A & P Chapter 2: Muscles of Respiration

Diaphragm Innervation

Diaphragm Innervation

- Innervated by the Phrenic Nerve
- Innervated by the spinal nerves C3, C4, C5

Diaphragm Attachment

- Attaches to the vertebrae in the back and the ribs & sternum in the front.

Central Tendon

- Sheet-like tendon in the intermediate region of the diaphragm.

Diaphragm Function

- Dome shaped at rest.
- When the muscles contract, the dome flattens out.
o It returns to the dome shape when back at rest.
- Where the diaphragm goes, the lungs go because they both have pleural lining.
o When it lowers = air comes into the lungs.
o When it raises (relaxes) = air exits the lungs.

Diaphragm Components

- Foramen Vena Cava
- Esophageal Hiatus
- Abdominal Aorta
- Costal Attachment
- Vertebral Attachment
- Sternal Attachment

Abdominal Aorta

- Where the aorta comes through the diaphragm.

Vertebral Attachment

- Where the diaphragm attaches to the spinal column.

Sternal Attachment

- Where the diaphragm attaches to the sternum.

Mediastinum

- Space deep in the bony thorax.
- Houses the heart.
- Covered in pleural lining.

Accessory Muscles of Inspiration Types:

- External Intercostal
- Internal Intercostal, interchondral portion
- Levatores Costarum, Brevis and Longis
- Serratus Posterior Superior
- Sternocleidomastoid
- Scalenes
- Trapezius
- Pectoralis, Major and Minor
- Serratus Anterior
- Subclavius
- Levator Scapulae
- Rhomboideus

Intercostals

- Within the rib cage.
- 3 Types:
o External: Inspiration
o Internal: Expiration
• EXCEPT, Chondral Portion: Inspiration
o Innermost: Expiration

Internal Intercostals - Interchondral Portion

- Stronger in the ventral area.
- Elevates ribs 2 through 12.

Internal Intercostals (interchondral portion) - Origin, Insertion, Innervation

- Origin: Superior margin of ribs 2-12
- Insertion: inferior surface of the ribs above.
- Innervation: Intercostal Nerves, Spinal Nerves T1-T11

Levator Costarum Brevis

- Origin: The transverse processes of vertebrae C7-T11.
- Insertion: The tubercle of the rib below.
o (short and rib-to-rib).

Serratus Posterior Superior

- (sawtooth back above)
- Elevates the ribs 2-5.
o More powerful movement than the intercostals.

Serratus Posterior Superior - Origin, Insertion, Innervation

- Origin: Spinous processes of vertebrae C7 and T1-T3
- Insertion: Just beyond the angles of ribs 2-5
- Innervation: Spinal Nerves T2-T5

Accessory Muscles of the Neck - Function

- Important for inspiration.
- Source of stability.
- Control neck tension and flexion.

Sternocleidomastoid

- Breakdown
o Sterno = sternum
o Cleido = clavicle
o Mastoid = mastoid process
- Comprised of 2 heads:
o Sternal Head
o Clavicular Head

Scalenes

- Function: Help with rotation and stabilization of the head/neck.

Trapezius - Origin, Insertion, Innervation

- Origin: Spinous processes of C2-T12
- Insertion: Scapula and Clavicle
- Innervation: Cranial Nerve 11, XI Accessory

Muscles of the Upper Arm and Shoulder - Function

- Allows the thorax to get deeper (increase anterior-posterior dimension).
- Provides stabilization and strength for respiration.

Pectoralis Major

- Has a radiant form (fan shape)
- Provides bulk to the chest.
- Function: Elevates sternum and increases the dimension of the rib cage.

Pectoralis Major - Origin, Insertion, Innervation

- Origin: At the clavicle and sternum.
- Insertion: In the humerus.
- Innervation: Superior branch of brachial plexus (spinal nerves C5-C8 & T1)

Pectoralis Minor

- Deep to the pectoralis major.
- Function: Increases the dimension of the rib cage & helps extend the shoulder for long reach.

Serratus Anterior

- (sawtooth front)
- Large sawtooth fingers that lie over the ribs.
- Function: Raises the rib cage

Subclavius

- (not everyone has it)
- Small muscle
- Function May elevate 1st rib during inspiration (contribution is uncertain)

Levator Scapulae

- Function: Elevates the scapula
- Secondary Function: Provides neck support.

Rhomboideus Major

- Deep to the trapezius
- Function: Support of upper body and stability for shoulder girdle.

