Chapter 11 - Notes PDF

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11.0 The Muscular System

Muscular System: The Muscular system is composed of the nearly 700 voluntarily controlled muscles of the body; functionally their job is to produce movements of body parts.

11.1 How Skeletal Muscles Produce Movements

Skeletal Muscle Movement: (Extra) Skeletal muscles that produce movement do so by excreting force on tendons, which in turn pull on bones or other structures; most muscles cross at least one joint and are usually attached to articulating bones that form joints. Skeletal Muscle Contractions: (Extra) When a skeletal muscle contracts it moves one of the articulating bones; the two articulating bones generally don’t move equally; one bone generally remains stationary of near its original position either because other muscles stabilize it, or its own structure makes it less moveable.

Origin: The “Origin” is the term for the bone acting as an attachment point for a muscle by its tendon, which remains stationary during movement; the origin is usually proximal. Insertion: Is the moveable bone that a muscle’s other tendon is attached to during movement; the insertion is usually distal and pulled towards the origin. Belly (Body): The “Belly” of a muscle is the fleshy portion between the tendons. Actions: The “Action” of a muscle is the main movement that occurs when a muscle contracts. Reverse Muscle Action (RMA): Some muscles switch the positions of the origin and insertions of specific muscles during reverse muscle action; meaning that during specific movements of the body, the actions are reversed.

Lever System and Leverage

Lever System and Leverage: In producing movement bones act as levers, while joints function as fulcrums for these levers; the relative distance between the fulcrum and load and the given point that the effort is applied determines whether a lever operates at a mechanical advantage or disadvantage.

Lever: Is a rigid structure that can move around a fixed point (known as a fulcrum); a lever is acted on at two different points by the two different forces: the effort and the load. Fulcrum: Is the fixed point a lever moves around. Effort: The effort is the force that causes movement on a lever. Load/Resistance: The load is the force that opposes the movement of a lever. Mechanical Advantage: Mechanical advantage occurs if the load is closer to the fulcrum, while the effort farther from the fulcrum; resulting in only a relatively small effort being required to move a large load over a small distance. Mechanical Disadvantage: Mechanical disadvantage occurs when the load is father from the fulcrum, while the effort is applied closer to the fulcrum; this results in a relatively large effort being required to move a small load (but at greater speeds).

Lever Categorization: Levers are categorized into three types according to the position of the fulcrum, the effort, and the load.

First-Class Levers: [Think EFL] First-Class levers occur when the fulcrum is between the effort and load; this produces either a mechanical advantage or disadvantage depending on where the effort or load is closer to the fulcrum. Second-Class Levers: [Think: ELF] Second-class levers occur when the load is between the fulcrum and the effort; they always produce mechanical advantages (b/c the load is always closer to the fulcrum) and the most force. Third-Class Levers: [Think: FEL] Third-class levers occur when the effort is between the fulcrum and load, favoring speed and range of motion over force; they always produce a mechanical disadvantage and are the most common lever in the body.

Coordination among Muscles

Coordination among Muscles: Most skeletal muscles are arranged in opposing pairs (antagonistic) at joints, with a prime mover/agonist and an antagonist; the antagonist and prime mover are usually located on opposite sides of a bone/joint, and can switch roles for different movements. If they contract at the same time with equal force there will be no movement.

Prime Mover or Agonist: The prime mover/agonist is a muscle within an opposing pair that contracts to cause an action. Antagonist: The antagonist is the muscle that stretches and yields to the effects of the prime mover. Synergist: Synergists are muscles that contract during the movement of a prime mover in order to stabilize intermediate joints to prevent unwanted movements, or otherwise aid the movement of the prime mover and are usually located close to the prime mover. Fixator: Are muscles in a group that stabilize the origin of the prime mover in order to allow the prime mover to act more efficiently; the act to stabilize the proximal end of a limb while movement occurs at the distal end. Compartment: Compartments are groups of skeletal muscles, their associated blood vessels, and associated nerves, all of which have a common function.

11.2 How Skeletal Muscles are named

Naming of Skeletal Muscles: Skeletal muscles are primarily named based on a combination of seven factors: (1) Direction, (2) Size, (3) Shape, (4) Action, (5) Number of Origins, (6) Location and (7) Origin and Intersection.

