Week 9: Regional Anatomy: The Thoracic Cavity Flashcards
What is the thoracic region?
- The region between the root of the neck (thoracic inlet) and the abdomen
- The superficial structures of the thorax are referred to as the thoracic wall
- Thoracic wall involved in movement, pulmonary ventilation and protection of the thoracic cavity
Ventilation breathing: Movement of the thoracic region
What is the thoracic region composed of?
- 12x thoracic ribs
- 12x thoracic vertebrae
- Sternum
Muscles and cartilage
Where is the thoracic cavity? What are its sections?
- The thoracic cavity is located deep in the thoracic wall, inferior to the root of the neck and superior to the diaphragm
Contains compartments:- The pleural (pulmonary) cavities x2
- The mediastinum: Pericardial cavity (located within mediastinum)
Contains organs and tissues that function within various body systems
What body systems are involved?
Cardiovascular:
- The heart is the pump for transportation of essential gases, nutrients and hormones
- Maintenance of homeostasis
Respiratory system:
- Pulmonary ventilation and respiration
Nervous system:
- Maintains homeostatic balance, senses and response to the environment and instructs the body for survival
Skeletal:
- Protection of vital organs
Digestive:
Esophagus passes through
What is the Mediastinum?
- The central portion of the thoracic cavity between the lungs
- Extends from the sternum/breastbone anteriorly to the body of the thoracic vertebra posteriorly and from the thoracic inlet superiorly to the diaphragm inferiorly
- Can be subdivided into superior and inferior sections, with the inferior portion being further subdivided into anterior, middle and posterior sections
- This is as the heart is located in the middle portion
- Contains the heart within the pericardial cavity of the middle mediastinum, thymus, esophagus, trachea and major blood vessels
- Surrounded by loose connective tissue to enable movement, volume and pressure changes e.g. during pulmonary ventilation
What are the pleural cavities?
- Left and right cavities that sit within the pleura, contain the left and right lung
- The pleura is continuous, double layered serous membrane lining the lungs and thoracic wall
- Visceral pleura (inner): Attached to the lungs
- Pleural cavity containing pleural fluid
- Parietal pleura (outer): Attached to the thoracic wall, diaphragm and mediastinum
- Facilitates ventilation, creates surface tension to keep alveoli open
What is the pericardial cavity?
- Located in the middle mediastinum
- Specifically between the epicardium and the parietal layers of the serous pericardium
- Contains lubricating fluid called pericardial fluid
Reduces friction between layer as the heart beats - Slightly left of the midline within the mediastinum (specifically within the pericardial cavity)
Apex rests on the diaphragm
Morphology of the heart?
- The human heart contains four chambers: Left and right atria, left and right ventricles
- The human heart contains valves to control the flow of blood
- Tricuspid/right atrioventricular valve
- Pulmonary (semilunar) valve
- Mitral/bicuspid/left atrioventricular valve
Aortic (semilunar valve) valve
Major blood vessels of the heart?
- Aorta
- Left and right pulmonary veins
- Superior and inferior vena cava
- Left and right pulmonary arteries (pulmonary trunk)
- Arteries take blood away from the heart, veins take it to the heart
- We don’t say that arteries only have specific deoxygenated/oxygenated functions as some arteries have opposing functions
- Systole: Heart squeezes, exits aorta to the body
Diastole: blood relaxes and those that weren’t squeezed enters the coronary arteries
Blood supply of the heart: Coronary circulation
- Anterior interventricular branch supplies oxygenated blood to majority of the cardiac muscle on the left-hand-side
- Posterior interventricular
- Left and right marginal
- Circumflex
- Blood enters coronary arteries during ventricular relaxation/diastole (where blood is caught in semilunar valve of the aorta)
- Cardiac veins drain deoxygenated blood back into the right atrium
- Left and right has a marginal artery and supply respective sides
Left: Circumflex artery which usually swings around the back, however individual variation differs person to person
Structure of the heart wall:
Endocardium
- Endothelium and connective tissue that lines heart chambers and valves
Myocardium
- Cardiac muscle that forms the bulk of the heart wall
Epicardium
- A visceral layer of serous pericardium
Pericardial cavity
- Fluid-filled to allow friction-free movement
Pericardium
- Parietal layer of serous pericardium
- Superficial layer of fibrous pericardium
Protects and anchors the heart (fused to diaphragm)
The lungs:
- Located within the thoracic cavity
