From StudyingMed

< AEB
Jump to: navigation, search

This learning activity is not yet finished -- we still have to improve it to reach our stringent standards. Please help out!

Class notes

Chest wall

  • Consists of a cage
  • Inlet at the top = thoracic inlet
  • Outlet down below is much wider
  • Inlet is a passageway for the trachea, blood vessels, and oesophagus
    • Bounded by vertebrae, first rib and manubrium of sternum
  • The thoracic outlet is bounded by the diaphragm (musculotendinous membrane)

Thoracic vertebrae

  • Arranged in a curvature, concave towards the front. Curvature becomes pronounced in older women due to fractures. Can cause problems for lung ventilation
  • Has a central canal containing spinal cord and surrounding meninges, and some bones
  • Has a vertebral body anteriorly
  • Spinous process posteriorly, pointing down
  • Transverse processes posterolaterally
  • Inferior vertebral notch protects spinal nerves

Typical thoracic vertebra (lateral view)

  • Weight-bearing body anteriorly
  • Laterally projecting transverse process
  • Downward-pointing spinous process
  • Superior vertebral notch = shallow
  • Inferior vertebral notch is deeper
    • Putting these notches together produces an opening for the spinal nerves to come out
  • Superior and inferior articular processes to articulate with adjacent vertebrae
  • Costocapitular demifacets articulate with the heads of the ribs
    • One rib head meets two demifacets
  • On the TP, the costotubercular facet articulates with the tubercle of the rib.

Thoracic vertebrae: typical and atypical

  • Head of each rib articulates with a pair of demifacets, then the rib curves backwards to have an articulation with the transverse process of the rib of the vertebra of the same number
  • First vertebra = circular, complete superior costocapitular facet; thick, horizontal and prominent spinous process
  • T10-12 have a single costocapitular facet
  • No costotubercular facet on T11, T12

A single rib

  • Superior and inferior articular facets to articulate with vertebrae
    • Between them is a crest of head of rib, where a ligament attaches to invertebral disc
  • Neck
  • Tubercle of head of rib has a nonarticular part (ligament) and an articular part (rib) (articular part is more medial)
  • Underside of the rib has a costal groove to protect the neurovascular elements that run in the intercostal space
  • Posterior angle is where rib changes direction to run forwards

Costal cartilages and sternum

  • When you reach 40-50, your costal cartilages start to ossify
  • Sternum = manubrium, body and xiphoid process
  • Some people have a hole in their xiphoid process
  • Jugular notch = top of manubrium of sternum
  • Manubriosternal angle marks where second rib attaches to the sternum, and marks boundary between superior mediastinum and inferior mediastinum (?)
  • Facet on the top articulates with the clavicle
  • On the side of the manubrium are sites for articulation of rib 1-7
  • Rib 8, 9, 10 articulate with the costal cartilage above them
  • Costal cartilages of rib 11 and 12 don't articulate with anything - they're just little cartilaginous tips on these floating ribs

Costovertebral and costotranverse joints

  • Lateral and medial costotransverse ligaments support the costotransverse joing
  • Radiate ligament supports the costovertebral joint
  • Intra-articular ligament of head of rib
  • Superior costotransverse ligament

Intercostal muscles

  • External intercostal = runs in the way of the external oblique
  • Internal intercostal = runs in the way of the internal oblique
  • Innermost intercostal = runs in the way of the internal intercostal
  • Intercostal neurovascular bundle: V A N from superior to inferior
    • Care of nerve in thoracoscentesis
  • Transversus thoracis attaches the costochondral joint with the sternum
  • Internal thoracic artery and vein runs down laterally and posteriorly to the sternum

Thoracic veins

  • Can be a pathway for spread of breast cancer
  • Internal vertebral venous plexus: prominent venous channels surrounding spinal cord and dural sac in the vertebral canal, and penetrate lumbar vertebral bodies and anastamose all the way around the spinous process and back to the spinous process
    • These venous channels are relatively valveless: blood is free to move in both directions
  • Every time you breathe in and out, pressure can push blood up our down: can spread tumours
  • Azygos system of veins: textbook shows it on the right, but this isn't always the case
    • Connections to all the veins draining intercostal spaces, and across to the left side
  • Note that vein 12 is a subcostal vein
  • Accessory hemiazygos vein (sup) and hemiazygos vein (inf) on the left
  • These drain the chest wall - spread breast cancer
  • The internal vertebral venous plexus also has a connection to this azygos system as well: highway to spread metastases: vertebral mets are common in breast cancer.
    • Extent of plexus: Base of skull --> lumbar vertebrae
  • Azygos vein drains into SVC and also connects to IVC and lumbar veins (so can get colateral venous drainage of lower limb in the case of IVC thrombus

