrane
Line body cavities that open to the outside
Adapted for absorption or secretion (digestive , respiratory, excretory, reproductive tracts)
Serous membrane
Line body cavities that do not open directly to the outside + cover these organs
Covered by thin layer of serous fluid (secreted by ep) + used for protection (cushion)
Special names according to location :
- peritoneum (abdominal cavities)
- pleura (lungs cavities)
- pericardium (around the heart)
Connective tissue membrane?
Synovial membrane : lines fibrous capsules surrounding joints
Integumentary system definition and constituents
Def: helps the body maintain a constant state of balanced internal conditions (homeostasis)
Const: skin, hair, nails, glands ( sweat or oily)
Dermis constituents
Blood vessels
Receptors
Glands
Receptors in dermis
Types of receptors:
- thermoreceptors
- meissners corpuscle (touch)
- nociceptor (pain)
- pacinian corpuscle (pressure)
Fct:
Work with other tissues to detect change in environment
Glands in dermis
Enable body to maintain homeostasis (remove waste)
Help ensure body’s temperature remains the same
Sweat glands : emit moisture on skin surface + removes waste
Oil glands / Sebaceous glands : secrete lubricating liquid at base of hair follicle (activated during puberty)
Skin function
Protection (from ext env)
- mechanical damage (keratinized cells)
- chemical damage (melanin’s uv protection+skin secretions)
- bacterial damage (macrophage of dermis + DNA
- thermal damage
- uv radiation
- desiccation (water loss)
Vitamin D synthesis
Aids in thermal regulation (sweat glands + hair)
Aids in excretion of urea and uric acid
Sensory receptors (nerves that receive msg)
Fct of blood vessels in dermis
Provide dermis with blood
Enable the skin to grow and heal itself
Skin structure
Epidermis
Dermis
Subcutaneous / hypodermis
Epidermis definition
Outer thin layer of skin
Stratified squamous epithelium
Often keratinized
Keratin = fibrous protein that protects epidermis + connected by desmosomes
Arise from stratum basale and die along the way to surface
Layers of epidermis
Stratum basale
-next to dermis
-cells undergo mitosis
-melanocytes (cells containing melanin)
Melanin= pigment that varies between yellow, brown and black
Amount of melanin produced depends on sun exposure or genes
Stratum spinosum
- 8 to 10 layers of keratinized cells connected by desmosomes
- cells phagocytose melanin progressively
Stratum granulosum
3 to 5 layers of cells connected by desmosomes
Stratum lucidum
ONLY IN THICK SKIN ( Palm of hands, feet, tip of fingertips)
2 to 3 layers of clear flat dead keratinocytes
(Cells start to detach and lose desmosomes)
Stratum corneum
Dead cells that protect the skin from water loss and gain
Dermis definition
Region of connective tissue –> contain elastin + collagen
Contain sensory nerves
Dermis layers
Papillary layer (upper)
- pain receptors
- capillary loops (from blood vessels)
Reticular layer (lower + bigger)
- blood vessels
- glands
- nerve receptors
Hypodermis definition
NOT PART OF THE SKIN
Deep to dermis
Anchors skin to underpaying organs
Composed mostly of adipose tissue
Normal skin color determinants
Melanin
- yellow, brown, black pigments
- in deepest layer of epidermis
- accumulate on keratinocyte nucleus forming shield that protects from uv
Carotene
-orange-yellow pigment from som vegetables
Hemoglobin
- red coloring from blood cells in dermis capillaries
- O2 content determines extent of coloring
Appendages of skin
Sebaceous glands
Sweat glands
Hair
Nail
Sebaceous glands
Produce oil : Sebum -slows H2O loss -lubricant for skin and hair -kills bacteria
Connected to hair follicle
Activated during puberty
Sweat glands
Widely distributed in skin
2 types
Eccrine : directly opens to pore on skin surface + abundant in thick skin
Apocrine : opens into hair follicle pore + less numerous than eccrine (secretion: water, salts, proteins, FA)
Sweat and its function
