Lab Module 6: The Pelvis - Anatomy Dissection and Imaging Review

Comprehensive flashcards covering the anatomical structures, dissections, osteology, neurovasculature, and cross-sectional imaging of the male and female pelvis, perineum, and urinary system.

Pubic region

One of the nine regions of the abdominal cavity; a lower median region on the anterior abdominal wall (flanked by the right and left inguinal regions). Contents include the distended urinary bladder and parts of the small and large intestines. Also known as the hypogastric region.

Right inguinal region

One of the nine regions of the abdominal cavity; located in the right lower lateral anterior abdominal wall. Contents include parts of the small and large intestine, including the cecum and vermiform appendix. Also known as the right groin or right iliac region.

Left inguinal region

One of the nine regions of the abdominal cavity; located in the left lower lateral anterior abdominal wall. Contents include parts of the small and large intestines. Also known as the left groin or left iliac region.

Urinary bladder with peritoneum (Female pelvis)

A hollow organ with a smooth muscle wall (detrusor muscle) whose superior aspect is covered by peritoneum. When distended, it extends into the lower abdominal quadrants and pubic region. Three internal openings define its trigone: two ureteric orifices and one internal urethral orifice.

Uterus

A pear-shaped muscular reproductive organ divided into a body with a thick smooth muscle layer (myometrium) and a cervix that pierces the superior, anterior wall of the vagina. Serves as the blastocyst implantation site, supplies nutrients and oxygen via the placenta to the fetus, and contracts during parturition.

Ovary (Female pelvis)

A paired female gonad with an almond shape and size, located on the lateral pelvic wall near the distal end of the uterine tube. Functions in oogenesis, ovulation, and secretion of progesterone, estrogen, and inhibin. Suspended by the mesovarium of the broad ligament.

Fimbriae of uterine tube

Mobile, finger-like processes at the distal end (infundibulum) of the uterine tube, closely associated with the ovary. They spread over the ovary during ovulation to capture and guide the ovulated egg into the uterine tube.

Sigmoid colon (Female pelvis)

The characteristic S-shaped terminal segment of the large intestine beginning in the left iliac fossa and ending at the S3 vertebra. Continuous superiorly with the descending colon and inferiorly with the rectum; functions in water/electrolyte absorption and fecal storage.

Round ligament of uterus

Paired fibrous cords extending laterally from the body of the uterus, coursing through the inguinal canal to end in the labium majus. It represents the embryonic remnant of the ovarian gubernaculum and has an insignificant function in adults.

Pelvic part of ureter (Female pelvis)

The muscular tube segment extending from the pelvic brim to the base of the urinary bladder (approximately half of the ureter's total $25\text{--}30\,\text{cm}$ length). In females, it passes inferior to the uterine artery ('water under the bridge').

Rectum (Female pelvis)

The pelvic portion of the large intestine beginning at the S3 vertebral level and terminating at the pelvic floor. Measuring approximately $15\,\text{cm}$ in length, it lacks haustra and serves to store feces and absorb water and electrolytes.

Psoas major muscle (Female pelvis)

A major posterior abdominal and pelvic muscle originating from T12 and L1–L5 vertebral bodies, transverse processes, and intervertebral discs, and inserting on the lesser trochanter of the femur. Innervated by ventral rami of L2–L3; acts to flex and laterally rotate the thigh and laterally flex the trunk.

Internal iliac vein

A large pelvic vein ascending along the lateral pelvic wall that ends at the sacro-iliac joint (L5–S1) by uniting with the external iliac vein to form the common iliac vein. Drains the pelvis, perineum, gluteal region, and posterior abdominal wall.

Right internal iliac artery

Terminal branch of the common iliac artery arising at the sacro-iliac joint (L5–S1) that descends into the pelvis toward the greater sciatic notch. Distributes blood to the pelvic wall, pelvic viscera, gluteal region, perineum, and posterior abdominal wall.

Right external iliac artery

Artery descending laterally along the medial border of the psoas major muscle from the sacro-iliac joint level to the inguinal ligament. Gives off the inferior epigastric and deep circumflex iliac branches, then continues into the thigh as the femoral artery.

