Embryology

Question 1

4 stages of embryonic development in ALL animals

Answer 1

1) Fertilization
2) Cleavage
3) Gastrulation
4) Organogenesis

Question 2

Homologues of this drosophila gene are important in embryonic development

Answer 2

Tinman gene - regulates heart position in drosophila

Question 3

3 key events in fertilization

Answer 3

1) Contact
2) Acrosomal reaction
3) Cortical reaction

Question 4

Contact

Answer 4

1st stage of fertilization

- Sperm makes contact with protective egg coating (Zona pelludica)

Question 5

Acrosomal reaction

Answer 5

2nd stage of fertilization

• enzymes dissolve jelly coat
• molecules on sperm bind to receptors on egg
• species specific binding process (not in all mammals)

Question 6

Cortical reaction

Answer 6

Changes at surface of egg prevent further sperm from entering - Polyspermy

Question 7

Zona Pellucida

Answer 7

Outer jelly coating of the females egg while still in the ovary

Question 8

What occurs when the head of the sperm contacts an egg

Answer 8

Spermatozoon touches Zona pellucida
- triggers acrosomal process
- spermatozoon release hydrolytic enzymes
from the acrosome (head)

Question 9

What is the significant process within the acrosomal process within fertilization?

Answer 9

Release of actin filaments

• pierce the jelly coat
• Proteins on the tip of the acrosomal process bind to receptors and act as lock and key

Question 10

Acrosomal process - Non-Mammals

Answer 10

Quick-Block Process

• Binding of proteins on acrosomal process causes fusion of spermatozoon and egg
• Fusion triggers Na release
• Na influx causes depolarization
• Depolarization blocks other sperm from fusing

Question 11

Cortical Reaction

Answer 11

All Mammals
Longer lasting - block polyspermy
- Cortical granules beneath egg membrane released into perivitelline space
- Hardens
- Receptors clipped off
- No further binding of other sperm

Question 12

What is is called when rapid cell division occurs and a single egg (zygote) forms many smaller cells?

Answer 12

Blastomeres

Question 13

What are the first 5-7 divisions called?

Answer 13

Blastula

Blastocyst (in mammals)

Question 14

What is it called when many small cells surround a fluid filled space?

Answer 14

Blastocoel

Question 15

What are the two main types of cleavage systems?

Answer 15

1) Holoblastic

2) Meroblastic

Question 16

Holoblastic cleavage

Answer 16

• yolk concentrated at vegetal pole
• indentation causes “cleavage furrow”
• 1st cleavage: furrow crosses over both vegetal and animal pole
• 2nd cleavage: 90deg. to 1st cleavage
• 3rd cleavage: produces 8 distinct cells

Question 17

Meroblastic

Answer 17

Furrow cannot pass through vegetal pole
Cleavage only occurs in animal pole
- Results in blastula (blastocyst) which contains a fluid filled blastocoel

Question 18

What types of animals undergo Meroblastic cleavage? (5)

Answer 18

1) Monotremes
2) Birds
3) Reptiles
4) Fish
5) Insects

Question 19

What types of animals undergo Meroblastic cleavage? (5)

Answer 19

1) Monotremes
2) Birds
3) Reptiles
4) Fish
5) Insects

Question 20

Which pole of the zygote is and which type of systematic cleavage impedes furrow formation

Answer 20

Vegetal pole / Meroblastic cleavage

• vegetal pole is more dense and impedes cleavage in certain directions
• difference in pole density is feature of systematic cleavage

Question 21

Embryoblast

Answer 21

Inner collection (mass) of cells which is attached to the trophoblast
- Trophoblast: outermost layer of cells before zona pellucida

Question 22

Gastrulation results in which 3 layers in the embryo?

Answer 22

1) Endoderm
2) Mesoderm
3) Ectoderm

Question 23

Endoderm forms: (3)

Answer 23

1) Epithelial lining of respiratory, excretory, reproductive tracts
2) Epithelial lining of digestive tract and liver/pancreas
3) Thymus, thyroid, and parathyroid

Question 24

Mesoderm forms: (5)

Answer 24

1) Musculo-skeletal system
2) Circulatory/lymphatic systems
3) Excretory/reproductive systems (not germ cells)
4) Dermis of skin
5) Adrenal cortex

Question 25

Ectoderm forms:

Answer 25

1) Epidermis of skin (and sweat glands, hair follicles) 2) Nervous/sensory systems 3) Pituitary gland, adrenal medulla 4) Jaws and teeth 5) Germ cells

Question 26

If the first "hole" in the zygote is called the blastocoel, the second one is called?

Answer 26

Archenteron | Archenteron eventually displaces blastocoel and is the only "hole"

Question 27

Frog Gastrulation

Answer 27

- Hollow ball of cells - Blastocoel eventually displaced by Archenteron - Endoderm forms yolk plug surrounded by blastopore - Blastopore develops into anus - Mouth/digestive cavity develops form archenteron

Question 28

Bird Gastrulation

Answer 28

Frog: Hollow ball of cells Bird: Disc of cells Contain 2 layers: Epiblast, Hypoblast EMBRYO DEVELOPS FROM EPIBLAST

Question 29

The "disc" gastrulation process found in birds is called?

Answer 29

Blastoderm

Question 30

Primitive streak

Answer 30

Occurs during gastrulation in birds - Outer epiblast layer innervates towards yolk - Downward cell movement: Endoderm - Lateral cell movement: Mesoderm - Cells left on surface: Ectoderm

Question 31

What embryonic development changes occur in the zygote before implantation into endometrium of uterus?

Answer 31

Inner cell mass (embryoblast) further divides into 1) Epiblast 2) Hypoblast Cells of epiblast move inward via the primitive streak and form mesoderm and endoderm

Question 32

Totipotent:

Answer 32

- Stem cells which can for all cells of the body | - First few divisions after fertilization: 8-cell stage

Question 33

Pluripotent:

Answer 33

- Can form all cell types of the body but NOT the extraembryonic tissue

Question 34

Multipotent:

Answer 34

Adult stem cells Found in bone marrow/adipose tissue Limited differentiation ability - Mesenchymal stem cells (MSCs) - cartilage, bone, adipose, [good at forming cells originating from the mesoderm]

Question 35

Induced pluripotent stem cells

Answer 35

iPSC's | Produced from adult cells via 'reprogramming'

Question 36

Induced pluripotent stem cells

Answer 36

iPSC's | Produced from adult cells via 'reprogramming'

Question 37

Neurulation

Answer 37

Process of forming the notochord

Question 38

Neurulation (process)

Answer 38

Ectoderm above the notochord becomes the neural plate Neural folds: Adjacent tissue comes together to form top of neural tube Neural tube: Formed by neural ectoderm

Question 39

What are the two types of cells which form near the neural tube?

Answer 39

1) Neural crest cells | 2) Somites

Question 40

Neural crest cells

Answer 40

- Form from neural folds - Migrate to many parts of the embryo - Neurons, bone, pigment cells

Question 41

Somite Cells

Answer 41

- Form from mesoderm | - Play major role in organizing and segmentation of body (ex, vertebrae and associated muscles)