Session 1 to 5 of cardiorespiratory anatomy Flashcards
(101 cards)
1
Q
How many percent of blood does the ductus venosus shunt directly from the umbilical veins to the inferior vena cava?
A
about 30%
2
Q
What ribs do the body of the sternum articulate with?
A
Ribs 2-7. Rib 7 articulates with the superior end of the xiphisternum.
3
Q
Which ribs are true ribs, false ribs and floating ribs? Why are they called these terms?
A
- Ribs 1-7 are true ribs as they articulate directly with the sternum (sternocostal joint)
- Ribs 8-12 are false ribs as they do not articulate directly with the sternum, (Ribs 8-10) join the 7th costal cartilage
- Ribs 11 and 12 are considered floating because they are short and do not articulate with the sternum. They only articulate with the vertebrae at the costovertebral joints
4
Q
The costal cartilages of which ribs form the costal margin?
A
The costal cartilages of ribs 7-10 form the costal margin
5
Q
What are typical and atypical ribs and Which are typical and atypical ribs?
A
Typical ribs - Ribs that look similar and share common anatomical features.
Atypical ribs - Look different to typical ribs and lack some of the features of typical ribs.
Ribs 3-9 are typical ribs as they have a head, neck and tubercle and body (shaft)
Ribs 1, 2, 10, 11, 12 are atypical for various reasons, e.g. they are much shorter than typical ribs.
6
Q
In the vertebral column, what are the 5 vertebral sections and how many parts do they have?
A
Cervical - 7 vertebrae (C1 - C7)
Thoracic - 12 vertebrae (T1-T12)
Lumbar - 5 vertebrae (L1-L5)
Sacral - 5 vertebrae (S1- S5)
Coccygeal - 4 vertebrae (Co1-Co4)
7
Q
What forms the boundaries of the superior thoracic aperture? (bones)
A
The manubrium, first rib and the first thoracic vertebrae
8
Q
What do the heads and the tubercle of the ribs articulate with?
A
The head articulates with the vertebral body and the tubercle of the rib articulates with the transverse process of the vertebra.
9
Q
What rib lies at the level of the sternal angle?
A
The second rib
10
Q
What spinal nerves innervate the skin of the thoracic wall? What do the somatic sensory fibres do? What do the somatic motor fibres of the thoracic wall do?
A
- The skin of the thoracic wall is innervated by T1-T12 spinal nerves
- Sensation from the skin reaches our conscious perception via somatic sensory fibres in the spinal nerves.
- Somatic motor fibres innervate the skeletal muscles of the thoracic wall and controls voluntary movement.
11
Q
What is a dermatome?
A
An area of skin innervated by a single spinal nerve. Each pair of thoracic spinal nerves supplies a ‘strip’ around the corresponding body part (thoracic spinal nerves supply strips around the chest wall). (picture in google docs)
12
Q
What are the 5 components in the breast?
A
- Fat –> Variable amounts just under the skin
- Lobules of glandular tissue
- Ducts which converge on the nipple. (areola is the region of pigmented skin surrounding the nipple)
- Connective tissue and ligaments
- Blood vessels and lymphatics
13
Q
What arteries supply the breast with oxygen?
A
The internal thoracic artery, axillary artery and anterior intercostal arteries
14
Q
What are the 5 lymph nodes in the axilla? Which part do they drain?
A
Central- Breast
Pectoral- Upper limb
Humeral- Chest wall
Subscapular- Scapular region
Apical- Abdominal wall
15
Q
Where is the apical node located and what is its significance?
A
The apical node is located in the apex of the axilla.
They receive lymph from all other lymph nodes in the axilla. Because they drain most of the lymph from the breast, they are usually involved in the spread of breast cancer.
16
Q
How many layers of intercostal muscles are there and what is their function?
A
- External, internal and innermost intercostal muscles.
They move the ribs and alter the dimensions of the thoracic cavity for inspiration and expiration.
17
Q
What are the 3 main muscles of the anterior thoracic wall and what are they attached to?
A
- Pectoralis major- Most superior muscle of the anterior chest wall. It is attached to the upper humerus, clavicle and ribs 1-6.
- Pectoralis minor- lies deep to the pectoralis major. It is attached to ribs 3-5 and the scapula.
