SUGAR Flashcards
at what day does the developing embryo switch from using maternal RNA to using its own genetic code
day 5
what is the major thing that happens on cleavage, day 2
splitting of the ooplasm (cytoplasm). if one of the pronuclei failed to condense, it can results in mosaicism
what stage happens at day 4 of embryonic development in utero and what is its 2 key steps
compaction. flattening of cells and formation of tight junctions between cells
what happens in cavitation, day 5
tight junctions form between the outermost layer of cells, the trophectoderm.
at which of the 7 stages can the embryo be classed as a blastocyst and why
cavitation. it is formed of more than 80 cells
what happens at day 5/6 and give a key step in it
expansion. pumping of fluid into the blastocyst to cause the zona pellucida to become thinner
what are the 2 factors that cause hatching at day 6
enzymatic factors and expansion by the pumping of fluid in
what are the 3 stages of implantation
apposition, adhesion invasion
at which stage of implantation do receptor ligand integrations occur and what are the receptors called, and what are they on
adhesion, integrins, on the trophectoderm cells
what substance is produced as part of the decidual reaction, by the endometrial stromal cells, that prevents rejection of the embryo by maternal cells
interleukin 2
what are the 2 cell layers below the trophectoderm?
epiblast (directly under) and hypoblast
what does hCG stand for, where is it produced and what does it support
human chorionic gonadotropin, placenta, corpus luteum
where along the nephron is bulk phosphate reabsorption and is it active or passive
proximal, 80%, active using a sodium symporter
what 2 hormones increase serum calcium
1,25 (OH)2VD and PTH
where is PTH produced, be specific
in the parathyroid gland’s chief cells, these have receptors for calcium
where is calcitonin produced, be specific
C cells (parafollicular cells) of the thyroid gland
what 3 factors activate 1 alpha hydroxylase to produce more of the active vitamin d hormone
decreased active VD hormone, decreased FGF23, increased PTH
what are the 2 main effects of calcium homeostasis done by active Vitamin D
increased absorption by active transport in the gut (so jejnum and duodenum) and increased resorption of bone
what shape graph best describes the relationship between plasma calcium levels and PTH secretion
sigmoid
what are the 3 types of calcium in the blood
ionised, complexed and protein-bound
give 3 reasons why extracellular calcium must be kept at a constant level
nerve function, muscle function and normal blood clotting
what is the main way by which phosphate levels can be altered in the blood
by the reabsorption in the kidneys
what substance is a local regulator of FGF23 release
PHEX
give 3 result of low vitamin D chemically
low serum calcium, low serum phosphate , low FGF23
what do kinases do
add phosphate to a substance, so phosphorylation
what do phosphatases do
remove phosphate from substances, so dephosphorlylation
if PTH decreases reabsorption of phosphate by the proximal tubule, what is the fractional secretion of phosphate increased to?
20% from 10%
does increased phosphate increase or decrease PTH production
increases it
what cells do osteoblasts originate from and what other important cell also shares this origin
mesenchymal stem cells. monocytes
what cells do osteoclasts originate from
haemopoietic stem cells. so are a differentiated form of macrophages
what are the 4 paracrine/autocrine mediators of osteoclast differentiation and activity
prostaglandins, interleukin 1 and 6 and tumour necrosis factor (TNF)
what substance binds to RANK-ligand, to stop it activating osteoclast precursors
osteoprotegrin (OPG)
what are the 3 types of bone disease associated with rheumatoid arthritis
generalised osteoporosis, periarticular osteopenia (adjacent to inflammed joints) and focal bone loss
closure of what means that bone growth can no longer take plate
the epiphyseal plate
what are the 5 stages of bone remodelling in order?
quinesence, resorption, reversal, formation, mineralisation
what 2 things are resultant from osteoclasts and osteoblasts communicating with eachother
balance and coupling (bone formation occurring at sites of previous resorption)
what is the area in the middle of a long bone called, another word for shaft
diaphysis
define modelling of bone
this is the changing of the gross shape of a bone, either by adding bone on to the existing or resorbing bone
give the 5 types of bones as classified by shape
flat, long, short, sesamoid, irregular
as well as being a scaffold, give 2 important functions of the ECM
to act as a basement membrane for the attachment of cells and so stop apoptosis. to have receptors (like collagen receptors and integrins) to allow self-surface signalling and cascades of reactions within the cell
what is the name given to the tropocollagen before proteinases cleave its ends
procollagen
give 3 structure that type 1 collagen is found in
tendons, bone and skin
what type of collagen is in the basemnt membrane of cells
IV
what 2 things are released by osteoclasts and what does each break down?
- protons (dissolves the bone mineral) 2. Cathepsin K (breaks down the collagen, so the matrix)
give the 7 stages of endochondral ossification
- cartilage proliferator 2. collar formation 3. invagination of osteogenic bud 4. formation of the primary centre 5. establishment of the secondary centre 6. lengthening via growth plates 7. closure of the growth plates
what is the name given to the pits that the osteoclasts reside in?
Howship’s lacunae
what 2 ways can primary bone develop from
- mesenchyme (membrane bone) 2. cartilage proformer (endochondral bone)
