Zoo-Lab (Sem-1) - Exercise 21: The Muscular System

muscular system

concerned with the various types of movements in the animals; groups vary in origin histology, distribution, and function

fibers/myofibers

muscle cells

skeletal; cardiac; smooth

types of vertebrate muscles

skeletal muscle

striated and voluntary; forms the bulk of the body wall

smooth muscle

involuntary; found in the walls of the digestive tracts and other visceral organs; controlled by the sympathetic nervous system

cardiac muscle

found in the heart; striated and involuntary

origin

the point of attachment of a muscle on the bone that will not move when the muscle contracts

insertion

the point of attachment of a muscle on the bone that will move when the muscle contracts

belly

middle part of the muscle; between the two points of attachment

heads

proximal and distal ends of a muscle

action

function of the muscle; accomplished by the contraction of the component muscle fibers

synergists

muscles which concur in action

antagonists

muscles which oppose in action

flexors

muscles that bend one part upon another

extensors

muscles that straighten a part

depressors

muscles that lower a part

levators

muscles that raise a part

rotator

muscles that rotate a part upon another

constrictor/sphincter

muscles that close an opening

dilator

muscles that antagonize the constrictor

adductor

muscle that draws a limb toward the ventral surface

abductor

muscle that draw a limb away from the ventral surface

fasciae

sheets or bands of connective tissue that cover groups of muscles of the body

fascia

sing. fasciae

tendon

a whole fibrous cord or band of dense regular connective tissues

aponeurosis

broad, flat, and ribbon-like loose connective tissue

body wall

made up of the skin or the integument forming the outer covering of the body; separated from the bulk of the body via the subcutaneous lymph spaces

subcutaneous lymph spaces

separated the body wall from the bulk of the body

depressor mandibuli; temporalis; masseter

3 muscles of the head (dorsal aspect)

depressor mandibuli

a broad muscle behind the tympanic ring

origin - depressor mandibuli

behind the tympanic ring

insertion - depressor mandibuli

caudal portion of the lower jaw

action - depressor mandibuli

closes the mouth

temporalis

a small muscle that extends from the tip of the suprascapula to the region between the tympanic ring and the eye

origin - temporalis

dorsal border of the suprascapula

insertion - temporalis

dorsal lower jaw

action - temporalis

opens the mouth

masseter

a small muscle located in front of the tympanic ring

origin - masseter

tympanic ring and adjacent bones

insertion - masseter

outer surface of the lower jaw

action - masseter

raises the lower jaw and closes the mouth

submental; mylohyoid/submaxillaris; median raphe; sternohyoid

4 muscles of the head (ventral aspect)

submental

a transversely oriented muscle connecting the distal mandibular tips, contributing to the formation of the floor of the buccal cavity

mylohyoid/submaxillaris

a very thin sheet of muscle at the ventral surface of the head region, the floor of the mouth

origin - mylohyoid/submaxillaris

ventral lower jaw

insertion - mylohyoid/submaxillaris

median raphe

action - mylohyoid/submaxillaris

pulls the floor of the mouth downward in breathing

sternohyoid

the continuation of the rectus abdominis forward to the head under episternum

origin - sternohyoid

coracoid and clavicle

insertion - sternohyoid

hyoid bone

action - sternohyoid

pulls the hyoid backward, thus lowering the floor of the mouth in respiration

latissimus dorsi; dorsalis scapulae (infraspinatus); longissimus dorsi; coccygeo-sacralis; coccygeo-iliacus

5 muscles of the back and girdles

latissimus dorsi

small muscle overlapping the caudal portion of the suprascapula

origin - latissimus dorsi

fascia of the back just behind the shoulder blade

insertion - latissimus dorsi

deltoid ridge of the humerus

action - latissimus dorsi

abducts the arm and pulls the arm upward and backward

dorsalis scapulae (infraspinatus)

muscles covering the outer surface of the suprascapula

origin - dorsalis scapulae (infraspinatus)

scapula

insertion - dorsalis scapulae (infraspinatus)

tendon joining the latissimus dorsi

action - dorsalis scapulae (infraspinatus)

raises the arms towards the body

longissimus dorsi

long muscle running close and along the vertebral column

origin - longissimus dorsi

anterior third of the urostyle

insertion - longissimus dorsi

vertebrae and skull

action - longissimus dorsi

raises the head and straightens the back

coccygeo-sacralis

a narrow muscle located posteriorly to the longissimus dorsi and extends posterior in oblique postion

origin - coccygeo-sacralis

sacralis urostyle

insertion - coccygeo-sacralis

transverse process of the sacral vertebra

action - coccygeo-sacralis

humps the back when the two muscles of the sides of the body act together, when they act singly, turns the back to one side

coccygeo-iliacus

running diagonally in the space between the ilia and the urostyle just caudal of the preceding muscle

origin - coccygeo-iliacus

iliacus urostyle

insertion - coccygeo-iliacus

anterior part of the ilium

action - coccygeo-iliacus

holds urostyle in place

rectus abdominis; external oblique; internal oblique/transverse abdominis

3 muscles of the abdomen

rectus abdominis

broad, thin muscle covering the ventral side of the abdomen; two parts separated by the linea alba, marked by crosswise faint lines called the ventral inscriptiones tendinae

linea alba

mid-ventral line; separates the two recti abdominis; appears red because of the presence of the blood vessel, the ventral abdominal vein

ventral abdominal vein

blood vessel which causes the linea alba to appear red

ventral inscriptiones tendineae

crosswise faint lines which mark the recti abdominis muscles

origin - rectus abdominis

pubic border

insertion - rectus abdominis

sternum and coracoid

action - rectus abdominis

support the abdominal viscera

external oblique

a thin sheet of muscle, which forms the outer layer of the body wall at the side of the abdomen; muscle fibers are directed obliquely caudal and ventral

origin - external oblique

dorsal fascia

insertion - external oblique

linea alba, dorsal to rectus and abdominis

action - external oblique

supports and compresses the abdomen

internal oblique/transverse abdominis

another sheet of oblique muscles internal to the preceding; muscle fibers here are directed obliquely in the opposite direction to the fibers for the external oblique; an incision in the external oblique is need to view this muscle

origin - internal oblique/transverse abdominis

transverse processes of 4th to 9th vertebrae, and ilium

insertion - internal oblique/transverse abdominis

coracoids, xiphisternum, and linea alba

action - internal oblique/transverse abdominis

supports and compresses the abdomen

deltoid; sternoradialis; anterior pectoralis; middle pectoralis; posterior pectoralis

5 muscles of the shoulder and chest

deltoid

a triangularly-shaped muscle that lies at the anterior border of the shoulder

origin - deltoid

clavicle and scapula

insertion - deltoid

deltoid crest of the humerus

action - deltoid

raises and rotates the humerus

sternoradialis

next to the preceding (deltoid) and arises in the midventral line passing outwards, piercing the distal portion of the deltoid

origin - sternoradialis

episternum

insertion - sternoradialis

radius

action - sternoradialis

raises the humerus

anterior pectoralis

anterior muscle of the chest just next to the sternoradialis

origin - anterior pectoralis

anterior sternum and coracoid

insertion - anterior pectoralis

anterior deltoid ridge