- Serratus anterior- A layer of superficial muscle that lies jagged around the lateral aspect of the thoracic cage. It attaches to ribs 1-8.
18
Q
What is the prime function of the pectoralis major, pectoralis minor and serratus anterior and how do they carry it out?
A
- The prime function of these muscles is to move the upper limb.
- Pectoralis major adducts the humerus while pectoralis minor and the serratus anterior abducts the scapula.
19
Q
What are the accessory muscles of breathing and why is it possible for them to carry out this function? What is this a sign of (if you use accessory muscles for breathing)?
A
Pectoralis major, pectoralis minor and serratus anterior can also function as accessory muscles of breathing as they attach to the ribs and hence can move the ribs. HOWEVER, in patients, use of these muscles is a sign of respiratory distress. (the sternocleidomastoid can also function as an accessory muscle)
20
Q
What are the spaces in between the ribs called and what do they contain?
A
- Intercostal spaces
It contains the - Intercostal muscles (3 layers and associated membranes)
- Intercostal neurovascular bundle (comprising of an intercostal, artery, vein and nerve)
21
Q
The different layers of intercostal muscles have their fibres running in different directions and thus act on the ribs in different ways.
How are the 3 layers of intercostal muscles orientated?
A
- External intercostal muscles have fibres running infero-medially (antero-inferiorly)
- Internal intercostal muscles and innermost intercostal muscles have fibres running perpendicular to the EIM (postero-inferiorly) to that and so away from the midline and inferiorly.
22
Q
Function of the external intercostal muscles
A
When it contracts during inspiration, it pull the ribs superiorly to increase the volume of the thoracic cavity, thus decreasing pressure in the lungs and allowing inflow of air.
23
Q
Function of internal intercostal muscles
A
When it contracts during expiration, it pulls the ribs inferiorly decreasing intrathoracic volume thus increasing pressure in the lungs and air is expelled from the lungs.
24
Q
Where does the endothoracic fascia lie?
A
Deep to the innermost intercostal muscles and superficial to the parietal pleura.
25
Order of layers from the skin to the lungs
Skin, superficial fascia, serratus anterior, external intercostal muscles, internal intercostal muscles, innermost intercostal muscles, endothoracic fascia, parietal pleura, pleural cavity, visceral pleura, lung.
26
Where is the neurovascular bundle?
They lie along the inferior border of the ribs, superior to the intercostal space.
It lies in a shallow costal groove on the deep surface of the rib. (They are located in the plane between the internal and innermost intercostal muscle)
(That is why when you need to pierce the intercostal space you usually cut at the middle or lower part of the intercostal space to avoid damaging the neurovascular bundle)
27
What does the neurovascular bundle supply?
It supplies the intercostal muscles, the overlying skin, and the underlying parietal pleura.
28
Where do the anterior and posterior intercostal arteries branch from?
- Anterior intercostal arteries- branches of the internal thoracic artery (a branch of the subclavian artery)
- Posterior intercostal arteries- branches from the descending aorta (in posterior thorax).
29
Where do the anterior and posterior intercostal veins drain into?
- The anterior intercostal veins drain into the internal thoracic vein.
- The posterior intercostal veins drain into the azygous system of veins (carries blood back to the heart).
30
What does the two layers of pleura cover and what are they called.
What lies in between the 2 layers of pleura?
- They generally cover the lungs and structures passing in and out of the lungs (pulmonary blood vessels and the main bronchi)
- The parietal pleura lines the inside of the thorax
- The visceral pleura adheres and covers the surface of the lungs, (and extends into the fissures)
- A thin pleural cavity lies between both layers of pleura. They contain pleural fluid made by pleural cells to aid mechanics of breathing.
31
Function of pleural fluid
- To create surface tension between the parietal pleural lining, the thoracic cavity and the visceral pleura.
- Surface tension allows the lung and thoracic wall to move together so when thoracic volume changes, lung volume changes as well.
- Pleural fluid also prevents the lungs from collapsing. If there is a puncture in the parietal pleura and air enters the pleural cavity, ventilation may become dysfunctionl.
32
What are the different borders of the parietal pleura?
- Cervical pleura- covers apex of the lungs
- Costal pleura- lies adjacent to the rib
- Mediastinal pleura- lies adjacent to the heart
- Diaphragmatic pleura- lies adjacent to the diaphragm.
