Wednesday, April 29, 2015

Anterior Triangle of the Neck

Posted by Radiology Madeeasy

Anterior Triangle of the Neck

image

The sternocleidomastoid musc divides the neck into an ant triangle & a post triangle

Boundaries

Anteriorly

ant median line of neck

Posteriorly

ant border of sternocleidomastoid

Superiorly

inf border of mandible & a line drawn from angle of mandible to mastoid process

Inferiorly

the apex of the triangle lies at the manubrium sterni

Subdivision

It is subdivided by the digastric & sup belly of omohyoid into

a. submental

b. digastric

c. carotid

d. muscular triangles

a) Submental Triangle

base

hyoid core

on each side

ant belly of digastric

b) Digastric Triangle

anteroinferiorly

ant belly of digastric

posteroinferiorly

post belly of digastric

superiorly (base)

inf border of mandible

c) Carotid Triangle

anteriorly

sup belly of omohyoid

posteriorly

ant border of sternocleidomastoid

superiorly

post belly of digastric

d) Muscular Triangle

anteriorly

ant median line of neck

posterosuperiorly

sup belly of omohyoid

posteriorinferiorly

ant border of sternocleidomastoid

Roof

The roof is formed by

1. skin

2. fascia

3. platysma

Floor

Triangle

formed by

Submental

mylohyoid muscles

Digastric

1. mylohyoid

2. hyoglossus

Carotid

1. thyrohyoid

2. hyoglossus

3. inf & middle constrictors of pharynx

Muscular

1. sternohyoid

2. sternothyroid

3. thyrohyoid

ie. infrahyoid muscles

Contents

Triangle

Contents

Submental

1. LN

2. veins

Digastric

1. submandibular gld

2. facial art & vein

3. portions of parotid gld

4. ECA

situated more deeply

5. ICA

6. IJV

7. glossopharyngeal n

8. vagus n

Carotid

1. CCA, ECA & ICA (more deeply)

2. branches of ECA

3. IJV & some of its tributaries

4. portions of X, XI & XII cranial n

5. larynx & pharynx

6. int & ext laryngeal n

Muscular

1. thyroid gld

2. trachea & larynx

3. esophagus

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Scalenus Anterior Muscles

Posted by Radiology Madeeasy

Scalenus Anterior Muscles

Scalenus Anterior Muscles

The scalenus anterior is an impt muscle of the lower part of the neck

because of its relations with the impt structures in that region

Origin

from the ant tubercles of the tnvs processes of CV3, 4, 5 & 6

Insertion

The fibres are inserted into

1. scalene tubercle on inner border of 1st rib

2. ridge on upper surface of 1st rib

Innervation

from ventral rami of C4, 5 & 6

Action

1. assists elevating 1st rib

2. when acting from below, it laterally flexes & rotates cervical part of vertebral column

Relations

Anteriorly

Posteriorly

Medially

Laterally

1. prevertebral layer of deep cervical fascia

2. phrenic n

3. supf cervical & suprascapular art

4. IJV & subclavian vein

1. subclavian art

2. brachial plexus

3. cervical dome of pleura

1. vertebral art & v

2. inf thyroid art

3. thyrocervical trunk

4. symp trunk

5. on the left side, thoracic duct

1. roots of brachial plexus

2. subclavian art

3. roots of phrenic n

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Sternocleidomastoid Muscle

Posted by Radiology Madeeasy

Sternocleidomastoid Muscle

image

The sternocleidomastoid is 1 of the 2 large, supf muscles of the neck

Origin

sternal head

· tendinous

· arises from superolat part of front of manubrium sterni

clavicular head

· musculotendinous

· arises from med 1/3 of upper surface of clavicle

Insertion

It is inserted by:

1. a tendon into mastoid process of the temporal bone

2. a thin aponeurosis into lat part of sup nuchal line of occipital bone

Nerve Supply

spinal part of accessory n

motor

ventral rami of C2 & C3

sensory (proprioceptive)

Blood Supply

by branches from occipital artery

Actions

When both muscles contract:

1. extend head at atlanto-occipital jt

2. flex cervical part of vertebral column

When 1 muscle contracts:

1. tilt the head towards the shoulder

2. rotates head so that the face looksupwards on the oppo side

If the head is fixed, the 2 muscles can also act as accessory muscles of inspiration

Relations

Supf

1. skin

2. fascia & platysma

3. ext jugular vein (EJV)

4. great auricular, tnvs cut & med supraclavicular nerves

5. supf cervical LN along EJV

6. parotid gland

Deep

1. carotid sheath & its contents: common & ICA, IJV & vagus n

2. muscles: sternohyoid, sternothyroid, omohyoid, scaleni ant, med & post

levator scapulae, splenius capitis & post belly of digastric

3. besides common carotid art (CCA) & int carotid art (ICA)

there are also

   1. ext carotid art (ECA)

   2. occipital art

   3. subclavian art & suprascapular art

4. besides int jugular vein (IJV), there are also

    1. ant jugular vein

    2. facial vein

    3. lingual vein

5. besides vagus nerve there also:

    1. accessory nerve

    2.cervical plexus

    3. upper part of brachial plexus

    4. phrenic n & ansa cervicalis

6. deep cervical LN

Clinical Notes

1. the sternocleidomastoid divides the neck into ant & post triangles

2. congenital torticollis

3. spasmodic torticollis

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Wednesday, April 22, 2015

Inguinal canal

Posted by Radiology Madeeasy

A 21 year old man has an inguinal hernia and is undergoing a surgical repair. As the surgeons approach the inguinal canal they expose the superficial inguinal ring. Which of the following forms the lateral edge of this structure?

 

 

A.

Inferior epigastric artery

  

B.

Conjoint tendon

  

C.

Rectus abdominis muscle

 

 

D.

External oblique aponeurosis

  

E.

Transversalis fascia

 

The external oblique aponeurosis forms the anterior wall of the inguinal canal and also the lateral edge of the superficial inguinal ring. The rectus abdominis lies posteromedially and the transversalis posterior to this.

 

Inguinal canal

Location

  • Above the inguinal ligament
  • The inguinal canal is 4cm long

Boundaries of the inguinal canal

Floor

  • External oblique aponeurosis
  • Inguinal ligament
  • Lacunar ligament

Roof

  • Internal oblique
  • Transversus abdominis

Anterior wall

External oblique aponeurosis

Posterior wall

  • Transversalis fascia
  • Conjoint tendon

Laterally

  • Internal ring
  • Fibres of internal oblique

Medially

  • External ring
  • Conjoint tendon

Contents

Males

Spermatic cord and ilioinguinal nerve

As it passes through the canal the spermatic cord has 3 coverings:

  • External spermatic fascia from external oblique aponeurosis
  • Cremasteric fascia
  • Internal spermatic fascia

Females

Round ligament of uterus and ilioinguinal nerve

 

Related anatomy of the inguinal region


The boundaries of Hesselbachs triangle are commonly tested and illustrated below:

clip_image004

Image sourced from Wikipedia

 

 

The image below demonstrates the close relationship of the vessels to the lower limb with the inguinal canal. A fact to be borne in mind when repairing hernial defects in this region.

clip_image006

 

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Friday, April 10, 2015

side-view mirror strikes his right shoulder

Posted by Radiology Madeeasy

Question 1
Scenario:
A young man is walking along a road when a car travelling at 30mph (48 km/h)
drives past. The side-view mirror strikes his right shoulder and he sustains an
injury to his humerus.

humerus.

With regards to Image 1.1:
I. Identify the greater tubercle.
II. Identify the lesser tubercle.
III. Identify the anatomical neck of the humerus.
IV. Identify the surgical neck of the humerus.


A radiograph shows a fracture at the site marked on Image 1.1.
V. What nerve is at risk following this type of injury?
VI. What clinical features would be present if the nerve was damaged?
VII. Which nerve runs in the spiral groove of the humerus?
VIII. If a fracture was to injure this nerve, what clinical findings might be
expected?
IX. What muscles attach to the coracoid process, and what nerves innervate
them?
X. At what site is the clavicle most commonly fractured?
XI. In which direction are the resultant fragments displaced? Explain your
answer.

