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Pediatrics > test 2 > Flashcards

test 2 Flashcards

1
Q

Fertilization occurs where

A
  • ampullary region of the fallopian tube
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2
Q

Sperm + Oocyte =

A

Zygote

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3
Q

Reaches 2 cell stage about how long after fertilization

A
  • 30 hours post fertilization

- happens in fallopian tube

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4
Q

Reaches 4 cell stage about how long after fertilization

A
  • 40 hours

- happens in Fallopian tube

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5
Q

Reaches 12-16 cell stage about how long after fertilization

A
  • 72 hours (3 days)

- happens in Fallopian tube

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6
Q

mitotic divisions

A

 Series of mitotic divisions occurs.
 Cells increase in number
 Become smaller with each division
 Cells are called BLASTOMERES

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7
Q

8 cell stage

A

 Cells are loosely arranged until 8 cell stage.
 After the 3rd cleavage, cells have maximized contact with each other.
 Start to undergo compaction
 Cells separate into inner and outer cells.

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8
Q

16 cell stage

A

 called a MORULA
 Had defined inner and outer cells.
 Inner cells = inner cell mass (will become the embryo)
 Outer cells = outer cell mass (will become the trophoblasts, which will be the placenta)

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9
Q

What happens when the morula makes wits way into the uterus

A 
 Fluid penetrates into the intercellular spaces of Inner Cell Mass.
         Spaces become a single cavity
                 BLASTOCELE
 Enlarges and becomes a BLASTOCYST
         Embryo is called a Blastocyst
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10
Q

Early Embryonic Development process (6 steps)

A
  1. fertilization (12-24 hours after ovulation)
  2. cleavages (first cleavage completed about 30 hours after fertilization)
  3. Morula (3-4 days after fertilization)
  4. Blastocyst (4.5-5 days after fertilization)
  5. Implantation (6 days after fertilization)
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11
Q

Blastocyst is comprised of:

A

 Trophoblast – outer covering
 Formed from cells of the outer cell mass.
 Cells flatten and eventually form the epithelial wall of the blastocyst
 Blastocele – Internal fluid filled space
 Embryoblast – Inner cell mass
 Located at one pole

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12
Q

Trophoblast and part of inner cell mass will become and the rest of the inner cell mass will become?

A
  • the placenta

 Rest of inner cell mass will become the embryo

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13
Q

Around day 6 after fertilization

A

 implantation occurs
 Trophoblastic cells over the embryoblast pole penetrate between the epithelial cells of the uterine wall.
 L-Selectin (Trophoblasts) and carbohydrate receptor on uterine epithelium mediate attachment and capture of the capture and holding of the leukocytes from the blood onto the endothelial cells
 Blastocyst remains free in the uterus for 2 days

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14
Q

Blastocyst attaches to

A

 uterine epithelium, and subsequently the endometrium

 Oriented so the inner cell mass is near the endometrium

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15
Q

At day 8

A
  • the Blastocyst is partially embedded
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16
Q

The Trophoblast cells over the embryoblast differentiate into 2 layers:

A

 Syncytiotrophoblast – multi-nucleated, outer zone
 no cell boundries
 Cytotrophoblast – mononucleated cells, inner layer (look like normal cells)
 distinct cells
 Cells from cytotrophoblast divide and migrate into the syncytiotrophoblast
 Fuse and lose individual cell membrane – multi-nucleated
 Both layers become part of the chorion (one of the fetal membranes)

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17
Q

Inner cell mass –embryoblast, differentiates too

A

 Hypoblast layer (Entoderm)
 Layer of small cuboidal cells adjacent to the blastocyst cavity
 Epiblast layer (Ectoderm)
 Layer of high columnar cells adjacent to amniotic cavity
 Forms a flat disc
 Small cavity appears within the epiblast
 Enlarges to become amniotic cavity

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18
Q

Day 11-12

A

 Completely embedded
 Cells of the Synctiotrophoblast penetrate deeper into endothelial lining of maternal capillaries
 Capillaries are congested and dilated
 Called SINUSOIDS
 Causes blood to flow through the trophoblastic system
 Beginning of the uteroplacental circulation (primitive placenta)

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19
Q

Cytotrophoblast proliferates to form:

A

 Amnion
 Thin Protective membrane that surrounds the developing embryo.
 Amniotic Cavity
 Space, eventually filled with fluid.