Right external iliac vein

Vein that begins at the inguinal ligament as the continuation of the femoral vein and courses along the pelvic brim. Drains the lower limb and inferior anterior abdominal wall, joining the internal iliac vein at the sacro-iliac joint to form the common iliac vein.

Urinary bladder (Male pelvis)

A hollow pelvic reservoir composed of smooth muscle (detrusor muscle) that stores urine and expels it during micturition. It sits posterior to the pubic symphysis; its base and floor contain the bladder trigone.

Ureteric orifice

Paired openings situated at the posterolateral corners of the bladder trigone in the base of the urinary bladder, through which urine discharged from the ureters enters the bladder lumen.

Internal urethral orifice

The opening located in the floor of the urinary bladder at the inferior apex of the bladder trigone; forms the entrance into the urethra. Regulated in males by the involuntary internal urethral sphincter composed of smooth muscle.

Vas deferens (Ductus deferens)

A thick-walled muscular tube extending from the epididymis through the scrotum, inguinal canal, and pelvis to join the duct of the seminal vesicle; actively propels sperm and testicular fluid during emission.

Pelvic part of ureter (Male pelvis)

The segment of the ureter extending through the lateral pelvis that enters the base of the bladder. In males, it is crossed superiorly by the ductus (vas) deferens near the bladder base.

Left common iliac artery

Terminal branch of the abdominal aorta arising anterior to the L4 vertebral body and coursing obliquely across L4–L5 to terminate at the sacro-iliac joint (L5–S1) by bifurcating into the internal and external iliac arteries.

Internal iliac artery (Male pelvis)

Vessel originating from the common iliac bifurcation at L5–S1 and descending toward the superior margin of the greater sciatic notch. Supplies pelvic viscera, pelvic walls, gluteal region, and perineum via anterior and posterior divisions.

External iliac artery (Male pelvis)

Arterial vessel arising from the common iliac bifurcation at the sacro-iliac joint level and running along the medial border of the psoas major muscle toward the inguinal ligament, where it continues as the femoral artery.

Psoas minor muscle

A slender muscle located anterior to the psoas major, originating from the T12–L1 vertebral bodies and intervening disc, and inserting onto the superior pubic ramus of the hip bone. Innervated by ventral rami of L1; weakly flexes the trunk.

Psoas major muscle (Male pelvis)

Thick fusiform muscle on the posterior abdominal wall and pelvic brim that unites with the iliacus muscle to form the iliopsoas, the most powerful flexor of the hip joint. Its belly embeds the roots of the lumbar plexus.

Iliacus muscle

Fan-shaped muscle originating from the iliac fossa and the pelvic surface of the sacral ala, inserting into the lesser trochanter of the femur alongside psoas major. Innervated by the femoral nerve; acts as a powerful flexor of the thigh.

Piriformis muscle

Pelvic muscle originating from the anterior surface of the sacrum and inserting onto the greater trochanter of the femur after exiting the pelvis via the greater sciatic foramen. Innervated by ventral rami of L5–S2; laterally rotates the thigh.

Ischiococcygeus muscle

A triangular muscle of the pelvic floor originating from the ischial spine and inserting onto the coccyx and inferior sacrum. Innervated by ventral rami of S4–S5 (or S3–S4); supports pelvic viscera. Also known as the coccygeus muscle.

Pelvic diaphragm

The muscular partition closing the pelvic outlet and forming the pelvic floor, composed of the levator ani and ischiococcygeus (coccygeus) muscles. It supports pelvic viscera and resists increases in intra-abdominal pressure.

Levator ani muscle

Broad muscular sheet of the pelvic floor formed by the iliococcygeus, pubococcygeus, and puborectalis muscles. Originates from the pubic body, tendinous arch of obturator internus, and ischial spine; inserts into the perineal body, coccyx, anococcygeal ligament, and midline viscera.

Tendinous arch of levator ani muscle

A thickened band of obturator fascia extending along the medial (pelvic) surface of the obturator internus muscle from the pubis to the ischial spine, serving as an origin for parts of the levator ani muscle.

