lecture 24 - development and inheritance Flashcards
intraembryonic coelem splits into:
splanchnopleuric mesenchyme
somatopleuric mesenchyme
splanchnopleuric mesenchyme becomes:
the heart
somatopleuric mesenchyme becomes
bones, ligaments, blood vessels, etc
development of chorionic villi and placenta happens in week
3
as embyronic tissue invades the uterine wall, what happens? waht does this cause
maternal uterine vessels are eroded
cuases trophoblastic lacunae to form intervillous spaces that fill with maternal blood
chorionic villi develop as:
develop as outgrowths of the chorion that project into the endometrium
by the end of the third week, what develops in chorionic villi? what will they connect to/
blood capillaries that will connect to the embryonic heart by umbilical arteries and veins via the connecting stalk
intervillous spaces function
bath chorionic villi in maternal blood
bloods do not mix
placentation
forming of the placenta
what forms the placenta (2 layers)
chorioic villi of the chorion
- fetal portion
basal layer
- maternal portion
functions of placenta (3)
allow exchange of nutrients and waste between mom and baby
produce hormones for sustaining pregnancy
acts as a barrier to most microorganisms
example of things that can pass the placenta
drugs, alcohol, HIV
umbilical cord develops from
the connecting stalk
umbilical cord function
connect placenta to embryo
umbilical cord makeup
2 arteries
- carry deoxy retal blood to placenta
1 vein (big)
- carry oxy blood to fetus
afterbirth
placenta detaches from uterus following birth
what is special about the blood in the umbilical cord
called cord blood
pluipotent stem cells are sourced from here
stem cell terminology (5)
totipotent
pluripotent
multipotent
oligopotent
unipotent
totipotent stem cells (def and example)
can form any of 220 cells types in the body. can form an entire organism
ex. blastomeres, zygotes
pluripotent stem cells (def and example)
tissue specific, differentiate from totipotent cells but can form MANY cells, not ALL cells.
ex endoderm, mesoderm, ectoderm
multipotent stem cells (def and example)
differentiate into a group of closely related cells
ex. hemotopoietic cells that can form myeloid and lymphoid stem cells (for blood cell/lymphocyte production)
oligopotent stem cells (def and example)
develop into only a few cell types
ex myeloid cells that form different blood cell types (but not lymphocytes like multipotent cells)
unipotent stem cells (def and example)
produce only one type of cell
ex. spermatogonia only form sperm
weeks 1-8 are known as ______. what are the main 2 processes that take place in these weeks
embryonic period or first trimester
organogenesis and placentation
4 major events from week 3 and brief description of what they are
gastrulation
- primary germ layers
neurulation
- segmentation of ectoderm to separate neural tissue from skin
somite formation
- segmentation of mesoderm to separate heart from bones/blood vessels
formation of heart
week 4 events (1)
organogenesis
how big does the emrbyo grow in week 4
3 times
embryonic folding
process where the flat embryonic disc folds into a 3D cylinder: head/tail, and two lateral folds
looks like a contact lens sort of
after embryonic folding, the embryo now has a distinct: (4)
superior/inferior, left/right, anterior/posterior, and primative gut
organogenesis
formation of body organs and systems
what week do the pharyngel arches develop
4
pharyngeal arches and what they contain
protrusions below the “head” of the fetus
each contains an artery, cranial nerve, and skeletal muscle
what separates pharyngeal arches
pharyngeal grooves
pharyngeal arches
separate pharyngeal grooves on the ectodermal side
what is on the endodermal side of the pharyngeal arches
pharyngeal pouches
pharyngeal arches are made of;
ectoderm, mesoderm, and endoderm layers except in teh groove area
what do teh pharyngeal pouches form?
