Skin Flashcards
3 layers of skin and their position beginning with the most superficial
Epidermis
Dermis
Subcutaneous
What are the two types of sweat glands and the difference between them?
Merocrine (acidic secretion) and apocrine (alkaline secretion)
What are Langer’s lines?
Natural lines on skin created by tension
When making incisions, why is it important to cut along the Langer’s lines?
The stitches are less likely to fall out and leave scarring
What is propreiation?
The skin’s ability to know its location in space
In early development, what are the little bumps along the longitudinal axis called?
Somites
What originates from somites?
Nerve supply and muscles in a segmented pattern
What causes the Langer’s lines to no longer be straight?
Limbs extend out and ruin the lines of segmentation
Where do each level of spinal nerves originate from?
Dermatones
What name is given to the disc we originate from?
Tri-laminar disc
What are the three layers of the tri-laminar disc?
Ectoderm
Mesoderm
Endoderm
What originates from the ectoderm?
Skin and nervous tissue
What originates from the mesoderm
Blood, muscles and skeleton
What originates from the endoerm
Gut
How does the tri-laminar disc fold?
Folds into two directions. This creates a cephalo-caudal structure
What does folding create?
Creates spaces/cavities within the membrane
What lines the membranes of the cavities and what does this allow?
Serous liquid and this allows for movement and distension
Where would you find pleural cavities?
The lungs
Where would you find pericardial cavities?
The heart
Where would you find abdomino-pelvic cavities?
The gastro-intestinal and reproductive tracts
Where would you find cranial cavities?
The brain
What happens to the spaces within the body during development?
The space is filled by an organ. The organ pushes the two layers together creating a visceral layer beside the organ and a parietal layer against the wall of the cavity
What are fascial spaces?
Fasicial spaces are casued by the fascia layers separating muscles into compartments
What is adipose tissue composed of?
White and brown fat
What is the function of white fat cells?
Energy storage, insulation, protection
What is the function of brown fat cells?
Heat production
What can white fat stores do?
Produce adipokines that send signals to regulate nutritional balance
What produces leptin?
White fat cells
What does leptin do?
Sends signal to the brain that it has had enough to eat
How does brown fat create heat?
Uncoupling oxidative phosphorylation in mitochondria
What are the functions of skin?
1- Protective barrier: enclose and shelter an internal environment 2- Metabolic 3- Temperature regulaiton 4- Internal homeostasis 5- Sensation 6- Psycho-social signals
What are the three layers of skin?
1- Epidermis
2- Dermis
3- Hypodermis
Describe the epidermis.
1- Avascular epithelium
2- Undergoes proliferation
3- Synthesises keratin
Describe the dermis.
1- Vascular 2- Tough, leather-like 3- Contains blood vessels 4- Contains lymphatics 5- Contains cutaneous nerves 6- Collagen and elastic fibres are not replaced with age
Describe the hypodermis.
1- Superficial fascia 2- Varies in thickness 3- Contains blood vessels 4- Contains nerves 5- Contains lymphatics 6- Contains adipose tissue 7- Skin ligaments, loose skin or taut skin are implied in scarring and incisions
How do burns affect skin?
1- Leads to loss of skin’s function as a barrier
2- Fluid loss
3- May lead to infection
What type of epithelium is found in the epidermis?
Stratified squamous keratinised epithelium (thick skin e.g. palms)
What are five layers of the epidermis?
1- S. Corneum 2- S. Lucidum 3- S. Granulosum 4- S. Spinosum 5- S. Basale
Describe the S. Corneum layer.
Water proof cell ghosts
Describe the S. Lucidum layer.
1- Specialised cell death program
2- Only present in thick skin
Describe the S. Granulosum layer.
Keratohyaline granules promote cell dehydration and aggregation of keratin
Describe the S. Spinosum layer.
1- Intermediate filaments keratin-1 and keratin-10 expressed
2- Keratin linked to eachother via desmosomes
3- Basal cells linked with basement membrane via hemidesmosomes
Describe the S. Basale layer.
Stem cells attached to the basement membrane by hemidesmosomes
How is the epidermis attached to the dermis?
Collagen VII
What happens when the gene expressing collagen VII undergoes mutation?
1- Dystrophic epidermolysis bullosa
2- Weak links between epidermis and dermis
3- Weak/fragile and blistering skin
What is cornification?