33
Where is the costomediastinal and costodiaphragmatic recess?
Costomediastinal recess- Lies at the junction of the costal and mediastinal pleura.
Costodiaphragmatic recess- Where the costal parietal pleura becomes continuous with the diaphragmatic pleura
34
What nerves are the visceral and parietal pleura innervated by?
Visceral- Branches of the vagus nerve (Autonomic sensory fibres)
Parietal- Innervated by intercostal nerves that innervate the overlying layer of skin over the chest wall. SOMATIC sensory fibres carry sensations to our consciousness.
35
What separates the lobes of the lungs? (talk about both lungs)
- Both lungs have oblique fissures. In the left lung, it separates the superior and inferior lobe. In the right lung it separates the superior and middle lobe from the inferior lobe.
- The right lobe has a horizontal fissure as well separating the superior and the middle lobe.
36
What landmarks can you use to explain where the fissures of the lung extend to and from?
Oblique fissure- 4th rib posteriorly, 5th rib deeply and 6th rib anteriorly.
Horizontal fissure- at the level of the 4th rib, it intersects with the oblique fissure.
37
What is the hilum of the lung?
The region on the mediastinal surface of the lung where the pulmonary artery, pulmonary vein and the main bronchus enter and exit the lung.
38
Where do the pulmonary veins and main bronchus lie on the hilum of both lungs?
In both right and left lungs, the pulmonary veins are usually situated most anteriorly and inferiorly.
(essentially, the bronchus is located medially on both)
In the right lung, the main bronchus lies anterior to the pulmonary artery while in the left lung, the main bronchus usually lies inferior to the pulmonary artery.
39
What is the branching system of the bronchial tree?
1) Each main bronchus is divided into lobar bronchi- 3 in the right lung, two in the left lung.
2) Each lobar bronchi divide into segmental bronchi- 10 in each lung. (each supplying their own independent segment of the lung)
3) Segmental bronchi continue to divide into terminal bronchioles, respiratory bronchioles and alveolar ducts (where gas exchange occurs).
40
What is a difference between the walls of the trachea and main bronchus from the bronchioles?
The walls of the trachea and bronchi contain smooth muscle AND cartilage while the walls of the bronchioles only contain smooth muscle. (contraction and relaxation of the smooth muscle is controlled autonomically)
41
What do parasympathetic and sympathetic nerves that innervate the lung do when stimulated?
Parasympathetic nerves
- Causes bronchoconstriction of smooth muscles and secretion from glands of the bronchial tree
Sympathetic nerves
- Causes bronchodilation and inhibits secretion from glands of the bronchial tree
bronchial secretions help protect the airway against pathogens and environmental toxins
42
What do visceral afferents (visceral sensory fibres) do?
They accompany sympathetic and parasympathetic fibres and relay sensory information from the lungs and visceral pleura to the CNS. (however these sensations do not usually reach out consciousness unlike the somatic sensory fibres that innervate the parietal pleura)
43
What is separated by the costodiaphragmatic recess?
The inferior border of the lung and the inferior extent of the parietal pleura.
44
What are the surface landmarks for the inferior border of the lungs and the parietal pleura
Lungs
- 6th anteriorly
- 8th laterally
- 10th posteriorly
Parietal pleura
- 8th anteriorly
- 10th laterally
- 12th posteriorly
45
Features of the diaphragm (at least 3)
- It is a broad, thin, domed sheet of skeletal muscle
- It separates the thoracic and abdominal cavity
- Its superior surface is adjacent to the parietal pleura
- Openings (apertures) in the diaphragm allow for the passage of structures between the thorax and the abdomen (e.g. esophagus, abdominal aorta, inferior vena cava, etc)
- Its function is integral to the mechanics of breathing (ventilation)
- It is attached to the xiphoid process, costal margin and the lumbar vertebrae.
- The central part of the diaphragm is fibrous (central tendon) rather than muscular
- The left and right somatic phrenic nerves arising from C3, C4, C5 spinal nerves innervate the left and right side of the diaphragm.
46
How can the diaphragm be moved in three planes?
- Vertically - due to contraction and relaxation of the diaphragm
- laterally- due to contraction of the intercostal muscles which move the ribs
- Antero-posteriorly- due to movement of the sternum secondary to movement of the ribs
47
What are the muscles involved in inspiration?
