Session 3 and 4 Flashcards
What is the pre embryonic period?
describe what happens in this period
Describe the process of fertilisation
from oocyte to implantation
Describe what happens in week 1 (how the blastocyst is formed)
cleavage zona pellucida morula blastocyst- what does this contain? totipotent and pluripotent hatching implantation
How do assisted reproductive techniques work?
in vitro
4 or 8 cell stage
morula to uterus
PGD
What happens in week 2?
differentiation
syncytiotrophoblast
cytotrophoblast
bilaminar disk (what is this?)
What is the fibrin plug?
blood clot
What happens by the end of week 2?
implanted embryo + its two cavities suspended within supporting sac
Describe the process of implantation
interstitial
blood flow
chorionic villus
What are the conditions linked to implantation defects? Describe them
IUGR
pre eclampsia
ectopic pregnancy (Fallopian tube implant)
placenta praevia (lower uterine segment implantation)
Describe the embryonic pole and the abembryonic pole
syncytiotrophoblast
primitive yolk sac
What happens in the latter half of the second week?
primitive yolk sac pushed away reticulum layer maternal sinusoids uteroplacental circulation secondary yolk sac extraembryonic mesoderm connecting stalk
Define the different cavities (blastocyst cavity, amniotic sac, primitive yolk sac, secondary yolk sac, extraembryonic coelom)
first cavity spaces within the epiblast hypoblast lining blastocyst cavity definitive yolk sac chorionic cavity
Describe the embryonic period
3 to 8
change
malformation
What is teratogenesis and when is it possible?
the process by which congenital malformations are produced in an embryo or fetus
pre embryonic
embryonic
fetal
What are the key events?
fertilisation and implantation gastrulation neurulation segmentation folding
What is the primitive streak?
epiblast
dorsal surface
leads to the migration and invagination of epiblast cells
Describe the process of invagination and migration
epiblast cells intracellular junctions embryonic disk hypoblast third layer
What is the trilaminar disk?
ectoderm
mesoderm
endoderm
epiblast layer
remove ectoderm layer
endoderm two patches
mouth anus
What are the derivatives of the sections of the trilaminar disk?
organs structures
contact with outside world
nervous system
epidermis
supporting tissues
muscle cartilage bone
vascular system
internal structures
epithelial lining of GI
respiratory tract too
What is situs invertus?
mirror image
immotile cilia
problem forms from both normal and mirror image
Describe the left right asymmetry
bilaterally symmetrical
l lung two lobes r lung three lobes
thoracic and abdominal viscera
primitive node
ciliated cells
left ward flow of signalling molecules
without get right sidedness
Describe the function of the notochord
rod of cells midline conversion ectoderm signalling molecules endoderm not have receptors
How does the neural plate form?
ectoderm thickens
neural tube formation:
edges elevate out of plane of disk
curl
SEE CARD 27
Label the new different parts of the mesoderm
paraxial intermediate somatic splanchnic intraembryonic coelom
What are somites? What is the organised degeneration that follows?
paraxial mesoderm 31 in total start off with 1st pair at day 20 in occipital region before gastrulation more appear in a craniocaudal sequence 42 to 44 pairs at the end of week 5 some disappear regular block mesoderm cells small cavity
organised degeneration: ventral wall sclerotome further organisation of the dorsal portion forms... myotome dermatome
What are the somite derivatives?
dermatome - dermis myotome - muscles sclerotome - bones
How does folding occur?
neural tube
curl under yolk sac
cephalocaudal folding
lateral folding
see images
What does folding achieve?
margins ventral body wall amniotic membrane amniotic sac connecting stalk
What happens at the end of the fourth week?
nervous system
segments
folded embryo
What holds cells together?
cell cell adhesion molecules
extracellular matrix proteins
internal external scaffolding
close proximity
What are the epithelial cell adherence systems?
lateral surface
- 5
basal surface
- 5
What are tight junctions?
location?
fusion point
function?
paracellular transport
What are adhesion junctions?
location? pairs formed from? e- cadherin adhesion belt function?
What are desmosomes?
strongest location? random mechanical stress cytokeratin e- cadherin function? epidermal cells
What are gap junctions?
location? cardiac and smooth muscle function? Smooth muscle contraction sperm, RBC and motile cells cylinders of proteins connexin switch
What are hemi- desmosomes?
location? extracellular matrix cytokeratin, laminin basal lamina function?
What are focal adhesions?
similar function
actin filaments
integrins
fibronectin
What are integrins?
cohesive forces alpha beta dimer extracellular matrix focal adhesion kinase binding capacity eg skin
What do all of these adhesion properties/ proteins require?
presence of calcium ions in order to function
if insufficient Ca inside cell/ outside cell, adhesion molecules can’t hold in place
Describe the mucosal membrane
definition continuous mucus function? examples
What are the layers in the GI tract?
mucosa muscularis mucosae submucosa muscularis externa serosa
Describe the structure- function relationships in the oesophagus
epithelium
submucosa
muscularis externa
Label the layers in the stomach
rugae
3 layers of smooth muscle in stomach- ME
how are rugae held in this position?
Label the layers in the jejunum
jejunum- middle segment of the small intestine
plicae circulares
at this stage what is the function of these layers/ structures
two layers to the ME
Label the layers in the colon
colon= large intestine MM at this magnification simple columnar epithelium water and electrolytes Lieberkuhn- function? aggregations of lymphoid tissue
What is the function of the mucosa in the GI tract?
absorb
prevent
move
epithelial specialisations
lamina propria
muscularis mucosae
muscularis externa
Describe the structure of the urinary tract
structural unit = nephron corpuscle lining square shaped proximal tubes basal lamina
Where is the muscle first appearing in the GI tract?
ureter and bladder
urothelium
Describe the structure of the bladder and the urethra
fat shock absorber mucus acidic urine protection tight junctions function of transitional epithelium
similar squamous ➡️ keratinised squamous mucus glands absorption prevention removal
Describe the structure of the respiratory tract, trachea and primary bronchi, alveolus
gaseous
conducting and respiratory
trachaelis muscle hyaline cartilage ring primary similar but cartilage and spiral muscle differences food? mucosa submucosa c shaped hyaline cartilage secretions from epithelium and submucosal glands contain? cilia wave mucociliary escalator
flattened specialised epithelium
folds in basal lamina
at the juntion
connective tissue
Describe the mucociliary escalator in the trachea
unusually thick lamina propria elastic fibres sugar white patches GOBLET CELL
What are the secondary and tertiary bronchi?
similar cartilage no longer present epithelium pseudostratified smooth muscle seromucous glands crescent shaped no outer layer of smooth muscle