The production of corneocytes (dead cells) which act as a protective barrier for the skin
What is filaggrin found?
Filaggrin is a main component of keratohyaline granules in the S. granulosum
What is profilaggrin?
Precursor to filaggrin
What are the roles of filaggrin?
1- Maintain optimal skin barrier
2- Aid keratin filament aggregation
3- Inhibit water loss
How does filaggrin inhibit water loss?
It is cleaved into amino acids, which aids in maintaining moisture
What is the most common cause of keratinization disorders?
Mutation of filaggrin
What can the mutation of filaggrin lead to?
1- Keratinization disorders e.g. itchyosis vulgaris
2- May also be implied in ~50% of eczema case
3- Null mutations may also be associated with asthma
Where are melanocytes found?
Basal layer of the epidermis
What do melanocytes synthesise and release?
Melanin, a brown pigment
What is the function of melanin?
1- Absorbs UV-B
2- Prevents DNA damage to underlying cells of the hypodermis
3- Increased levels lead to lower incidence of skin cancer
4- Synthesised and released by melanocytes
What is melanoma?
Tumour of melanocytes
What is the cause of melanoma?
Exposure of melanocytes to UV radiation
Where are melanocytes derived from?
Crest cells that originate near the developing nervous system and spread into the embryo which become mesodermal in nature
What are Langerhans cells?
1- Macrophage-like cells
2- Dendritic in form
3- Derived from monocytes
4- Mostly found in S. spinosum layer
5- Antigen-presenting
6- Activated in skin but later on migrate to lymph nodes
7- Express Langerin, which helps degrade viruses such as HIV in speciailised endosomes called Birbeck granules
Where are Langerhans cells usually found?
1- S. spinosum
2- Activated in skin but later on migrate to lymph nodes
What do Langerhans cells express?
Langerin
What is the role of Langerin?
Help degrade virsuses such as HIV by binding to the virus and internalising them in endosomes called Birbeck granules for degradation
What is the dermo-epidermal junction?
1- Tissue which joins epidermis to dermis
2- Prevents shearing
What are the two layers of the dermis?
1- Papillary dermis
2- Reticular dermis
What does the papillary dermis layer comprise of?
1- Fine collagen and elastic fibres
2- Small blood vessels and nerves
What does the reticular dermis comprise of?
1- Coarser collagen and elastic fibres
2- Larger blood vessels and nerves
What does the hypodermis consist of?
1- Loose connective tissue 2- Adipose tissue 3- Superficial blood vessels and lymphatics 4- Cutaneous nerves 5- Skin ligaments
What tissue is responsible for vitamin D production?
Hypodermis
What determines the mobility of skin implicated in scarring and incisions?
Skin ligaments in the hypodermis
What are sweat glands?
1- Eccrine and apocrine
2- Secrete sweat, watery fluid
3- Secretory portion lies in the dermis and superficial fascia
4- Controlled by sympathetic nervous system
What is the function of eccrine sweat glands?
1- Thermoregulation
2- Respond in fight or flight
What is the function of apocrine sweat glands?
1- Secrete pheromones
Where are apocrine sweat glands found?
In the axillae (arm pits) and genital region
Describe the structure of hair follicles.
1- Cylindrical, epithelial structures 2- Anchored in the hypodermis 3- Hair shaft grows from the bulb 4- Hair shaft made of keratin 5- Associated with sebaceous glands
What are sebaceous glands?
1- Glands associated with hair follicle
2- Secrete sebum to lubricate hair and adjacent skin
What are arrector pili?
1- Smooth muscle attached to papillary dermis and sheath of the follicle
2- When it contracts, they pull the hair upright leading to goose bumps
3- Controlled by sympathetic nervous system
What are the three parts of a pilosebaceous unit?
1- Sebaceous gland
2- Hair follicle
3- Arrector pili
What are mammary glands?
1- Modified apocrine sweat glands
2- Lactate under hormonal control
What are nails?
1- Nail plate formed from keratin
2- Rests on nail bed
3- Grows from nail root which passes deep into the dermis
What is the periodontal membrane?
Fibrous joint between the teeth and skull
What receptors sense pain?
Nociceptors
What receptors sense touch?
1- Meissner’s corpuscles
2- Fine touche Merkel cells
What receptors sense pressure?
Pacinian corpuscles
What receptors sense vibration?
1- Meissner’s corpuscles
2- Pacinian corpuscles
