Anatomy Of the thorax and circulation Flashcards
What anatomical structures lie behind the sternal angle?
RAT PLANT
Rib 2 Aortic arch Tracheal bifurcation Pulmonary trunk Ligamentum arteriosum Azygos vein Nerves (vagus and sympathetic trunk) Thoracic duct
Where is the Suprasternal (suprajugular) notch?
Superior border of manubrium
Where is the Sternal angle/ Angle of Louis?
Manubriosternal joint (between the manubrium & body of the sternum)
Anterior axillary line
Runs through the lateral quarter point of the clavicle
Sternal line (border)
Lateral margin of sternum
Parasternal line
Between sternal and mid-clavicular lines
Mid-clavicular line
Runs through the mid-point of the clavicle
Midline
Runs centrally down the sternum
Posterior axillary line
Posterior axillary fold
Mid-axillary line
Runs at the mid-point between the anterior & posterior axillary lines
Structures of mediastinum
Superior- above the heart
Inferior - anterior in front of the pericardium
Inferior - middle containing pericardium
Inferior - posterior behind pericardium
Superior mediastinum
Thymus Great vessels Trachea Esophagus Thoracic duct
Structures in middle inferior mediastinum
Heart
Pericardium
Roots of great vessels
Structures in posterior inferior mediastinum
Thoracic aorta
Thoracic duct
Azygous venous system
Thin walled and contain valves
Veins
Thick walled
No valves
Contain baroreceptors & chemoreceptors
Arteries
Layers of blood vessels
Tunica intima
Tunica media
Tunica esterna/Adventia
Tunica intima
INNERMOST layer
Lined by endothelium comprised of simple squamous epithelial cells
Basement membrane and subendothelial connective tissue support overlying cells
Tunica media
INTERMEDIATE , smooth muscular layer
Contain alpha and beta adrenergic receptors, allowing for sympathetic regulation of blood pressure
Tunica externa/adventitia
OUTERMOST layer
Anchors vessels to organs Comprised of type 1 collagen, and elastic connective tissue (in arteries)
Types of arteries
Elastic artery
Muscular artery
Arterioles
Elastic artery
Aorta, pulmonary trunk
Thick tunica media with abundance of elastic fibres
Contain 2 additional layers : internal and external elastic laminae
Muscular artery
Gastro-epiploic artery
More smooth muscle & fewer elastic fibres within intima layer
Most abundant arterial vessel
Arterioles
Vasa recta or large intestines
Smallest division of arterial network
Thin tunica interna
Far fewer muscle fibres
What are Capillaries?
- Smallest vascular structures in the body
- Deliver blood to tissues
• No tunica media or
externa: single layer endothelium plus basement membrane
• Grouped based on the arrangement of the endothelium along the vessel walls
Vessel walls types of capillaries
- Fenestrated
- Continuous
- Discontinuous
Fenestrated capillaries
Capillary beds are perforated along the endothelial cells
Function of Fenestrated capillaries
Facilitates rapid molecular exchange between capillaries and tissues
Example: Bowman’s capsule
Discontinuous (sinusoid also) capillaries
Tortuous, irregular vessels. Incompletely formed/ absent basement membranes underlie widely spaced endothelial cells.
Function of Discontinuous (sinusoidal)
Absence of gap junctions allows for direct transportation from the capillary’s lumen to surrounding tissue
Examples: bone marrow, liver, spleen
Continuous capillaries
Most common type.
Endothelial cells are within close proximity and fitted with gap junctions
Function of capillaries
Isolate luminal content from interstitial space
Examples:
Skin, connective and nervous tissue, muscle
Flow of blood in veins
Capillary»_space; post-capillary veins»_space; venules»_space; veins (small> medium>large)
When compared to similarly sized arteries, veins have?