- Superior portion of lung (apex) sits slightly superior to the clavicles
- Inferior portion (base) lies on the diaphragm
- Left lung is slightly smaller than the right and contains the cardiac notch (space for the heart)
- Lobes of the lung are divided into segments: Each segment divides into lobules (each containing many alveolar sacs)
- Alveoli give the lung its spongey appearance
- Gas exchange at the alveolar level
Ventilation:
- The movement of air between the environment and the lungs through inspiration and expiration (breathing)
- Inspiration: Drawing air into the lungs
- Expiration: releasing air from the lungs
- Follows Boyles law: Pressure is inversely proportional to volume
- If volume increases, pressure decreases
- If volume decreases, pressure increases
Ventilation: Supporting structures
Respiratory musculature
- Regulate inspiration and expiration
- Expand and contract the thoracic cavity
Diaphragm:
- Dome shaped muscle
- Lines the base of the lungs
- Contracts (pulls downward) during inhalation
- Relaxes (recoils upwards) during exhalation
Intercostal muscles:
- Located between ribs
- External intercostals: Quiet forced exhalation
Internal intercostals: Forced expiration
Inspiration:
- Drawing air into the lungs
- Diaphragm contracts (moving downward) and external intercostals contract
- Chest cavity expands, increases volume
- Congruent with Boyle’s law, when the volume in the chest cavity increases, the pressure decreases
- Alveolar pressure becomes lower than atmospheric pressure
Air flows into the lungs (follows pressure gradient)
Exhalation:
- Releasing air from the lungs
- Diaphragm relaxes (moving upwards) and external intercostals relax
- Chest cavity recoils, decreases in volume
- Congruent with Boyle’s law, when the volume in the chest cavity decreases, the pressure increases
- Alveolar pressure becomes higher than atmospheric pressure
Air flows out of the lungs (follows pressure gradient)
Sympathetic innervation of the thoracic cavity?
- Sympathetic control of thoracic viscera occurs via the sympathetic trunk
Fight or flighty physiological responses occur: Increases heart rate, bronchodilation, vasodilation of coronary arteries
Parasympathetic innervation of the thoracic cavity?
- Parasympathetic control of the thoracic viscera occurs via cranial nerve X (vagus nerve)
- Rest and digest physiological responses occur
- Decreased heart rate
- Bronchocondtriction
Vasoconstriction of coronary arteries
Autonomic innervation of the heart: The cardiac plexus:
- The cardiac plexus formed by both sympathetic and parasympathetic neurons enroute to the heart as well as visceral sensory (afferent) neurons relaying information from the heart
- The neurons of the plexus extend along the coronary vessels and to the components of the conducting system of the heart e.g. the sinoatrial node
- Activation of sympathetic innervation: Increased heart rate, increases conduction, increases force of contraction, increases blood flow through coronary arteries
Activation of parasympathetic innervation: Decreases heart rate, reduces force of contraction, constricts coronary arteries
The autonomic innervation of the lungs: The pulmonary plexus
- The pulmonary plexus is formed from extensions of the cardiac plexus that travel alongside the pulmonary arteries to the lungs (sympathetic division) and by branches of the vagus nerve (parasympathetic division)
- Activation of sympathetic innervation: Increases rate of breathing, causes bronchodilation, vasoconstriction of pulmonary blood vessels (increases BP so that, in conjunction with bronchodilation, perfusion of oxygen into blood increases)
Activation of parasympathetic innervation: slows breathing rate, causes bronchoconstriction, vasodilation of pulmonary blood vessels
- Activation of sympathetic innervation: Increases rate of breathing, causes bronchodilation, vasoconstriction of pulmonary blood vessels (increases BP so that, in conjunction with bronchodilation, perfusion of oxygen into blood increases)
What types of ribs are the 12 ribs?
- 1-7 pairs are true ribs (based on attachments to the sternum interiorly), true ribs attach directly into the sternum via their costa cartilage
- 8-10 pairs are false ribs as they attach to the sternum via the 7th costal cartilage
- 11-12 ribs are floating ribs as they do not attach interiorly to the sternum
- Typical ribs: generally from 3-9th ribs have the following components: head, Neck, tubercle, body
Atypical ribs: 1-2, 10-12: are dissimilar, costal cartilages prolong the ribs anteriorly and contribute to the elasticity of the thoracic coil, providing a flexibly attachment. Intercostal spaces separate the ribs and their costal cartilages from one another
Thoracic cavity description?