- The diaphragm and external intercostal muscles contract. (external intercostal muscles pull ribs superiorly and laterally, ribs pull the sternum superiorly and anteriorly
- Intrathoracic volume increases
- lungs expand with thoracic wall due to surface tension
- pressure in lungs decrease below atmospheric pressure and air is drawn into the lungs.
48
What are the muscles involved in expiration?
- The diaphragm and external intercostal muscles relax
- Internal intercostal muscles contract (all leading to the decrease in intrathoracic volume) --- Internal intercostal muscles pull ribs inferiorly and ribs pull the sternum inferiorly and posteriorly
- Lungs recoil, decreasing volume
- Pressure in the lungs increases above atmospheric pressure and air is expelled from the lungs.
49
What does the pleural fluid in the lung do?
The pleural fluid creates surface tension between the parietal pleura lining the thoracic cavity and the visceral pleura on the surface of the lung.
- This surface tension keeps the lung and thoracic wall together so that when the thoracic cavity changes, the lung volume changes with it.
- This surface tension also prevents the collapsing of the lung away from the thoracic wall.
50
When will ventilation become dysfunctional due to a lack of pleural fluid?
When surface tension is 'broken' due to a penetrating injury of the parietal pleura where air is introduced to the pleural cavity, ventilation becomes dysfunctional
51
Describe the muscles involved in 1) normal breathing 2) vigorous breathing 3) very vigorous/forced breathing
1) Normal breathing- The diaphragm is the main muscle driving inspiration and expiration is passive
2) Vigorous breathing- the internal costal muscles become important. Internal intercostal muscles are used in active expiration
3) Forced breathing- Accessory muscles are used for breathing (pectoralis major, pectoralis minor, serratus anterior, sternocleido mastoid) which contribute to the movement of the ribs and aid ventilation
52
Where is the mediastinum and what does it contain?
- It is the part of the thoracic cavity lying in between the lungs
- It contains all the thoracic viscera apart from the lungs. These include: the heart, pericardium, esophagus and thymus gland, trachea, bronchi, great vessels entering and leaving the heart, veins that drain the chest wall, nerves and lymphatics.
53
What are the borders of the mediastinum? (extensions from superior, inferior, anterior and posterior)
- It extends from the superior thoracic aperture superiorly to the diaphragm inferiorly
- It extends from the sternum anteriorly to the thoracic vertebrae posteriorly
54
Where is the superior and inferior mediastinal separated?
They are separated at the level of the sternal angle anteriorly and at the level of T4-T5 on the thoracic vertebrae posteriorly.
55
What are the main contents of the superior mediastinum?
- The arch of the aorta and its branches
- The superior vena cava and its tributaries (left and right brachiocephalic veins)
- Trachea
- Esophagus
- left and right phrenic nerves
- left and right vagus nerves
- the thoracic duct
- the thymus gland
56
What is the inferior mediastinum divided into?
The anterior mediastinum- lies between the posterior aspect of the sternum and the anterior aspect of the pericardial sac. (thymus gland is located here)
The middle mediastinum- containing the heart inside the pericardial sac. It also contains the pulmonary trunk and ascending aorta.
The posterior mediastinum- it lies between the posterior aspect of the pericardial sac and the vertebrae.
57
How many parts does and aorta have and what do they do?
Ascending aorta- short and gives rise to coronary arteries
Arch of the aorta- curves posteriorly and lies in the superior mediastinum
Descending aorta- Descends through the posterior mediastinum and into the abdomen posterior to the diaphragm.
58
What do aortic bodies in the arch of the aorta do/contain?
Not baroreceptors, what is the other thing they contain?
How is the information transmitted and what is the end result?
The arch of the aorta contains aortic bodies where chemoreceptors are located. These receptors constantly monitor arterial oxygen and carbon dioxide.
Visceral sensory information travels back to the CNS along the path of the vagus nerve and results in reflex responses that regulate ventilation.
They contain both chemoreceptors and baroreceptors
59
What are the 3 major branches of the arch of the aorta in the superior mediastinum? (what do they supply?)
Brachiocephalic trunk- which bifurcates into the right common carotid artery (supplying the right side of the head and neck) and the right subclavian artery (supplying the right upper limb).
