Download Development of somites

Bi-Ismi-ALLAH-Arehman-Araheem
MUDGHAH
(Chewed Substance)
O people, if you have any doubt about Life-after-death,
you should know that WE first created you of clay, then
of a sperm-drop, then of a clot of blood, then a lump of
flesh, shaped or shapeless. (WE are telling you this) so
that WE make the reality plain to you.
And WE cause whom WE will to remain in the wombs
for a fixed period, then WE bring you out as an infant;
then (WE nourish you) so that you may attain to your full
youth. And there may be among you one who is
returned to the most abject/miserable age so that he
should know nothing even after knowing all he could.
And you see the land lying dry and barren, but as soon
as WE send down rainwater upon it, it stirs (to life), and
swells and brings forth every kind of luxuriant vegetation.
• This is so because ALLAH is the Truth. HE
brings the dead to life and HE has power over
everything and (This is a proof that) the Hour of
Resurrection is sure to come and there is
absolutely no doubt about it, and most surely
He will raise up those who are lying in the
graves.
Al-Hajj. Surah 22, Ayat 5-7, Para 18.
Mudghah as described in
Surah Al-Hajj is of two types:
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Shapeless Mudghah refers to the somite
stage of the embryo. It starts on 20th day
when first pair of somites appears and
ends on 35th day when all the somites
have developed. It is mostly 4th and 5th
weeks.
Shaped Mudghah is from 6th week to 8th
week.
Shapeless Mudghah
Somite Stage
4th to 5th week of intrauterine life
Development
of somites
• Dorsum of human
embryo, 2.11 mm in
length.
• (The older term
'primitive segments' is
used to identify the
somites.)
Day-17
Transverse section of trilaminar germ disc.
Day-19
Three main parts of intraembryonic mesoderm.
• 20-day
• Three main parts of intraembryonic mesoderm.
• See the segments of paraxial mesoderm.
Day-20. Paraxial mesoderm
begins to divide into paired
cuboidal bodies called somites.
First pair of somites arises in the
cervical region of embryo.
Subsequent pairs form in a
craniocaudal sequence.
About 3 pairs of somites form daily
during the so-called somite period (20
to 30 days)
Eventually by the end of 5th week, 42
to 44 pairs are present.
The first occipital and the caudal 5 to
7 coccygeal somites disappear.
Week 4
Week 5
• The somites give rise to most of
the axial skeleton, associated
musculature and the dermis of the
skin.
• During the somite period, the
somites are used as one of the
criteria for determining the
embryo’s age.
INTRAEMBRYONIC COELOM
• Day 19. A number of small, isolated coelomic
spaces appears within the lateral plate
mesoderm and the cardiogenic mesoderm.
• Day-20. These spaces soon coalesce to form a
horseshoe-shaped cavity the intraembryonic coelom,
• It is lined by flattened epithelial cells.
• Laterally communicates with extra-embryonic coelom.
• The intraembryonic coelom divides
the lateral plate mesoderm into two
layers:
1. Somatic (parietal) layer continuous
with the extraembryonic mesoderm
covering the amnion.
2. Splanchnic (visceral) layer continuous
with the extraembryonic mesoderm
covering the yolk sac.
Transverse section of day-21 embryo showing
intermediate mesoderm clearly defined. Paraxial
mesoderm has formed somites. One somite is visible
in this cross section. Lateral plate mesoderm has
become divided into two layers.
• The somatic mesoderm and the overlying
embryonic ectoderm form the body wall, or
somatopleure, whereas the splanchnic
mesoderm and the embryonic endoderm form
the splanchnopleure, or wall of the primitive gut.
• During the second month, the intraembryonic
coelom is divided into the body cavities:
– one pericardial cavity
– the two pleural cavities
– one peritoneal cavity
Fourth Week
• Major changes in the body form occur
during fourth week.
• At the beginning, the embryo (2.0 to 3.5
mm long) is almost straight and has 4 to
12 somites that produce conspicuous
surface elevations.
• The neural tube is formed between right
and left chains of somites.
• Pharyngeal (branchial) arches are visible.
• The embryo is now slightly curved because of
the head and tail folds. The heart produces a
large ventral prominence and pumps blood.
• The forebrain produces a prominent elevation
of the head, and folding of the embryo has
given the embryo a characteristic C-shaped
curvature. A long, curved tail is present.
• Upper limb buds become recognizable by day
26 or 27 as small swellings on the ventrolateral
body walls.
• The otic pits, the primordial of the internal ears, are
also visible.
• Ectodermal thickenings indicating the future lenses of
the eyes called lens placodes are visible on the sides
of the head.
• The fourth pair of pharyngeal arches and the lower
limb buds are visible by the end of the fourth week.
• Toward the end of the fourth week, an attenuated tail
is a characteristic feature.
• Rudiments of many of the organ systems, especially
the cardiovascular system, are established.
• By the end of the fourth week the caudal neuropore is
usually closed.
Fifth Week
• Changes in body form are minor during
the fifth week compared with those that
occurred during the fourth week, but
growth of the head exceeds that of other
regions. Enlargement of the head is
caused mainly by the rapid development
of the brain and facial prominences. The
face soon contacts the heart prominence.
• The rapidly growing second (hyoid) pharyngeal
arch overgrows the third and fourth arches,
forming a lateral ectodermal depression on
each side – the cervical sinus.
• The upper limb buds are paddle-shaped and
the lower limb buds are flipper like.
• The mesonephric ridges indicate the site of the
mesonephric kidneys, which are interim kidneys
in humans.
Derivatives of Ectoderm
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Central and Peripheral Nervous System
Epidermis of the skin, including hair and
nails.
Sensory epithelium of ear, nose and eye
Anterior two third of oral cavity.
External and Internal ear.
Lens of the eye.
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Muscles of iris
Pituitary gland
Medulla of the Suprarenal gland
Subcutaneous glands
Mammary gland
Enamel of the teeth
All the five special senses develop from
ectoderm.
Derivatives of Mesoderm
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Connective tissue (all types including cartilage
and bone)
Muscles (all types), except the muscles of iris
Joints (all types)
Fascia (all types), Intermuscular septa,
Retinaculae etc. (these are connective tissues)
Dermis of the skin connective tissue
Urogenital system (except the epithelial lining
of urinary bladder and urethra).
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Cardiovascular system, including blood and
lymph
Body cavities.
Respiratory and Alimentary tract; except their
epithelial linings
Stroma of salivary glands, liver and pancreas
Stroma of thyroid and parathyroid glands
Spleen, Lymph nodes and Tonsils
Cortex of the Suprarenal gland
Derivatives of Endoderm
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Epithelial lining of Gastro-intestinal tract
Respiratory tract (Epithelial liningonly)
Parenchyma of salivary glands, liver and
panceas.
Parenchyma of thyroid and parathyroid glands
Reticular stromaof tonsils and thymus
The epithelial lining of urinary bladder and
urethra
The epithelial lining of tympanic cavity and
Eustachian tube