B) Vertical, antero-posterior, and rotational movement

Explanation: The sternoclavicular joint allows for vertical, antero-posterior, and rotational movements, making it versatile in its function.

A) To protect the heart and lungs

Explanation: The thoracic wall serves as a protective structure for vital organs such as the heart and lungs, ensuring their safety from external trauma.

B) It provides attachment and support to upper limbs

Explanation: The thoracic wall serves as an attachment point for muscles and structures that support and facilitate the movement of the upper limbs, contributing to overall mobility.

B) Ribs 1-7

Explanation: True ribs are defined as ribs 1 through 7, which directly attach to the sternum, distinguishing them from false ribs.

B) Fibrocartilaginous

Explanation: The joint between the first rib and the sternum is classified as fibrocartilaginous, which provides stability and support at this critical junction.

C) Depress the ribs

Explanation: The innermost intercostal muscles primarily function to depress the ribs, aiding in forced expiration.

B) Two (bilateral)

Explanation: The medial arcuate ligaments are present bilaterally, meaning there are two of them, one on each side of the body, contributing to the support of the diaphragm.

B) To assist in breathing

Explanation: The diaphragm is a crucial muscle in the thoracic wall that plays a primary role in respiration by contracting and relaxing to facilitate inhalation and exhalation.

B) To assist in inspiration

Explanation: The external intercostal muscles are primarily responsible for aiding in the process of inspiration by elevating the ribs and expanding the thoracic cavity.

D) Superior intercostal artery

Explanation: The superior intercostal artery, also known as the supreme intercostal artery, branches from the costocervical trunk of the subclavian artery and supplies the upper two or three intercostal spaces.

C) To aid in forced exhalation

Explanation: The internal intercostal muscles primarily function to aid in forced exhalation by depressing the ribs, which decreases the volume of the thoracic cavity and expels air from the lungs.

B) Subcostal

Explanation: The subcostal muscles are located beneath the ribs and play a role in expiration by helping to lower the rib cage during breathing.

A) Costotransverse joint

Explanation: The costotransverse joint works alongside the costovertebral joint to facilitate the movement of the ribs.

C) Protraction of the scapula

Explanation: The serratus anterior muscle is primarily responsible for the protraction of the scapula, which is essential for movements such as pushing and reaching forward.

C) Three

Explanation: The sternum is typically divided into three parts: the manubrium, the body, and the xiphoid process, each contributing to its overall structure.

B) Fibrocartilaginous

Explanation: The manubriosternal joint is classified as a symphysis, which is a type of fibrocartilaginous joint, providing stability between the manubrium and the body of the sternum.

B) 'Hands in the pocket'

Explanation: The external intercostal muscles are often described with the mnemonic 'hands in the pocket' to indicate their orientation and direction of fibers, which run obliquely downward and forward.

B) Jugular notch

Explanation: The suprasternal notch is also referred to as the jugular notch, which is a prominent feature located at the top of the sternum.

C) Diaphragm

Explanation: The diaphragm is the primary muscle that forms the floor of the thoracic cavity, playing a crucial role in respiration by contracting and relaxing to facilitate breathing.

B) Pectoralis minor

Explanation: The pectoralis minor is located deeper than the pectoralis major, lying underneath it and contributing to the stabilization of the scapula.

B) By providing a rigid exterior wall to prevent collapse of elastic lungs

Explanation: The thoracic wall provides structural support that prevents the elastic lungs from collapsing, ensuring they can function effectively during respiration.

C) To protect blood vessels and nerves

Explanation: The primary function of the costal groove is to provide a protective channel for blood vessels and nerves that run along the rib, ensuring their safety as they travel through the thoracic cavity.

A) Supports the diaphragm

Explanation: The median arcuate ligament is a fibrous structure that supports the diaphragm, playing a crucial role in the anatomy of the thoracic wall.

