A&P Chapter 12 - Muscles of the Torso

Umbilicus

"Navel" - marks the site of attachment of the umbilical cord to the fetus

Quadratus Lumborum

"hip hiker" muscle A: Bilaterally, pulls twelfth ribs inferiorly during forced exhalation, stabilizes twelfth ribs to prevent their elevation during deep inhalation, and unilaterally, flexes trunk to side elevating hip and lower limb. N: Thoracic spinal nerve

11 pairs; occupy the superficial layer and their fibers run obliquely and anteriorly from the rib above to the rib below. They elevate the ribs during inhalation to help expand the thoracic cavity.

External intercostal muscles

Rectus sheaths

Formed by the aponeuroses of the external oblique, internal oblique and transversus abdominis muscles; this encloses the rectus abdominis muscles.

Inguinal Ligament

Formed by the inferior free border of the external oblique aponeurosis plus some collagen fibers. This runs from the ASIS to the pubic tubercle.

Linea Alba

Formed by the meeting at the midline of the rectus sheaths, during the latter stage of pregnancy, this stretches to increase the distance between the rectus abdominis muscles.

External Oblique

Forms inguinal ligament A: Acting together, bilaterally, compress abdomen and flex vertebral column; acting singly (unilaterally), laterally flex vertebral column, especially lumbar portion, and rotate vertebral column. N: Thoracic spinal nerves

Structure along which hernias frequently occur

Inguinal ligament

Internal Oblique

Intermediate, flat muscle. Its fascicles extend at right angles.

11 pairs; lie deep; the fibers of these muscles are at right angles and run obliquely and posteriorly from the rib below to the rib above. They draw adjacent ribs together during forced exhalation to help decrease the size of the thoracic cavity

Internal intercostal muscles

O: Superior surface of all spinous processes I: Inferior surface of spinous process of vertebra superior to the one of origin A: Acting together, weakly extend vertebral column; acting singly, stabilize vertebral column during movement.

Interspinales

Segmental Muscles

Interspinales and Intertransversarii

O: Transverse processes of all vertebrae I: Transverse process of vertebra superior to the one of origin A: Acting together, extend vertebral column; acting singly, weakly laterally flex vertebral column and stabilize it during movements.

Intertransversarii

Diaphragm

O: Xiphoid process of the sternum; costal cartilages and portions of ribs 6-12, lumbar vertebrae and their intervertebral discs. I: Central tendon A: Contraction of the diaphragm causes it to flatten and increases the vertical dimension of the thoracic cavity, resulting in inhalation; relaxation of the diaphragm causes it to move superiorly and decreases the vertical dimension of the thoracic cavity, resulting in exhalation. N: Phrenic nerve

Spinalis capitis

O: very small or arises with Semispinalis capitis I: Occipital bone with Semispinalis A: Acting together, muscles of each region (cervical, thoracic, lumbar) extend vertebral column of their respective regions. N: Cervical and superior thoracic spinal nerves.

This separates the pelvic cavity above from the perineum below.

Pelvic diaphragm

Unite the spinous and transverse processes of consecutive vertebrae and function primarily in stabilizing the vertebral column during its movements.

Segmental muscles

Transverse line drawn between the ischial tuberosities divides the perineum into two triangles: the anterior triangle is called the

Urogenital triangle

Central tendon

A strong aponeurosis located near the center of the diaphragm, the fibers of the muscular portion converge and insert into this....

Internal Oblique

A: Acting together, compress abdomen and flex vertebral column; acting singly, laterally flex vertebral column, especially lumbar portion, and rotate vertebral column.

Rectus Abdominis

A: Flexes vertebral column, especially lumbar portion, and compresses abdomen to aid in defecation, urination, forced exhalation, and childbirth. RMA: Flexes pelvis on the vertebral column N: Thoracic spinal nerves

Transverse line drawn between the ischial tuberosities divides the perineum into two triangles: the posterior triangle is called the ...

Anal triangle

Interspinales

Between spinous processes

Intertransversarii

Between transverse processes

Hiatal Hernia

Condition in which a portion of the stomach protrudes superiorly through the esophageal hiatus.

Erector Spinae Group

Crosses many joints - AKA Sacrospinalis muscles

Transversus Abdominis

Deep "Girdle" muscle A: Compresses abdomen. N: Thoracic spinal nerves

Has three major openings through which the aorta, esophagus and inferior vena cava pass between the thorax and abdomen.

Diaphragm

The most important muscle that powers breathing

Diaphragm

Diaphragm

Dome-shaped muscle that separates the thoracic and abdominal cavities; has a convex superior surface that forms the floor of the thoracic cavity and a concave inferior surface that forms the roof of the abdominal cavity.

Largest muscle mass of the back; chief extensor of the vertebral column; run parallel with vertical axis of vertebral column

Erector Spinae muscles

Tendinous intersections

Form the "six pack" - Transverse fibrous bands of tissue that interrupt the surface of the Rectus Abdominis muscle; it is believe to be remnants of embryological development.

Amount of force; repetition; posture; stress applied to vertebral column

Four factors associated with increased risk of back injuries.

