anat and phys lecture 13

muscles of the thoracic cage

most responsible for breathing

• diaphragm

• intercostal muscles: internal/external intercostal muscles

• scalene muscles

diaphragm

• origin: xiphoid process, lower ribs, lumbar vertebrae

• insertion: central tendon

• when activated: the diaphragm flattens out and pulls the lungs down (lungs are attached to diaphragm by the pleural membrane)

• primary function: inhalation

intercostal muscles

intercostal: between ribs

• internal and external intercostal muscles

internal intercostal muscles

run from the sternum and not that posteriorly along the rib

• origin: inferior rib

• insertion: superior rib

• when activated: compresses the rib cage, making it smaller

external intercostal muscles

runs on the ribs and posteriorly all they way to the vertebral column

• origin: superior rib

• insertion: inferior rib

• when activated: pulls the inferior rib superiorly, anteriorly, laterally → increases dimension the rib cage→ makes lungs bigger →relieves pressure in the lung → allows air to enter in the lung

scalene muscles

• origin: cervical vertebrae

• insertion: first two ribs

• when activated: contributes to increasing dimension of rib cage by lifting up the first two ribs (causing it to have the name accessory inspiratory muscles)

abdominal muscles

• hydrostatic skeleton: is created when you pressurize a fluid filled area

  • when the abdominal wall contracts it pressurizes the fluid that the peritoneal cavity contains which makes it structural so at some level the abdominal wall serves as a hydrostatic skeleton

• we use our abdominal muscles to flex the vertebral column

linea alba

connective tissue that runs in between the two rectus abdominus

rectus sheath

connective tissue that covers the rectus abdominus and where the external/internal abdominal obliques and the transverse abdominus insert onto

parietal peritoneum

the parietal peritoneum is associated with the abdominal muscles so when you compress the abdominal wall you are compressing the internal fluid of the peritoneal cavity → producing the hydrostatic skeleton

abdominal wall

• rectus abdominus

• external abdominal obliques

• internal abdominal obliques

• transverse abdominus

rectus abdominus

• origin: pubic bone

• insertion: xiphoid process and lower ribs

• when activated: flexes vertebral column and compresses abdominal wall

external abdominal obliques

• origin: ribs 5-12

• insertion: iliac crest, inguinal ligament, rectus sheath

• when activated: flexes the vertebral column and compresses the abdominal wall

internal abdominal oblique

• origin: iliac crest, inguinal ligament, lumbar fascia

• insertion: rectus sheath and lower ribs

• when activated: flexes the vertebral column and compresses the abdominal wall

transverse abdominus

• origin: iliac crest and lumbar fascia

• insertion: rectus sheath

• when activated: compresses abdominal wall

quadratus lumborum

• origin: iliac crest

• insertion: lumbar vertebrae

• when activated: flexes the vertebral column laterally