Development Of The Musculoskeletal System

Question 1

Intraembryonic Mesoderm Differentiates into 3 parts?

Answer 1

1. Paraxial mesoderm
2. Intermediate mesoderm
3. Lateral mesoderm

Question 2

Paraxial mesoderm divides into ?

Answer 2

segments called ‘somites’.

Question 3

Each somite divides into 3 parts:

?

Answer 3

Dermatome
Myotome

Sclerotome

Question 4

Development of the Skeletal System

Source of Origin:

Answer 4

Paraxial Mesoderm • Lateral plate Mesoderm • Neural Crest Cells

Question 5

The vertebral column develops from the

?

Answer 5

sclerotomes (ventromedial parts ) of the

somites

Question 6

The somites develop from ?

Answer 6

para-axial

mesoderm.

Question 7

Origins of the Axial & Appendicular Skeleton

The mesenchyme in the paraxial
mesoderm will transform into
?

Answer 7

Osteoblasts that will form the
bony elements of the vertebral
column (e.g. body, transverse
process, spinous process etc).

Question 8

The mesenchyme in the
somatopleuric mesoderm will
transform into ?

Answer 8

osteoblasts that
will form the Pelvic & Pectoral
girdles and also the bones of
upper & lower limbs.

Question 9

Development of Skull (Intramembranous Ossification)

The skull is divided into two parts ?

Answer 9

Neurocranium

Viscerocranium

Question 10

which forms a
protective covering around
the brain is derived from the ‘
occipital somites’
Is the?

Answer 10

Neurocranium

Question 11

which forms
the skeleton of the face is
derived from the ‘Neural
crest cells’.
 Is the?

Answer 11

Viscerocranium

Question 12

Neurocranium has 2 types?

Answer 12

Membranous Neurocranium  is
composed of flat bones of the
cranial vault.
– Cartilagenous Neurocranium  is
composed of the irregular
bones of the base of skull

Question 13

The limb buds become visible as outpocketings from the?

Answer 13

ventrolateral

body wall of the embryo in the beginning of 5 th wk.

Question 14

terminal portion of the limb buds becomes ?

Answer 14

flattened to
form hand plates & foot plates and are separated from the proximal
segment by a circular constriction (the future wrist crease & ankle
crease)

Question 15

Initially, limb buds consists of ?

Answer 15

mesenchymal core.

Question 16

The mesenchyme in the buds begins to condense, and by the end of 6 th wk the first hyaline cartilage models, foreshadowing the?

Answer 16

bones of extremities can be recognized.

Question 17

During the 7 th week, the upper &

lower limbs?

Answer 17

rotate in opposite

directions.

Question 18

The upper limb rotates 90⁰?

Answer 18

laterally/ extensor muscles lie on
the posterior surface of the upper
limb and the thumbs also come to lie
laterally.

Question 19

The lower limb rotates 90⁰?

Answer 19

medially/
so that the extensor muscles come to
lie on the anterior surface of the
lower limb and the big toe lies on the
medial side.

Question 20

Patient has Both extremities are short but head is of
normal size. Caused by a disturbance in the
‘endochondral/intracartilagenous’
ossification in the ‘epiphyseal/growth
plates’ of the long bones.

The result is Dwarfism?

Answer 20

Achondroplasia

Question 21

Achondroplasia explain ?

Answer 21

Caused by a disturbance in the
‘endochondral/intracartilagenous’
ossification in the ‘epiphyseal/growth
plates’ of the long bones.
• The result is Dwarfism.
• Both extremities are short but head is of
normal size.

Question 22

The entire muscular system of the body develops from the ?

Answer 22

Mesoderm (except for the muscles of Iris, which are derived from the ectoderm of the optic cups).

Question 23

The cardiac muscles of the heart develops from the ?

Answer 23

The cardiac muscles of the heart develops from the splanchnic mesoderm surrounding the primitive heart tube.

Question 24

The smooth muscles of gastrointestinal tract develop from the ?

Answer 24

Splanchnic mesoderm surrounding the gut tube .

Question 25

The Somites develop
from Paraxial mesoderm
and give rise to the
?

Answer 25

skeletal musculature of
axial skeleton, body wall,
limbs, and head.

Question 26

somites form and
differentiate into the
‘sclerotome and
dermomyotome.
From?

Answer 26

From the occipital region

down

Question 27

At the end of 5 th wk, the

musculature in the body wall divides into?

Answer 27

a small dorsal portion, the ‘
Epimere’

a larger ventral portion, the ‘
Hypomere’.

Question 28

The nerve innervating the
segmental muscles is also
divided into two rami;
?

Answer 28

Dorsal primary ramus’ supplying the Epimere

‘Ventral primary ramus’ supplying the Hypomere

Question 29

Formation of Extensors and Flexors

?

Answer 29

The muscles of Epimere form the extensors of the vertebral column.
The muscles of Hypomere form the ventral and lateral flexors of vertebral column.

Question 30

The Hypomere splits into three layers;

Answer 30

In the thorax, these layers are represented by External & Internal intercostals and Transversus thoracic muscles.

In the Abdomen, these are represented by External & Internal Obliques and Transversus abdominis muscles.