Composition
Mostly H2O + some metabolic waste (+ FA and proteins in apocrine ONLY)
Function
Helps dissipate excess of heat
Excrete waste products
Acidic nature inhibits bacteria growth
Odor is from associated bacteria
Hair definition
Def: flexible strands produced by hair follicle + consist of keratinized cells
Main regions: root -> shaft
Layers of keratinized cells (inner to outer)
Medulla -> cortex -> cuticle
Hair pigments made by melanocytes at root
Structure of hair follicle
From epidermis to deep in the dermis ( sometimes into hypodermis)
Deep end of hair follicle expanded -> hair bulb
Which is surrounded by sensory nerve endings called : hair follicle receptor / root hair plexus
+ presence of papilla : supply nutrients to cells of hair bulb
Around hair follicle (on walls) : outer connective tissue root sheath -> glossy membrane (basement membrane) -> inner epithelial root sheath
Association with bundle of smooth muscle cells called arrector pili muscle (goose bumps)
Nail
Def: scale like modification of epidermis -> form clear protective covering
Made up of hard keratin (C sulfur) + lack of pigments
Free edge of nail -> body of nail -> proximal nail fold
Skin cancer
Basal cell carcinoma
- least malignant
- most common type of skin cancer
- arise from stratum basale
Squamous cell carcinoma
- rapid growth + metastasizes to lymph nodes (ganglion of lymph. syst) if not removed early (early removal -> gd chance of cure)
- arise from stratum spinosum
Melanoma
- most dangerous bcs highly metastatic + resistant to chemotherapy
- cancer of melanocytes
- metastasizes rapidly to lymph and blood vessels
- detection by ABCDE rule
ABCDE rule
Asymmetry : 2 sides of mole don't match Borders : irregular Color : variated Diameter : >6mm Evolving over time
Most dangerous form of melanoma : nodules melanoma has its own classification
Elevated above skin surface
Firm to the touch
Growing
Burns
Def: tissue damage inflicted by intense heat, electricity, radiation or chemicals
-> denature cell proteins + cause cell death
Most immediate threat :
- dehydration
- electrolyte imbalance due to fluid loss
After 24hrs: threat becomes infection to the wound site
Classification of burns
First degree: damage only to epidermis
Second degree: injure epidermis + upper region of dermis
Third degree: entire thickness of skin
Critical if
- over 25% of body has 2ndary
- over 10% of body has 3rd
Rules of nines:
- way to determine the extend of burns
- body divided into 11 areas
- each area approx. 9%
Developmental aspects of integumentary system
During embryonic formation:
- ectoderm -> epidermis
- mesoderm -> dermis + hypodermis
End of 4th month:
-dev of skin well formed
During infancy and childhood:
- skin thickens
- more subcutaneous fat is deposited
During adolescence:
-sebaceous glands are activated -> skin + hair becomes oilier
20s and 30s:
-skin reaches optimal appearance
After that skin starts to show the effects of cumulative env exposures
Old age:
- rate of epidermal cell replacement slows
- skin thins
- lose collagen + fibers in dermis -> lose skin elasticity
- skin more easily damaged (more prone to bruising and injuries)
How skin changes at old age
Skin more easily damaged
Epidermis thins
Amount of collagen in dermis decreases (peptide chain weakened)
Skin infections are more likely + repair of skin occurs more slowly
Decrease in # of elastic fibers in dermis + loss of far from hypodermis
-> skin sags and wrinkles
Activity of sebaceous gland decreases
-> skin becomes drier
+ decrease in blood supply to dermis
–> poor ability to regulate body temp
Number of functioning melanocytes decreases
BUT in some areas (ex hands and face) melanocyte number increase
-> age spots
(Diff from freckles = increase in melanin production not in melanocyte number)
Decrease in or lack of melanin production
-> white or gray hair
! Skin more exposed to sunlight ages more rapidly (hands or face)
