Activity 1.2.2 Makeup of a Muscle

Endomysium

The delicate connective tissue surrounding the individual muscular fibers within the smallest bundles.

Epimysium

The external connective-tissue sheath of a muscle. *Wrap the combined fascicles in another piece of plastic wrap.*

Perimysium

The connective-tissue sheath that surrounds a muscle and forms sheaths for the bundles of muscle fibers. *Place the bunch of spaghetti on the end of a piece of plastic wrap.*

Fascicle

A small bundle or cluster, especially of nerve or muscle fibers. *Pick up a handful of spaghetti.*

Myofibril

A threadlike structure, extending longitudinally through a muscle fiber (cell) consisting mainly of thick filaments (myosin) and thin filaments (actin, troponin, and tropomyosin).

Given what you've already learned about what drives muscle contraction, where in your drawing do you think the actin and myosin proteins would be?

Within the muscle cells myofibrils. These proteins are too small to see at the scale of the drawing.

Using what you've already learned about muscles, what do you think it means when someone says they have "pulled" a muscle? As a physiatrist, how would you explain the physiology of a pulled muscle to a patient?

A "pulled muscle" is a muscle strain. A strain occurs when muscle fibers are under such strong mechanical stress that they are overstretched and can even tear

Muscle Rule #1):

Muscles must have at least two attachments and must cross at least one joint.

Muscle Rule #2):

Muscles always "pull" and get shorter.

Muscle Rule #3):

The attachment that moves is known as the insertion and the attachment that remains stationary is known as the origin.

Muscle Rule #4):

Muscles that decrease the angle between ventral surfaces of the body are known as flexors. Muscles that increase the angle between ventral surfaces of the body are known as extensors.

Muscle Rule #5):

Muscles work in opposing pairs.

Muscles Rule #6):

Muscle striations point to the attachments and show the direction of pull.

Triceps Origin

Proximal half of dorsal humerus.

Triceps Insertion

Distal of elbow on the ulna.

Triceps Action

Extends elbow

Trapezius and Rhomboid Minor

*Shape*:Trapezius is shaped like a trapezoid; A Rhomboid is shaped like a rhombus.

Gluteus maximus and Gluteus minimus

*Size*:Gluteus maximus is the largest muscle in the group; Gluteus minimus is the smallest.

Frontalis and Temporalis

*Location in the body*;Frontalis is located on the frontal bone of the skull; Temporalis is located on the temporal bone of the skull.

Orbicularis Oculi and Transverse abdominis

*Direction of fibers*:Fibers in orbicularis oculi form a circle; fibers in transverse abdominis "traverse" or go across the abdomen.

Flexor Carpi Ulnaris and Extensor digitorum longus

*Action*:Flexor carpi ulnaris flexes the hand at the wrist; Extensor digitorium longus extends the foot and toes upward.

Sternocleidomastoid and Brachioradialus

*Origin and insertion*:Sternocleidomastoid has origins on the breastbone (sternum) and the collar bone (clavicle or "cleido") and insertions of the mastoid process of the skull's temporal bone; Brachioradialus has an origin on the brachium or arm and an insertion on the radius.

Biceps Brachii and Triceps Brachii

*Number of origins*:Biceps brachii has two origins on the scapula; Triceps brachii has three origins on the scapula and humerus.

Caleb

Has pain in his chest muscles.

Intercostals

Muscles between the ribs.

Pectoralis Minor

Protracts and depresses scapula.

Pectoralis Major

Adducts and flexes humerus.

Grade 2 tear to the pectoralis major

Partial tear in the muscle resulting in pain, loss of strength and movement, and a longer recovery time.

What causes a grade 2 tear to the pectoralis major

This usually happens when you're weightlifting. For example, when you bench-press heavy weights on a bar and extend your arm to lift it, the weight of the bar forces down on your chest muscles. That pressure can cause a tear or, in severe cases, cause your tendon to snap.

What treatment options, if any, are available to Caleb?

Will Caleb be able to work on cars or play drums again? If so, when might that be?

Treatment options include medications, therapeutic exercises, bracing, rest, and/or surgery. With proper adherence to a physical therapy treatment plan, Caleb should be pain free and able to play drums and work on cars again within a few months. Depending on the extent of the tear, Caleb might need surgery, which would prolong his recovery time.

Describe how the structural makeup of a muscle contributes to the muscle's ability to do its job.

The fibers and connective tissue that make up the muscle both have properties, like elasticity and distensibility, that ensure that they will be able to return the same shape after moving in a certain direction.

Explain how you know which attachment of a muscle is the origin and which attachment is the insertion.

If the place is a bone that remains immobile for an action, the attachment is called an origin. If the place is on the bone that moves during the action, the attachment is called an insertion.

When an athlete or musician says that they need to "warm up" their muscles, what does that mean? Explain how warming up is beneficial.

It benefits athletes and musicians by increasing flexibility, improving blood circulation, enhancing coordination, and preparing them mentally.

Look at the temporalis, one of the face muscles you previously built. Using what you have learned about muscles and their attachments, describe the origin and the insertion of this muscle. How is this structure linked to the function?

The temporalis muscle is usually described as a single layer originating at the temporal line, converging to a tendon, and inserting onto a narrow site of the coronoid process.

Physiatrist Education:

Four years to earn a bachelor's degree, four years to complete medical school, and four years to complete a residency and earn certification.

Physiatrist Average Salary:

200K

Physiatrist Responsibilities

Physiatrists diagnose illnesses, design treatment protocols, and prescribe medications. Physiatrists design exercise programs tailored to the patient's needs and outline a plan of care that physical therapists use.