Lecture 14: Skeletal Muscles Trunk Flashcards
Muscles of the back
3 layers: superficial, intermediate, deep
Superficial and intermediate layers = extrinsic back muscles
Deep layer = intrinsic back muscles
Superficial back muscles
Trapezius
Latissimus dorsi
Levator scapulae
Rhomboid
Function: connects upper limb to trunk and positions pectoral girdle and upper limb
Innervated by anterior/ventral rami of spinal nerves
Intermediate back muscles
Serratus posterior superior
Serratus posterior inferior
Function: accessory respiratory muscles
Innervated by ventral rami of spinal nerves
Deep back muscles
Erector spinae
Transversospinalis
Segmental muscle groups
Splenius wapitis
Cervicis
Function: maintains erect position of trunk and neck, extends and rotates vertebral column, extends/laterally flexes vertebral column, elevates ribs, extends and rotates head/neck
Innervated by dorsal rami of spinal nerves
Trapezius
Origin: occipital bone, spinous process from all cervical and thoracic vertebrae
Insertion: clavicle, acromian, spine of scapula
Function: upper fibers (down and lateral) elevate shoulders, middle fibers (horizontal) retract/adduct scapula, lower fibers (superior and lateral) depress scapula
Nerve: CNXI (accessory)
Latissimus dorsi
Origin: spinous process of lower thoracic and lumbar vertebrae, sacral and iliac crests
Insertion: intertubercular groove of humerus
Function: prime mover of shoulder extension; adduction, medial rotation of shoulder
Nerve: thoracodorsal nerve of brachial plexus
Levator scapulae
Origin: upper cervical vertebrae
Insertion: superior angle of scapula
Function: elevation of scapula
Nerve: branch of brachial plexus
Rhomboid (major and minor)
Origin: thoracic vertebrae
Insertion: medial border of scapula
Function: retraction and elevation of scapula
Nerve: branch of brachial plexus
Erector spinae
3 longitudinal bundles of muscles fibers (from lateral to medial): iliocostalis, longissimus, spinalis
Function: maintains erect position of trunk and neck, extends and rotates vertebral column, stabilizes vertebral column
Nerve: dorsal rami of spinal nerves
Transversospinalis
Between transverse process and spinous process of vertebrae
Subdivided (from superficial to deep): semispinalis, multifidus, rotatores
Function: maintains erect position of trunk and neck, extends and rotates vertebral column, stabilizes vertebral column
Nerve: dorsal rami of spinal nerves
Segemental group
From medial to lateral: interspinales, intertransversarii, elevator costarum
Function: extends or laterally flexes vertebral column, elevates ribs
Nerve: dorsal rami of spinal nerves
Splenius capitis and cervicis
Extend and rotates the neck/head
Nerve: dorsal rami of spinal nerves
Muscles of thorax (extrinsic and intrinsic)
2 groups:
Extrinsic muscles originate in thorax, and insert to upper limb: pectoralis major, pectoralis minor, serrates anterior, subclavius muscle
Intrinsic muscles originate and insert to thorax: intercostal muscles and diaphragm
Pectoralis major
Origin: clavicle and costal cartilage of upper fibers
Insertion: proximal end of humerus
Function: medial rotation and adduction of shoulder; accessory respiratory muscle
Nerve: branch of brachial plexus
Pectoralis minor
Origin: ribs 3-5
Insertion: corocoid process of scapula
Function: brings tip of shoulder anteriorly and inferiorly
Nerve: branch of brachial plexus
Serratus anterior
Origin: ribs 1-9
Insertion: anterior medial border of scapula
Function: prime mover for protraction of scapula, stabilizes scapula against chest wall (if paralyzed, scapula will be unstable and 7-8 other muscles that depend on scapula will also lose function)
Nerve: long thoracic nerve of brachial plexus (close to breast gland)
Intercostal muscles
Muscles between adjacent ribs
3 layers (from superficial to deep): external intercostal, internal intercostal, innermost intercostal
Function: helps with respiration by increasing/decreasing thoracic cavity volume during inhalation and exhalation
Nerve: intercostal nerves
Diaphragm
Origin: xiphoid process, lower 6 ribs, lumbar vertebrae
Insertion: central tendon (dense connective tissue in the centre)
