Anatomy Unit 4 Lesson 1 Thoracic/Abdominal Muscles & Bones

Describe four unique features of Rib I.

1. Articulates only with T1 at costal facet and transverse costal facet (two points of articulation). 2. Scalene tubercle: insertion point for scalenus anterior 3. Posterior groove allows passage of subclavian artery 4. Anterior groove allows passage of subclavian vein

Which two ligaments stabilize the costotransverse joint? Where are they located?

1. Costotransverse ligament: posterior surface of head and neck of rib to anteromedial surface of transverse process of thoracic vertebra. (#1 in photo) 2. Lateral costotransverse ligament: superior, lateral, and inferior surfaces of costal tubercle of rib to anterolateral surface of transverse process of thoracic vertebra. (#2 in photo)

Internal Intercostal functions? (2)

1. Move ribs inferiorly, mostly during expiration 2. Support intercostal space

External Intercostal functions? (2)

1. Move ribs superiorly, mostly during inspiration 2. Support intercostal space

Within the abdominal cavity, the abdominal viscera are distributed into two major spaces. What are they?

1. Within the peritoneal cavity 2. Between the peritoneal cavity and the musculoskeletal wall

The lateral border of the body of the sternum has four articular facets and two demifacets. Describe their positions, and tell which ribs they articulate with.

A demifacet is located at the superior lateral border of the sternal body, and connects superiorly with a demifacet on the inferior lateral border of the manubrium. These two demifacets comprise the articular surface for the costal cartilage of Rib II. Four articular facets are found along the lateral edge of the sternal body inferior to the superior demifacet, and articulate with the costal cartilages of Ribs III-VI. A second demifacet is located at the extreme posterior lateral border of the sternal body, and connects inferiorly with a demifacet on the superior lateral border of the xiphoid process. These two demifacets comprise the articular surface for Rib VII.

What defines a "false" rib? Which ribs are false ribs?

A false rib does not articulate to the sternum via its own cartilage. Ribs VIII-XII are false ribs.

What defines a "floating" rib? Which ribs are floating ribs?

A floating rib does not articulate at all with the sternum. Ribs XI and XII are floating ribs.

What defines a "true" rib? Which ribs are true ribs?

A true rib articulates with the sternum via its own costal cartilage. Ribs I-VII are true ribs.

Innermost Intercostal function?

Acts with Internal Intercostals

External Oblique Innervation?

Anterior rami T7-T12

Rectus abdominis innervation?

Anterior rami of T7-T12

Internal Oblique Innervation?

Anterior rami of T7-T12, L1

Transversus abdominis innervation?

Anterior rami of T7-T12, L1

Pyramidalis innervation?

Anterior ramus T12

What are the attachment points (2) for the inguinal ligament?

Anterior superior iliac spine to pubic tubercle

Transversus abdominis insertions? (3)

Aponeurosis to linea alba Pubic crest Pectineal line

Through what structure does the brachial plexus pass?

Axillary Inlet

Describe the costovertebral joint in general terms.

Between the head of a rib and vertebra(e). (Remember: the heads of Ribs I, X, XI, and XII articulate with only the vertebra of the same number as the rib.)

Transversus abdominis function?

Compress abdominal contents

Internal Oblique Functions? (2)

Compress abdominal contents Flex trunk

Rectus abdominis functions?

Compress abdominal contents Flex vertebral column Tense abdominal wall

External Oblique Functions? (2)

Compress abdominal contents Flex trunk

Rectus abdominis insertions? (2)

Costal cartilages of ribs V to VII Xiphoid process

Which joint is found between the ribs and the transverse processes of thoracic vertebra?

Costotransverse joint

Transversus thoracis function?

Depress costal cartilages

Subcostales function?

Depress ribs

What structure closes the inferior thoracic aperture?

Diaphragm

Describe the unique features of Ribs XI and XII (floating ribs).

Do not articulate with sternum, but tips are still covered in cartilage. Single point of articulation with body of vertebra of same number as rib. (Do not articulate with transverse processes as does Rib X.) Short. No neck or tubercles.

From superficial to deep, name the three layers of intercostal muscles.

External Intercostal Internal Intercostal Innermost Intercostal

The aponeuroses of which three muscles contribute to linea alba?

External Oblique Internal Oblique Transversus abdominis

External Oblique Origin?

External surfaces of lower 8 ribs

Pyramidalis origins? (2)

Front of pubis Pubic symphysis

What structures are contained in the mediastinum?

Heart Esophagus Trachea Major nerves Systemic Blood Vessels (e.g., Aorta, Vena Cavae)

Internal Oblique Origins? (3)

Iliac crest between origins of external oblique and transversus abdominis Lateral 2/3 of inguinal ligament Thoracolumbar fascia

Transversus thoracis insertions? (3)

Inferior aspect of deep surface of sternum Xiphoid process Costal cartilages IV-VII

Internal Oblique Insertions? (3)

Inferior border of lower 3 or 4 ribs Aponeurosis to linea alba Pubic crest and pectineal line

External Intercostal origin?

Inferior margin of rib above

Transversus thoracis origins (2)?

Inferior margins and internal surface of costal cartilages of 2nd-6th ribs

What structures are found between the Internal Intercostal muscle and Innermost Intercostal muscle?