Anterior chest wall muscles

  • Pec major, pec minor
  • Biceps muscles

Muscles of posterior axilla

  • Basic structure is a truncated, lop-sided pyramid
  • Spaces is filled with fat, brachial plexus, axillary vein, axillary artery, lymph nodes
  • Top of the axilla = cervicoaxillary canal
  • Armpit is only the bottom of the axilla
  • Look at the diahgram with the green shape showing axilla boundaries
  • Anterior: pec major, pec minor, subclavius, clavipectoral
  • Lateral wall: intertubercular sulcus (for long head of biceps)
  • Medial wall: upper thoracic wall, serratus anterior muscle
  • Posterior wall: subscapularis, teres major and latissimus dorsi and long head of triceps brachii muscle
  • Floor: skin of armpit, open laterally into arm

Neurovascular components of axilla

  • Axilla narrows laterally toward the intertubercular groove for the long head of biceps

Breast

  • Breast has an axillary tail
    • People may think it's abnormal when it's not
    • Can be a site of breast cancer development (check this as well as the breast)
  • Pigmented region = areola. Central to that is the nipple

Internal structure of the breast

  • Modified sweat gland
  • Glandular lobules with secretory cells. Compare resting and lactating states
  • Ducts run towards the nipple into the lactiferous sinus (space for milk to collect before extrusion from the nipple)
  • Lactiferous ducts run from the lactiferous sinus to the nipple
  • Bulk of the tissue of the breast is fat - they're a lot larger than they need to be to work
  • Cooper's ligaments = strands of CT anchoring the breast tissue to the fascia of the chest wall
  • Retromammary space (bursa) is behind the SC fat for prostheses
  • Note pec major/minor and its fascia behind the breast

Changes in the breast during life

  • See the text about
  • Breasts sag due to Cooper's ligaments losing their tone; the breasts also shrink due to loss of fat

Official notes

Skeleton of the thorax

  • This consists of 12 thoracic vertebrae, 12 ribs and their hyaline costal cartilages and the single sternum. The latter is divided into 3 parts: the manubrium, the body and the xiphoid process.
  • The thorax extends from the upper thoracic aperture (thoracic inlet) above, which consists of the 1st thoracic vertebra, 1st rib, 1st costal cartilage and the manubrium, to the lower thoracic aperture (thoracic outlet) below, which consists of the 12th thoracic vertebra, 12th rib, lower 6 costal cartilages.

Thoracic vertebrae

  • have several important features.
  • Typical thoracic vertebrae are TV2 to 8.
  • Typical thoracic vertebrae have the following features:
    • vertebral body with two costal (demi)facets (superior and inferior). The superior pair of (demi)facets are usually larger and lie anterior to the pedicles. The lower pair are smaller and lie anterior to the vertebral notches.
      • Superior facet of TV X articulates with facet on rib number X while inferior articular facet of TV X articulates with rib number X+1.
    • laminae are short, thick and broad and tend to overlap from above downwards
    • the vertebral foramen is small and circular
    • spinous processes slant downwards
    • superior articular processes are almost flat and face dorsally and a little superolaterally. They articulate with inferior articular processes, which project down from the laminae, with their facets directed forwards and a little inferomedially.
    • transverse processes project posterolaterally and bear near their tips, anterior facing oval facets for articulation with the tubercles of the corresponding number rib.

The ribs

  • There are 12 ribs, of which ribs numbers 3-10 are typical, while ribs 1, 2, 11 and 12 are atypical
  • Ribs 1-7 are connected to the sternum by costal cartilages and are called true ribs. Ribs 8, 9, 10 are connected to the suprajacent costal cartilages as they approach the sternum and are called false ribs. Ribs 11 and 12 are not connected to the sternum at all and are called floating ribs.
  • Typical rib features:
    • shaft with anterior and posterior ends. The anterior or costal end has a depression for its costal cartilage's lateral end. The shaft has an external convexity and is grooved internally near its lower border (the costal groove). The costal groove protects the posterior intercostal vein, posterior intercostal artery and intercostal nerve, in that order from superior to inferior
    • the posterior or vertebral end has a head with two articular facets for the vertebral bodies, separated by an interarticular crest (which will lie adjacent to the intervertebral discs). The lower and larger facet articulates with the vertebra of the same number, while the upper and smaller facet articulates with the suprajacent vertebral body
    • the neck is the flattened part behind the head, which lies anterior to the corresponding number transverse process
    • the tubercle is posterior and external to the junction of the neck and shaft. It is divided into medial articular and lateral non-articular areas. The articular area bears a small oval facet for the corresponding facet on the transverse process of the same number rib.
    • the shaft is bent at a posterior angle, 6cm from the tubercle

The sternum

  • Consists of manubrium, body and xiphoid process
  • The manubrium sterni has a jugular notch, clavicular notches for articulation with the clavicle, facets for the 1st ribs and 2nd ribs. The latter articulate at the manubriosternal joint (a symphysis).
  • The body of the sternum is formed from fusion of 4 sternebra and may possess three variable transverse ridges representing the lines of fusion. On the lateral border there are 4 costal notches for articulation with the 3rd to 6th costal cartilages. The inferior angle has a small facet, which, with the xiphoid process, receives the 7th costal cartilage.
  • The sternal angle (at the manubriosternal joint) lies at the level of the 2nd costal cartilage anteriorly, 4th/5th intervertebral disc posteriorly and 5cm inferiorly to the jugular notch.

