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What is the main action of the rhomboid muscles?
Which muscle is primarily responsible for protracting and stabilizing the scapula?
Which nerve innervates the pectoralis minor muscle?
Which of the following is NOT one of the rotator cuff muscles?
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Where does the supraspinatus muscle insert?
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Which bones make up the pectoral girdle?
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What is a common cause of glenohumeral joint dislocation?
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What is the primary function of the clavicle in the pectoral girdle?
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Which of the following is true regarding the structure of the scapula?
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How does the humerus connect to the forearm?
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Which muscle is involved in the movement of protraction of the shoulder?
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What could likely happen if the clavicle suffers a fracture?
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What best describes the arrangement of the scapulae in the human body?
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What is the primary role of the clavicle in the pectoral girdle?
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Which anatomical feature is NOT part of the scapula?
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How does a clavicular fracture typically affect the shoulder region?
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What is the function of the glenoid cavity in relation to the humerus?
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Which borders of the scapula are characterized by specific shapes?
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Study Notes
Overview of Limb Structure and Function
- Upper and lower limbs share a common general outline, with three analogous sections: arm, forearm, and hand in the upper limb; thigh, leg, and foot in the lower limb.
- The upper limb allows for power movements and fine movements.
Development of Limbs
- Limbs develop during the fifth and seventh weeks of gestation.
Body Movements
- Common limb movements include flexion/extension, abduction/adduction, and lateral/medial rotation.
Protraction vs. Retraction
- Protraction refers to pushing forward, while retraction refers to pulling back.
Osteology of the Upper Limb
- Major bones of the upper limb include the pectoral girdle (scapula and clavicle), humerus, radius, ulna, and bones of the wrist and hand.
The Pectoral Girdle
- Comprises the scapula (posterior) and clavicle (anterior).
- The name "girdle" is a misnomer, as the two scapulae do not physically meet on the back.
- The pectoral girdle provides an attachment point for the upper limb to the axial skeleton and allows for significant movement flexibility.
- The pectoral girdle is highly mobile but can be prone to injury.
Muscles Acting on the Scapula
- Rhomboid muscles (major and minor): retract the scapula and rotate it to depress the glenoid cavity.
- Pectoralis Minor: stabilizes the scapula by drawing it inferiorly and anteriorly.
- Serratus Anterior: protracts and stabilizes the scapula, assisting with upward rotation.
Rotator Cuff Muscles
- Four muscles originate on the scapula and insert on the humerus: subscapularis, supraspinatus, infraspinatus, and teres minor.
- They encircle the shoulder joint, anchoring the head of the humerus into the glenoid cavity.
- Most rotate the humerus medially or laterally, except for supraspinatus, which abducts the arm.
- Supraspinatus, Teres Minor, and Infraspinatus insert into the greater tubercle of the humerus, while Subscapularis inserts into the lesser tubercle.
The Clavicle
- An "S" shaped bone with a sternal end (attaches to the manubrium of the sternum) and an acromial end (attaches to the acromion process of the scapula).
- Acts as a "brace" holding the scapulae and arms laterally from the thorax.
- Transmits compression force from the upper limbs to the axial skeleton.
Clavicular Fractures
- The clavicle is prone to fractures due to its relatively weak structure.
- Fractures result in the collapse of the entire shoulder region medially, highlighting the clavicle's brace-like function.
The Scapulae
- Also known as "shoulder blades", are located on the dorsal rib cage between rib 2 and rib 7.
- Triangular in shape, with superior, medial, and lateral borders.
- The lateral border ends in the glenoid cavity, which articulates with the humerus.
- Three important angles: lateral angle (contains the glenoid cavity), superior angle, and inferior angle.
Key Nerves
- Accessory Nerve (CN XI): innervates the trapezius muscle.
- Dorsal scapular nerve: innervates the rhomboid muscles.
- Medial Pectoral Nerve: innervates the pectoralis minor.
- Long thoracic nerve: innervates the serratus anterior muscle.
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Description
This quiz explores the structure and function of human limbs, including the osteology of the upper limb and the major bone groups. It also covers limb development, common movements, and the concepts of protraction and retraction. Test your understanding of how upper and lower limbs work together in the human body.