Rectus capitis posterior major; Rectus capitis posterior minor; Obliquus capitis inferior; Obliquus capitis superior

Four suboccipital muscles

Transverospinalis

Goes from lateral to medial and crosses 2-4 joints

Rectus Abdominis

Has tendinous intersections - "six pack" muscle. Long muscle that extends the entire length of the anterior abdominal wall; its anterior surface is interrupted by three or more transverse fibrous band of tissue.

Lateral Erector Spinae muscles

Iliocostalis cervicis, Iliocostalis thoracis, Iliocostalis lumborum

Largest and most important muscle of the pelvic floor; it supports the pelvic viscera and resists the inferior thrust that accompanies increases in intra-abdominal pressure during functions such as forced exhalation, coughing, vomiting, urination and defecation.

Levator Ani

Intermediate Erector Spinae muscles

Longissimus capitis, Longissimus cervicis, Longissimus thoracis

External Oblique

Most superficial muscle of the abdominal wall - forms inquinal ligament

Iliocostalis thoracis, Iliocostalis lumborum, Longissimus cervicis, Longissimus thoracis, Spinalis thoracis, Semispinalis cervicis, Semispinalis thoracis, Multifidous, Rotatores

Muscles of the Posterior Torso

Help contain and protect the abdominal viscera; flex, laterally flex, and rotate the vertebral column at the intervertebral joints; compress the abdomen during forced exhalation; and produce the force required for defecation, urination or childbirth.

Muscles of the anterolateral abdominal wall

Pelvic Diaphragm

Muscles of the pelvic floor are the levator ani and ischiococcygeus; together with the fascia covering their internal and external surfaces, these muscles are referred to as the .......which stretches from the pubis anteriorly to the coccyx posteriorly, and from one lateral wall of the pelvis to the other.

Semispinalis capitis

O: Articular processes of C4-C6 and transverse processes of C7-T7 I: Occipital bone A: Acting together, extend head; acting singly, rotate head to side opposite contracting muscle N: Cervical and thoracic spinal nerves

Longissimus capitis

O: Articular processes of C4-C7 and transverse processes of T1-T4 I: Mastoid process of temporal bone A: Acting together, both muscles extend head; acting singly, rotate head to same side as contracting muscle. N: Middle and inferior cervical spinal nerves.

Iliocostalis lumborum

O: Iliac crest I: Ribs 7-12 A: Acting together, muscles of each region (cervical, thoracic and lumbar) extend and maintain erect posture of vertebral column of their respective regions; acting singly, laterally flex vertebral column of their respective regions to the same side as the contracting muscle. N: Lumbar spinal nerves.

External Intercostals

O: Inferior border of rib above I: Superior border of rib below A: Contraction elevates the ribs, resulting in inhalation. Relaxation depresses the ribs, resulting in exhalation. N: Thoracic spinal nerves.

Ischiococcygeus

O: Ischia spine I: Lower sacrum and upper coccyx A: Supports and maintains position of pelvic viscera; resists increase in intra-abdominal pressure during forced exhalation, coughing, vomiting, urination and defecation; pulls coccyx anteriorly following defecation or childbirth. N: Sacral spinal nerves S4-S5

Levator Ani - Iliococcygeus

O: Ischial spine I: Coccyx A: Supports and maintains position of pelvic viscera; resists increase in intra-abdominal pressures during forced exhalation, coughing, vomiting, urination and defecation; constricts anus, urethra and vagina. N: Sacral spinal nerves.

Spinalis cervicis

O: Ligamentum nuchae and spinous process of C7 I: Spinous process of axis A: Acting together, muscles of each region (cervical, thoracic and lumbar) extend vertebral column of their respective regions. N: Inferior cervical and thoracic spinal nerves.

Splenius capitis

O: Ligamentum nuchae and spinous processes of C7-T4 I: Occipital bone and mastoid process of temporal bone. A: Acting together (bilaterally), extend head; acting singly (unilaterally), laterally flex and/or rotate head to same side as contracting muscle. N: Middle cervical spinal nerves.

Rectus capitis posterior minor

O: Posterior tubercle of the atlas (C1) I: Medial third of inferior nuchal line A: Extend or retract head N: Dorsal ramus of C1 (suboccipital nerve)

Levator Ani - Pubococcygeus

O: Pubis and ischial spine I: Coccyx, urethra, anal canal, perineal body of perineum and anococcygeal ligament A: Supports and maintains position of pelvic viscera; resists increase in intra-abdominal pressures during forced exhalation, coughing, vomiting, urination and defecation; constricts anus, urethra and vagina. N: Sacral spinal nerves

Iliocostalis cervicis

O: Ribs 1-6 I: Transverse processes of C4-C6 A: Acting together, muscles of each region (cervical, thoracic, and lumbar) extend and maintain erect posture of vertebral column of their respective regions; acting singly, laterally flex vertebral column of their respective regions to the same side as the contracting muscle. N: Cervical and thoracic spinal nerves

Iliocostalis thoracis

O: Ribs 7-12 I: Ribs 1-6 A: Acting together, muscles of each region (cervical, thoracic and lumbar) extend and maintain erect posture of vertebral column of their respective regions; acting singly, laterally flex vertebral column of their respective regions to the same side as the contracting muscle. N: Thoracic spinal nerves

Multifidus

O: Sacrum; ilium, transverse processes of lumbar, thoracic and C4-C7 I: Spinous process of a more superior vertebrae A: Acting together, extend vertebral column; acting singly, weakly laterally flex vertebral column and weakly rotate vertebral column to side opposite contracting muscle. N: Cervical, thoracic and lumbar spinal nerves.

