Anatomy and Physiology II

Anatomy and Physiology II

Syllabus from Dr. Wong:

Syllabus from Dr. Beaumont:

Sciatica – Peripheral Nervous System – PNS – Clinical Applications

Dr. Phillip T  Wong  & Dr. Mark Beaumont  

OER – Open Educational Resources

Anatomy

Origin: Nerve roots from L4, L5, S1, S2, and S3 on each side (left and right).  

Branches: The main sciatic nerve on each side splits into a tibial nerve and fibular nerve above or at the location of the popliteal fossa (knee). The fibular nerve is also known as the common peroneal nerve. 

The nerve roots of the lower lumbar spine and sacral spine from L4 to S3 merge and join together on each side approximately at the greater sciatic foramen. The thickness can range from the size of an individual thumb to ¾ of an inch.

Majority of the general population (about 80%) have their entire sciatic nerve anatomically anterior to the piriformis muscle. About 20% of the population have different variations in which the most common is the sciatic nerve splitting into two (divides) above the piriformis muscle. Therefore, one portion of the sciatic nerve pierces directly through the piriformis muscle and the other portion is located anterior to the piriformis muscle. 

Physiology

The function of the sciatic nerve is to provide motor, reflexes, and sensory innervation to the lower extremity. Specifically, it allows for:

1. Muscle contraction of the lower limb specifically the posterior side such as the hamstrings and calf muscles.
2. Sensation of stimuli at the skin of lower extremity.
3. Reflexes (Patella Tendon Reflex and Achilles Tendon Reflex).
   

Sciatica

Causes: Herniated disc (bulging and protruding), bone spurs (osteoarthritis –degenerative joint disease), spinal stenosis, piriformis syndrome, and sacro-iliac joint dysfunction. Other rare causes can vary from tumors and diabetes mellitus. Occupations that required prolonged periods of sitting along with older age and obesity can contribute to sciatica. Also, simply wearing a wallet on the back pocket of pants or jeans with prolong sitting.

Symptoms: Motor weakness of specific muscle groups of the lower extremity causing imbalance and strength integrity is compromised with patient. In addition, numbness and tingling can occur from the lower back, pelvic region (buttocks), thigh (anterior and/or posterior side), popliteal fossa (behind knee), gastrocnemius/soleus muscles (calf), and entire foot. Hyper-reflex or Hypo-reflex can occur with sciatica. In extreme situations, sciatica can cause bowel, bladder, and/or sexual dysfunction.

Diagnosis: Physical Examination which elicits muscle weakness and pain (tenderness at gluteus maximus and piriformis) at the lower extremity along with subluxation (joint dysfunction) of the SI (Sacro-Illiac) joint. In addition, dysfunction of the sensory dermatomes and results of the reflex assessment (hypo or hyper reflex). X-rays to reveal bone spurs. MRI to confirm and analyze bulging vs protruding herniated disk. EMG (Electromyelography) to measure impulses and to assess nerve conduction speeds of sciatic nerve.

Treatment: RICE protocols upon initial injury with muscle spasms and inflammation. Prescribed muscle relaxants to reduce inflammation and muscle spasms. Cortico-steriod injections to reduce inflammation around the irritated nerve. Conservative chiropractic, physical therapy, massage, and acupuncture treatments. In addition, therapeutic exercises to stretch and strengthen gluteus maximus and piriformis muscle. If necessary, surgery to remove bone spurs (laminectomy) and discectomy to reduce physical and/or chemical irritation of nerve root contributing to sciatica.

References

https://www.mayoclinic.org/diseases-conditions/sciatica/symptoms-causes/syc-20377435 

https://www.mayoclinic.org/diseases-conditions/sciatica/diagnosis-treatment/drc-20377441 

https://www.spine-health.com/conditions/sciatica/what-you-need-know-about-sciatica 

https://smart.servier.com/smart_image/sciatic-nerve/ 

https://www.spine-health.com/conditions/spine-anatomy/sciatic-nerve-anatomy 

Rotator Cuff Injuries – Clinical Applications

Dr. Phillip T Wong & Dr. Mark Beaumont 

OER – Open Educational Resources

The rotator cuff stabilizes the should joint. It is made up of four muscles which include the supraspinatus, infraspinatus, teres minor, and subscapularis. The supraspinatus muscle and tendon is the most commonly affected when the rotator cuff is injured.  

A rotator cuff tear is an injury of one or more of the tendons or muscles of the rotator cuff of the shoulder. Symptoms may include shoulder pain, which is often worse with movement, or weakness. This may limit peoples’ ability to brush their hair or put on clothing. Clicking may also occur with movement of the arm. Tears may occur as the result of a sudden force or gradually over time. Risk factors include certain repetitive activities, smoking, and a family history of the condition. Diagnosis is based on symptoms, examination, and medical imaging.  

The most common presentation is shoulder pain or discomfort. This may occur with activity, particularly shoulder activity above the horizontal position, but may also be present at rest in bed. Pain-restricted movement above the horizontal position may be present, as well as weakness with shoulder flexion and abduction.