Thoracic cavity: perfectly designed to carry out functions. Dome shape coupled with light weight gives it a strong rigid ability to perform multiple functions e.g. protection of key thoracic and abdominal organs from external forces, resists the negative internal pressures generated by the elastic recall of the lungs during inhalation/exhalation, provide attachment for and support of upper limbs and provide anchorage attachment form many core muscles
Sternum: Description
- Sternum: flat elongated bone, forming the middle of the anterior part of the thorax, directly in the center of the thorax e.g. protects the mediastinal viscera and heart
- Sternum has: Manubrium, body and xiphoid process, joined by cartilaginous joints which ossify later in life in middle age
What do the separate parts of the sternum do?
- Manubrium: Widest and thickest part
- At the superior boarder is a very easily palpated concave center= Jugular/suprasternal notch. On either side are two smaller clavicular notches. Together these form the sternoclavicular joints, where the clavicle connects to the sternum
The manubrium articulates with the body of the sternum at an angle. This angle is the sternal angle. IMPORTANT landmark as lateral to this the second rib attaches and this provides a way of us being able to count ribs - Body of the sternum: Varying widths due to costal cartilage notches
Xiphoid process: Smallest, variable part of the sternum
- At the superior boarder is a very easily palpated concave center= Jugular/suprasternal notch. On either side are two smaller clavicular notches. Together these form the sternoclavicular joints, where the clavicle connects to the sternum
Thoracic vertebrae?
- Form posterior vertical support of the ribs
- Typical features: Independent, have bodies, have vertebral arches and 7 processes for muscular and articular connections
Characteristic features of thoracic vertebrae: Bilateral costal facets on vertebral bodies, costal facets on their transverse processes, long inferiorly slanting spinous processes.
- Typical features: Independent, have bodies, have vertebral arches and 7 processes for muscular and articular connections
Muscles of the thoracic wall?
- Axioappendicular muscles are attached to and/or cover the thoracic cage and extend to bones of the upper limb
- Anterior lateral abdominal wall, back and neck
- These muscles act primarily on the upper limbs but also act as accessory muscles of inspiration to help elevate the ribs and expand the thoracic cavity during deep inspiration
These muscles include: The scalene muscles, pectoralis minor and major, serratus anterior
What are:
Scalene muscles
Pectoralis major
Pectoralis Minor
The anterior part of the serratus anterior
- Scalene muscles: originate from transverse processes of the cervical vertebrae and insert on the first and second ribs
- Pectoralis major: Originates on the anterior surface of the medial half of the clavicle, anterior surface of the sternum and costal cartilages of ribs 1-6 and then they attach onto the lateral lip of the intertubercle sulcus of the humerus
- Pectoralis minor: Originates 3-5 ribs and its costal cartilage and attaches to the medial border and superior surface of the coracoid process of the scapula
The anterior part of the serratus anterior: Originates on the external surfaces of the lateral part of the 1-8 ribs, these are involved in the expansion of the thoracic cavity
True muscles of the thoracic wall?
- Serratus posterior, levatores costarum, intercostalis, sub-costals and tranverses thorasis
- These move the ribs through elevation and depression during forced respiration and function primarily to support the intercostal spaces, resisting negative and positive intrathoracic pressures
The diaphragm is the main muscle of inspiration: Closes the thoracic outlet, the lower portion of the ribcage and splits the thoracic viscera from the abdominal viscera
- These move the ribs through elevation and depression during forced respiration and function primarily to support the intercostal spaces, resisting negative and positive intrathoracic pressures
Diaphragm?
- 3 main openings which permit passage of some structures
- Anterior opening: Foramen for the inferior vena cava
- Behind is an opening for the esophagus
- Posteriorly is for the aorta: Aortic foramen/aortic hiatus
Mediastinum?
