Cardiorespiratory System - VOID Flashcards
1
Q
Label the anterior views of the ribs and sternum.
A
2
Q
What are the different joints in the thoracic cage?
A
Costochondral joints: where the ribs articulate with the costal cartilages.
Sternocostal joints: where the costal cartilages of ribs 1-7 articulate with the sternum. These are the ‘true’ ribs. Ribs 8-10 join (and also with rib 7) to form the ‘costal margin’.
Costovertebral joints: where the ribs articulate anteriorly with the thoracic vertebrae.
3
Q
What are typical ribs?
A
Ribs that look similar and share anatomical features ie ribs 3-9. They have a head, neck, tubercle and body (shaft).
Atypical ribs are atypical for various reasons ie ribs 1,2,11 are much shorter than typical ribs.
4
Q
Label the anatomy of the breast.
A
- Intercostal muscle.
2. Pectoral muscles.
3. Lobule. - Nipple.
- Areola.
- Ducts.
- Fat.
8. Skin.
5
Q
Describe the neurovascular supply of the breast.
A
- Internal thoracic artery (which arises from the subclavian artery).
- Axillary artery.
- Intercostal nerves supply somatic nerves and sympathetic fibres. Somatic sensory fibres innervate the skin of the breast. Sympathetic fibres innervate smooth muscle in the blood vessel walls and nipple.
6
Q
Describe the lymphatic drainage of the breast.
A
Most drains to lymph nodes in the axilla, which contains 5 groups of lymph nodes: central, pectoral, numeral, sub scapular and apical.
They drain the breast, upper limb, chest wall, scapular region and the abdominal wall.
The apical nodes (in the apex of the axilla) receive and drain lymph from all other lymph nodes in the axilla.
7
Q
What are the layers of the thoracic wall?
A
*External intercostal is most superficial and fibres lie antero-inferiorly. When they contract they pulls the ribs superiorly, so are most active in inspiration.
In the anterior part of the intercostal space, the muscle becomes membranous and forms the external intercostal membrane.
*Internal intercostal lies deep to the external intercostal. Fibres run perpendicular to the external intercostal, in a posterior-inferior direction. Pulls ribs inferiority so is most active in expiration.
It becomes membranous in the posterior part of the intercostal space and forms the internal intercostal membrane.
*Innermost intercostal lies deep to internal intercostal. Fibres lie in the same direction as those of internal intercostal.
The endothoracic fascia lies deep to the innermost intercostal and superficial to the parietal pleura, which surrounds the lung.
These allow inspiration and expiration.
The intercostal spaces also contain a neurovascular bundle, comprising an intercostal nerve, artery and vein. These supply the intercostal muscles.
8
Q
Describe the pectoralis major.
A
The most superficial muscle of the anterior chest wall. It attaches to the humerus, clavicle and the upper six ribs.
It adducts the humerus.
9
Q
Describe the pectoralis minor.
A
The smaller muscle, lying deep to the pectoralis major. Attaches to the scapula and ribs 3-5.
With the serratus anterior, they protract the scapula.
10
Q
Describe the serratus anterior.
A
The muscle superficial around the lateral aspect of the thoracic cage. Attaches to the scapula and upper eight ribs.
With the pectoralis minor, they protract the scapula.
11
Q
What is the function of the upper limb muscles?
A
The pectoralis major, pectoralis minor and serratus anterior.
They move the upper limb.
They also act as accessory muscles of breathing. They can move if the humerus and scapula are fixed. Use of these while breathing is a sign of respiratory distress.
12
Q
Describe the intercostal neurovascular bundles.
A
Each intercostal space has a neurovascular bundle that supplies it. It lies along the inferior border of the rib superior to the intercostal space, in a shallow costal groove on the deep surface of the rib.
The anterior and posterior intercostal spaces are supplied by the anterior and posterior intercostal arteries, respectively.
The anterior intercostal arteries are branches of the internal thoracic artery (which is a branch of the subclavian artery).
The posterior intercostal arteries are branches from the descending aorta in the posterior thorax.
Anterior intercostal veins drain into the internal thoracic vein.
Posterior intercostal veins drain into the azygos system of veins.
Intercostal nerves are somatic.
They innervate intercostal muscles, skin of chest wall, and parietal pleura. Intercostal nerves also carry sympathetic fibres.
13
Q
What are the pleurae?
A
The two layers of membranes that cover the lungs and the structures passing into and out of the lungs. They are separated by a thin pleural cavity (filled with pleural fluid as produced by pleural cells).
Pleural fluid creates surface tension between the pleura on it’s either sides, keeping the thoracic wall together. This means the lung changes volume when the thoracic cavity does during inspiration.
*The parietal pleura lines the inside of the thorax. It is innervate by somatic sensory fibres in intercostal nerves that innervate the overlying skin to the chest wall. It has 4 parts:
Cervical pleura covers apex of lung.
Costal pleura lies adjacent to ribs.
Mediastinal pleura lies adjacent to heart.
Diaphragmatic pleura lies adjacent to diaphragm.
- Visceral pleura cover surface of lungs. Innervated by autonomic sensory nerves (visceral affronts, from which sensation is not normally registered consciously).
