Back, Pectoral Region, Breast and Axilla Flashcards
Describe the origin and insertion of pectoralis major.
Origin:
Clavicular head: anterior surface of the medial half of the clavicle
Sternocostal head:
(a) lateral half of the anterior surface of the sternum, up to the 6th costal cartilage
(b) medial parts of 2nd-6th costal cartilages
(c) aponeurosis of the external oblique muscle of the abdomen
Insertion: Lateral lip of intertubercular sulcus
[Diagram]
What are the actions of pectoralis major at the shoulder joint and scapulothoracic joint?
Shoulder joint: arm adduction (sternocostal head), arm internal rotation, arm flexion (clavicular head), extension of flexed arm (sternocostal head)
Scapulothoracic joint: contributes to protraction of the scapula [alt: draws the scapula anteroinferiorly]
What is the anatomical basis of Poland syndrome?
This is an embryonic malformation of the thoracic wall, which is accompanied by a defect on the pectoralis major in combination with other malformations of the upper extremities such as malformation of the fingers. The muscle can be partly or completely missing.
Using landmarks of the bone, explain how you would side a clavicle.
The conoid tubercle is posterolateral.
The groove for subclavius muscle is inferior.
The impression for the costoclavicular ligament is inferomedial.
Viewing the bone anteriorly, the medial two thirds is convex, whereas the lateral one third is concave.
What muscle that covers the shoulder is commonly used for intramuscular injections?
Deltoid muscle
Which ligament attaches clavicle to scapula?
Coracoclavicular ligament
Which ligament anchors clavicle to the first costal cartilage?
Costoclavicular ligament
Name the parts of the clavicle as you appreciate with an atlas or/and the bone itself. (Approximately 8)
- Acromial end and acromial facet
- Sternal end and Sternal facet
- Anterior and posterior sides
- Conoid tubercle for attachment of conoid part (conoid ligament) of coracoclavicular ligament
- Trapezoid line for attachment of trapezoid part (trapezoid ligament) of coracoclavicular ligament
- Subclavian groove for attachment of subclavian muscle
- Impression for costoclavicular ligament
- Nutrient foramen
- [Diagram 1] [Diagram 2]
State the functions of the clavicle. (3)
- It acts as a strut for holding the upper limb far from the trunk so it can move freely.
- It transmits forces from the upper limb to the axial skeleton (sternum).
- It provides an area for the attachment of muscles.
Appreciate peculiarities of the clavicle. (7)
- only long bone that lies horizontally
- no medullary cavity (the medullary cavity is the hollow part of bone that contains bone marrow)
- subcutaneous throughout its extent
- first bone to start ossifying (between the 5th and 6th week of intrauterine life) and last bone to complete its ossification (at 25 years)
- only long bone which ossifies by two primary centers [Diagram]
- only long bone which ossifies via intramembranous ossification except for its medial end
- may be pierced through and through by cutaneous nerve (intermediate supraclavicular nerve)
State the position of the nutrient artery in the clavicle and indicate its importance.
The nutrient foramen is mostly located closer to the sternal end of the clavicle (posterior, middle 1/3). Especially during osteosynthesis of clavicle fractures at the sternal end, maintaining the arterial supply of the clavicle is of great importance for increasing the post-operative life quality of patients.
[Image: nutrient artery of clavicle]
What is the importance of the sternum in clinical practice?
The sternum is a crucial anatomical landmark in clinical practice for a number of procedures, including central venous catheterization, bone marrow biopsy, and chest compressions during cardiopulmonary resuscitation (CPR). It is also a common site for fractures, which can occur due to blunt trauma to the chest.
State the origin and insertion of pectoralis minor.
Origin: it arises from the 3rd, 4th and 5th ribs, near their costal cartilages
Insertion: medial border and upper surface of the coracoid process
[Diagram]
State the nerve supply of pectoralis minor. (and root values too)
medial pectoral nerve
(C8, T1)
State 4 actions of pectoralis minor.
- It assists serratus anterior in drawing the scapula forward (protraction) for punching action.
- Depresses the scapula together with serratus anterior
- Acts as an accessory muscle of respiration during forced inspiration
- Aids in medial or downward rotation of scapula (inferior angle of scapula moves medially; pectoralis minor exerts force on the coracoid process, which pulls the lateral aspect of the scapula inferiorly)
Its subsequent contraction assists gravity in restoring the scapula to the rest position.
The sternal angle is an important landmark in the chest. Elaborate.
- It marks the point at which the costal cartilage of the second rib articulate with the sternum (second sternocostal/sternochondral joint). This is particularly useful when counting ribs to identify landmarks, as rib one is often impalpable.
- It is also used to identify the boundary between the superior and inferior mediastinal cavities.
- It is at the level of the intervertebral disc between thoracic vertebrae 4 and 5.
- This is the superior extent of the heart as well as the inferior end of the trachea when a person is supine.
The clavicle is the most commonly fractured bone in the body. Explain.
Points of reference:
1. Which point is most prone to fractures?
2. What are likely situations that would result in such a fracture?
3. How are the lateral and medial parts of the clavicle likely to be displaced by the muscles attached to them?
4. What would be the clinical presentation of a fractured clavicle?
5. What are three reasons for fracture of the clavicle at the specific point mentioned in number 1?
It commonly fractures at the junction of its lateral one-third and medial two-third due to blows to the shoulder or indirect forces, usually as a result of strong impact on the hand or shoulder, when person falls on the outstretched hand or the shoulder. [X-ray image] [Image: clinical presentation]
When fracture occurs, the lateral fragment is displaced downward by the weight of the upper limb because trapezius alone is unable to support the weight of the upper limb. In addition, the lateral fragment is drawn medially by shoulder adductors viz. teres major, etc. The medial fragment is slightly elevated by the sternocleidomastoid muscle.