- Central portion of the thoracic cavity between the lungs
- Extends from sternum to vertebral column, then first rib to diaphragm
- Extends from superior thoracic aperture to the diaphragm inferiorly from the sternum and costal cartilages anterior to bodies of vertebra posteriorly
- Highly mobile region of the human body: organ and structures in mediastinum are hollow and filled with liquid and air joined only by connective tissue
- All the major organs in mediastinum are surrounded by blood and lymphatic vessels (lymph nodes, nerves and fat)
- Anatomical descriptions describe the level of the viscera if the person was in a supine position
Abdominal viscera spreads horizontally and pushes the mediastinal structures superiorly. When a person is standing or sitting, the levels of viscera are different as the soft structures of the mediastinum e.g. pericardium sage under the influence of gravity
Contents of the mediastinum?
- Heart
- Thymus
- Esophagus
- Trachea
- Several large blood vessels
These are surrounded by loose connective tissue to enable movement, pressure changes that occur in mediastinal e.g. as a diaphragm moves, the volume and pressure changes to enable air to flow into and out of the lungs, the heart contracts to ensure blood is pumped efficiently around the body, arteries pulse with blood pressure, passage of food and liquid passes through the esophagus as it travels to the stomach
What are the divisions of the mediastinum?
- Mediastinum: Can be divided into superior and inferior. Superior mediastinum extends inferiorly from the superior thoracic aperture to the horizonal plane. This plane includes the sternal angle anteriorly and passes through the junction of the T4 and T5 vertebrae posteriorly. Referred to as the transverse thoracic plane
Inferior mediastinum: Located between the transverse thoracic plane and diaphragm, this can be further subdivided by the pericardium into anterior, middle and posterior sections. The pericardium and its contents (heart, roots of great vessels) make up the middle mediastinum. Some structures such as esophagus pass vertical through the mediastinum and set to light in more than one mediastinal compartment
What is the pulmonary trunk and arteries and ascending aorta?
- Pulmonary trunk contained in the mediastinum: Branches into the left and right pulmonary arteries. Both of which travel to respective left and right lungs
- Pulmonary arteries are the only ones that carry deoxygenated blood
The ascending aorta is approx. 2.5 cm in diameter and starts at the aortic Orpheus
- Pulmonary arteries are the only ones that carry deoxygenated blood
What are the coronary arteries? What is the aortic arch? What is the brachicephalic trunk?
- The coronary arteries branch from the ascending aorta (is identified as intrapericardial and a structure of the middle mediastinum which located in the inferior mediastinum)
- Aortic arch is recognizable structures in the heart: Continuation of the ascending aorta and archers superiorly, posteriorly and to the left for changing direction and heading inferiorly. The arch ascends anteriorly to the right pulmonary artery and the bifurcation of the trachea. The arch ends by becoming the thoracic/descending aorta
At the top of the heart is the brachiocephalic trunk: branch of the aortic arch,
- Aortic arch is recognizable structures in the heart: Continuation of the ascending aorta and archers superiorly, posteriorly and to the left for changing direction and heading inferiorly. The arch ascends anteriorly to the right pulmonary artery and the bifurcation of the trachea. The arch ends by becoming the thoracic/descending aorta
What does brachiocephalic mean?
brachio/bracial= upper limbs
Cephalic= head
What does the brachiocephalic trunk branch into/do?
- Brachiocephalic trunk heads away from the aortic arch, it divides into two arteries: One supplies upper limb, one supplies the head and the neck
- The second branch of the aortic arch= left common carotid artery
- The third/most posterior: left subclavian artery
Superior vena cava: Responsible for returning from all body structures superior to the diaphragm with the exception of lings and heart. Lies to right side of the superior mediastinum, the right and left brachiocephalic veins unite to form the superior vena cava
Nerves of the superior mediastinum?
- Vagus nerve: Two nerves, right and left
- Phrenic nerve: supplies diaphragm with motor and sensory fibers.
Trachea and esophagus - Trachea ascends anteriorly to the esophagus and enters the superior mediastinum to the right of the medial plane.
Esophagus: Enter superior mediastinum between trachea and vertebral column and passes thorough the esophageal hiatus into the diaphragm
- Phrenic nerve: supplies diaphragm with motor and sensory fibers.
What is the pericardium?
- Double walled sac around the heart
- Middle mediastinum
Protects heart and confining position to the mediastinum by allowing it to move in a coordinated manner
- Middle mediastinum
What are the two subdivisions of the pericardium?