14
Q
What are the costodiaphragmatic and costomediastinal recesses?
A
Costodiaphragmatic recess: A gutter around the periphery of the diaphragm, where the costal pleura becomes continuous with the diaphragmatic pleura.
Costomediastinal: lies at junction of costal and mediastinal pleura. The lungs expand into these spaces during deep inspiration.
15
Q
Draw the anatomy of the lungs.
A
16
Q
What are the words used to describe areas of the lungs?
A
Costal surface - adjacent to ribs.
Mediastinal surface - adjacent to the heart.
Diaphragmatic surface - interior surface of the lung.
Anterior border - shape and tapered.
Posterior border - thick and rounded.
Inferior border - sharp and tapered.
17
Q
What is the root and hilum of the lung?
A
The root of the lung lies between heart and lung, comprising pulmonary artery and vein and the main bronchus.
The hilum is the region on the mediastinal surface where the root is.
At the hilum of the right lung, the main bronchus lies anterior to the pulmonary artery.
At the hilum of the left lung, the main bronchus lies inferior to the pulmonary artery.
At both hila, the pulmonary veins are the most anterior and inferior vessels.
18
Q
How does the bronchial tree split?
A
- Trachea divides left and right at the level of the sternal angle. Contains cartilage and smooth muscle.
- Right main bronchus is shorter, wider and descends more vertically than the left. A foreign body is more likely to enter the right main bronchus.
- Main bronchus divides into lobar bronchi (three in right, two left, one for each lobe).
- Lobar bronchi give rise to segmental bronchi. There are 10 segmental bronchi in each lung. Each supplies an independent region of the lung, called a bronchopulmonary segment.
- Segmental bronchi continue to divide into bronchioles (they become smaller with each division). Bronchioles are made of smooth muscle.
- The alveoli are where gas exchange takes place in the lung.
All muscle is under autonomic control.
19
Q
Describe the blood and lymph supply of the lungs.
A
Pulmonary arteries carry deoxygenated blood to the lungs. Bronchial arteries from the descending aorta supply the lungs.
Pulmonary veins return deoxygenated blood to the heart from the lungs.
Bronchial veins return blood to the azygos system of veins.
Lymph is drained via the thoracic duct or right lymphatic duct.
20
Q
Describe nervous supply to the lungs.
A
Controlled by autonomic nerves:
* Parasympathetic fibres stimulate:
Bronchostriction
Secretion from glands of bronchial tre.
- Sympathetic fibres:
Bronchodilation.
Inhibit secretion.
Somatic sensory fibres innervate the parietal pleura.
Visceral afferents to relay unconscious sensory information from the lungs and visceral pleura to CNS.
21
Q
Describe the surface anatomy of the lobes and fissures
A
Oblique fissure of both L and R lungs extends from 4th posteriorly to 6th costal cartilage anteriorly. The fissure runs deep to the 5th rib.
Horizontal fissure of the R lung extends anteriorly from 4th costal cartilage and intersects the oblique fissure.
22
Q
What are the functions diaphragm, and how does it contract?
A
Thin, domed sheet of skeletal muscle.
Integral to mechanics of breathing.
Separates thoracic and abdominal cavities.
During inspiration, the diaphragm contracts, pulling the ends of the muscle fibres towards their peripheral attachments, so the domes flatten. This increases volume of the thoracic cage so the lungs expand.
During expiration, the diaphragm relaxes and domes superiorly. Decreases volume and drives air from lungs.
23
Q
How is the diaphragm attached and innervated?
A
To the xiphoid process, costal margin (and to tips of 11th and 12th ribs) and the lumbar vertebrae.
The central part is called the central tendon (it is not muscular).
The right and left phrenic nerves innervate the right and left side of the diaphragm, respectively. They are somatic, formed from C3 and C4 and C5 spinal nerves. Contain motor and sensory fibres.
24
Q
Describe inspiration
A
- The diaphragm and external intercostal muscles contract, increasing intrathoracic volume. (External intercostals pull ribs superiorly and laterally, so ribs pull sternum superiorly and anteriorly, increasing lateral dimensions of thoracic cavity).
- Due to surface tension, the lungs expand with the thoracic wall (increase in volume).
- Pressure in lungs decreases below atmospheric pressure send air is drawn into lungs.
25
Describe expiration.
1. Diaphragm and intercostal muscles relax, internal intercostal muscles contract, decreasing intrathoracic volume.
2. Lungs recoil (decrease in vol).
3. Pressure in lungs increases above atm, so air is expelled.
26
How to the muscles involved in breathing change?
* Normally, quiet breathing, inspiration is active, expiration is passive. Inspiration mainly driven by movement of diaphragm.
* In vigorous breathing (exercise) the intercostal muscles become important. Active expiration uses internal intercostal muscles.
* in very vigorous breathing, accessory muscles, like pectorals, contribute to movement of ribs and aid ventilation.
27
What is the mediastinum?
The part of the thoracic cavity that lies between the lungs. It contains things like the heart, oespohagus, trachea etc. There is the inferior and superior mediastinum, separated at the sternal angle anteriorly to the T4/T5 junction posteriorly:
28
What is the inferior mediastinum?