A thinner tunica media
A wider lumen
A greater abundance (more of them) Valves (except for the venae cava)
Location of Baroreceptors
Carotid sinus
Location of Chemoreceptors
Carotid body
Carotid sinus
Proximal internal carotid artery (near bifurcation of common carotid artery)
Carotid body
At bifurcation
of common carotid artery
Blood supply to head & upper limbs
Arch of aorta
Blood supply to thorax
Thoracic aorta
Blood supply to abdomen & GI
Abdominal aorta
Blood supply to lower limbs and pelvic region
Common iliac arteries
Ascending aorta
From aortic orifice (at base of LV) at the level of 3rd left costal cartilage anteriorly, to 2nd right costal cartilage anteriorly (sternal angle)
Aortic arch
Begins and ends at the level of the 2nd right costal cartilage anteriorly/ T4-T5 vertebral level posteriorly (i.e level of sternal angle).
Occupies the superior mediastinum
Major branch order of the aortic arch
ABC’S
Aortic arch gives rise to:
Brachiocephalic trunk
Left Common carotid artery
Left Subclavian artery
Thoracic aorta runs from?
Arch of aorta ( level TTP) to diaphragm ( vertebral level T12)
Where is the Aortic hiatus ?
T12
Unpaired branches of the thoracic aorta
Bronchial arteries
Pericardial arteries
Esophageal arteries
Mediastinal arteries
Paired branches of the thoracic aorta
Intercostal arteries
Superior phrenic arteries
Which branches of thoracic aorta supply diaphragm?
Superior phrenic arteries
The venous system has two main collecting vessels
Superior vena cava
Inferior vena cava
Superior vena cava
collects from head and upper limbs
Inferior vena cava
collects from abdomen and lower limbs
The RIGHT superior intercostal vein is received by
Azygous vein
The LEFT superior intercostal drains into the
Left brachiocephalic OR the azygos vein.
Right azygous vein arises at which level?
L1-2
Right azygous vein empties at which level?
T4 into the SVC
What are tributaries of azygous vein ?
Right superior intercostal vein, 5th-11th right posterior intercostal veins, the hemiazygos vein, the accessory hemiazygos vein, oesophageal, mediastinal, pericardial and right bronchial veins.
Hemiazygos vein (left) arises where?
Arises at confluence of L ascending lumbar and subcostal veins or from the L renal vein
Hemiazygos vein crossed the midline to enter the azygous run at what level ?
T9
What are the tributaries of the hemiazygos vein?
The lowest 4 or 5 left posterior intercostal veins, oesophageal and mediastinal veins.
At what level does the accessory hemiazygos vein (left) descend at the posterior mediastinum?
T8, where is crosses the midline to drain into the azygos vein or ends in the hemiazygos vein
What are the tributaries of the accessory hemiazygos vein?
4th-8th left posterior intercostal veins, sometimes the left bronchial veins.
The IVC passes through the diaphragm at?
T8
What is the lymphatic system?
A series of organs, vessels and nodes that collect and filter excess tissue fluid (lymph), before returning it to the venous circulation.
Function of lymphatic system
• To drain excess interstitial fluid from tissues into the venous system
• To produce and transport immune cells (lymphocytes)
• To mount an immune response against pathogens
• To transport dietary lipids from the GI tract into the
blood
Lymphatic flow summary
- Fluid leaves the blood capillaries (due to hydrostatic pressure) and enters the interstitial space
- Fluid enters the lymphatic system through lymphatic capillaries within the interstitial space, which unite to form lymphatic vessels
- Lymph flow is slow, one- directional and passes through a series of lymph nodes before draining into lymphatic trunks (collecting vessels)
- These trunks converge to form the right lymphatic duct and thoracic duct, which drain into the venous circulation at the subclavian veins (via the right and left venous angles, respectively)
What structure collects lymph from left upper quadrant & lower half of body?
Thoracic duct - 40 cm long
What structure collects lymph from right upper quadrant of the body → head & neck, upper limb, chest & thoracic cavity?
Right lymphatic duct- short= 1 cm
