Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
67 Cards in this Set
- Front
- Back
|
In the development of the embryo, what is crucial to healthy development?
|
Adherence to consistency
|
|
|
What happens at ovulation?
|
The oocyte or egg cell is released by the ovary into the abdominal cavity.
|
|
|
Where does fertilisation normally take place?
|
In the lateral end of the fallopian tube.
|
|
|
Once the egg cell is released into the abdominal cavity, what happens?
|
The fimbria at the ends of the fallopian tubes sweep the egg into the tube itself.
|
|
|
According to Langman, how long do the spermatazoa remain alive in the female reproductive tract?
|
About 24 hours.
|
|
|
If it is not fertilised, how long will the egg cell remain alive?
|
12 to 24 hours.
|
|
|
How many spermatazoa are "deposited" each time according to Langman?
|
200 to 300 million.
|
|
|
How many spermatazoa reach the site of fertilisation?
|
Only 300 to 500
|
|
|
What do the spertmatazoa encounter when they reach the egg?
|
Two barriers: the corona radiata and the zona pellucida
|
|
|
What is released as each sperm approaches the egg?
|
Enzymes are released to break down the corona radiata.
|
|
|
What happens once one sperm cell contacts the edge of the egg cell?
|
The zona pellucida changes consistency so that no other sperm can get through into the egg.
|
|
|
Once the nuclei of the sperm cell and egg cell are nearly united, what happens?
|
Each of the nuclei containing one half of the genetic material duplicates itself into two identical sets of chromosomes and the now fertilised egg cell splits into two cells taking one set of chromosomes from each parent.
|
|
|
When the fertilised egg cell splits into two cells, what is created?
|
A two-celled individual called a zygote.
|
|
|
The formation of the zygote signals the completion of the process of...
|
fertlisation.
|
|
|
What does the zygote do after fertilisation?
|
It travels down the fallopian tube to the uterus to embed itself in the heavy uterine lining.
|
|
|
What creates the uterine lining?
|
The growth and proliferation of vessels and glands.
|
|
|
If the zygote does not imbed in the appropriate part of the uterus, it is called what?
|
An ectopic or abnormally-placed pregnancy.
|
|
|
Once the zygote has reached the two-cell stage, it undergoes a series of mitotic divisions. What is this process called?
|
Mitosis.
|
|
|
What happens as a result of mitosis?
|
There is a rapid increase in the number of cells in the zygote.
|
|
|
What is the zygote still surrounded by while mitosis is happening?
|
The zona pellucida.
|
|
|
What happens as a result of the zygote still being surrounded by the zona pellucida?
|
The cells get smaller and smaller.
|
|
|
After 3 or 4 mitotic divisions, what do we call the zygote?
|
A morula (Latin for mulberry)
|
|
|
At what stage does the zygote become a morula?
|
After about three days, when the zygote is ready to enter the uterus.
|
|
|
How do the cells in the morula organise themselves?
|
Into an inner cell mass surrounded by an outer cell mass.
|
|
|
What will the inner cell mass become?
|
The embryo.
|
|
|
What will the outer cell mass become?
|
It will contribute to the placenta.
|
|
|
What name do we give to the inner and outer cell masses together?
|
A blastocyst (forming cell)
|
|
|
What happens to the inner cell mass (embryoblast) during the second week?
|
It differentiates into two layers, a layer of small cells called the hypoblast and a layer of larger, columnar cells called the epiblast.
|
|
|
What do the hypoblast and epiblast together form?
|
Together they form a flat disc called the bilaminar disc.
|
|
|
What appears at the beginning of the third week?
|
A narrow groove called the primitive streak.
|
|
|
Where does the primitive streak appear?
|
In the caudal half of the epiblast.
|
|
|
What do we call the pit or depression at the cephalic end of the primitive streak?
|
The primitive node.
|
|
|
What are the three germ layers of the embryo called?
|
Mesoderm
Ectoderm Endoderm MEE! |
|
|
What will the ectoderm give rise to?