Risk factors

Epidemiological studies strongly support a relationship between age and cuff tear prevalence. Those most prone to failed rotator cuff syndrome are people 65 years of age or older; and those with large, sustained tears. Smokers, people with diabetes, individuals with muscle atrophy and those who do not follow postoperative-care recommendations also are at greater risk. This high rate of tear prevalence in asymptomatic individuals suggests that rotator cuff tears could be considered a "normal" process of aging rather than a result of an apparent pathological process. Increased body mass index is also associated with tearing. Recurrent lifting and overhead motions are at risk for rotator cuff injury as well. This includes jobs that involve repetitive overhead work, such as carpenters, painters, custodians, and servers. People who play sports that involve overhead motions, such as swimming, volleyball, baseball, tennis and football quarterbacks are at a greater risk of experiencing a rotator cuff tear. Generally, the incidence of rotator cuff tears or injuries increases by age while corticosteroid injection for pain relief increases the risk of tendon tear and delays tendon healing. 

Symptoms

Symptoms may occur immediately after trauma or develop over time. 

Acute injury is less frequent than chronic disease, but may follow bouts of forcefully raising the arm against resistance, as occurs in weightlifting, for example. In addition, falling forcefully on the shoulder can cause acute symptoms. These traumatic tears predominantly affect the supraspinatus tendon or the rotator interval and symptoms include severe pain that radiates through the arm, and limited range of motion, specifically during abduction of the shoulder. Chronic tears occur among individuals who constantly participate in overhead activities, such as pitching or swimming, but can also develop from shoulder tendinitis or rotator cuff disease. Symptoms arising from chronic tears include sporadic worsening of pain, debilitation, and atrophy of the muscles, noticeable pain during rest, crackling sensations (crepitus) when moving the shoulder, and inability to move or lift the arm sufficiently, especially during abduction and flexion motions. 

Diagnosis

Magnetic resonance imaging (MRI) and ultrasound are comparable in efficacy and helpful in the diagnosis of rotator cuff injuries. MRI can reliably detect most full-thickness tears although very small pinpoint tears may be missed. It should be realized that a normal MRI cannot fully rule out a small tear (a false negative) while partial-thickness tears are not as reliably detected. While MRI is sensitive in identifying tendon degeneration (tendinopathy), it may not reliably distinguish between a degenerative tendon and a partially torn tendon. 

Treatment

Treatment may include pain medication such as NSAIDs and specific exercises. It is recommended that people who are unable to raise their arm above 90 degrees after 2 weeks should be further assessed. In severe cases surgery may be indicated. Rotator cuff tears are common. Those over the age of 40 are most often affected. After rotator cuff surgery, conservative treatments such as chiropractic, physical therapy, acupuncture, and massage therapy to stretch and strength and to increase AROM of gleno-humeral joint with less pain upon end range.

Rotator Cuff Muscles Review Box

Plumb Line – Clinical Applications

Dr. Phillip T. Wong  & Dr. Mark Beaumont 

OER – Open Educational Resources

In order to do a spinal examination and proper posture analysis for a patient during a physical examination, a chiropractic physician may use a plumb line test.

With the lateral view of a patient in anatomical position, the Plumb Line is a vertical line (frontal/coronal line) that intersects the following landmarks of the human body:

1. Slightly anterior to the External Acoustic Meatus (EAM) / Mastoid Process.
2. AC joint (Acromio - Clavicular).
3. Third Lumbar Vertebrae.
   
4. Greater Trochanter of the Femur.
   
5. Anterior third of knee.
6. Immediately anterior to Lateral Malleolus.
   

A patient that has good to excellent posture would have the Plumb’s line intersect at all bony landmarks listed above. 

If the line intersects slightly anterior or posterior to any specific bony landmark listed above, the patient can have a structural integrity issue or poor biomechanics particularly with the skeletal and muscular system.  

Forward Head Carriage: EAM and Mastoid Process anterior to Plumb’s Line. 

Rounded Shoulders and Kyphosis: AC joint posterior to Plumb’s Line.  

Hyper-Lordosis: Third lumbar vertebrae anterior to Plumb’s Line.  

References

www.clker.com 

www.pinterest.com 

www.slideplayer.com 

www.acefitness.org (American Council on Exercise) 

https://newsinhealth.nih.gov/2017/08/getting-it-straight 

Muscle Fibers – Clinical Applications

Dr. Phillip T. Wong & Dr. Mark Beaumont 

OER – Open Educational Resources

Muscle fiber types

Two criteria to consider when classifying the types of muscle fibers are how fast some fibers contract relative to others and how fibers produce ATP. Using these criteria, there are three main types of skeletal muscle fibers. Slow oxidative fibers contract relatively slowly and use aerobic respiration, oxygen and glucose, to produce ATP. Fast oxidative fibers have fast contractions and primarily use aerobic respiration but because they may switch to anaerobic respiration, glycolysis, can fatigue more quickly than slow oxidative fibers. Lastly, fast glycolytic fibers have fast contractions and primarily use anaerobic glycolysis. The fast-glycolytic fibers fatigue more quickly than the others. Most skeletal muscles in a human contain all three types, although in varying proportions. 