future head and nekc structures
otic placode is made of _____ and forms the___-
ectoderm, forms future internal ear
lens placode is made of ______ and forms the ______
ectoderm, forms future lens of eye
limb buds
mesoderm covered by ectoderm, create future limbs
heart prominenece
distinct projection on ventral surface that will become the heart
when do teh limb buds form
week 4
when does the heart prominence form
week 4
development in week 5-8 8 is:
rapid
development of in week 5-8: head
rapid brain development and growth of head
development of in week 5-8: heart
becomes 4 chambered, blood cells form in liver
development of in week 5-8: limbs
limbs form and lengthen, digits develop and separate
development of in week 5-8: face
eyelids and auricles form
development of in week 5-8: external genitals
begin to differentiate, tails shorten and disappear
development of in week 5-8: primative gut and other internal organs
continue development
development of in week 5-8: bone
formation begins
once the embryo has clear human features, it is known as a :
fetus
week 9-birth (2)
all structures developed in the embryonic period continue to grow and differentiate
very few structures form after week 8
(nipples, hair follicles, hand prints)
what happens to the fetus after week 9?
grows larger, movements start, limbs and digits lengthen, fingernails/toe develop
waht week can a fetus survive prematurely
24
from 28 weeks to birth, what happens to the fetus? (5)
rapid growth, strength gain, brain development, changes in respiratory and circulatory systems to prepare for breathing, head changes proportion
3 main causes of abnormal development
- unknown
- genetics
- environmental (teratogens)
teratogens
one of the causes of abnormal development
eg. alcohol, viruses, smoking, radiation etc
- most harmful during weeks 3-8 (organogenesis)
fetal ultrasound
transducer emits high freq sound waves that reflects sound waves converted to an image on a screen
- patient needs full bladder
- used to confirm pregnancy, determine fetal age, viability, growth, gender, and abnormalities
quad screen
non invasive test done between 16-18 weeks
tests maternal blood for 4 things:
- alpha fetoprotein (AFP) produced by fetus
- hCG produced by placenta
- estriol produced by fetus/placenta
- inhibin A produced by placenta
abnormal levels in a quad screen may indicate:
neural tube defect (too much AFP)
trisomy 21, 18 or other chromosomal disorders
AFP
alpha fetoprotien
amniocentesis test is used to detect
suspected genetic abnormalities
how is amniocentesis done
needle through abdominal wall remove some amniotic fluid that contains fetal cells for analysis
what is done with the amniotic fluid is an amniocentesis
fetal cells from the fluid are examined for chromosomal abnormalities
chorionic villi sampling proceedure
needle through abdominal wall OR suction thru cervix to remove chorionic villi (contains same genome as fetal cells)
can be preformed as early as 8 weeks
chorionic villi sampling is used for
detecting genetic abnormalities
hCG
human chorionic gonadotropic
hCG is secreted by
the chorion
hCG function
stimulates continued production of estrogen and progesterone by corpus luteum whihc is necessary for attachment of embryo /fetus to endometirum
when can hCG be detected in blood
8 days after fertilization
when does hCG peak
week 9, then decreases in month 4-5 and levels off till birth
estrogenes and progesterone are produced by _____. when?
corpus luteum in the first 3-4 months of pregnancy to maintian uterus lining and prepare mammary glands, increases a lot later on
progesterone function
keeps uterine myometirum relaxed and cervix closed
hCS
human chorionic somatomammotropin
human chorionic somatomammotropin
(hCS) functions (2)
helps prepare mammary glands for lactation
decreases glucose use in mother so that more glucose is available for fetus
- mother will use fatty acids for ATP instead
- promotes release of fatty acids
corticotropin releasing hormone (CRH) functions (2)
establishes timing of birth
- high levels = premature birth
increases secretion of cortisol
- important for lung development
hormones secreted by placenta (4)
- human chorionic gonadotropin
- relaxin
- human chorionic somatomammotropin
- corticotropin releasing hormone
changes during pregnancy - GI tract
heartburn, constipation
increase appetite
changes during pregnancy - urinary bladder
increased frequency and urgency of urination
changes during pregnancy - inferior vena cava
varicose veins and edema in legs
changes during pregnancy - inferior vena cava, aorta, renal artery
less blood flow, renal hypertension
changes during pregnancy - weight gain
- increase protein, fat, water storage
- weight of fetus + all structures
- breast enlargement
- lower back pain
changes during pregnancy - cardiovascular
- increase heart rate (10-15%)
- increase Cardiac output (20-30%)
- maternal blood vol increases by 30-50%
all of these changes are needed to meet needs of fetus
changes during pregnancy - respiratory
- increase tidal volume (30-40%)
- total body O2 consumption increases by 10-20%
changes during pregnancy - urinary system
increased renal plasma flow, which increases GFR up to 40%
increased urination
labour
expulsion of fetus from uterus thru vagina
hormones elevated during labour (4)
estrogens, prostagandins, oxytocin, relaxin
what effects must be reversed in order for labour to occur? why??
