i want 25 multiple choice questions with their model answer below each question about Basic Medical Science I Anatomy
Module
General EmbryologyGeneral EmbryologyObjectives
By the end of this lecture student should be able to:
Study the embryonic period
(3rd to 8th week)
(derivatives of the mesoderm)Contents
- Derivatives of the mesoderm:
- Lateral plate mesoderm
- Intermediate mesoderm
- Paraxial mesodermThe mesodermal layerThe mesoderm
17 days
-The cells of the
mesodermal germ
layer form a thin
sheet on each side
of the midline.
(Arrows)
Amniotic cavity
Yolk sacThe mesoderm
19 days
The mesodermal sheets
differentiate into:
1- Paraxial mesoderm:
(P)
It is a thickened plate
near to the midline.
2- Lateral plate
mesoderm: (L)
It is a thin mesodermal
plate (the most lateral).
3-Intermediate
mesoderm: (I)
It connects the paraxial
and the lateral plate
mesoderm.
Yolk sac
P
L I
Amniotic cavity
P
I LThe lateral plate
mesoderm
19 days
The lateral plate
mesoderm is divided
into two layers.
Amniotic cavity
Yolk sacThe lateral plate
mesoderm
20 days
The lateral plate
mesoderm is divided
into two layers.
Amniotic cavity
Yolk sacThe lateral plate
mesoderm
20 days
Amniotic cavity
1-Somatic or parietal
mesoderm layer.
1
2
2-Splanchnic or visceral
mesoderm layer.
Yolk sacThe lateral plate
mesoderm
21 days
Amniotic cavity
A new cavity is
formed between
the two layers of
the lateral plate
mesoderm, it is
called the
intraembryonic
cavity.
Yolk sac
1 2The lateral plate mesoderm
Amniotic cavity
24 days
Splanchnic or
visceral
mesoderm layer
Somatic or
parietal
I.E.C.
mesoderm layer
I.E.C.
Yolk sac
Intraembryonic
cavity (I.E.C)Intraembryonic
cavity (I.E.C)
The lateral plate mesoderm
Amniotic cavity
28 days
1 I.E.C. 2
I.E.C.The mesoderm
Notochord
MesodermThe mesoderm
Paraxial mesoderm
Intermediate mesoderm
Lateral Plate mesodermThe mesoderm
Paraxial
mesoderm
Intermediate
mesoderm
Lateral Plate
mesoderm
Intraembryonic
cavity
Paraxial
mesoderm
Intermediate
mesoderm
Lateral Plate
mesoderm
Intraembryonic
cavityDerivatives
The parietal layer of
lateral plate mesoderm
forms:
-Dermis of the skin in the
body wall and limbs.
-Bones and connective
tissue of the limbs, and
the sternum.
The lateral plate mesodermDermis of the
skin in the body
wall and limbs
The lateral plate mesoderm
Bones and
connective tissue
of the limbs, and
the sternum.Derivatives
The visceral layer of
lateral plate mesoderm,
together with embryonic
endoderm forms:
The gut tube
The lateral plate mesodermDerivatives
The intermediate
mesoderm forms:
The urogenital
structures.
The intermediate mesodermDerivatives
The intermediate mesoderm
Urogenital structuresThe paraxial mesoderm
-By the beginning of the
third week the paraxial
mesoderm is organized
into segments known as
somites (somitomers).
-First they appear in the
cephalic region of the
embryo and proceed
cephalocaudally.The paraxial mesoderm
-By the beginning of the
third week the paraxial
mesoderm is organized
into segments known as
somites (somitomers).
-First they appear in the
cephalic region of the
embryo and proceed
cephalocaudally.The paraxial mesodermThe paraxial mesoderm
Somites
The first pair of
somites arises in the
occipital region of the
embryo at the 20th
day of development.
New somites appear
in craniocaudal
sequence at a rate of
three pairs per day.
By the end of the fifth
week, 42 to 44 pairs
are present.The paraxial mesoderm
Somites
-There are 4 occipital, 8
cervical, 12 thoracic, 5
lumbar, 5 sacral, and 8
to 10 coccygeal pairs.
-The first occipital and
the last five to seven
coccygeal somites will
disappear.The paraxial mesoderm
Amniotic cavity
Somite
Somite
Yolk sacBy the beginning of the
fourth week cells in the
somites differentiate into:
-Sclerotome
-Dermomyotome
The paraxial mesodermThe paraxial mesodermThe sclerotomes
surround the
neural tube and
notochord.
The paraxial mesoderm
They will differentiate
into the vertebrae
and ribs.The paraxial mesoderm
Vertebrae and ribsThe paraxial mesoderm
Cells in the
dermomyotome form:
Dermis for
the skin of the
back.
Muscles for the
back, body wall
and limbs.The paraxial
mesoderm
Muscles for the back, body
wall and limbs.
Dermis for the
skin of the backThe mesoderm
Blood cells and blood vessels
also arise from mesoderm.Derivatives of the mesoderm Paraxial mesoderm
Intermediate mesoderm
Lateral plate mesoderm
Somites Sclerotome Dermomyotome
Vertebrae and ribs
Dermis for the skin of the back
Muscles for the back, body wall
and limbs muscles
Blood cells and blood vessels arise from mesoderm
Urogenital structures
Parietal
Dermis of the skin in the body wall and limbs
Bones and
connective tissue of the limbs, and the sternum