A&P PowerPoint 4 (Anatomy of Respiration : Muscles of Respiration)

Alevolar Pressure

* Pascals Law: pressure is transmitted rapidly and uniformly throughout an enclosed fluid at rest. *Tiny alveoli or air sacs in the lungs ** Pascal's law says that the pressure in each of the air sacs is the same. ***Alveolar pressure is uniform throughout the lung. *Alveolar pressure, measured in cm H20, within the alveoli, is the smallest gas exchange unit of the lung. Alveolar pressure is given with respect to atmospheric pressure, which is always set to zero. Thus, when alveolar pressure exceeds atmospheric pressure, it is positive (high); when alveolar pressure is below atmospheric pressure it is negative (low).

Inhalation

* The lungs are spongy bodies which have no muscles and some elasticity. They are controlled by the muscles of respiration: the external intercostal muscles, internal intercostal muscles (lie between cartilaginous part of rib) and the rotation of cartilages raise the ribs. * The diaphragm is convex and is flatten down by contraction, thus enlarging the chest by increasing its depth. The abdominal muscles relax and allow the stomach, liver, and other organs in the abdomen to move downward to make room for the depressed diaphragm. This causes a vacuum (lower or negative air pressure) in the chest. The lungs (due to pleural linkage to rib cage and alveolar pressure) expand to fill this vacuum and the air rushes in to fill the expanding lungs.

Diaphragm: Origins

* Xiphoid process (sternum) *Inferior ribs 7 - 12 * Corpus L1, transverse processes of L1 - L4

Atmospheric Pressure Reference

*All measurements of air pressure are made relative to atmospheric pressure *Example : Vocal Fold Vibration **+3 to +5 cm H20 of subglottic air pressure to set VFs into vibration, a simple "ah" **That is, +3 to +5 cm H2O above atmospheric pressure **+7-10cm H20 - conversational speech *Stress or Prosodic Changes **+2 cm H20

Pressure

*Flow of air depends on the pressure gradient (atmospheric, Pa, and intra-alveolar, Pi) and the airway resistance, R *Resistance depends primarily on the radius of the conducting airways

Pleural Pressure

*Pleural pressure is the pressure surrounding the lung, within the pleural space. The ribcage is lined with a membrane called the costal pleura. There is a second membrane that covers the lungs called the pulmonary or visceral pleura. The pleura allow the lungs to expand and contract as the thoracic cage changes volumes. As volume of the rib cage increases, so does the lung volume due to pleura. *Boyle's Law—Increased volume causes a proportional decrease in pressure.

The respiratory pump

*The spongy lungs can be likened to two balloons that are inflated and deflated as if by a bicycle pump *The basis for the action of the respiratory pump is the way the lungs are linked to the ribcage (thorax) and abdomen by two pleurae (membranes). A layer of fluid between the pleurae allows them to move freely and provides suction to maintain the linkage *The consequence of the linkage is that the lungs expand and contract as the ribcage and abdomen expand and contract *Because volume and pressure are related, altering the lung volume changes the air pressure in the lungs (Pa, Ps) **Increasing lung volume (e.g. by pushing the ribcage or abdomen outwards) lowers air pressure **Decreasing lung volume raises air pressure *Air flows from regions of higher to lower pressure, so air flows into the lungs when pressure decreases below atmospheric level, and out when pressure increases above atmospheric level. *Inspiration/ Inhalation (breathing in) normally involves muscular effort: contracting External intercostal muscles (to elevate ribs) and disphragm (which lowers as it contract, expanding volume of thorax).