Rhomboideus Major - Origin, Insertion, Innervation

- Origin: Spinous processes of T2-T5
- Insertion: Scapula
- Innervation: C4 and C5

Rhomboideus Minor

- Deep to trapezius
- Function: Stabilizes shoulder girdle

Muscles of Forced Expiration

- Thoracic Muscles of Expiration
- Abdominal Muscles of Expiration
- Muscles of the Upper Limb

Thoracic Muscles of Expiration

- Anterior/Lateral Muscles
o Internal Intercostals (interosseous portion)
o Transverse Thoracis
o Innermost Intercostals
- Posterior Muscles
o Subcostals
o Serratus Posterior Inferior

Internal Intercostals Interosseous Portion - Origin, Insertion, Innervation

- Origin: Superior margin of ribs 2-12
- Insertion: Inferior surface of rib above
- Innervation: Intercostal nerves, Spinal nerves T2-T11

Transverse Thoracis

- Transverse muscles of the thorax (go side to side)
- On the inner surface of the rib cage
- Function: To resist the elevation of the rib cage and decrease the volume of the thoracic cavity.

Innermost Intercostals - Origin, Insertion, Innervation

- Origin: Superior margin of the lower rib (ribs 1-11)
- Insertion: Inferior surface of rib above
- Innervation: Intercostal Nerves, Spinal Nerves T2-T11

Subcostals

- Found on the inner posterior wall of the thorax.
- May span more than 1 rib.
- Form a slight V-shape angle.
- Function: Depress thorax

Serratus Posterior Inferior

- (sawtooth back lower)
- Function: Pull the rib cage down

Serratus Posterior Inferior - Origin, Insertion, Innervation

- Origin: Spinous processes of T11, T12, L1-L3
- Insertion: Inner margin of lower 5 ribs
- Innervation: Spinal Nerves T9-T12

Transverse Abdominis

- Deepest of the anterior muscles
- Runs Lateral (horizontally) to the rectus abdominis
- Top fibres attach to lower ribs and lower fibers attach to the pelvis.
- Most powerful muscle in compressing viscera
o Because it is so big

Internal Oblique Abdominis

- Located between the external oblique and the transverse abdominis.
- Function: Rotates trunk, flexes trunk, compresses abdomen

External Oblique Abdominis

- Most superficial
- Function:
o Bilateral contraction (flex both sides) = flex vertebral column - bending over
o Unilateral contraction = Trunk rotation

Rectus Abdominis

- Prominent midline muscles.
- Rectangular shape.
- Covered by abdominal aponeurosis.
- Function: Pull sternum toward pelvis and compress viscera.

Rectus Abdominis - Origin, Insertion

- Origin: Originates at the pubis inferiorly as 4 or 5 segments.
- Insertion: Xiphoid process & cartilage of ribs 5-7, & the lower ribs.

Abdominal Aponeurosis

- Flat sheath of tendon.
- Where all the abdomen muscles attach.
- Hold things in and make them tight.

Quadratus Lumborum

- Flat vertical muscle
- Function:
o Bilateral Contraction = fixes the abdominal wall for abdominal compression
o Unilateral Contraction = Allows lateral movement of the trunk.

Latissimus Dorsi

- Fans upward
- Function: Stabilizes chest

Muscles of Respiration

- Muscles of inspiration = muscles for breathing in.
- Muscles of expiration = muscles for breathing out.

Diaphragm

- The primary muscle of inspiration.
- Separates the visceral thorax from the abdomen.
- The only unpaired muscle of inspiration.

Foramen Vena Cava

- Where the vena cava comes through the diaphragm.

Esophageal Hiatus

- Where the esophagus comes through the diaphragm.

Costal Attachment

- Where the diaphragm attaches to the ribs.

Action of the Diaphragm

- Contraction pulls the central tendon of the diaphragm down.
- The contraction increases the vertical dimension of the thorax (up-down dimension).
- The increased dimension of the thorax caused the abdominal viscera to be compressed.

Accessory Muscles of Inspiration

- Accessory muscles of the thorax and neck help promote inspiration.
- Function: to elevate and expand the rib cage.
- We need them for deep breathing.

Accessory Thoracic Muscles

- External Intercostal
- Internal Intercostal, interchondral portion
- Levatores Costarum, Brevis and Longis
- Serratus Posterior Superior

External Intercostals

External Intercostals
- Muscles of inspiration.
- Most superficial of the intercostals.
- Elevates each of the ribs during quiet inspiration.
- Stronger in the dorsal area, So ribs can open and lift.

