Types of Nerves:

Somatic – innervates

and skeletal muscle

fibres supply skeletal muscle only

Sensory nerves supply sensation from the skin (dominant sensory area), muscles, bones, the parietal pleura + the parietal pericardium.

The main somatic nerves of the thorax are: the intercostal nerves (11 pairs) and the

nerves (1 pair)

Autonomic (also known as

) – innervates organs, viscera, smooth muscle, glands

Motor fibres supple smooth muscle, cardiac muscle and many exocrine glands (e.g. muscle of the heart, blood vessels, bronchi, bronchial + sweat glands)

Sensory fibres supply sensation of various kinds to the

The autonomic nerves can then be sub-divided:

Sympathetic

- Motor nerves to smooth muscle, the cardiac pacemaker + many exocrine glands - Pain sensation to the viscera - NOT limited to the viscera – also supply somatic

muscle (particularly blood vessel walls) and the sweat glands - Chest wall obtains sympathetic supply mainly via thoracic spinal nerves

Thoracic viscera mainly supplied from thoracic spinal nerves T3-T6

Parasympathetic:

- Motor to smooth muscle, the cardiac pacemaker + many exocrine glands - Sensory monitoring feedback from the visceral organs (known as

- Distribution limited to the viscera - Entire supply to the thoracic viscera comes from the brainstem in the

nerves

Thoracic somatic nerves:

The intercostal nerves-

Arise as the main branches of the thoracic somatic spinal nerves

These nerves are often described as

nerves – each pair supplies a single body segment – i.e. each pair form a repeating unit containing a single vertebrae with its associated skeletal muscle and skin

Each segmental spinal nerve forms from roots emerging from the spinal cord: o anterior (ventral) root – all motor fibres o posterior (dorsal) root – all sensory fibres

the cell bodies of the sensory neurones all form a swelling called the

(found on the dorsal root just prior to its join with the ventral root to form the spinal nerve)

the dorsal root ganglion and the junction of the roots lie within the

– a lateral gap between the pedicles of adjoining vertebrae

There is no corresponding motor neurone ganglion, as the cell bodies are within the spinal cord

Each spinal nerve then divides into two unequal-sized

The posterior ramus is

and supplies motor fibres to the column of muscle posterior to the transverse spinal processes (often called the erector spinae complex), and sensory fibres to the skin overlying these muscles

The anterior ramus is larger, and runs anteriorly between the muscle layers, supplying muscle right round to the anterior midline.

Many different spinal nerves may combine to form

suppying specialised areas (e.g. cervical, brachial, lumbosacral)

Dermatome – an area of

which is supplied by a single spinal nerve/spinal cord level

Myotome – part of a

which is supplied by a single spinal nerve/spinal cord level

Thoracic segments:

T1-

T4-

T6-

T10- Navel

T12-

The phrenic nerves:

 Derived from the anterior rami of spinal nerves

Somatic nerves – no autonomic function or visceral distribution

Motor fibres supply the skeletal muscle of the

– the most important inspiratory muscle therefore damage to the motor tracts of the spinal cord at/above the C4 segment disconnects the inspiratory muscles from the respiratory centre in the brainstem (likely to cause death from asphyxia)

Sensory fibres supply the central diaphragm, its pleural covering, mediastinal plerua + pericardium, as well as the peritoneum on the inferior surface of the central diaphragm

Spinal nerves C2-C5 produce several nerves other than the phrenic, though these are of much less importance. Such areas of shared distribution of several pairs of spinal nerves are called plexi – this one is called the

plexus

The phrenic nerves run down the neck on the muscles arising from the cervical transverse processes to enter the thorax.