Direction: Orientation of the Muscle Fascicles Relative to the Bodies Midline Name Rectus Transverse Oblique

Meaning -

Parallel to the midline. Perpendicular to the midline. Diagonal to the midline.

Size: Relative Size of the Muscle Name Maximus Minimus Longus Brevis Latissimus Longissimus Magnus Major Minor Vastus

Meaning -

Largest. Smallest. Long. Short. Widest. Longest. Large. Larger. Smaller. Huge

Shape: Relative Shape of a Muscle Name Deltoid Trapezius Serratus Rhomboid Orbicularis Pectinate Piriformis Platys Quadratus Gracilis

Meaning -

Triangular. Trapezoid. Saw-Toothed. Diamond-Shaped. Circular. Comblike. Pear-shaped. Flat. Square and four-sided. Slender.

Action: Principle Action of the Muscle Name Flexor Extensor Abductor Adductor Levator Depressor Supinator Pronator Sphincter Tensor Rotator

Meaning -

Decreases joint angle. Increases joint angle. Moves bone away from midline. Moves bone closer to midline. Raises or elevates a body part. Lowers or depresses a body part. Turns palm anteriorly. Turns palm posteriorly. Decreases size of an opening. Makes body part rigid. Rotates bone around longitudinal axis.

Number of Origins: Number of Tendons of Origin Name Biceps Triceps Quadriceps

Meaning -

Two origins. Three origins. Four origins.

Location: Structure Near Which a Muscle is Found Name Example:

Meaning -

Temporalis, muscle near the temporal bone.

Origin and Insertion: Sites Where Muscle Originate and Inserts Name Example:

Meaning -

Sternocleidomastoid, originating on the sternum and clavicle and inserting on mastoid process of temporal bone.

11.A Muscles of the Head that Produce Facial Expressions

Muscles of Facial Expression: The muscles of facial expression lie within the subcutaneous layer and originate in the facia or bones of the skull, inserting into the skin; moving the skin rather than joints when the contract.

Occipitofrontalis: Occipitofrontalis is an unusual muscle group because it is made up of two parts; the anterior portion called the frontal belly, and the posterior portion called occipital belly. Frontal Belly (Occipitofrontalis): Frontal Belly is the anterior portion of the occipitofrontalis muscle located superficial to the frontal bone; it is responsible for drawing the scalp back and raising eyebrows. Occipital Belly (Occipitofrontalis): Occipital Belly is the posterior portion of the occipitofrontalis muscle located superficial to the occipital bone; it draws the scalp back posteriorly.

Orbicularis Oris: Orbicularis Oris is the muscle located around the lips of the mouth, and closes/protrudes (as in kissing) compresses (against teeth) and shapes the lips.

Zygomaticus Major: Zygomaticus Major is the muscle located at the edge of the mouth and draws the mouth superiorly and latterly (as in smiling).

Buccinator: The buccinator is the major muscular portion of the cheek; and has the duct of the parotid gland (salivary gland) pass through it; it presses cheek against teeth and lips (blowing/sucking), draws corner of mouth laterally, and assists in mastication (chewing) by keeping food between teeth.

Orbicularis Oculi: Orbicularis Oculi is the muscle that closes the eye.

Muscles of the Head that Produce Facial Expressions Muscle

Origin

Insertion

Occipitofrontalis (ok-sip-i-to-frun-TAlis) Frontal Belly (occipitofrontalis)

-

N/A

-

-

N/A

- N/A

Occipital Belly (occipitofrontalis)

-

N/A

- N/A

Orbicularis Oris (or-bi-ku-LAR-is)

-

N/A

-

N/A

Zygomaticus Major

-

N/A

-

N/A

Buccinator (BUK-si-na-tor)

-

N/A

-

N/A

-

N/A

-

N/A

Action

Location

Scalp Muscles N/A

-

Frontal/Occipital

-Scalp.

- Draws scalp anteriorly. - Raises eyebrows. - Wrinkles skin of forehead horizontally. - Draws scalp posteriorly.

- Superficial to the frontal bone of the skull.

- Closes and protrudes lips. - Compresses lips against teeth. - Shapes lips during speech. - Draws the angles of mouth superiorly and laterally (as in smiling). - Presses cheek against teeth and lips (blowing/sucking). - Draws corner of mouth laterally. - Assists in mastication (chewing) by keeping food between teeth.

- Circle around mouth.