The inferior mediastinum is divided into anterior, middle and posterior compartments:
*Anterior mediastinum lies between the posterior aspect of the sternum and the anterior aspect of the pericardial sac. It is a narrow space, and contains the thymus gland in children and its remnant in adults.
* middle contains the heart inside the pericardial sac, the pulmonary trunk and the ascending aorta.
* Posterior mediastinum lies between posterior aspect of pericardial sac and the vertebrae.
29
What is the superior mediastinum?
The main contents of the superior mediastinum are the:
● arch of the aorta and its three branches
● superior vena cava and its tributaries - the left and right brachiocephalic veins
● trachea
● oesophagus
● phrenic nerves (left and right) and vagus nerves (left and right)
● thoracic duct
● thymus gland
30
Describe the aorta and it's branches
Ascending aorta is the short, first part, which gives rise to the coronary artery which supply the myocardium.
The arch of the aorta curves posteriorly, and lies in the superior mediastinum. This arch gives rise to three major branches that support the upper body:
● First, the brachiocephalic trunk. It bifurcates into the right common carotid artery (which supplies the right side of the head and neck, including the brain) and the right subclavian artery which supplies the right upper limb.
● Second, the left common carotid artery, which supplies the left side of the
head, neck, and brain.
● Third, the left subclavian artery, which supplies the left upper limb.
The descending (thoracic) aorta descends through the posterior mediastinum and into the abdomen posterior to the diaphragm.
31
What are the aortic bodies?
In the arch of the aorta, chemoreceptor cells constantly monitor arterial oxgyen and carbon dioxide. The CNS receives this information via the vagus nerve and results in reflex responses that regulate ventilation.
32
What is the ligamentum arteriosum?
The ligamentum arteriosum is a fibrous, cord-like connection between the pulmonary trunk and the arch of the aorta. It is the remnant of the ductus
arteriosus, a foetal circulatory shunt. In the foetus, gas exchange occurs at the placenta, not in the lungs. The ductus arteriosus diverts most of the blood entering the pulmonary trunk directly to the aortic arch (only a small amount of blood
circulates through the foetal lungs; enough for them to develop). When a baby starts to use their lungs at birth, the ductus arteriosus closes, and blood in the pulmonary trunk enters the lungs.
33
What is the vena cava?
The two large veins that carry deoxygenated blood from the body to the heart.
The superior vena cava (it and all all its tributaries also lie in superior mediastinum) returns blood from the head, neck and upper limbs.
● The SVC is formed by the union of the left and right brachiocephalic veins (brachium = arm; cephalic = head).
● The union of the internal jugular vein (which drains the head and neck) and the subclavian vein (which drains the upper limb) forms each brachiocephalic vein.
The inferior vena cava returns blood from all regions inferior to the diaphragm.
34
What is the general structure of the trachea?
It is semi rigid due to C chaped rings of cartilage.
● 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 (and junction between the T4 and T5 vertebrae) by bifurcating into the left and right main bronchi.
35
What are the phrenic nerves?
Left and right phrenic nerves, formed by fibres from C3, C4 and C5 spinal nerves. They innervate the diaphragm, and are somatic nerves. They enter the thorax through the superior thoracic aperture, coursing over the pericardium and piercing the diaphragm.
36
Describe the vagus nerves.
L and R vagus nerves arise from the brainstem, containing somatic sensory, somatic motor and parasympathetic fibres. They innervate the structures of the thorax, abdomen, head and neck.
● They descend through the neck alongside the internal carotid artery and internal jugular vein and enter the thorax via the superior thoracic aperture.
● They each give rise to a recurrent laryngeal nerve (RLN), which ascend back up into the neck to innervate the muscles of the larynx.
● 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 descends anterior to the right subclavian artery and then loops under the inferior border of the artery before ascending back up the right side of the neck (between the trachea and oesophagus) to the
larynx.
● The vagus nerves descend in the thorax posterior to the root of the lung.
● They contribute parasympathetic fibres to the heart, lungs, and oesophagus.
● They traverse the diaphragm and convey parasympathetic fibres to most of the abdominal viscera.
37
What is the thoracic duct?
A major channel for lymphatic drainage for most regions of the body. It ascends through the posterior mediastinum and into the superior mediastinum, where it empties into the venous system at the union of the left internal jugular vein and left subclavian vein.
38
Describe the pericardium.
A tough, fibrous bag that loosely encloses the heart.
Two layers:
* Tough, outer fibrous later. Superiorly attached to the great vessels and interiorly to the central tendon of the diaphragm. L and R phrenic nerves give rise to sensory neurones that innervate the fibrous pericardium.
* Inner serous layer that is thin. Parietal layer lines the inner aspect, visceral layer covers the surface of the heart, separated by the pericardial cavity, containing pericardial fluid. The fluid allows the layers to slide over each other during contraction. The layers are continuous.
39
Name the surfaces of the heart.
