MTM WK4 - DERMIS/EPIDERMIS Flashcards
LAYERS OF SKIN
- epidermis (apendages are nails, hair, sweat glands)
- dermis (angulations (bends) in bottom of epidermis stick to dermis to anchor it (Dermal-epidermal junction)
(papillary layer on top then reticular) - hypodermis (has adipose tissue & larger vessels which supply & drain dermal blood vasculature)
JOBS OF SKIN (3 jobs)
- thermoregulation (sweat)
- protect against external threats (mechanical, water loss, biological, UV light)
- resist bacteria/fungal invasion as have langerhan cells (antigen-presenting) to do immune response
INNERVATION OF SKIN (efferent & afferent)
EFFERENT NERVE SUPPLY - non-myelinated fibres from sympathetic part of autonomic nervous system
AFFERENT NERVE SUPPLY - transmits impulses from sensory nerve endings to CNS (free nerve endings needed for pain sensation & detecting temp)
BLISTER
friction leads to epidermis & dermis separating so fluid accumulates & blister forms
KERATINOCYTES
- synthesise keratin (used to strengthen epidermis)
- start in basal layer then move up to form prickle cell layer & do terminal differentiation & lose nucleus & die to form dead, protective, waterproofing keratin layer (become corneocytes as we get to top & die)
LAYERS OF EPIDERMIS (superficial to deep)
- STRATUM CORNEUM (dead keratinocytes/corneocytes)(horny layer)
- STRATUM LUCIDUM (only exists in thick skin layers)
- GRANULAR LAYER (stratum granulosum)(keratohyalin granules (strength) & enzymes which degrade bi-layer)
- PRICKLE CELL LAYER (stratum spinosum)(has langerhans cells)
- STRATUM BASALE (has melanocytes) (has merkel cells) (cells here change)
PRICKLE CELL LAYER (spinosum) keratin doings
keratin (from keratinocytes) accumulates within each spinous cell (keratin passed between adjacent cells upwards (as spinous cells full) at desmosome junctions)
HOW MELANOCYTES WORK
produce melanin & have dendrites throughout layer which are phagocytosed to spew out melanin
MERKEL CELLS
mechanoreceptors for touch sensation in dermal/epidermal junction (basal layer)
PSORIASIS
- abnormal growth & differentiation of keratinocytes
- appears as excessive scaling of skin
ALLERGIC CONTACT DERMATITIS
due to epidermal Langerhans cells & T-lymphocytes
MALIGNANT MELANOMA
- malignant tumour of melanocytes
- if tumour cells above basal membrane it is good but otherwise is worrying
VITILIGO
autoimmune disease on melanocytes
PILOSEBACEOUS UNIT
- has hair sheath (outskirt) & hair shaft & sebaceous gland (secretes oils of skin into hair shaft) & arrector pilli muscle to keep up hair
ECCRINE SWEAT GLANDS
release sweat directly into skin surface (is mostly water w some nutrients)
APOCRINE SWEAT GLANDS
release sweat into hair follicles (apocrine secretion which is digested by microbes to form body odour)
VASCULATION OF SKIN
smaller blood vessels (e.g. capillary) in epidermis lniked to larger blood vessels in dermis by interconnecting vessels
FIRST DEGREE BURN
epidermal damage only (red but no blister)
SECOND DEGREE BURN
- SUPERIOR PARTIAL THICKNESS (all the way through epidermis & touches top of dermis (papillary layer))(red blistered)
- DEEP PARTIAL THICKNESS (into upper dermis (reticular layer))(yellow/white)
THIRD DEGREE BURN
all the way through dermis (white/brown but painless as all way through dermis)
REVERSE TRANSCRIPTASE
converts RNA to DNA
WHY RNA LESS STABLE THAN DNA
RNA has -OH group at carbon 1 but DNA only has H (de-oxy) & the RNA can be attacked by water due to having that -OH)
DNA REPLICATION style
semi conservative (each daughter has one old & one new strand)
DNA polarity
enzymes bind from 5-prime to 3-prime (uni-directional)
dNTP’s
building blocks for DN synthesis (if adenine = dATP, cytosine = dCTP)
DNA SYNTHESIS
- 5-prime to 3-prime
- complementary base binds to first base & DNA polymerase binds next complementary dNTP but loses 2 phosphates doing it
REPLICATION FORK
DNA polymerase bonds from 3-prime to 5-prime in the 5-prime strand (leading) BUT in lagging strand, there would be a gap behind where DNA polymerase starts so DNA polymerase enzymes bind in multiple sites to form okazaki fragments (joined by DNA ligase)
HOW DNA POLYMERASE PROOF READS
DNA polymerase adds a base (dNTP), moves back to check it & removes it if it is wrong then moves on
DNA TRANSLATION
ribosome comes in on mRNA & has 2 binding sites (P-site & A-site). First brings tRNA molecule (held in P-site) complementary to first codon & then tRNA complementary to next codon (tRNA in A-site)
TRANSCRIPTOME
complete set of RNA transcripts (varies from cell to cell)
TELOMERES
- PROS - allow replication all the way to tip of chromosome
- CONS - long tracts of repeats can be unstable which leads to deletions immediately below telomeres
- side of chromosome & there are repeat sequences here to protect chromosome)
CENTROMERES
used for segregation during cell division
MINI SATELLITES
no purpose but can cause mispairing in cell division to give duplication/deletion between homologous chromosomes
CHROMATIN
used in DNA packaging (DNA wraps around chromatin & chromatin fibres packed into nucleosome)
- HETEROCHROMATIN (inaccessible as in nucleus)
- EUCHROMATIN (accessible and can be activated or inactivated for transcription)
MITOSIS
- P - chromosomes condense & spindle fibres are formed
- M - nuclear membrane broken down, spindle fibres to equator, tension on kinetochores at centromere facing opp. directions
- A - kinetochore microtubules disappear & chromosomes go to opp. poles
- T - nuclear membrane reforms around chromosomes & RNA synthesis begins
- C - cytoplasm divides to 2 daughter cells
INDEPENDENT ASSORTMENT
mix of maternal & paternal chromosomes = genetic variation
CROSSING OVER
- homologous pair of paternal chromosomes duplicate & cross over (recombine) to give mix of chromosomes (genetic variation)
- cross over at chiasmata
CHIASMATA
hold chromosomes together & is when DNA exchanged between homologous chromosomes
EGG
each month, one egg ovulated & meiosis 1 forms polar body (useless) & another cell that is cytoplasm which divides in meiosis 2 to form zygote (whole cytoplasm) & 2nd polar body
MEIOSIS USES
used for reduction division (23 not 46) and to get re-assortment of genes (independent segregation & crossing over)
MEIOSIS STEPS
- MEIOTIC METAPHASE 1 (each of 2 copies of chromosome has kinetochore joined to it so goes to centre)
- MEIOTIC ANAPHASE 1 - arms of sister chromatids unglued & leads to mix of maternal & paternal & go to side
- MEIOTIC META/ANA 2 - diploid to haploid
