Review of pelvic osteology and muscles of the pelvis

PELVIS & PERINEUM: Review of Pelvic Osteology

  • Course: ANTH/EEB/NURS 250
  • Lecture 7.1

PELVIS: Osteology Review

  • Ossification and Main Structures:
    • OS COXA:
    • Also known as hip bone, consists of three parts: ilium, ischium, and pubis.
    • SACRUM:
    • Composed of fused sacral vertebrae, articulates with the ilium at the sacroiliac joint.

Key Anatomical Features of the Pelvis

  • Anterior View:
    • PUBIC SYMPHYSIS:
    • The cartilaginous joint between the left and right pubic bones.
    • ILIAL STRUCTURES:
    • ILIAC CREST:
      • The superior border of the ilium, easily palpated.
    • ANTERIOR SUPERIOR ILIAC SPINE (ASIS):
      • A bony prominence on the iliac crest, important for muscle attachment and anthropometric measurements.
    • ANTERIOR INFERIOR ILIAC SPINE (AIIS):
      • Another important landmark on the ilium structure.
    • ACETABULUM:
    • The cup-shaped socket for the femur.
    • ISCHIUM:
    • Forms the lower part of the hip bone.
Pelvic Inlet
  • True Pelvis:
    • Protects reproductive organs and bladder.
  • False Pelvis:
    • Supports abdominal cavity.

PELVIS: Ligament Review

Key Ligaments:

  • SACROSPINOUS LIGAMENT:
    • Connects the sacrum to the ischial spine, important for pelvic stability.
  • SACROTUBEROUS LIGAMENT:
    • Connects the sacrum to the ischial tuberosity, prevents forward rotation of the sacrum.

Foramina:

  • GREATER SCIATIC FORAMEN:
    • Passage for structures entering or leaving the pelvis.
  • LESSER SCIATIC FORAMEN:
    • Transmits the obturator internus tendon and vessels.

PELVIS: Muscles of the Pelvic Floor

Contents:

  • LEVATOR ANI MUSCLES:
    • Primarily support pelvic organs and aid in accounting for the pelvic diaphragm.
  • COCCYGEUS MUSCLE:
    • Stabilizes the coccyx and supports pelvic organs.
  • PIRIFORMIS MUSCLE:
    • Lower limb muscle, also aids in pelvic stability.
  • OBTURATOR INTERNUS MUSCLE:
    • Provides support and facilitates movement in pelvic processes.
  • Detailed Structures:
    • Urogenital hiatus: Opening in pelvic diaphragm.
    • Coccygeus muscle - attaches to the sacrospinous ligament.

Additional Pelvic Floor Muscles:

  • Iliococcygeus Muscle:
    • Part of the levator ani group, contributes to pelvic support.
  • Pubococcygeus Muscle:
    • Assist with continence and pelvic support.
  • Puborectalis Muscle:
    • Plays a role in maintaining fecal continence.

PERINEUM: Overview

Structure:

  • Divided into Urogenital Triangle and Anal Triangle.
  • Key anatomical references include:
    • Pubic Symphysis
    • Ischial Tuberosity
    • Ischial Spine

Female Anatomy in Perineum:

  • Superficial Layer:
    • Mons Pubis: Fat pad over pubic symphysis.
    • Clitoris: Erectile organ above the urethra.
    • Labia Minora and Majora: Folds of skin protecting the vaginal opening.
    • External Urethral Orifice, Vagina, Anus: Openings in the perineum.
  • Middle Layer Features:
    • Bulbospongiosus Muscle, Ischiocavernosus Muscle: Contribute to sexual function and stabilization of the pelvic area.

Male Anatomy in Perineum:

  • Superficial Layer:
    • Glans Penis, Scrotum: Forms part of the external genitalia.
  • Middle Layer:
    • Bulbospongiosus Muscle, Ischiocavernosus Muscle: Provide support and structure to the scrotum and penis.
    • External Anal Sphincter: Responsible for controlling bowel movements.

PELVIS: Bladder and Related Structures

Female Anatomy:

  • Urogenital Peritoneum and Bladder Configuration:
    • Left Ureter: Channels urine from the kidney to the bladder.
    • Neck of Bladder and Urethra: Connects to the external environment, plays a crucial role in urinary function.

Male Anatomy:

  • Features such as the Prostate, Bulb of Penis:
    • Internal Urethral Sphincter: Controls urine flow and prevents backflow during ejaculation.
    • External Urethral Sphincter: Additional layer around the urethra for voluntary control of urination.
Key Anatomical Relationships:
  • The Prostatic Urethra connects the bladder and prostatic fluid.
  • Ejaculatory Ducts: Note their function in transporting sperm during ejaculation.

PELVIS: Erectile Tissues and Sphincters

Male Erectile Structures:

  • Glans Penis, Corpus Cavernosum, Corpus Spongiosum: Form the erectile tissues involved in penile erection and sexual function.
  • **Muscles Associated with Erections: *Ischiocavernosus Muscle, Bulbospongiosus Muscle*: These assist in the rigidity of the penis.

Urethral Muscles in Both Genders:

  • Spanning deep structures:
    • Urethrovaginal Sphincter: Includes parts such as external and internal muscular structures controlling passage.
    • Superficial and Deep Transverse Perineal Muscles: Provide a structural support base within the perineum.

PELVIS: Detailed Interrelations of Male Structures

Deep Layer Relations:

  • Involves ligaments and the perineal membrane offering attachment for various structures such as:
    • Dorsal Nerve and Arteries: Supplying erectile tissues.
    • Deep Dorsal Vein of Penis (cut): Leading away from the erectile structures.

Vascular Supply and Innervation of Pelvic Region:

  • Internal Pudendal Artery and Vein: Supplies blood to the pelvic floor.
  • Pudendal Nerve: Main nerve for innervating the muscles of the perineum.

Anatomical Corridors:

  • Ischial Tuberosity, Sacrotuberous Ligament: Key landmarks in understanding perineal support anatomy.

APPLICATIONS IN ANATOMY AND CLINIC:

Ethical and Practical Considerations:

  • Knowledge of pelvic structure is crucial for interventions in urology, gynecology, and pelvic surgeries.
  • Understanding muscle structures provide insights into gender differences affecting treatments and rehabilitation protocols.

Clinical Relevance:

  • Insights into pelvic anatomy are indispensable for obstetric care, understanding of childbirth dynamics, and surgical implications surrounding reproductive health.