Human Anatomy Midterm Review 1 - Extrinsic Back Muscles

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Questions and Answers

What is the primary function of the multifidus muscle group?

Extend across several vertebral segments

Assist in lateral flexion of the trunk

Facilitate contralateral rotation

Stabilize the spine and support posture (correct)

Which muscles are known for being the shortest and most obliquely angled?

Semispinalis

Rotatores (correct)

Interspinales

Levatores costarum

How many vertebral levels do the multifidus muscles typically span?

2-4 (correct)

3-5

5-7

1-2

Which layer of thoracolumbar fascia is the most superficial?

Superficial layer Signup and view all the answers

What is the main action of the muscles within the thoracolumbar fascia?

Provide stabilization and maintain posture Signup and view all the answers

Which of the following muscles do NOT directly aid in trunk rotation or stabilization?

Intertransversarii Signup and view all the answers

The innervation of most intrinsic back muscles primarily comes from which part of the spinal nerves?

Posterior primary rami Signup and view all the answers

Which muscles connect to the same numbered rib in the thoracic region?

Levatores costarum Signup and view all the answers

What muscle group originates from the sacrum and near the PSIS of the ilium?

Multifidus Signup and view all the answers

What is the primary role of the deep minor intrinsic muscles of the back?

Maintaining space between vertebral segments Signup and view all the answers

Which muscles are considered extrinsic trunk muscles?

Trapezius, Latissimus dorsi, Rhomboids Signup and view all the answers

What is the primary function of the serratus posterior superior and inferior muscles?

To elevate the ribs during inhalation Signup and view all the answers

Which of the following muscles run in the opposite direction to the external intercostals?

Internal intercostals Signup and view all the answers

Where does the neurovascular bundle run in relation to the intercostal muscles?

Between the internal intercostals and the innermost muscles Signup and view all the answers

Which muscle connects to the transverse process of C1?

Splenius cervicis Signup and view all the answers

What is the significance of the T10 dermatome?

Lines up directly with the umbilicus Signup and view all the answers

Which of the following muscles is most lateral in the erector spinae group?

Iliocostalis Signup and view all the answers

Which muscles are mainly responsible for isometric and eccentric work while bending to touch toes?

Erector spinae muscles Signup and view all the answers

Which group of muscles includes the transversospinales?

Deep intrinsic back muscles Signup and view all the answers

Which blood supply comes from the thoracic aorta?

Ribs 3-7 Signup and view all the answers

Study Notes

Extrinsic Trunk Muscles

Superficial: Closest to the surface, move the arm/shoulder
- Trapezius: Large, triangular muscle covering the upper back
- Latissimus Dorsi: Wide, flat muscle covering the lower back
- Rhomboids: Two muscles (minor and major) situated beneath the trapezius
- Levator Scapula: Elevates shoulder blade
Intermediate: Deeper than superficial muscles, move the ribs.
- Serratus Posterior Superior
- Serratus Posterior Inferior

Muscles of the Thorax

Intercostal muscles: Occupy spaces between the ribs.
- External Intercostals: Run diagonally, posterior-superior to anterior-inferior, elevate ribs during inhalation.
- Internal Intercostals: Run in the opposite direction of external intercostals, depress ribs during exhalation.
- Innermost Intercostals: Deepest layer of intercostal muscles
- Subcostalis: Spans across multiple ribs
- Transversus Thoracis: Fans out like a star, continuous with the transversus abdominis muscle.
- Levator Costarum: Elevates the ribs.

Neurovascular Bundle

Located between internal and innermost intercostal muscles.
Contains a vein, artery, and nerve arranged from superior to inferior.
Blood supply:
- Uppermost (ribs 1 and 2): Axillary artery
- Ribs 3-7: Thoracic aorta
- Ribs 8 and below: Internal thoracic artery (branch of subclavian artery)

Dermatomes in the Thorax

Direct sensory distribution from spinal nerves, no nerve plexuses.
T4 dermatome: Approximately aligns with the upper nipple line.
T10 dermatome: Aligns with the umbilicus.

Intrinsic Back Muscles

Muscles that attach only within the trunk, purely act on the trunk.

Superficial Intrinsics

Splenius Cervicis: Connects to the transverse process of C1, helps rotate, extend, and laterally flex the neck.
Splenius Capitis: Connects to the skull, helps rotate, extend, and laterally flex the head.

Intermediate Intrinsics: Erector Spinae

Group of three muscles: Iliocostalis, Longissimus, and Spinalis.
Iliocostalis: Lateralmost muscle, runs from sacrum and lumbar fascia to ribs and cervical transverse processes.
Longissimus: Middle muscle, attaches from the fascia of the sacrum and pelvis to ribs, thoracic and cervical transverse processes, and the mastoid process.
Spinalis: Most medial muscle, originates from the fascial band and attaches to the spinous process of thoracic and cervical regions and the cranium.
Pneumonic: "I Luv Spaghetti" helps remember the order of the muscles.

Deep Intrinsics

Transversospinales: Group of muscles involved in rotating the back.
- Semispinalis: Longest muscle, runs through the thorax, cervical region, and up to the head.
- Multifidus: Slightly shorter fibers, span 2-4 vertebral levels, critical for back stability and pain management.
- Rotatores: Shortest muscle fibers, obliquely angled, crossing one or two vertebral levels.

Deep Minor Intrinsics

Interspinales: Lie between spinous processes.
Intertransversarii: Fill in the gap between consecutive transverse processes.
Levatores Costarum: Extend from transverse processes to the same numbered rib in the thoracic region, stabilize ribs.

Actions of the Back Muscles

Extension: Return trunk to an erect posture.
Isometric: Maintain posture.
Side Bending: Lateral flexion.
Rotation: Twisting motion.

Thoracolumbar Fascia

Connective tissue sheet that covers the back muscles.
Superficial Layer: Subcutaneous, adipose.
Deep Layer: Splits into two or three laminae, attaches to spinous and transverse processes, envelops erector spinae and transversospinales, connects to abdominal muscles.

Innervation of Back Muscles

Intrinsic Back Muscles: Posterior primary rami of spinal nerves.
Extrinsic Back Muscles: Anterior primary rami of spinal nerves.
Sinuvertebral Nerves: Innervate the outer components of intervertebral discs and connective tissue.

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Description

This quiz explores the extrinsic trunk muscles and the muscles of the thorax, focusing on their location, characteristics, and functions. Test your knowledge on important muscles such as the trapezius, latissimus dorsi, intercostals, and more. Perfect for students of anatomy and physiology!