They then pass on either side of the mediastinum down to the diaphragm

The

phrenic nerve follows the course of the great veins, running successively on the right brachiocephalic vein, the superior vena cava, and the fibrous pericardium covering the sinus venous of the right atrium and inferior vena cava

The left phrenic nerve crosses the arch of the

then rubs across the fibrous pericardium overlying the left ventricle

Diaphragmatic pain – the brain doesn’t have a map of the viscera, so pain from the diaphragm is interpreted as coming from the part of the body surface supplied by C3-C5 – the top of the shoulder and the base of the neck – this is known as

Thoracic autonomic nerves:

In the autonomic nervous system, there are two tiers of motor neurones:

Pre-ganglionic neurones – cell bodies in the spinal cord/brain with axons that fun to swellings on the nerves called

In these ganglia, the pre-ganglionic axons synapse with the much more numerous post-ganglionic neurones

Post-ganglionic neurones – axons run to target (cardiac muscle, smooth muscle, glands)

This two-stage arrangement greatly reduces the number of cell bodies needing space within the CNS, though it reduces the precision of successful targeting of specific nerves

Autonomic nerves are divided into parasympathetic and sympathetic divisions; each of which has different origins and distributions, and are often (NOT always) opposite in motor effects

Sympathetic nerves:

All the sympathetic ganglionic neurones of the body live in the spinal cord between

but the axons have to reach virtually all parts of the body (except the CNS itself)

Sympathetic motor fibres mainly travel with the

motor fibres. However their autonomic ganglia (containing the synpases between pre + post) need to be accommodated somewhere.

The fibres come out in the spinal nerve like somatic motor fibres, but then briefly leave the nerve in a slender bundle to form a

ganglion on the side of the vertebrae (thus each spinal nerve pair will -> ganglion on either side of the vertebra)

At the paravertebral ganglion, the pre-synaptic fibres synapse with the post-synaptic fibres, and then the slender bundle of post-synaptic fibres return to the spinal nerve to be distributed.

These slender bundle of nerves which join the sympathetic ganglia to the spinal nerves are called

The pre-ganglionic fibres are wrapped in myelin so form a

ramus commincans

The post-ganglionic fibres are unmyelinated so form a

ramus communicans

Why do we need lymphatics?

More fluid leaves blood capillaries than returns to them so we need a way of clearing the excess fluid or we'd get

Ensure foreign particles come into contact with the immune system

Disease (e.g. cancer) can spread via the lymphatics so you need to understand the direction of lymphatic flow

What is the lymphatic system?

Network of tissues and organs consisting of lymph vessels, lymph nodes and lymph

Includes tonsils, adenoids , spleen and thymus

There are around 600-700

in humans

Lymph nodes filter the lymph before it returns to the circulatory system Removing lymph nodes increases the likelihood of developing oedema

Overview of the Lymphatic System

Lymphatics drains the entire body except the

The main lymphatic vessel is the

Nearly all of the body drains via the thoracic duct

The upper right quadrant is drained separately to the rest of the body

The upper right quadrant drains into the right

vein

The rest of the body is drained via the thoracic duct into the

subclavian vein

Capillary beds leak out fluid which then gets collected by the blind-ended lymphatic capillaries

The lymphatic vessels keep getting

as you get closer to the point at which lymph returns to the circulation

There are valves in the lymphatic vessels because there is no

associated with the lymphatic system

Around the bifurcation of the trachea you find the largest collection of lymph nodes in the body

Enlargement of lymph nodes around the trachea can alter the subcarinal angle Lymph vessels join together to form lymphatic trunks

Anatomy of a Lymph Node:

Small (<2.5 cm long)

Found along lymph vessels

Contain lymphocytes and macrophages

Drainage from infected regions detectable in enlarged lymph nodes

Lymph nodes are palpable in the armpit, groin and

Enlarged lymph nodes (lymphadenopathy) are indicative of

Lymph:

Clear and odourless in most vessels

Lymph in

is opaque and milky due to the fats absorbed

Intestinal lymph is called

Lymph contains: White blood cells Pathogens Hormones Cell debris Fats

Movement of Lymph:

Slow and sporadic because there is no pump

Movement is maintained by the action of adjacent structures: Skeletal muscles and the pulses in arteries

due to the presence of valves

Lymphatics of the Thoracic Wall

Lymph from the thoracic wall drains into nodes associated with:

Internal thoracic arteries-

Ribs- intercostal and diaphragm- diaphragmatic

Anterior intercostal arteries from the internal thoracic arteries

Anterior parts of the thoracic wall will drain into the

nodes

The intercostal nodes are located around the back near the vertebral column

The thoracic duct travels up from the right side of the body, crosses to the left, remains behind the great veins and then comes forward and drops into the

between the left internal jugular vein and the left subclavian vein

The anterior chest wall drains into the parasternal nodes which travel superiorly to the

trunks (there is one on the left and one on the right)

The bronchomediastinal trunks may join the right lymphatic duct or the thoracic duct but usually they open independently into the junction of the internal jugular and the subclavian vein on their own side

The upper part of the intercostal lymphatics will drain via the bronchomediastinal trunks and the inferior part will drain into the

The cisterna chyli is just below the diaphragm - it is significantly larger than the thoracic duct and it collects fluid from the lower limbs

The diaphragmatic lymph nodes drain into the aortic/lumbar area of the

Superficial lymph vessels drain via the axillary or parasternal nodes

SUMMARY: Parasternal = bronchomediastinal trunks Intercostal (upper) = bronchomediastinal trunks Intercostal (lower) = thoracic duct Diaphragmatic = brachiocephalic + aortic/lumbar area of thoracic duct Superficial = axillary or parasternal

The Thoracic Duct:

Main channel draining most of the body (everything except the upper right quadrant)

Begins at the

which drains the abdomen, pelvis, perineum and lower limbs

Thoracic duct begins at vertebral level

Enters behind the oesophagus as it goes through the diaphragm (at T10)

Ascends on

of midline (between aorta and azygos vein)

Crosses over to the left side at

Empties into the left subclavian vein

The veins going along the ribs at the back are the right and left posterior intercostal veins The azygos vein joins into the back of the

Lymphatics of the Lungs

The largest collection of lymph nodes in the body are the

lymph nodes which sit just under the bifurcation of the trachea

They are found around the trachea and the bronchi

They are within the lungs, inside the visceral pleura and through the hilum

Tracheo-bronchial lymph vessels unite with vessels from parasternal and brachiocephalic nodes anterior to brachiocephalic veins to form:

left and right bronchomediastinal

Lymphatics of the heart:

Lymphatics in the heart follow the coronary arteries and drain into the brachiocephalic and tracheobronchial vessels

Lymphatics of the Posterior Mediastinum:

Nodes on the aorta receive lymph from the oesophagus, diaphragm, liver and pericardium and drain into the:

Thoracic Duct Posterior mediastinal

In the posterior mediastinum, there is a collection of lymph nodes associated with the

The intercostal nodes are also sometimes called the para-aortic nodes

You need to know the direction of travel of the lymphatics because a primary tumour in any organ could travel via the lymphatics and form secondaries elsewhere

There are

thoracic vertebrae. 12 pairs of ribs and costal cartilages.

The ribs

reach the sternum and are called true ribs

reach costal cartilage above but don't attach to sternum and

are lacking anterior attachment

Articulations are

The neck is a short flat region of bone that separates the head from the

This projects posteriorly from the junction of the neck with the shaft and consists of two parts: An articular and non-articular part

The articular part is

and has an oval facet for articulation with a corresponding facet on the transverse process of the associated vertebra

the raised nonarticular part is roughened by

The shaft is generally thin and flat with internal and external surfaces. The superior margin is

than the inferior margin. The shaft bends forward just laterally to the tubercle at a site termed the

It also has a gentle twist around its longitudinal axis so that the external surface of the anterior part of the shaft faces somewhat superiorly. The inferior margin of the internal surface is called the

Because ribs slope downwards,

is on the same plane as the sternal angle

The thoracic inlet is a ring formed of: the first thoracic vertebra, first

Its contents include: Great vessels heading to the upper neck and upper limb, oesophagus, trachea, nerves and lymphatic

The space between adjacent ribs is the

Intercostal muscles are found

The external intercostals- They are

and laterally from the low border of rib above to rib below. They're replaced by anterior intercostal membrane at the

(rib-cartilage) junction.

