Human Anatomy: Upper Body Muscles

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Questions and Answers

What is the proximal attachment of the Pectoralis Major muscle?

Coracoid process of the scapula

Rib 1

Sternum, clavicle and costal margins of ribs (correct)

Lateral border of rib 1 - 8

Where does the Pectoralis Minor muscle attach proximally?

Costal margins of ribs

Medial margin of scapula

Clavicle

Rib 3 - 5 anteriorly (correct)

What is the proximal attachment point for the Subclavius muscle?

Sternum

Clavicle

Coracoid process of the scapula

Rib 1 (correct)

The Serratus Anterior muscle has its proximal attachment along which of the following?

Lateral border of rib 1 - 8 Signup and view all the answers

Which intercostal muscle is the most superficial layer and has a specific oblique course?

External Intercostal Signup and view all the answers

What is the common proximal attachment for the Intercostal muscles?

Tubercles of the ribs Signup and view all the answers

Intercostal muscles are primarily responsible for what function during respiration?

Expanding the rib cage Signup and view all the answers

The Pectoralis Minor's primary role involves stabilization against which structure?

Scapula against the thoracic wall Signup and view all the answers

What is the proximal attachment site of the serratus posterior superior?

Spinous processes of vertebrae C7-T3 Signup and view all the answers

Which muscle's proximal attachment includes the upper lumbar vertebrae?

Diaphragm (right crus) Signup and view all the answers

What is the correct origin for the internal intercostal muscles?

Angle of the ribs to the vertebral column Signup and view all the answers

Which muscle aids in depressing the ribs and is innervated by the anterior rami of spinal nerves T9-T12?

Serratus posterior inferior Signup and view all the answers

What is the proximal attachment of the muscle fibers of the diaphragm that arise from the lower ribs?

Inner surfaces of the lower six ribs Signup and view all the answers

Which region is NOT a muscular portion origin of the diaphragm?

Sacral origin Signup and view all the answers

Which of the following correctly describes the proximal attachment of the levator scapulae?

Transverse processes of C1 to C4 Signup and view all the answers

Which muscle primarily functions to elevate the ribs and is innervated by the 2nd to 5th intercostal nerves?

Serratus posterior superior Signup and view all the answers

What is the primary sensory innervation of the diaphragm?

Phrenic nerve Signup and view all the answers

Which spinal roots give rise to the phrenic nerve?

C3, C4, C5 Signup and view all the answers

What structures pass through the caval opening of the diaphragm?

Inferior vena cava and phrenic nerve branches Signup and view all the answers

Where is the esophageal opening located in relation to the midline?

Left of the midline Signup and view all the answers

Which of the following is true about the aortic opening?

It is a large gap between the crura. Signup and view all the answers

What is one of the primary functions of the diaphragm?

Principal muscle for inspiration Signup and view all the answers

What happens during the Valsalva maneuver?

The diaphragm contracts and exerts pressure on the thoracic cavity. Signup and view all the answers

How do the right and left crura function in relation to splanchnic nerves?

They permit the passage of greater and lesser splanchnic nerves. Signup and view all the answers

Study Notes

Pectoralis Major

Originates from the sternum, clavicle, and costal margins of ribs.
Inserts at the lateral intertubercular groove of the humerus.
Functions in flexing, adducting, and medially rotating the humerus.
Receives innervation from the medial pectoral nerves (C8-T1) and lateral pectoral nerves (C5-C7).

Pectoralis Minor

Originates from ribs 3-5 anteriorly.
Inserts at the coracoid process of the scapula.
Functions in protracting and stabilizing the scapula against the thoracic wall.
Receives innervation from the medial pectoral nerves (C8-T1).

Subclavius Muscle

Originates from rib 1.
Inserts at the clavicle.
Function is to stabilize the clavicle.
Receives innervation from the nerve to subclavius (C5-C6).

Serratus Anterior

Originates from the lateral border of ribs 1-8.
Inserts at the medial margin of the scapula posteriorly.
Functions in protracting and stabilizing the scapula against the thoracic wall.
Receives innervation from the long thoracic nerve (C5-C7).

Intercostal Muscles

Located in the eleven intercostal spaces, consisting of 3 layers: External Intercostal, Internal Intercostal, and Innermost Intercostal.
Nerves and vessels course between the 2nd and 3rd layer.
Primarily function in respiration.

External Intercostal

The most superficial layer.
Courses obliquely from superior to inferior.
Connects from the tubercles of the ribs to the costochondral joint posteriorly and from the costochondral joint to the sternum anteriorly.
Aids in elevating the ribs, primarily active during inspiration.

