Anatomy of the Sacrum
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Questions and Answers

What forms the axillary vein?

  • Union of azygos vein and cephalic vein
  • Union of basilic vein and brachial veins (correct)
  • Union of subclavian vein and anterior jugular vein
  • Union of superficial veins and deep veins
  • Where does the axillary vein empty to become the subclavian vein?

  • At the lateral border of the 1st rib (correct)
  • At the superior border of the scapula
  • At the inferior border of the teres major
  • At the medial border of the 1st rib
  • Which lymph nodes receive lymph from other axillary lymph nodes?

  • Thoracic lymph nodes
  • Lateral lymph nodes
  • Subclavian lymph nodes
  • Apical lymph nodes (correct)
  • What is the primary source of the brachial plexus?

    <p>Anterior rami of C5-T1 nerves</p> Signup and view all the answers

    How many trunks does the brachial plexus typically divide into?

    <p>Three trunks</p> Signup and view all the answers

    What structure forms the intermediate sacral crests?

    <p>Fused articular processes</p> Signup and view all the answers

    Which trunk of the brachial plexus is formed from the union of the C5 and C6 roots?

    <p>Superior trunk</p> Signup and view all the answers

    Which vertebrae lack an intervertebral disc?

    <p>C1 and C2</p> Signup and view all the answers

    What structure does not typically drain into the subclavian lymphatic trunk?

    <p>Lateral cervical nodes</p> Signup and view all the answers

    What is the primary role of intervertebral (IV) discs?

    <p>Permit movement and serve as shock absorbers</p> Signup and view all the answers

    What sections does each trunk of the brachial plexus divide into?

    <p>Anterior and posterior divisions</p> Signup and view all the answers

    Where are uncovertebral joints located?

    <p>Between C3–C6 vertebrae and superior vertebral bodies</p> Signup and view all the answers

    What characterizes the nucleus pulposus in an intervertebral disc?

    <p>Gelatinous central mass</p> Signup and view all the answers

    Which of the following joints are classified as symphyses?

    <p>Intervertebral joints</p> Signup and view all the answers

    What feature projects inferiorly on either side of the sacral hiatus?

    <p>Sacral cornua</p> Signup and view all the answers

    What is the main function of the lateral sacral crests?

    <p>Indicate the location of sacral hiatus</p> Signup and view all the answers

    What structure demarcates the proximal end of the radius from its shaft?

    <p>Radial tuberosity</p> Signup and view all the answers

    Which carpal bone is located on the medial aspect of the proximal row of carpals?

    <p>Scaphoid</p> Signup and view all the answers

    What type of shape does the lunate carpal bone resemble?

    <p>Moon</p> Signup and view all the answers

    Which of the following statements about the radial styloid process is true?

    <p>It extends farther distally than the ulnar styloid process.</p> Signup and view all the answers

    What is the function of the dorsal tubercle of the radius?

    <p>To serve as a pulley for tendon passage</p> Signup and view all the answers

    Which bone in the distal row of carpals has a wedge shape?

    <p>Trapezoid</p> Signup and view all the answers

    The medial concavity at the distal end of the radius is known as what?

    <p>Ulnar notch</p> Signup and view all the answers

    Which bone in the proximal row of carpals is boat-shaped and features a prominent scaphoid tubercle?

    <p>Scaphoid</p> Signup and view all the answers

    What is the primary function of the intrinsic back muscles?

    <p>Maintaining posture and controlling movements of the vertebral column</p> Signup and view all the answers

    Which of the following muscles is NOT part of the erector spinae group?

    <p>Latissimus dorsi</p> Signup and view all the answers

    What is the primary role of the semispinalis muscle within the transversospinales group?

    <p>Spanning four to six vertebral segments</p> Signup and view all the answers

    Which layer of intrinsic back muscles is considered the most superficial?

    <p>Superficial layer</p> Signup and view all the answers

    How are the erector spinae muscles arranged relative to the vertebral column?

    <p>In a 'groove' on each side of the vertebral column</p> Signup and view all the answers

    What distinguishes the multifidus muscle of the transversospinales group from others?

    <p>It spans two to four segments.</p> Signup and view all the answers

    In terms of attachments, where do the deep back muscles generally originate?

    <p>From the transverse processes of vertebrae to the spinous processes of superior vertebrae</p> Signup and view all the answers

    What primarily differentiates intrinsic back muscles from extrinsic back muscles?

    <p>Intrinsic muscles originate in the back and extrinsic in other regions.</p> Signup and view all the answers

    What is the primary clinical sign of radial nerve injury?

    <p>Wrist-drop</p> Signup and view all the answers

    Which muscles are primarily affected by a musculocutaneous nerve injury?

