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1. Structures in the Costal Groove (from above downward)
👉 V-A-N
V → Posterior intercostal vein
A → Posterior intercostal artery
N → Intercostal nerve
(Remember: “Vein Above Nerve” — VAN)
2. Structures on the Neck of the 1st Rib (from medial to lateral)
👉 S–V–A–N
S → Sympathetic trunk
V → Posterior intercostal vein
A → Superior intercostal artery
N → 1st thoracic nerve
(Mnemonic tip: “Some Very Active Nerves”)
3. Vertebrae – How to Recognize a Thoracic from a Lumbar Vertebra
Thoracic: Heart-shaped body (“Heart in the Thorax”).
Lumbar: Kidney-/bean-shaped body (“Kidneys in Lumbar region”).
Thoracic: Has costal facets on body and transverse processes.
Thoracic spine: Long and oblique.
The thoracic cage protects the heart, lungs, and great vessels, yet remains flexible enough for respiration.
The sternal angle lies opposite the T4 vertebra and marks the level of:
Second costal cartilage
Tracheal bifurcation
Arch of aorta
Upper border of pericardium
True ribs (1–7) articulate directly with the sternum.
False ribs (8–10) articulate indirectly via the costal cartilage of the rib above.
Floating ribs (11–12) have no anterior attachment.
A typical rib has a head, neck, tubercle, and shaft.
First rib is the shortest, broadest, and most curved; it has grooves for subclavian vessels and a scalene tubercle.
The angle of a rib indicates the point of greatest curvature and is a common site of fracture.
Sternum develops from two sternal bars that fuse in the midline; fusion completes by puberty.
Manubriosternal joint forms the sternal angle—a major surface landmark.
Vertebral column provides attachment for ribs and muscles of the back and transmits body weight to lower limbs.
Costovertebral and costotransverse joints are plane synovial joints permitting gliding during respiration.
Ribs move like handles:
Pump-handle movement → increases anteroposterior diameter.
Bucket-handle movement → increases transverse diameter.
Thoracic inlet transmits structures between neck and thorax; thoracic outlet gives passage to structures between thorax and abdomen.
Respiration involves coordinated movement of ribs, sternum, and diaphragm.
Problem:
A 25-year-old man was brought to the emergency department following a road traffic accident. He complained of severe pain in the chest and difficulty in breathing. On examination, there was paradoxical movement of a segment of the chest wall — it moved inward during inspiration and outward during expiration.
Question:
What is the diagnosis? Explain the anatomical basis of this condition.
Answer:
The condition is Flail Chest.
It occurs when multiple adjacent ribs are fractured at two points each, leading to the formation of a free-floating segment of the chest wall.
During inspiration, negative intrathoracic pressure pulls the fractured segment inward, while the rest of the chest expands.
During expiration, positive pressure pushes the segment outward.
This paradoxical movement impairs ventilation and oxygen exchange, leading to respiratory distress.
Clinical Significance:
Immediate stabilization of the chest wall and respiratory support are essential to prevent hypoxia and respiratory failure.
FAQs
The thoracic cage is formed by:
12 thoracic vertebrae and intervertebral discs posteriorly
12 pairs of ribs and their costal cartilages anterolaterally
Sternum anteriorly
True ribs (1–7): Directly attached to the sternum through their own costal cartilages.
False ribs (8–10): Indirectly attached to the sternum via the cartilage of the rib above.
Floating ribs (11–12): Have no anterior attachment; free at their anterior ends.
A typical rib has:
Head: Two articular facets for the corresponding vertebra and the one above.
Neck: Lies between head and tubercle.
Tubercle: Has a facet for articulation with the transverse process.
Shaft: Has an angle and costal groove for intercostal vein, artery, and nerve (V-A-N).
Shortest, broadest, most curved rib.
Single articular facet on head (for T1).
Scalene tubercle on superior surface for scalenus anterior.
Grooves for subclavian vein (anterior) and subclavian artery (posterior).
No angle or costal groove.
Size: First is smaller and flatter.
Head: First rib has one facet, second rib has two.
Surface: First rib has grooves for subclavian vessels; second rib has rough area for serratus anterior.
Curvature: First is more curved.
Parts: Manubrium, body, and xiphoid process.
Attachments:
Manubrium: Clavicle, 1st and 2nd costal cartilages.
Body: 2nd to 7th costal cartilages.
Xiphoid process: Attachment for diaphragm and rectus abdominis.
Sternal angle (Angle of Louis): At junction of manubrium and body, opposite T4 vertebra.