- Fibrous pericardium: Protects. Anchors heart, prevents overfilling, dense connective tissue. Fused to central tendon of diagram, when it moves it facilitates movement of blood by the heart. Prevents heart form over stretching and protecting and anchorage
Serous pericardium: Deeper to fibrous, composed of thin membrane which forms a double layer around heart. Outer parietal layer which is fused to the fibrous pericardium. Inner visceral layer that covers the heart Epicardium/ layer of heart wall
What is the pericardial cavity?
Pericardial fluid prevents friction between layers as the heart beats.
Somatic innervation to thorax?
Phrenic and intercostal nerves?
Somatic innervation to thorax:
- Phrenic nerve: Arises in the neck from the ventral rami of C3,4, 5. The only motor innervation to the muscles of the diaphragm. If the nerve is disrupted or damages life is unsustainable. Provides motor innervation to the diaphragm, provides sensory innervation to the pericardium.
Intercostal nerves: Motor innervation to the intercostal muscles, sensory innervation to the pleura and thoracic wall. Represent the main motor innervation to the intercostal muscles. Provide sensory innervation to the pleural and thoracic wall
Sympathetic and parasympathetic innervation of the thorax?
Sympathetic innervation to thorax:
- Fight/flight
- Controls thoracic viscera via the sympathetic trunk/sympathetic chain
- Enables pulmonary arteries to dilate and increases blood flow to the heart tissue
- Increases heart rate and is responsible for bronchodilation
Parasympathetic innervation to the thorax:
- Thoracic viscera by the 10th cranial/vagus nerve
- Supply to thoracic and abdominal viscera
- Enables coronary arteries to constrict and reduce the blood flow to heart tissue
Decreases heart rate, responsible for bronchoconstriction
Cardiac plexus?
- Heart is supplied by autonomic nervous system, the cardiac plexus
- Formed from sympathetic and parasympathetic fibers enroute to the heart
Afferent fibers containing reflexing and nociceptive fibers from the heart. Essentially fibers extend from the plexus along to the coronary vessels and to the components of the conduction system in particular the sinoatrial node
- Formed from sympathetic and parasympathetic fibers enroute to the heart
Sympathetic innervation of the heart?
- Sympathetic supply from the heart comes form presynaptic fibers who cell bodies are located in the intermedia lateral cell columns of the superior 5/6 thoracic segments of the spinal cord
- From post-synaptic sympathetic fibers with cell bodies in the cervical and superior thoracic paravertebral ganglia of the sympathetic trunk
- Post synaptic fibers transverse cardiopulmonary nerves and the cardiac plexus ending in the SA node and AV nodes. In relation to the terminations of the parasympathetic fibers on the coronary arteries.
- Sympathetic stimulation will cause an increased heart rate, increased conduction, increased force of conduction, increased blood flow to the coronary vessels which supports increased activity
- Adrenergic stimulation of the SA node and conducting tissues increases the rate of depolarization of the pacemaker cells while increasing the AV conduction. Direct adrenergic stimulation from the sympathetic nerve fibers and suprarenal hormone stimulation increases atrial and ventricular contraction
Parasympathetic innervation of the heart?
- Parasympathetic supply is from presynaptic fibers of the vagus nerves. Post synaptic parasympathetic bodies are in the atrial wall and intraarterial septum with SA and AV nodes and along the coronary arteries
- Parasympathetic stimulation slows heart rate, reduces the force of contraction and constricts the coronary arteries saving energy between periods of increased demand
Post synaptic parasympathetic fibers will release acetylcholine which bines wis muscarinic receptors to slow rates of depolarization of pace maker cells and atrioventricular conduction and decrease atrial contractability
- Parasympathetic stimulation slows heart rate, reduces the force of contraction and constricts the coronary arteries saving energy between periods of increased demand
What is cardiac referred pain?
- Cardiac referred pain is the phenomenon where stimuli originating in the heart are perceived by a person as pain arriving from the superficial part of the body e.g. skin on the upper left limb e.g. chest/neck
- General somatic afferent fibers from the left arm/neck/chest and general visceral afferent fibers from the heart can verge in the same area of the spinal cord
The brain will then prioritize the input from the general somatic afferent fibers as they are more common input to the brain. The brain will then think the pain is from the chest, left arm and neck
- General somatic afferent fibers from the left arm/neck/chest and general visceral afferent fibers from the heart can verge in the same area of the spinal cord
What happens during cardiac referred pain?
