Gross Human Anatomy Exam 4

Pelvic Region Borders

=> superior: pelvic inlet

=> inferior: pelvic outlet/pelvic diaphragm

=> pelvic brim divides superior greater pelvis from inferior lesser (true) pelvis

Pelvic Region Osteology

=> made up of 8 bones in childhood and 4 in adulthood

=> os coxa, sacrum, coccyx

=> os coxa: ilium, ischium, pubis (fused in adulthood)

Human Traits of Pelvis

=> bipedalism: bowl-like pelvis to support organs/narrow/rotates the iliac crest laterally so smaller gluteals become hip stabilizers (prevents side-to-side swaying during walking)/gluteus maximums provides spring for running

=> head to outlet ratio: human heads are larger than bipedal pelvises

Gluteus Maximus Function

=> pulls the leg backward, critical for human running

=> a hip extender

Gluteus Medius/Minimus Function

=> stabilize the hip and upper body during walking

Pelvis and Birthing

=> human offspring must be born before skull formation is complete in order to pass through the pelvis (it must pass through the pelvic inlet oriented to the side, head first)

=> to compensate, pelvises widen under the influence of estrogen

=> similarly, they narrow progressively during menopause

Pelvis Joints

=> anterior/posterior sacroiliac ligaments laterally attach ilium and sacrum

=> iliolumbar ligament is the superior/inferior attachment between ilia and transverse process of L5

=> sacrospinous attaches sacrum to ischial spine (weight-bearing)

=> sacrotuberus attaches sacrum to ischial tuberosities (weight-bearing)

=> anterior/posterior sacrococcygeal ligaments attach sacrum to coccyx

Pelvic Floor Muscles

=> “sump pump” contractions of these muscles move lymph/venous blood within the lymphatic circulation/veins (moving fluid against gravity)

=> sphincteric role for urethra/anus

=> support for the abdominal/pelvic viscera

Pelvic Floor Tearing

=> up to 80% of individuals post-vaginal birth experience tearing of pelvic floor muscles

Urethra in Penis

=> transports urine/semen

=> 18-20 cm

=> divided into three zones: prostatic (extends through prostate gland), membranous (external urethra sphincter), spongy (encased within erectile tissue)

Bladder Features

=> trigone: triangle shaped space between ureter orifices-location of stretch receptors that trigger the urge to urinate

Urethra in Vagina

=> transports urine

=> 3 cm (more prone to UTIs)

Pelvis and Pregnancy

=> weight-bearing stress placed on pubic symphysis during pregnancy

=> volume reduction of urinary bladder and stomach

=> limitation of diaphragm contraction

Acetabulum

=> joint made up of the ilium, ischium, and pubis

Lumbar Plexus L1-4

=> primarily innervates the: abdominal wall muscles, the anterior thigh muscles, and the medial thigh muscles

Iliohypogastric

=> L1 and T12 fibers

=> innervates internal oblique and transversus abdominus

=> sensory innervation in pubic region

Ilioinguinal

=> L1

=> innervates internal oblique and transversus abdominus

=> sensory innervation in pubic region

Genitofemoral

=> L1 and L2

=> innervates sensory to genitalia and upper anterior thigh

Lateral Femoral Cutaneous

=> L2 and L3

=> innervates sensory for skin of the anterio-lateral thigh

Femoral

=> L2 - L4

=> innervates hip flexors/knee extensors

=> sensory innervation to anterior thigh and medial leg

Obturator

=> L2 - L4

=> innervates adductor muscles and skin over medial thigh

Sacral Plexus L4-5 & S1-4

=> primarily innervates posterior comp. thigh muscles, buttock, all of the leg and foot below the knee except the medial cutaneous leg

=> major nerves include sciatic and pudendal

=> most nerves pass through the greater sciatic foramen

Sciatic Nerve

=> largest nerve in the body (2 cm wide)

=> L4-S3

=> innervates the posterior thigh muscles, all leg and foot muscles, all joints of the lower limb

=> made of two nerves joined in a connective tissue sheath (common fibular and tibial)

Pudendal Nerve

=> main nerve of the perineum and genitalia

=> S2-S4

=> exits pelvis posteriorly through greater sciatic foramen then reenters anteriorly through lesser sciatic foramen

Hip Joint Stability

=> more stable than the shoulder due to…

=> acetabular labrum

=> joint capsule

=> shape of articulating surfaces

=> extrinsic ligaments (iliofemoral, pubofemoral, ischiofemoral)

=> intrinsic ligaments (ligamentum teres, transverse acetabular ligament)

Hip Ligaments

=> ilofemoral: prevents excessive extension

=> pubofemoral ligament: prevents excessive abduction

=> ischiofemoral: provides stability during extension/limits excessive internal rotation and adduction w/ flexion

Thigh Muscles (primarily) Acting Hip + Function

=> iliopsoas (FLEXION)

=> sartorius (FLEXION)

=> tensor fascia latae/IT band (ABDUCTION)

=> pectineus (ADDUCTION)

=> adductor longus/brevis/magnus (ADDUCTION)

=> gracilis (ADDUCTION)

=> gluteus medius/minimus/maximus (EXTENSION/MEDIAL ROTATION)

=> piriform/inferior and superior glemellus/obturator internus and externus/quadriceps femorus (LATERAL ROTATION)

Hip Abductors

=> tensor facia latae + IT band tract: major abductor, some flexion contribution

=> gluteus medius/minimus: major abductor, medial rotation

Hip Stabilizers

=> muscles on the lateral/posterior sides of the hip joints

=> reduces risk of injury in lower joints

Hip Extensors

=> gluteus maximus: major extensor, some lateral (external) rotation

=> the hamstring muscles are primarly knee flexors, but can also contribute

Deep Lateral Rotator of Femur

=> piriformis

=> superior gemellus

=> obturator internus

=> inferior gemellus

=> obturator externus

=> quadratus femoris

Hip Flexor

=> iliopsoas: primary hip flexor formed by iliacus and psoas major (in people who sit all day, it can become tight, pulling the illiac crest forward even when standing)

=> sartorius: hip flexion, crosses lateral to medial and inserts on medial tibia, also contributes to knee flexion, especially in sitting

=> other contributors: tensor fascia lata, pectineus, adductor longues… anything that passes over the hip joint on the ANTERIOR side

HIp Adductors

=> pectineus

=> adductor magnus: posterior head that crosses the hip joint on the posterior side, also a hip extensor/anterior head that crosses the hip joint on the anterior side, also a hip flexor

=> adductor brevis

=> adductor longus

=> gracilis