Lecture notes

Biomedical sciences 2 lecture notes (semester 2)

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Module
Biomedical Sciences 2

Institution
The University Of Edinburgh (ED)

Topics: Fertilisation, Assisted Reproduction and Contraception, Renal system, Autonomic nervous system, Inferring from data, Cardiovascular system, Molecular techniques, Homeostasis & obesity, Inflammation, Sensory & motor systems, pain & analgesia

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Uploaded on May 15, 2022
Number of pages 69
Written in 2021/2022
Type Lecture notes
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Biomedical sciences 2 complete lecture summaries

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1. Lecture notes - Biomedical sciences 2 lecture notes
2. Lecture notes - Biomedical sciences 2 lecture notes (semester 2)
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BMSZ (semi)

, Fertilisation ,

Assisted Reproduction

i.
Contraception

,129 -
Fertilisation & early embryo development

Embryogenesis metric
assy
division
(generic ;;Ywe%¥
In 2h
01 .

MISH n

↑ LH

h

In 4 sperm

☐

, complete M2
.

to
Female MS fertilisation

" Kicky
polar body
Zona pellucida ( glycoprotein coat ) & prevents polyspenny (not compatible with life in humans
)
-

protects oocyte as
goes through oviducts +
from species
entering oocyte & mediates species specific -

recognition
^

human
Mouse
egg
e

14µm thick human ↓
7pm
.

vs in vs mouse
mouse sperm < human ↓ from carbohydrate
ZP4
has extra
residues
Cumulus cells Protein cumulus cells

%¥¥☒
thin

(above ZP ,
penetrating it with their processes into
cytoplasm of egg)
Functions :
penetrate ZP it egg

form intracellular
junctions with
oocyte cell mem .

Male
head shape species but ubiquitous
→
varies across components

Drosophila bifurea has
largest sperm 16cm long)
✗ 20 longer
than animal → spembund

, Fertilisation
Requires various barriers :

small window
{

3 stages of fertilisation
1) sperm preparation facnsome reaction)
2) sperm binding fusion r

3) preventing polys penny (cortical reaction

1) Sperm preparation
-

CAPA CITATION

oviduct
•

in

mature
allows sperm to
acquire capacity
to
fertiliser making it less stable
by losing
• :
via

cholesterol , phospholipids A
r
glycoproteins on
surface causes in tail movement

( hyperactivation)

1) Sperm preparation
-

A CROSOME REACTION

induced
by progesterone
•

↓

proteolytic enzyme release
( eg hyaluronidase for pores @ outer acnsomal mem .

↓
expose acres in @ inner aowsomal membrane

↓

expose surface molecules for sperm
binding to ZP receptors
⑨ Izumo
1)

,Sequence of events in
fertilisation

} """ "
this order of events .
"""

(
on )
its side

↑ I
penvitaelline oolemq
space

Time lapse experiment by
:

by
ZP penetrated aerosome -

reacted sperm or not acw some -

intact sperm
( remains on ZP
surface )

2) Sperm binding
-

OOCYTE PLASMA MEMBRANE

sperm Renard enters perivitelline space and
immediately after fusion with oolema the tail stops beating
•

↓

sperm head binds on its side to
oocyte ( via Izumo 1
ligand on
sperm head with Juno on
egg) .

↓
microvilli on
oocyte mem .

engulf sperm
↓

swelling (fertilisation )
at point of there is
fusion
cone

,3) Preventing polys penny -

CORTICAL REACTION

cortical
•

granules from inside with plasma contents released into pen : space
egg fuse
mem .
or .

-

t proteases peroxidases
, ,
polysaccharides
As structure
of ZP (which prevents polyspenny )
-
=
Zona block
I
2
ways
✓↳

{
2-0Mt REACTION
/ MEMBRANE
BLOCK
Zohra BLOCK

slow block 2- P2 cleaved
Juno shed
receptor
gradually gum
• •

80 mem
plasma membrane
oligosaccharides
ZP 3 removes
.

other sperm
•
so
block also
•

cross-link other ZP proteins cannot bind
440min after sperm
entry) .

w
polyspenny can still take place 4 -2% in vivo
/ 10% in
vitro

sperm contribution to
zygote
•
whole sperm enters
oocyte in most mammals
Conly head in
golden hamsters
mt
destroyed
→ mt inherited
sperm zygote maternally
•

.
.
all

sperm centriole has different fates
•
:

-
in humans it
incorporates into
zygote r
organises
1st mitotic spindle µ -
cell → 2- cell
embryo)
A

rodents it not retained
-

in is .

Formation
of zygote
As sperm enters female
"
ca Spike → stimulates to continue meiosis 1st nucleus
→ →
firms
v1 (female pronucleus )
sperm undergoes dramatic transformation t
2nd polar
body

}
-

sperm nucleus decmclenses

nuclear mem
forms around sperm DNA 24h to male Dmt
-

reprogram
~
.

me

sperm DNA
actively demethylation
-

-
histones replace protamines in
sperm chromatin
✓ ↳ nuclear proteins that protect DNA and aid in

male pronucleus tightly packing it to make it fit in
sperm
head .

, 1st mitotic division
[post fertilisation ,
takes 18 -24h
]
1) dissolving of pronuclear envelope
2)
syngamy merging of gametic ( )
-
Ftm chromosomes on spindle

3) formation of 2- cell
embryo .

Cleavage
series
of rapid
divisions without cell
growth divisions are
reductive BLASTOMERES
( totipotent
)
-

I
so produce
cleavage timings (quicker development
can
As between mouse r human in
mice placenta
as all
as

cells
well

of
-

early embryogenesis
-

body
occur at same time

Compaction [takes 10h ] e- but independent → Polarisation
8- cell smooth starts @ 8- cell
stage each cell
gains polarisation to become
•
= •

then compaction
cells
flattened increases cell-to-cell contact epithelial like :
•
-

microvilli
confines
to
requires action E-cadherin p catenin microvilli @ outer apical surface
•

surface of
r - -

↓
¥÷÷¥ ☆ -

organelles @ outer apical region
embryo to
• •

allows
become
closely @ basal
-

nucleus inner
region
a

bonded
single entity

1
-

formation of tight junctions

cells continue to divide

↓
MORULA
( 16 cell
)
-

dinner ]
outer polarised cells
→ Allows
polar BLASTOCYST
a cells
formation

cavitation (blastocyst formation
•
ATP -

dependent pump system
: Nat
=
pumped into
blastocyst cavity ! Hwn in
by osmosis

↓
cavity expands
( BLASTOCOEL E)
↓ embryo now

essential differentiated
for proper development of ICM
into ICM t
at end
as inner polar cells remain one f-
a
troph ectoderm
t f

,Blastocyst implantation [day 8- a ]
hatches
embryo from
ZP with 1- 2d
after entering uterus .

survival obstacle
This step is a
significant as -

tz fail to
successfully implant

, L 30 -
Assisted reproduction

30.1
Understanding the female reproductive system
@ period :
endometrium 3mm
4- 5mm
small
follicles

@ tod after period :

follicles 11mm

@ 1 2d :
endometrium 9mm

follicles 14mm

@ Kid :

pre ovulating follicle 18mm

fertile mucous present (
in prep to let sperm into
.

uterus
sperm swims all the
way
into
fallopian tube

J
V
meet
has
ovary grown
a
big follicle
# egg released → picked up by
tube
follicle released fallopian

✓

follicle collapses down and cells
change
bÉmes CL

CL
very vascular
( ✗8
of kidney) since it produces a lot
of progesterone
↓
A endometrium
by stopping
its
growth starts secreting
+

proteins important for early
nourishment
pregnancy
.

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