Muscular System

Muscular System

Muscular System of Invertebrates Evolution of the Vertebrate Muscular System

Suggested reading: Miller SA and Harley JP. 2007. Zoology. 7 th ed. McGraw-Hill Education. p 395-403

Muscular System of Invertebrates and Vertebrates

I. Nonmuscular movement

II.

Muscular movement

Nonmuscular Movement

1. Amoeboid movement • Of amoebas, other protists, white blood cells, embryonic mesenchyme and other mobile cells of higher animals Mechanism of movement – Gel ectoplasm (plasmagel) in the recruitment zone changes into fluid endoplasm (plasmasol) as it flows into the fountain zone of a pseudopodium. – Plasmasol then changes back to plasmagel once it reaches the tip of the pseudopodium.

Nonmuscular Movement

2. Flagellar movement • Of unicellular protists eg. Euglena, sperm cells and choanocytes of sponges • Wave-like undulation propels fluid parallel to the long axis of the flagellum

Nonmuscular Movement

3. Ciliary movement • Of Paramecium, large flatworms and proboscis worms (nermertines) • Coordinated beating of hairlike extensions or cilia organized in rows produce ciliary waves that facilitate locomotion (i.e. ciliary creeping) or propel fluids and particles across surfaces of tissues

Nonmuscular Movement

3. Ciliary movement • The complementary function of ciliary and muscular movements in flatworms and nemertines indicates that the transition from ciliary to muscular movement may have taken place among the flatworm-like ancestors.

Muscular Tissues of Invertebrates

• Skeletal muscles of invertebrates differ from those of vertebrates • • Invertebrates – housed in exoskeleton Vertebrates – covers endoskeleton

Muscular Tissues of Invertebrates

• Striated muscles with single nuclei similar to cardiac muscles are also common in invertebrates but with many modifications. Smooth muscles are also predominant in invertebrates. In some invertebrates, there is even a combination of the different muscle types - eg. bivalve...