- In response to a schema, which is decreased blood flow and accumulation of metabolic products there can be the stimulation of pain endings in the myocardium. Afferent pain fibers run from the heart centrally into the middle and inferior cervical branches and especially those in the of thoracic cardiac branches o the sympathetic trunk
These axons of the primary sensory neurons also enter spinal cord segments T1-T4/5 and is evident of the left side of the body
Mechanism of breathing?
- Air is 760 mm mercury
- At rest intrapulmonary is 760 mm mercury
- Gases always want to take the path of least resistance: from high to low pressure
- Inspiration/exhalation
- Inspiration: Increase volume, lowers pressure, intrapulmonary pressure has dropped to 759, active process
Expiration: Decrease in volume, increase in pressure to 761 mm mercury, air is moved out to atmosphere, passive process
Clinical implications of a misshaped thorax?
- Thorax has a convex shaped curve posteriorly referred to as kyphosis
- Poor posture as well as medical conditions or events such as Scheuermann’s disease, osteoporosis or fractures may lead to an increase in the kyphotic curve
- Scoliosis refers to the curvature of the spine in the coronal plane
The spine has a curve to the left or right
Blood flow through the heart?
- Deoxygenated blood enters right atrium through superior and inferior vena cava
- Blood enters right ventricle through the tricuspid valve
- Blood exits right ventricle through pulmonary valve and enters pulmonary artery
- Left and right pulmonary arteries send blood to lungs where gas exchange occurs
- Oxygenated blood returns to heart via the pulmonary vein: Enters left atrium
- Blood enters left ventricle through mitral valve
- Blood exits left ventricle through aortic semilunar valve to enter aorta
- CoAorta distributes blood to body
Coronary arteries:
- Heart contracts to feed body but itself needs oxygen, done through arteries (own dedicated blood supply)
- Left and right that come out the trunk of the aorta
- When left ventricle contracts and pushes blood up the aorta, when it relaxes (diastole), the blood wants to fall back down but is cause by aortic semilunar valves
- Blood drains our via coronary arteries
Fed under diastole
Left coronary artery:
- Continues and major branch at the front, descends down, goes down the interventricular septum (separates left and right ventricles)
- Left anterior descending coronary artery (LAD)
- Going down coronary artery, it goes to the apex and moves behind the heart and feeds the majority of the intraventricular septum and left atrium/ventricles/left hand side things on the heart
- Circumflex artery goes around the back and feeds some musculature behind the heart. A branch of this is called the left marginal artery and goes down the margin of the left hand side of the heart and feeds the musculature of the left ventricle
- Major arteries of the left: LAD, circumflex, left marginal
LAD is the most important: Heart attack = musculature will die off and lead to myocardial infarction
Right coronary artery:
- Right coronary flips behind the heart
- Branch: Right marginal artery (right margin), feeds right musculature
- Posterior descending coronary artery: May join with left descending artery: Anastomosis (when blood vessels joining together)
- Common in people who have coronary artery diseases: Increase likelihood the heart is fed so joining them does this (prevents myocardial infarction)
Major arteries on the right: Right marginal, posterior descending, anastomosis at the back
What regions of the spinal cord do parasympathetic nerves arise from?
What region of the spinal cord do sympathetic nerves arise from?
- Craniosacral
- Thoracolumbar
Where is the Thymus?
In the thoracic region
Boarders of the thoracic region?
- Superior boarder: Thoracic inlet
- Inferior boarder: Diaphragm
- Anterior region of the thoracic vertebrae
What is the mitral valve also known as?
Bicuspid valve
Where does the sympathetic/Parasympathetic thoracic nerve start:
- Where does the sympathetic thoracic nerve start: sympathetic trunk T1-T12
- Parasympathetic/pre-ganglionic: sacrum or vagus nerve
What are the names of the two major nerve plexuses that supply the visceral organs of the thoracic cavity:
ty: Cardiac and Pulmonary, autonomic plexuses, not somatic (voluntary)
What landmark represents the most superior point of the thoracic region?
The thoracic inlet
Which of the following options correctly states (A) The serous pleural membrane layer, and (B) The surface it lines?
Visceral pleura, lungs
Which blood vessel carries deoxygenated blood from the heart to the lungs?
Pulmonary Arteries
Which of the following options correctly matches the (A) Ventilation phase, and (B) Muscular action
Expiration, diaphragm relaxes