Muscles of Forced Expiration : Abdominal Muscles of Expiration

1. Abdominal aponeurosis Function: Tendons to attach anterior abdominal muscles to form wall. 2. Aponeuroses (layers of flat broad tendons) *Linea alba **Xiphoid process to public symphysis *Linea semilunarius *Lumbodorsal fascia (connective tissue surrounding muscle)

Diaphragm : Three openings (hiatuses)

1. Aortic hiatus *Descending abdominal aorta 2. Esophageal hiatus *Esophagus *Small arteries 3. Foramen vena cava *Inferor vena cava, lumph vessels, & nerves

Muscles of Forced Expiration : Muscles of Thorax : Anterior/Lateral Thoracic Muscles

1. Internal Intercostal (interosseous portion) 2. Transversus Thoracis 3. Innnermost Intercostals Function: Depresses ribs & rib cage

Muscles of Forced Expiration : Muscles of Thorax : Posterior Thoracic Muscles

1. Subcostals 2. Serratus Posterior Inferior (One of several muscles of the back and thorax, that have interdigitating slips that ressemble the notches on the cutting edge of a saw.) Functions: Depress thorax Pulls rib cage down

Muscles of Forced Expiration : Abdominal Muscles of Expiration : Anteriolateral abdominals

1. Transverse Abdominis 2. Int. Oblique Abdominis 3. Ext. Oblique Abdominis 4. Rectus Abdominis Functions *Compress abdomen *Rotate & flex trunk; compress abdomen *Flexes veterbral colum

Accessory Muscles of Inspiration

14 muscles *Anterior thoracic M. - 2 *Posterior thoracic M. - 2 *Accessory Neck M. - 2 *Upper arm & shoulder M. - 8

Innervation of the Diaphragm : Phrenic Nerve : How it works

A need for oxygen (sensory) is sent to the medulla obongata (part of brainstem) in the form of neuronal impulses from the brain and spinal cord (sensory impulses). The medulla, then which sends impulses (motor) to phrenic nerve, which innervates the diaphragm. The ribcage which houses the diaphragm is attached anteriorly to the sternum and posteriorly to vertebrae. The diaphragm is the floor of the ribcage. The lungs (spongy with no muscle) rest on the diaphragm. The lining of the ribcage contains costal pleura and a deeper lining around the lungs called pulmonary pleura. The costal and pulmonary pleura work together to enable the lungs to change its shapes as the thorax changes. When the neuronal stimulation is large enough for a contraction, then the diaphragm flattens. The thorax and lungs expand to increase volume and air rushes in.

Insertion

Area of attachment of muscle to the bone it moves.

Five Pressures for Non-Speech & Speech Functions

Atmospheric pressure (P atm) *Ref. measure for earth (760 mm Hg) Intraoral or mouth pressure (P m) *Air pressure measured within the mouth Subglottic pressure (P s) *Air pressure measured below the vocal folds Intrapleural pressure or pleural (P pl) *Air pressure measured between the pleurae Alveolar pressure (P al) *Air pressure measured within individual alveolus *Remember that high pressure moves to low pressure.

Innervation of the Diaphragm : Phrenic Nerve

Bunches of cervical nerves bind to form phrenic nerve. The phrenic nerve innervates the diaphragm.

Diaphragm : Insertions

Central tendon (tough fibrous tissue)

Diaphragm Action

Contraction : Pulls the central tendon down & forward

Forced Expiration / Exhalation : Forced Exhalation : Active Exhalation

During active exhalation, the most important muscles are those of the abdominal wall (including the rectus abdominus, internal and external obliques, and transversus abdominus), which drive intra-abdominal pressure up when they contract, and thus push up the diaphragm, raising pleural pressure, which raises alveolar pressure, which in turn drives air out. The internal intercostals assist with active expiration by pulling the ribs down and in, thus decreasing thoracic volume. This high (positive) pressure forces the air from the lungs and prepares them for another inhalation.