Intercostal Veins Intercostal Arteries Intercostal nerves Found superiorly in intercostal groove. See collateral branches of each structure inferiorly in groove.

External Intercostal innervation?

Intercostal nerve

Innermost Intercostal innervation?

Intercostal nerve

Internal Intercostal innervation?

Intercostal nerve

Subcostales innervation?

Intercostal nerve

Transversus thoracis innervation?

Intercostal nerve

Innermost Intercostal insertion?

Internal aspect of superior margin of rib below

Subcostales origin?

Internal surface of lower ribs near angle

Subcostales insertion?

Internal surface of second or third rib below

What is unique about the sternocostal joint between the cartilage of Rib I and the manubrium?

It is a fibrocartilage connection, not a synovial joint as are the articulations between the cartilage of Ribs II-VII and the sternum. The point of connection on the manubrium is therefore called an "attachment site" rather than an "articular surface."

What are interchondral joints?

Joints between costal cartilages of adjacent ribs, primarily ribs VII-XII.

What are the functions of the abdominal muscles, collectively? (4)

Keep viscera in abdominal cavity Protect viscera from injury Maintain position of viscera in erect posture Assist in expiration by pushing viscera upward

What are the borders of the axillary inlet?

Lateral border of first rib Superior border of scapula Posterior border of clavicle

Internal Intercostal origin?

Lateral edge of costal groove of rib above

External Oblique Insertion?

Lateral lip of iliac crest Aponeurosis to linea alba

Pyramidalis insertion?

Linea Alba

What structure gives rise to the inguinal ligament?

Lower border of aponeurosis of external oblique

Which three fused bones make up the sternum?

Manubrium (superior) Body (middle) Xiphoid process (inferior)

Innermost Intercostal origin?

Medial edge of costal groove of rib above

Transversus abdominis origins? (3)

Medial lip of iliac crest Lateral 1/3 of inguinal ligament Costal cartilages of lower 6 ribs

What structure divides the inferior mediastinum into anterior, middle, and posterior regions?

Pericardium

What three compartments comprise the thoracic cavity?

Pleural cavities (one for each lung) Mediasinum (shown as "pericardial cavity"

What are the components of the thoracic wall?

Posterior: Thoracic vertebrae (12) and intervertebral discs Lateral: Ribs (12), intercostal muscles Anterior: Sternum

Where is the head of a rib located?

Posteriorly

Rectus abdominis origins? (3)

Pubic crest Pubic tubercle Pubic symphysis

Describe a unique feature of Rib X.

Rib X has only one articular surface which articulates with the body of vertebra T10. (It also articulates with the transverse process of T10).

Where is the jugular notch located?

Superior border of manubrium

External Intercostal insertion?

Superior margin of rib below

Internal Intercostal insertion?

Superior margin of rib below, deep to attachment of external intercostal

What are the two apertures of the thorax?

Superior thoracic aperture Inferior thoracic aperture

What are the superior and inferior borders of the abdomen?

Superior: diaphragm Inferior: pelvis

Which structures are contained in the superior mediastinum?

Systemic Blood Vessels (e.g., Aorta, Vena Cavae) Trachea

Pyramidalis function?

Tenses linea alba

What is the angle of the rib? Where is it located?

The angle is the abrupt change in curvature of the external surface of a rib just lateral to the neck where the rib is bent in two directions and twisted along its axis.

Describe the costal groove of a rib. What structures does it house and protect?

The costal groove is located along the deep inferior margin of the rib. It houses the costal vein, artery, and nerve. The vein is superior, artery in the middle, and nerve inferior. The costal nerve is only partly protected by the costal groove and thus prone to injury.

With what structure does the inferior articular facet of a rib connect?

The inferior articular facet of a rib articulates with the superior articular facet of the thoracic vertebra of the same number as the rib; e.g., inferior articular facet of rib 7 with superior articular facet of vertebra T7. Ribs 1, 10, 11, and 12 articulate with only one vertebra.

What is the neck of a rib?

The narrowed portion just lateral to the head that connects the head to the angle.

Describe the pelvic inlet.

The pelvic inlet conceptually divides the abdominal cavity from the pelvic cavity. Its borders are formed by the bones of the os coxae, through which it passes.

What is the rectus sheath? What are its components? (3)

The rectus sheath encloses the rectus abdominis and pyramidalis muscles. It is comprised of layering aponeuroses of external oblique, internal oblique, and transversus abdominis.

With what structure does the superior articular facet of a rib connect?

The superior articular facet of a rib articulates with the inferior articular facet of the thoracic vertebra of one number lower than the rib; e.g., superior articular facet of rib 7 with inferior articular facet of vertebra T6. Ribs 1, 10, 11, and 12 articulate with only one vertebra.

Describe the tubercle of the rib and give its function.

The tubercle is a small raised area on the superior surface of the rib, just lateral to the neck. It articulates with the transverse costal facet of the vertebra of the same number as the rib

The lateral surfaces of the manubrium have an "attachment site" for Rib I. Why is this area not called an articular facet?

There is no synovial joint between Rib I and the manubrium.

Describe the sternocostal joints between Ribs II-VII and the sternum.

They are synovial joints with thin joint capsules, stabilized by sternocostal ligaments.