- Closes Eye.

- Circular formation around the orbit/eye.

- Superficial to the occipital bone.

Mouth Muscles

- Lying across the Zygomatic bone of the skull. - The muscular portion of the cheek.

Orbit and Eyebrow Muscles Orbicularis Oculi

11.C Muscles that move the Mandible

Muscles of Mastication: The muscles that move the mandible at the temporomandibular joint are known as the muscles of mastication (chewing); there are four muscles with the master being the strongest and the temporalis and master being much later than the other two.

Masseter: Is the strongest of the muscles of mastication, it elevates the mandible (closes mouth); with its origin in the maxilla and zygomatic arch, and insertion in the angle and ramus of the mandible.

Temporalis: Is the muscle responsible for elevating and retracting the mandible; its origin is in the temporal bone and its insertion is into the coronoid process of the ramus of the mandible.

Muscles that move the Mandible Muscle

Origin

Insertion

Masseter* (MA-se-ter =chewer)

- Maxilla and zygomatic arch.

- Angle and Ramus of the mandible.

Temporalis* (tem-po-RA-lis)

- Temporal Bone

- Coronoid process and ramus of mandible.

Action - Elevates the mandible (such as in closing the mouth). - Elevates and retracts mandible.

Location - Side of the face along the jaw line. - Inside lateral aspect of skull.

11.F Muscles of the Neck that Move the Head

Sternocleidomastoid (SCM): Each Sternocleidomastoid muscle consists of two bellies that insert into the sternal head, and the clavicular head; muscular spasms in the two bellies have somewhat different functions, and are important landmarks that divide the neck into two major triangles: anterior and posterior. When acting together the sternocleidomastoid muscles contract to flex the cervical portion of the vertebral column and flex the head; when acting alone, each sternocleidomastoid muscle laterally flexes and rotates the head.

Muscles that move the Mandible Muscle Sternocleidomastoid* (ster-no-kli-do-MAStoyd)

Origin - Sternal Head. - Manubrium of sternum. - Clavicular head. - Medial third of clavicle.

Insertion - Mastoid process of temporal bone. - Lateral half of superior nuchal line of occipital bone.

Action

Location

Acting Together/Bilaterally - Flex cervical portion of vertebral column. - Extend head at atlantooccipital joints. Acting Singly/Unilaterally: - Laterally flex neck and head to the same side. - Rotate head to side opposite of contracting muscles. - Posterior fibers of muscle can assist in the extension of head. Reverse Muscle Action: - Elevate Sternum during force inhalations.

- Twisting from front of sternum and clavicle to the back of the occipital bone.

11.G Muscles of the Abdomen that Protect Viscera and Move the Vertebral Column

Muscle of the Abdomen that Protect Viscera: The anterolateral abdominal wall is composed of skin, fascia and four pairs of muscles: the external oblique, internal oblique, transversus abdominis and rectus abdominis. As a group the muscles of the anterolateral abdominal wall help contain and protect the abdominal viscera; flex, laterally flex, and rotate the vertebral column at the intervertebral joints, and compress the abdomen during forces exhalation, defecation, urination and childbirth.

Rectus Abdominis: Is a long muscle that extends the entire length of the anterior abdominal wall; originating at the pubic crest and pubic symphysis, and inserting on the cartilage of the 5-7 ribs and the xiphoid process of the sternum. The anterior surface of the muscle is interrupted by three transverse fibrous bands of tissue called tendinous intersections; it flexes vertebral column (especially lumbar portion), compresses abdomen to aid in: defecation, urination, forced exhalation, and childbirth, and through reverse muscle action flexes pelvis on the vertebral column.

External Oblique: The external oblique is the superficial muscle of the anterolateral abdominal wall with its fascicle extending inferiorly and medially; compresses abdomens and flexes vertebral column, RMA: flexes pelvis on the vertebrae column.

Internal Oblique: The internal oblique is the intermediate flat muscle of the anterolateral abdominal wall with its fascicle extending at right angles to those of the external oblique; when acting together (bilaterally) it compresses the abdomen and flexes vertebral column, but while acting single (unilaterally) it laterally flex vertebral column (especially lumbar) and rotates vertebral column.

Transversus Abdominis: The transversus abdominis is the deep muscle of the anterolateral abdominal wall, with most of its fascicles directed transversely around the abdominal wall; it helps to compress the abdomen.

