Chapter 4 Flashcards
1
Q
Thorax
A
- Upper part of the body cavity
- Separated from the abdomen by the diaphragm
- Protected by the thoracic cage
- Contents: Heart; Great vessels; Lungs; Airways; supporting circulatory and nerve networks
- Thoracic cavity can be split in left and right lungs (pleural spaces and mediastinum)
- Mediastinum is the space between the lungs
2
Q
Chest Wall (Thoracic Cage)
A
- Protection of the thoracic and abdominal contents
- Breathing occurs when the diaphragm contracts and relaxes
- When exertion is required, the diaphragm is assisted by intercostal, arm and neck muscles
- Attachments for the upper limb are located at the Sternoclavicular joint.
- Breast is attached between ribs 2 and 6 (covering the pec major)
- Made up of 12 ribs, 12 vertebrae and the sternum
- Inlet and Outlet
- Narrowest at the top, widest at ribs 7 and 8, narrowin slightly toward the outlet
3
Q
Inlet (Thoracic Cage)
A
- Defined as the first thoracic vertebra posteriorly, first ribs(at the sides) and the superior aspect of the Manubrium Sterni
- Structures that pass through the Inlet: Esophagus; Trachea; Common Carotid and Subclavian Arteries; Jugular and Subclavian Veins; Left and Right Vagus Nerves; Left and Right Phrenic Nerves; Left and Right Sympathetic Trunks
4
Q
Outlet (Thoracic Cage)
A
- Defined as the 12th thoracic vertebrae, the 12th ribs passing onto the 11th ribs and then the Costal Margin
- Structures passing through the outlet: Esophagus; Descending Aorta; Inferior Vena Cava; Left and Right Vagus Nerves; Left and Right Sympathetic Trunks; Thoracic Duct
5
Q
Sternum (Breastbone)
A
- Located at the centre front of the chest; provides anterior attachment for the ribs
- 3 components united by 2 joints: Manubrium; Body; Xiphoid process. 2 joints: manubriosternal; xiphisternal
- Manubrium = stoutest part of the bone, it has a Suprasternal or Jugular Notch, an important medical landmark
- Lateral to this notch are the 2 articular surfaces for the sternoclavicular joints
- Immediately inferior to these are the vertically inclined facets for the first costosternal joints
- (Manubrium) The bone narrows towards the manubriosternal joint
- 2nd rib articulates at this joint with a demifacet on both the manubrium and the upper body of the sternum
- The joint is a fibrocartilaginous joint
- Manubrium joins the body by creating an angle in the anteroposterior plane (Sternal Angle)
- Sternal body has articulations laterally for costal cartilages 3,4,5 and 6
- 7th rib articulates between the body and the xiphoid process in like manner to to the articulation of the second rib
- Xiphoid process is variable, pointed, cartilaginous in the young; located in the subcostal angle
6
Q
Ribs
A
- 12 pairs of ribs; upper 7 are true, lower 5 are false
- True rib: directly attached to to the sternum
- Of the false ribs the 8th, 9th and 10th pairs attach indirectly by the costal cartilage of rib 7
- Ribs 11 and 12 are floating ribs
- The 1st rib os the widest, shortest and flattest; it articulates posteriorly with the body of its own vertebra (T1)
- Its upper surface has a small bumb in the centre, the Scalene Tubercle; the subclavian vein and artery pass in front and behind this tubercle, respectively
- Typical rib has a head, neck, tubercle, shaft and distal end
- Head it pointed and has a demifacet (articulate with the bodies of its own vertebra and the one above)
- Not the case for ribs 1, 11 and 12; T1 has one and a half facets, T2-T9 have two demifacets each, T11 and T12 each have a single facet
- Neck is narrow and round, leads to the tubercle
- Tubercle has 2 parts: articular surface and the non-articular part
- Shaft is flat, featuring the Subcostal Groove, running in the inferior deep surface
- 1/3 of the way around, rib starts to point forward and downward, this juncture is called the angle of the rib
- Distal end is characterised by the attachment of the Costal Cartilage (it attaches to the sternum by means of a synovial joint, the Costosternal joint)
- The head is held in place by anteriorly located Radiate Ligaments
- Deep in the joint is the Intra-Articular Ligament securing the top of the head with the Disc
- Tubercle of the ribs articulates with the articular part of the transverse provess
- This joint is strengthened by a large Medial (Ligament of the Neck) and smaller Lateral Costotransverse Ligaments.