Left common carotid artery- suppling the left side of the neck, head and brain
Left subclavian artery- supplies the left upper limb.
60
What is the ligamentum arteriosum?
What is the function of it?
What happens at first breath?
It is the remnant of the ductus arteriosus (a foetal circulatory shunt). It is a fibrous cord-like connection between the pulmonary trunk and the arch of the aorta.
The function of the ductus arteriosus is the divert blood going to the pulmonary trunk to the arch of the aorta. This is because gas exchange in the foetus takes place in the placenta and not the lungs (although some blood still circulates through the lungs for development).
At birth, when the baby starts to use its lungs to breath, the ductus arteriosus closes and blood in the pulmonary trunk enters the lungs.
61
What is the superior vena cava formed by?
- it is formed by the left and right brachiocephalic veins (and drains blood into your right atrium).
- The brachiocephalic veins are each formed by a subclavian vein (drains your neck, head and brain) and an internal jugular vein (drains your upper limb).
62
What does the inferior vena cava do?
Is it shorter or longer than the superior vena cava?
It returns deoxygenated blood from the regions inferior to the diaphragm, to the right atrium.
It is shorter than the vena cava. As soon as it enters the thorax through the diaphragm, it enters the right atrium.
63
Tell me about the trachea (3)
- It conducts air to and from the left and right main bronchi
- It is semi rigid and has C shaped rings of cartilage in its walls.
- It extends from the larynx in the midline of the neck into the superior mediastinum (and is palpable just superior to the suprasternal notch)
- It terminates at the level of the sternal angle by bifurcating into the left and right main bronchi.
64
Tell me about the oesophagus (3)
- A muscular tube that extends from the pharynx in the midline of the neck to the stomach.
- Via peristalsis, it moves swallowed food and fluid down into the stomach.
- It enters the superior mediastinum posterior to the trachea and descends into the posterior mediastinum.
65
Tell me about phrenic nerves (3)
- They are formed by fibres from the C3, C4 and C5 spinal nerves.
- They innervate the diaphragm at the level of T8
- They are somatic nerves which contain both sensory and motor fibres
- They descend through the neck and enter the thorax via the superior thoracic aperture.
- They course over the pericardium of the right atrium and left ventricle
66
Tell me about vagus nerves (3)
- They arise from the brainstem
- They contain somatic sensory, somatic motor and parasympathetic fibres.
- They innervate structures of the head, neck, thorax and abdomen
- They contribute parasympathetic fibres to the heart, lungs and oesophagus
- They descend through the neck alongside the internal jugular vein and the internal carotid artery and enter the thorax via the superior thoracic aperture.
- They each give rise to a recurrent laryngeal nerve which ascends back up into the neck to innervate muscles of the larynx.
- Passes through the diaphragm at T10
67
Tell me about the left and right recurrent laryngeal nerves. (3)
- The left and right vagus nerves gives rise to the left and right recurrent laryngeal nerves.
- The left recurrent laryngeal nerve loops under the arch of the aorta before ascending back up the left side of the neck (alongside the trachea) to the larynx.
- The right recurrent laryngeal nerve loops around the inferior border of the right subclavian artery before ascending back up the right side of the neck to the larynx.
- They both provide motor innervation to all the intrinsic laryngeal muscles except the cricothyroid muscle (which is supplied by the superior laryngeal nerve)
68
Tell me about the thoracic duct (3)
If this is the case, what is the other side of the body drained by?
- Lymph from the lower limbs, pelvis and abdomen flow to the cisterna chyli, a sac like swelling which gives rise to the thoracic duct, which ascends into the thorax.
- As it ascends up the thorax, it collects lymph from the intercostal spaces and lymph nodes.
- It then ascends into the neck collecting lymph from the left upper limb, left side of the head and neck.
- It terminates at the venous system in between the left jugular vein and the left subclavian vein.
- Lymph on the right side of the head, neck and upper limb are drained by lymphatic ducts which terminate at the venous system in between the right subclavian vein and right internal jugular vein.
69
Tell me about the thymus gland (3)
- It is a lymphoid organ that is essential for the development of T cells.
- It lies anteriorly in the superior mediastinum.
- It is important in children but atrophies with age to become fatty.
70
What is the pericardium?
Is it tight or loose?