External Intercostal - Origin, Insertion, Innervation

- Origin: Inferior surface of ribs 1-11.
- Insertion: Upper surface of rib immediately below.
o Slope slightly down towards sternum.
- Innervation: Intercostal Nerves, Spinal Nerves T1-T11.

Levatores Costarum

- Elevates the costal region (rib cage).
- 12 pairs
- 2 types: Brevis & Longis
- Innervated spinal nerves C7-T11

Levator Costarum Longis

- Origin: The transverse processes of T7-T11.
- Insertion: Bypasses the rib below the point of origin and inserts into the next rib.
o (skips a rib and inserts into the 2nd rib below).

Accessory Muscles of the Neck

- Sternocleidomastoid
- Scalenes
- Trapezius (considered neck or back)

Sternocleidomastoid - Sternal Head

- Origin: Mastoid process
- Insertion: Manubrium at the sternum
- Innervation: Cranial Nerve 11, XI Accessory
- Function: Elevates sternum and rib cage.

Sternocleidomastoid - Clavicular Head

- Origin: Mastoid process
- Insertion: Attaches at the clavicle
- Innervation: Cranial Nerve 11, XI Accessory
- Function: Turn head and elevate rib cage.

Scalenes - Origin, Insertion, Innervation

- Origin: From the cervical vertebrae
- Insertion: The upper border of the top 2 ribs
- Innervation: Spinal Nerves C3-C8

Trapezius

- Huge neck and back muscle.
- Fans laterally.
- Function: Elongates the neck, provides head control, provides back support in respiration.

Muscles of the Upper Arm and Shoulder

- Pectoralis Major and Minor
- Serratus Anterior
- Subclavius
- Levator Scapulae
- Rhomboideus Major and Minor
- Trapezius (considered neck or back)

Pectoralis Minor - Origin, Insertion, Innervation

- Origin: Upper ribs
- Insertion: At the end of the scapula near the shoulder.
- Innervation: Superior branch of brachial plexus (spinal nerves C5-C8 & T1)

Serratus Anterior - Origin, Insertion, Innervation

- Origin: Ribs 1-9
- Insertion: Inner vertebral boarder of the scapula
- Innervation: Spinal Nerves C5-C7

Subclavius - Origin, Insertion, Innervation

- Origin: Inferior margin of the clavicle
- Insertion: Superior surface of the 1st rib
- Innervation: Spinal Nerves C5-C6

Levator Scapulae - Origin, Insertion, Innervation

- Origin: Transverse processes of C1-C4
- Insertion: Medial border of scapula
- Innervation: Spinal nerves C3-C5

Rhomboideus Minor - Origin, Insertion, Innervation

- Origin: Spinous processes of C7 and T1
- Insertion: Medial border of scapula
- Innervation: C4 and C5

Internal Intercostals - Interosseous Portion

- Absent in the posterior aspect of the ribcage near the vertebral column.
- Function: Depresses the ribs.

Transverse Thoracis - Origin, Insertion, Innervation

- Origin: Margin of the sternum
- Insertion: Inner chondral surface of ribs 2-6
- Innervation: Spinal Nerves T2-T6

Innermost Intercostals

- Deepest of the intercostal muscles.
- Fibers run between the inner costal surface of adjacent ribs.
- Parallel to the internal intercostals.
- Absent in the chondral portion of the ribs.
- Function: Depress ribs 1-11

Abdominal Muscles of Expiration

- Anterolateral Abdominal Muscles
o Transverse Abdominis
o Internal and External Oblique Abdominis
o Rectus Abdominis
- Posterior Abdominal Muscles
o Quadratus Lumborum

Internal Oblique Abdominis - Origin, Insertion

- Origin: Inguinal ligament and iliac crest
- Insertion: Lower ribs and abdominal aponeurosis

External Oblique Abdominis - Origin, Insertion

- Origin: Osseous portion of the lower 7 ribs.
- Insertion: Iliac crest, inguinal ligament, & abdominal aponeurosis.

Quadratus Lumborum - Origin, Insertion

- Origin: Crest of the pelvis bone (iliac crest)
- Insertion: Inserts into the bottom of the floating ribs and the transverse processes of the lumbar vertebrae.

Muscles of the Upper Limb

- Latissimus Dorsi

Latissimus Dorsi - Origin, Insertion

- Origin: Lumbar, Sacral, and Lower Thoracic Vertebrae.
- Insertion: Humerus