 

Correct answer :

 

humerus

I. The greater tubercle is the larger of the two tubercles and lies lateral to the lesser tubercle when the humerus is in the anatomical position; it projects
lateraltotheacromion.It has threefacets, which provideattachmentfor three
of the rotator cuff tendons (supraspinatus, infraspinatus and teres minor).
II. The lesser tubercle is smaller but still prominent. It is the site of attachment of the fourth rotator cuff tendon (subscapularis).


III. The anatomical neck of the humerus follows the articular margins of the
head of the humerus. The capsule of the shoulder joint is attached to
the anatomical neck, except medially and inferiorly where it attaches to the
surgical neck of the humerus.


IV. The poorly defined surgical neck is at the upper end of the shaft of the
humerus.


V. Fractures through the surgical neck of the humerus are the most
common type of proximal humeral fracture. They are extracapsular and
therefore rarely compromise the blood supply to the head of the humerus.
Fractures of the anatomical neck of the humerus are rare. The axillary
nerve (C5,6) passes immediately behind the surgical neck of the humerus,
where it lies in contact with the bone just below the capsule of the shoulder
joint. Consequently, it is susceptible to injury with fractures of the surgical
neck and with shoulder dislocation.


VI. The axillary nerve is a branch of the posterior cord of the brachial plexus.
It supplies motor innervation to the deltoid and teres minor muscles and
sensory cutaneous supply to the upper lateral arm. Injury to the axillary
nerve may result in the following signs:
• Weakness (and later wasting) of the deltoid muscle, causing a loss of
power during abduction and later ‘flattening’ of the normally rounded
contour of the shoulder.
• Sensory loss on the upper outer aspect of the arm, over the ‘regimental
patch’ area.
The main differential diagnosis of an axillary nerve lesion is a C5 nerve
root lesion. With the latter, the normal function of the suprascapular nerve
(C5,6), which supplies the supraspinatus and infraspinatus muscles, will
also be affected.


VII. The radial nerve (C5–8, T1). The radial nerve is the continuation of the
posterior cord of the brachial plexus. It descends posterior to the axillary
artery and enters the spiral (or radial) groove alongside the profunda
brachii artery and its venae comitantes. It passes between the medial and
long head of the triceps muscle and is in contact with the periosteum of
the humerus in the lower part of the spiral groove.
VIII. In a fracture involving the spiral groove, the radial nerve could be
injured, resulting in sensory and motor disturbances. Sensory impairment would be apparent in the territory supplied by the superficial radial
nerve, but due to overlap of cutaneous innervation only a small area of
anaesthesia would be evident, usually over the dorsum of the hand
between the first and second metacarpal bones. This is therefore the
18 Chapter 2: Limbs and vertebral column answers
autonomous zone and so the best area to test for sensory function of the
radial nerve. Knowledge of where the motor branches leave the radial
nerve can be used to predict the site of the lesion. The motor branches to
the long and medial heads of the triceps leave the radial nerve proximal
to the spiral groove; whereas the branch to the lateral head, and a second
branch to the medial head, are generally given off more distally. Consequently, a fracture involving the spiral groove is likely to affect the lateral
head with relative sparing of the long and medial heads. Elbow extension
is weak rather than lost. Brachioradialis function will also be impaired.
Both wrist and finger drop may be evident due to denervation of the
wrist and long finger extensors, extensor pollicis longus and abductor
pollicis longus. The interphalangeal joints of the fingers can still be
extended due to the retained action of the intrinsic muscles of the hand.


IX. Three muscles attach to the coracoid process. They are the:
• biceps brachii, short head (musculocutaneous nerve);
• coracobrachialis (musculocutaneous nerve);
• pectoralis minor (medial and lateral pectoral nerves).


X. The clavicle is the most commonly fractured bone in the body. The
junction between middle and lateral thirds is most commonly fractured
(~75% of all clavicular fractures) for two reasons: (a) the medial twothirds are circular in cross-section whilst the lateral third is flatter; the
junction between the two regions is comparatively weak and also has no
muscular attachments; (b) the powerful coracoclavicular and costoclavicular ligaments stabilise the lateral and medial third of the clavicle,


respectively, and fractures therefore tend to occur between these points.
XI. The medial fragment of bone is elevated superiorly by the unopposed
action of the sternocleidomastoid muscle. The lateral fragment is
depressed by the weight of the arm. The proximal humerus may be pulled
medially by the action of pectoralis major.

