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Size

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	==Size==		==Size==
	* Crown Rump Length (CRL) 85 mm (week 10 CRL 40mm), [[F#femur length\|femur length]] 15 mm, [[B#biparietal diameter\|biparietal diameter]] 25 mm
	~~[[File:Fetal_length_change.jpg\|400px]]~~

	\|~~Fetal length change~~		[[File:Fetal_length_change.jpg\|500px]]

	[[File:Fetal_head_growth_circumference_graph02.jpg\|~~400px~~]]		Fetal length change

			[[File:Fetal_head_growth_circumference_graph02.jpg\|500px]]

	Fetal head growth circumference		Fetal head growth circumference


	==Week 16+ (4 months)==		==Week 16+ (4 months)==

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 * Genital male and female external genital differences observable
 * Respiratory Month 3-6 - lungs appear glandular, end month 6 alveolar cells type 2 appear and begin to secrete surfactant
 ==Week 16+ (4 months)==

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Introduction

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	[[File:Ultrasound12wk 3D image.jpg\|thumb\|300px\|3D ultrasound static image of the 12 week fetus]]		[[File:Ultrasound12wk 3D image.jpg\|thumb\|300px\|3D ultrasound static image of the 12 week fetus]]

	* Early fetal - week 12
	* placental changes and fetal membrane changes		* placental changes and fetal membrane changes
	* length changes		* length changes

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Week 12

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 * Respiratory Month 3-6 - lungs appear glandular, end month 6 alveolar cells type 2 appear and begin to secrete surfactant
 ==Week 16+ (4 months)==
 ===Respiratory Development Overview ===

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Created page with "{{ANAT2341Lab11}} ==Introduction== thumb|300px|3D ultrasound static image of the 12 week fetus * Early fetal - week 12 * placental cha..."

New page

{{ANAT2341Lab11}}

==Introduction==

[[File:Ultrasound12wk 3D image.jpg|thumb|300px|3D ultrasound static image of the 12 week fetus]]

* Early fetal - week 12
* placental changes and fetal membrane changes
* length changes
* clinical diagnosis (ultrasound)
* fetal endocrine
* sensory systems
* Genital male and female external genital differences observable
* Respiratory Month 3-6 - lungs appear glandular, end month 6 alveolar cells type 2 appear and begin to secrete surfactant

==Week 12==

<html5media height="420" width="550">File:Ultrasound_Fetus_02.mp4</html5media>

:'''Links:''' [[Ultrasound]]
===Size===
[[File:Fetal_length_change.jpg|thumb|300px|Fetal length change]]
* Crown Rump Length (CRL) 85 mm (week 10 CRL 40mm), [[F#femur length|femur length]] 15 mm, [[B#biparietal diameter|biparietal diameter]] 25 mm
[[File:Fetal_head_growth_circumference_graph02.jpg|thumb|300px|Fetal head growth circumference]]

* Biparietal diameter
* Head circumference
* Abdominal circumference
*Femur length
* Foot length (correlates with CRL)
* Placental parameters (covered in next practical)

===Head===
{|
| [[File:Fetal_head_lateral.jpg|300px]]
| [[File:Fetal head medial.jpg|300px]]
|-
| Fetal head lateral
| Fetal head medial
|}

[[File:Fetal head section 01.jpg|800px]]

* Tongue Week 12 - first differentiated epithelial cells
==Week 16+ (4 months)==
===Respiratory Development Overview ===
[[File:Lung alveoli development cartoon.jpg|thumb|Lung alveoli development cartoon]]
* week 4 - 5 [[R#respiratory embryonic stage|embryonic]]
* week 5 - 17 [[P#pseudoglandular stage|pseudoglandular]]
* week 16 - 25 [[C#canalicular stage|canalicular]]
* week 24 - 40 [[T#terminal sac stage|terminal sac]]
* late fetal - 8 years [[A#alveolar stage|alveolar]]

===Pituitary Development===
* '''Week 4''' - hypophysial pouch, Rathke’s pouch, diverticulum from roof
* '''Week 5''' - elongation, contacts infundibulum, diverticulum of diencephalon
* '''Week 6''' - connecting stalk between pouch and oral cavity degenerates
* '''Week 10''' - growth hormone and ACTH detectable
* '''Week 16''' - adenohypophysis fully differentiated
* '''Week 20 to 24''' - growth hormone levels peak, then decline

===Thyroid Development===
* '''Functions from week10''' - required for neural development, stimulates metabolism (protein, carbohydrate, lipid), reduced/absence = cretinism (see abnormalities)
* '''Hormones''' - (amino acid derivatives) Thyroxine (T4), Triiodothyronine (T3)

