muscular system

Muscles of vertebrates

• specialized for contraction and thus can pull the parts to which they are attached.

• They are responsible for locomotion and for movements of various internal organs

3 types of vertebrate muscular system

1. Skeletal or striated voluntary muscles

2. Smooth or nonstriated involuntary muscles

3. Cardiac or striated involuntary muscle

Skeletal muscle

• forms the greater part of the body and is under the control of the will and only muscle that can be consciously controlled.

• Attached to the bones; contractions resulted to movement.

• consist of long fibers which are in reality multinucleated cells.

• Each fiber is bounded by a membrane, the sarcolemma.

• Numerous myofibrils, which are present within the fiber, are surrounded by sarcoplasm.

Smooth muscle

• This muscles makes up the muscle of visceral organs, ducts and blood vessels

• occurs in sheets as part of an organ such as the intestine.

• The cells are spindle-shaped, contains a single nuclei (uninucleated), have myofibrils but lack striations.

• The cytoplasm, called sarcoplasm, is bounded by the cell membrane, the sarcolemma.

Cardiac muscle

• This muscles which makes up the muscles of the heart, and which is not under the control of the will.

• Stimulates its own contraction that for our heartbeat, rhythmically and involuntary, closely resembles skeletal muscle in structure since it’s striated

• They appear to represent the cell membranes of adjacent cardiac muscle cells.

• Each cell therefore contains its own nucleus and is a distinct entity.

• Signal from the nervous system control rate of contraction.

• Intercalated disc

Intercalated discs

• present at intervals in cardiac muscle fibers.

• Specialized junctions connecting cardiac muscle cells (cardiomyocytes), facilitating both mechanical coupling and efficient electrical communication.

Orgin

Less movable part of the muscle

Insertion

More movable part

Belly

pronounced bulge in the middle are said to have a ______.

Tendons

some muscles are attached by means of strong white fibrous cords of connective tissue

Aponeurosis

broad, flat, ribbon-shaped tendons

Flexor

Bend, close or decrease joint angle

Extensor

Straighten or increase joint angle

Abductor

Draw part away from the median line

Adductor

Draw part toward the median line

Circumduction

Movement of the body in a circular manner

Rotator

Revolve a part on its axis

Elevator or levator

Raise or lift a part

Depressor

Lower or depress a part

Constrictor

Draw parts together (tighten, smaller, or narrower)

Dilator

Opens a part

Pronator

make is prone (turn it downward)

Supinator

Rotators that turn the palm upward

Size

1. Maximus (largest)

2. Medius (medium)

3. Minimus (smallest)

4. Major and minor

5. Brevis (short)

6. Longus (long)

7. Vastus (huge)

Nomenclature

• Direction of fibers

• Location or position

• Number of subdivisions

• shape

• Orgin or insertion

• Action

• Size

Oblique

Fibers run diagonally(direction)

Rectus

fibers run straight, usually parallel to the body’s midline (direction)

Thoracic

Found in chest area (location)

Superficial

Found close to the surface (location)

Deep

Located beneath other muscles (location)

Triceps

has three heads or points of origin (number of subdivisions)

Deltoid

Triangular shaped (delta, greek)

Trapezius

trapezoid-shaped (like a kite or diamond, covering the upper back and neck).

Sternocleidomastoid

attaches to the sternum, clavicle, and mastoid process (behind the ear). (Origin or insertion)

Biceps brachii

originates from the scapula and inserts into the radius (Origin or insertion)

Triceps brachii

originates from scapula and humerus, and inserts into ulna (olecranon process). (Origin or insertion)

Xiphihumeralis

connects the xiphoid process (part of the sternum) to the humerus. (Origin or insertion)

Levator scapulae

helps lift (elevate) the scapula (shoulder blade).(action)

Major

Larger muscle (size)

Longissimus

Very long muscle (size)

Somatic muscles

• Controls voluntary movement

• These muscles help with movement and posture

  • Axial

  • Appendicular

Axial muscle

• are the skeletal muscles of the trunk and tail including muscles beneath the pharynx, tongue muscles and eyeballs muscles.

• Metsmerism (segmentation) most evident feature, meaning they appear in repeated sections along the body.

• They are divided into dorsals, epaxial muscles, and ventral, hypaxial muscles.

Epaxial muscle

(dorsal - posture/movement) muscles extend to the skull as epibranchial muscles

Hypaxial muscle

(ventral - breathing/movement) extend forward under the pharynx as muscles (supporting jaw and throat movement) and tongue muscles (helping with speech and swallowing).

Appendicular muscles

are the muscles that insert on the girdles fins, or limbs, thereby moving the appendage.

Extrinsic Appendicular Muscles (Axial Skeleton Origin)

• These muscles start from the axial skeleton (skull, spine, or ribs) and attach to the girdles or limbs. They help move the limbs by pulling from the body’s core.

• Example: Trapezius, Latissimus dorsi, serratus ventralis

Intrinsic Appendicular Muscles (Appendicular Origin or Origin on the Girdles)

• These muscles start from the girdles or limbs themselves, meaning they do not rely on the axial skeleton for movement.

• They control more refined limb movements.

• Example: Deltoid, triceps brachii, biceps brachii, subscapularis

Visceral muscles

• Control involuntary functions.

• Involved in organ function and circulation.

  • Branchiomeric

  • Smooth

  • Cardiac

Branchiomeric muscles

• associated with the visceral arches.

• They operate the jaws of vertebrates.

• Found in the head and neck, controlling jaw and facial movements.

• Example: Masseter (used for chewing)

40%

Muscles make up approximately ____ of total weight

Heart

hardest-working muscle in the body. It pumps 5 quarts of blood per minute and 2,000 gallons daily.

Gluteus maximus

body's largest muscle. It is in the buttocks and helps humans maintain an upright posture.

Ear

contains the smallest muscles in the body alongside the smallest bones. These muscle hold the inner ear together and are connected to the eardrum.

Masseter

Located in the jaw is the strongest by weight. It allows the teeth to close with a force up to 55 pounds on the incisors or 200 pounds on the molars.

600 to 700

The muscular system contains more than _______ muscles that work together to enable the full functioning of the body

Eye muscles

• Main muscles:

  • Superior rectus: moves eye up

  • Inferior rectus: moves eye down

  • Medial rectus: moves eye inward

  • Inferior oblique: rotates eye upward and outward

• Other muscles:

  • Levator palpebrae superioris: lifts upper eyelid

  • Retractor bulbi (frogs): pulls eyeball inward