● Base / posterior surface = left atrium, part of the right atrium
● Inferior / diaphragmatic surface = left ventricle, part of the right ventricle
● Anterior / sternocostal surface = right ventricle
● Left pulmonary surface = left ventricle
● Right pulmonary surface = right atrium
* Apex is at the LV at the 5th intercostal space in the midclavicular line.
40
Describe the borders of the heart relative to surface landmarks
● Right border (RA) = lies lateral to the right sternal edge, from the right 3rd costal cartilage to the right 6th costal cartilage.
● Left border (LV) = extends from the left 2nd intercostal space to the left 5th intercostal space in the midclavicular line (i.e. the apex).
● Superior border = lies along the line connecting the superior extents of the right and left borders (i.e. from the right 3rd costal cartilage to the left 2nd intercostal space).
● Inferior border (RV and part of LV) = lies along the line connecting the inferior end of the right border with the apex (mostly formed by the right ventricle).
41
What are the auricles?
Ear-like outpouching from the walls of R and L atria.
42
What is coronary circulation?
Arteries and veins that supply the heart. Are visible on it's surface. Sulci are major arteries that lie in grooves on the external surface.
43
What are the coronary arteries?
L and R coronary arteries arise from ascending aorta and give rise to several named branches, which supply regions of the heart.
Cardiac veins return blood to the coronary sinus, which enters the right atrium.
44
Describe the right coronary artery and it's branches.
Supplies parts of conducting system of the heart, RA, RV, part of LV, part of interventricular septum.
Main branches:
* Branches to SAN and AVN supply these.
* Right marginal artery supplies inferior border of heart.
* Posterior interventricular artery (PIV) is the continuation of the right coronary artery on the diaphragmatic surface of the heart. It runs in the posterior interventricular sulcus and supplies both ventricles.
45
Describe the left coronary artery and it's branches.
Supplies parts of conducting system of heart, LA, most of LV, part of RV and part of interventricular system.
The LCA runs a short course before it divides into two large terminal branches. This short segment is the left main stem.
The two terminal branches are the anterior interventricular artery (or left anterior descending, LAD) and the circumflex artery (Cx).
The branches are as follows:
* LAD runs in the anterior interventricular sulcus towards the apex. Supplies both ventricles.
* One or two diagonal branches arise from the LAD.
* Circumflex artery runs around the heart onto the diaphragmatic surface, supplying LA, part of RV and part of LV.
* Left marginal artery arises from the circumflex and supplies LV.
46
Draw the anterior view of coronary circulation
47
Draw the posterior view of coronary circulation
48
What is right and left dominant circulation?
The posterior interventricular (PIV) artery (supplies much of LV) may arise from the right or left coronary artery, depending on the individual.
* Most people have right dominant circulation (PIV from right coronary). In these people, both R and L coronary arteries supply the LV.
* Those with left dominant circulation, PIV arises from Cx artery. Left coronary artery supplies entire LV.
(ie in someone who has left dominant circulation, blockage to the left main stem occludes blood flow to the entire LV)
49
Describe the right atrium.
Deoxygenated blood enters via the venae cavae, and from the heart via the coronary sinus. Main features follow:
* Interatrial septum - separates from LA.
* Fossa ovalis - a depression in the interatrial septum, a remnant of the foetal foramen ovale (in foetus, foramen ovale shunts oxugenated blood from RA to LA, bypassing the lungs).
* Crista terminalis - a muscular ridge that reparates the smooth walled posterior part of the atrium from the anterior part, which has a ridged, muscular wall. Ridges are pectinate muscles and extend to the right auricle (parts of RA on either side of crista have different embyrological origins).
The right atrioventricular valve is called the tricuspid valve. Blood flow is mostly passive, but RA does contract to fully empty.
50
Describe right ventricle
Pumps the blood it receives from RA into the pulmonary trunk, which bifurcates into a L and R pulmonary artery.
Backflow prevented by pulmonary valve at entrance of pulmonary trunk.'
Walls of RV thicker than walls of RA.
Features are:
* Interventricular septum separates it from the LV.
* Trabeculae carneae - muscular ridges on the internal wall.
* Papillary muscles - modified regions of trabeculae carneae, which project into the lumen of the ventricle.
* Chordae tendineae - fibrous cords which connect 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.
51
Describe LA
Oxygenated blood from lungs via pulmonary veins (two from each lung). Like RA, smooth walled posterior part and anterior part with pectinate muscles.
Left atrioventricular valve aka mitral valve. Flow is mostly passive - contraction to fully empty.
52
Describe left ventricle
Pumps oxygenated blood into the aorta, through the aortic valve. The first branches from the aorta are the coronary arteries. Wall of LV is thickest as pump blood to whole body.
Like RV, LV contains:
* Trabeculae carneae.
* papillary muscles (two in LV)
* Chordae tendineae (connects tips of papillary muscles to mitral valve).
53
How do the atrioventricular valves work?
The valve cusps (which project into the ventricle) close passively when pressure rises.
The papillary muscles and chordae tendineae don't close the valves, but allow the closed valves to resist to the pressure generated, stopping them from being forced open.
When ventricle muscles contract, papillary muscle contract, tensing the cords and pulling on the valve cusps to prevent them from entering the atria.