Boundaries:
Posteriorly – body of T1 vertebra
Laterally – first pair of ribs and costal cartilages
Anteriorly – superior border of manubrium
Contents:
Trachea, oesophagus, brachiocephalic vessels, subclavian vessels, and apices of lungs covered by pleura.
Boundaries:
Posteriorly – body of T12 vertebra
Laterally – 11th and 12th ribs
Anteriorly – xiphisternal joint and costal margins
It transmits structures like aorta, oesophagus, thoracic duct, and inferior vena cava between thorax and abdomen.
Manubriosternal joint: Secondary cartilaginous
Xiphisternal joint: Primary cartilaginous
Costovertebral joint: Plane synovial
Costotransverse joint: Plane synovial
Sternocostal joint: 1st → cartilaginous; 2nd–7th → synovial
Costochondral joint: Primary cartilaginous
Interchondral joint: Plane synovial
Costovertebral: Between head of rib and vertebral bodies; plane synovial type.
Costotransverse: Between tubercle of rib and transverse process; plane synovial type.
Allow rotation and gliding movements during respiration.
Type: Secondary cartilaginous (symphysis).
Significance: Forms the sternal angle, a surface landmark for:
2nd costal cartilage
Arch of aorta
Tracheal bifurcation
T4 vertebral level
Inspiration:
Ribs elevate → thoracic volume increases.
Diaphragm descends (piston action).
Expiration:
Ribs depress, diaphragm relaxes → thoracic volume decreases.
Air expelled by elastic recoil.
Definition: Upward and forward movement of ribs that increases the anteroposterior diameter of thorax.
Ribs involved: 2nd to 6th ribs.
Definition: Outward and upward movement of ribs that increases the transverse diameter of thorax.
Ribs involved: 7th to 10th ribs.
Heart-shaped body
Long, downward sloping spinous process
Costal facets on body and transverse processes
Circular vertebral foramen
Cervical and lumbar curvatures → concave posteriorly.
Develop after birth.
Function: Maintain upright posture and balance, absorb shocks during movement.
a) Vertebral column curvatures: Alternating convex and concave curves provide strength and flexibility.
b) Thoracic cage: Bony framework for protection and respiration.
c) Thoracic inlet syndrome: Compression of subclavian vessels or brachial plexus by a cervical rib or tight scalene muscle.
Manubrium: 5th fetal month
Body: 4 sternebrae ossify from 5th–6th fetal months; fuse by 25 years.
Xiphoid process: Appears in 3rd year, fuses by 40 years.
Junction between manubrium and body at T4 level.
Indicates the level of:
2nd costal cartilage
Tracheal bifurcation
Arch of aorta
Upper border of pericardium
Bone marrow biopsy: From manubrium or upper sternum.
Sternal fracture: May injure underlying heart or vessels.
Thoracic outlet syndrome: Compression of neurovascular structures.
Chest compressions (CPR): Performed over lower half of sternum.
MCQs
1. How many true ribs are there in the human body?
a) 5 b) 7 c) 10 d) 12
✅ Answer: b) 7
Explanation: The first seven ribs are true ribs because their costal cartilages articulate directly with the sternum.
2. Which rib is the shortest, broadest, and most curved?
a) 2nd b) 7th c) 1st d) 10th
✅ Answer: c) 1st
Explanation: The first rib is atypical—flat, highly curved, and broad.
3. Which of the following ribs does not have a costal groove?
a) 1st b) 2nd c) 5th d) 7th
✅ Answer: a) 1st
Explanation: The 1st rib lacks a costal groove since its superior surface has grooves for subclavian vessels instead.
4. The manubriosternal joint corresponds to which vertebral level?
a) T2 b) T3 c) T4 d) T5
✅ Answer: c) T4
Explanation: The sternal angle (Angle of Louis) lies opposite the T4 vertebra.
5. Which type of joint is the first sternocostal joint?
a) Synovial b) Primary cartilaginous c) Secondary cartilaginous d) Plane synovial
✅ Answer: b) Primary cartilaginous
Explanation: The 1st sternocostal joint is a synchondrosis (primary cartilaginous joint).
6. How many ossification centers are present in a typical rib?
a) 1 b) 2 c) 3 d) 4
✅ Answer: c) 3
Explanation: One primary center for the shaft and two secondary centers for the head and tubercle.
7. Which movement increases the anteroposterior diameter of the thorax?
a) Bucket-handle b) Pump-handle c) Piston d) Sliding
✅ Answer: b) Pump-handle
Explanation: Pump-handle movement (upper ribs) elevates the sternum, enlarging the anteroposterior dimension.
