Human Embryology #4 (Final) Doroski

stem cells

unspecialized cells that are able to renew themselves for long periods of time by cell division

basic properties of stem cells

self renewal & potency

normal self-renewal

cells can only divide a limited number of times

immortality

the ability to self-renew indefinitely

potency

-totipotent

-pluripotent

-multipotent

totipotent

can become all cell types including extraembryonic membranes (ex. zygote)

pluripotent

can become all cell types in human body

multipotent

can become multiple cell types

-usually from only one germ layer

differentiation

a change from one cell type to another

potency trend

generally decreases as cells differentiate

-more developed organisms generally have more differentiated cells

applications of stem cells

study of developmental processes

-zygote is first stem cell

-reveals how cells in body may develop

tissue engineering

formation of engineered tissues

-stem cells can be used to make new tissues

-tissues can be used to replace organs

embryonic stem cells

cells are always removed from the inner call mass, kill the blastocyst

-against church teaching

-immortal

-pluripotent

Fetal stem cells

sometimes improperly refers to fetal cells that are not stem cells

- ex: fetal cells used for taste testing are sometimes called fetal stem cells

- these cells come from aborted fetuses, but are not stem cells

Fetal Proper stem cells (FpSCs)

source: tissue from fetus proper

-generally obtained after an abortion

-references to fetal stem cells that are accurate refer to these

-usually against church teaching if it takes a human life

-not immortal, but high level of cell division

-multipotent

Perinatal stem cells (PSCs)

source: a cell from that body that has been "reprogrammed"

ex. skin cell plus active stem cell genes ---> pluripotent

induced pluripotent stem cells (iPSC)

source: a cell from the body that have been "reprogrammed"

ex. skin cell plus active stem cell genes ---> pluripotent, immortal, embryonic-like cell

-not against church teaching

-immortal

-pluripotent

adult stem cells (ASC)

source: tissue and from adults or earlier, generally obtained after birth

-not against church teaching

-not immortal

-multipotent

signifcant advantages

-all adult cell types

-early developmental models

-wide support

liklihood to be able to produce any cell type?

-strongest evidence: ESCs, iPSCs

-have been directly shown to contribute to all tissues of an organism

-confirmed through tetraploid complementation assays

-strong evidence: ASCs, FpSCs

-may be "pluripotent' as a population

-it may be possible to get any cell type if the correct stem cell is used

-individual cells are multipotent (not all cell types are obtained from a single source)

usefulness in early developmental models?

ESCs, FpSCs, PScs, iPSCs can provide cells from relatively early developmental stages

wide support?

-Some people may reject treatments that they have ethical objections to

-Are treatments that half of the population would be uncomfortable using prudent?

-Wide support: eFSCs, ASCs, iPSCs

-Challenged by many: ESCs, FpSCs

significant disadvantages

-Tumors

-Immune rejection

-Pluripotency

tumors

some stem cells form tumors when implanted into the body

-instability of "young' cells is linked to tumor formation

-tumor formaation: ESCs, FpSCs, iPScs

-no tumors: PSCs, ASCs

immune rejection

the body attacks non-native cells

-treatments that don't use the body's own cells require suppression of the immune system

-immune rejection: ESCs, FpSCs (cells must come from nonnative sources)

no immune rejection:PSCS, ASCs, iPSCs

pluripotency (disadvantages)

makes it difficult to obtain the exact cell type needed

-Not all cells in a population differentiate uniformly

-Undifferentiated or improperly differentiated cells can create tissues other than the desired type

clinical trials

treatments being tested for safety/efficacy

vast majority (10,000s)

PSCs and ASCs (mostly ASC)

many papers (>1000)

ESC + iPSC

few papers (

FpSC

pregnancy weight

being underweight or overweight increases risks to the child

pregnancy weight gain general guidlines

-most should gain 20-s5 lbs.

-1 lb/month in the first trimester

-1 lb/week afterwards

dieting and cravings

-cravings/aversions to certain foods can occur

-doesnt appear to be related to nutrient needs

vitamins and minerals

-vitamin d and calcium

-folate/folic acid and vitamin B12

-water

-nutrient supplements/vitamin A

vitamin D and calcium

- Builds fetal bones and teeth

-- Calcium is the main component in bone

- Vitamin D aids calcium absorption/deposition

iron

-used in red blood cells (required for rbcs)

-blood volume greatly increases during pregnancy (creates a higher need for iron)

folate/ folic acid B12

-folate needed for cell division

-aids growth development of fetus

weight loss (breastfeeding)-

-modest weight loss (1 lb/week)

-does not affect quality of breast milk

-significant weight loss can prevent lactation

role of prolactin and oxytocin

-oxytocin: prevents the let down reflex

- prolactin: generally prevents menstruation for at least six months (possibly up to a year) if exclusively breast fed

recommended breastfeeding timeline

•First six months after birth

-Exclusively breast feed

•Breast milk provides almost all needed nutrients

•After 6 months

-Continue breast feeding

-Can incorporate solid foods

water

-needs increase during pregnancy

-provides material for increasing body fluids

-aids elimination of waste

what to do if milk supply is low

-increase feedings because more demand = more supply

flavorful foods while breastfeeding

-dont need to be avoided

-child may enjoy them eventually

Carnegie stages

-developmental stages in vertebrates

-Only covers embryonic development

-Does not cover fetal development

-Categorized by visible structures

-Applicable to a wide variety of species

-Applicable to different developmental rates

-Not days or size

development vs. organism creation

-development:

when do biologists say life begins?

Fertilization

when do developmental textbooks say life begins?

fertilization

problems with using chromosomes or fertilization to identify the beginning of life

-chromosomal constitution can not define a human organism

biological categories

- Standard cases

- Unusual cases

- Non-organismal cases

- Controversial cases

standard

cases of common and typical development

-normal development

-multiple species

unusual

-developmental anomolies

-identical dna offspring

non-organismal

entities that have commonalities with organisms, but are not themselves organisms

controversial

cases where the metaphysics are uncertain and/or debated

how to identify a new organism at a basic level

- Is there an organism before the event?

- Is there an organism after the event?

- If the answer to both of these is yes...

- Is the organism after the same as the one before?

neurulation

the formation of the neural tube from overlying ectoderm cells

Neural tube

early structure that forms the brain and spinal cord

neural plate

thick area of ectoderm- Will fold to form neural tube- Runs along "back" of embryo"Head""Tail""Back""Chest"

neural tube segmentation

development of different regions of the neural tube• Forms brain and spinal cord

gut formation

-folding at sides

-folding at head

-folding at tail

somites

blocks of mesoderm tissue

intermediate mesoderm

Between somites and lateral plate mesoderm- Forms tubes of early urinary system

lateral plate misoderm

Found at edge of mesoderm

-Creates dermis of chest

-Creates outside of gut

limbs

Small limb buds form- Limb extends- Hands are initially paddles- Cells die between finger to remove webbing