Thorax IV Flashcards
The Cardiac Skeleton (attachment of the valves)
Collection of dense, fibrous tissue in the form of four rings which interconnect in a plane between the atria and ventricles
Purpose of cardiac skeleton
- Surround the AV orifices, aortic orifice and opening of pulmonary trunk
- Helps maintain integrity of openings and provides attachments for cusps
- Separates muscular wall of atria from ventricles, as well as electrically isolating the ventricles
What is the single connection between these two groups of myocardium
The AV bundle
The Cardiac Skeleton II
Papillary Muscles
- Muscles located in ventricles of the heart.
- Attach to the cusps of the atrioventricular valves (also known as the mitral and tricuspid valves) via the chordae tendineae
- Contract to prevent inversion or prolapse of these valves on ventricular contraction (systole)
Tricuspid Valve (papillary muscles/cusps)
How many papillary muscles in Tricuspid Valve
3 papillary muscles in right ventricle
Anterior: largest
Posterior: may consist of 1-3 structures
Septal: inconsistent (small or absent)
Septomarginal trabecula (moderator band)
- Bridge between lower ventricular (interventricular) septum and base of anterior papillary muscle
- Carries a portion of the cardiac conduction system to anterior wall of right ventricle
The mitrial valve
No Septal papillary
The Semilunar Valves
Major Arteries of the Thorax: Aorta
1 . Ascending Aorta remains within the ______ ___
- Arch of Aorta:
- Lies behind the ______ _______, in front of ______. It arches ______ and backwards. It becomes ________ with descending aorta at level of _____ angle - Aortic arch branches:
- ________ _______(divides into right _____ and right common ____)
- Left common ______
- Left _______
- Ascending Aorta remains within the pericardial sac
- Arch of Aorta:
- Lies behind the manubrium sternum, in front of Trachea. It arches upwards and backwards. It becomes continuous with descending aorta at level of sternal angle - Aortic arch branches:
- Brachiocephalic trunk (divides into right subclavian and right common carotid)
- Left common carotid
- Left subclavian
Mediastinum
Aortic Arch Branches
Features of the Descending Thoracic Aorta
- Begins at about T4-T5 from the arch of the aorta
- Descends in the posterior mediastinum
- Passes through the aortic hiatus of the diaphragm at T12
Descending Thoracic Aorta
Q: Why is it important that the Descending Thoracic Aorta passes through the aortic hiatus of the diaphragm at T12?
So that we don’t get compression of aorta by contraction of diaphragm
Descending Thoracic Aorta: Posterior Intercostal Arteries
Brachiocephalic
The Vena Cavae
All the body’s systemic veins (except cardiac) ultimately drain into either the superior vena cava (SVC) or inferior vena cava (IVC)
The superior vena cava receives blood from…
The head, neck, chest, shoulders and upper limbs
The inferior vena cava collects…
most of the venous blood from organs inferior to the diaphragm (execption Azygous Vein*)
*drains posterior abdominal & thoracic wall eventually into SVC
The azygous system of veins provides an alternative route for….
venous return back to the heart via the superior vena cava in cases where the inferior vena cava is damaged
The Azygous Vein
The Hemiazygos vein
The Lymphatic System
- made up of lymphatic tissues & lymphatic vessels
- the lymphatic system is essentially a drainage system, and there is no circulation
Lymphatic tissues
- Contain large numbers of lymphocytes e.g. the thymus, the spleen
- Essential for the immunologic defences
Lymphatic vessels
- Tubes that assist the cardiovascular system in tissue fluid removal from the tissue spaces of the body.
- The vessels then return the fluid to the blood
Before lymph is returned to the bloodstream…
…it passes through at least one lymph node.
Lymph nodes:
- are a congregation of immune cells
- filter lymph
Lymphatic Drainage of the Thorax
The link between Lymph System and CVS system:
Thoracic Duct
- Major lymphatic vessel in the body (runs right up through the posterior mediastinum)
- Starts at cisterna chyli (a dilated sac at the lower end of the thoracic duct)
- Passes behind the arch of the aorta to enter the left brachiocephalic vein
Right Lymphatic Duct and Thoracic Duct
Thoracic Duct (larger duct) is draining everything except that which is in black
Divisions of the Nervous System
The enteric division
The enteric nervous system (or intrinsic nervous system) is embedded in the lining of the gastrointestinal system. consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract e.g bowel peristalsis
Sympathetic division is active during ….
Parasympathetic division active under….
Sympathetic division is active during periods of exertion, stress or emergency (“Fight or Flight”)
Parasympathetic division active under resting conditions (“Rest and Digest”)
The Sympathetic Nervous System (described as Thoracolumbar outflow)
DETAILED
The areas of grey matter in thoracic and lumbar region have an additional horns in them called the lateral horns of grey matter - it is from this we that we have our sypathetic outflow.
! If a cross section of the spinal cord is taken out and they don’t have a lateral horn = not thoracic or lumbar region !
