WEEK 2 - Integumentary System Flashcards
functions of skin
- protection: acts as a barrier to the outside world
- body temperature regulation: insensible (can’t sense it but is happening constantly ) and sensible (high increase in body temp)
- cutaneous sensations: exteroceptors (exposed to the external environment), free nerve endings
- blood reservoir: constriction of skin vessels (fight)
flight: vasoconstriction of skin vessels - excretion of waste
structure of the skin
consists of two layers:
1. epidermis: avascular (no blood vessels)
2. dermis: type of connective tissue with capillaries and free nerve endings
*3. hypodermis: not technically a skin layer
epidermal layers (from the bottom to top)
stratum basale: deepest epidermal layer (attaches to the dermis), one row of actively mitotic stem cells, some newly formed cells become part of the more superficial layers
which of the following epidermal layers contain merckel cells? this one!
other cells:
- keratinocytes
- melanocytes: containing melanin and protects from UV
- tactile epithelial cells/merckel cells: sensory perception
stratum spinosum
- several layers of keratinocytes unified by desmosomes
- cells contain thick bundles of intermediate filaments made up of keratin
- dendritic cells aka macrophage so eats debris
stratum granulosum
- 1 to 5 layers of flattened cells with organelles deteriorating (since its far from dermis/blood vessels
- keratinization begins (cytoplasm is getting packaged): cytoplasm full of keratohyalin granules, lipids, filaggrin: filament aggregating protein
status lucidum
- high wear and tear (hands and feet)
stratum corneum
- most superficial layer
- 20 to 30 of dead cells (keratinocytes), flat membranous sacs filled with keratin, lost their nucleus
- glycolipids in extracellular space and are water resistant
keratinocytes
1. adhesion of the epidermis by their cytoskeleton and junctions (desmosomes)
2. a barrier between the external environment and the internal environment at the level of stratum corneum (impermeability)
3. protect from UV radiation: they phagocytose melanosomes that contain melanin, from melanocytes
3 physiological consequences of disrupting these functions
- epidermolysis bullosa simplex/butterfly disease
- ichthyosis vulgaris
- albinism
- epidermolysis bullosa simplex/butterfly disease
- localized EBS: occurs on the hands and feet
- intermediate EBS: widespread, occurs on the arms and legs
- severe EBS: includes mouth
interstitial fluid from broken cells contains plasma and provides nutrients and prevents infection
- affects how well the desmosomes hold together and the skin becomes fragile, easily damaged
the affected genes for ALL include KRT5 and KRT14
- ichthyosis vulgaris
fish-like impermeability = improper forming of stratum corneum
- mutation in filaggrin protein
in normal cases, the keratohyalin granules contains the filaggrin which aggregates the keratin and the cells flatten
in abnormal cases: the mutation prevents aggregation so there’s no stratum corneum = no shedding
- the cells in the basal layer are still dividing and being pushed up and cells in the stratum granulosum cannot become cells in stratum corneum
albinism
- disruption in melanin production
- number of melanocytes in individuals doesn’t vary, the differences in skin color reflect the amount and kind of melanin made
melanogenesis
stage 1: contains tyrosine
stage 2: fibrillar matrix acquires inactive tyrosine and fuses with stage 1
stage 3: melanin cell and contains active tyrosinase and tyrosine and it is where the skin color differs
stage 4: melanin cell now contains mature melanosomes and are exocytosed by melanocytes and endocytose by keratinocytes
- melanosomes surround the nucleus and absorb UV radiation
- a mutation in tyrosinase causes the blockage of stage 3 which means no melanin = no color and increased rates of skin cancer
structure of the skin
the dermis consists of 2 layers:
1. top layer: sends projections up into the epidermis, contains capillary loops, free nerve endings, touch receptors
- bottom layer: appendages of the skin, fibroblasts (ECM), macrophages, mechanoreceptors (pressure vibrations)
appendages of the skin
- hair:
- hair bulb contains melanocytes and keratinocytes
- hair bulge contains stem cells
effects of aging on hair color:
- less stem cells
- reactive oxygen species (less ability to remove ROS), reverse by increasing enzymes that block ROS
- nails: have stem cells
cutaneous glands
eccrine sweat glands
- secretes to the surface
- temperature control and antibacterial properties (dermicidin)
- secretes hypotonic filtrate of blood plasma
- located everywhere but especially palms soles and forehead
apocrine sweat glands
- secretes into the hair follicle
- may act as sexual scent glands (pheromones)
- secretes filtrate of blood plasma with added proteins and fatty substances
- located mostly in the axillary and anogenital regions
sebaceous sweat glands
- secretes into the hair follicles
- lubricates skin and hair, prevents water loss, some antibacterial properties
- secretes sebum
- located everywhere except palms and soles