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Saturday, April 4, 2015

JVP

Posted by Radiology Madeeasy

43 year old lady is recovering on the intensive care unit following a Whipples procedure. She has a central venous line in situ. Which of the following will lead to the "y" descent on the waveform trace?

A.Ventricular contraction

B.Emptying of the right atrium

C.Emptying of the right ventricle

D.Opening of the pulmonary valve

E.Cardiac tamponade



3 Upward deflections and 2 downward deflections
Upward deflections


  • a wave = atrial contraction
  • c wave = ventricular contraction
  • v wave = atrial venous filling

Downward deflections


  • x wave = atrium relaxes and tricuspid valve moves down
  • y wave = ventricular filling


The 'y' descent represents the emptying of the atrium and the filling of the right ventricle.


 

Cardiac physiology


  • The heart has four chambers ejecting blood into both low pressure and high pressure systems.
  • The pumps generate pressures of between 0-25mmHg on the right side and 0-120 mmHg on the left.
  • At rest diastole comprises 2/3 of the cardiac cycle.
  • The product of the frequency of heart rate and stroke volume combine to give the cardiac output which is typically 5-6L per minute.

Detailed descriptions of the various waveforms are often not a feature of MRCS A (although they are on the syllabus). However, they are a very popular topic for surgical physiology vivas in the oral examination.

Electrical properties


  • Intrinsic myogenic rhythm within cardiac myocytes means that even the denervated heart is capable of contraction.
  • In the normal situation the cardiac impulse is generated in the sino atrial node in the right atrium and conveyed to the ventricles via the atrioventricular node.
  • The sino atrial node is also capable of spontaneous discharge and in the absence of background vagal tone will typically discharge around 100x per minute. Hence the higher resting heart rate found in cardiac transplant cases. In the SA and AV nodes the resting membrane potential is lower than in surrounding cardiac cells and will slowly depolarise from -70mV to around -50mV at which point an action potential is generated.
  • Differences in the depolarisation slopes between SA and AV nodes help to explain why the SA node will depolarise first. The cells have a refractory period during which they cannot be re-stimulated and this period allows for adequate ventricular filling. In pathological tachycardic states this time period is overridden and inadequate ventricular filling may then occur, cardiac output falls and syncope may ensue.

Parasympathetic fibres project to the heart via the vagus and will release acetylcholine. Sympathetic fibres release nor adrenaline and circulating adrenaline comes from the adrenal medulla. Noradrenaline binds to β 1 receptors in the SA node and increases the rate of pacemaker potential depolarisation.

 

Cardiac cycle








clip_image004


Image sourced from Wikipedia


 



    Mid diastole: AV valves open. Ventricles hold 80% of final volume. Outflow valves shut. Aortic pressure is high.


    Late diastole: Atria contract. Ventricles receive 20% to complete filling. Typical end diastolic volume 130-160ml.


    Early systole: AV valves shut. Ventricular pressure rises. Isovolumetric ventricular contraction. AV Valves bulge into atria (c-wave). Aortic and pulmonary pressure exceeded- blood is ejected. Shortening of ventricles pulls atria downwards and drops intra atrial pressure (x-descent).


    Late systole: Ventricular muscles relax and ventricular pressures drop. Although ventricular pressure drops the aortic pressure remains constant owing to peripheral vascular resistance and elastic property of the aorta. Brief period of retrograde flow that occurs in aortic recoil shuts the aortic valve. Ventricles will contain 60ml end systolic volume. The average stroke volume is 70ml (i.e. Volume ejected).