Obliquus capitis inferior

O: Spinous process of the axis (C2) I: Above the insertion of rectus capitis posterior major A: Acting together, extend or tilt head; acting singly, rotate and/or laterally flex head to same side. N: Dorsal ramus of C1 (suboccipital nerve)

Rectus capitis posterior major

O: Spinous process of the axis (C2) I: Middle third of inferior nuchal line A: Acting together, extend head; acting singly, rotate head to same side. N: Dorsal ramus of C1 (suboccipital nerve)

Spinalis thoracis

O: Spinous processes of T10-L2 I: Spinous processes of superior thoracic vertebrae A: Acting together, muscles of each region (cervical, thoracic and lumbar) extend vertebral column of their respective regions. N: Thoracic spinal nerves.

Splenius cervicis

O: Spinous processes of T3-T6 I: Transverse processes of C1-C2 or C1-C4 A: Acting together, extend head; acting singly, laterally flex and/or rotate head to same side as contracting muscle. N: Inferior cervical spinal nerves.

Internal Intercostals

O: Superior border of rib below I: Inferior border of rib above. A: Contraction draws adjacent ribs together to further decrease the anteroposterior and lateral dimensions of the thoracic cavity during forced exhalation. N: Thoracic spinal nerves.

Semispinalis cervicis

O: Transverse processes of T1-T5 I: Spinous processes of C1-C5 A: Acting together, both this muscle and Semispinalis thoracis extend vertebral column of their respective regions; acting singly, rotate head to side opposite contracting muscle. N: Cervical and thoracic spinal nerves.

Longissimus cervicis

O: Transverse processes of T4-T5 I: Transverse processes of C2-C6 A: Acting together, this muscle, along with the longissimus thoracis muscles extend vertebral column of their respective regions; acting singly, laterally flex vertebral column of their respective regions. N: Cervical and superior thoracic, spinal nerves.

Semispinalis thoracis

O: Transverse processes of T6-T10 I: Spinous processes of C6-T4 A: Acting together, both Semispinalis cervicis and this muscle extend vertebral column of their respective regions; acting singly, rotate head to side opposite contracting muscle. N: Thoracic spinal nerves

Rotatores

O: Transverse processes of all vertebrae I: Spinous process of vertebra superior to the one of origin. A: Acting together, weakly extend vertebral column; acting singly, weakly rotate vertebral column to side opposite contracting muscle. N: Cervical, thoracic and lumbar spinal nerves.

Longissimus thoracis

O: Transverse processes of lumbar vertebrae I: Transverse processes of all thoracic and superior lumbar vertebrae and ribs 9 and 10 A: Acting together, lumbar cervicis and this muscle extend vertebral column of their respective regions; acting singly, laterally flex vertebral column of their respective region. N: Thoracic and lumbar spinal nerves

Formed by the lumbar vertebrae, parts of the ilia of the hip bones, psoas major and Iliacus muscles and the quadratum lumborum; this wall is bulky and stable.

Posterior abdominal wall

"Six pack" effect

Rectus abdominis muscles segmented by fibrous bands that run transversely or obliquely across the rectus abdominis muscle called tendinous intersections. Body builders focus on the development of these muscles for this....

Suboccipital muscles (craniovertebral joint muscles)

Rectus capitis posterior major, Rectus capitis posterior minor, Obliquus capitis inferior, Obliquus capitis superior

Opposite side Rotators of the Head

SCM, Semispinalis capitis, Semispinalis cervicis

Cross a single joint; Interspinales, Intertransversarii

Segmentals

Transversospinales Muscles

Semispinalis capitis, Semispinalis cervicis, Semispinalis thoracis, Multifidus, Rotatores

Medical Erector Spinae muscles

Spinalis capitis, Spinalis cervicis, Spinalis thoracis

Same side Rotators of the Head

Splenius capitis, Iliocostalis cervicis, Longissimis capitus

Muscles which are a common source of headaches

Suboccipital muscles

Pubococcygeus and iliococcygeus

The two components of the levator ani muscle.

Cross at least two or more joints

Transversospinales muscles

So named because their fibers run from the transverse processes to the spinous processes of the vertebrae, extend, laterally flex, and rotate the vertebral column and rotate the head

Transversospinales muscles

Short "Leg" Syndrome

Unilateral chronic contraction (spasm) of the quadratus lumborum muscle will elevate the pelvis on the same side, thus giving the muscle its nickname, "the hip hiker." When the pelvis is elevated on one side, its causes the lower limb of that side to elevate, thus leading to a functional "leg length discrepancy" (LLD)

This abdominal wall can contract and distend

anterolateral abdominal wall