What are the layers of the pericardium?
The pericardium is a tough, fibrous sac that encloses the heart like a loose-fitting bag. (it is loose to allow the movement of the heart within it)
There are 2 main layers:
- A tough, outer fibrous layer attached superiorly to the great vessels and inferiorly to the central tendon of the diaphragm.
- A thin, inner serous layer that has two parts the parietal layer (lining the inner aspect of the fibrous pericardium), and the visceral layer (covering the surface of the heart) --THEY ARE CONTINUOUS WITH EACH OTHER.
71
What is the narrow space between the two layers of the pericardium and what does it contain? What is its function?
- It is the pericardial cavity which contains pericardial fluid.
- Pericardial fluid lubricates the serous membranes which allows them to slide over each other with movements of the heart.
72
What nerves innervate the fibrous pericardium?
The left and right phrenic nerves give rise to sensory branches which innervate the fibrous pericardium.
73
You are doing well！
Keep it up!
74
Which surface of the heart corresponds to the parts of the heart?
Base/posterior- Left atrium and part of right atrium
Diaphragmatic/inferior- Left ventricle and part of the right ventricle
Sternocostal/anterior- Right ventricle
Left pulmonary surface- left ventricle
Right pulmonary surface- right atrium
75
What is the apex of the heart formed by and where does it lie?
It is formed by the left ventricle and lies at the 5th intercostal space in the midclavicular line where the apex beat is palpable.
76
What are the borders of the heart relative to surface markings (e.g. costal cartilages)
Right border- Lies laterally to the right sternal edge from the right 3rd costal cartilage to the 6th costal cartilage
Left border- Extends from the left 2nd intercostal space to the left 5th intercostal space in the midclavicular line
Superior border- (lies along the line connecting the superior right and left borders). extends from the right 3rd costal cartilage to the 2nd left intercostal space
Inferior border- (lies along the line connecting the inferior right and left border) 6th right costal cartilage to the 5th left intercostal space.
77
What are auricles/auricular appendages of the heart?
They are muscular outpouchings from the walls of the right and left atria (they have a ear like appearance) which increase the holding capacity of the atria when needed.
78
What are sulci of the heart?
They are grooves on the external surface of the heart where the major arteries lie.
79
Generally, what do these arteries supply?
1) Coronary arteries
2) Pulmonary arteries
3) Right marginal artery
4) Posterior interventricular artery
1) Coronary arteries supply blood to the heart muscles
2) Pulmonary arteries carry blood to the lungs
3) Right marginal artery supplies the inferior border of the heart
4) The posterior interventricular artery is a continuation of the right coronary artery on the diaphragmatic surface of the heart. It supplies both ventricles.
80
What are the two main branches of the left coronary artery?
What do they supply?
Name a branch from each of these main branches.
1) The left circumflex artery which runs around the heart and then to the diaphragmatic surface. (it supplies the left atrium, part of the right ventricle and the left ventricle. (the left marginal artery arises from the circumflex and supplies the left ventricle)
2) The left anterior descending which runs in the anterior interventricular sulcus. It supplies both ventricles. (one or two diagonal branches arise from the LAD)
81
Whether the posterior interventricular artery arises from the left or right coronary artery, how does it affect the body? Explain in depth.
- This will determine if an individual has a left or right dominant coronary circulation.
- In those with left dominant coronary circulation, the posterior interventricular artery arises from the circumflex artery. (here, only the left coronary artery supplies the left ventricle) --> 10% of people
- In those with right dominant coronary circulation, the posterior interventricular artery arises from the right coronary artery. (here, both right and left coronary arteries supply the left ventricle) --> 70% of people
- This means that in someone with left-dominant coronary circulation, should there be a blockage of the left main stem, blood flow to the entire left ventricle would be occluded (but in someone with right dominant coronary circulation, they would still have the right coronary artery to supply the left ventricle.
82
What are some features of the right atrium (3)
What are pectinate muscles?
- It receives deoxygenated blood from the SVC and IVC and from the heart via the coronary sinus.
- The interatrial septum separates the right and the left atrium
- The fossa ovalis which is a remnant of the foramen ovale used to shunt blood from the right to left atrium (bypassing the lungs)
- Crista terminalis- A muscular ridge separating the smooth walled posterior part of the atrium and the ridged musclar wall of the anterior part of the atrium.
