Embryology Unit 2 Test Flashcards
Fertilization of the female egg by the male sperm takes place where
Distal 1/3 rd of Fallopian tubes (ampulla)
What occurs while the fertilized egg is traveling down the uterine tube
Divides by 2^n
How long does it take for the fertilized egg to reach the uterus
7 to 8 days, one week
During fertilization, the sperm penetrates what
The mature ovum
The sperm and egg fuse to form what
The zygote
How many chromosomes in the egg
23
How many chromosomes in sperm
23
How many chromosomes in zygote
46
What does the egg release when in the uterus to help penetrate the endometrial lining
Proteolytic enzyme
When does the embryo begin to develop
After penetrating the endometrium of the uterus and the hole closes up
What is ectopic pregnancy
When the embryo develops outside of the uterus
What are the first two main structures to begin developing in embryo
Spine (nervous system) and heart (vascular system)
What is the germ disc
The round egg in the endometrial layer that flattens out
What is the neural streak
The ectodermal floor of the amniotic cavity thickens and the center of the midline creases
What is the neural groove
The neural streak invaginates (folds in)
What is the beginning of the overall nervous system in the embryo
Neural groove
What is the mesoderm
Middle embryonic layer of tissue
The mesoderm surrounds what
The amniotic cavity
Where does the mesoderm come together
Under or anterior to the neuroectoderm tissue
The mesoderm becomes what
The cephalad (head) portion of the embryo
Another name for the cephalad head formed by mesoderm
Primitive node or hensen’s node
Function of notochord
Form the guid for further spinal development
How does the notochord form
From hensen’s node, cells migrate or elongate to the causal forming the notochord
Other name for notochord
Chorda dorsalis
When does the spine form in the embryo
2nd embryonic week between the 10th and 14th day
What mesodermal cells line up on either side of the notochord as spine forms
Somites
How many pairs of somite pairs of notochord
42 to 44
The somites eventually become what
Vertebral bodies
The first four pairs of somites become
The occipital
The 7 pair become what
Cervical vertebrae
12 pair will become
Thoracic vertebrae
5 pair will become the
Sacral segments
8 to 9 pair will become
Coccygeal segments
Any remaining pairs of somites will become
Absorbed or disappear
The neural crest cells will into what
The posterior dorsal root ganglion and spinal nerves, ganglia of the cranial nerves, cranial nerves, ganglia of the autonomic nervous system, adrenal medulla, meninges of the spinal cord and brain, meisner’s and auerbauch’s plexus.
What happens to the somites of the third embryonic week
Somites will split in their center at an area called the fissure of von bender
What happens to the superior half of the somites
Move cephalad and unite with the inferior half of the somite migrating caudad
What will happen to the inferior half of the somite
Will move caudad and unite with the superior half of the somite below the migrating cephalad
What is the sclerotome
The superior portion of one half somite fused with and the inferior portion of one half of another somite
Myotomes are
Somites for muscles
Dermatomes are what
Somites for skin
What is a mesenchyme
Rest of connective tissue
During the 4th embryonic week, what happens to the sclerotomes
Change into cartilage
After the sclerotomes change into cartilage, the cartilage surrounds what
The notochord
After the cartilage surrounds the notochord during the 4th embryonic week, what happens
Squeezes the notochord causing it to push superiorly and inferiorly
The squeezed notochord will bunch up between the cartilage and will become what
Part of the nucleleus pulposis of the intervertebral disc
What are the three stages of vertebral development
Mesenchymal stage, chondrification, ossification
What is the alternative name of mesenchymal stage
Primordial or primordium stage
What occurs during the mesenchymal stage
Beginning of vertebral development, somites form and sclerotomes develop
When does the mesenchymal stage occur
Last from the second to third embryonic week
When does the chondrification stage occur
Begins the fourth embryonic week
Where does chondrification stage occur
Begins overall in the cervicothoracic region then proceeds upward and downward
Chondrification begins in what number of ares of the vertebra
4
What are the four areas of the vertebra the chondrification occurs
1 in each half of the vertebral arch (pedicolaminal junction)
1 in each Half of the vertebral body, on each side of notochord
What occurs during the 6th embryonic week in the chondrification stage
2 more centers will develop at what will be the TVP area
what is stage three of the vertebral development
ossification (bone forming)
when does the ossification stage begin
7th and 9th embryonic week
ossification of the vertebral bodies begins where
the thoracolumbar areas of the spine and proceed upwards and downwards
ossification of the vertebral arches begins where
at the cervicothoracic regions of the spine and proceeds upward and downward
what are the two types of ossification
primary and secondary
what is primary ossification
begins prior to birth but may not complete till after birth
what is secondary ossification
begins after birth
when does secondary ossification usually occur
between ages 12 - 20
how many primary ossification centers in the atlas (C1)
three
what are the three primary ossification centers in C1
one in each lateral mass (2), one in the anterior arch
the axis is also known as
C2 or epistropheus
how many primary ossification centers in C2
5
how many secondary ossification centers in C2
2
Where are the primary ossification centers in C2
1 in each half of the vertebral arch (2), 1 in center of vertebral body, 2 at the base of the odontoid process
when does the secondary ossification centers in C2 begin and end
age 2 to 12
where are the secondary ossification centers in C2
one located in the apex of the odontoid process, one located at the bottom of the anterior portion of the body called the anterior inferior lip
what is persistant epiphysis
any failure of fusion of an ossification center, either primary or secondary
what is os odontoidium
failure of fusion of the primary center of ossification in which the odontoid process fails to fuse with the body of the axis
what is os terminale
failure of fusion of the secondary center of ossification in which the tip (apex) of the odontoid fails to fuse with the rest of the odontoid (dens) process
how many total ossification centers in C3 through T12
8 in each vertebrae
how many primary ossification centers in C3 through T12
3
what are the primary ossification centers in C3 through T12
one in center of each vertebra, one in each half of the posterior arch
how many secondary ossification centers in C3 through T12
5
what are the secondary ossification centers in C3 through T12
one in each epiphyseal plate (2), one in tip of each transverse process (2), one in tip of spinous process
how many total ossification centers in the lumbar region
10
how many primary ossification centers in lumbar
5
what are the primary ossification centers in lumbar
one in center of vertebral body, one in each half of vertebral arch, one in each mamillary process
how many secondary ossification centers in the lumbar
5
what are the secondary ossification centers in the lumbar
one in each epiphyseal plate, one in each transverse process, one in tip of SP
how many total centers of ossification in sacrum
49
how many primary ossification centers in sacrum
37
how many secondary ossification centers in sacrum
12
how many total ossification centers in coccyx
4
how many primary ossification centers in coccyx
4
how many secondary ossification centers in coccyx
zero
when do the primary ossification centers in the coccyx develop
develop one every 5 years and will be fused between ages 25 to 30
