Musculoskeletal System and Anatomy - NCLEX-PN

The largest unit of muscle tissue is the fascicle. Each fascicle is made up of a bundle of muscle fibers, and every muscle fiber is made up of many fibrils (called myofibrils).

The muscle body is encased in a fibrous elastic sheath called the epimysium (epi meaning on or above and mys meaning muscle). It is composed of dense irregular connective tissue and is continuous with tendon fibers. The perimysium surrounds muscle fascicles, while the endomysium surrounds muscle fibers.

The only type of muscle that is not striated is smooth muscle. Smooth muscle does not use sarcomeres for contraction - rather, each muscle cell is a spindle that is covered in a mesh of contractile fibrils. These fibrils contract in unison when calcium enters the cell.

The inferior alveolar nerve exits through the mental foramina of the chin. This nerve is a branch of the mandibular nerve and supplies sensory innervation to the lower teeth. The foramen rotundum transmits the maxillary nerve. The supraorbital foramina transmit the supraorbital artery, vein, and nerve. The greater palatine foramen is located in the palatine bone and transmits the greater palatine nerve, artery, and vein.

The falx cerebri, the dura that separates the two hemispheres of the brain, attaches to a bony projection of the ethmoid bone called the crista galli, or "crest of the rooster." This projection is a distinct landmark that arises from the cribiform plate. The ethmoidal labyrinth and orbital plate do not form any attachments to the dura of the brain.

The scapula has multiple fossa that serve as attachment points of various bones and muscles of the shoulder. Among these are the glenoid fossa, where the head of the humerus articulates with the scapula, the subscapular fossa, which is an attachment for the subscapularis muscle, the infraspinous fossa, to which the infraspinatus attaches, and the supraspinous fossa, to which the supraspinatus muscle attaches. There is no suprascapular fossa on the scapula.

The supraspinatus tendon passes under the acromion, a bony hook-like process at the end of the scapular spine. Inflammation of the supraspinatus muscle or tendon can quickly lead to entrapment of this muscle under the acromion, causing pain and reduced mobility. The coracoid process, another projection from the anterior scapula, is an attachment point for several muscles and ligaments, including the pectoralis minor and the short head of the biceps brachii.

The pelvis is formed by the sacrum and coccyx and the three bones that come together to form the innominate: the ilium, ischium, and the pubis. The ileum is a part of the small intestine.

The large, fan-like ridge of bone that can be felt just under the waist is the iliac crest. The anterior superior iliac spine and the anterior inferior iliac spine are smaller protuberances on the ilium that are important landmarks for assessing malpositions of the bones of the sacroiliac joint. The greater sciatic notch is in the posterior ilium and serves as a passage for several muscles and nerves of the pelvic girdle.

The head of the femur rests in the acetabulum, a bony socket on the lateral pelvis that is formed by all three bones of the innominate (the ischium, ilium, and the pubis). The pubic symphysis is a midline cartilaginous joint between the pubic bones. The obturator foramen is an opening in the innominate through which multiple nerves and vessels pass. The pubic tubercle is a bony projection on the pubis that serves as an attachment point for inguinal ligament.

All of the bones listed form the posterior portion of the foot. The largest bone in the foot is the calcaneus. It forms the heel and articulates with the bones of the ankle.

The bones that form the anterior half of the foot (but not the toes) are the metatarsals. These are mirrored in the metacarpal bones of the hand. The carpal bones form the wrist, and the phalanges form the toes and the fingers.

Long bones are lengthened during childhood and adolescence via a process referred to as endochondral ossification. In this process, chondrocytes of the growth plate hypertrophy and eventual die, leaving cavities that are then colonized by osteoprogenitor cells. These osteoprogenitor cells then differentiate into osteoblasts, which mineralize the newly forming bone. None of the other answers are actual processes in bone formation or physiology.

There are five distinct zones in regions of endochondral ossification. These are the resting zone, the zone of proliferation, the zone of maturation, the zone of calcification, and the zone of ossification.

The head of the femur articulates with the acetabulum, a concave surface on the pelvis formed by the union of three bones: the ilium, the ischium, and the pubis.

The obturator foramen is a large opening in the pelvis formed by the pubis and the ischium bilaterally. It does not form any joints but rather allows the passage of the obturator artery, nerve, and vein.

The glenoid fossa is the surface onto which the head of the humerus articulates in the shoulder, and the patella is a part of the knee.

Bursae are synovial fluid sac between bones and overlying tissues. They provide a cushion between the bone and tendons or musculature around them, allowing for reduced friction and painless movement.

A tendon is a connective tissue point of attachment of muscle to bone, while a ligament is a connective tissue attachment from bone to bone. A capsule is a fibrous, fluid filled structure surrounding a synovial joint.

Bruxism, or involuntary tooth grinding, can cause inflammation and damage in the temporomandibular joint, which is the articulation between the condyle of the mandible and the temporal bone.

The xiphisternal joint is between the xiphoid process and the body of the sternum. The intermetacarpal joints are formed between the metacarpal bones of the hand, and the pisotriquetral joint is between the pisiform and triquetrum of the wrist.

Movement along a sagittal plane that decreases the angle between bones is flexion. This is in contrast to extension, which is movement along a sagittal plane that increases the angle between bones. Adduction is movement that pulls a structure toward the midline of the body, while abduction moves a structure away from midline.

Circumduction is movement that produces a circular motion wth the distal end of a body part. True circumduction allows for a 360 degree range of movement. Of the joints listed, the only one capable of circumduction is the shoulder.

Condyloid joints are a form of synovial joint in which a condyle rests in an ovoid cavity. Of the joints listed, the only condyloid joint is the metacarpophalangeal joints (the joint of the most proximal knuckle).

The acromioclavicular joint is a plane joint, while the glenohumeral and humeroradial joints are both ball and socket joints.