External Oblique/Internal Oblique/Transverse Abdominis: Together the external oblique, internal oblique and transverse abdominis form three layers of muscles around the abdomen; in each layer the muscles fascicles extend in different directions, allowing for a structural arrangement that affords considerable protection to the abdominal viscera, especially when the muscles have good tone.

Muscles of the Abdomen that Protect Viscera and Move the Vertebral Column Muscle Rectus Abdominis* (REK-tus ab-DOMin-is; rectus = fascicles parallel to midline.)

Origin - Pubic crest and pubic symphysis.

- N/A

External Oblique (o-BLEK; oblique = fascicles diagonal to midline)

Internal Oblique (Internal = Farther from midline).

-

N/A

Transversus Abdominis (tranz-VER-sus = fascicles perpendicular to midline)

-

N/A

Insertion

Action

Location

- Cartilage of ribs - Flexes vertebral column 5-7 and xiphoid (especially lumbar portion) process of sternum. - Compresses abdomen to aid in: defecation, urination, forced exhalation, and childbirth. - RMA: Flexes pelvis on the vertebral column. - N/A Together (Bilaterally): -Compress abdomen. - Flex vertebral column. Singly (Unilaterally): - Laterally flex vertebrae column (especially lumbar). - Rotates vertebral column. - N/A Acting Together (Bi.Lat.): - Compresses the abdomen. - Flexes vertebral column. Acting Singly (Uni.Lat.): - Laterally flex vertebral column (especially lumbar). - Rotate vertebral column. - N /A - Compresses abdomen.

- Muscle over the “Abs”

- Muscles on the side of the abdomen, wrapping around side.

- Underneath external oblique.

- Underneath internal oblique; inner most.

11.H Muscles in the Thorax that Assist in Breathing

Muscles of the Thorax Assisting in Breathing: The muscles of the thorax (chest) alter the size of the thoracic cavity so that breathing can occur; inhalation occurs when the thoracic cavity increases in size, and exhalation occurs when the thoracic cavity decreases in size.

Diaphragm: The diaphragm is the dome-shaped muscle and the most important muscle that powers breathing; it has a convex superior surface that forms the floor of the thoracic cavity, and a inferior surface that forms the roof of the abdominal cavity. It also has three major openings through which various structures pass: (1) the aortic hiatus, (2) esophageal hiatus, and (3) caval opening, foramen for the vena cava. The diaphragm helps to return blood to heart, and increase intra-abdominal pressure during defecation/urination/childbirth.

Intercostal Muscles: Muscles involved in breathing that span the intercostal spaces between the ribs; these muscles are arranged in three layers and 11 pairs.

External Intercostal: External Intercostal muscles are a pair of 11 muscles that occupy the superficial layer and their fibers run in an oblique direction interiorly and anteriorly from the rib above to the rib below; they elevate the ribs during inhalation to help expand the thoracic cavity.

Internal Intercostal: The internal Intercostal muscles are the 11 pairs of muscles occupy the intermediate layer of the intercostal spaces, they run at right angles to the external intercostal muscles; they draw adjacent ribs together during forced exhalation to help decrease the size of the thoracic cavity.

Muscles in the Thorax that Assist in Breathing Muscle

Origin

Insertion

Diaphragm (DI-a-fram)

- N/A

- N/A

External Intercostal (in-ter-KOS-tals)

- N/A

- N/A

Internal Intercostal ()

-

N/A

-

N/A

Action

Location

- Contraction of diaphragm causes it to flatten and increase vertical dimensions of thoracic cavity, resulting in inhalation. - Relaxation of diaphragm causes it to move superiorly and decreases vertical dimension of thoracic cavity; resulting in exhalation. - Contraction elevates ribs and increases anteroposterior and lateral dimensions of thoracic cavity, resulting in inhalation. - Relaxation depresses ribs and decreases anteroposterior and lateral dimensions of thoracic cavity; resulting in exhalation. - Contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimensions of thoracic cavity during forced exhalation.

- Dome-shaped muscle located just underneath lungs.

- Muscles located between two ribs; on the anterior side.

- Muscles located underneath the external intercostal muscles of the ribs.

11.K Muscles of the Thorax That Move the Pectoral Girdle

Muscles of the Thorax and the Pectoral Girdle: The m...