8. Which movement increases the transverse diameter of the thorax?
a) Bucket-handle b) Pump-handle c) Piston d) Rotation
✅ Answer: a) Bucket-handle
Explanation: Middle and lower ribs elevate laterally, expanding the transverse diameter.
9. The vertebral column normally consists of how many thoracic vertebrae?
a) 10 b) 11 c) 12 d) 13
✅ Answer: c) 12
10. The sternal angle marks which anatomical landmark?
a) Start of ascending aorta b) Arch of aorta c) End of trachea d) Both (b) and (c)
✅ Answer: d) Both (b) and (c)
Explanation: At the sternal angle (T4 level), the trachea bifurcates and the arch of aorta begins and ends.
11. Which ribs are called “floating ribs”?
a) 8–10 b) 9–11 c) 11–12 d) 10–12
✅ Answer: c) 11–12
Explanation: Floating ribs have no anterior attachment to the sternum.
12. Which part of the sternum ossifies last?
a) Manubrium b) Body c) Xiphoid process d) Sternal angle
✅ Answer: c) Xiphoid process
Explanation: The xiphoid process ossifies around the 3rd year and fuses after 40 years.
13. What is the type of costotransverse joint?
a) Ball-and-socket b) Hinge c) Plane synovial d) Saddle
✅ Answer: c) Plane synovial
14. Which of the following statements about the vertebral column is true?
a) Thoracic vertebrae have kidney-shaped bodies.
b) Lumbar vertebrae have costal facets.
c) Thoracic vertebrae have long downward spinous processes.
d) Cervical vertebrae have no transverse foramina.
✅ Answer: c) Thoracic vertebrae have long downward spinous processes.
15. Which ribs take part in both pump-handle and bucket-handle movements?
a) 2nd to 6th b) 7th to 10th c) 5th to 8th d) 1st to 4th
✅ Answer: c) 5th to 8th
Explanation: These ribs lie in the transition zone and show both anteroposterior and transverse expansion.
1. How many bones form the thoracic cage?
→ The thoracic cage is formed by 12 thoracic vertebrae, 12 pairs of ribs with their costal cartilages, and the sternum.
2. Which ribs are typical and which are atypical?
→ Typical ribs: 3rd to 9th.
→ Atypical ribs: 1st, 2nd, 10th, 11th, and 12th.
3. Which rib is the shortest and broadest?
→ The first rib is the shortest, broadest, and most curved.
4. What structures lie on the superior surface of the first rib?
→ Grooves for the subclavian vein (anteriorly) and subclavian artery (posteriorly), separated by the scalene tubercle.
5. What is the angle of a rib?
→ It is the point where the shaft curves forward, and it is a common site of fracture.
6. Which joint forms the sternal angle?
→ The manubriosternal joint, a secondary cartilaginous joint (symphysis).
7. At which vertebral level does the sternal angle lie?
→ At the level of the T4 vertebra.
8. How many true, false, and floating ribs are there?
→ True ribs (1–7), false ribs (8–10), floating ribs (11–12).
9. What type of joint is the first sternocostal joint?
→ Primary cartilaginous joint (synchondrosis).
10. Which type of movement occurs at costovertebral joints?
→ Gliding and rotatory movements during respiration.
11. Define pump-handle movement.
→ Elevation of upper ribs (2–6) that increases the anteroposterior diameter of the thorax.
12. Define bucket-handle movement.
→ Elevation of lower ribs (7–10) that increases the transverse diameter of the thorax.
13. What is the significance of the costal groove?
→ It lodges the intercostal vessels and nerve (V-A-N from above downward).
14. Which type of joint is the xiphisternal joint?
→ Primary cartilaginous joint.
15. Name the three types of joints present in the thoracic cage.
→ Synovial, cartilaginous, and fibrocartilaginous (symphysis) joints.
16. What happens in flail chest?
→ Multiple rib fractures produce a free-floating segment of the chest wall showing paradoxical movement during breathing.
17. Which ribs take part in both pump-handle and bucket-handle movements?
→ 5th to 8th ribs.
18. Name the bones forming the thoracic inlet.
→ Body of T1 vertebra, first pair of ribs and cartilages, and superior border of manubrium sternum.
19. What are the boundaries of the thoracic outlet?
→ Posteriorly T12, laterally 11th and 12th ribs, anteriorly xiphisternal joint and costal margin.
20. What are the clinical uses of the sternum?
→ Bone-marrow aspiration, sternal fracture identification, CPR landmark, and midline surgical access.
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