B) It marks the bifurcation of the trachea

Explanation: The sternal angle is significant as it marks the bifurcation of the trachea into the right and left main bronchi, which is crucial for respiratory anatomy.

A) Winged scapula

Explanation: Injury to the long thoracic nerve can lead to a condition known as winged scapula, where the scapula protrudes outwards due to weakness of the serratus anterior muscle.

C) Intercostal nerves

Explanation: The intercostal nerves, which are part of the ventral primary rami, are specifically responsible for innervating the intercostal muscles, facilitating movement and respiration.

B) Phrenic nerve

Explanation: The phrenic nerve is the main nerve that innervates the diaphragm, providing the necessary signals for contraction during the breathing process.

A) External intercostal membrane

Explanation: The external intercostal muscles are associated with the external intercostal membrane, which is the continuation of the muscle fibers and provides support to the thoracic wall.

C) Phrenic nerves

Explanation: The diaphragm is innervated by the phrenic nerves, which originate from the cervical spinal nerves C3, C4, and C5, playing a crucial role in respiration.

A) Left pleural cavity, right pleural cavity, mediastinum

Explanation: The thoracic cavity is divided into three main parts: the left pleural cavity, the right pleural cavity, and the mediastinum, which are essential for understanding the structure of the thoracic region.

C) Rotation and elevation

Explanation: The ribs rotate and elevate along the costovertebral joint, allowing for important movements during respiration.

B) To support the rib cage

Explanation: The sternum plays a crucial role in supporting the rib cage, providing structural integrity and protection for the thoracic organs.

C) Long thoracic nerve

Explanation: The serratus anterior muscle is innervated by the long thoracic nerve, which is crucial for its function in scapular movement.

C) At the bottom of the sternum

Explanation: The xiphoid process is the smallest and most inferior part of the sternum, located at the bottom, and serves as an attachment point for various muscles.

B) External intercostals

Explanation: The external intercostals are the muscles that elevate the ribs during inhalation, facilitating the expansion of the thoracic cavity and allowing air to enter the lungs.

B) Internal thoracic artery

Explanation: The internal thoracic artery branches from the subclavian artery and is responsible for supplying blood to the anterior thoracic wall, making it crucial for thoracic circulation.

B) It aids in respiration

Explanation: The diaphragm plays a crucial role in respiration by contracting and relaxing to facilitate the inhalation and exhalation of air, working in conjunction with the thoracic wall.

B) Details of the pleural cavities and mediastinum

Explanation: The text indicates that further details about the pleural cavities and mediastinum will be covered in upcoming lectures, highlighting their importance in thoracic anatomy.

B) The superior edge of the heart

Explanation: The sternal angle marks the superior edge of the heart, indicating its position relative to the thoracic wall.

D) Ribs 11-12

Explanation: Ribs 11 and 12 are classified as floating ribs because they do not attach to the sternum or to other ribs, allowing for greater flexibility in the rib cage.

B) They are visible through a 'window'

Explanation: The internal intercostal muscles can be identified through a 'window' created by the external intercostal membrane, allowing for their visibility during anatomical studies.

B) Rotation of the trunk

Explanation: The superior and inferior articular processes of the thoracic vertebrae facilitate the rotation of the trunk, allowing for a range of motion in the upper body.

B) Along axons

Explanation: The shingles virus is transported along axons, which are the long projections of nerve cells, leading to its effect on a specific dermatome.

B) Stabilization of the scapula

Explanation: The pectoralis minor primarily functions to stabilize the scapula by drawing it anteriorly and inferiorly against the thoracic wall.

C) T12

Explanation: The inferior boundary of the thoracic wall is marked by vertebra T12, which is the lowest vertebra in the thoracic region.

C) External intercostal m.

Explanation: The external intercostal muscle is the most superficial muscle layer in the thoracic wall, playing a crucial role in the mechanics of breathing by aiding in inhalation.

