Muscular System

Question 1

The muscular system develops from the ___, except for the muscles of the iris which develop fromt he ____

Answer 1

Mesoderm

Neuroectoderm

Question 2

Myoblasts-embryonic muscle cells are derived from ___

Answer 2

Mesenchyme

Question 3

Skeletal muscle: The myoblasts that form the skeletal msucles of the trunk are derived from the ___ in the ___ regions of the ___

Answer 3

Mesenchyme
Myotome
Somites

Question 4

The limb muscles develop from __ precursor cells in the limb buds

Answer 4

Myogenic

Question 5

Studies show that these cells originate from the ventral ___ of somites in response to molecular signals from nearby tissue

Answer 5

Dermomyotome

Question 6

The myogenic precursor cells migrate into h limb buds, where they undergo ___ transformation

Answer 6

Epitheliomesenchymal

Question 7

The first indication of ___ is the elongation of the nuclei and cell bodies of mesenchymal cells as they differentiate into myoblasts

Answer 7

Myogenesis

Question 8

The primordial muscle cells soon fuse to form elongated , multinucleated, cylindrical structures-___

Answer 8

Myotubes

Question 9

At the molecular level, these events are preceded by gene activation and expression of the ___ family of muscle specific basic helix-loop-helix transcription factors int he precursor myogenic cells. What are they

Answer 9

MyoD

MyoD, myogenin, Myf-5, MRF4)

Question 10

What signalling molecules regulate the beginning of myogenesis and the induction of the myotome

Answer 10

Shh(from ventral neural tube)
Shh9from notochord)
Wnt, BMP4(from dorsal neural tube)
Wnt, BMP4(from overlying ectoderm)

Question 11

Muscle growth results fromt he ongoing fusion of __ nd ___

Answer 11

Myoblasts and myotubes

Question 12

____ develop in the cytoplasmof the myotubes during or after fusion of the myoblasts

Answer 12

Myofilaments

Question 13

Soon after myofilaments develop, __ and other organelles characteristic of striated muscle cells develop

Answer 13

Myofibrils

Question 14

As the myotubes differentiate, they become invested with external laminae, which segregate them from the surrounding CT

Answer 14

Ok

Question 15

__ produce the perimysium and epimysium layers of the fibrous sheath

Answer 15

Fibroblasts

Question 16

The endomysium is formed by the __ lamina which is derived from the muscle fiber and reticular fibers

Answer 16

External

Question 17

Most skeletal muscles develop when

Answer 17

Before birth

And remaining by end of first year

Question 18

The increase in the size of a muscle after the first year results from an increase int he diameter of the fibers because of the formation of more myofilaments

Answer 18

Muscle increase in length and width to grow the skeleton

Question 19

Each myotome part of a somite divides into a dorsal __ __ and a ventral __ ___

Answer 19

Epaxial division

Hypoxia division

Question 20

Each developing spinal nerve also divides and sends a branch to each division with the ____ ___ ___ supplying the epaxial division and the __ __ __ supplying the hypaxial division

Answer 20

Dorsal primary ramus

Ventral primary ramus

Question 21

Some muscles, such as the __ __, remain segmentally arranged like the somites

Answer 21

Intercostal msucles

Question 22

Most myoblasts migrate away from the myotome and form ___ ___

Answer 22

Nonsegmented msucles

Question 23

What do the myoblasts from the epaxial divisions of the myotomes form

Answer 23

Segmental msucles of the main body axis

Extensor msucles of the neck and vertebral column

Question 24

The embryonic extensor muscles that are derived from the sacral and coccygeal myotomes ___. What are their adult derivatives

Answer 24

Degenerate

Dorsal sacrococcygeal ligaments

Question 25

Myoblasts from the hypaxial division of thecervical myotome form what

Answer 25

Scalene, prevertebral, geniohyoid, and infrahyoid

Question 26

The myoblasts from the hypaxial divisions of the thoracic myotomes form what

Answer 26

Lateral and ventral flexor muscles of the vertebral column

Question 27

The myoblasts from the hypaxial divisions of the lumbar myotomes form

Answer 27

Quadratus lumborum muscle

Question 28

What else is derived from hypaxial division of myotomes

Answer 28

Muscles of limbs, intercostal msucles, abdominal msucles

Question 29

The sacrococcygeal myotomes form what (still hypaxial

Answer 29

Muscles of pelvic diaphragm | And probably the striated msucles of the anus and sex organs

Question 30

Myoblasts fromt he pharyngeal arches form what msucles

Answer 30

Muscles of mastication and facial expression as well as those of the pharynx and larynx.