progesterone secretion must stop
progesterone has been secreted by the placenta to maintain pregnancy. I relaxed the myometrium and kept the cervix closed
for labour to occur, this must be reversed
how are the effects of progesterone reversed for labour to start?
increased estrogen levels overcome progesterones effects
how to estrogen levels rise to initiate labour? (4 steps)
- placenta secretes CRH
- fetal anterior pituitary secretes ACTH in response to placental CRH
- fetal suprarenal glands secrete cortisol and DHEA in response to ACTH
- placenta converts DHEA to estrogens
loop between palcenta and fetus
estrogens role in labour (2)
incease oxytocin receptors on uterine muscle fibres
stimulate placenta to release prostaglandins which dilates teh cervix
oxytocin role in labour (1)
release by maternal posterior pituitary to stimulate contractions
relaxin role in labour
released by placenta, increases pubic symphysis flexibility and dilates cervix
positive feedback loop during labour
stimulus
- contraction of myometrium forces fetal head into cervix
receptor
- stretch receptors in cervix send impulses to hypothalamus
control centre
- hypothalamus/AP release oxytocin into blood
effector
- oxytocin causes more contractions, baby descends, producing more stretching of cervix
response
- cervix continues to dilate due to baby pushing on it
positive feedback loop ends with birth because stretching suddenly ends
false labour
abdominal pain at irregular intervals
does not intensify
true labour
regulate, painful uterine contractions that increase in frequency and intensity
back pain
dilation of cervix
vaginal discharge with blood
3 stages of true labour
dilation
expulsion
placental
dilation stage of labour (4)
6-12 hours
regular contractions
complete dilation of cervix
amniotic sac usually ruptures
expulsion stage of labour (2)
10 mins to several hours
baby move through and out of birth canal
placental stage of labour
known as afterbirth
placenta expelled 5-30 mins after delivery
how long does it take the mom to return from pre pregnancy state
about 6 weeks,, very variable
maternal postnatal period (3)
uterus undergoes involution (size reduction)
uterine discharge called lochia from former placenta site
cervix loses elasticity and becomes firm
postnatal adjustments to infant - prebirth
prebirth, teh fetus had:
placental O2/nutrient supply
placental waste removal
amniotic fluid pressure
fetal respiratory/cardiovascular system attached to placenta
respiratory changes in fetus after birth
increased CO2 levels in blood stimulate respiratory centre in medulla, triggers first breath
- forceful inhalations and exhalations
- rate begins and 45 breaths/min for first 2 weeks, slow after to 12
when is teh fetal respiratory system well developed
month 7
changes in cardiovascular system after birth (6)
all changes are stimulated by breathing
foramen ovale becomes fossa ovalis
- deoxy blood is now sent to the lungs
ductus arteriorsus shuts (connected aorta and pulmonary vein
- becomes ligamentum arteriosum
umbilcal vein closes
- becomes ligamentum teres
umbilical arteries close
- become medial umbilical ligaments
ductus venosus collapses
- now allows venous blood into hepatic portal vein to liver
high pulse as birth (120-180)
- o2 demand increases, increasing erythropoiesis (negative feedback loop)
ductus arteriosus becomes
ligamentum arteriosum
umbilical arteries and vein become
arteries
- medial umbilical ligaments
vein
- ligamentum teres
ductus venosus becomes
collapsed to allow fetal venous blood into hepatic portal vein
patent foramen ovale (PFO)
foramen flap remains open
occurs in 25% of births
no symptoms, not treated
unverified links to migraine and stroke occurrence