C) Articular disc

Explanation: The sternoclavicular joint is divided into two compartments by an articular disc, which helps in stabilizing the joint and allowing for smooth movement.

B) A depression for blood vessels and nerves

Explanation: The costal groove is a notable feature on the underside of a rib that serves as a channel for blood vessels and nerves, providing protection and a pathway along the rib.

C) C3, C4, C5

Explanation: The phrenic nerves, which innervate the diaphragm, arise from the cervical spinal nerves C3, C4, and C5, indicating their importance in controlling diaphragm movement.

B) Supports the thoracic wall

Explanation: The lateral arcuate ligaments, which are also present bilaterally, play a role in supporting the thoracic wall and maintaining structural integrity.

C) It affects a single dermatome

Explanation: Shingles is transported along axons and specifically affects a single dermatome, which is a region of skin supplied by a single spinal nerve.

B) A flexible cage

Explanation: The thoracic wall is often described as a flexible cage that allows for the expansion and contraction necessary for breathing while providing protection to the thoracic cavity.

B) Ribs

Explanation: The serratus anterior muscle originates from the upper eight or nine ribs, which allows it to effectively protract and stabilize the scapula during arm movements.

B) T8

Explanation: The inferior vena cava passes through the diaphragm at the caval hiatus located at the T8 vertebral level, which is crucial for understanding the anatomy of the diaphragm.

C) Supply blood to the intercostal muscles

Explanation: The anterior intercostal arteries branch from the internal thoracic artery and supply blood to the intercostal muscles, which are essential for respiration.

D) Diaphragm

Explanation: The diaphragm assists in both inhalation and exhalation; it contracts during inhalation to increase thoracic volume and relaxes during exhalation to decrease thoracic volume.

C) It is part of the inferior boundary

Explanation: The costal margin is part of the inferior boundary of the thoracic wall, contributing to the lower limit of the thoracic cavity.

C) Scalene tubercle

Explanation: The scalene tubercle on the 1st rib serves as an attachment point for the scalene muscles, which are important for respiration and neck movement.

C) Synovial joint

Explanation: The sternoclavicular joint is classified as a synovial joint, which is characterized by the presence of a joint capsule and synovial fluid, allowing for a wide range of movements.

C) Intercostal muscles

Explanation: The intercostal muscles are primarily responsible for the movement of the thoracic wall during breathing, helping to expand and contract the chest cavity.

C) Synovial joint

Explanation: The costovertebral joint is classified as a synovial joint, which allows for movement such as rotation and elevation of the ribs.

B) Transversus thoracis

Explanation: The transversus thoracis muscle is located on the inner surface of the thoracic cage and helps stabilize the thoracic wall.

C) Sternum

Explanation: The sternum is commonly known as the breastbone, located in the center of the chest and serving as a key component of the thoracic skeleton.

C) Diaphragm

Explanation: The inferior thoracic aperture is enclosed by the diaphragm, which separates the thoracic cavity from the abdominal cavity.

C) Pulling movements

Explanation: The serratus anterior primarily assists with pushing movements and stabilizing the scapula, but it does not play a significant role in pulling movements.

B) Fibrocartilaginous

Explanation: The xiphisternal joint is also a symphysis, which is a fibrocartilaginous joint, connecting the xiphoid process to the body of the sternum.

B) Supplies the thoracic wall and breast

Explanation: The internal thoracic artery primarily supplies the thoracic wall and the breast, providing important blood flow to these areas.

C) It indicates the level of the second rib

Explanation: The sternal angle is an important anatomical landmark that corresponds to the level of the second rib, aiding in the identification of thoracic structures.

C) Intercostal muscles

Explanation: The transversus thoracis muscle is located on the inner surface of the thoracic wall and is associated with the intercostal muscles, playing a role in the mechanics of breathing.

C) Middle thoracic splanchnic

Explanation: The thoracic splanchnic nerves include the greater, lesser, and least thoracic splanchnics, but there is no middle thoracic splanchnic nerve.

