SUGAR

Question 1

at what day does the developing embryo switch from using maternal RNA to using its own genetic code

Answer 1

day 5

Question 2

what is the major thing that happens on cleavage, day 2

Answer 2

splitting of the ooplasm (cytoplasm). if one of the pronuclei failed to condense, it can results in mosaicism

Question 3

what stage happens at day 4 of embryonic development in utero and what is its 2 key steps

Answer 3

compaction. flattening of cells and formation of tight junctions between cells

Question 4

what happens in cavitation, day 5

Answer 4

tight junctions form between the outermost layer of cells, the trophectoderm.

Question 5

at which of the 7 stages can the embryo be classed as a blastocyst and why

Answer 5

cavitation. it is formed of more than 80 cells

Question 6

what happens at day 5/6 and give a key step in it

Answer 6

expansion. pumping of fluid into the blastocyst to cause the zona pellucida to become thinner

Question 7

what are the 2 factors that cause hatching at day 6

Answer 7

enzymatic factors and expansion by the pumping of fluid in

Question 8

what are the 3 stages of implantation

Answer 8

apposition, adhesion invasion

Question 9

at which stage of implantation do receptor ligand integrations occur and what are the receptors called, and what are they on

Answer 9

adhesion, integrins, on the trophectoderm cells

Question 10

what substance is produced as part of the decidual reaction, by the endometrial stromal cells, that prevents rejection of the embryo by maternal cells

Answer 10

interleukin 2

Question 11

what are the 2 cell layers below the trophectoderm?

Answer 11

epiblast (directly under) and hypoblast

Question 12

what does hCG stand for, where is it produced and what does it support

Answer 12

human chorionic gonadotropin, placenta, corpus luteum

Question 13

where along the nephron is bulk phosphate reabsorption and is it active or passive

Answer 13

proximal, 80%, active using a sodium symporter

Question 14

what 2 hormones increase serum calcium

Answer 14

1,25 (OH)2VD and PTH

Question 15

where is PTH produced, be specific

Answer 15

in the parathyroid gland’s chief cells, these have receptors for calcium

Question 16

where is calcitonin produced, be specific

Answer 16

C cells (parafollicular cells) of the thyroid gland

Question 17

what 3 factors activate 1 alpha hydroxylase to produce more of the active vitamin d hormone

Answer 17

decreased active VD hormone, decreased FGF23, increased PTH

Question 18

what are the 2 main effects of calcium homeostasis done by active Vitamin D

Answer 18

increased absorption by active transport in the gut (so jejnum and duodenum) and increased resorption of bone

Question 19

what shape graph best describes the relationship between plasma calcium levels and PTH secretion

Answer 19

sigmoid

Question 20

what are the 3 types of calcium in the blood

Answer 20

ionised, complexed and protein-bound

Question 21

give 3 reasons why extracellular calcium must be kept at a constant level

Answer 21

nerve function, muscle function and normal blood clotting

Question 22

what is the main way by which phosphate levels can be altered in the blood

Answer 22

by the reabsorption in the kidneys

Question 23

what substance is a local regulator of FGF23 release

Answer 23

PHEX

Question 24

give 3 result of low vitamin D chemically

Answer 24

low serum calcium, low serum phosphate , low FGF23

Question 25

what do kinases do

Answer 25

add phosphate to a substance, so phosphorylation

Question 26

what do phosphatases do

Answer 26

remove phosphate from substances, so dephosphorlylation

Question 27

if PTH decreases reabsorption of phosphate by the proximal tubule, what is the fractional secretion of phosphate increased to?

Answer 27

20% from 10%

Question 28

does increased phosphate increase or decrease PTH production

Answer 28

increases it

Question 29

what cells do osteoblasts originate from and what other important cell also shares this origin

Answer 29

mesenchymal stem cells. monocytes

Question 30

what cells do osteoclasts originate from

Answer 30

haemopoietic stem cells. so are a differentiated form of macrophages

Question 31

what are the 4 paracrine/autocrine mediators of osteoclast differentiation and activity

Answer 31

prostaglandins, interleukin 1 and 6 and tumour necrosis factor (TNF)

Question 32

what substance binds to RANK-ligand, to stop it activating osteoclast precursors

Answer 32

osteoprotegrin (OPG)

Question 33

what are the 3 types of bone disease associated with rheumatoid arthritis

Answer 33

generalised osteoporosis, periarticular osteopenia (adjacent to inflammed joints) and focal bone loss

Question 34

closure of what means that bone growth can no longer take plate

Answer 34

the epiphyseal plate

Question 35

what are the 5 stages of bone remodelling in order?

Answer 35

quinesence, resorption, reversal, formation, mineralisation

Question 36

what 2 things are resultant from osteoclasts and osteoblasts communicating with eachother

Answer 36

balance and coupling (bone formation occurring at sites of previous resorption)

Question 37

what is the area in the middle of a long bone called, another word for shaft

Answer 37

diaphysis

Question 38

define modelling of bone

Answer 38

this is the changing of the gross shape of a bone, either by adding bone on to the existing or resorbing bone

Question 39

give the 5 types of bones as classified by shape

Answer 39

flat, long, short, sesamoid, irregular

Question 40

as well as being a scaffold, give 2 important functions of the ECM

Answer 40

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

Question 41

what is the name given to the tropocollagen before proteinases cleave its ends

Answer 41

procollagen

Question 42

give 3 structure that type 1 collagen is found in

Answer 42

tendons, bone and skin

Question 43

what type of collagen is in the basemnt membrane of cells

Answer 43

IV

Question 44

what 2 things are released by osteoclasts and what does each break down?

Answer 44

1. protons (dissolves the bone mineral) 2. Cathepsin K (breaks down the collagen, so the matrix)

Question 45

give the 7 stages of endochondral ossification

Answer 45

1. 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

Question 46

what is the name given to the pits that the osteoclasts reside in?

Answer 46

Howship's lacunae

Question 47

what 2 ways can primary bone develop from

Answer 47

1. mesenchyme (membrane bone) 2. cartilage proformer (endochondral bone)