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Embryology > Muscular System > Flashcards

Muscular System Flashcards

1
Q

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

A

Mesoderm

Neuroectoderm

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2
Q

Myoblasts-embryonic muscle cells are derived from ___

A

Mesenchyme

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3
Q

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

A

Mesenchyme
Myotome
Somites

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4
Q

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

A

Myogenic

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5
Q

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

A

Dermomyotome

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6
Q

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

A

Epitheliomesenchymal

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7
Q

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

A

Myogenesis

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8
Q

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

A

Myotubes

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9
Q

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

A

MyoD

MyoD, myogenin, Myf-5, MRF4)

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10
Q

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

A

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

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11
Q

Muscle growth results fromt he ongoing fusion of __ nd ___

A

Myoblasts and myotubes

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12
Q

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

A

Myofilaments

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13
Q

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

A

Myofibrils

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14
Q

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

A

Ok

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15
Q

__ produce the perimysium and epimysium layers of the fibrous sheath

A

Fibroblasts

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16
Q

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

A

External

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17
Q

Most skeletal muscles develop when

A

Before birth

And remaining by end of first year

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18
Q

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

A

Muscle increase in length and width to grow the skeleton

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19
Q

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

A

Epaxial division

Hypoxia division

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20
Q

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

A

Dorsal primary ramus

Ventral primary ramus

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21
Q

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

A

Intercostal msucles

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22
Q

Most myoblasts migrate away from the myotome and form ___ ___

A

Nonsegmented msucles

23
Q

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

A

Segmental msucles of the main body axis

Extensor msucles of the neck and vertebral column

24
Q

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

A

Degenerate

Dorsal sacrococcygeal ligaments

25
Q

Myoblasts from the hypaxial division of thecervical myotome form what

A

Scalene, prevertebral, geniohyoid, and infrahyoid

26
Q

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

A

Lateral and ventral flexor muscles of the vertebral column

27
Q

The myoblasts from the hypaxial divisions of the lumbar myotomes form

A

Quadratus lumborum muscle

28
Q

What else is derived from hypaxial division of myotomes

A

Muscles of limbs, intercostal msucles, abdominal msucles

29
Q

The sacrococcygeal myotomes form what (still hypaxial

A

Muscles of pelvic diaphragm

And probably the striated msucles of the anus and sex organs

30
Q

Myoblasts fromt he pharyngeal arches form what msucles

A

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

31
Q

What are the muscles of the pharyngeal arch innervated by

A

Pharyngeal arch nerves

32
Q

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

A

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

33
Q

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

A

Tongue

Hypoglossal XII

34
Q

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

A

Bones

35
Q

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

A

Somites

36
Q

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

A

Ventral

Epithelial

37
Q

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

A

The primordium of the limb

38
Q

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

A

Splanchnic mesenchyme

39
Q

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

A

Somatic mesoderm

40
Q

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 ___

A

Ectoderm

41
Q

What is the first sign of smooth muscle differentiation

A

Development of elongated nuclei in spindle-shaped myoblasts

42
Q

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

A

Fuse

Mononucleated

43
Q

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

A

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

44
Q

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

A

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

45
Q

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

A

Lateral splanchnic mesoderm

46
Q

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

A

Single

Fusion

47
Q

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 ___ ___

A

Disintegrate

Intercalated discs

48
Q

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

A

Myofilaments

49
Q

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

A

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

50
Q

Poland syndrome

A

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

51
Q

Absence of the pectoralis major is often associated with ____

A

Syndactaly

52
Q

Congenital torticollis

A

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

53
Q

Causes of congenital torticollis

A

Birth trauma

Malpositioning in utero

54
Q

Accessory soleus muscle

A

3% of population

Primordium of soleus may undergo early splitting to form an accessory soleus

Embryology (12 decks)

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