D) Diaphragm muscle

Explanation: The diaphragm is a dome-shaped muscle that plays a crucial role in respiration by contracting and relaxing to facilitate breathing.

B) Internal thoracic a.

Explanation: The internal thoracic artery gives rise to the anterior intercostal arteries, which supply blood to the anterior intercostal spaces, contributing to the overall arterial supply of the thoracic wall.

E) No muscles lie between them

Explanation: The internal intercostal muscle and the innermost intercostal muscle lie directly adjacent to each other, with no other muscles situated between them in the intercostal space.

B) To protect internal air- and fluid-filled organs

Explanation: The thoracic wall serves a crucial role in protecting vital internal organs that are filled with air and fluids, such as the lungs and heart, from external injury.

C) The body

Explanation: The costal groove is located on the body of the rib, specifically on its underside, which is important for the passage of nerves and blood vessels.

B) They support the rib cage

Explanation: The thoracic vertebrae provide structural support for the rib cage, anchoring the ribs and contributing to the overall stability of the thoracic wall.

B) Mediastinum

Explanation: The mediastinum is the central compartment of the thoracic cavity, situated between the left and right pleural cavities, and contains vital structures such as the heart and major blood vessels.

C) 24

Explanation: There are typically 24 ribs in the human body, which correspond to 12 pairs, and these ribs are associated with the intercostal muscles.

C) False ribs

Explanation: Ribs 8 through 12 are classified as false ribs because they do not attach directly to the sternum, with ribs 11 and 12 being specifically noted as floating ribs.

B) Below the lungs

Explanation: The diaphragm is located below the lungs, separating the thoracic cavity from the abdominal cavity, which is essential for its function in respiration.

C) Manubrium of sternum

Explanation: The superior boundary of the thoracic wall is defined by vertebra T1, rib 1, and the manubrium of the sternum, which collectively form the upper limit of the thoracic cavity.

E) Rib 1

Explanation: The inferior boundary of the thoracic wall includes vertebra T12, rib 12, the costal margin, and the xiphoid process, while rib 1 is part of the superior boundary.

D) Posterior intercostal artery

Explanation: The posterior intercostal arteries branch directly from the aorta and supply blood to the intercostal spaces located at the back of the thoracic wall.

C) Esophagus

Explanation: The esophageal hiatus, located at the T10 vertebral level, allows the esophagus to pass through the diaphragm, facilitating the connection between the thoracic and abdominal cavities.

C) Xiphoid process

Explanation: The xiphoid process is the inferior part of the sternum, serving as an important landmark in thoracic anatomy.

C) Anterior cutaneous branch

Explanation: The anterior cutaneous branch is a part of the intercostal nerves, which originate from the ventral primary rami, not the dorsal primary rami.

B) To drain blood from the thoracic wall and abdominal wall

Explanation: The azygous veins primarily function to drain blood from the thoracic and abdominal walls, playing a crucial role in venous return to the heart.

B) Anterior and posterior intercostal arteries

Explanation: The thoracic wall receives its blood supply from the anterior and posterior intercostal arteries, which branch from the aorta and other major arteries, ensuring adequate perfusion to the thoracic structures.

B) By providing auxiliary lung expansion

Explanation: The thoracic wall aids in lung expansion by providing additional support and space, allowing for greater lung capacity during inhalation.

E) Pelvis

Explanation: The pelvis is not part of the thoracic wall; it is part of the lower body structure, while the ribs, sternum, and vertebrae are integral components of the thoracic wall.

D) T4-5

Explanation: The sternal angle marks the plane through the T4-5 vertebral levels, serving as an important anatomical landmark.

C) Herpes zoster

Explanation: Shingles is medically referred to as herpes zoster, which is a viral infection that affects the spinal ganglion.

