Cutaneous Membrane Flashcards
What is the integumentary system composed of?
Cutaneous membrane (epidermis and dermis) and accessory structures (, hair follicles, nails, exocrine glands)
What is the cutaneous membrane composed of?
Epidermis and dermis make up the two layers of the skin
What is the subcutaneous membrane?
Hypodermis; composed of loose connective tissue (not part of the integument but tissue fibres are interwoven with those of the dermis)
What is the integument?
Epidermis + Dermis + Accessory structures
What are the functions of the skin and hypodermis? (8)
1) Protection: from impact, abrasion, fluid loss, chemicals
2) Excretion: of salts, water, organic wastes
3) Regulation of body temperature
4) Synthesis of vitamin D3: a steroid that is converted into calcitriol hormone required for Ca2+ absorption from the intestine
5) Storage of lipids: in adipocytes
6) Sensation: innervated tactile receptors sensitive to different levels of touch and vibration
7) Production of melanin: protects cells from UV
8) Production of keratin: protects from dehydration
What is the composition of the epidermis?
Stratified squamous epithelium which are avascular; superficial surface cells are inert/dead
What are the characteristics of the epidermis?
(main cell type, nature of cell junctions)
Main cell type: keratinocytes
Nature of cell junctions: hemidesmosomes to basal lamina
What is the origin and fate of keratinocytes in the epidermis?
Newly formed cells at the bottom are pushed further towards the surface of the cell and are eventually shed (die)
What is the dermal papillae?
Dermal papillae are upward extensions of the dermis layer of the skin. The strength of attachment is proportional to the surface area
- named for its fingerlike projections called papillae
- little humps
They have two main functions: to help adhesion between the dermal and epidermal layers, and to provide a large surface area to nourish the epidermal layer
What are the layers of the epidermis?
2 types of skin; thin or thick
Thin = 4 layers of keratinocytes
Thick = 5 layers of keratinocytes
What are the (5) layers of skin in thick skin?
Stratum Corneum (thickest; 20-30 layers)
Stratum Lucidum (palms and soles only)
Stratum Granulosum
Stratum Spinosum
Stratum Germinativum/Basale
What are the (4) layers of the skin in thin skin?
Stratum Corneum (thickest; outermost; 25-30 layers dead skin)
Stratum Granulosum
Stratum Spinosum
Stratum Germinativum/Basale
What layer of skin is present in only thick skin?
Stratum Lucidum
What contributes to the colour of skin?
Epidermis contains melanin which gives skin its colour and allows skin to tan
Carotene and oxygen-rich hemoglobin also contribute to the colour of skin
What stiffens epidermal tissue to form fingernails?
Protein keratin
Order the layers of the epidermis; deep to superficial
1) Stratum germinativum/basale- Deepest
2) Stratum spinosum
3) Stratum granulosum
4) Stratum lucidum
5) Stratum corneum - Surface
What is the stratum germinativum/basale
- anchored to basal lamina by hemidesmosomes
- forms epidermal ridges which interlock with dermal papillae
- simple cuboidal/columnar epithelium (keratinocytes)
- provides strong attachment
Why do you get calluses and what are they?
Pressure, wear and tear stimulates more rapid mitosis, which leads to thickening of the epidermis as a protective mechanism
Why do you get blisters and what are they?
Friction or damage to the epidermis from extreme temperatures or chemicals cause layers of the epidermis to separate and the gaps fill with fluid from underlying tissue (clear, blood, or pus if infected)
The fluid stimulates healing and regrowth
What is the purpose of ridges in the skin?
Ensures good grip of fingers and toes; creates fingerprint ridge pattern uniqueness
- genetics + in utero development
Would identical twins have the same finger prints?
NO :3
- different level of hormones, growth factors
Why do you get prune-y fingers in the bath?
Nervous system triggers blood vessel constriction
What cell types are present in the stratum germinativum?
a) basal cells = germinative cells (stem cells)
b) melanocytes = pigment producing cells
c) merkel cells = sensitive to touch, activate nerve endings by releasing chemicals
Provides protection for DNA from the sun
What is the stratum spinosum?
spiny layer; 8-10 layers of keratinocytes joined by desmosomes
includes langerhans (dendritic) cells (phagocytes)
defends against microorganisms and superficial skin cancer
What is the stratum granulosum?
Grainy layer; 3-5 layers of keratinocytes which accumulate in granules, promoted dehydration, and cross links between keratin fibres
as cells move upwards through the stratum granulosum, they become thinner, flatter, and less permeable, creating a tightly interlocked layer of cells. Cells begin to die at this layer
What are keratinocytes
cells that produce large amounts of protein keratin
What is insensible water loss?
Water loss directly through the skin (not the sweat glands); evaporation through skin and respiration
500mL/day
What are melanosomes?
