Osteopathy Journals and Research by Darren Chandler

 

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  1. LAYERS OF THE PERICARDIUM

    The pericardium is located behind the sternum and r2-6 costal cartilages. It is separated into an outer and inner layer:

    • Outer layer: fibrous pericardium. This is the strong fibrous part of the sac. This layer is continuous into the sheaths of the vessels which pierce it (aorta, pulmonary trunk, superior and inferior vena cava and the pulmonary veins).
    • Inner layer: serous pericardium. The serous pericardium is divided into parietal and visceral layers.
      Parietal layer of the serous pericardium: lines the fibrous pericardium. It is reflected around the roots of the great vessels to become continuous with the visceral layer. 
      Visceral layer of the serous pericardium (aka epicardium): it is closely applied to the heart. 
      Pericardial cavity: lies between the parietal and visceral layers. Contains the pericardial fluid that acts as a lubricant to facilitate movement of the heart.

    Marchand (1951) found at the anterior origin of the aorta the fibrous and serous layers of the parietal pericardium are separated by loose connective tissue. Over the ventricles, however, the two layers become firmly adherent to each other.

    Fascial sheaths derived from the fibrous pericardium invest the great vessels in their extrapericardial course: the ascending aorta, the pulmonary trunk (branches into the right and left pulmonary arteries), the pulmonary veins and the superior vena cava. Note the fascial sheets from the fibrous pericardium don’t invest the inferior vena cava.

    The fascial sheaths of the pulmonary arteries and veins are prolonged around these vessels into the substance of the lung.

    At the hilum of the lung this fascia is more loosely attached to the pulmonary arteries and veins but it becomes more adherent blending with the outer coat of the vessels as they begin to branch along their progression through the lung.

    LIGAMENTS OF THE PERICARDIUM

    Sternal ligaments

    Ligamenta sterno-pericardiaca

    • Superior (sterno-costo-pericardiacum) ligament: consists of two groups of fibres. Superior end of the sternum --> anterior wall of the pericardium below the large vessels of the heart. Suspends the pericardium in both vertical and horizontal positions.
    • Inferior (xipho-pericardiacum) ligament: xiphoid process --> ascends towards the anterior wall of the pericardium. Suspends the pericardium in a horizontal position.
    • Ligamentum sterno-pericardiacum medium: sometimes another group of ligaments extends from the middle part of the sternum and the neighbouring costal cartilages --> anterior wall of the pericardium.

    Anterior ligamenta phreno-pericardiaca

    The anterior ligamenta phreno-pericardiaca is the connective tissue that attaches the the top of the central tendon of the diaphragm to the bottom of the fibrous pericardial sac. These attachments span from the left side (near the apex of the heart) to the right side (anterior to the inferior vena cava).

    These fibers can be followed superiorly into the adventitial layer of the aorta and pulmonary artery.

    The attachments of this ligament must be considered together with the fibres which pass from the various large blood vessels of the heart into the anterior wall of the pericardium. 

    During inspiration when the diaphragm contracts and moves downward, the pericardial sac and the heart are pulled down and elongated. The phrenopericardial ligament is the fulcrum around which the diaphragm is supported when it comes to distribute its contractile tension laterally (Bordoni and Zanier 2013).

    Ligamentum vertebro-pericardiacum (ligament of Beraud or ligamentum superius pericardii)

    Popa & Lucinescu (1932) believed this ligament does not exist but did acknowledge some longitudinal fibres placed on the posterior aspect of the pericardium which might be taken for such a ligament (refer to 'fibers of the pericardium' 1b).

    Vertebro-pericardiacum: C6-T1 --> pericardium: base of the posterior aspect of the pericardium.

    Fibers in the pericardium

    Popa & Lucinescu (1932) distinguish an outer and inner layer of fibres which are thin in the anterior wall of the pericardium and very thick in the posterior wall.

    1. Outer layer of fibers in the pericardium.

    1a. Anterior wall of pericardium.

    • Fasciculus xipho-anonymus: xiphoid process --> along the anterior wall of the pericardium --> brachiocephalic artery (arteria anonyma). Its fibres intermingle with those of fasciculus phreno-aorticus dexter.
    • Fasciculus phreno-aorticus dexter: diaphragm: central tendon (right side) --> arch of the aorta. With some other fibres which continue farther on fasciculus phreno-anonymus (diaphragm: central tendon --> brachiocephalic artery).
    • Fasciculus aortico-apicalis: arch of aorta --> descends to the ventral side of the pericardium --> apex of the heart.
    • Ligamentum phreno-apicale: diaphragm: central tendon --> apex of the heart (pericardium).
    • Fasciculus phreno-aorticus sinister: diaphragm: central tendon --> arch of the  aorta.
    • Phreno-pulmonalis anterior: diaphragm: central tendon --> pulmonary artery.
    • Fasciculus aortico-cardiacus: ascending aorta --> left edge of the pericardium.
    • Fasciculus cavo-anonymus: inferior vena cava --> brachiocephalic artery.
    • Fasciculus cavo-pulmonalis:  inferior vena cava --> pulmonary vein. 
    • Fibrae transversae anteriores & fibrae xipho-apicales: these are horizontal fibers connecting longitudional fibers on the left side (fasciculus aortico-cardiacus) and on the right side (fasciculus cavo-anonymus & fasciculus cavo-pulmonalis). 
    • Starting from each pulmonary vein, bundles of fibres spread underneath and between all the above described bundles.
    • Ligamentum cardio-aorticum: a thick and large bundle of fibres completely blended with the fibrous ductus arteriosus (foetal blood vessel: pulmonary artery --> descending aorta). Anterior wall of the pericardium --> arch of the aorta.
    • Systems of circular fibres around every pulmonary vein producing inextensible rings around every venous orifice.