Internal intercostals- Attachments begin anteriorly at the

from lower border of rib above to rib below- fibres are directed at

to external intercostals. They're replaced by membrane posteriorly

The axilla is the

Intercostal-neuromuscular junction:

Each intercostal artery joins (anastomoses) with a major artery at each end of the intercostal space.

Intercostal nerves and associated major arteries and veins lie in the

along the inferior margin of the superior rib and pass in the plane between the inner two layers of muscles

In each space the

is the most superior structure and therefore the highest in the costal groove. The artery is inferior to the vein and the nerve is inferior to artery. Therefore the

is the structure that is most at risk when objects perforate the upper aspect of an intercostal space

Deep to the intercostal spaces and ribs, and separating these structures from the underlying pleura is a layer of loose connective tissue called

which contains variable amounts of fat. Superficial to the spaces are deep fascia and skin.

Sternum:

First costal cartilages attach to the

2nd to the

to the sternum

8th-10th to cartilage above

and the 11th-12th are

The top of the sternum is the

and the bottom is the

Intercostal nerves- there are

pairs of intercostal nerves plus one sub costal (underneath the 12th rib)

They come from the

and supply the costal muscles

The contents of the thoracic cavity:

Space between the pleural cavities-

which contains the heart, great vessels, oesophagus, trachea, thymus, thoracic duct, lymph nodes and phrenic and vagus nerves

Thoracic vertebrae:

Characterised by articulation with ribs, a typical thoracic vertebrae has 2

facets (superior and inferior costal facets) on each side of the vertebral body for articulation with the head of its own rib and the one below

The

costal facet is the larger of the two

Each traverse process also has a facet- the transverse costal facet for articulation with the

of its own rib

The vertebral body of the vertebra is heart shaped and the vertebral foramen is

Lumbar vertebrae:

Distinguished from other vertebrae by their

Also they lack facets for articulation with ribs. Their transverse process is generally long and

with the exception of lumbar vertebrae which are massive and cone shaped for the attachment of

ligaments to connect the transverse process to the

The vertebral body is cylindrical and the vertebra foramen is triangular in shape and

than thoracic vertebrae

Each vertebrae has a vertebral body which is the region of load bearing. There is also a hole in the middle called the

that collectively form the vertebral canal to encase the

In addition there is usually a

which extends posteriorly and inferiorly away from the body and is involved in helping create the foramen and being a site of attachment for ligaments and muscles

Bony pillars that attach the vertebral body to the vertebral arch are

Flattened sheets of bone that extend from the pedicle to meet medially and form the superior surface of the vertebral arch are

Transverse processes are small fused rib elements that extend posterolaterally from the junction of the pedicle and lamina on each side and is a site for articulation with ribs in the thoracic region.

There are also superior and inferior articular processes which are formed from the joining of the lamina to the pedicles.

Cervical vertebrae:

Characterised by

and foramen present in every transverse process

Vertebral body is short in height and

shaped. It has a concave superior surface and a convex inferior surface.

Each transverse process is trough shaped and perforated by a round foramen transversarium.

The spinous process is short and

The vertebral foramen is

Atlas and axis (CIandCII) have no

The sacrum is a collection of

fused bones which has 4 anterior sacral foramina which allow the passage of the spinal nerves S1-S4 to leave.

It is triangular in shape with apex pointed inferiorly and is curved so that it has a concave anterior surface and convex posterior surface.

Two large L-shaped facets for articulation with

Female breast base extends from the

to

rib in the midclavicular line. It overlies the pectoralis major

Laterally, it extends to lie on

anterior and external oblique muscles

An axillary tail of breast tissue sometimes extends into the medial wall of the

and lies in the subcutaneous fat

The medial and lateral extents depending on the size of the breast from the midline (medially) to the axillary line (laterally)

The breast is a modified

Under hormonal influence it can produce milk post-partum It is made up of: glandular tissue, fat and fibrous tissue

Radiology Terminology:

Black:

White:

The breast consists of

ductal lobular units each draining into a main duct

There is a complex network behind the nipple

There are between 4-18 milk ducts open on the summit of the nipple or on the areola

lies interspersed between the ductal lobular units

The organ is divided by fibrous

that radiate from the centre outwards

Mammography:

Young women have more

breasts so it is more radioopaque on a mammogram and hence it is more difficult to identify breast tumours

The breasts are put side by side so you can look for asymmetry

You look at the breast in 2 views: Cranio-Caudal and

In a fatty breast it is easier to see a difference

Breast cancer causes

- it tethers and draws in tissue

You sometimes have to do an extended lateral view because you might miss some of it. Lateral side is at the

Medial side is at the bottom

If they have gynaecomastia then you may be able to see some glandular tissue You tend to do ultrasound scans first with males It is difficult to get much breast tissue between the plates in males

Breast cancer causes microcalcification This abnormal calcification is linear and follows the milk ducts to the nipple

Suspensory Ligaments of Cooper:

The organ is divided by fibrous septae that radiate from the centre outwards (suspensory ligaments of Cooper)

Sometimes you can get indrawing of the skin (tethering) due to the ligaments of Cooper being involved in the tumour process

Blood Supply to the Breast

The blood supply is derived from branches of the: Lateral thoracic artery Internal thoracic artery Thoraco-acromial artery Thoraco-dorsal artery Intercostal arteries

The skin is supplied by the

which communicates with the deep parenchymal vessels

The nipple receives a branch from the

artery. Venous return follows the arteries

There is a rich supply of blood to the breast which is why you can do skin-sparing mastectomy

Sensory Innervation of the Breast:

Sensory innervation is dermatomal, mainly from the anterolateral and anteromedial branches of thoracic intercostal nerves

There is also innervation from the

nerves to the upper and lateral parts of the breast The nipple has a dominant supply from the lateral cutaneous branch of T4

Breast Ultrasound:

Ultrasound can be used to help biopsy breasts

A benign lump is smooth and

than it is tall in the longitudinal plane - cancers tend to be the opposite

This is a fibroadenoma

Ultrasound can be used to guide a wire into a tumour Dense tissue is very

Glandular tissue is

Breast MRI

Tumour is

Everything else is black

This is the opposite of ultrasound in terms of colour Breast MRI isn't offered to many people because it takes a long time, is a little distressing and is expensive

Lymphatics :

The lymphatic and venous channels play an important role in the spread of breast cancer

Lymphatic drainage from the breast is mostly towards the

If you remove too many lymph nodes in breast surgery, you get oedema in your

You usually just remove the sentinal lymph node - axillary clearance is only performed if absolutely necessary

Before breast surgery, a dye is inserted into the breast and it is observed to see which lymph nodes it spread to

Sentinal Node Imaging :

Lymph capillaries make a richly anastomosing network within the breast and overlying skin

The superficial parts of the breast drain towards the

plexus

The deep parts of the brain drain towards the

plexus that lies in the deep fascia overlying pectoralis major and serratus anterior

Lymph Glands :

From the submammary and subareolar plexuses, lymph from most of the breast drains to the:

group of axillary nodes

But there is drainage of adjacent parts of the breast to: The infraclavicular group Parasternal nodes Mediastinal nodes (inferiorly through the abdominal wall, and diaphragm) To the opposite breast

Because there is rich anastomoses, there are other routes of drainage other than to the axillary nodes

If there is tumour blocking one of the routes or one of the routes has been removed in surgery, you need to know where else it can drain There is free communication between the nodes above and below the

and between the cervical and axillary nodes

Lymphoedema of the arm can occur after surgery (axillary clearance) or radiotherapy to the axilla due to blockage of the lymphatics or as a result of impairment of venous drainage Lymphoedema is associated with a higher risk of infection

Lymphoedema is associated with a higher risk of infection

Congenital Abnormalities: Accessory nipples Accessory breast tissue Underdevelopment or absence of one breast (may coexist with muscle/rib cage anomaly) Poland Syndrome (underdevelopment or absence of the chest muscle (pectoralis) on one side of the body)

Scars : Relaxed skin tension lines Langer's lines Axilla contractures