Accessory Muscles of Neck : Scalenus anterior, medius, posterior muscle

FX : Elevates ribs 1 & 2 during respiration; help rotate head

Exhalation in Phases

Inhalation: the abdominal muscles and internal intercostals (rib muscles) relax but not completely, and the external intercostals contract to fully expand the rib cage; the diaphragm contracts and descends, which also enlarges the lung space. Exhalation, first phase: since the rib cage has been expanded more than it is at rest, it will tend to 'relax' back to its rest position if no muscular effort is keeping it expanded; this "relax back" motion is called elastic recoil. The pressure from recoil is all that is needed to start the airflow; in fact, if an especially deep breath was taken, the pressure from the recoil will be greater than desired, and the air pressure will need to be restrained somewhat by continued contraction of the diaphragm Exhalation, second phase: The last of the elastic recoil is used up in this phase, aided by contraction of the internal intercostals. These pressures shrink the rib cage, adding to the lung pressure. Exhalation, third phase: The abdominal muscles are used to provide the last bit of lung pressure possible.

Diaphragm : Innervation & Blood Supply

Innervation: Bilateral Innervation Phrenic nerves *Originates in the cervical plexus **Spinal nerves C3, C4, & C5 from both sides of the spinal cord. *Has both sensory & motor functions

central tendon of diaphragm

Insertion of diaphragm

Muscles of Forced Expiration : Abdominal Muscles of Expiration : Muscles of Upper Limb

Muscle : Latissimus Dorsi Function : For respiration, stablizes posterior abdominal wall for respiration

Muscles of Forced Expiration : Abdominal Muscles of Expiration : Posterior Abdominal Muscles

Muscle: Quadratus Lumborum Function: Bilateral compression fixes abdominal wall to support abdominal compression

Anterior Thoracic Muscles of Inspiration

Muscles *External Intercostal Muscles *Internal Intercostal **Interchondral Portion Functions: *Elevate ribs

Posterior Thoracic Muscle of Inspiration

Muscles *Serratus Posterior Superior *Levatores Costarum **Brevis **Longis Functions: *Elevate ribs

Accessory Muscles of Neck

Muscles *Sternocleidomastoid Muscle *Scalenes 1. Anterior 2. Middle 3. Posterior Functions: *Repiration 1. Elevate sternum, i.e. rib cage 2. Elevate ribs 1 & 2 *Head rotation *Neck flexion & extension stability

Muscles of Forced Expiration

Muscles of thorax: *Anterior/lateral thoracic M. - 3 *Posterior Thoracic M. - 2 Abdominal Muscles of Expiration: *Anteriolateral abdominal M. - 4 *Posterior Abdominal M. - 1 *Upper limb M. - 1 Function: To "squeeze" the air from the lungs *Front-to-back fall of the rib cage *Squeeze abdominal viscera pushing diaphragm upward

Vena Cava

One of two large veins that drain blood directly in the heart. The superior vena cava and inferior vena cava are the two largest veins in the body.

Muscles of Upper Arm & Shoulder : Trapezius M.

Origin : Spinous processes of C2 to T12 Insert.: Acromion of scapula & sup. Surface of clavicle N.: XI (Access); SPN: C2-C4 FX : Elongate neck; head control

Muscles of Upper Arm & Shoulder : Levator Scapulae M.

Origin : Transverse process of C1 -C4 Insert.: Medial border of scapula N.:SPN: C3-C5 FX: Neck support; elevate scapula

Muscles of Upper Arm & Shoulder : Pectoralis Minor M.

Origin: Ant. Surface ribs 2-5 near chondral margin Insert: Coracoid process of scapula N.: SN: C4-C7 & T1 FX: Inc. transverse dimension of rib cage.

Muscles of Upper Arm & Shoulder : Subclavis M.

Origin: Inf surface of clavicle Insert.: Sup. Surface of rib 1 at chrondral margin N.: SPN: C5-C6 FX: Elevates rib 1

Accessory Muscles of Neck : Sternocleidomastoid Muscle

Origin: Mastoid process of temporal bone Insert: Sup. Margin of manubrium sterni N.: XI (Access.N.); from spinal nerves at C2 - C5 FX: Elevate sternum, thus rib cage; rotates head to side of contraction

Muscles of Upper Arm & Shoulder : Serratus Anterior M.