B) To anchor the rib cage by abdominal muscles

Explanation: Floating ribs play an important role in anchoring the rib cage through the abdominal muscles, providing stability while allowing for flexibility.

C) Viral infection

Explanation: Shingles is a viral infection caused by the reactivation of the varicella-zoster virus, which is the same virus that causes chickenpox.

C) Thorax

Explanation: The thoracic region is commonly referred to as the thorax, which encompasses the area between the neck and the abdomen.

B) They ossify

Explanation: With age, symphyses and costal cartilages tend to ossify, which can lead to decreased flexibility and mobility in the thoracic region.

B) Supply blood to the thoracic wall

Explanation: The internal thoracic artery primarily supplies blood to the thoracic wall and the anterior intercostal spaces, playing a crucial role in the vascularization of the chest area.

C) Abdominal aorta

Explanation: The aortic hiatus, located at the T12 vertebral level, allows the abdominal aorta and thoracic duct to pass through the diaphragm, which is essential for vascular and lymphatic circulation.

D) Biceps brachii

Explanation: The biceps brachii is primarily located in the upper arm and is not considered part of the pectoral region, unlike the pectoralis major, pectoralis minor, serratus anterior, and subclavius.

B) Depress the ribs during exhalation

Explanation: The internal intercostal muscles primarily function to depress the ribs during forced exhalation, contributing to the expulsion of air from the lungs.

E) Pulmonary artery

Explanation: The pulmonary artery is not associated with the diaphragm's openings; instead, the diaphragm has specific openings for the inferior vena cava, esophagus, abdominal aorta, and thoracic duct.

B) Ventral primary rami

Explanation: Intercostal nerves originate from the ventral primary rami of the thoracic spinal nerves, which are responsible for motor and sensory innervation in the thoracic wall.

D) It accommodates the subclavian vein

Explanation: The groove for the subclavian vein on the 1st rib is significant as it provides a pathway for the vein, ensuring it is positioned correctly and protected during movement.

C) To facilitate breathing

Explanation: The diaphragm is the primary muscle responsible for facilitating breathing by contracting and expanding the thoracic cavity, allowing air to flow into the lungs.

B) To ascertain the position of rib 2

Explanation: The sternal angle is specifically used to locate the position of rib 2, which is important for counting ribs during anatomical examinations.

C) Superior thoracic aperture

Explanation: The superior thoracic aperture is the upper boundary of the thoracic cavity, allowing communication with the neck and upper structures.

B) Ribs 2-7

Explanation: Ribs 2-7 form synovial joints with the sternum, allowing for greater mobility compared to the first rib's fibrocartilaginous joint.

C) Skeletal muscle

Explanation: The diaphragm is primarily composed of skeletal muscle, which allows for voluntary control during breathing, although it also functions involuntarily.

B) Pectoralis major

Explanation: The pectoralis major is known for its role in adducting and medially rotating the upper limb, making it a key muscle in upper limb movements.

B) They bear weight

Explanation: Intervertebral discs are crucial for bearing weight in the thoracic region, helping to distribute loads across the vertebral column.

B) Internal thoracic artery

Explanation: The internal thoracic artery gives rise to the anterior intercostal arteries, which supply blood to the anterior intercostal spaces.

D) Posterior intercostal a.

Explanation: The posterior intercostal arteries branch from the thoracic aorta and supply blood to the intercostal spaces, playing a crucial role in the arterial supply of the thoracic wall.

B) Internal thoracic veins or Azygos veins

Explanation: Intercostal veins drain into either the internal thoracic veins or the azygos veins, which then contribute to the superior vena cava, highlighting their role in venous drainage of the thoracic wall.

B) The neck and upper back

Explanation: The costocervical trunk branches from the subclavian artery and supplies blood to the neck and upper back regions, including some intercostal spaces.

B) To accommodate the subclavian artery

Explanation: The groove for the subclavian artery on the 1st rib is specifically designed to accommodate the subclavian artery, allowing it to pass safely beneath the rib.