54
Describe the semilunar valves
The aortic and pulmonary valves are called the semilunar valves as their cusps are half moon shaped.
Each valve has 3 semi-circular cusps. Each cusp is attached to the inner wall of the vessel with a free edge that projects it into the vessel lumen. Each cusp forms a pocket (sinus) between its free edge and the vessel wall.
The cusps are flattened onto the vessel wall during ventricular systole. Once pressure is greater in the (aorta or pulmonary trunk) than the ventricle, blood flows back and is immediately caught in the valve cusps. The sinuses fill with blood and the cusps balloon out into the lumen. the free edges of the three valve cusps contact each other in the lumen and the valve orifice closes.
In the aorta, the right and left coronary arteries arise from two of the three aortic sinuses, hence the coronary arteries fill during ventricular relaxation (diastole).
55
Where do we listen to the heart?
Heart murmurs are when the valves are abnormal or dysfunctional.
To listen to the valves, we listen to where the sound is transmitted, in the direction of blood flow. The auscultatory areas for each valve are:
● Aortic valve = 2nd intercostal space, just to the right of the sternum.
● Pulmonary valve = 2nd intercostal space, just to the left of the sternum.
● Tricuspid valve = 5th intercostal space, just to the left of the sternum.
● Mitral valve = left 5th intercostal space, midclavicular line.
56
Describe the conducting system of the heart
● Cells in the sinoatrial (SA) node spontaneously generate electrical impulses; it is the ‘pacemaker’ of the heart. It is located at the superior end of the crista terminalis.
● The SA node generates impulses at a rate of approximately 70 per minute.
● Impulses from the SA node stimulate contraction of the atria.
● Impulses are conducted to the atrioventricular (AV) node, located at the inferior end of the interatrial septum.
● From the AV node, conducting fibres form the atrioventricular bundle (Bundle of His).
● The atrioventricular bundle divides into two groups of fibres - the right and left bundle branches.
● The left and right bundle branches give rise to Purkinje fibres that enter the myocardium of the left and right ventricles, respectively, and stimulate
contraction.
57
How does blood supply of the conducting system vary anatomically between people?
* SA node is supplied by RCA in 60%, by LCA in 40%.
* AV node is usually supplied by the posterior interventricular artery. In most people, the PIV arises from the RCA.
* In most people, the LCA supplies the Bundle of His.
58
What does the posterior mediastinum contain?
* Descendinf aorta
* Azygos veins
* oesophagus
* thoracic duct
* sympathetic trunk and splanchnic nerves.
* posterior intercostal vessels and nerves
59
Describe the branches off of the descending (thoracic) aorta.
* posterior intercostal arteries which supply the intercostal spaces.
* brachial arteries which supply the lungs.
* oesophageal branches which supply oesophagus
* pericardial branches which supply the pericardium
* phrenic branches which supply the diaphragm.
The aorta passes through the diaphragm at the level of t12.
60
What are the Azygos veins?
Arises at L1/L2 level in the abdomen. Traverses the diaphragm to enter the posterior mediastinum.
They drain blood from the posterior thoracic wall, returns it to the superior vena cava.
They lie on the thoracic vertebrae.
Course varies, but arrangement is typically:
* an azygous vein on the right side of the vertebral bodies.
* a smaller, shorter hemiazygous vein on the left side of the vertebral bodies.
* one or more veins connecting the above veins to each other.
The azygos system receives blood from the posterior intercostal veins, oesophageal veins and bronchial veins.
61
Describe the structure of the oesophagus
Lies right of aorta, in the posterior mediastinum.
Supplied by oesophageal arteries (from d aorta).
Oesophageal veins return venous blood to the azygos system.
Innervated by
At T10, the oesophagus passes through the oesophageal hiatus in the diaphragm.
62
Describe the function and structure of the thoracic duct
It returns most of the body’s lymph to the venous system. It lies between the azygos vein and the aorta.
* lymph from the lower body flows towards the cisterna Chyli, a sac like swelling that gives rise to the thoracic duct, which ascends into the thorax,
* in the thorax, The duct receives lymph from intercostal spaces and lymph nodes.
* the duct ascends into the neck, receiving lymph from the left side of head and left side of neck and left upper limb.
* terminates by opening into the venous system at the junction between the left internal jugular vein and the left subclavian vein
(Right is drained by lymphatic ducts which enter the venous system as the junction between right internal jugular and right subclavian veins).
63
What are the sympathetic trunks?
Groups of nerves that innervate parts of the upper body.
CNS The two trunks lie on the posterior thoracic wall, either side of the vertebral column and posterior to the parietal pleura. They are thin, longitudinal fibres interspersed with ganglia (known as paravertebral ganglia).
The cell bodies of preganglionic sympathetic neurones lie in the thoracic and upper lumbar spinal cord segments (T1 -L2/3). They exit the spinal cord in spinal nerves T1-L2/3 from it’s ventral aspect and enter spinal nerves T1-L/3 along with somatic motor nerves, whose cell bodies lie in the grey ventral horn.
To summarise:
* Preganglionic sympathetic fibres exit the spinal cord in spinal nerves T1-L2/3.