Internal Intercostal

The middle layer of the intercostal space.
Positioned perpendicular to the external intercostal muscles.
Extends from the sternum anteriorly to the angle of the ribs posteriorly.
Functions in moving ribs inferiorly, primarily active during expiration.

Innermost Intercostal

The deepest layer of the intercostal spaces.
Aids in depressing the ribs to facilitate expiration.

Trapezius

A superficial back muscle.

Levator Scapulae

A superficial back muscle

Rhomboid Major

A superficial back muscle.

Rhomboid Minor

A superficial back muscle

Latissmus Dorsi

A superficial back muscle

Serratus Posterior Superior

An intermediate back muscle.
Originates from the nuchal ligament and spinous processes of vertebrae C7-T3.
Inserts at the superior borders of ribs 2-5.
Innervated by the 2nd-5th Intercostal nerves.
Functions in elevating the ribs.

Serratus Posterior Inferior

An intermediate back muscle.
Originates from the spinous processes of vertebrae T11-L2.
Inserts at the inferior borders of ribs 9-12.
Innervated by the anterior rami of spinal nerves T9-T12 (9th-11th Intercostal nerves + subcostal nerve).
Functions in depressing ribs and drawing them inferoposteriorly.

Deep Muscles of the Back

Include Iliocostalis, Longissimus, and Spinalis.

Diaphragm Muscle

Divides the thoracic and abdominal cavities.
The primary muscle for inspiration and expiration.
Consists of a peripheral muscular portion and a central tendon.
Dome-shaped and its contraction causes it to descend (flatten).
The right dome is higher due to its position on the liver, while the left dome is lower and sits on the stomach fundus.

Muscular Portion Origins of the Diaphragm

Lumbar Origin: Two crura:
- Left crus: from the bodies of the upper two lumbar vertebrae.
- Right crus: from the bodies of the upper three lumbar vertebrae.
Costal Origin: Muscle fibers arise from the inner surfaces of the lower six ribs.
Sternal Origin: Muscle fibers arise from the inner surface of the xiphoid process.

Diaphragm Insertion

The muscle fibers converge to insert into the central tendon.

Diaphragm Innervation

Right and left phrenic nerves provide sensory and motor innervation.

Sensory Innervation of Diaphragm

Pericardium
Mediastinal and diaphragmatic pleurae
Diaphragmatic peritoneum.

Motor Innervation of Diaphragm

Through the phrenic nerve, which arises from spinal roots C3, C4, and C5.

Phrenic Nerve Pathway

Courses along the anterior surface of the anterior scalene muscle on each side.
Descends into the thoracic cavity between the subclavian vein and artery.
Travels anterior to the root of each lung between the mediastinal pleura and pericardium.

Openings of the Diaphragm

Permit passage of structures between the thorax and abdomen.
Major openings include the Caval, esophageal, and aortic openings.
Smaller openings are provided by the left and right crura.

Caval Opening

Located at the T8 vertebral level within the central tendon, slightly right of the midline.
Allows passage for:
- Inferior vena cava
- Branches of the right phrenic nerve
- Branches of the left phrenic nerve pass through the diaphragm by piercing the central tendon on the left side.

Esophageal Opening

Located to the left of the midline at the T10 vertebral level.
Splits the muscle fibers of the right crus.
Allows passage for:
- Esophagus
- Left and right vagus nerves
- Esophageal branches of the left gastric artery
- Esophageal tributaries of the left gastric vein.

Aortic Opening

Located at the T12 vertebral level, behind the two crura.
Not an opening through the diaphragm, but a large gap between the crura.
Left and right crura form the borders of the opening.
Allows passage for:
- Aorta
- Azygos vein
- Thoracic lymphatic duct

Right and Left Crura

Greater and lesser splanchnic nerves pass from the thoracic cavity deep to the crura.
The left crus allows passage for the hemiazygos vein.

Functions of the Diaphragm

Respiration:
- The primary muscle responsible for inspiration.
- Contraction flattens the diaphragm, increasing the vertical dimensions of the thoracic cavity.
Venous Return:
- Contraction and relaxation create pressure changes in the thoracic and abdominopelvic cavities, facilitating venous blood return to the heart.
Valsalva Maneuver:
- A forceful contraction of the diaphragm against the abdominal viscera.
- Increases intra-abdominal pressure to aid in expelling vomit, feces, and urine.
- Prevents gastric reflux by exerting pressure on the esophagus at the esophageal hiatus.

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Description

Test your knowledge on the anatomy and functions of key upper body muscles including the pectoralis major, pectoralis minor, subclavius, and serratus anterior. This quiz covers their origins, insertions, functions, and innervation. Perfect for students of human anatomy or anyone interested in muscle structure.