Muscular System (Part 2) - Muscles of the Neck, Back and Abdomen

Summary

This lecture segment focuses on the muscles of the neck, back, and abdomen. It covers the composition of epaxial muscles, including extensors and flexors of the neck, and four key abdominal muscles with their fiber orientations. The epaxial muscles are divided into three groups: transverso spinalis, longissimus, and iliocostalis systems. The hypoxial muscles and other flexors of the neck are also discussed. The abdominal muscles include the external and internal oblique muscles, rectus abdominis, and transversus abdominis, each with unique fiber directions contributing to the strength of the abdominal wall.

Takeaways

• 📚 The lecture focuses on the muscles of the neck, back, and abdomen.
• 🔍 Students should be able to identify the composition of epaxial muscles, other extensors and flexors of the neck, and four abdominal muscles by the end of the presentation.
• 🦴 The intrinsic muscles of the vertebral column are categorized into epaxial and hypaxial muscles.
• 📏 Epaxial muscles are positioned dorsal to the transverse process of the vertebra and function to support the spine and extend the vertebral column.
• 💪 Hypaxial muscles are located ventral to the transverse process and are responsible for flexing the neck and contributing to the flexion of the vertebral column.
• 📝 Epaxial muscles are organized into three longitudinal groups: transversospinalis, longissimus, and iliocostalis systems.
• 🔑 The transversospinalis system is the most medial and extends from the sacrum to the head.
• 🔑 The longissimus system is intermediate, the longest and strongest, extending from the ilium to the skull.
• 🔑 The iliocostalis system is the most lateral and extends from the ilium to C7, identifiable by its flat shiny tendons.
• 🦵 The flexors of the neck include the hypaxial muscles and additional muscles such as sternocephalicus, sternohyoid, sternothyroid, and scalenus.
• 🤸‍♂️ The abdominal muscles consist of the external abdominal oblique, internal abdominal oblique, rectus abdominis, and transversus abdominis, each with different fiber orientations providing strength to the abdominal wall.

Q & A

What are the two major groups of intrinsic muscles of the vertebral column?

The two major groups of intrinsic muscles of the vertebral column are the epaxial and hypoxial muscles.

What is the function of epaxial muscles?

Epaxial muscles function to support the spine, extend the vertebral column, and allow lateral flexion.

How are the epaxial muscles arranged?

Epaxial muscles are arranged in three adjacent longitudinal groups: the transverso spinalis, the longissimus system, and the iliocostalis system.

What is the role of hypoxial muscles in the vertebral column?

Hypoxial muscles are positioned ventral to the transverse process of the vertebrae and they flex the neck and tail, contributing to the flexion of the vertebral column.

Which muscle is considered the first flexor of the neck?

The first flexor of the neck is the V-shaped sternocephalicus muscle.

What are the two divisions of the sternocephalicus muscle?

The two divisions of the sternocephalicus muscle are the sternomastoidus and the sterno occipitalis.

What is the function of the sternohyoidus muscle?

The sternohyoidus muscle is a thin flat muscle that draws the basihyoid bone caudally.

How does the sternothyroid muscle contribute to neck movement?

The sternothyroid muscle draws the larynx and tongue caudally.

What is the significance of the linea alba in the abdomen?

The linea alba is a whitish longitudinal line formed by the aponeurosis of the muscles of the abdominal wall, and it is where protein laparotomies are generally performed due to its low vascularity.

How do the muscle fibers of the external abdominal oblique muscle run?

The fibers of the external abdominal oblique muscle run caudal ventrally.

What is the deepest muscle of the abdomen and in which direction do its fibers run?

The deepest muscle of the abdomen is the transversus abdominis, and its fibers run perpendicular to the long axis of the body.