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ل

اهال

اه

اقر لتحرر أمط النص الرئسيالمستوى الثي

● لثلا ىوتسملا●

المستوى الرابع● خلا ىوتسملا

 Derivaties of germ layersEmbryonic period (3-8 weeks)

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المستوى الثياقر لتحرر أمط النص الرئسي● لثلا ىوتسملا

● المستوى الرابع● خلا ىوتسملا

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Derivatives of 

ectoderm1- Surface ectoderm:

Epidermis, hair, nails,cutaneous (sebaceous andsweat) &mammary glands

Anterior lobe of pituitaryEnamel of teeth

The lower half of the anal

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Derivatives of 

ectoderm2.Neuroectoderm derivatives:

A. Neural tube:

C.N.S.Retina

Pineal body

Posterior lobe of pituitary

Iris muscle

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Derivatives of 

ectodermB. Neural crest:

Cranial(5,7,9,10)ganglia, sensory

ganglia and nerves.Medulla od adrenal gland

Pigment cells of dermis, muscle,C.T.Bones of pharyngeal arches

Meninges of brain & spinal cord

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Derivaties of mesoderm

It differentiates into:

1-Paraxial mesoderm gives somites (42-44) . These somites further differentiateinto 3 components:

a- Sclerotome (cartilage and bone)b- Myotome (muscles)

c- Dermatome (dermis of skin)

2-Intermediate cell mass (gives kidneys&

genital system)3-Lateral plate of mesoderm.

 سي

 ئرلا صنلا طمأ ررحتلالمستوى الثي

● لثلا ىوتسملا● المستوى الرابع

● خلا ىوتسملا

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Somites

The total number of somites is 42-44. They aredistributed in the different regions as follows:

4 occipital

8 cervical

12 thoracic

5 lumbar  

5 sacral

8-10 coccygeal

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اقر لتحرر أمط النص الرئسيالمستوى الثي

● لثلا ىوتسملا● المستوى الرابع

● خلا ىوتسملا

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اقر لتحرر أمط النص الرئسيالمستوى الثي

● لثلا ىوتسملا● المستوى الرابع

● خلا ىوتسملا

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Lateral plate of 

mesoderm1. The parietal (somatic) mesoderm:It forms the connective tissue of the lateral and ventral body wall aswell as the parietal layers of the serous membranes (peritoneum, pleuraand pericardium). It also gives rise to the Fallopian tubes, uterus andmost of the vagina.

2. The visceral (splanchnic) mesoderm:

It forms the smooth muscles and connective tissue

of the gut and respiratory organs & the cardiac

muscle and the visceral layers of the serous

membranes.

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Intraembryonic coelom:

Pericardial cavity

Pleural cavities

Peritoneal cavity

Cranial to buccopharyngeal membrane, themesoderm will form the cardigenic plate (future

heart) and septum transversum (futurediaphragm)

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Diferentiation of theintraembryonic mesoderm

The mesoderm is diferentiated into threecolumns on both sides of the notochord &two masses:1- Paraxial mesoderm.2- Intermediate cell mass.3- Lateral plate.

4- septum transversum.5- Cardiogenic plate.

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 Development of the

endodermEpithelial lining of:

Gastrointestinal tract (except the anterior 

 part of the mouth cavity and the lower half of the anal canal).

Respiratory tract.

Most of the urinary bladder and urethra.The tympanic cavity and the Eustachiantube.

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اقر لتحرر أمط النص الرئسيالمستوى الثي

● لثلا ىوتسملا● المستوى الرابع

●

خلا ىوتسملا

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اقر لتحرر أمط النص الرئسي

المستوى الثي● لثلا ىوتسملا

● المستوى الرابع● خلا ىوتسملا

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