[[File:Stage13 and 22 thyroid development a.jpg|thumb|Stage 13 and Stage 22 thyroid development]]
* thyroid median endodermal thickening in the floor of pharynx, outpouch – thyroid diverticulum
* '''24 days''' - thyroid median endodermal thickening in the floor of pharynx, outpouch – thyroid diverticulum
* '''Week 11''' - colloid appearance in thyroid follicles, iodine and thyroid hormone (TH) synthesis
* Fetal Thyroid Hormone
** Initial secreted biologically inactivated by modification, late fetal secretion develops brown fat
** Iodine deficiency- during this period, leads to neurological defects (cretinism)
** Birth - TSH levels increase, thyroxine (T3) and T4 levels increase to 24 h, then 5-7 days postnatal decline to normal levels

:'''Links:''' [[Endocrine - Pituitary Development]] | [http://www.med.unc.edu/embryo_images/unit-nervous/nerv_htms/nerv016.htm Embryo Images - Pituitary] | [[Talk:BGD_Lecture_-_Endocrine_Development#Chapter_7._The_pituitary_gland|Endocrinology]]

=== Skin Development Overview ===
[[File:Fetal_integumentary_histology_01.jpg|800px]]

* '''4 weeks'''
** simple ectoderm epithelium over mesenchyme.

* '''1 - 3 months'''
** ectoderm - germinative (basal) cell repeated division of generates stratified epithelium.
** mesoderm - somite dermatome spreads out under the epithelium, differentiates into connective tissue and blood vessels.
* '''4 months'''
** basal cell - proliferation generates folds in basement membrane.
** neural crest cells - (melanocytes) migrate into epithelium. These are the pigment cell of the skin.
** embryonic connective tissue - differentiates into dermis, a loose ct layer over a dense ct layer. Beneath the dense ct layer is another loose ct layer that will form the subcutaneous layer.
** Ectoderm contributes to nails, hair follictles and glands.
** Nails form as thickening of ectoderm epidermis at the tips of fingers and toes. These form germinative cells of nail field.
** Cords of these cells extend into mesoderm forming epithelial columns. These form hair follicles, sebaceous and sweat glands.
* '''5 months'''
** Hair growth initiated at base of cord, lateral outgrowths form associated sebaceous glands.
** Other cords elongate and coil to form sweat glands.
** Cords in mammary region branch as they elongate to form mammary glands. These glands will complete development in females at puberty. Functional maturity only occurs in late pregnancy.

:Links: [[Integumentary System Development]]

===Genital Development===
Genital male and female external genital differences observable. In the ovary primary follicles begin to form and are characterized by the developing oocyte.

The animations below shows the development of external female and male genitalia from the indifferent external structure, during the period of week 9 to 12. Note - this content will be covered in detail in BGDB Genital development.

{|
| valign="bottom"|{{Female external movie}}
| valign="bottom"|{{Male external movie}}
|}

[[Template:Genital cartoons|All Genital cartoons]]
===Sensory Development===
* '''Hearing''' - middle ear bones (ossicles) - not free to move until birth.
* '''Vision''' - months 3 to 4 retina development, eyelids closed (until 5-7 months), lens grows through third trimester, cannot focus even postnatally.

==Ultrasound==
===About Ultrasound===
Different body tissues reflect sound waves differently. In ultrasound, a beam of sound waves (frequency 3 to 10 MHz) are passed through the body, the reflected waves are analysed by a computer, and an image is then generated on a display screen. The sound source is usually a transducer placed on the surface of the abdomen.

===Ultrasound Measurements===
There can be number of different parameters, depending on gestational age, that are commonly recorded during an ultrasound procedure. These measurements (and ratios) include embryonic/fetal size and key lengths and sizes of specific structures, fetal membrane sizes/volumes, placental location/size. In addition, general body movements, including heartbeat, can be observed.