    1b. Posterior wall of the pericardium.

    The collagen fibres are extremely thick and grouped in large bundles generally directed longitudinally.

    Nearly all the bundles spread from the central tendon of the diaphragm --> small area lying behind and a little to the right of the inferior vena cava.

    Popa & Lucinescu (1932) failed to find the vertebro-pericardiac ligament attributing its existence to a long bundle of one of these ligaments (especially Teutleben's left ligament).

    These authors found long tracts of fibres ascending to various levels and producing loops around the pulmonary veins and arteries. The longest of these fibres pass up to the arch of the aorta and the bronchi.

    Fasciculus centro-atrialis sinister (& dexter): central tendon of diaphragm --> atrium: left (& right).

    Fasciculus centro-aorticus: central tendon of diaphragm --> arch of the aorta.

    Fasciculus centrotrachealis: central tendon of diaphragm --> trachea.

    Fasciculus centro-cardiacus I & II: central tendon of the diaphragm --> pericardium: posterior and left wall.

    2. Inner layer of fibers in the pericardium.

     2a. Anterior wall of the pericardium.

    Generally it is noticed that, whereas on the anterior aspect of the outer wall of the pericardium the fibres are orientated chiefly in a longitudinal direction, on the inner layer they almost run transversely.

    In this place there are very few fibres, and almost all are mere extensions from the posterior and lateral walls of the pericardium.

    • Fasciculus phreno-trachealis: a long bundle of fibres. Trachea --> posterior surface of the anterior wall of the pericardium.
    • Fibrae arciformes posteriors: some fibres running more or less transversely and coming from the left side of the pericardium.

    2b. Posterior wall of the pericardium.

    Three categories of bundles can be defined: longitudinal, transverse and circular.

    i. Longitudinal fibres.

    • Fasciculus phreno-trachealis: a long tract of fibres descends from the trachea -->  pericardium: through the diaphragmatic portion of the pericardium up to its anterior wall.
    • Annulus periatrialis (fibrae dextrae): right pulmonary veins --> descends --> inferior vena cava: near the inferior vena cava changes its direction to become transverse --> pericardium: surrounds the whole pericardium in front of the limit between atria and ventricles.
    • Fasciculus broncho-apicalis: large fasciculus. Both bronchi --> pericardium: lying over the apex cordis (rounded end of the left ventricle).
    • Fibrae verticals: large off shoot of fasciculus broncho-bronchi: both bronchi --> in front of the inferior vena cava.
    • Fibrae cavo-pulmonales superiores; fibrae cavo-hilares et bronchiales dextrae; fibrae cavo-pulmonales inferiors: on the posterior side of the inferior vena cava bundles of fibres ascend in front of or behind various components of the right hilum of the lung. 
    • Fibrae intercavae: inferior vena cava --> superior vena cava.
    • Fasciculus cavo-dorsalis, annulus periatrialis (fibrae dextrae and fibrae sinistrae), fasciculus aortico-periatrialis: several bundles, more or less vertical, become horizontal at their caudal end and form together large rings. These rings are called periatrial because of their position just between the atria and ventricles of the heart. 

    ii. Transverse fibres. 

    • Fibrae transversae interhilares posteriors: right root of lung --> left root of lung.
    • Fibrae transversae infrahilares: just below left root of the lung --> just below right root of the lung. 
    • Fibrae cavo hilares sinistrae, et dextrae: transversely from the inferior vena cava --> lung root.
    • Fibrae transversae interhilares anteriores: on an anterior plane. Right lung root --> left lung root. 
    • Fibrae transversae arciformes: root of lungs --> pericardium: lateral walls of the pericardium.
    • Fibrae phreno-pulmonales dextrae and sinistrae: pulmonary artery: bifurcation of the pulmonary artery --> pericardium: posterior wall of the pericardium. 
    • Fibrae phreno-aorticae: arch of the aorta --> pericardium: lateral wall of the pericardium. In this transversely orientated group of fibres terminate many oblique or vertical fibres which contribute to the formation of the periatrial rings. 

    iii. Circular fibres.

    • Pulmonary vein and arteries: strong rings are around these vessels.
    • Annulus perihilaris: long fibres round the roots of the lungs.
    • Annulus periatrialis: long fibres are grouped in a very large and thick rings which surrounds the whole pericardium in front of the limit between atria and ventricles. 

