Stem cells, implantation, embryonic development

Question 1

What is a stem cell?

Answer 1

Cell from which all other cells with specialized functions are generated
Types:
-embryonic (pluri and toti potent)
-adult (multipotent)
-placental/cord blood

Question 2

What are the some characteristics of stem cells?

Answer 2

-can replicate itself indefinitely
-provide unlimited sources of cells for repair of tissues e.g. bone, skin, muscle, etc
-can differentiate/produce specialised cells

Question 3

What is the difference between stem and specialised cells?

Answer 3

When they mitotically divide;
new stem cells = proliferation
new specialised cells = differentiation

Question 4

Define differentiation

Answer 4

Process by which dividing cells change their functional or phenotypical type
-differentiate into specialised cells

Question 5

Define differentiation

Answer 5

Process by which dividing cells change their functional or phenotypical type
-differentiate into specialised cells

Question 6

What are the two signals triggering differentiation?

Answer 6

-external: involving chem secretions of neighbouring cells+physical contact with neighbouring cells within microenvironment
-internal: controlled by genes

Question 7

Define potency

Answer 7

The potential capacity of a stem cell to differentiate into different specialized cell types

Question 8

What is totipotent?

Answer 8

Stem cells capable of developing into a new organism
-have the ability to form embryo+membranes that surround, support, nourish the embryo

Question 9

What is pluripotent?

Answer 9

Stem cells with potential of developing into any cell/tissue founds in adults

Question 10

What is multipotent?

Answer 10

stems cells with potential of developing into only a few cell types
-usually those found in the organ from which they derived=have a specific function

Question 11

What are embryonic stem cells?

Answer 11

Undifferentiated cells taken from the inner cell mass of a 3-7 day old embryo
-totipotent or pluripotent as they have potential to become a wide variety of specialised cell types

Question 12

What is implantation? How does it occur?

Answer 12

Process that enables the blastocyst to gain nourishment
-occurs after cyst has been in uterus 2-3days
-blastocyst sinks into the soft endometrium
-then absorbs nutrients from glands/blood vessels of uterine lining

Question 13

Define blastocyst

Answer 13

A hollow cluster of dividing cells made by a fertilized egg

Question 14

What are the 3 germ layers?

Answer 14

Endoderm
Ectoderm
Mesoderm

Question 15

What is the ectoderm (outer most layer)

Answer 15

-epidermis
outer layer of body, skin, hair, mammary glands, nervous system

Question 16

What is the mesoderm (middle layer)

Answer 16

Forms skeleton, muscles, connective tissue, heart, blood, urogenital tract
+stomach and intestines

Question 17

What is the endoderm? (inner layer)

Answer 17

Forms lining of digestive system, lungs, thyroid

Question 18

What occurs following implantation? (hormone production)

Answer 18

-blastocyst continues to develop if endometrium is maintained
-needs high levels of oestrogen+progestrone to be produced
hormones stop break down of endometrium/menstrual cycle
-corpus luteum produces oestrogen+progestrone required for support

Question 19

Define corpus luteum

Answer 19

Cells remaining in ovary from follicle once oocyte is released

Question 20

What are the embryonic membranes (2 most important)

Answer 20

-amnion—Surrounds the embryo, enclosing a cavity into which it secretes amniotic fluid
-chorion—Formed from the outer cells of the blastocyst and a layer of mesodermal cells
-yolk sac
-allantois

Question 21

What is fertilisation?

Answer 21

begins following ejaculation
occurs when a sperm fuses with the egg that gets implanted in uterus of the female (becomes a zygote)
sperm travels through the fallopian tube and penetrates the zona pellucida layer of the ovum (female egg) and fuses with it which forms zygote (fertilized egg).

Question 22

What is the placenta?

Answer 22

An organ that forms form maternal and foetal tissues during the first three months of gestation (embryo development)

Question 23

Placenta functions

Answer 23

Immune-transports antibodies from mother into foetal blood supply so foetus has immunity to some infectious diseases
Respiratory-transports oxygen form mother to foetus and C02 from foetus to mother
Endocrine-secretes many hormones (oestrogen, progesterone, HCG) for pregnancy maintenance
Nutritional- transports nutrients (glucose, amino acids, fatty acids, vitamins, minerals, from mother’s blood to foetal blood
Excretory- transports nitrogenous wastes such as urea, uric acid, ammonia and creatinine from foetal blood to mother for excretion by kidney

Question 24

Ways hormones aid pregnancy (3 main types)

Answer 24

HCG- Human chorionic gonadotropin helps thicken a person’s uterine lining to support a growing embryo and tells the body to stop menstruation
Oestrogen- allows the uterus and placenta to create new blood vessels and transfer nutrients to your baby.
Progesterone- helps the uterus (womb) grow during pregnancy and keeps it from having contractions.

Question 25

How is a blastocyst formed and what is it?

Answer 25

A hollow ball of cells that surround a cavity filled with fluid.
Made following fertilisation when the original zygote has reached the uterus and has developed.

Question 26

Define gonads

Answer 26

Primary reproductive organs that produce gametes

Question 27

What is colostrum? Where is it produced?

Answer 27

A watery yellowish white fluid, with a high content of the mothers anti bodies, that are secreted from the breast at the time of child birth.

Question 28

What are fimbriae and their function?

Answer 28

Finger like projection that will bring the ovum to the fallopian tube from the ovaries.

Question 29

Why do maternal and foetal blood not mix?

Answer 29

Foetal blood circulates in the chorionic villi of the placenta whereas the mother’s blood pools in the spaces around the chorionic villi, bathing the villi in maternal blood.
The villi act as a barrier, as they are comprised of a few layers of cells however, an exchange of materials can occur via diffusion between the two blood supplies.

Question 30

What is the ovarian cycle? and it’s process?

Answer 30

Series of events that take place within the ovaries
1. primary follicle -which begins to enlarge and divide, creating a layer of cells around the developing egg influenced by FSH
2. secondary follicle -cavity forms and production of oestrogen
3. mature follicle -secretions of these cells create a fluid filled space that gradually forces the egg to the edge of the follicle
4. when the mature follicle bursts it expels the egg (ovulation)
5. influenced by LH

Question 31

What is the menstrual cycle? and it’s process?

Answer 31

Events occurring in the endometrium
1. ruptured follicle collapses into the corpus luteum
2. secretion of progesterone and oestrogen by corpus luteum
3. oestrogen and progesterone maintain the endometrium lining
-if fertilisation occurs: LH maintains corpus luteum for 3 months (then placenta takes over endocrine function)
-no fertilisation: scar tissue (corpus albicans) forms; hormone secretion ceases