Anatomy and Consequences of Coughing

Question 1

summarise the sensory nerve supply to the mucosa lining the nasal cavities, pharynx and larynx

Answer 1

coughing stimulates sensory receptors in oropharyngeal mucosa, laryngopharyngeal muscoa and laryngeal mucosa

nasal cavities - CN V (a, b) - sneezing
pharynx - CN IX - coughing sneezing
larynx - CN X - coughing

Question 2

give a basic definition of the carotid sheath and list the structures enclosed within it

Answer 2

protective tubes of cervical deep fascia
attach superiorly to the bones of the base of the skull
blends inferiorly with the fascia of the mediastinum

contains;
vagus nerve
internal carotid artery
common carotid artery
internal jugular vein

Question 3

give a basic summary of the sensory and motor nerve supply to the lungs (via pulmonary plexus)

Answer 3

visceral pleura and respiratory tree visceral afferents connect to CNS;
all motor axons travel from the tracheal bifurcation along the branches of the respiratory tree to supply all mucous glands and all bronchiolar smooth muscles
the pulmonary visceral afferents travel from visceral pleura and respiratory tree to the pulmonary plexus (containing sympathetic and parasympathetic axons and visceral afferents) then follow the vagus nerve (CN X, in the carotid sheath) to the medulla of the brain stem

Question 4

describe the phrenic nerves

Answer 4

found in the thorax descending over the lateral aspects of the fibrous pericardium anterior to the lung root
in a deep (forced) inspiration a greater outflow of action potentials of longer duration, via phrenic nerve occurs causing the diaphragm to flatten then descend maximally

Question 5

list the accessory muscles of deep inspiration

Answer 5

pectoralis major and minor
sternocleidomastoid
scalenus anterior, medius and posterior

recruitment of these muscles is an important sign of dyspnoea (breathlessness)

Question 6

describe the anatomy of the pectoralis major and minor

Answer 6

major;
attaches between sternum/ribs and humerus
adducts and medially rotates humerus if the upper limb position is fixed (holding onto arm of chair or thigh)
pulls rib upwards/outwards

minor;
can pull ribs 3-5 superiorly towards the caracoid process of the scapula

Question 7

describe the anatomy of the sternocleidomastoid

Answer 7

attaches between sternum/clavicle and mastoid process of temporal bone

Question 8

describe the scalenus anterior, medius and posterior

Answer 8

attach between cervical vertebrae and ribs 1 and 2

Question 9

state the names of the laryngeal cartilages and describe their anatomy

Answer 9

thyroid - rima glottidis
cricoid
artenoid

Question 10

define the rima glottidis

Answer 10

vocal cords and arytenoid cartilages (vocal cords can approximate in the midline and close the rima glottidis)
narrowest part of larynx
located within thyroid cartilage

Question 11

describe the intrinsic muscles of the larynx

Answer 11

skeletal muscles
attach between the cartilages of the larynx
supplied by somatic motor - branches of the vagus nerves
contraction bring about specific movements of the vocal cords
intrinsic muscles of larynx adduct the vocal cords during cough relfex

Question 12

summarise the anatomy of the vagus nerves

Answer 12

right and left vagus nerves (CN X)
mixed cranial nerves
connect with CNS at the medulla (oblongata) of the brainstem
base of the skull part of course is the jugular foramen
descend through the neck within the carotid sheath - one function important to coughing is to supply somatic sensory and somatic motor axons to the larynx (sensory to the mucosa lining the larynx, motor to the intrinsic muscles of the larynx)
in the chest they descend posterior to the lung root - supplies parasympathetic axons to the chest organs (including the lungs via the pulmonary plexus)
pass through the diaphragm on the oesophagus
on the surface of the stomach they finally divide into many parasympathetic branches for the foregut and midgut organs

Question 13

define the anterolateral abdominal wall

Answer 13

muscles (left and right);
rectus abdominis

external oblique - aponeurosis (flattened tendon) of the right external oblique blends with the aponeurosis of the left external oblique at the midline linea alba.
linea semilnaris - where muscle fibres and aponeurosis begins
attachment superiorly - the superficial aspects of the lower ribs
attachment inferiorly - anterior part of the iliac rest and pubic tubercle
fibre direction the same as external intercostal muscle (anterior, inferior)

internal oblique;
aponeurosis (flattened tendon) of the right external oblique blends with the aponeurosis of the left external oblique at the midline linea alba.
deep to external oblique
attachment superiorly - inferior border of lower ribs
attachment inferiorly - the iliac crest and thoracolumbar fascia of lower back
fibre direction the same as internal costal muscle (posterior, inferior)