* Almost immediately, they separate from the spinal nerves and enter the sympathetic trunk via a short connecting branch.
* Once in The sympathetic trunk, the preganglionic axon does one of the following:
1. Synapses in the ganglion at its level of entry.
2. Ascends or descend in the trunk before synapsing in a ganglion.
3. Travels through a ganglion and the trunk without synapsing.
In 1 and 2, the postganglionic axons leaving the ganglia:
* Enter spinal nerves via a communicating branch (grey ramus communicans). Through this, sympathetic fibres enter all 31 pairs of spinal nerves.
* form visceral nerves that convey sympathetic fibres to the head.
* Form visceral nerves that convey sympathetic fibres to the thoracic viscera (cardiopulmonary splanchnic nerves).
64
What is ganglia?
A collection of cell bodies outside the cns
65
What are the different plexuses?
Sympathetic and parasympathetic fibres form autonomic plexuses around the thoracic viscera. They look like delicate fine meshes. In the thorax, there is the:
* cardiac plexus - Innervate the SAN. Parasympathetic and sympathetic (travel to cardiac plexus from T1-T5 via cardiopulmonary splanchnic nerves) fibres.
* pulmonary plexus - innervate the bronchi. Sympathetic stimulation relaxes the bronchi. Parasympathetic stimulation constricts them.
* oesophageal plexus - overlies anterior surface of oesophagus. Sympathetic fibres inhibit peristalsis and parasympathetic fibres stimulate peristalsis.
Visceral afferents relay sensory information from the thoracic viscera back to the CNS along paths of the vagus and thoracic splanchnic nerves.
66
67
How are the thoracic viscera innervated?
The cardiopulmonary splanchnic nerves convey postganglionic sympathetic fibres to the thoracic viscera.
Vagus nerves convey parasympathetic fibres to the thoracic viscera.
68
How is the heart innervated?
Why do we perceive cardiac pain from different parts of the body?
Cardiopulmonary splanchnic nerves deliver impulses from the T1-T5 spinal chord segments to the cardiac plexus and heart.
Visceral sensory nerves convey sensory information from the heart back to the CNS (not generally conscious perception).
If myocardium is ischaemic, it does, as pain, by visceral nerves which take the signal to t1-t5.
Somatic sensory information from the skin of the chest wall, neck and arm also return to t1-t5.
Therefore for an unknown reason, the brain interprets this as pain from the skin around the upper body.
69
What structures are in the neck?
* Structures of the respiratory tract - pharynx, larynx and trachea.
* structures of the gastrointestinal tract - pharynx and oesophagus
* Glands - thyroid and parathyroid glands.
* artieries and veins
* nerves
* muscles - those that move the head and neck. Also the platysma, a thin subcutaneous muscle deep to the skin of the neck.
70
Describe the bones and cartilage in the neck.
Seven cervical vertebrae.
Hyoid bone - slender bone situated anteriorly in the upper neck, inferior to the mandible. It helps to keep the pharynx open and provides an attachment point for several muscles in the neck and tongue.
Larynx - small cartilages connected by membranes and small joints. It protects the airway. Muscles attach to the laryngeal cartilages and move them, in turn moving the vocal cords.
71
What are the triangles of the neck?
There are 2 - the anterior and posterior triangles, separated by the sternocleidomastoid muscle.
72
What is the sternocleidomastoid muscle?
This muscle is attaches to the sternum, clavicle and mastoid process (part of temporal bone).
It can act unilaterally or bilaterally.
It is innervated by the accessory nerve (cranial nerve XI).
73
Describe the anterior triangle
The boundaries are:
* Anteriorly - midline of the neck
* Posteriorly - anterior border of sternocleidomastoid muscle.
* Superiorly - lower border of the mandible.
The anterior triangle contains:
* trachea and larynx
* thyroid gland, parathyroid glands, submandibular salivary gland
* suprahyoid muscles (connect hyoid to the skull). They form the floor of the mouth. They move the hyoid and larynx in speech and swallowing.
* infrahyoid muscles (strap muscles). Connect hyoid to the sternum and scapula. Move hyoid in speech and swallowing.
* common carotid artery and it’s terminal branches (ext and int).
* internal jugular vein.
* branches of the facial nerve (CN VIII), the glossopharyngeal nerve (CN IX), the vagus nerve (CN X), the accessory nerve (CN XI) and the hypo gloss all nerve (CN XII)
74
What is the posterior triangle?
Boundaries are:
Anteriorly - posterior border of sternocleidomastoid muscle.
Posteriorly - anterior border of trapezius.
Inferiorly - clavicle.
Superiorly - apex of the triangle is formed from the sternocleidomastoid and trapezius.
The posterior triangle contains:
* Muscles that move the head,
* Paet of subclavian artery and subclavian vein.
* the external jugular vein (drains scalp and face).
* accessory nerve (XN XI)
* Roots of the brachial plexus (spinal nerves that supply upper limb).
* cervical plexus (fibres from c1-c4).
* The phrenic nerve.
75
Describe the suprathyroid muscles.
Four paired muscles (mylohyoid, geniohyoid, stylohyoid, digastric).