    THE MECHANICAL FACTORS WHICH MIGHT EXPLAIN THE ORIENTATION OF FIBRES IN THE PERICARDIUM

    Extrinsic mechanical factors 

    Respiratory movements exert a direct line of pull on the pericardium. These mechanical tensions, from inspiration, exerted on the pericardium, is generated from antagonistic lines of pull, in multiple directions, from the pericardial ligaments:

    • Sternum and ribs pull on the anterior wall of the pericardium during inspiration.
    • Diaphragm pulls the pericardium downward during inspiration.
    • Blood vessels and bronchi: superiorly and laterally the pericardium is fixed to the blood vessels: aorta, pulmonary artery and vena cava superior; and laterally it is also fixed to the pulmonary veins and bronchi. The bronchi elongate and dilate during inspiration stretching their connective tissue. All these points oppose the downwards pull of the diaphragm.
    • Roots of the lungs: on inspiration the roots of the lungs descend with the diaphragm and are pulled laterally (following the expanding thoracic wall) which laterally pulls on the pericardium. As the roots of the lung are posterior to the pericardium, during inspiration, the pericardium is simultaneously pulled posteriorly.
    • Trachea: the level of the bifurcation of the trachea maybe lowered by as much as two vertebrae during inspiration.

    In summary the pericardium is strongly fixed between four opposing points: transversely between the roots of the lungs, vertically between the diaphragm, the blood vessels, and, again, the roots of the lungs. The pericardium in such conditions becomes absolutely rigid and appears like a hard bony membrane.

    Therefore the greatest stress exerted upon the pericardium coincides with a combination of trunk extension and forced inspiration. This tenses all the longitudinal ligaments causing the shape of the pericardium to become more elongated and quite narrow, especially in its upper outline. 

    Conversley the greatest relaxation of the pericardium coincides with a combination of trunk flexion with forced expiration. This relaxes the longitudinal bundles of the pericardium to a certain degree. In this case the shape of the pericardium becomes short and large, and its upper outline is thick.

    As a result of such changes in the shape and position of the pericardium, the heart can move only laterally and vertically inside the pericardium.

    Effects of the sternum and ribs on pericardial movement

    Sternal and rib ligaments:

    • Ligamentum sterno-pericardiacum superius:  extended by the manubrium sterni at every inspiratory movement. Pulls the upper part of the pericardium upwards.
    • Ligamentum sterno-pericardiacum inferius: during inspiration the xiphoid process tenses the ligamentum sterno-pericardiacum inferius. Pulls the lower part of the pericardium downward.
    • Ligamentum sterno-pericardiacum medium: when present this ligament pulls the pericardium directly forwards.

    The antagonistic nature of these ligaments in a cranio-caudal direction produce tension in the anterior wall of the pericardium; this tension is directed longitudinally with a slight divergence backwards.

    These ligaments also work synergistically when they transmit the traction of the sterno-costal wall during inspiration to the pericardium. During inspiration the sternum moves anteriorly attempting to drag the pericardium with it. This anterior movement is resisted the posterior connections of the pericardium with the diaphragm around the inferior vena cava (< fasciculus centro-cardiacus, fasciculus centro-atrialis dexter, and ligamentum phreno-pericardiacum anterius dextrum). The trajectorial lines of forces in this case pass from the upper left side of the pericardium to the right inferior side and posteriorly, crossing the anterior wall of the pericardium diagonally. This line of force corresponds to the fibrae transversae anteriores.

    Effects of the diaphragm on pericardial movement

    The descent of the diaphragm causes a still greater effect upon the pericardium after the forward and upward movement of the anterior wall of the thorax is accomplished. When the ribs and sternum are fully stretched after the initial phase on inspiration further contraction of the diaphragm has a more concentrated pull upon the pericardium.

    The pull of the diaphragm is orientated in this case vertically from the diaphragm towards the arch of the aorta and brachiocephalic artery (refer to 'effects of the blood vessels on pericardial movement'), its greatest power being exerted on the posterior side of the pericardium. Particularly important is the posterior longitudinal bundles which fix a permanent distance between the central tendon of the diaphragm and the bronchi (and the roots of the lungs as a unit) via the fasciculus centro-aorticus, fasciculus centro-trachealis, and fasciculus centro-atrialis dexter et sinister.

    Effects of the blood vessels on pericardial movement

    During inspiration the trajectory of force is directed from the diaphragm through the pericardium up to the arch of the aorta and brachiocephalic artery.

    These trajectories are grouped especially along four principal lines:

    • Brachiocephalic artery --> inferior vena cava.
    • Aorta and pulmonary artery --> left side of the central tendon of the diaphragm.
    • Superior vena cava --> inferior vena cava.
    • Posteriorly: central tendon of the diaphragm --> arch of the aorta and other large blood vessels.

    These longitudinal sheets of resistance provide an excellent support for the transverse bundles, and together they form a strong membrane well planned for resistance to every direction of pull.

    Effect of movement of the roots of the lung on pericardial movement 

    The roots of the lungs on inspiration pull the pericardium laterally (following the expanding thoracic wall) and backwards (as the roots of the lung are posterior to the pericardium). The descent of the roots of the lungs during inspiration will exert a downward pull on the pericardium.