- Also reinforced by Superior Costotransverse Ligament (runs between the neck of the rib and the transverse process above)
7
Q
Insic Muscles of the Rib Cage
A
- External Intercostals (superficial)
- Fibers point down and forward; posterior and lateral parts are muscular; anterior section is Aponeurotic
- Internal Intercostals (middle)
- Fibers point down and posteriorly, the aponeurosis is posterior; lateral and anterior are muscle
- Innermost Intercostals (deep)
- Incomplete layer in 3 parts (anterior, lateral and posterior), joined together by thin aponeuroses and are extremely variable
8
Q
Intercostal Spaces
A
- Spaces between the ribs
- Below 12th rib is called Subcostal Space
- Intercostal Space is located between the internal and innermost layers of muscles
- Contains intercostal vein, artery and nerve nestled in the subcostal groove
9
Q
Intercostal Nerves
A
- 11 pairs of intercostal nerves (T1-T11), they are the Anterior Rami of the spinal nerves
- T1, its major portion helps make up the Brachial Plexus
- Each nerve courses around the intercostal space, sending off a major collateral branch
- Collaterals supply the sensory innervation for the skin and merge with penetrating branches from the Dorsal Rami and the Anterior Cutaneous Nerves
10
Q
Intercostal Arteries
A
- 2 sets of arteries supplying the intercostal spaces: Anterior and Posterior Intercostal Arteries
- Most posterior intercostal arteries arise from the Aorta
- The exceptions are arteries 1 and 2 which arise from Supreme Intercostal Artery
- Anterior intercostal arteries are branches of the Internal Thoracic Artery
- Internal Thoracic is a branch of Subclavian Artery and runs down lateral to the sternum behind costal cartilages, accompanied by its Venae Comitantes
- Bifurcates in the Costal Margin into the Superior Epigastric and Musculophrenic Arteries
- Upper 6 anterior intercostal arteries come off of the internal thoracic, the rest from the Musculophrenic Artery
11
Q
Intercostal Veins (Anterior and Posterior)
A
- Posterior vein runs back in the upper part of the intercostal space
- Veins on the right side of the thorax run back to empty into the Azygos Vein
- Left thorax drains into a series of veins, the Hemiazygos Veins (which drain into the azygos vein)
- Anterior Intercostal Veins drain to the venae comitantes of the internal thoracic artery (which eventually drain into the Brachiocephalic Veins)
12
Q
The Diaphragm
A
- Thin musculotendinous partition separating the contents of the thorax from those of the abdomen
- Passing through the diaphragm are: esophagus; aorta; inferior vena cava; vagi and sympathetic nerves
- Innervated by the Left and Right Phrenic Nerves (C3, 4, 5 - keep the diaphragm alive)
- Has a lumbar, costal and sternal origin
- Lumbar portion is via 2 Crura which arise from the first 3 lumbar vertebrae and form an arch to allow the aorta to pass through
- Lateral to these crura are the Medial and Lateral Arcuate Ligaments (which bridge across 2 posterior abdominal muscles, Quadratus Lumborum & Psoas)
- Costal origin continues from the lateral arcuate ligament along rib 12 and onto the lower 6 costal cartilages (it the passes onto the xyphoid process).
- From this oval origin, the diaphragm rises remarkably to form a left and a right Dome on each side of the thorax
- Right dome rises to a level 1 cm below the right nipple (in the male); fibers insert on the crescent-shaped fibrous Central Tendon
- Upon inspiration the fibers contract, pulling the Central Tendon (dome) downward, flattening the diaphragm and expanding the the vertical diameter of the the thoracic cavity
- Lateral to the dome is the Costodiaphragmatic Recess
13
Q
The Heart
A
- Systemic Circulation: the totality of the vessels serving the organs and tissues of the body except the lungs and the liver
- Portal System, made up of the Portal Vein and its tributaries delivering nutrients from the GI tract to the liver
- Located in the middle mediastinum and is constructed of cardiac muscle and connective tissue
- Has 4 chambers: 2 Atria & 2 Ventricles
- Venous blood enters the right atrium from the superior and inferior venae cavae; it passes through the Tricuspid Valve into the right ventricle
- When that ventricle contracts, it sends blood through the Pulmonary Valve into the Pulmonary Trunk
- Pulmonary trunk bifurcates into the Left and Right Pulmonary Arteries which deliver the blood to the Left and Right Lungs
- Oxygenated blood returns from the lungs in the Pulmonary Veins which empty into the left atrium
- It passes through the Mitral Valve into the left ventricle; when the left ventricle has contracted blood passes by the Aortic Valve and into the aorta
- First part of the aorta is the Arch of the Aorta which has 3 major branches; the first branch Brachiocephalic Artery bifurcates into the Right Common Carotid and Right Subclavian Arteries, supplying the head (and neck) and the right upper limbs respectively; the other 2 branches are the Left Common Carotid and Left Subclavian Arteries
- Aorta continues as the Descending Aorta which passes through the Diaphragm to become the Abdominal Aorta; it then bifurcates into the Left and Right Common Iliac Arteries; these supply the pelvis and lower limbs
14
Q
The Pericardium
A
- 3 layered protective “sac” around the heart
- Subdivided into: Fibrous Pericardium; Serous Pericardium (Parietal layer & Visceral layer)
