Mm. of Trunk Flashcards
Epaxial Muscles
lie dorsal to the transverse processes or axial skeleton
hypaxial muscles
- lie ventral to the transverse processes of the vertebrae.
- include mm of neck, thorax, and abdomen & those directly ventral to the vertebrae
divisions of neck & trunk muscles
- Epaxial mm.
2. Hypaxial mm.
Hypaxial mm.
Sternocephalicus m., sternohyoideus m., sternothyroideus m., Scalenus m., Intercostal mm., External Abdominal Oblique m., Internal Abdominal Oblique m., Transversus Abdominus m., Rectus Abdominus m.,
Sternocephalicus mm.
O: cranial sternum
I: Mastoid process & occipital bone
A: draw head/neck sideways or ventrally if both contract simulateously
form ‘v-shaped’ m. when viewed cranially. lie immediately ventral to external jugular veins.
Sternohyoideus m.
O: cranial sternum
I: Basihyoid bone (on the midline, cranial to larynx) [cranial to larynx]
A: pull tongue & larynx caudally (swallowing)
Sternothyroideus m.
O: cranial sternum
I: Thyroid cartilage of larynx (lateral surface of larynx)
A: pull the tongue & larynx caudally (swallowing)
Why are the sternohyoideus & sternothyroideus mm. grouped together?
They originate as a single common m. and separate into individual mm. a few cm from the 1st sternebra.
Thyroid glands
dark red, elongated structures that lie lateral to cranial portion of trachea
Scalenus m.
Triangular m. that lies ventral to serratus ventralis m.
O: Last 3 cervical vertebrae
I: 1st few ribs
A: “Anchors” cranial ribs during inspiration
Intercostal mm. types
External intercostal m.
Internal intercostal m.
External intercostal mm.
more superficial intercostal mm. & fibers run caudoventrally.
Internal intercostal mm.
lie deep to external intercostal mm.
fibers run cranioventrally.
Intercostal mm. OIA
O: Caudal border of 1 rib
I: Cranial border of the next
A: Pull ribs closer together
12 pairs exist on each side
External Abdominal Oblique m.
Most superficial m. of lateral abdominal wall. Runs caudoventrally. BIGGEST abdominal gp m.
O: Caudal ribs & thoracolumbar fascia
I: Ventral midline
A:
Internal Abdominal Oblique mm.
O: Thoracolumbar fascia, Tuber Coxae, Inguinal Ligament,
I: Aponeurosis (last rib/costal arch [outer rim] & linea alba
fibers run cranioventrally (to manus)
Transversus Abdominus M.
O: Thoracolumbar fascia
I: Aponeurosis - dorsal to rectus femoris everywhere except very caudal, where its ventral too
fibers run ventral in a transverse plane. deepest m. of abdominal wall
Rectus Abdominus M.
O: Sternum & 1st few ribs via an aponeurosis
I: Pectin of pubis
R/L mm. lie adjacent to each other on ventral midline (linea alba).
Tendinous bands give more control over contraction (give 6 pack look in ppl).
Linea Alba
“White Line”
relatively avascular. holds sutures well.
therefore, its a common site for abdominal incisions.
Epaxial mm.
Iliocostalis System., Longissimus System, Transversospinalis System, Splenius m.,
Transversospinalis System
Sit medial & dorsal on vertebral column.
Caudal extent: sacrum & ilium
Cranial extent: skull
Longissimus system
lateral and ventral to transversospinalis system.
Caudal Extent: Ilium
Cranial Extent: Skull
Iliocostalis System
shortest system. lateral most & ventral most system.
Caudal Extent: Ilium
Cranial Extent: Ribs
Epaxial Systems’ Functions
- extend vertebral column (both sides contract)
- pull side over (lateral flexion) [only one side contracts]
Splenius m.
O: Spinous processes of cranial thoracic vertebrae, dorsal midline of the neck.
I: Caudodorsal border of the skull
Nuchal Ligament
2 bands of elastic connective tissue
Run from cranial extent of the supraspinous ligament to the axis (yellow in color)
Inguinal Lig.
Thickened caudal border of aponeurosis of external abdominal oblique m.
not technically a lig. it just protects the muscles.
Muscles that form the Abdominal Wall
Rectus Abdominis m., Transverses Abdominis m., Internal Abdominal Oblique m., External Abdominal Oblique m.
“Abdominal Press”
the smoother & more uniform the more effective the contraction of all the muscles is.
Why is it important to know the muscle fiber’s directions?
- protection
- identification of muscles
- contraction direction
Why do the fibers of the 4 muscles in the abdominal walls run different directions?
creates a meshwork which give strength to them. Meshwork makes abdominal m. group smoother and more uniform.
Diaphragm
Attaches to caudal rib area.
Separates thoracic and abdominal cavities.
The relaxed m. is pushed cranially by organs of abdominal cavity.
Order of Epaxial Muscles from Dorsal to Ventral
“Ten Little Indians”
- Transversospinalis system
- Longissimus system
- Iliocostalis system
Flexor angle of vertebral jts.
ventral side.
Superficial Inguinal Ring
A slit in aponeurosis of insertion of external ab. oblique m.
Location: medial to vessels of femoral triangle.
Male dog: spermatic cord, external pudendal vessels leave/enter here.
Female dog: fat-filled sack (Vaginal Process) & external pudendal vessels leave/enter here.
Vaginal Process
blind-ended, fat-filled sack that passes through superficial inguinal ring in females.
equivalent to vaginal tunic extension in males
Vaginal Tunic
covers the spermatic cord and testes.