Joints of the thorax

  • costovertebral, or more properly called the costocorporeal joint (typical vertebra):
    • between the heads of ribs on the one hand and the superior and inferior articular facets and the intervening intervertebral disc on the other. This is a synovial joint with a double synovial compartment, one for each demifacet separated by an intra-articular ligament which extends from the crest between the costal articular facets to the intervertebral disc.
    • costotransverse: between the facet of the transverse process and the articular facet of the tubercle of the corresponding rib. This is a synovial joint
    • costochondral: between the perichondrium of the rib and the periosteum of the rib
    • chondrosternal joints: between the costal cartilage perichondrium and lateral surface of the sternum

Intercostal muscles

  • external intercostals: found in 11 pairs. They extend forward and downwards from each rib to its inferior neighbour. They are not present anterior to the costal cartilages where they are replaced by the external intercostal membrane. They are active during inspiration and the early part of expiration
  • internal intercostals: also 11 pairs. They pass superiorly and anteriorly from each rib to its suprajacent neighbour. They are not present posterior to the costal angles where they are replaced by an internal intercostal membrane. Interosseus parts are believed to be expiratory, while intercartilaginous parts are thought to be inspiratory.
  • innermost intercostals: often absent, they lie deep to the intercostal vessels and nerve. May be expiratory, but no firm information is available.

Blood supply of the thorax

  • costocervical trunk: highest intercostal As to 1st and 2nd intercostal spaces
  • internal thoracic A and its brs: pericardiacophrenic, anterior intercostal and musculophrenic As
  • brs of thoracic aorta: posterior intercostal and subcostal As

Venous drainage of the thorax

  • superior intercostal Vs draining to brachicephalic Vs
  • anterior intercostal Vs draining to internal thoracic V draining into subclavian V.
  • azygos, hemiazygos and accessory hemiazygos Vs draining from posterior intercostal Vs and finally into SVC

Azygos system of veins

  • Azygos V., hemiazygos V. and accessory hemiazygos V.
    • The latter is often absent from our cadavers
  • The azygos vein drains into the superior vena cava
  • The azygos system receives blood from many sources: posterior intercostal veins, vertebral venous plexuses, oesophageal Vs, bronchial Vs, pericardial Vs, mediastinal Vs.
  • There are important communications between the azygos venous system and the internal vertebral venous plexus, which facilitates the widespread dissemination of carcinomatous metastases from primary sites in the drainage area of the azygos system (e.g. breasts). Thus there are communications between the azygos system and the intracranial veins via the vertebral venous plexus (this plexus being valveless and traverses the diaphragm).

Structure of the axilla

  • The axilla is essentially a truncated pyramid with a concave base formed from axillary fascia and an apex at the cervicoaxillary canal
  • Apex - cervicoaxillary canal, the passageway between the neck and the axilla, is bounded by the 1st rib, clavicle and the superior edge of the scapula. Arteries, veins and nerves traverse this opening.
  • Base - formed by the concave skin, subcutaneous tissue and the deep axillary fascia forming the axillary fossa.
  • Medial wall - formed by the thoracic wall (ribs 1 to 4 and intercostal muscles) and the overlying serratus anterior
  • Lateral wall - narrow bony wall formed by the intertubercular groove of the humerus
  • Anterior wall - anterior axillary fold. Anterior wall is formed by the pectoralis major and minor and the fascia between them.
  • Posterior wall - formed by the scapula and subscapularis. The posterior axillary fold is formed by the latissimus dorsi and teres major.

Note: you need to review the origins and insertions of each of these muscles. These are available here.

The breast

General features

  • Mammary glands are in the subcutaneous tissue overlying the pectoralis major and minor muscles. Two thirds of the bed of the breast is formed by the pectoral fascia overlying the pectoralis major; the other third by the fascia covering the serratus anterior.
  • Between the breast and the pectoral fascia there is a loos CT plane or potential space known as the retromammary space (bursa). This allows the breast some movement on the pectoral fascia.
  • The axillary process or tail of the breast extends along the inferolateral border of the pectoralis major muscle towards the axilla. The mammary gland is firmly attached to the dermis of the overlying skin by the suspensory ligaments of Cooper, which are best developed in the superior part of the gland and help support the mammary gland lobules.
  • There are 15 to 20 lobules of glandular tissue arising from lactiferous ducts. Each duct opens independently on the nipple. Deep to the areola, each duct has a dilated portion known as the lactiferous sinus in which a small droplet of milk accumulates or remains in the nursing mother. The areolae contain numerous sebaceous glands, which enlarge during pregnancy and secrete an oily substance, which provides a protective lubricant for the nipple and areolae.

Arterial supply/venous drainage of breast

  • Medial mammary branches of the perforating branches of the internal thoracic artery (ultimately from the subclavian artery)
  • Lateral thoracic and thoracoacromial arteries from the axillary artery
  • Posterior intercostal arteries (branches of the thoracic aorta in the 2nd, 3rd and 4th interspaces).
  • The venous drainage of the breast is mainly to the axillary vein but there is some drainage to the internal thoracic vein. Note connection with internal vertebral venous plexus (see above).