Integumentary system Flashcards
What are the accessory organs of the integumentary system?
Hair
Nails
Cutaneous glands- sweat, sebaceous and mammary
What are the three gross layers from outer to inner?
Epidermis
Dermis
Hypodermis (areola or adipose tissue between skin and muscle)
What are the two zones of the dermis?
Papillary layer
Reticular layer
What is the papillary layer of the dermis?
Thin region of loose connective tissue allowing mobility of leukocytes, mast cells and macrophages
What is the reticular layer of the dermis?
Thick layer of dense irregular tissue, less cells, but often with adipocyte clusters for stretch of skin in weight gain
What are fibroblasts?
Produces proteins laminin and fibronectin of the ECM
What other structures are found in the dermis?
Fibroblasts Accessory organs Rich supply of blood and lymphatic cells Atriovenous enastemoses Numerous nerve endings
What is the structure of the dermal-epidermal boundary?
Wavy boundary of finger like projections
Made of dermal papillae and epidermal ridges
Tall dermal papillae facilitate nerve fibres reaching closer to the surface in areas of high sensitivity
What are the differences between thick and thin skin?
Thick- palms of hands and feet, no hair, 5 layers
Thin- rest of the body and only has 4 layers
What are the layers of the epidermis from the bottom upwards?
Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (only in thick skin) Stratum corneum
What cells in the epidermis retain the ability to replicate?
Only ones that are in contact with the basement membrane
Stratum basale
Keratinocytes most prevalent and are mitotically active on the basement membrane
Contains melanocytes which gives the skin colour
Contains merkel disc sensory receptors
What are the two kinds of melanin produced in the stratum basale?
Pheomelanin- red soluble pigment
Eumelanin- brown insoluble pigment
What is the function of melanocytes?
Release melanin which is UV absorbant, an antioxidant and is radical scavenging which all helps to protect the skin from UV damage
What else does the pigment of the skin depend on other than melanocytes?
Carotene pigments give a yellow/orange colour in subcutanous fat and the stratum corneum
Amount of blood and its oxygen content- haemoglobin gives red colour
Stratum spinosum
Several layers of keratinocytes and is usually the thickest layer (apart from thick skin which is the stratum corneum)
Deepest cells are mitotic and are pushed upwards so they cease to divide
Produce keratin filaments causing cells to flatten
Tight junctions for water retention of skin
What are desmosomes?
Strongly link keratinocytes together in the stratum spinosum
Stratum granulosum
3-5 layers of flat keratinocytes, post-mitotic
Contain dark staining keratohyalin granules which bind to cytoskeleton and are converted to keratin
Cells undergo apoptosis
Produce glycolipid filled vesicles to form a waterproof layer between spinosum
Stratum lucidum
Thin translucent layer which is only present in thick skin
Keratinocytes densely packed with no nuclei or organelles
Indistinct cell boundaries
Granules of eleidin within proteoplasm- product of keratinohyalin
Stratum corneum
Most superficial, 15-20
Terminally differentiated dead keratinocytes that continually flake off
Resistant to abrasion, water loss and penetration
What is the cornified envelope of the stratum corneum made up of?
Keratins enclosed within an insoluble amalgam of proteins
Cross linked by transglutaminases
Surrounded by lipid envelope
Structure of nails
Derivatives of the stratum corneum and composed of dead scaly cells densely packed with hard keratin fibres
New cells are added by mitosis in the nail matrix
How can appearance of the nails indicate underlying health issues?
Iron deficiency- become flat or concave
Long term hypoxemia- become clubbed
Structure of hair
Slender filament of dead keratinised cells from follicles
What are the three stages of hair changing during lifetime?
Lanugo- fine, downy, unpigmented, in the foetus
Vellus- similarly fine and unpigmented
Terminal- coarse, pigmented
What are the three layers of the hair matrix?
Medulla- loosely arranged cells
Cortex- keratinised cuboidal cells
Cuticle- surface layer of scaly cells
How does hair grow?
Hair bulb grows around a bud of vascular connective tissue- dermal papilla
The hair matrix above is mitotically active
What are the 5 different types of glands present in the skin?
Merocrine sweat glands, apocrine sweat glands
Sebaceous glands
Ceruminous glands
Mammary glands
What is the function of merocrine glands?
Watery perspiration to skin
Associated with myoepithelial cells
What is the function of apocrine sweat glands?
Ducts lead to follicles
Scent glands responding to stress and sexual stimulation
What is the function of sebaceous glands?
Produces oily sebum which lubricate skin and hair
What is the function of ceruminous glands?
In the external ear and produces ear wax
How is skin a physical barrier?
Cross linked keratin layer upon a scaffold of keratinocytes
How is skin a biochemical barrier?
Slight acidity of pH 4-6
Bacteriocidal agents- saturated and unsaturated fatty acids inhibit the growth of bacteria and lysozymes cleave the cross linkages in bacterial cell walls
How is the skin an immunological barrier?
Langerhans cells of the stratum spinosum are able to self renew and take up and process antigens
by either migrating to lymph nodes for antigen presentation
or present antigens to the skin lymphocytes which activate an immune response
How does the skin regulate temperature in terms of blood flow?
Countercurrent heat exchange between arterial and venous blood flow in the dermis of extremities
How does the skin regulate temperature using sympathetic fibres?
Postganglionic- release norepinephrine which causes vasoconstriction
Preganglionic- release ACh which causes vasodilation, mediated by formation of bradykinin
Muscarinic ACh receptors for sweat glands