{|
| [[File:Ultrasound_-_fetal_abdominal_circumference.jpg|500px|Ultrasound Fetal (GA 19 weeks)
Ultrasound scan through the fetal trunk to measure abdominal circumference (AC).]]
|-
| Ultrasound Fetal (GA 19 weeks)
Ultrasound scan through the fetal trunk to measure abdominal circumference (AC).
|}

[[File:Placental_cord_knot.png|thumb|placental cord knot]]

'''Embryonic/Fetal Size:''' crown-rump length (CRL), biparietal diameter (BPD), abdominal circumference (AC)

'''Embryonic/Fetal Structures:''' femur length (FL), head circumference, nuchal translucency, heart size/rate

'''Fetal Membrane:''' gestational sac diameter (GS), yolk sac diameter (YS), meconium peritonitis, umbilical cord stricture

'''Placenta:''' location, size, umbilical cord stricture

===Ultrasound - Abnormalities===
<gallery>
File:Cleft_lip_01.jpg|Cleft lip 1
File:Cleft_lip_100.jpg|Cleft lip 1 measurement
File:Cleft_lip_03.jpg|Cleft lip 2
File:Gastroschisis_01.jpg|Gastroschisis
</gallery>

See Ultrasound movie for [[Ultrasound_-_Cleft_Lip_01|Cleft lip 1]]

===Second Trimester Brain Growth===

[[File:Brain_fissure_development_02.jpg]]

At about 19 weeks ({{GA}} 21 weeks) neuronal migration ends and the radial glial cells, that aided this migration, now become transformed into astrocytes and astrocytic precursors.<ref><pubmed>3339373</pubmed></ref>

:'''Links:''' [[Neural System - Glial Development|Glial Development]]
==Additional Information==
{{Med Prac additional Information}}

{{Ultrasound Movies}}

===Second Trimester Intestinal Growth===
Both the small and large intestine grow in a linear manner during the second trimester.<ref><pubmed>3244599</pubmed></ref><ref><pubmed>16891202</pubmed></ref>

[[File:Fetal_small_Intestine_length_growth_graph.jpg|600px]] [[File:Fetal_large_Intestine_length_growth_graph.jpg|600px]]

=== Second Trimester ===
(Clinical Week 14) [[Second Trimester]]

{| class="prettytable" width=100%
|-bgcolor="#AFEEEE"
| <center>'''Week'''</center>
| <center>'''Stage'''</center>
| '''Event'''

|-bgcolor="#AFEEEE"
| <center>12</center>
| Clinical second trimester
| [[File:Fetal_head_lateral.jpg|90px|link=Fetal Development]] Week 12 - CRL 85 mm, femur length 15 mm, biparietal diameter 25 mm

[[Sensory_-_Hearing_and_Balance_Development|Hearing]] Week 12-16 - Capsule adjacent to membranous labrynth undegoes vacuolization to form a cavity (perilymphatic space) around membranous labrynth and fills with perilymph

[[Genital_System_Development|Genital]] male and female external genital differences observable

[[Respiratory_System_Development|Respiratory]] Month 3-6 - lungs appear glandular, end month 6 alveolar cells type 2 appear and begin to secrete surfactant

[[Tongue_Development|Tongue]] Week 12 - first differentiated epithelial cells (Type II and III)

[[Genital_System_Development|Genital]] female genital canal (80 days) formed with absorption of the median septum

|-
| <center>13</center>
|  
| [[Tongue_Development|Tongue]] Week 12 to 13 - maximum synapses between cells and afferent nerve fibers

[[Hearing_-_Outer_Ear_Development|Hearing - Outer Ear Development]] Week 13 - Meatal plug disc-like, innermost surface in contact with the primordial malleus, contributes to the formation of the tympanic membrane.
 

|-bgcolor="#AFEEEE"
| <center>14</center>
|
| [[Tongue_Development|Tongue]] Week 14 to 15 - taste pores develop, mucous

[[Ovary Development]] 100 days - primary follicles present

[[Integumentary_System_-_Nail_Development|Nail Development]] toenails appear

[[Head Development]] facial skeleton remodelling begins

|-
| <center>15</center>
|  
| [[Endocrine_-_Pancreas_Development|Pancreas]] glucagon detectable in fetal plasma.

[[Cardiovascular_System_-_Spleen_Development|Spleen]] Week 15 -alpha-smooth muscle actin (alpha-SMA)-positive reticulum cells scattered around the arterioles. <ref name="PMID19255788"><pubmed>19255788</pubmed></ref>

===Fetal Timeline===

|-bgcolor="#AFEEEE"
| <center>16</center>
| 14 cm
| [[File:Fetal_size_change.jpg|90px|link=Fetal Development]] [[Sensory_-_Hearing_and_Balance_Development|Hearing]] Week 16-24 - Centres of ossification appear in remaining cartilage of otic capsule form petrous portion of temporal bone. Continues to ossify to form mastoid process of temporal bone.

[[Endocrine_-_Pituitary_Development|Pituitary]] adenohypophysis fully differentiated

[[Respiratory_System_Development|Respiratory]] Week 16 to 25 lung histology - canalicular

[[Hearing_-_Outer_Ear_Development|Hearing - Outer Ear Development]] Week 16.5 - External auditory meatus is fully patent throughout its length, lumen is still narrow and curved.