C) Left subclavian vein

Explanation: The left subclavian vein drains blood superiorly to the superior vena cava, contributing to the venous return from the upper body.

B) The hemiazygous vein drains into the azygous vein

Explanation: The hemiazygous vein typically drains into the azygous vein, allowing for the integration of venous return from the lower thoracic region.

E) All of the above

Explanation: The thoracic vertebrae play a crucial role in the thoracic wall by protecting vital organs like the lungs, providing attachment points for the diaphragm, and allowing for the movement of the ribs during respiration.

A) To protect the heart and lungs

Explanation: The thoracic wall, also known as the thoracic cage, serves to enclose and protect vital organs such as the heart and lungs within the thoracic cavity.

A) True ribs

Explanation: True ribs (ribs 1-7) articulate directly with the sternum via their costal cartilages, providing a direct connection that aids in the protection of thoracic organs.

B) Lateral cutaneous branch

Explanation: The lateral cutaneous branch of the dorsal primary rami is associated with the innervation of the deep back, providing sensory information from that region.

B) Ribs that make up the thoracic cage

Explanation: The transverse boundary of the thoracic wall is formed by the ribs that create the thoracic cage, providing structural support and protection for the thoracic organs.

C) To relay sympathetic nerve signals

Explanation: The sympathetic trunk is primarily responsible for relaying sympathetic nerve signals throughout the body, playing a crucial role in the autonomic nervous system.

D) To connect the thoracic and abdominal cavities

Explanation: The inferior thoracic aperture serves as the boundary between the thoracic cavity and the abdominal cavity, allowing for the passage of structures such as the esophagus and major blood vessels.

B) Intercostal nerves

Explanation: The thoracic wall is primarily supplied by intercostal nerves, which are the ventral primary rami of the thoracic spinal nerves, playing a crucial role in innervating the muscles and skin of the thoracic region.

B) For articulation with ribs

Explanation: The superior costal demifacet is specifically designed for articulation with the ribs, allowing for the connection between the thoracic vertebrae and the rib cage, which is essential for respiratory mechanics.

D) Innermost intercostal m.

Explanation: The innermost intercostal muscle is located deep to the internal intercostal muscles, forming part of the internal structure of the thoracic wall.

C) Esophagus, aorta, and inferior vena cava

Explanation: The diaphragm allows for the passage of several critical structures, including the esophagus, aorta, and inferior vena cava, which are essential for bodily functions.

C) 12

Explanation: There are typically 12 intercostal spaces in the thoracic wall, corresponding to the 12 pairs of thoracic spinal nerves that supply the intercostal muscles and overlying skin.

C) They influence the passage of structures between the thorax and neck

Explanation: The dimensions of the superior thoracic aperture are significant as they influence the passage of various structures between the thorax and neck, impacting both respiratory and circulatory systems.

B) Costal groove

Explanation: Intercostal nerves travel in the costal groove, which is a protective space along the ribs that houses the nerves and blood vessels.

B) Internal intercostal muscles

Explanation: The internal intercostal muscles play a significant role in forced expiration by depressing the ribs and reducing the volume of the thoracic cavity.

B) It has a groove for the subclavian vein

Explanation: The 1st rib is characterized by having a groove for the subclavian vein, which is an important anatomical feature that distinguishes it from other ribs.

C) The seventh cervical vertebra

Explanation: The vertebra prominens refers to the seventh cervical vertebra, which is easily palpated and serves as a key landmark in the cervical region.

B) Branches that connect spinal nerves to the sympathetic trunk

Explanation: Rami communicantes are branches that connect spinal nerves to the sympathetic trunk, facilitating communication between the central nervous system and the sympathetic nervous system.

C) Inferior vena cava

Explanation: The inferior vena cava is not part of the azygous system; it is a major vein that carries deoxygenated blood from the lower body to the heart.