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20
Q

What starts at day 8

A

 GASTRULATION: Process for establishing 3 germ layers
 Inner cell mass differentiates into:
 Ectoderm
 Endoderm
 Mesoderm
 These are the major embryonic tissues from which all tissues and organs of the body develop.

21
Q

Gastrulation: Cells of the epiblast migrate to the primitive streak

A

 Regulated by fibroblast growth factor 8 (FGF8)
 Made by streak cells
 Down-regulated with E-Cadherin (causing things to be loose)
 Protein normally holds epiblasts together
 Loss of E-Cadherin allows cells to detach and move
 Arrive and become “flask-like”
 Detach from epiblast and slip beneath it
 Epiblast is the source of the germ layers.
 Inward movement / cause invagination
 Cells displace the hypoblast
 Creates Endoderm
 Others lie between the epiblast and the new endoderm
 Mesoderm
 Cells remaining in the epiblast
 Ectoderm

22
Q

Around 14 days after fertilization after gastrulation

A

 Inner Cell Mass now called an Embryonic Disc as amniotic cavity starts to form.
 Ectoderm – Layer of cells of the inner cell mass closest to the amniotic cavity.
 Endoderm – layers of inner cell mass that borders the blastocele.
 Mesoderm – Lies between the ectoderm and endoderm.

23
Q

Ectoderm Becomes:

A

 Skin, teeth, mouth glands, nervous system, some endocrine glands.

24
Q

Endoderm Becomes:

A

 Epithelium of digestive tract, respiratory system, bladder, reproductive organs, urethra

25
Q

Mesoderm Becomes:

A

 All connective tissue, the muscular, skeletal, lymphatic, and circulatory systems.

26
Q

Cardiovascular system development

A

 Cardiovascular System appears in the middle of the 3rd week.
 At this point the embryo is no longer able to survive via diffusion alone.
 The Cardiovascular System reaches a functional state long before any of the other systems
 Vascular system develops from a simple symmetrical plexus, into an asymmetrical complex system
 The size of the embryonic heart in relation to the size of the embryo is enormous compared to an adult heart in an adult size body.

27
Q

Progenitor Heart Cells

A

 Day 16-18
 Lie in the Epiblast.
 Adjacent to the cranial end of the primitive streak
 Move through the streak and into the splanchnic layer of the mesoderm.
 Form a horse-shoe shaped cluster of cells called the Primitive Heart Field (PHF)
 Will form blood islands and cardiac myoblasts
 These will form blood cells and blood vessels.
 Blood islands unite and form a horse-shoe shaped tube
 Endothelial cell lined
 Surrounded by myoblasts

28
Q

First parts of the heart to show up (from primary heart field cells) (set up the sturcture)

A
  • Specified on both sides
    • Atria
    • LV
    • RV (part of it)
29
Q

Day 20-21 secondary heart field cells develop and add to (part of the growth and development of the heart tube and heart itself)

A 
• RV
• Conus Cordis
• Truncus Arteriosus
• Lengthen outflow tract
• Also have laterality
        • Those on right side add to left side of heart tube
        • Those on left side add to the right side of heart
tube.
30
Q

Serotonin (5HT)

A

 Serotonin (5HT) initiates the R/L patterning
 Concentrated on the LEFT side
 Degrading enzyme (Monoamine Oxidase) is in high concentrations on the RIGHT side
 Leads to expression of the PITX2 gene (master gene for the LEFT side)
 All occurs about day 16-18 – critical for heart development

31
Q

Intraembryonic Celom (Body Cavity)

A

 Formed by the joining of small (initially isolated) spaces which appear in the lateral mesoderm
 Bilateral cavities extend cranially and fuse with each other forming a horseshoe-shaped cavity
 Eventually becomes the pericardial cavity