Function: increase volume and decrease pressure of chest (decrease volume and increase pressure of abdomen) for breathing, using the bathroom, coughing, sneezing
Nerve: phrenic nerve of cervical plexus
*if not well developed during embryonic stage, some abdominal organs may herniate from diaphragm to chest
Major openings in the diaphragm
Inferior vena cava opening (TVIII) Esophageal hiatus (TX) Aortic opening (TXII)
Muscles of abdomen
2 group:
Anterolateral - flexes and rotates trunk, increases abdominal cavity pressure
Posterior - extends and laterally flexes trunk, or flexes and lateral rotates the hip
External oblique
Most superficial Origin: lower ribs and hip bone Insertion: linea alba Function: contralateral rotation of trunk Nerve: lower intercostal nerve **Origin moves towards the insertion
Internal oblique
Origin: hip bone and inguinal ligament
Insertion: linea alba and lower rips
Function: ipsilateral rotation of trunk
Nerve: lower intercostal nerves
Transversus abdominis
Origin: hip and lower ribs
Insertion: linea alba
Function: compresses abdominal viscera and increasing abdominal pressure to help the diaphragm
Nerve: lower intercostal nerves
Rectus abdominis
Origin: pubic bone
Insertion: xiphoid process of sternum, and ribs 5-7
Function: flexion of trunk
Nerve: lower intercostal nerves
Has horizontal bands = tendinous intersection to divide it into smaller segments (determines how many packs we have)
Aponeurosis
Sheet like tendon that attaches anterolateral abdominal muscles to insertion
Inguinal ligament
Inferior border of aponeurosis of external abdominal oblique
Stretched between anterior superior iliac spine and pubic tubercle
Rectus sheath
Fibrous sheath by aponeurosis of external, internal, and transverse abdominis muscle
Almost completely invests rectus abdominis muscle
Linea alba
Dense connective tissue by union of aponeuroses of anterolateral abdominal muscles in midline
Between xiphoid process and pubic symphysis
Inguinal canal
Short oblique canal above medial half of inguinal ligament
Between external, internal and transverses abdominis muscles
Has 2 openings: deep and superficial inguinal rings
Contains spermatic cord (males) or round ligament of uterus (females)
Muscles of pelvis
Classified as pelvic wall muscles, pelvic diaphragm, perineal muscles
Pelvic wall muscles
Piriformis
Obturator interns
Originate in pelvic cavity, insert to femur
Pelvic diaphragm
Levator ani
Coccygeus muslces
Form funnel shaped membrane between true pelvis and perineum
Supports pelvic viscera (uterus, rectum, bladder)
Levator ani
Origin: inner surface of hip bone
Insertion: anterior fibers merge with the opposite side, posterior fibers insert to sacrum and coccyx
Forms muscular bulb
Function: supports weight of pelvic viscera
Nerve: branch of sacral plexus
Coccygeus
Origin: ischial spine
Insertion: coccyx, sacrum
Function: supports weight of pelvic viscera
Nerve: branch of sacral plexus
Weak point of pelvic diaphragm
Anterior part of the floor where 3 structures pass through (from anterior to posterior): urethra, vaginal canal, anal canal
All very close to each other
Prolapsis
Some pelvic viscera may displace inferiorly though pelvic diaphragm
Mainly in females after child birth
Muscle fibers are not replaced, instead you get dense connective tissue that is plastic instead of elastic
Perineal muscles
Contained within perineum (between coccyx, pubic symphysis, ischial tuberosities)
Reinforces pelvic diaphragm immediately
below the weakest point
Nerve: pudendal nerve of sacral plexus
*Damage = increased chance of UTI, no erectionn, loss of control of urination/defecation
Urogenital triangle
Contains distal part of urethra, external genitalia, perineal muscles (except anal sphincter)
Contains bulbospongiosus, ischiocavernosus
Bulbospongiosus
Drains last drops of urine, joined at midline to cover base of penis (male)
Sphincter for vaginal opening, surround vagina (does not join) (female)
Nerve: pudendal nerve of sacral plexus
Ischiocavernosus
Maintains erection of penis or clitoris
Nerve: pudendal nerve of sacral plexus
Anal triangle
Contains anal canal surrounded by external anal sphincter
External anal sphincter
Controls passage of fecal material
Nerve: pudendal nerve of sacral plexus