    This fact explains the presence of several strong bundles of fibres: fibrae transversae interhilares, fibrae transversae arciformes, fibrae transversae arciformes and fibrae transversae interhilares anteriores.

    This same mechanism explains the presence of transverse bundles of fibres which connect the pulmonary vessels to the pericardium: pulmonary artery (fibrae phreno-pulmonales sinistrae et dextrae) and the pulmonary vein (fasciculus transversus pericardiacus anterior).

    The strong ligaments of the central tendon of the diaphragm and the bronchi/roots of the lungs is defined by their inextensile nature. This causes the roots of the lungs and the central tendon to ascended and descended together at every movement of respiration like two structures firmly fixed to each other.

    Intrinsic mechanical factors

    Movement of the heart

    Because of the relations of the heart with the pericardium only the ventricles can move inside the pericardial cavity. Thus, the change of position that takes place is a certain rotation of the heart round its longitudinal axis, associated with the movement of the tip of the heart from left to right. Popa & Lucinescu (1932) believe that there is a relationship between these rotatory movements of the heart and the direction of the ligamentum cardio-aorticum.

    The heart as an active organ contains a variable amount of blood which causes it to vary in weight.

    In systole blood ejects from the heart and it becomes smaller and diminishes in weight; conversley in diastole blood enters the heart and it becomes larger and heavier.

    It is around the auricle that the pericardium is strongest and the fasciculi of fibres are best developed.

    Fasciculi periatriales dexter et sinister: large inextensible rings which encircle the thin walls of the auricles at their ventricular extremities. This ring is prolonged backwards by the thick wall of the pericardium. It plays the same role for the atria as the blood vessel rings for the pulmonary veins in that it assures a constant space for the atria. By its inextensibility it protects the atria against over dilatation and compression from the increase volume of the lungs during inspiration.

    Respiration 

    As well as traction being produced by the moving roots of the lungs, a great compressive power is set up by the expanding mass of the lungs acting upon the pericardium and heart.

    As the roots of the lungs separate strong perihilar rings hold together the pulmonary artery, pulmonary vein and bronchus. In addition, every pulmonary vein and pulmonary artery has a special ring which assures a constant opening at every moment of function. These rings protect the blood vessels, with their thin walls, against possible blood engorgement, and tendency to closure by external pressure.

    During respiration the pericardium also plays an important mechanical role in the redistribution of blood by changing the size of large arteries merely by traction exerted upon the arch of the aorta, brachiocephalic artery and carotid artery.

    As the diaphragm descends during inspiration the thoracic inlet (with the arteries) is raised. This increases the distance between these two points. The pericardium, which is is fixed to diaphragm inferiorly, and blood vessels superiorly, exerts a mechanical tension on the arch of the aorta, brachiocephalic artery and carotid artery. This is more notable when accompanied by trunk extension, a typical movement associated with inspiration. The effects of this mechanical tension on the blood vessels results in the ligaments pulling the blood vessels tight to restrict blood flow; or the ligaments relaxing to allow the blood vessels to open up and permit more blood flow:

    On inspiration/trunk extension the brachiocephalic artery, left >right carotid and left subclavian arteries decrease in diameter and a smaller quantity of blood is allowed to pass through. The surplus blood is passed on through the arch of the aorta and descending aorta into the abdominal organs. As a result bpm increases during inspiration/trunk extension.

    On expiration/trunk flexion the brachiocephalic artery, left>right carotid and left subclavian arteries increase in diameter and more blood can pass through. This will result in less blood surplus to pass through the arch of the aorta and descending aorta into the abdominal organs. As a result bpm decreases during expiration/trunk flexion.

    Therefore the pericardium by pulling on the arch of the aorta and large arterial blood vessels plays an important role as a mechanical device for the redistribution of blood between the head and upper limbs and the abdominal organs and lower limbs.

    Systolic/diastolic pressure in the arteries 

    During systole the force of the blood pushes vigorously against an arched tube, the arch of the aorta. Under such conditions there is a tendency for this arched tube to straighten out.

    If this was to be permitted it would:

    • Endanger the patency of openings in the brachiocephalic artery, left carotid and left subclavian artery.
    • Increase the distance between the left subclavian and descending aorta.

    As the pericardium is fixed to the arch of the aorta (fasciculus aortico-periatrialis), this arch remains almost fixed in systole. The arch of the aorta goes up and down as a unit and does not distend itself.

    The same effect upon the arch of the aorta is produced also by the ligamentum cardio-aorticum, fibrae aortico-subelaviales (descending aorta and left subclavian artery).

    Fascia pretrachealis

    Natale et al (2015) identified the fascia pretrachealis as part of the endocervical (visceral) fascia. The endocervical fascia corresponds to the endothoracic (subpleural) fascia in the thorax, to the endoabdominal (transversalis/subperitoneal) fascia in the abdomen, and to the endopelvic (subperitoneal) fascia in the pelvis. The continuity of these connective fascia is only interrupted by Sibson’s fascia (neck–thorax) and by the diaphragm (thorax–abdomen). 

