disorders of growth and differentaition Flashcards
what is multiplicative growth?
what is auxetic growth?
what is accretionary growth?
what is combined patterned of growth?
what is differentiation?
- muliplicative growth, cells multiply to give identical daughter cells
- auxetic growth, cells just increase in size rather than number
- accretionary growth, cells increase the extracellular matrix rather than the cells themselves
- combined pattern of growth, these above types^ of growth are combined
- differentiation: converting one cell type into another cell type
what is hyperplasia?
increased growth
what is hypertrophy?
increased size
what is an example of physical hypertrophy?
athletes muscle, this can occur due to physiological response (due to demands put upon muscle cells)
what is an example of pathological hypertrophy?
right ventricular hypertrophy, thickened cell wall of right ventricle which arises when heart is having difficulty in pumping deoxygenated blood to the lungs
what is an example of physiological hyperplasia?
- adaptation to altitude (seen in mountaineers)
- more red blood cells are produced in indivudals who live in low oxygen regions of the world to compensate for the lack of oxygen
- this can also occur physiologically during pregnancy, in cells during the mammory cycle - as maturity increases, alveolar growth and secretory differentiation increases until after pregnancy - psoriasis - Psoriasis is achronic condition
that makes your skin cells grow too fast, resulting in red, scaly patches that can itch, hurt, or bleed.
- in psoriasis, there is an expansion of the epidermis (increased cell number, delayed differentiation and thickened stratum corneum) which is an autoimmune response, stimulating the proliferation of keratinocytes
give examples of hyperplasia in tissue repair:
- angiogenesis - thegrowth of new blood vessels
- wound healing
- liver regeneration - in alcoholic liver disease, normal cells are exposed to excess alcohol which causes liver cells to become fatty and damaged, and sometimes if exposure is continued, there are fibrous tissue deposits and scar tissue develops which eventually results in cirrhosis of the liver
what is atrophy?
decreased/regressed growth: reduction in cell size or number or both
- may require apoptosis
what is an example of physiological atrophy
- seen in thymus development with age:
thymus gland generates T cells, and in adulthood, bone marrow takes over however in development, the cortex and medulla are responsible for T cell generation and recognition - also seen in aging, with muscles get smaller
give examples of pathological atrophy
- muscle - due to fractures with plasters required
- nerves - paraplegics, part of the body is poorly innervated
- blood supply - circulatory problems, part of body not receiving good circulation of blood/oxygen
- pressure - bedsores, part of the body has excess pressure
- diet - anorexia, malnutrition
give examples of systemic growth disorders:
- hormones and growth factors
- genetics
- nutrition
- environmental factors, such as foetal alcohol syndrome
- disease such as cystic fibrosis, chronic kidney disease
proportionate alterations of skeletal growth (growth change in the size of an individual):
describe turner syndrome
what is the cause?
turners syndrome: genetic abnormality
- A girl with Turner syndrome only has 1 normal X sex chromosome, rather than the usual 2 X chromosomes
- This chromosome variation happens randomly when the baby is conceived in the womb.
- individuals are seen as quite small
^ this is sue due to the lack of SHOX gene, which is found in the pseudo-autosomal region (usually all individuals have 2 SHOX genes)
- it encodes a transcription factor, which binds to DNA
- expressed in chondrocytes of the human growth plate, particularly in hypertrophic cells (cells with increased size) therefore without SHOX, there are no enlarged cells and therefore is no growth
proportionate alterations of skeletal growth (growth change in the size of an individual):
describe down syndrome
- caused by a trisomy 21 (chromosome 21)
- causing a small stature, meaning chromosome 21 has a gene which affects growth
- hypotonia, heart defects, learning difficulties
proportionate alterations of skeletal growth (growth change in the size of an individual):
describe Beckwith-Wiedemann syndrome
- inheriting two copies of a chromosome from one (paternal) parent and none from the other is bad news
- increased expression of IGF-II (insulin growth factor-2)
- decreased expression of H19 (H19 is a gene for a long noncoding RNA, found in humans and elsewhere. H19 has a role in the negative regulation (or limiting) of body weight and cell proliferation)
- overgrowth especially in early childhood
proportionate alterations of skeletal growth (growth change in the size of an individual):
describe pituitary gigantism
- increased IGF-1 (insulin growth factor-1)
- increased growth hormone
- often from pituatary tumours
examples of disproportionate alterations of skeletal growth:
describe achondroplasia
what is it due to?
- achondroplasia: A type of bone growth disorder. Due to genetic mutations, the cartilage does not convert into a bone during foetal development, resulting in dwarfism.
- due to a genetic defect in FGFR3 (Fibroblast growth factor receptor 3)
- loss of FGFR3 increases growth (no FGFR3 = larger long bones)
- FGFR3 suppresses growth (mutant FGFR3 = shrunken long bones)
- mutation of FHFR3 has most effect in chondrocytes, expressed in growth plate of long bones
describe the action of a fibroblast growth receptor (FGF receptor) and it’s association with achondroplasia
- the fibroblast growth receptor (FGF receptor) binds to fibroblast growth factor and dimerises which activates the Tyrosine kinase enzyme which the receptor already carries with it
- tyrosine kinase enzyme (kinases phosphorylated things) phosphorylates the receptor itself which also phosphorylated other proteins through a signal transduction cascade
- in achondroplasia, there is a mutation in the FGF receptor