B) Depress the ribs

Explanation: The transverse thoracis muscle primarily functions to depress the ribs, particularly during forced expiration, aiding in the mechanics of breathing.

C) Midway between contracted and relaxed

Explanation: During normal breathing, the diaphragm moves between contracted and relaxed states, allowing for efficient airflow into the lungs.

B) Triangular

Explanation: The superior thoracic aperture is best described as having a triangular shape, which is important for its anatomical relationships and the structures that pass through it.

B) It contracts and moves downward

Explanation: During inhalation, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity and allowing air to flow into the lungs.

B) Provide sensory innervation to the anterior thorax

Explanation: The anterior cutaneous branch of the intercostal nerves provides sensory innervation to the anterior thorax, allowing for sensation in that area.

B) Internal thoracic artery

Explanation: The internal thoracic artery gives rise to the anterior intercostal arteries, which supply blood to the anterior intercostal spaces of the thoracic wall.

E) Femoral artery

Explanation: The femoral artery is not involved in the arterial supply of the thoracic wall; it supplies the lower limb instead.

D) Adduction

Explanation: The primary action of the pectoralis major during arm movements is adduction, which brings the arm closer to the body.

A) Greater thoracic splanchnic

Explanation: The greater thoracic splanchnic nerve primarily innervates the abdominal organs, providing sympathetic innervation to structures in the abdomen.

C) Nerves, blood vessels, and the trachea

Explanation: The superior thoracic aperture allows for the passage of various structures, including nerves, blood vessels, and the trachea, which are essential for respiratory and circulatory functions.

A) 12

Explanation: There are typically 12 thoracic vertebrae in the human body, which are characterized by their unique features that allow for the articulation with the ribs and support the thoracic cavity.

C) External intercostals

Explanation: The external intercostals are most active during quiet inspiration as they elevate the ribs, facilitating the inhalation process.

B) They facilitate rib elevation

Explanation: The superior and inferior costal (demi) facets on the bodies of thoracic vertebrae are designed to allow for the elevation of ribs during respiration.

C) A branch of the subclavian artery

Explanation: The costocervical trunk is a branch of the subclavian artery that gives rise to the superior intercostal artery and other branches, supplying the upper thoracic region.

D) Pectoralis major

Explanation: The pectoralis major is not considered a muscle of the thoracic wall; it is primarily involved in movements of the shoulder and arm, whereas the other options are directly associated with the thoracic wall.

C) They enable trunk rotation and rib elevation

Explanation: The articulations of thoracic vertebrae are significant as they facilitate both trunk rotation and rib elevation, which are essential for various movements and respiratory functions.

C) It serves as a passage for the diaphragm's central tendon

Explanation: The inferior thoracic aperture provides a structural opening that allows the diaphragm's central tendon to connect with the surrounding thoracic and abdominal structures.

B) Head

Explanation: The head of the 1st rib articulates with the corresponding thoracic vertebra, forming a crucial joint that contributes to the ribcage's structure.

B) External intercostal membrane

Explanation: The external intercostal membrane is found at the most superficial layer of the thoracic wall, providing a supportive structure for the external intercostal muscles.

B) Secondary blood vessels and nerves

Explanation: Collateral branches refer to the secondary blood vessels and nerves that arise from the main intercostal vessels and nerves, providing additional support and supply to the thoracic wall.

B) On the transverse processes

Explanation: Costal facets are located on the transverse processes of thoracic vertebrae, which play a key role in rib articulation.

D) It forms the vagal trunks

Explanation: The vagus nerve, through its vagal trunks, plays a role in innervating the esophagus and other structures passing through the diaphragm, but it does not directly innervate the diaphragm itself.

A) Intercostal vein, artery, and nerve

Explanation: The intercostal vein, artery, and nerve are specifically noted to run in the (sub)costal groove, which is an important anatomical feature of the intercostal space.

