Integumentary System Flashcards
1
Q
Thick and thin skin
A
Thick skin - Epidermis (thick) - Dermis - Appendages: no hair Thin skin - Epidermis (thin layer) - Dermis - Appendages: hair folicle
2
Q
Functions of integumentary system
A
- Barrier: physical, chemical and biological agents
- Immunologic: antigen processing to the appropriate effector cells in the lymphatic system
- Homeostasis: body temperature and water loss
- Conveys sensory info about the external environment to the nervous system
- Endocrine: secreting hormones, cytokines and growth factors + converting precursor molecules into hormonally active molecules vitamin D
• Excretion: sweat
3
Q
Epidermis
A
- consists of stratified squamous keratinised epithelium
- Several layers (stratum)
- Melanin pigment – colour of skin
4
Q
Dermis
A
- Blood/lymph vessels, appendages, nerves, sensory nerve endings
5
Q
Hypodermis
A
- (not considered part of the skin)
- Layer of subcutaneous loose connective tissue
- Presence of adipose tissue
6
Q
5 epidermis layers
A
- Stratum Corneum; dead keratinized cells
- Stratum Lucidum; (Thick skin only)
- Stratum Granulosum; Cells that are about to die
- Stratum Spinosum; Maturing and slowly dying cells, Keratinocytes produce keratin filaments
- Stratum Basale; Stem cells , capable of differentiation
7
Q
Cells of the epidermis
A
- keratinocytes (aka stratified squamous keratinized epithelium)
- melanocytes
- langerhans
- merkel
- its in a state of dynamic equilibrium in which exfoliated keratinized cells are constantly replaced by a steady flow of terminally differentiated cells
8
Q
Keratinocytes
A
- they account for 85% of the cells in the epidermis.
- Originate in the stratum basale.
- Keratinocytes has two essential activities: produce keratins (cytokeratins) + participate in formation of the epidermal water barrier.
9
Q
Life cycle of epidermis
A
- basal cell layer originate new cells with keratin filaments
- As cells mature, they move upwards.
- In upper part of the spinous layer, the cells begin to produce keratohyalin granules and glycolipid-containing lamellar bodies to form the water barrier
- pH is low enough to digest desmosomal proteins promoting detachment of the most superficial layer of keratinocytes.
10
Q
Epidermal cell differentiation and replacement
A
- Division of stem cells in the stratum basale (1-2 days) - Newly formed cells move upward as they differentiate into keratinized cells. - Keratinized cell are lost by exfoliation on skin surface. - process takes 47 days and is maintained in equilibrium (cell divisions vs cell loss)
11
Q
Psoriasis
A
- Normal epidermal turnover time takes ∼47 days
- In psoriasis the epidermal turnover time is faster, taking approximately 8 to 10 days.
12
Q
Merkel’s cells
A
- Detect touch sensations
- Least numerous
- Most abundant in skin where sensory perception is acute (fingertips)
- Have desmosomes and contain keratin filaments
- Nucleus is lobed
- Cytoplasm contains neurosecretory granules
- Closely associated with the expanded terminal bulb of afferent myelinated nerve fibres = merkel’s corpuscle
13
Q
Melanocytes
A
- Melanocyte to keratinocyte ratio 1:4 to 1:10
- Constant throughout all races
- Skin colour = Amount of melanin present
- Darker skin individuals have slower melanin degradation
- Once produced, melanin granules migrate from melanocytes to keratinocytes
14
Q
Albinism
A
- inability of melanocytes to synthesise melanin
15
Q
Vitiligo
A
- degeneration and disappearance of entire melanocyte
16
Q
Melanoma
A
- Tumour formed by proliferation of melanocytes
- darker colour; Increased number of melanocytes in a small area leads to increased production in melanin in the area
17
Q
Langerhans cells
A
- Originate from Common lymphoid progenitor (CLP)
- Immunological function: encounter, process and express antigens, antigen presenting cells (APCs), migrates to the lymph node to present the antigen to T-lymphocytes
18
Q
Skin - Dermis
A
- below epidermis
- It is the connective tissue that supports the epidermis and bind to the hypodermis
19
Q
What does the dermis contain?
A
- blood/lymph vessels
- appendages
- nerves
- sensory nerve endings
20
Q
Epithelial appendages
A
- All are outgrowths of the epidermis in one way or another
- All extend into the dermis
- Hair follicle and hair
- Nails
- Glands; sebaceous, eccrine (sweat), apocrine (sweat) glands
21
Q
Hair follicle and hair
A
- Invagination of the epithelium that extends into the hypodermis
- Associated with a sebaceous gland and smooth muscle = pilosebaceous organ
- Not found in thick skin
- Bulb contains the matrix cells for hair formation; melanocyte stem cells are found in the bulb, shaft and root
22
Q
Hair
A
- Consists of hard keratin
- Colour is determined by the amount of melanin produced by the melanocytes in the bulb
23
Q
Three layers of hair
A
- Medulla - central part contains large vacuolated cells and only present in thick hairs - Cortex - peripherally to the medulla and contains cuboidal cells undergo differentiation into keratin-filled cells - Cuticle - squamous cells that form the outermost layer
24
Q
Three types of glands in skin
A
- Sebaceous
- Eccrine (sweat)
- Apocrine (sweat) glands
25
Eccrine sweat glands
- distributed over the entire body surface
- they are especially numerous in thick skin of hands and feet
- Evaporation of the secreted sweat on the skin surface cools the body
- Simple coiled tubular glands
- Secretory portion is in the deep dermis
26
Apocrine sweat glands
- localized in the axilla, areolae, perineal and perianal area, prepuce, scrotum, mons pubis, and labia majora
- Coiled tubular glands
- Secretory portion is located in dermis or even hypodermis
- Secretory lumen larger than eccrine sweat glands
- Secrete pheromones
- Ducts are straight and lined by stratified cuboidal epithelium has a narrow lumen
27
Sebaceous glands
- discharge their secretion into the follicle, from where it reaches the skin surface
- sebaceous secretion is rich in lipid.
- Simple branched acinar
- Secretory portion is located in the deeper dermis
- Opens into hair follicle
- Secretion is holocrine
- Product is sebum, clear with H&E staining
- Helps prevent the hairs from becoming dry + brittle
28
What do eccrine glands contain?
- Clear cells - abundant glycogen stains well with PAS
- Dark cells - rER and secretory granules are abundant
- Myoepithelial cells - basal aspect of the secretory
segment
- The duct passes through the dermis and epidermis to
open onto the surface
29
Nails
- Hard plates of epidermal keratinized cells
- Help with grip, gives protection
- Resting on a nailbed; nail matrix, hyponychium
• Grow 1mm/week
30
Skin sensorial receptors
- skin is endowed with sensory receptors of various types that are peripheral terminals of sensory nerves
- also well supplied with motor nerve endings to the blood vessels, arrector pili
muscles, and sweat glands.
31
Free nerve endings
- the endings are “free” in that they lack a connective tissue or Schwann cell investment
32
Merkel's corpuscle
- a dendritic cell for cutaneous sensation, such as the fingertips
33
What do encapsulated nerve endings include?
- Pacinian corpuscles (pressure changes and vibrations)
- Meissner's corpuscles (light touch)
- Ruffini's (stretch and torque) corpuscles
- Krause's end bulb (cold)