They lie superior to the hyoid bone and form the floor of the mouth.
During contraction, they raise the hyoid bone and larynx during speech and swallowing.
76
Describe the infrahyoid muscles,
Four paired strap muscles lying inferior to the hyoid bone just lateral to the midline of the neck. They draw the larynx and hyoid bone inferiorly during speech and swallowing.
Four muscles:
* Sternohyoid and omohyoid lie superficially. They attach the hyoid to the sternum and scapula, respectively.
* Steenothyroid lies deep. Attaches the sternum to the thyroid cartilage.
* thyrohyoid lies deep. Attaches thyroid cartilage to hyoid.
77
What is the thyroid gland?
It produces hormones which play an important role in the regulation of metabolic processes. The pituitary gland regulates hormone secretion from the thyroid gland.
It is composed of right and left lobes that lie just lateral to the lower larynx and upper trachea. Each lobe lies deep to the sternothyroid muscle.
The two lobes are joined by the isthmus, which lies anterior to the trachea.
Blood supply:
* Left and right superior thyroid arteries. Branches of the external carotid artery.
* The left and right inferior thyroid arteries - branches of the thyrocervical trunks (which are branches of the subclavian artery).
* Superior, middle and inferior thyroid veins drain the gland,
Some people have an additional thyroid ima artery.
78
Describe the parathyroid glands
Usually four - right and left superior and inferior glands. Located posterior to the thyroid gland.
They produce parathyroid hormone which plays a role in Calcium regulation.
They are typically supplied by the inferior thyroid arteries.
79
What are the arteries in the neck?
The common carotid arteries and the subclavian arteries.
Common carotid arteries: ascend in the R and L sides of the neck. They bifurcate into external and internal carotid arteries.
* internal carotid artery enters the cranium and supplies the brain. No branching in the neck.
* External carotid artery gives rise to several branches that supply the head neck (inc pharynx, tongue, scalp, thyroid gland, face).
* at the point of bifurcation, there is a small swelling - the carotid sinus. Here, baroreceptors monitor arterial blood pressure. Visceral sensory information that results in refuel responses is relayed back to the CNS via the glossopharyngeal nerve.
Subclavian artery supplies the upper limb and gives rise to several vessels.
A large branch, the thyrocervical trunk, gives rise to the inferior thyroid artery.
80
What veins are in the neck?
* internal jugular vein. Drains blood from parts of the face and the brain
* the internal jugular vein unites with the subclavian vein, which returns blood from the upper limb, to form the brachiocephalic vein.
* the R and L brachiocephalic veins unite to form the superior vena cava.
* the external jugular
81
Describe the nerves in the neck
* facial nerve (CN VII) supplies platysma in the neck.
* glossopharyngeal nerve (CN IX) supplies:
Pharynx (sensory innervation)
Carotid sinus (visceral sensory fibres that return to the CNS via CN IX)
* The vagus nerve (CN X) is vital for speech and swallowing, it supplies:
Muscles of the pharynx (motor innervation)
The larynx (motor and sensory)
The carotid sheath comprises the vagus nerve that runs between the internal jugular vein and the internal carotid artery (above its bifurcation), and between the internal jugular vein and common carotid artery (below its bifurcation). These three structures run together is a fascial sleeve (carotid sheath).
* the accessory nerve (CN XI) and supplies the sternocleidomastoid and trapezius muscles.
* the hypoglossal nerve (CN XII) is motor to muscles of the tongue, so it only travels through the neck. It lies lateral to the internal carotid artery and deep to the external jugular vein.
* the phrenic nerve is formed from c3, c4 and c5 nerve fibres. It descends through the neck to enter the thorax and innervate the diaphragm.
* the head and neck are richly innervated with sympathetic nerves. The sympathetic trunk extends as far as the base of the skull. The associated sympathetic ganglia in the neck are superior, middle and inferior cervical ganglia. Postganglionic fibres from these ganglia innervate the head and neck.
82
What are the abdominopelvic splanchnic nerves.
* The greater splanchnic nerve (sympathetic preganglionic fibres originating from T5 -T9 segments of the spinal cord).
* Lesser splanchnic nerve (from T10-11)
* Least splanchnic nerve (from T1)
* lumbar splanchnic nerves (from L1-L2)
The greater, lesser and least are formed in the posterior mediastinum and traverse the diaphragm to enter the abdomen.
The preganglionic sympathetic fibres in these splanchnic nerves do ultimately synapse with second neurones in prevertebral ganglia that lie close to major blood vessels in the abdomen. After synapsing, the postganglionic fibres innervate abdominal viscera.
83
Show structure of the pharynx
84
What is the muscular structure of the pharynx?
Outer layer of circular muscle. Composed of superior, middle and inferior constrictors that overlap. They contract superior to inferior, to move swallowed food down the oesophagus.
Inner layer of longitudinal muscle.
85
How does swallowing work?
Food in the oral cavity is pushed into the oropharynx by the tongue. The soft palate rises and closes off the nasopharynx from the oropharynx. Food enters the laryngopharynx and pharyngeal muscles constrict to move food into the oesophagus.