32
Q

Blood Islands

A

 Heart development starts at the end of the 3rd week of gestation.
 Occurs in the ventral region of the embryo, inferior to the foregut.
 Scattered masses of angiogenic cells appear in the mesenchyme derived from PHF
 Occurs ventral (in front of) the intraembryonic celom.
 Anterior part of the celom will develop the pericardial cavity

33
Q

Endocardial Tube Formation

A

 Angiogenic cells form clusters (Blood Islands) which increase in size and number.
 Acquire a lumen, unite and form a plexus of blood vessels
 From this plexus, bilateral endocardial tubes develop.
 The Endocardial tubes unite to form a common
tube
 Primitive Heart Tube

34
Q

Day 21-22

A

 the single heart tube starts to beat

35
Q

Formation of the Heart Tube

A

 Heart tube continues to elongate
 Cells are added from the secondary heart field to the cranial end of the tube
 Process is essential for normal formation of part of the RV, the Conus Cordis (RV outflow) and the Truncus Arteriosus (LV outflow)
 Also essential for looping
 If lengthening doesn’t occur, where outflow tract defects come from

36
Q

Dorsal Aortas

A

 Meanwhile, Other blood islands appear inferior (below) to the endocardial tubes
 Eventually give rise to dorsal aortas.
Will connect with the endocardial tubes
Establish the arterial end of the heart
 Other end of the future endocardial tubes will make contact with the vitelline veins (via the sinus venosus) and establish a venous pole.

37
Q

Day 23 after the tube starting to beat

A

 Newly formed heart tube starts to bend
 Cephalic part bends ventrally, caudally, and to the right.
 Caudal part bends dorsocranially, and to the left.
 Bulges into the pericardial cavity
 Attached to dorsal wall by mesoderm
 Mesoderm eventually ruptures
 Leaves heart tube suspended in pericardial cavity

38
Q

Dorsal Aorta and Aortic

Sac Becomes

A
  • common outflow tract
39
Q

Bulbus Cordis becomes

A
  • Primitive RV
40
Q

Primitive Ventricle becomes

A
  • Primitive LV
41
Q

Atrioventricular Sulcus becomes

A
  • Divides atria from

ventricles

42
Q

Paired Primitive Atria becomes

A
  • Will form common atria
43
Q

Sinus Venosus becomes

A
  • Eventually forms the coronary sinus and oblique vein of the LA
44
Q

Heart Folding

A

 Day 23-28 (TAKES 5 DAYS)
 Heart undergoes a series of folding that leads to the formation of the bulboventricular loop.
 Heart Tube grows rapidly in length, especially the midsection (Bulbus Cordis and Ventricle)
 Because the two ends are fixed, heart tube is forced to bend in order to adapt itself to the pericardial space causing:
 Forms a U-Shape
 Then Forms an S-Shape
 Oriented so that the atrium and sinus venosus lie superior to the bulbus cordis, ventricle and dorsal aorta/aortic sac

45
Q

What happens to the comparments after heart folding?
atria
Atrioventricular juntion
bulbus cordis

A

 Atria initially paired – forms common atrium
 Atrioventricular junction remains narrow
 Forms AV Canal – connects common atrium and ventricle.
 Bulbus Cordis is narrow, except proximal 1/3
 Will form trabeculated part of RV

46
Q

Junction between the ventricle and the bulbus cordis externally is the?

A

 bulboventricular sulcus
Remains narrow
Called the primary interventricular foramen

47
Q

Heart Folding – Atrium

A

 Atrial portions of the Heart Tube dilate
 Form Common Atrium
 Atrium “climbs up” the dorsal pericardial wall
 Takes Atrioventricular junction with it
 Atrioventricular junction remains narrow
 Now called AV Canal
 Forms the communication between the atrium and the primitive ventricle.

48
Q

Heart Folding - Ventricle

A

 Ventricle also dilates
 Acquires a larger lumen
 Junction of the ventricle and the bulbus cordis remains narrow
 Junction is now called the intraventricular foramen

49
Q

Heart Folding – Bulbus

Cordis

A

 Further dilation of the bulbus cordis

 Lies on top of and in between the atrium

Pediatrics (37 decks)

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