Some of these neurons will pass out from lateral horn of grey matter and will synapse in ganglia which are running lateral each side of vetebral column (paravertebral ganglia)
Some neurons pass out and move up or down the chain and synapse in ganglia closer to their target. Movement of neurones up and down creates a sympathetic chain
The Sympathetic Nervous System (summarised)
- Preganglionic sympathetic outflow from spinal cord segments T1-L2
- Thoracolumbar outflow
- Some of these neurons synapse in paravertebral ganglia located on each side of the vertebral column, which are connected
- Sympathetic chains
Sympathetic Chain: pre- and post-ganglionic
Later on the sympathetic neurone passes white ramus communicans, if it synapses at paravertebral ganglia, it passes back out via grey ramus communicans into the spinal nerve
Preganglionic fibres are ____ and synapse with roughly __ postganglionic neurons
Facilitates _______ and a more ______ response to e.g increase cardiac output or respiration
Preganglionic fibres are short and synapse with roughly 30 postganglionic neurons
Facilitates divergence and a more widespread response o e.g increase cardiac output or respiration
Postganglionic fibres leave ganglia to..
Thoracic Splanchnic Nerves
…innervate visceral tissues and organs within abdominopelvic cavity
Thoracic Splanchnic Nerves
They synapse in …
Thoracic Splanchnic Nerves
…separate prevertebral ganglia (located around the blood vessels of the aorta)
Thoracic Splanchnic Nerves
Preganglionic fibres pass through the sympathetic chain without ______
Thoracic Splanchnic Nerves
Preganglionic fibres pass through the sympathetic chain without synapsing
Thoracic Splanchnic Nerves
The lower 8 ganglia of the sympathetic chain mainly give pre-ganglionic fibres that are…
Thoracic Splanchnic Nerves
..grouped together to form thoracic splanchnic nerves & supply abdominal viscera
Thoracic Splanchnic Nerves
Summary thus far
We have the sympathetic chain running down the posterior thoracic wall, we have ganglia either side of the vertebrae column, and we have nerve fibres that move up and down the vertebral column that form the sympathetic chain.
Thoracic Splanic Nerves don’t synapse in sympathetic chain but pass straight through through and synapse closer to their target organs
A lot of the nerves that pass into the sympathetic chain do synapse, they synapse with many post-ganglionic fibres which head off to target various organs
Greater Splanchnic nerve
Greater Splachnic Nerve
- T5-T9/T10
- Coeliac ganglion - surrounds coeliac artery of abdominal aorta (foregut)
- Supplies Foregut viscera
Lesser Splanchnic nerve
Lesser Splanchnic nerve
- T9-T10 or T10-T11
- Synapse in Aorticorenal ganglion/superior mesenteric ganglion - midgut (close to the renal vasculature coming off the aorta)
- Supplies Midgut viscera
Least Splanchnic nerve
Least Splanchnic nerve
• T12
• Renal ganglion/Aorticorenal ganglion - kidneys
• Supplies kidneys and upper ureter
Although Splanchic nerve function mainly in the abdominal region, their origin is from…
the posterior thoracic wall
Lumbar splanchnic nerves
- Supplies lower part of Gastrointestinal tract
- L1-L2
- Synapse in the inferior mesenteric ganglion - hindgut
SOMATIC NERVES
Phrenic Nerves
- Originate from the cervical plexus (specifically C3, 4 & 5)
- Contains motor, sensory & sympathetic nerve fibers
- Provides the only motor supply to the diaphragm (C3, 4, 5 keeps the diaphragm alive) as well as sensation to the central tendon of diaphragm.
- In the thorax, each phrenic nerve supplies sensation to the mediastinal pleura & pericardium
relation to Phrenic Nerve summary
Sympathetic nerve fibers would have originated in the thoracic region and would move up either side of vertebrae column, synapsing within ganglia up in cervical region, then run with the spinal nerve towards the diaphragm.
Phrenic Nerve Path
- Enters the superior mediastinum lateral to vagus nerve & behind the brachiocephalic veins
- Passes anteriorly to the hilum of the lung and over the pericardium of the heart sending small pericardial branches to it
Vagus Nerve Features
- Cranial Nerve X
- Autonomic control of the heart and digestive tract
- Supplies motor parasympathetic fibers to all the organs except the suprarenal (adrenal) glands, from the neck down to the second segment of the transverse colon
Which few skeletal muscles does the Vagus nerve control?
Controls a few skeletal muscles (movement of pharynx (swallowing)):
- Superior, middle and inferior pharyngeal constrictors
- Muscles of the larynx (Recurrent laryngeal)
Nerve Trunk
A bundle of nerve fibers enclosed in a connective tissue sheath.
In the thorax, vagus nerves form…
Right – posterior vagal trunk
Left – anterior vagal trunk
Vagus nerve branches from the vagal trunks contribute to the formation of the __________ plexus, which innervates the __________________________
Vagus nerve branches from the vagal trunks contribute to the formation of the oesophageal plexus, which innervates the smooth muscle of the oesophagus
Two other branches arise in the thorax, these are:
Vagus Nerve
Left recurrent laryngeal nerve – it hooks under the arch of the aorta, ascending to innervate the majority of the intrinsic muscles of the larynx
Cardiac branches – these innervate regulate heart rate and provide visceral sensation to the organ
Vagus Nerve