    Early diastole: All valves are closed. Isovolumetric ventricular relaxation occurs. Pressure wave associated with closure of the aortic valve increases aortic pressure. The pressure dip before this rise can be seen on arterial waveforms and is called the incisura. During systole the atrial pressure increases such that it is now above zero (v- wave). Eventually atrial pressure exceed ventricular pressure and AV valves open - atria empty passively into ventricles and atrial pressure falls (y -descent )

The negative atrial pressures are of clinical importance as they can allow air embolization to occur if the neck veins are exposed to air. This patient positioning is important in head and neck surgery to avoid this occurrence if veins are inadvertently cut, or during CVP line insertion.

Mechanical properties

 


  • Preload = end diastolic volume
  • Afterload = aortic pressure

It is important to understand the principles of Laplace's law in surgery.


  • It states that for hollow organs with a circular cross section, the total circumferential wall tension depends upon the circumference of the wall, multiplied by the thickness of the wall and on the wall tension.
  • The total luminal pressure depends upon the cross sectional area of the lumen and the transmural pressure. Transmural pressure is the internal pressure minus external pressure and at equilibrium the total pressure must counterbalance each other.
  • In terms of cardiac physiology the law explains that the rise in ventricular pressure that occurs during the ejection phase is due to physical change in heart size. It also explains why a dilated diseased heart will have impaired systolic function.

Starlings law


  • Increase in end diastolic volume will produce larger stroke volume.
  • This occurs up to a point beyond which cardiac fibres are excessively stretched and stroke volume will fall once more. It is important for the regulation of cardiac output in cardiac transplant patients who need to increase their cardiac output.

Baroreceptor reflexes


  • Baroreceptors located in aortic arch and carotid sinus.
  • Aortic baroreceptor impulses travel via the vagus and from the carotid via the glossopharyngeal nerve.
  • They are stimulated by arterial stretch.
  • Even at normal blood pressures they are tonically active.
  • Increase in baroreceptor discharge causes:

*Increased parasympathetic discharge to the SA node.
*Decreased sympathetic discharge to ventricular muscle causing decreased contractility and fall in stroke volume.
*Decreased sympathetic discharge to venous system causing increased compliance.
*Decreased peripheral arterial vascular resistance

 

 

Atrial stretch receptors

  • Located in atria at junction between pulmonary veins and vena cava.
  • Stimulated by atrial stretch and are thus low pressure sensors.
  • Increased blood volume will cause increased parasympathetic activity.
  • Very rapid infusion of blood will result in increase in heart rate mediated via atrial receptors: the Bainbridge reflex.
  • Decreases in receptor stimulation results in increased sympathetic activity this will decrease renal blood flow-decreases GFR-decreases urinary sodium excretion-renin secretion by juxtaglomerular apparatus-Increase in angiotensin II.
  • Increased atrial stretch will also result in increased release of atrial natriuretic peptide.
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Monday, March 30, 2015

Pagets disease of the nipple

Posted by Radiology Madeeasy

Pagets disease of the nipple

A 65 year old lady presents with a lesion affecting her right breast. On examination she has a weeping, crusting lesion overling the right nipple, the areolar region is not involved. There is no palpable mass lesion in the breast, there is a palpable axillary lymph node. The patients general practitioner has tried treating the lesion with 1% hydrocortisone cream, with no success. What is the most likely diagnosis?

  

A.

Infection with Staphylococcus aureus

 

 

B.

Pagets disease of the nipple

  

C.

Phyllodes tumour

  

D.

Nipple eczema

  

E.

Basal cell carcinoma

 

A weeping, crusty lesion such as this is most likely to represent Pagets disease of the nipple (especially since the areolar region is spared). Although no mass lesion is palpable, a proportion of patients will still have an underlying invasive malignancy (hence the lymphadenopathy).

 

Pagets disease of the nipple

Pagets disease is an eczematoid change of the nipple associated with an underlying breast malignancy and it is present in 1-2% of patients with breast cancer. In half of these patients, it is associated with an underlying mass lesion and 90% of such patients will have an invasive carcinoma. 30% of patients without a mass lesion will still be found to have an underlying carcinoma. The remainder will have carcinoma in situ.
Pagets disease differs from eczema of the nipple in that it involves the nipple primarily and only latterly spreads to the areolar (the opposite occurs in eczema).
Diagnosis is made by punch biopsy, mammography and ultrasound of the breast.
Treatment will depend on the underlying lesion.

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