The speed of contraction is dependent on how quickly myosin’s ATPase hydrolyzes ATP to produce cross-bridge action. Fast fibers hydrolyze ATP approximately twice as quickly as slow fibers, resulting in much quicker cross-bridge cycling which pulls the thin filaments toward the center of the sarcomeres at a faster rate. The primary metabolic pathway used by a muscle fiber determines whether the fiber is classified as oxidative or glycolytic. If a fiber primarily produces ATP through aerobic pathways it is oxidative. More ATP can be produced during each metabolic cycle making the fiber more resistant to fatigue. Glycolytic fibers primarily create ATP through anaerobic glycolysis, which produces less ATP per cycle. As a result, glycolytic fibers fatigue at a quicker rate. 

The oxidative fibers contain many more mitochondria than the glycolytic fibers, because aerobic metabolism, which uses oxygen (O2) in the metabolic pathway, occurs in the mitochondria. The slow oxidative fibers possess a large number of mitochondria and are capable of contracting for longer periods because of the large amount of ATP they can produce, but they have a relatively small diameter and do not produce a large amount of tension. Slow oxidative fibers are extensively supplied with blood capillaries to supply O2 from the red blood cells in the bloodstream. The slow oxidative fibers also possess myoglobin, an O2-carrying molecule similar to O2-carrying hemoglobin in the red blood cells. The myoglobin stores some of the needed O2 within the fibers themselves and gives slow oxidative fibers their red color. All of these features allow slow oxidative fibers to produce large quantities of ATP, which can sustain muscle activity without fatiguing for long periods of time. 

The fact that slow oxidative fibers can function for long periods without fatiguing makes them useful in maintaining posture, producing isometric contractions, stabilizing bones and joints, and making small movements that happen often but do not require large amounts of energy. They do not produce high tension, and thus they are not used for powerful, fast movements that require high amounts of energy and rapid cross-bridge cycling. 

Fast oxidative fibers are sometimes called intermediate fibers because they possess characteristics that are intermediate between fast fibers and slow fibers. They produce ATP relatively quickly, more quickly than slow oxidative fibers, and thus can produce relatively high amounts of tension. They are oxidative because they produce ATP aerobically, possess high amounts of mitochondria, and do not fatigue quickly. However, fast oxidative fibers do not possess significant myoglobin, giving them a lighter color than the red slow oxidative fibers. Fast oxidative fibers are used primarily for movements, such as walking, that require more energy than postural control but less energy than an explosive movement, such as sprinting. Fast oxidative fibers are useful for this type of movement because they produce more tension than slow oxidative fibers, but they are more fatigue-resistant than fast glycolytic fibers. 

Fast glycolytic fibers primarily use anaerobic glycolysis as their ATP source. They have a large diameter and possess high amounts of glycogen, which is used in glycolysis to generate ATP quickly to produce high levels of tension. Because they do not primarily use aerobic metabolism, they do not possess substantial numbers of mitochondria or significant amounts of myoglobin and therefore have a white color. Fast glycolytic fibers are used to produce rapid, forceful contractions to make quick, powerful movements. These fibers fatigue quickly, permitting them to only be used for short periods. Most muscles possess a mixture of each fiber type. The predominant fiber type in a muscle is determined by the primary function of the muscle. 

Human skeletal muscle is composed of a heterogenous collection of muscle fiber types.1–3 This range of muscle fiber types allows for the wide variety of capabilities that human muscles display. In addition, muscle fibers can adapt to changing demands by changing size or fiber type composition. This plasticity serves as the physiologic basis for numerous physical therapy interventions designed to increase a patient's force development or endurance. Changes in fiber type composition also may be partially responsible for some of the impairments and disabilities seen in patients who are deconditioned because of prolonged inactivity, limb immobilization, or muscle denervation.2 Over the past several decades, the number of techniques available for classifying muscle fibers has increased, resulting in several classification systems. The objective of this update is to provide the basic knowledge necessary to read and interpret research on human skeletal muscle. 

Muscle fiber types can be described using histochemical, biochemical, morphological, or physiologic characteristics; however, classifications of muscle fibers by different techniques do not always agree.1 Therefore, muscle fibers that may be grouped together by one classification technique may be placed in different categories using a different classification technique. A basic understanding of muscle structure and physiology is necessary to understand the muscle fiber classification techniques.

Example: Track and Field Runner

100  meter yard dash - Fast Twitch B Muscle Fiber 

1,000 meter yard run - Fast Twitch A Muscle Fiber 

10,000 meter marathon - Slow Twitch Muscle Fiber

Example:  Baseball Player

Designated home run hitter - Fast Twitch B Muscle Fiber 

Designated Runner to steal base - Fast Twitch B Muscle Fiber

Lead off Hitter (Primarily to Hit Singles & Doubles) -  Fast Twitch A Muscle Fiber

 
This work is licensed under a Creative Commons Attribution 4.0 International License.