    Details of the fascia pretrachealis is outlined here as its attachments to the trachea, bronchi, pericardium and blood vessles match those of the ligaments of the pericardium. Natale et al (2015) found a reference to the prevertebral fascia, as it descends in the posterior mediastinum, sending attachments to the pericardium, although this is not widely recognised.

    The following work on the fascia pretrachealis is based on that of Cavdar et al (1995). 

    The fascia pretrachealis is superiorly continuous with the buccopharyngeal aponeurosis. It is thin and translucent at its upper end and considerably thicker at its lower end. It is attached to:

    • Thyroid: attaches superiorly to the upper brim of the thyroid cartilage and laterally to its oblique line. Ensheaths the thyroid gland very firmly.
    • Trachea (neck): continues down over the trachea attaching laterally to the edge of the cartilagenous part of the trachea on both sides.
    • Retrosternal area: relates to the vessels of the retrosternal area.
    • Blood vessels and pericardium: attaches to the brachiocephalic vein and brachiocephalic artery. It then terminally fuses with the adventitia of the posterior aspect of the arch of the aorta and with the posterior aspect of pulmonary artery and the pericardium.
    • Trachea (thorax): laterally, at the bifurcation of the trachea, the fascia pretrachealis covers the angle between the trachea and main bronchus on either side. At the lower end of the trachea it forms a ring like structure formed by the fusion of the fascia pretrachealis to the brachiocephalic artery.
    • Bronchus: Marchand (1951) found the perivisceral fascia* (the part of this fascia that is around the trachea is the fascia pretrachialis) invests the left and right bronchi. Extrapulmonary the fascia is readily separated from the bronchi as it contains the bronchial artery, lymphatic vessels, and nodes. Intrapulmonary, after the bronchus enters the hilum of the lung the fascia becomes thinner and more adherent the further the lung is penetrated. Marchand (1951) identified it as the possible fascia that is prolonged around the bronchioles, and perhaps forms the alveolar septa.
    • Superior vena cava and pulmonary artery: after spanning the angle between the trachea and bronchus it fuses with the vascular sheath around the superior vena cava on the right and with the sheath of the pulmonary artery on the left.

    The lungs house fascial attachments from the perivisceral fascia and fibrous pericardium. The perivisceral fascia tightly adheres to the bronchi as they advance through the lung just as the fibrous pericardium attaches to the pulmonary artery and vein as they advance through the lung.

    Fascia pretrachealis is important in allowing the gliding movement of the trachea during swallowing

    The space between the fascia pretrachealis and the trachea is termed the "axial mediastinum".

    *: the perivisceral fascia includes the fascia pretrachealis (around the trachea); and the fascia around the oesophagus. Therefore the perivisceral fascia encloses the trachea and oesophagus collectively descending to the mediastinum and then blending with the outer coat of the stomach. Superiorly it attaches to the hyoid and runs continuous with the buccopharyngeal fascia. Posteriorly it is continuous with the prevertebral fascia. 

    References

    Anatomic connections of the diaphragm: influence of respiration on the body system (2013). Bruno Bordoni and Emiliano Zanier

    The Anatomy of Lamina Pretrachealis Fasciae Cervicalis (1995). S. CAVDAR, F. KRAUSE, H. DALCIK and Y. ARIFOGLU

    THE ANATOMY AND APPLIED ANATOMY OF THE MEDIASTINAL FASCIA  (1951) BY PAUL MARCHAND 

    Is the cervical fascia an anatomical proteus? (2015). Natale G, Condino S, Stecco A, Soldani P, Belmonte MM, Gesi M

  2. The endoabdominal fascia lines the abdominal cavity. It is comprised of:

    • Transversalis fascia: outer layer. Lies between the inner surface of the transverse abdominis muscle and the extraperitoneal tissue. 
    • Extraperitoneal tissue: this is a layer of connective tissue between the transversalis fascia and parietal peritoneum.
    • Parietal peritoneum (or fascia): this layer is a thin serous membrane acting as a balloon which lines the abdomen and into which the organs are pressed into from the outside. 
    • Visceral peritoneum (or layer): inner layer. This layer lines the organs and is known as the visceral peritoneum in the abdomen, pleura around the lungs (Gallaudet, 1931) and pericardium around the heart.

    Transversalis fascia

    Li (2012) defined the transversalis fascia as lining the inner surface of the transversus abdominis. It can be divided into two layers, superficial and deep with a dividing intermediate layer:

    • Superficial layer of the transversalis fascia: closely covers the internal surface of the transversus abdominis and its aponeurosis.
    • Intermediate layer: is an amorphous fibroareolar space filled with fat and loose fibrous tissue. It lies between the superficial and deep layers of the transversalis fascia.
    • Deep layer of the transversalis fascia: lies underneath the intermediate layer. It is seperated from the peritoneum by a loose amorphous fibroareolar space.

    Superiorly

    Superiorly the superficial and deep layers fuse to form the fascia covering the inferior surface of the diaphragm. Forming the subdiaphragmatic fascia the transversalis fascia travels through the medial and lateral arcuate ligaments and aortic hiatus to become the endothoracic fascia. Apaydin et al (2008) found the transversalis fascia also blended with the endothoracic fascia at the oesophageal hiatus to form the phrenico-esophageal ligament. This ligament attaches the oesophagus to the right diaphragmatic crura at the oesophageal hiatus.