|
Organs and structures that maintain contact with the outside world like:
central nervous system, peripheral nervous system, sensory epithelium of the ear, nose and eye, epidermis (including hair and nails) subcutaneous glands, mammary glands, pituitary gland, enamel of teeth. |
|
|
What will the mesoderm give rise to?
|
The locomotor system -supportive connective tissues such as:
cartilage and bone, musculature, blood and lymph cells and vessels, kidneys, gonads, cortical portion of the suprarenal gland spleen |
|
|
What will the endoderm give rise to?
|
Primarily the
gastrointestinal (GI) tract or gut |
|
|
What period do we all the embryonic period?
|
The fourth to eighth week
|
|
|
What happens during the embryonic period?
|
The germ layers give rise to the organs and their respective systems.
|
|
|
What is established by the eighth week?
|
All of the organs.
|
|
|
By the end of the third week, some parts of the paraxial mesoderm have begun to form into sections. What are the sections called?
|
Somites
|
|
|
What do we call the normal process by which a cell reproduces itself and becomes two cells?
|
Mitosis
|
|
|
Where do the somites first appear?
|
In the neck region.
|
|
|
In which direction do the somites develop from the neck region?
|
Both cranially and caudally
|
|
|
By the end of the fifth week, how many pairs of somites are there?
|
42 to 44 pairs
|
|
|
How are somites laid down?
|
They are laid down in layers
|
|
|
What is the notochord?
|
A fairly rigid structure that forms the midline axis of the embryo.
|
|
|
What is mesenchyme?
|
A loosely woven tissue which is a kind of embryonic connective tissue.
|
|
|
Once developed and ready for differentiation, what shape is the somite?
|
Triangular.
|
|
|
What portions of the somite differentiate first?
|
The ventral and medial portions.
|
|
|
What do we call the part of the somite that spreads out?
|
The sclerotome.
|
|
|
What does the sclerotome form?
|
Mesenchyme
|
|
|
The sclerotome that surrounds the spinal cord and notochord develops what?
|
The vertebral column.
|
|
|
What happens to each sclerotomic block?
|
The caudal portion of each sclerotomic block proliferates and condenses to meet the cephalic portion of the block below, while the cephalic portion just sort of disappears. In the area where this condensation takes place, the notochord also disappears, and, with ossification, this condenses sclerotomic block becomes the vertebral body.
|
|
|
What forms the tough outer covering of the intervertebral disks, and what do we call the covering?
|
Mesenchyme forms it. We call it the anulus fibrosus.
|
|
|
How are the muscles formed by myotome laid down?
|
In layers (like the sclerotome)
|
|
|
How many bony structures do the paraspinal muscles span?
|
Two.
|
|
|
The fact that the paraspinal muscles attach to two different bones on two different levels makes what possible?
|
Movement
|
|
|
In the trunk, what does the myotome differentiate into?
|
The small dorsal epimere and the larger, surrounding hypomere.
|
|
|
What will the epimere in the trunk differentiate into?
|
Into the extensor muscles of the back.
|
|
|
What will the hypomere in the trunk become?
|
The flexor muscles of the thorax and abdomen.
|
|
|
When do the limb buds become visible?
|
At the beginning of the fifth week.
|
|
|
Where does the upper limb bud lie?
|
Opposite the lower five cervical and upper two thoracic segments.
|
|
|
Where do the lower limb buds lie?
|
Opposite the lower four lumbar and upper two sacral segments.
|
|
|
What do the limb buds initially consist of, and what do they become?
|
A core of mesenchyme and a covering of ectoderm. Then the mesenchyme pushes out and begins to condense into hyaline cartilage models that will later become bones.
|
|
|
When does the ossification of the cartilage in the limb buds into bones begin?
|
By the end of the eighth week.
|
|
|
When does the ossification of the cartilage into bones in the extremities end?
|
Not until early adulthood.
|
|
|
What is necessary for complete functional differentiation of the limb?
|
The nerves
|