Question 31

What are the muscles of the pharyngeal arch innervated by

Answer 31

Pharyngeal arch nerves

Question 32

The mesoderm oin the prechordal plate area is believed to give risk the three preotic myotomes from which myoblasts differentiate

Answer 32

Groups of myoblasts, each supplied by its own cranial nerve, form the extrinsic muscles of the eye Cn3, 4, 6

Question 33

Myoblasts from the occipital (postotic) myotomes form the ___ msucles whicha re innervated by the __ nerve

Answer 33

Tongue | Hypoglossal XII

Question 34

The musculature of the limbs develops from myoblasts surrounding the developing ___

Answer 34

Bones

Question 35

The precursor myogenic cells in the limb buds originate from the __

Answer 35

Somites

Question 36

The precursor myogenic cells are first located int he __ part of the dermomyotome and they are ___

Answer 36

Ventral | Epithelial

Question 37

After the epitheliomesenchymal transformation, the precursor myogenic cells migrate to where

Answer 37

The primordium of the limb

Question 38

Some smooth muscle fibers differentiate from __ ___ surrounding the endoderm of the primordial gut and its derivatives

Answer 38

Splanchnic mesenchyme

Question 39

The smooth muscle in the walls of many blood an lymphatic vessels arises from the ___ __

Answer 39

Somatic mesoderm

Question 40

The muscles of the iris (sphincter and dilator pupillae) and the myoepithelial cells in the mammary and sweat glands are derived form the mesenchymal cells that originate from ___

Answer 40

Ectoderm

Question 41

What is the first sign of smooth muscle differentiation

Answer 41

Development of elongated nuclei in spindle-shaped myoblasts

Question 42

During early development, new myoblasts continue to differentiate from mesenchymal cells, but do not __; they remain ___

Answer 42

Fuse | Mononucleated

Question 43

During later development, the division of existing myoblasts gradually replaces the differentiation of new myoblasts in the production of new smooth muscle tissue

Answer 43

Filamentous, but nonsacromeric, contractile elements develop in their cytoplasm and the external surface of each differential cell acquires a surrounding external lamina

Question 44

As smooth muscle fibers develop into sheets or bundles, they receive autonomic innervation

Answer 44

Fibroblasts and muscle cells synthesize and lay down collagenous , elastic, and reticular fibers

Question 45

The __ ___ ___ gives rise to the mesenchyme surrounding the developing heart tube

Answer 45

Lateral splanchnic mesoderm

Question 46

Cardiac myoblasts are derived fromt he mesenchyme surrounding the developing heart tube by differentiation and growth of ___ cells, unlike striated skeletal muscle fibers, which develop by __ of cells

Answer 46

Single | Fusion

Question 47

In development of cardiac muscles, the myoblasts adhere to each other as in developing skeletal muscle , but the intervening cell membranes do not ____. These areas of adhesions give rise to ___ ___

Answer 47

Disintegrate | Intercalated discs

Question 48

Growth of cardiac muscle fibers results fromt he formation of new _____

Answer 48

Myofilaments

Question 49

Late in the embryonic period, special bundles of muscle cells develop that have relatively few myofibrils and relatively larger diameters than typical cardiac muscle fibers

Answer 49

The cells develop from original trabeculated myocardium and have fast conducting gap junctions and form the conducting system of the heart (purkinje fibers)

Question 50

Poland syndrome

Answer 50

Breast and nipple aplasia or hypoplasia, deficiencies of axillary hair and subcutaneous fat and shortened arms and fingers

Question 51

Absence of the pectoralis major is often associated with ____

Answer 51

Syndactaly

Question 52

Congenital torticollis

Answer 52

Sternocleidomastoid muscle injured at birth Fixed rotation Nd tilting of the head because of concomitant muscle fibrosis, as well as shortening of the sternocleidomastoid muscle on one side

Question 53

Causes of congenital torticollis

Answer 53

Birth trauma | Malpositioning in utero

Question 54

Accessory soleus muscle

Answer 54

3% of population | Primordium of soleus may undergo early splitting to form an accessory soleus