    Anteriorly

    Anteriorly the superficial layer covers the inner surface of the transversus abdominis and the posterior rectus sheath (or the rectus abdominis muscle). The deep layer lines the outer surface of the peritoneum.

    Posteriorly

    Posteriorly the superficial and deep layers join together and form a continuous sheet anterior to the lumbar fascia.

    Running from an anterior to posterior direction the transversalis fascia courses laterally over the quadratus lumborum and then medially over the psoas major. At these points the transversalis fascia gets renamed the quadratus lumborum and psoas fascia respectively.

    As the transversalis fascia is the fascia of the quadratus lumborum and psoas it extends superiorly to form the subdiaphragmatic fascia. At this point it forms the arcuate ligaments and, with the endothoracic fascia, the phrenico-esophageal ligament (Apaydin eat al (2008).

    The lateral arucate ligament (rib 12 to L1 TP) is a thckening of the quadratus lumborum fascia. The medial arcuate ligament (L1 body to L1 TP) is a thickening of the psoas fascia.

    Laterally

    Laterally Li et al (2012) found the superficial and deep layers of the transversalis fascia to join at the:

    • Outer edge of the quadratus lumborum (at the level of the renal hilum)
    • Outer edge of the psoas major (at the level of L3).
    • Anterior axillary line.

    Also at the outer edge of the quadratus lumborum the transversalis fascia blends with the lateral conal fascia* (Li et al 2012).

    *: Lateral conal fascia is formed by the lateral fusion of the anterior and posterior renal fascia. It then travels laterally inrelation to the posterolateral aspect of the colon and fuses with the lateral parietal peritoneum.

    Inferiorly

    Inferiorly the transversalis fascia is continuous with the endopelvic fascia.

    Inferiorly Meyer (1927) found the transversalis fascia, along with the pelvic fascia with which it is continuous, tightly adherent to the pelvic brim. Hayes (1950) found anteriorly at the pelvic brim the transversalis fascia blends with the periosteum of the dorsal surface of the superior pubic ramus and pubic crest.

    Spaces between the superficial and deep layers of transversalis fascia

    The spaces between the superficial and deep layers of the transversalis fascia are:

    • Extraperitoneal space: the space between the superficial and deep layers of the transversalis fascia.
    • Retroperitoneal space: space behind the peritoneum in the abdominal cavity.
    • Retzius space: the space between the symphysis pubis and bladder. 
    • Retroinguinal (Bogros) space: is bound by the transversalis fascia anteriorly, the peritoneum posteriorly and the fascia iliacus laterally. 
    • The inferior epigastric vessels: these vessels penetrate the superior layer of the transversalis fascia as they originate from the external iliac vessels. They run in the matrix between the two layers and then penetrate the superficial layer of the transversalis fascia at the level of the linea arcuata and run into the rectus sheath.

    Peritoneum

    Parietal and visceral peritoneum

    • Parietal peritoneum (or fascia): this layer is a thin serous membrane acting as a balloon which lines the abdomen and into which the organs are pressed into from the outside. 
    • Visceral peritoneum (or layer): this layer lines the organs. It is known as the visceral peritoneum in the abdomen, pleura in the thorax (Gallaudet, 1931) and pericardium around the heart.
    • Between these parietal and visceral layers is a closed sac with a potential space. This space is called the peritoneal cavity, the pleural space and pericardial cavity.

    The parietal and visceral peritoneum are continuous at:

    • Sides and anterior surface of the ascending and descending colon.
    • Falciform ligament.
    • Lateral margin and part of the anterior surface of the left kidney.
    • Toldt's fascia: visceral peritoneum of the mesocolon fuses with the parietal peritoneum of the retroperitoneum. Separates the mesentery from the retroperitoneum.
    • Retroperitoneal segments of the bowel: most of the duodenum, ascending colon, descending colon and rectum.
    • Intraperitoneal bowel loops suspended by the mesentery: loop one (abdominal oesphagus, stomach and D1). Loop two (duodenojejunal junction, jejuneum, ileum and usually the caecum). Loop three (transverse colon). Loop four (sigmoid colon and occassionally the descending colon).

    In the region of the aorta and inferior vena cava the parietal peritoneum is continuous with the mesentery of the small intestine.

    Where the visceral peritoneum encloses or suspends organs within the peritoneal cavity, the peritoneum and its related connective tissue forms peritoneal ligaments, omenta and mesenteries.

    Peritoneal ligaments

    The peritoneal ligaments are formed by fused double layers of peritoneum:

    Gastrohepatic ligament: lesser omentum. Stomach: lesser curvature --> liver: fissure for ligamentum venosum.

    Hepatoduodenal ligament: free margin of the lesser omentum. Liver: porta hepatis --> D1 and D2: flexure between D1 and D2.

    Gastrosplenic ligament: left lateral extension of the greater omentum and lateral boundary of the lesser sac. Stomach: greater curvature --> spleen. 