15
Q
Fibrous Pericardium
A
- Single layer made of dense connective tissue (surrounding the heart and serous pericardia)
- Encases the roots of the Great Vessels
- Base fused with the central tendon of the diaphragm
- Serous Pericardium is fused with the inside of the Fibrous Pericardium
16
Q
Serous Pericardium
A
- Double layered sac
- Parietal Layer is fused with the fibrous pericardium
- Visceral Layer is fused to the myocardium (forms the outer layer of the heart, histologists call it Epicardium)
17
Q
External Features (Anterior Heart)
A
- From the front, the heart has 4 borders, a base and an apex
- Right border: forms a vertical line with the Venae Cavae; largely formed by the Right Atrium
- Inferior border: formed by the Right Ventricle
- Left border: formed by the Left Ventricle & Left Atrial Apendage (Auricle)
- Apex: formed by the tip of the Left Ventricle
- Superior border: part of the base, where roots of the great vessels arise
- Can also see Atrioventricular (A-V) & Interventricular Sulci
18
Q
Posterior (Diaphragmatic) Surface
A
- From the back
- Left border: formed by the Left Ventricle
- Right border: formed by the Right Ventricle & Right Atrium
- Left & Right Atriums are above A-V Sulcus
- Ventricles separated by I-V Sulcus
- Entering left atrium are the Pulmonary Veins
19
Q
The Chambers (Right Atrium)
A
- Formed by the venae cavae
- A muscular compartment, the interatrial septum and the right atrioventricular septum containing Right A-V Orifice
- Venae cavae empty towards each other into a smooth walled section of the atrium
- Crista Terminalis (a ridge): seperates the smooth from the muscular wall, located on the anterior wall of the atrium
- Pectinate Muscles: set of parallel ridges (muscular wall); these run into the Atrial Appendage (right one) or Auricle (vestigial flap) with the left auricle, project forward around the root of the aorta
- Left of the IVC opeinng is the opening for the Coronary (Cardiac) Sinus (vein); drain most of the myocardium
- Interatrial septum has a prominent depression, the Fossa Ovalis
20
Q
Chambers (Right Ventricle)
A
- Wall is much thicker than that of the atrium
- Blood enters via the A-V orifice and passes the tricuspid valve
- When the ventricle contracts, the valve closes and blood rushes up the smooth Infundibulum and passes the Pulmonary Valve and into the Pulmonary Trunk
- Chordae Tendinae: prevents evaginating of the 3 flaps of the tricuspid valve into the atrium (chords)
- Papillary Muscles (elongated bands of muscle): hold down and control Chordae Tendinae
- Trabeculae Carnae (ridges of muscle): augment the thickened walls of the ventricle
- Occasionally, a round bundle of muscle fibres links the interventricular septum with the ventricular wall - this is is the Moderator Band
- Septum has 2 parts, lower portion is muscular and the upper part is membranous
21
Q
Chambers (Left Atrium)
A
- Forms the base of the heart
- supplied by a variable number of pulmonary veins (average 2 per side) and naturally feeds the left ventricle
- Thin walled and has an appendage, the left auricle
- Empties into the left ventricle via the left A-V orifice
22
Q
Chambers (Left Ventricle)
A
- Left ventricle wall is 3 times as thick as the right ventricle (because of a much higher pressure in the Systemic Circulation
- Valve only has 2 cusps, Bicuspid or Mitral Valve
- Aortic and Pulmonary Valves are similar in structure, they both have 3 semilunar, sac like cusps which fill upon relaxation of the heart and close onto each other thus preventing regurgitation of the blood; closure is enhanced by the presence of Nodules in the centre of each cusp
23
Q
Pulmonary Trunk and Ascending Aorta
A
- Roots of these Great Vessels lie within the fibrous pericardium, lined with serous pericardium
- Pulmonary Trunk rises straight from the top of the right ventricle, divides into the left and right pulmonary arteries
- Ascending Aorta rises to the right of the pulmonary trunk before it turns backward to become the Arch of the Aorta
- At the root of both the pulmonary trunk and the aorta and three bulges called the Sinuses, each sinus is located above the Cusps of the pulmonary and aortic valves
- Coronary Arteries arise from two of the aortic sinuses
24
Q
Circulation of the Heart (Coronary Arteries)
A
- Right Coronary Artery runs down to the anterior atrioventricular sulcus, then runs backward in the A-V sulcus as far as the posterior I-V sulcus in which it descends as the Posterior Descending Artery
- As it passes around the heart it gives off the Right Marginal Branch (supplies part of the right ventricle wall)
- Left Coronary Artery branches into the Anterior Descending Artery, which runs down the anterior I-V sulcus, and the Left Circumflex Artery which passes behind in the A-V sulcus; these form appropriate anastomoses with each other, giving rise to the so-called Circle and Loop Scheme
25
Q
Circulation of the Heart (Venous Drainage of the Heart)
A
- Great Cardiac Vein goes around the left border, as it passes to the back of the heart it enlarges and becomes the Coronary Sinus which empties into the right atrium
- Sinus is also supplied by Middle Cardiac Vein (runs up the right border of the heart and passes around the back in the A-V sulcus to join the Coronary Sinus just before it enters the right atrium