[[Integumentary_System_Development|Skin]] 4 months - basal cell- proliferation generates folds in basement membrane; neural crest cells- (melanocytes) migrate into epithelium; embryonic connective tissue- differentiates into dermis, a loose ct layer over a dense ct layer. Beneath the dense ct layer is another loose ct layer that will form the subcutaneous layer. Ectoderm contributes to nails, hair follictles and glands. Nails form as thickening of ectoderm epidermis at the tips of fingers and toes. These form germinative cells of nail field. Cords of these cells extend into mesoderm forming epithelial columns. These form hair follocles, sebaceous and sweat glands.

primary follicles begin to form in the ovary and are characterized by an oocyte

glandular urethra forms and skin folds present

|-
| <center>17</center>
|
| [[File:Brain_week_17_histology.jpg|90px]] [[Neural System Development|Neural]] - Brain development histology week 17

|-bgcolor="#AFEEEE"
| <center>18</center>
|
| [[File:Bailey095.jpg|90px]][[Tongue_Development|Tongue]] Week 18 - substance P detected in dermal papillae, not in taste bud primordia

[[Integumentary_System_Development|Skin]] vernix caseosa covers skin

[[Cardiovascular_System_-_Spleen_Development|Spleen]] Week 18 - alpha-SMA-positive reticulum cells increase in number and began to form a reticular framework. An accumulation of T and B lymphocytes occurred within the framework, and a primitive white pulp was observed around the arterioles. <ref name="PMID19255788"><pubmed>19255788</pubmed></ref>

[[Hearing_-_Outer_Ear_Development|Hearing - Outer Ear Development]] week 18 - External auditory meatus is already fully expanded to its complete form.
|-
| <center>19</center>
|  
|  

|-bgcolor="#AFEEEE"
| <center>20</center>
|  
| [[Endocrine_-_Pituitary_Development|Pituitary]] week 20 to 24 growth hormone levels peak, then decline

[[Integumentary_System_Development|Skin]] lanugo, skin hair

[[Integumentary_System_Development|Skin]] 5 months - Hair growth initiated at base of cord, lateral outgrowths form associated sebaceous glands; Other cords elongate and coil to form sweat glands; Cords in mammary region branch as they elongate to form mammary glands.

|-
| <center>21</center>
|  
|  

|-bgcolor="#AFEEEE"
| <center>22</center>
|  
| [[File:Gray0038.jpg|90px|link=Fetal Development]] [[Neural System Development|Neural]] brain cortical sulcation - sylvian fissure, interhemispheric fissure, callosal sulcus, parietooccipital fissure, and hippocampic fissures present<ref name="PMID11158907"><pubmed>11158907</pubmed></ref>
[[Cardiovascular_System_-_Spleen_Development|Spleen]] - Week 22 - antigenic diversity of the reticular framework was observed, and T and B lymphocytes were segregated in the framework. T lymphocytes were sorted into the alpha-smooth muscle actin-positive reticular framework, and the periarteriolar lymphoid sheath (PALS) was formed around the arteriole. B lymphocytes aggregated in eccentric portions to the PALS and formed the lymph follicle (LF). The reticular framework of the LF was alpha-SMA-negative. <ref name="PMID19255788" />
|-
| <center>23</center>
|  
|  

|-bgcolor="#AFEEEE"
| <center>24</center>
|  
| [[Respiratory_System_Development|Respiratory]] Week 24 to 40 lung histology - terminal sac
[[Cardiovascular_System_-_Spleen_Development|Spleen]] Week 24 - marginal zone appeared in the alpha-smooth muscle actin-positive reticular framework around the white pulp.<ref name="PMID19255788"><pubmed>19255788</pubmed></ref>

Earliest potential survival expected if born

ovarian follicles can consist of growing oocytes surrounded by several layers of granulosa cells

|-
| <center>25</center>
|  
| [[Respiratory_System_Development|Respiratory]] end month 6 alveolar cells type 2 appear and begin to secrete surfactant

|}

==References==

<references/>

{{ANAT2341Lab11}}

[[Category:Second Trimester]]

ANAT2341 Lab 11 - Second Trimester - Revision history

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Z8600021: /* Introduction */

Z8600021: /* Week 12 */

Z8600021: Created page with "{{ANAT2341Lab11}} ==Introduction== 3D ultrasound static image of the 12 week fetus * Early fetal - week 12 * placental cha..."