    <p>Coracobrachialis, biceps, and brachialis</p> Signup and view all the answers

    What anatomical structure lies between the biceps tendon and the median nerve in the cubital fossa?

    <p>Brachial artery</p> Signup and view all the answers

    What happens to the triceps muscle when the radial nerve is injured at the radial groove?

    <p>Weakness of the triceps only</p> Signup and view all the answers

    Which nerve supplies sensation to the lateral surface of the forearm?

    <p>Musculocutaneous nerve</p> Signup and view all the answers

    What structure is located anterior to the brachial artery in the cubital fossa?

    <p>Median cubital vein</p> Signup and view all the answers

    Which of the following best describes the role of the radial nerve?

    <p>Innervates the extensor muscles of the wrist and fingers</p> Signup and view all the answers

    After an injury to the musculocutaneous nerve, what major action is weakened?

    <p>Flexion of the elbow</p> Signup and view all the answers

    Study Notes

    Sacral Anatomy

    • Fused articular processes form intermediate sacral crests.
    • Fused tips of transverse processes create lateral sacral crests.
    • Sacral hiatus is an inverted U-shape leading into the sacral canal, which is the inferior part of the vertebral canal.
    • Sacral cornua project inferiorly, aiding in locating the sacral hiatus.
    • Auricular articular surface on the lateral sacrum participates in the sacroiliac joint.
    • Coccyx typically consists of four fused vertebrae.

    Vertebral Column Organization

    • Intervertebral (IV) discs are secondary cartilaginous joints for weight-bearing and strength.
    • IV discs connect adjacent vertebrae, acting as shock absorbers with resilient deformability.
    • Each IV disc comprises anulus fibrosus (outer fibrous part) and nucleus pulposus (gelatinous central mass).
    • No IV disc exists between C1 (atlas) and C2 (axis) vertebrae; the lowest disc is between L5 and S1.

    Uncovertebral Joints

    • Located at posterolateral margins of cervical IV discs (C3–C6).
    • Uncovertebral joints (of Luschka) connect uncus of vertebrae to adjacent vertebral bodies.
    • Common sites for spur formation can lead to neck pain.

    Muscle Organization of the Back

    • Intrinsic back muscles are classified by layers: superficial, intermediate, and deep.
    • Superficial muscles (e.g., splenius cervicis and splenius capitis) arise medially and extend to cervical vertebrae and cranium.
    • Erector spinae muscles, chief extensors of the vertebral column, consist of three columns:
      • Iliocostalis (lateral)
      • Longissimus (intermediate)
      • Spinalis (medial)
    • Each column is regionally divided based on superior attachments (e.g., iliocostalis lumborum).

    Deep Intrinsic Back Muscles

    • Transversospinales group includes semispinalis, multifidus, and rotatores.
    • These muscles connect transverse processes to spinous processes of more superior vertebrae.
    • Semispinalis spans multiple segments, while multifidus covers fewer segments.

    Upper Extremity Anatomy

    • The wrist consists of eight carpal bones, arranged into two rows: proximal and distal.
    • Proximal row bones (lateral to medial):
      • Scaphoid (boat-shaped)
      • Lunate (moon-shaped)
      • Triquetrum (three-cornered)
      • Pisiform (pea-shaped)
    • Distal row bones (lateral to medial):
      • Trapezium (four-sided)
      • Trapezoid (wedge-shaped)
      • Capitate and hamate (specific shape not defined in detail).

    Brachial Plexus Formation

    • Brachial plexus is a nerve network supplying the upper limb, arising from C5–T1 anterior rami.
    • Roots pass between anterior and middle scalene muscles.
    • In the neck's inferior part, roots unite to form three trunks:
      • Superior trunk (C5 + C6)
      • Middle trunk (C7)
      • Inferior trunk (C8 + T1)

    Axillary Artery and Vein

    • The axillary vein forms from accompanying brachial veins and the basilic vein at the teres major's inferior border.
    • Drainage from axillary lymph nodes progresses to supraclavicular nodes and the subclavian lymphatic trunk.

    Nerve Injuries

    • Musculocutaneous nerve injury leads to weakened elbow flexion and forearm supination.
    • Radial nerve injury can cause "wrist drop," impairing wrist and finger extension.
    • Radial nerve injuries vary in severity based on injury location but may leave some muscle function intact.

    Cubital Fossa Contents

    • The cubital fossa contains terminal brachial artery branches, the biceps brachii tendon, and the median and radial nerves.
    • Median cubital vein lies anterior to the brachial artery, with medial and lateral cutaneous nerves connected to major veins.

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    Description

    Explore the detailed anatomy of the sacrum in this quiz, focusing on structures such as the sacral crests, hiatus, and cornua. Understand the significance of the auricular surface and its role in the sacro-iliac joint. Test your knowledge on these key anatomical features.

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