transversus abdominus
aponeurosis (flattened tendon) of the right external oblique blends with the aponeurosis of the left external oblique at the midline linea alba.
deep to internal oblique
attachment superiorly - deep aspects of the lower ribs
attachment inferiorly - the iliac crest and thoracolumbar fascia of lower back
fibre direction points (anterior)

nerve supply - serratus anterior

Question 14

describe the rectus abdominis and rectus sheath

Answer 14

rectus sheath - contructed from aponeuroses of other 3 muscles
refer to PP

Question 15

describe the functions of the anterolateral abdominal wall

Answer 15

tonic (continuous low level) contractions maintain posture
tonic (continuous low level) contractions support the vertebral column (mechanical back pain can be improved by abdominal muscle exercises depending on aetiology)
contractions produce movements of the vertebral column (spine) - flexion, lateral flexion, rotation
guarding contractions protect the abdominal viscera
contractions increase intra-abdominal pressure to assist - defecation, micturition, labour
contractions aid forced expiration

Question 16

describe the functions of the anterolateral abdominal wall

Answer 16

tonic (continuous low level) contractions maintain posture
tonic (continuous low level) contractions support the vertebral column (mechanical back pain can be improved by abdominal muscle exercises depending on aetiology)
contractions produce movements of the vertebral column (spine) - flexion, lateral flexion, rotation
guarding contractions protect the abdominal viscera
contractions increase intra-abdominal pressure to assist - defecation, micturition, labour
contractions aid forced expiration

Question 17

describe the pulmonary consequences of chronic cough

Answer 17

breach in the visceral pleura permits alveolar air to enter the pleural cavity

dynamic airway compression in asthma;
expiration difficult
build up of air trapped in alveoli can lead to rupture of lung and visceral pleura

Question 18

describe the pulmonary consequences of a pneumothorax

Answer 18

small amount of air entering pleura cavity;
penetrating injury to parital pleura
rupture of the visceral pleura the vacuum is lost, the elastic lung tissue recoils towards the lung root (<2cm gap between lung and parietal pleura)

large amount of air entering pleura cavity;
penetrating injury to parietal pleura
rupture of the visceral pleura the vacuum is lost, the lung tissue recoils towards the lung root (>2cm gap between lung and parietal pleura)

Question 19

describe diagnosing a pneumothorax

Answer 19

history
examination - reduced ipsilateral chest expansion and breath sounds, hyper-resonance on percussion
investigation (CXR) - absent lung markings peripherally, lung edge visible

Question 20

describe tension pneumothorax

Answer 20

torn pleura can create one way valve that permits air to enter the pleural cavity on each inspiration but prevents air escaping again on expiration
with each inspiration more air enters the pleural cavity
the pneumothorax expands and the lung collapses towards its root
the build up of air in the pleural cavity applies tension (pressure) to the mediastinal structures and cause them to shift
(can be bilateral)

Question 21

describe consequences of mediastinal shift

Answer 21

tracheal deviation, away from the side of a unilateral tension pneumothorax, palpable in jugular notch
SVC compression reduces venous return to the heart leading to hypotension

Question 22

describe the management of large pneumothorax

Answer 22

needle aspiration (thoracentesis)
chest drain via 4th or 5th intercostal space in the midaxillary line

emergency management - large gauge cannula inserted into pleural cavity via 2nd or 3rd intercostal space in the midclavicular line on the side of the tension pneumothorax

Question 23

summarise the anatomy of the steps involved in stimulating and generating a cough

Answer 23

1. stimulation of sensory receptors in mucosa of;
   oropharynx
   laryngopharynx
   larynx
   respiratory tree (trachea to bronchioles)
2. CNS responds by rapidly coordinating;
   deep inspiration using the diaphragm (phrenic nerves), intercostal muscles (internal nerves) and accessory muscles of inspiration
   adduction of vocal cords to close rima glottidis (vagus nerve)
   contraction of the anterolateral abdominal wall muscles (intercostal nerves) to build up intra-abdominal pressure which pushes the diaphragm superiorly and builds up pressure in the chest/respiratory tree inferior to the adducted vocal cords
   the vocal cords suddenly abduct to open rima glottidis (vagus nerve)
   the soft palate tenses (CN V) and elevates (vagus nerve) to close off the entrance into the nasopharynx and direct the stream of air through the oral cavity as a cough (rather than through the nasal cavity as a sneeze)