- (The coronary sinus drains into the right atrium)
- Pectinate muscles are comb shaped parallel columns of muscular ridges which are present on the inner walls of the left and right atria. (and extend to the auricle)
83
Features of the right ventricle (3-4)
Interventricular septum- separates the left and right ventricles.
Trabeculae carneae- muscular ridge on the internal wall
3 Papillary muscles- Modified regions of trabeculae carneae which project into the lumen of the ventricle
Chordae tendineae- fibrous chords connecting the tips of the papillary muscles to the tricuspid valve
Moderator band- Modified region of trabeculae carneae which connects the interventricular septum to one of the papillary muscles.
84
Features of the left ventricle
- Has the thickest wall of all the chambers as it propels blood into the systemic circulation.
- Has trabeculae carneae (muscular columns pulls on chordae tendinae attached to mitral valve to prevent blood from leaking back into the atria)
- 2 papillary muscles
- Chordae tendineae that connects the tips of the papillary muscles to the mitral valve
85
How do atrioventricular valves close? (referring to papillary muscles and chordae tendinae)
- Atrioventricular valves have cusps which passively close when blood pressure in the ventricles is higher than in the atrium.
- Chordae tendinae contract when the ventricles contract, pulling on the cusps and not allowing them to be forced opened.
86
How do semi lunar valves close?
(referring to sinuses)
- Semi lunar valves have 3 semi circle cusps which are flattened onto the vessel wall when blood flows from the ventricles to the aorta/pulmonary artery.
- If blood tries to flow back into the ventricles, the sinuses fill with blood and the valve orifice closes.
87
What is the electrical impulse route of the heart?
- The sinoatrial node generates impulses at a rate of approximately 70 per minute
- Impulses from the SAN causes the atria to contract
- Impulses are conducted to the AVN located at the inferior end of the interatrial septum.
- From the AVN, the electrical impulse travels down the bundle of His (atrioventricular bundle) which divides into the left and right bundle branches.
- The left and right bundle branches give rise to the purkinje fibres that enter the myocardium of the left and right ventricles, and the electrical impulse that has travelled down, stimulates contraction.
88
Where does the posterior mediastinum lie and what does it contain?
- The posterior mediastinum lies between the posterior of the pericardial sac and the vertebrae.
- It contains the: descending aorta, azygous veins, oesophagus, thoracic duct, sympathetic trunk and splanchnic nerves, posterior intercostal vessels and nerves.
89
What does the descending aorta give rise to and at what level does it pass through the diaphragm?
The descending aorta gives rise to
- Posterior intercostal arteries - supplying intercostal space
- Bronchial arteries- supplying the lungs
- Oesophageal branches- supplying the oesophagus
- Pericardial branches- supplying the pericardium
- Phrenic branches supplying the diaphragm.
The aorta pass through the diaphragm at the level of T12
90
What does the azygous vein system comprise of (3)? AND What do they do?
- An azygous vein on the right side of the vertebral bodies (arises in abdomen at level of L1/L2
- A shorter hemiazygous vein on the left side of the vertebral bodies. (At the level of T8, it turns right and combines with the azygous vein.
- Accessory hemiazygous vein- drains into azygous vein at level of T7
The azygous system of veins drains blood from the posterior thoracic wall and returns it to the superior vena cava.
91
What is the blood vessel system of the proximal and distal oesophagus? (arteries and vein)
What is portosystemic anastomose?
- In the posterior mediastinum, the oesophagus is supplied by oesophageal arteries from the descending aorta.
- In the posterior mediastinum, oesophageal veins return venous blood to the azygous system.
- In the abdomen (distal oesophagus), it is supplied by branches from the left gastric artery.
- In the abdomen (distal oesophagus), venous blood is drained through 2 paths. Systemic system of veins (oesophageal veins drain into azygous veins) and portal venous system via the left gastric vein.
- Portosystemic anastomose describes the site of communication between the systemic system of veins and the portal venous system.
92
Tell me about the thoracic duct
- Lymph from the lower limbs, pelvis and abdomen flow to the cisterna chyli, a sac like swelling which gives rise to the thoracic duct and ascends into the thorax.
