Muscles

Question 1

What are the different ways muscles can be classified?

Answer 1

• location: somatic/skeletal and visceral/gut
• method of nervous system control: voluntary vs not
• microscopic appearance: skeletal, smooth, etc

Question 2

Briefly describe defining features of smooth muscle

Answer 2

• not striated/striped
• spindle shaped
• not branched
• central nucleus, no disks
• relatively involuntary

Question 3

Briefly describe defining features of skeletal muscle

Answer 3

• striated/striped
• cylindrical
• not branched
• peripheral nuclei, no disks
• voluntary

Question 4

Briefly describe defining features of cardiac muscle

Answer 4

• striated/striped
• cylindrical
• branched
• central nuclei, intercalated disks
• relatively involuntary

Question 5

What muscles are from the mesoderm?

Answer 5

• somites/epimere: dermatome, myotome, sclerotome
• hypomere
• mesenchyme

Question 6

What muscles can epimere branch into?

Answer 6

• somitomeres, cranial muscles

- myotomes, post-cranial muscles

Question 7

What are the two subgroups of muscles in postcranial muscles?

Answer 7

1. Trunk/axial muscles from myotome of epimere

2. Appendicular muscles

Question 8

What are the three types of muscles under cranial muscles?

Answer 8

1. Branchiomeric muscles from somitomeres of epimere
2. Hypobranchial muscles from somites
3. Extrinsic eye muscles

Question 9

Briefly describe the different structures of the trunk muscles in fishes and the major function

Answer 9

• myotomes form myomeres/segments separated by myosepta
• epaxial portions dorsal, hypaxial portions ventral
• propulsive locomotion

Question 10

How do trunk muscles vary in tetrapods compared to fish?

Answer 10

• less involved in locomotion

- allows for flexion of vertebral column, moving ribs, supporting weight, and head movement

Question 11

How do trunk muscles vary in amphibians compared to fish?

Answer 11

• epaxial muscles now one segmented muscle mass

- hypaxial muscles differentiated into 3 bands of muscle

Question 12

How do trunk muscles in amniotes vary compared to fish?

Answer 12

• further differentiation of epaxial and hypaxial
• reduced muscles and small specialized muscles for complex head and trunk movement
• more muscle for more diverse functions

Question 13

Briefly describe the appendicular muscles present in fishes

Answer 13

• muscles for opposite things
• posterodorsal to fin: abductor/extensor pulls fin dorsally/caudally
• anteroventral to fin: adductor/flexor pulls fin ventrall/cranially

Question 14

How do appendicular muscles of tetrapods vary compared to fishes?

Answer 14

• larger muscle mass supports body weight
• pectoral girdle and forelimb muscles derive from fish musculature
• pelvic girdle and hindlimb muscles derive from muscles of fish ancestor
• variation between birds and mammals on what muscles are enlarged and which are reduced

Question 15

Briefly describe the branchial muscles present in fishes

Answer 15

• simple muscles associated with gills
• muscles on arches I and II for jaw suspension and closing
• feeding and respiration, contraction reduces mouth volume

Question 16

Briefly describe the branchial muscles present in tetrapods

Answer 16

• jaw and throat muscles, as well as for stapes and shoulder control
• mandibular adductor in jaw is dominant
• some muscles of hyoid arch become facial muscles

Question 17

How do hypobranchial muscles differ between fishes and tetrapods?

Answer 17

Fish: for reeding and respiration, contraction opens mouth
Tetrapods: more differentiated, for catching, manipulating, swallowing food, moving tongue, throat, larynx

Question 18

T or F: the 6 extrinsic muscles present in fish are more differentiated in tetrapods

Answer 18

False

The extrinsic eye muscles were least affected by the transition from water to land and are retained in tetrapods