Melanin packaged into vesicles
melanosomes passed to keratinocytes
What are cells superficial to the stratum corneum?
Dead
What is melanin?
A yellow/brown pigment made from tyrosine amino acid; a biochemical, not amino acid
produced by melanocytes in the stratum germinativum
What is the stratum corneum?
Horny layer; 15-30 layers of keratinized, dead cells tightly interconnected by desmosomes
water resistant; insensible water loss
What is the stratum lucidum?
Clear layer; present only in thick skin
cells are densely packed with keratin and devoid of organelles
What are the pigments of epithelium?
Carotene and melanin
What is sensible water loss?
Sweating through the sweat glands
What is carotene?
An orange/yellow pigment (also found in orange vegetables; can be converted to vitamin A)
humans cannot produce carotene
fat soluble; located in fat cells
What is vitiligo?
Vitiligo results from loss of melanocytes, causing white patches on the skin
causes are unknown but may result from autoimmune diseases, genetic factors, or other factors
How does the number of melanocytes differ in people of different skin colours?
Everyone has approximately the same amount of melanocytes; melanosomes is what impacts skin colour
Melanosomes in people with light skin
Breakdown of melanosomes occurs in the strata germinativum and spinosum by fusion with lysosomes
Melanosomes in people with darker skin
Breakdown of melanosomes in the stratum granulosum
melanosomes are more numerous and larger in size
What effect does UV have on skin?
Damage to DNA in stratum germinativum
What influences skin colour?
Number and size of melanosomes, dermal circulation
What is dermal circulation?
Influences skin colour;
a) oxygenates hemoglobin - bright red
-noticeable in light skinned individuals, especially when exercising or flushed (capillaries are dilated)
b) if cold temp. - skin capillaries constrict, making you look paler
- capillary constriction also occurs if blood flow is damaged/restricted
c) low oxygen - deoxygenated hemoglobin - appears dark red and through pale skin
-blue is called cyanosis
What is cholecalciferol?
Vitamin D3; required for normal absorption of Ca++ from digestive tract
Vitamin D3 is produced by epithelial cells in the stratum spinosum and stratum germinativum in response to sunlight
the liver converts the vitamin into a product that the kidneys turn into calcitriol
What causes ricketts?
Caused by a deficiency in Vitamin D3, resulting in the bending of abnormally weak and flexible bones under the weight of the body
What are vitamins?
Essential organic nutrient
Sources of vitamin D3?
** refer to diagram pg. 30
a) Sunlight: In response to sunlight, epithelial cells in the epidermis produce cholecalciferol, which then is converted in the liver to an intermediary product, which is then converted to calcitriol in the kidney.
Calcitriol stimulates calcium and phosphate ion absorption in the digestive tract
b) Dietary Sources: the body intakes VD3 consumption of dietary sources of VD3, which is then converted in the liver to an intermediary product, and then converted to calcitriol in the kidney.
Calcitriol stimulates calcium and phosphate ion absorption in the digestive tract (intestine)
What is the composition of the dermis?
2 layers; papillary layer and reticular layer of the dermis
What is the papillary layer of the dermis?
Areolar tissue
-thrown into folds on the surface = dermal papillae
-contains capillaries, lymphatics, and sensory neurons that supply the surface of the skin
What is the reticular layer of the dermis?
Dense irregular connective tissue; interwoven meshwork of both collagen and elastin fibres. Contains reticular fibres
also contains:
-hair follicles
-sweat glands
-lymphatic vessels
-nerve fibres
Dermal strength and elasticity: collagen, elastic fibres, water content of skin?
Collagen - very strong, resists stretching
Elastic fibres - stretchy
Water content of skin = skin turgor = stretchy
What are the lines of cleavage?
Collagen and elastin fibres in the dermis that are arranged in parallel bundles
-strategically line up
-bundles oriented to resist forces normally applied to skin
-establishes lines of cleavage (a line of cleavage will usually remain close and heal with little scratching; whereas severed elastic fibres recoil creating greater scarring)
Explain the healing of incisions made along vs perpendicular to tension lines
Incisions made along tension lines (following tension lines) heal faster and with less scarring
Incisions made perpendicular (going against tension lines) heal more slowly and tend to scar
Describe dermal blood supply
Dermis is well supplied with blood vessels; has a network of arteries and veins between the dermis and epidermis known as the cutaneous plexuses
these feed into subpapillary plexuses that supply capillaries extending into papillae = source of O2 and nutrients for epidermis
Why are the elderly more susceptible to bruising?
They have more fragile capillaries, and bruises are essentially the result of capillaries bursting beneath the skin
Describe innervation to the skin
Nerve cells regulate: blood flow, adjust gland secretion rates, and monitor sensory receptors
Sensory receptors respond to: light touch, deep pressure, vibration, chemicals, temperature, and pain/damage
