Chapter 3.1

Question 1

What is the acrosomal apparatus

Answer 1

• it is a tubelike structure of the sperm

- >used by the first sperm that comes into contact with the secondary oocyte

Question 2

What happens after penetration of the secondary oocyte ? Note some type of reaction occurs

Answer 2

• a cortical reaction occurs
• > release of calcium ions
• > depolarizes the ovum

Question 3

What is the point of depolarizing the ovum?

Answer 3

• depolarization prevents fertilization of ovum by multiple sperm cells
• increases calcium concentration increases the metabolic rate of the newly formed zygote

Question 4

What is the depolarized and impenetrable membrane of the secondary oocyte referred to as?

Answer 4

-it is referred to as the fertilization membrane

Question 5

How do conjoined twins come about?

Answer 5

-if division of monozygotic twins are incomplete

Question 6

What is the defining characteristic of a zygote

Answer 6

-its unicellularity

Question 7

What happens during cleavage? What ratio increases as more cleavages occur?

Answer 7

• first cleavage creates an embryo
• several rounds of mitosis keep occuring
• > size of the embryo doesn’t change
• > but there is division into smaller cells
• more divisions= greater nuclear:cytoplasmic ratio/ surface area to volume ratio
• > increased area for gas and nutrient exchange relative to volume

Question 8

What are the two types of cleavage

Answer 8

1) Indeterminate cleavage
- >results in cells that can still develop into complete organisms

2) Determinate cleavage
- >results in cells with their fates determined
- >these cells are committed to differentiating into a certain type of cell

Question 9

What does it mean when referring to morula?

Answer 9

• after several divisions of the zygote

- >it becomes a morula

Question 10

Describe the process of blastulation. What forms?

Answer 10

• the morula undergoes blastulation
• > forms the blastula
• blastula is a hollow ball of cells
• > with an inner fluid cavity known as the blastocoel

Question 11

What is the mammalian blastula known as? What two types of cells does it contain? Describe the functions of these two cell types

Answer 11

• it is known as the blastocyst
• > contains trophoblast cells and inner cell mass cells

Trophoblast cells

• > surrounds the blastocoel
• > gives rise to the chorion/placenta

Inner cell mass

• > protrudes into the blastocoel
• > gives rise to the organism itself

Question 12

What is the process of implantation

Answer 12

• it is where the blastula moves through the fallopian tube

- >implants itself in the uterus

Question 13

Where do chorionic villi originate from? Describe their structure. What do they later develop into? What is the purpose of this new developed structure

Answer 13

-they originate from trophoblasts

• they are microscopic finger like projections
• > penetrate the endometrium
• the chorionic villi later develop into placenta
• > they then support maternal-fetal gas exchange

Question 14

What is the embryo connected to the placenta by. Describe the structure of this connection

Answer 14

-umbilical cord connects an embryo to a placenta

• it has two arteries and one vein
• > vein carries freshly oxygenated blood from placenta to embryo
• > arteries carry deoxygenated blood and waste to the placenta for exchange

Question 15

What two structures does the umbilical cord form from

Answer 15

-it forms from the yolk sac and the allantois

Question 16

What is the function of the yolk sac

Answer 16

• until placenta is functional
• > embryo is supported by the yolk sac

-early blood cell development also occurs in the yolk sac

Question 17

What is the function of the allantois

Answer 17

-involved in early fluid exchange between the yolk sac and embryo

Question 18

What is the function of the amnion? What structure does the amnion surround? What structure surrounds the amnion

Answer 18

• amnion is a thin tough membrane filled with amniotic fluid
• > it surrounds the allantois
• serves as a shock absorber during pregnancy
• note the chorion surrounds the amnion as well for extra support

Question 19

What is the function of the ectoderm? Where is its location

Answer 19

• the outermost layer
• > gives rise to epidermis, hair, nails, epithelia of the noce, mouth and lower anal canal
• > but most importantly it gives rise to the NERVOUS SYSTEM

Question 20

What is the function of the mesoderm? Where is it located?

Answer 20

• middle layer
• > gives rise to the musculoskeletal, circulatory and most of the excretory systems
• > also the gonads
• so anything to do with muscular and connective tissue layers
• > eg; the muscular and connective tissue layers of the digestive system

Question 21

What is the function of the endoderm?

Answer 21

• it forms the epithelial linings of the digestive and respiratory tracts
• > including the lungs

-pancreas, thyroid, distal urinary tracts, bladder, as well as parts of the liver are derived from the endoderm

Question 22

What does the process of neurulation refer to?

Answer 22

• it occurs after the three germ layers are formed

- >it describes the development of the nervous system

Question 23

What part in the development of the nervous system gives rise to the CNS? What part gives rise to the PNS? What covers the rudimentary nervous system created by the neural tube and the neural crest cells?

Answer 23

• neural folds grow toward one another
• > until they fuse into the neural tube
• the neural tube gives rise to the CNS
• neural crest cells migrate outward to form the PNS
• the rudimentary nervous system is covered by the ectoderm cell
• > they migrate over the neural tube and neural crest cells

Question 24

What are teratogens? Give examples

Answer 24

• teratogens are substances that interfere with development
• > causing defects or even death in a developing embryo

-eg; alcohol, prescription drugs, viruses, bascteria and environmental chemicals