    Splenorenal (lienorenal) ligament: left kidney --> spleen. Surrounds the pancreatic tail and extends to the left anterior pararenal space.

    Gastrocolic ligament: greater omentum. Stomach: greater curvature --> transverse colon.

    Transverse mesocolon & sigmoid mesocolon: the mesocolon attaches the colon to the posterior abdominal and pelvic wall. Refer 'mesenteries'.

    Falciform ligament: separates the liver into the right and left lobes. Peritoneum behind the right rectus abdominis and diaphragm --> Liver: courses cranially along the anterior surface of the liver, blending into the hepatic peritoneal covering and then carries on posterosuperiorly to become the anterior portion of the left and right coronary ligaments. Contains the ligament teres (round ligament).

    Ligamentum teres (round ligament): a remnant of the obliterated umbilical vein (ductus venosus). Anterior portion is an extension of the falciform ligament. Liver: umbilical fissure --> umbilicus.

    Coronary and triangular ligaments: liver --> diaphragm: inferior surface. Bare area* of the liver is delineated by the coronary ligament centrally (anteriorly and posteriorly) and the right and left triangular ligaments laterally.

    * Bare area of liver: the cranial aspect of the liver is a convex area along the diaphragmatic surface. It is devoid of any ligamentous attachments or peritoneum. This bare area of the liver is attached to the diaphragm by flimsy fibroareolar tissue.

    Phrenicocolic ligament: left lateral extension of the root of the transverse mesocolon. Diaphragm: opposite left r10 & r11 --> Transverse-descending colon: left (splenic) colic flexure. Passes below the spleen acting as a suspensory ligament of the spleen.

    Duodenocolic ligament: right colon --> duodenum.

    Omentum

    Lesser omentum

    Liver: potra hepatis and fossa for the ductus venosus --> stomach: lesser curvature (hepatogastric ligament) and duodenum: D1 (heaptoduodenal ligament).

    From the liver attachment at the ductus venosus this connective tissue ascends to the diaphragm where it attaches to the oesophagus.

    The lesser omentum is often defined to encompass a variety of structures:

    • Hepatogastric ligament.
    • Hepatoduodenal ligament.
    • Hepatophrenic ligament.
    • Hepatoesophageal ligament.
    • Hepatocolic ligament.

    Greater omentum

    Greater curvature of the stomach (right border: D1) -->  descend in front of the small intestines --> ascend to, and encloses, the transverse colon.

    The left side of the greater omentum is continuous with the gastrosplenic ligament.

    The greater omentum is often defined to encompass a variety of structures:

    • Gastrocolic ligament: occasionally considered synonymous with the greater omentum.
    • Phrenicosplenic ligament.
    • Gastrophrenic ligament.
    • Gastrosplenic (gastrolienal) ligament.
    • Splenorenal (lienorenal) ligament: occasionally considered part of the greater omentum.

    The phrenicosplenic, gastrophrenic, gastrosplenic and splenorenal (lienorenal) ligaments are all part of the same mesenteric sheet making the divisions between them fairly arbituary.

    Mesenteries

    The mesenteries are a double fold of peritoneum that attaches the intestines to the posterior abdominal wall. The mesenteries are classified as the mesentery of the small intestine (the mesentery proper) and the mesentery of the large intestine (the mescolon).

    Mesentery of the small intestine (mesentery) proper

    The mesentery of the small intestine is a large and broad fan-shaped mesentery. It extends from the D/J junction (just to the left of L2) to the I/C junction (anterior to the right SIJ) and then attaches to the posterior abdominal wall. 

    Mesentery of the large intestine (mesocolon)

    • Mesoappendix: appendix --> back of the lower end of the mesentery close to the I/C junction.
    • Transverse mesocolon: transverse colon --> posterior abdominal wall. Connects to the pancreas, duodenum and greater omentum.
    • Sigmoid mesocolon: sigmoid colon --> pelvic wall. Forms an inverted 'V' attachment. The apex of the 'V' is at the level of the division of the left common iliac artery (anterior to the left sacroiliac joint). The base of the right limb descends to the median plane at the level of S3. The left limb descends on the medial side of the left psoas major.

    Sometimes the ascending and descending colon is attached to the posterior abdominal wall by the ascending and descending mesocolon. However, it is more common for the peritoneum to only cover the front and sides of the ascending and descending colon.

    Coffey et al (2015) highlighted the continuity of the mesentery from the D/J junction to the distal mesorectum. These authors describes the root of the mesentery where the superior mesenteric artery originates from the pancreatic bed (retroperitoneal space the pancreas and D1 shares). From this location, the mesentery fans out to span the entire gastrointestinal tract from the D/J junction to a termination at the distal mesorectum. Where the mesentery is apposed to the retroperitoneum, its surface area is limited. However, as it attaches on to the gastrointestinal tract, it elongates considerably. They describe approximately 6 feet of elongated mesentery is compactly plicated into the abdominal cavity and tightly packaged in a spiral confirmation the attachments of which parallel the work of Leonardo da Vinci.

    As well as Coffey et al (2015) finding the root of the mesentery to originate at the superior mesenteric artery Martin (1942) also found the anterior renal fascia to cover the mass of connective tissue surrounding the origins superior mesenteric artery.