- In the thorax, it drains lymph from the intercostal spaces and lymph nodes
- As it ascends into the neck, it receives lymph from the left upper limb, left side of the neck and left side of the head.
- It terminates by opening into the venous system in between the left internal jugular vein and the left subclavian vein.
- The right side of the upper limbs, head and neck are drained by lymphatic ducts which drain into the venous system between the right subclavian vein and right internal jugular vein.
93
Where are the sympathetic trunks located and what are some characteristics of them?
Where does the trunk extend from?
- The sympathetic trunks are located on the posterior thoracic wall on either side of the vertebral column, posterior to the parietal pleura.
- They are thin, longitudinal fibre tracts that are regularly interspersed with ganglia
- The trunk extends from the base of the skull to the coccyx.
94
Where are preganglionic sympathetic neurons located (spinal segments) and what is their function?
- They are located in the thoracic and upper lumbar segments T1-L2/L3
- As sympathetic fibres are visceral motor fibres, they leave the spinal cord from its ventral aspect and enter spinal nerves T1-L2/L3 along with somatic motor nerves, whose cell bodies lie in the ventral grey horn.
95
What happens to preganglionic sympathetic fibres when they leave the spinal cord?
What are the possible scenarios when the preganglionic axon enter the sympathetic trunk?
- Once they leave the spinal cord, almost immediately, they will enter the sympathetic trunk via a short connecting branch- the white ramus communicans
- When the preganglionic axons enter the sympathetic trunk, they can either synapse in the ganglion at its level of entry, ascend or descend in the trunk before synapsing in a ganglion, or travel through a ganglion without synapsing?
96
Where the preganglionic axons synpase with the ganglion in the sympathetic trunk, what happens to the postganglionic axons leaving the ganglia.
Sympathetic fibres enter all pairs of spinal nerves. How many pairs of spinal nerves are there?
- Postganglionic axons enter spinal nerves via a communicating branch (grey ramus communicans)
- Postganglionic axons can also form visceral nerves that convey sympathetic fibres to the head and thoracic viscera (cardiopulmonary splanchnic nerves).
- Sympathetic fibres enter all 31 pairs of spinal nerves
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What happens to the preganglionic axon that does not synapse in the sympathetic trunk? What are these nerves categorised into?
- These preganglionic axon leave through an abdominopelvic splanchnic nerve.
- These nerves are categorised into:
- Greater splanchnic nerves (T5-T9)
- Lesser splanchnic nerves (T10-T11)
- Least splanchnic nerves (T12)
- Lumbar splanchnic nerves (L1-L2)
98
Sympathetic fibres from the splanchnic nerves and parasympathetic fibres from the vagus nerve form an autonomic plexus around the thoracic viscera. What are the 3 plexus found in the thorax? What do sympathetic and parasympathetic stimulation result in?
- Cardiac plexus--> Innervates the heart. Sympathetic fibres increase the heart rate and increase the force of contraction. Parasympathetic fibres vice versa
- Pulmonary plexus--> Innervates the bronchi. Sympathetic fibres stimulate the relaxation of the bronchi. Parasympathetic fibres stimulate the constriction of the bronchi.
- Oesophageal plexus--> Overlies the anterior surface of the oesophagus. Sympathetic fibres inhibit peristalsis and parasympathetic fibres stimulate peristalsis (rest and digest)
99
What are sympathetic and parasympathetic nerves also called?
Visceral efferent nerves ,,,as they leave the CNS and travel to the periphery.
100
Where in the spinal cord do the sympathetic fibres innervating the cardiac muscle arise?
The sympathetic fibres that travel to the cardiac plexus and the heart, arise from spinal cord segments T1-T5 via the cardiopulmonary splanchnic nerves.
101
Why do we feel chest pain when the myocardium is ischemic?
- The heart is innervated by visceral sensory nerves which convey sensory information from the heart back to the CNS- which does not reach our conscious perception
- However, because visceral sensory nerves travel back to the CNS alongside sympathetic fibres that innervate the heart, the visceral sensory information enters spinal cord segments T1-T5
- However, somatic sensory information from the skin of the chest wall, neck and arm also return to spinal cord segments T1-T5, so painful visceral sensory information from the heart and somatic sensory information from the chest wall both enter spinal cord segments T1-T5 and thus cardiac pain is referred to the chest wall, left side of neck or left arm.
