PELVIS

PELVIS STUDY NOTES

Bony Pelvis Overview

  • Components:

    • Pelvic Bones

    • Sacrum

    • Coccyx

    • Sacroiliac Joints

    • Pubic Symphysis

Sacrum Structure

  • Base of Sacrum

    • Sacral Promontory: The anterior projection of the first sacral vertebra that forms the anterior border of the pelvic inlet.

    • Ala of Sacrum: The lateral parts of the sacrum, aiding in forming the sacroiliac joints.

    • Apex of Sacrum: The distal end of the sacrum, articulating with the coccyx.

  • Pelvic (Anterior) Surface:

    • Anterior Sacral Foramina: Openings for the passage of nerves and vessels.

  • Dorsal (Posterior) Surface:

    • Posterior Sacral Foramina: Openings equivalent to anterior foramina located posteriorly.

    • Median Sacral Crest: A vertical ridge along the dorsal surface, formed by the fused spinous processes of sacral vertebrae.

    • Intermediate Sacral Crests: Located lateral to the median crest, formed by the fused articular processes.

    • Lateral Sacral Crests: Forms from the transverse processes of sacral vertebrae.

  • Sacral Canal: The continuation of the vertebral canal within the sacrum.

  • Sacral Hiatus: A gap at the lower end of the sacral canal where the last sacral vertebra fails to close.

Types of Pelvis

  • Greater Pelvis (False Pelvis): Superior parts of pelvic bones.

  • Lesser Pelvis (True Pelvis): Inferior parts of pelvic bones. Includes sacrum, coccyx, pelvic inlet, and outlet.

Pelvic Inlet Structure

  • Boundaries and components:

    • Sacral Promontory

    • Ala of the Sacrum (Anterior Border)

    • Arcuate Line: Curved line on the inner surface of the ilium.

    • Pecten Pubis (Pectineal Line): Continuous with the arcuate line and forms the anterior boundary of the pelvic inlet.

    • Pubic Symphysis (Superior Border): Joint connecting the left and right pubic bones.

Differences Between Male and Female Pelvic Inlet

  • Female Pelvic Inlet:

    • Shape: Circular or transverse oval.

    • Orientation: More anteroposteriorly than in males.

    • Iliac Wings: Less flared.

    • Pubic Arch: Wider with a smaller subpubic angle.

    • Dimensions: Measurements shorter in relation to body size.

  • Male Pelvic Inlet:

    • Shape: Heart-shaped.

    • Orientation: More horizontally oriented.

Pelvic Outlet Structure

  • Components:

    • Pubic Symphysis (Inferior Border)

    • Ischiopubic Ramus

    • Ischial Tuberosity

    • Sacrotuberous Ligament:

    • Tip of Coccyx

  • Diameters of pelvic outlet:

    • Transverse Diameter

    • Oblique Diameter

    • Strait Conjugate (Conjugate Recta): Typically diamond-shaped.

Planes of the Pelvis

  • Pelvic Inlet

    • Conjugate Diameter: Roughly 11extcm11 ext{ cm}.

    • Transverse Diameter: Approximately 13extcm13 ext{ cm}.

    • Oblique Diameter: Around 12.5extcm12.5 ext{ cm}.

  • Pelvic Outlet

    • Anteroposterior Diameter: Ranges from 9.5extcm9.5 ext{ cm} to 11.5extcm11.5 ext{ cm}.

Pelvic Inclination

  • The angle of the pelvis is typically between 50−60exto50 - 60^ ext{o}.

Axis of Pelvis

  • The axis defines the orientation and relationship of pelvic structures.

Pelvic Walls and Muscles

  • Components:

    • Obturator Internus Muscle: Important for lateral rotation of the thigh; exits through the lesser sciatic foramen.

    • Piriformis Muscle: Originates from the sacrum and exits through the greater sciatic foramen.

    • Pelvic Diaphragm: Consists of levator ani and coccygeus muscles, providing support to pelvic organs.

Muscles of the Pelvic Floor

  • Levator Ani Muscles (Urogenital hiatus):

    1. Puborectalis

    2. Pubococcygeus

    3. Iliococcygeus

  • Function: Support pelvic organs and maintain continence.

  • Coccygeus Muscles: Located posterior to levator ani, assisting in pelvic support.

Joints of the Pelvis

  • Pubic Symphysis: Joint between pubic bones; supported by superior and inferior pubic ligaments.

  • Sacro-Iliac Joint: Connects sacrum to ilium; features include:

    • Auricular Surface: Articular surface for sacrum.

    • Articular Capsule: Provides stability.

    • Ligaments: Anterior, interosseous, and posterior sacro-iliac ligaments securing the joint.

Ligaments of the Pelvic Structures

  • Important ligaments include:

    • Sacrotuberous Ligament: Converts greater and lesser sciatic notches into foramina.

    • Sacrospinous ligament: Support against pelvic floor descent.

    • Iliolumbar ligament: Provides support to the lumbar region during pelvic movements.

Movements at the Sacro-Iliac Joint

  • Nutation: Forward tilting of the sacrum.

  • Contranutation: Backward tilting of the sacrum.

Pelvic Cavity Anatomy

  • Contents:

    • Peritoneum: Lining of pelvic cavity.

    • Pelvic Organs: Uterus (female), prostate (male), bladder, rectum.

    • Vessels and Nerves: Major arteries, veins, and nerves traversing the pelvic area.

    • Perineum: External genitalia, openings of the genitourinary and gastrointestinal systems.

Pelvic Fascial Layers

  • Fascia:

    • Superior Fascia of Pelvic Diaphragm: Covers the levator ani.

    • Inferior Fascia of Pelvic Diaphragm: Forms the pelvic floor.

    • Perineal Membrane: Supports structures in urogenital region.

    • Superficial Perineal Fascia: Surrounds superficial perineal region.

Ischioanal Fossa

  • Contains fat and is located laterally to the anal canal, allowing for movement and expansion.

Blood Vessels of the Pelvis

  • Key Blood Supply: Includes branches from the internal iliac artery supplying pelvic organs.

Diagrams & Additional Visuals

  • Pelvic Diagrams: Understanding various components and spatial relationships is crucial for studies. Consist of:

    • Lateral and medial views of hip bones.

    • Diagrammatic representations of the pelvic floor and fascial structures.

The above notes capture exhaustive details regarding the anatomy, function, and relationships within the pelvic region.