Origin: Ribs 1 - 9, lat. Surface of thorax Insert.: Inner vertebral border of scapula N.:SPN: C5-C7 FX: Elevates ribs 1-9

Muscles of Upper Arm & Shoulder : Rhomboideus Minor M.

Origin: Spinous process of C7 & T! Insert.: Medial border of scapula N.: SPN: C5 FX: Stabilizes shoulder girdle

Muscles of Upper Arm & Shoulder : Rhomboideus Major M.

Origin: Spinous processes T2 - T5 Insert.: Scapula N.: SPN: C5 FX: Stabalizes shoulder girdle

Muscles of Upper Arm & Shoulder : Pectoralis Major M.

Origin: Sternal head : sternum length at costal cart. Insert: Greater tubercle of humerus (humerus - upper bone of arm) N.: SN: C4 - C7 & T1 FX : Elevates sternum increasing transverse dimension of rib cage

Cranial Nerves

Originate from brainstem (Pons & medulla) 12 Cranial nerves

Spinal Nerves

Originate from spinal cord (C1 - coccyx) Names coincide with vertebra location Include *Cervical Plexus *Brachial Plexus

Summary of Muscles Involved

Phase / Muscles involved Inhalation / Diaphragm and/or external intercostals internal inter-costal muscles (lie between cartilaginous part of rib) and the rotation of cartilages raise the ribs. Exhalation Stage 1 / Elastic recoil, diaphragm used to prevent excess pressure from recoil Exhalation Stage 2 / Elastic recoil, internal intercostals, continuing until no more recoil remains Exhalation Stage 3 / Internal intercostals, abdominals

Origin

Place of attachment of a muscle that remains relatively fixed during contraction

Diaphragm

Primary muscle of inspiration Divides thorax from abdomen Dome-shaped underneath ribs *Higher on right side than left *Protects liver, spleen & kidneys

Muscles of Upper Arm & Shoulder

Six muscles: 1. Pectoralis major (thick fan shaped chest muscle on front of thoracic cavity) 2. Pectoralis minor 3. Levator Scapulae M 4. Rhomboideus Major M 5. Rhomboideus Minor M 6. Trapezius M. Accessory functions: Assist external intercostal muscles in elevating the thorax through their attachments to the ribs and sternum.

Exhalation

The movement of air out of the lungs (exhalation) also involves changes in volumes and pressures. However, in breathing at rest, no energy is required to contract the lungs which, being elastic in nature, contract automatically from their expanded state. Think of a bath sponge, which is quite similar in structure to the lungs, if you stretch it (as in inhalation), it will recoil of its own accord when released. The "stretchability" of the lungs is called compliance. The internal intercostals muscles, while not being used in quiet breathing, are necessary for forced expiration such as when coughing or during heavy exercise. Healthy lungs with good compliance recoil automatically and easily, but certain disease conditions such as emphysema, bronchitis, tuberculosis and cystic fibrosis can compromise this process. Mucus that is produced in disease such as bronchitis and asthma can partially block airways and result in ventilation problems (air passage and alveoli).

Phrenic Nerve

The phrenic nerve originates in the neck region of the spine. Its main role is to supply movement to the diaphragm, but it also supplies sensation to the chest and the upper part of the abdomen. The human body has two phrenic nerves --- a left and a right. They both follow different paths; however, they both begin in the C3-C5 vertebral region of the neck. The motor fibers in the phrenic nerves signal to the diaphragm when to contract and relax. If one phrenic nerve is left in tact, the patient will retain his ability to breathe, though it will be more labored. Irritation of the phrenic nerve may cause a hiccup reflex, in which the diaphragm suddenly contracts.

Ensiform process

Xiphoid process

Forced Expiration/ Exhalation : Quiet breathing, expiration is normally passive: the __________ ______________ ___________ of the lungs does most of the work

elastic recoil force

The transpulmonary pressure is the difference between the __________ and the __________ pressure.

pleural pressure and alveolar pressure