    Renal fascia 

    The retroperitoneal connective tissue is divided into three layers:

    • Outer layer: transversalis fascia.
    • Intermediate layer: these tissues are locally condensed or specialized forming the fascia for the kidneys (renal fascia), adrenals, kidneys, ureters, and the vessels and nerves.
    • Inner layer: peritoneum.

    As this is retroperitoneal tissue obviously all the layers will be behind (superficial) to the peritoneum.

    The renal fascia is divided into the:

    • Anterior renal fascia (Gerota fascia or fascia of Tobdt).
    • Posterior renal fascia (Zuckcnkandl fascia).

    The anterior renal fascia as a single lamina is thinner than the posterior renal fascia which is a double lamina (Bechtold et al 1996). Stecco et al (2017) described the renal fascia as a zone of dense endoabdominal fascia.

    These two fascia encompass the kidney to form an inverted cone of tissue that lies lateral to the lumbar spine and extends into the pelvis.

    Septa connect the anterior and posterior renal fascia as well as the renal capsule with the renal fascia.

    The boundaries of the renal fascia are:

    • Superiorly: fuses with the posterolateral aspect of the hemidiaphragm. The right anterior and posterior renal fascia blends with the right inferior coronary ligament.
    • Posteriorly: quadratus lumborum (transversalis) fascia. Martin (1942) removed a block of tissue from r11 and r12 to the iliac crest attaching anteriorly to the quadratus lumborum muscle. When this tissue was removed followed by the quadratus lumborum muscle the posterior layer of the renal fascia was exposed.
    • Medially: at the renal hilar level, and caudally from this level, the renal fascia fuses with the lateral margin of the quadratus lumborum (transversalis) fascia.

    Martin (1942) found medially the anterior renal fascia splits into a superficial and deep laminae. Superficial layer: up to the origin of the superior mesenteric artery this layer crosses the midline to form a mass of connective tissue in front of the aorta and inferior vena cava. Here it blends with the anterior renal fascia from the opposite kidney. Above the level of the superior mesenteric artery the anterior renal fascia covers the mass of connective tissue surrounding the origins of the coeliac axis and superior mesenteric artery (in which lie the coeliac and superior mesenteric autonomic plexuses). Deep layer: passes backwards around the medial border of the kidney becoming firmly adherent to the front of the renal hilum and then continues to join the posterior renal fascia.

    As well as Martin (1942) finding the anterior renal fascia to cover the mass of connective tissue surrounding the origins of the coeliac axis and superior mesenteric artery Coffey et al (2015) found the root of the mesentery to start also at the superior mesenteric artery.

    The posterior renal fascia splits at the medial boarder of the kidney. One layer turns into the hilum of the kidney and becomes firmly attached to the posterior aspect of the the ureter. The second layer blends with the psoas major (transversalis) fascia especially at the medial and lateral edges of the psoas.

    • Laterally: the posterior renal fascia blends with the anterior renal fascia forming the lateralconal fascia. Martin (1942) found the renal fascia also fuses laterally with the transversalis fascia.
    • Inferiorly: the posterior and anterior renal fascia gradually converges, but does not fuse, towards a point about 8 cm inferior to the lower pole of the kidney (Bechtold et al 1996). The perirenal space blends loosely with the iliac fascia and periureteric connective tissue.

    References

    Transversalis, endoabdominal, endothoracic fascia: who's who? (2006). Skandalakis PN, Zoras O, Skandalakis JE, Mirilas P.

    A description of the planes of fascia of the human body, with special reference to the fascia of the abdomen, pelvis and perineum (1931). Gallaudet B

    Intertransversalis fascia approach in urologic laparoscopic operations (2012). Li G, Qian YBai HSong ZHong BJia JShi BZhang X.

    THE PELVIC FLOOR—CONSIDERATIONS REGARDING ITS ANATOMY AND MECHANICS (1927). A. W. Meyer

    ABDOMINOPELVIC FASCIAE (1950). MARK A. HAYES

    The phrenic-esophageal ligament: an anatomical study (2008). Apaydinal N, Uz A, Evirgen O, Loukas M, Tubbs RS, Elhan A

    A NOTE ON THE RENAL FASCIA (1942)  BY C. P. MARTIN 

    The Perirenal Space: Relationship of Pathologic Processes to Normal Retroperitoneal Anatomy (1996). Robert E. Bechtold, Raymond B. Dye, Ronaldj Zagoria, Michael YM. Chen

    Microscopic anatomy of the visceral fasciae (2017). Carla Stecco, Maria Martina Sfriso, Andrea Porzionato, Anna Rambaldo, Giovanna Albertin, Veronica Macchi, Raffaele De Caro.

    Mesenteric-Based Surgery Exploits Gastrointestinal, Peritoneal, Mesenteric and Fascial Continuity from Duodenojejunal Flexure to the Anorectal Junction. A Review (2015). J. Calvin Coffey, Mary E. Dillon, Rishabh Sehgal, Peter Dockery, Fabio Quondamatteo, Dara Walsh, Leon Walsh