Chapter 10 (3)

• Other muscles that contribute to breathing are; Neck muscles (sternocleidomastoid and scalenes), Chest muscles (pectoralis major, and serratus anterior), Back muscles (latissimus dorsi), Abdominal muscles (internal and external obliques as well as transverse abdominis), AND Anal muscles.
• The diaphragm is a muscular dome between the thoracic and abdominal cavities. Here muscle fascicles extend to a fibrous central tendon and contraction flattens the diaphragm which enlarges the thoracic cavity (inspiration). The diaphragm rises when it relaxes which shrinks the thoracic cavity (expiration).
• External intercostals elevate ribs, expand the thoracic cavity, and create a partial vacuum causing an inflow of air. WHILE Internal intercostals depress and retract the ribs, compress the thoracic cavity, and expel air.
• The external abdominal oblique is the external layer of lateral abdominal muscles that support viscera and aid in breathing, and unilateral contraction causes contralateral rotation of the waist.
• The internal abdominal oblique is the intermediate layer of lateral abdominal muscles. The unilateral contraction causes ipsilateral rotation of the waist. It has aponeuroses that connect to tendons of oblique and transverse muscles and have broad, fibrous sheets.
• The transverse abdominal is the deepest of the lateral abdominal muscles. It has horizontal fibers, compresses abdominal contents, and contributes to movements of the vertebral column.
• The Rectus abdominis flexes the lumbar region of the vertebral column, produces forward bending at the waist, and extends from the sternum to pubis. The rectus sheath encloses muscle and three transverse tendinous intersections divide rectus abdominis into segments, sometimes called a “six-pack”.
• Muscles of the Anterior Abdominal Wall include; External abdominal oblique, Internal abdominal oblique, Transverse abdominal, and Rectus abdominis.
• The muscles of the back have actions that involve the extension, rotation, and lateral flexion of the vertebral column, AND Upper limb movement. The most prominent superficial back muscles are the latissimus dorsi and the trapezius.
• The muscles of the pelvic floor are layers of muscles and fasciae that span the pelvic outlet and are penetrated by the anal canal, urethra, and vagina.
• The perineum is the diamond-shaped region between the thighs, is bordered by four bony landmarks (the pubic symphysis (anteriorly), ischial tuberosities (laterally), and the coccyx (posteriorly)), has the Urogenital triangle which is the Anterior half of perineum, and the Anal triangle which is the Posterior half of perineum.
• Layers or compartments of the perineum include; Superficial perineal space, Deep perineal space, Anal triangle, Pelvic diaphragm, and Levator ani.
• Superficial perineal space is made up of the ischiocavernosus and the bulbospongiosus. Deep perineal space consists of the urogenital triangle which contains deep transverse perineal muscle and compressor urethrae in females. Anal triangle includes the external anal sphincter. Pelvic diaphragm is the deepest (most superior) layer. AND Levator ani supports viscera and defecation.
• A hernia is any condition in which the viscera protrudes through a weak point in the muscular wall of the abdominopelvic cavity.
• Types of hernias include; (1) the inguinal hernia which is the most common type of hernia (rare in women) as the viscera enter inguinal canal or even the scrotum. (2) Hiatal hernia where the stomach protrudes through the diaphragm into the thorax and it happens in overweight people over 40. (3) Umbilical hernia where the viscera protrude through the navel.
• Compartments are spaces where muscles are separated by fibrous connective tissue sheets (fasciae). Each compartment contains one or more functionally related muscles along with their nerve and blood supplies.
• Muscles of the upper limbs are divided into anterior and posterior compartments and intermuscular septa (thick fascia) separates these compartments.
• Compartment syndrome may occur when a blood vessel in a compartment is damaged due to things like blood and tissue fluid accumulation, fasciae being enclosed in muscle compartments and preventing expansion, or mounting pressure that obstructs blood flow to the compartment. After 2 to 4 hr of inadequate blood flow (ischemia), the nerves begin to die, and after 6 hrs the muscles begin to die. Nerves can regenerate, but muscle damage is permanent. Myoglobin in urine indicates compartment syndrome.
• The treatment for compartment syndrome is immobilization of the limb and fasciotomy (incision to relieve compartment pressure).