C) To connect the thoracic cavity to the neck

Explanation: The superior thoracic aperture serves as the opening that connects the thoracic cavity to the neck, allowing for the passage of structures such as blood vessels and nerves.

B) It is a major pathway for sympathetic nerve fibers

Explanation: The sympathetic trunk serves as a major pathway for sympathetic nerve fibers, allowing for the distribution of autonomic signals throughout the thoracic region and beyond.

E) Femoral a.

Explanation: The femoral artery is not associated with the thoracic aorta; it is a major artery of the thigh, while the other options are directly related to the arterial supply of the thoracic region.

B) Diaphragm

Explanation: The diaphragm is identified as the primary muscle of inspiration, playing a crucial role in the breathing process by contracting and allowing the lungs to expand.

C) Supplies blood to the anterior chest wall

Explanation: The internal thoracic artery primarily supplies blood to the anterior chest wall and the breasts, making it essential for the vascularization of these areas.

E) Femoral vein

Explanation: The femoral vein is not involved in the drainage of intercostal veins; instead, intercostal veins drain into the internal thoracic veins, azygos veins, and subsequently to the superior vena cava or left brachiocephalic vein.

C) Costocervical trunk

Explanation: The superior intercostal artery, which supplies the first two or three intercostal spaces, branches from the costocervical trunk.

B) Facets for rib articulation

Explanation: Costal demifacets are specific anatomical features on thoracic vertebrae that provide surfaces for the articulation with the heads of the ribs, allowing for the necessary movement and stability of the thoracic cage.

B) Manubrium of the sternum

Explanation: The superior thoracic aperture is bordered by the manubrium of the sternum anteriorly, which is a key anatomical landmark in the thoracic region.

D) Clavicle

Explanation: The clavicle is not considered part of the thoracic wall; it is a bone that connects the arm to the body, while the other options are structures associated with the thoracic wall.

B) For articulation with the ribs

Explanation: The transverse costal facet is located on the transverse processes of thoracic vertebrae and serves as a point of articulation for the ribs, facilitating the movement of the rib cage during breathing.

C) Receives drainage from the internal thoracic veins

Explanation: The left brachiocephalic vein receives drainage from the internal thoracic veins, playing a crucial role in the venous return from the thoracic region.

B) It houses the intercostal vessels and nerves

Explanation: The costal groove is significant as it provides a protective pathway for the intercostal vein, artery, and nerve, ensuring their safety as they run along the rib cage.

C) Abdominal wall

Explanation: The abdominal wall is noted as the primary contributor to active expiration, helping to push air out of the lungs during forceful exhalation.

C) Superior vena cava

Explanation: The azygos vein drains into the superior vena cava, serving as a major pathway for venous return from the thoracic wall and other structures.

B) Supplies blood to the spinal cord

Explanation: The radicular arteries are responsible for supplying blood to the spinal cord, highlighting their importance in the vascularization of the central nervous system.

C) Superior vena cava

Explanation: The intercostal veins ultimately drain into the superior vena cava, which is the major vein that returns deoxygenated blood to the heart from the upper body.

B) Depress ribs

Explanation: The internal intercostals are most active during expiration as they depress the ribs, aiding in the exhalation process.

B) To facilitate breathing

Explanation: The intercostal muscles play a crucial role in the mechanics of breathing by helping to expand and contract the thoracic cavity during inhalation and exhalation.

C) Internal jugular vein

Explanation: The internal jugular vein is responsible for draining blood from the left side of the head and neck, directing it towards the superior vena cava.

B) To stiffen the thoracic wall

Explanation: The intercostal muscles primarily act to stiffen the thoracic wall, resisting elastic forces during breathing, which helps maintain the structural integrity of the thoracic cavity.

B) To provide sensory and motor innervation to the thoracic wall

Explanation: The primary function of intercostal nerves is to provide both sensory and motor innervation to the muscles and skin of the thoracic wall, facilitating movement and sensation.