The characteristic clinical picture of the patient with a fractured clavicle is that of a man/woman supporting his sagging upper limb with the opposite hand.
The fracture at the junction of lateral one third and medial two-third occurs because:
(a) This is the weakest site.
(b) Two curvatures of clavicle meet at this site.
(c) The transmission of forces (due to impact) from the clavicle to scapula occur at this site through coracoclavicular ligament.
State the origin and insertion of subclavius.
Origin: It arises from the first rib at the costochondral junction.
Insertion: It is inserted into the subclavian groove on the inferior surface of the clavicle.
State the root values of nerve to subclavius.
C5, C6
State the action of subclavius.
~ It depresses the clavicle.
~ It stabilizes the sternoclavicular joint.
Describe the origin and insertion of serratus anterior.
Origin: it arises by a series of 8 digitations from the upper 8 ribs. The first digitation arises from the first and second ribs.
Insertion: It is inserted into the costal surface of the scapula along its medial border. (The first 2 digitations are inserted into the superior angle, next 2 digitations into the medial border and the lower 4 or 5 digitations into the inferior angle of the scapula.)
[Diagram: serratus anterior]
What are the cutaneous nerves of the pectoral region?
~ Supraclavicular nerves (medial, intermediate, and lateral) - supply skin on the front of chest to a horizontal line at the sternal angle
~ Lateral cutaneous branches of intercostal nerves (T3, T4, T5, T6) and anterior cutaneous branches of intercostal nerve (T2, T3, T4, T5, T6)
[Diagram]
Pain arising from the diaphragm can be felt over the shoulder region. Account for this fact.
Referred pain. The diaphragm is innervated by the phrenic nerve, which originates from the cervical spinal cord. The phrenic nerve also provides sensory innervation to the shoulder region. Therefore, when the diaphragm is irritated or inflamed, the pain signals are transmitted to the spinal cord and interpreted as pain in the shoulder.
State the nerve that supplies serratus anterior and state its root values.
Long thoracic nerve to serratus anterior (C5, 6, 7).
State three actions of serratus anterior.
- It is a powerful protractor of the scapula (it pulls the scapula forward around the chest wall for pushing and punching movements as required during boxing. Hence, serratus anterior is also called boxer’s muscle.)
- It keeps the medial/vertebral border of scapula in firm contact with the chest wall.
- Its lower 4 or 5 digitations along with lower part of the trapezius** rotate the scapula laterally and upwards** during overhead abduction of the arm.
State the clinical relevance of the pectoralis minor muscle.
The pectoralis minor is important clinically and as a surgical landmark, due to the structures that lie below or deep to the muscle and its tendon. Running deep to the pectoralis minor muscle are the nerves and blood supply to the upper limb: the posterior, lateral, and medial cords of the brachial plexus. If the muscle is shortened/tight, this abnormal tension negatively affects the Scapulohumeral Rhythm and can also cause thoracic outlet syndrome.
State the clinical relevance of the subclavius muscle.
It may prevent the jagged ends of a fractured clavicle from damaging the adjacent subclavian vein.
What structures pierce the clavipectoral fascia?
- Cephalic vein
- Lateral pectoral nerve
- Thoraco-acromial artery
- Lymphatic vessels passing between infraclavicular and apical nodes of axilla
- [Diagram]
The spinal nerves between the 4th cervical and 1st thoracic segments do not give cutaneous supply to the skin of the anterior thoracic wall. Account for this fact.
The lower cervical and first thoracic anterior rami form the brachial plexus, which supplies the upper limb. The cutaneous supply to the skin of the anterior thoracic wall is provided by the intercostal nerves, which are derived from the thoracic spinal nerves.
State two signs of paralysis of serratus anterior.
(a) Weakened protraction of the scapula.
(b) Winging of the scapula (Inferior angle and medial border of scapula become unduly prominent particularly when patient pushes his hands against the wall).
Medial scapular winging is caused by injury to the ____(a)____ nerve and hence paralysis of ____(b)____ muscle. Lateral scapular winging is caused by injury to the ____(c)____ nerve and hence paralysis of ____(d)____ muscle.
Medial scapular winging is worsened by arm ____(e)____, whereas lateral scapular winging is worsened by arm ____(f)____.
(a) long thoracic (C5, C6, C7)
(b) serratus anterior
(c) spinal accessory
(d) trapezius
(e) flexion
(f) abduction
[8-minute video]
Describe the origin and insertion of deltoid muscle.
Origin:
1. Anterior unipennate part: upper surface and anterior border of lateral third of clavicle
2. Middle multipennate part: lateral border of acromion
3. Posterior unipennate part: lower lip of crest of spine of scapula
Insertion: V-shaped deltoid tuberosity on lateral aspect of midshaft of humerus
State the nerve supply of deltoid muscle.
Axillary nerve (C5, 6)
Describe the actions of deltoid.
- Anterior (clavicular) fibres are flexors and medial rotators of the arm.
- The posterior (spinous) fibres are the extensors and lateral rotators of the arm.
- The lateral (acromial) fibres are strong abductors of the arm from 15-90 degrees.
Why can’t the acromial fibres of the deltoid abduct the arm from 0-15 degrees?
Within this range, their vertical pull corresponds to the long axis of the arm.
Describe origin and insertion of supraspinatus.
Origin: medial 2/3 of supraspinous fossa of scapula
Insertion: superior facet on greater tubercle of the humerus
[Diagram: supraspinatus]