The epiglottis (one of the cartilages of the larynx) closes off the laryngeal inlet, preventing food from entering the larynx.
86
Describe the innervation of the pharynx.
Sensory innervation from glossopharyngeal nerve fibres,
Motor innervation from vagus nerve fibres.
87
Describe the structure of the laryngeal skeleton.
Nine cartilages. Three paired (much smaller), three unpaired. Membranes and very small joints connect the cartilages.
Three unpaired:
* Thyroid. The thyroid cartilage is composed of two flat cartilages (laminae) that meet in the anterior midline to form the laryngeal prominence (adam’s apple).
Posteriorly, the laminate form extensions that project superiorly and inferiorly (superior and inferior horns).
The superior horns attach to the hyoid bone.
The inferior forms articulate with the cricoid cartilage below.
* Cricoid. The ciricothyroid membrane connects the inferior border of the thyroid and superior border of the cricoid.
* Epiglottis. The epiglottis is attached to the superior aspect of the thyroid cartilage, where two thyroid laminae meet.
Three paired:
* Arytenoids. Sit on upper surface of the cricoid cartilage. They articulate with the cricoid cartilage at small joints. Arytenoids are vital for phonation as the vocal cords attach to them. Movement of the Arytenoids moves the vocal cords.
* Cuneiforms
* Corniculate.
88
What is the laryngeal prominence?
The thyroid cartilage is composed of two flat cartilages (laminae) that meet in the anterior midline to form the laryngeal prominence (adam’s apple).
Posteriorly, the laminate form extensions that project superiorly and inferiorly (superior and inferior horns).
The superior horns attach to the hyoid bone.
The inferior forms articulate with the cricoid cartilage below.
89
What are the muscles of the larynx?
The two groups of muscles that act upon the larynx:
* Extrinsic muscles - the suprahyoid and infrahyoid muscles. They move the whole larynx (as opposed to individual cartilages).
* Intrinsic muscles - small muscles that move the cartilages on the larynx relative to each other. This in turn moves the vocal cords, altering speech.
90
What are the surface markings on the neck?
91
Describe the tonsils
The pharyngeal and tubal tonsils are found in the nasopharynx:
* pharyngeal tonsil (adenoid) is on the roof of the nasopharynx.
* Tubal tonsil surrounds the opening of the auditory tube (which connects the nasopharynx to the middle ear).
The palatine tonsil lies next to the pharyngeal wall in the oropharynx.
The lingual tonsil is a collection of lymphoid tissue on the posterior aspect of the tongue.
92
Describe the salivary glands
Three pairs of salivary glands. Stimulated by parasympathetic fibres.
Parotid gland:
* largest
* overlies posterior part of the mandible.
* the parotid duct empties saliva into the mouth, opening adjacent to the upper second molar tooth.
* stimulated by parasympathetic fibres of the glossopharyngeal nerve.
* the facial nerve runs deep to the parotid gland after exiting the skull. The nerve splits into five branches within the gland, to innervate the muscles of facial expression.
Submandibular glands:
* part lies in and part lies outside of the mouth.
* opening is into the floor of the mouth under the tongue.
* saliva secretion is stimulated by parasympathetic fibres of the facial nerve.
Sublingual glands:
* small and lie in floor of the mouth.
* open via several small ducts into the floor of the month.
* stimulation is by parasympathetic fibres of the facial nerve.
93
Describe the structure of the vocal cords
Two pairs of folds, vestibular folds (false vocal cords) superiorly and the vocal folds (true vocal cords) inferiorly, separated by a narrow space.
* the vestibular folds are folds of mucous membrane that lie superior to the vocal folds.
* the vocal folds are folds of mucous membrane that cover and protect the vocal ligaments. Together, they form the true vocal cords
* the vocal ligaments are attached anteriorly to the internal aspect of the laryngeal prominence and posteriorly to the arytenoid cartilages.
* the space between the true vocal cords in the rima glottidis. Adduction of the true vocal cords closes the rima glottidis, whilst abduction of the folds opens it.
* therefore phonation requires adduction of the cords and closure of the rima glottidis.
Abduction of the cords opens the rima glottidis:
* to a small degree when whispering.
* partially during normal breathing.
* fully when forced breathing.
The intrinsic muscles of the larynx move the laryngeal skeleton which moves the vocal cords and opens and closes the rima glottidis.
94
Describe the main intrinsic muscles that move the vocal cords
* cricothyroid muscle, anterior (Between thyroid and cricoid cartilages). This muscle tips the thyroid cartilage anteriorly and inferiorly which places tension on the vocal cords. Innervated by the superior laryngeal nerve (branch from vagus) and is sensory to the larynx above the vocal cords.
* posterior cricoarytenoids - on the posterior surface of the cricoid. They abduct the vocal cords, opening the rima glottidis.
* transverse Arytenoids on the posterior aspect of the larynx connect the two Arytenoids cartilages. They adduct the vocal folds and close the rima glottidis.
The recurrent laryngeal nerve (from vagus) innervated all intrinsic muscles bar cricothyroid. It is sensory to the larynx below vocal cords.
