Chapter 17

Question 1

what is a zygote

Answer 1

Single cell that results from the fertilisation of an egg by a sperm

Question 2

what is a blastocyst

Answer 2

A hollow ball of cells that surround a fluid filled cavity

Question 3

what is the inner cell mass

Answer 3

Group of cells in the blastocyst that develop into the embryo

Question 4

What are stem cells

Answer 4

cells that have the ability to produce different types of body cells. Found in the inner cell mass

Question 5

what is IVF

Answer 5

fertilisation outside of the mothers body

Question 6

what is proliferation

Answer 6

the process where cells replicate themselves

Question 7

what is differentiation

Answer 7

the process by which unspecialised cells develop special characteristics to suit particular functions

Question 8

how does differentiation occur

Answer 8

When stem cells proliferate different genes become activated. Results in differentiation into specialised cells that are able to perform particular functions

Question 9

what are the internal signals that trigger differentiation

Answer 9

The cells genes turned ‘on’ or ‘off’

Question 10

what are the external signals that trigger differentiation

Answer 10

secretions by other cells, contact with other cells and molecules in its surroundings

Question 11

what are the three types of stem cells

Answer 11

Totipotent, Pluripotent, Multipotent

Question 12

what are totipotent stem cells

Answer 12

a stem cell able to create any of the types of cell necessary for embryonic development. (eg. a zygote). After 5 days, specialise into a blastocyst

Question 13

what are pluripotent stem cells

Answer 13

stem cells that are able to give rise to many but not all cell types. (eg. Inner cell mass - give rise to foetal tissues but not placental tissue).

Question 14

what are multipotent stem cells

Answer 14

stem cells that are able to give rise to a limited number of other cell types. (eg. blood stem cells will give rise to RBC’s, WBC’s and platelets)

Question 15

what is the embryonic period

Answer 15

the first two months of pregnancy

Question 16

when is a developing individual called a foetus

Answer 16

after the second month

Question 17

what maintains the endometrium

Answer 17

First through corpus luteum (progesterone + oestrogen) then via placenta. Development of blastocyst depends on endometrium being maintained

Question 18

what are primary germ layers

Answer 18

the embryonic tissues from which all tissues and organs will develop. The ectoderm, Mesoderm and endoderm

Question 19

what is the ectoderm

Answer 19

Outer tissue layer of embryo. Gives rise to the entire nervous system, Epidermis of skin, and the lens, cornea and muscles of the eye

Question 20

what is the Mesoderm

Answer 20

Middle tissue layer of the embryo. Gives rise to skeletal smooth and cardiac muscles, Lymphoid tissue and the dermis of skin

Question 21

what is the endoderm

Answer 21

Inner tissue layer of the embryo. Gives rise to epithelium of alimentary canal and its glands (liver, pancreas), Epithelium of bladder, urethra and call bladder and epithelium of vagina and associated glands

Question 22

what are the two embryonic membranes

Answer 22

Amnion and Chorion

Question 23

what is the amnion

Answer 23

the membrane that forms a cavity around the embryo. Secretes amniotic fluid into the cavity to protect the embryo

Question 24

what is the chorion

Answer 24

Outermost embryonic membrane that eventually fuses with the amnion to form the a part of the foetal part of the placenta

Question 25

what are chorionic villi

Answer 25

Finger like projections that develop from the outer layer of cells of the early embryo. Grow to form part of the placenta

Question 26

explain the development of the placenta

Answer 26

As the chronic vill penetrate through endometrium and uterine blood vessels, they become surrounded by pools of maternal blood. The villi are bathed in maternal blood but bloodstreams don’t mix. Nutrients are exchanged through diffusion and active transport

Question 27

what are the 5 roles and functions of the placenta

Answer 27

E.E.I.N.R
Endocrine - secretes a number of hormones necessary for maintaining pregnancy
Excretory - Transports wastes from foetal blood to mother’s blood for excretion from kidney
Immune - Transports antibodies from mother to foetus for immunity to some infectious diseases
Nutritional - Transports nutrients such as glucose, vitamins, amino acids to foetus
Respiratory - Transports oxygen from mother to foetus and co2 from foetus to mother

Question 28

what is inside the umbilical cord

Answer 28

x2 umbilical arteries - carry deoxygenated blood + wastes to capillaries of chronic villi
x1 umbilical vein - Carry oxygenated blood and nutrients

Question 29

what developments of the embryo occur after 1 month

Answer 29

Embryo just under 4mm. Muscle segments develop. Nervous system developed. Brain, heart, liver begin to form. Tail evident until 5 weeks

Question 30

what developments of the embryo occur after 5 weeks

Answer 30

Arm + leg buds appear, heart beating

Question 31

what developments of the embryo occur after 8 weeks

Answer 31

Recognisable human form, limbs formed, bones hardening, organs present

Question 32

what are the 3 sources of stem cells

Answer 32

• Umbilical/placental (multipotent)
• Embryonic (pluripotent)
• Adult (multipotent)

Question 33

what are the possible treatments stem cells can be used for

Answer 33

Parkinsons, Alzheimers, Diabetes, Spinal cord injuries