Rectum (Male pelvis)

Segment of the large intestine between the sigmoid colon and anal canal, running from the S3 vertebra to the pelvic floor. It measures approximately $15\,\text{cm}$ in length, lacks haustra, and functions in the storage of feces.

Intervertebral disc

Fibrocartilaginous joint component between vertebral bodies from C2 to S1 (absent between C1 and C2). Composed of an outer fibrocartilaginous ring (anulus fibrosus) and a central gelatinous core of mucoid material (nucleus pulposus).

Lumbar vertebra

Five individual vertebrae (L1–L5) in the lower back characterized by a large, kidney bean-shaped body, stout pedicles, and a thick, blunt, quadrangular spinous process. Their bodies create the prominent anterior convexity termed lumbar lordosis.

Ala of sacrum

Large, paired, wing-like lateral projections at the base of the sacrum formed by the modified transverse processes of the first sacral vertebra (S1).

Sacrum

A triangular bone formed by the fusion of five sacral vertebrae (S1–S5), wedged between the two hip bones. Its superior anterior margin forms the sacral promontory, a key obstetric landmark for determining pelvic diameters.

Coccyx

A small triangular bone ('tailbone') located at the inferior end of the sacrum on the posterior pelvic wall, consisting of three to five variably fused, rudimentary vertebrae. Serves as an attachment point for pelvic floor muscles and ligaments.

Ilium

The largest of the three coxal bones, featuring a broad wing-like superior ala that forms the lateral boundary of the greater (false) pelvis. It contributes to the acetabulum, lesser pelvis wall, and articulates with the sacrum at the sacro-iliac joint.

Sacro-iliac joint

A strong synovial joint between the auricular surfaces of the sacrum and ilium with limited mobility due to irregular interlocking surfaces; serves as the primary route for weight and force transmission from the vertebral column to the lower limbs.

Iliac fossa

A broad, shallow concavity on the internal (pelvic) surface of the iliac ala forming the posterolateral wall of the greater pelvis; provides attachment for the iliacus muscle.

Anterior superior iliac spine (ASIS)

A prominent, rounded bony projection at the anterior end of the iliac crest that provides attachment for the lateral end of the inguinal ligament, the sartorius muscle, and the tensor fasciae latae muscle.

Anterior inferior iliac spine (AIIS)

A roughened bony projection on the anterior margin of the ilium situated immediately superior to the acetabulum; serves as the origin for the straight head of the rectus femoris muscle.

Pelvic inlet

The circular bony aperture ('pelvic brim') marking the boundary between the greater (false) and lesser (true) pelvis. Bounded by the sacral promontory, sacral alae, arcuate line of the ilium, pectineal line of the pubis, and the pubic crest. Wide/oval in females and heart-shaped in males.

Ischial spine

A pointed, sharp posterior bony projection of the ischium that separates the greater and lesser sciatic notches. Provides attachment for the coccygeus muscle and sacrospinous ligament; serves as the landmark for administering a pudendal nerve block.

Ischium

Posteroinferior coxal bone characterized by a prominent tuberosity (supporting body weight in sitting position) and a spine. Contributes to the acetabulum, wall of the lesser pelvis, and forms the inferior/posterior margin of the obturator foramen.

Pubis

Anterior component of the coxal bone comprising a body, superior pubic ramus, and inferior pubic ramus. Unites with the contralateral pubis at the pubic symphysis, helps form the obturator foramen, and contributes to the acetabulum.

Pubic symphysis

The midline fibrocartilaginous joint uniting the bodies of the right and left pubic bones; under hormonal influence in late pregnancy, its intervening disc softens to facilitate parturition.

Pubic tubercle

A small, rounded bony prominence situated on the superior anterior aspect of the pubic body lateral to the pubic symphysis; serves as the medial attachment site for the inguinal ligament.

Abdominal aorta

The main retroperitoneal systemic trunk extending from the aortic hiatus of the diaphragm to the L4 vertebral level, where it divides into the right and left common iliac arteries. Distributes blood to abdominal and pelvic viscera and the lower limbs.

Genitofemoral nerve

A branch of the lumbar plexus arising from the ventral rami of L1–L2 that pierces the psoas major muscle. Divides into a genital branch (motor to cremaster muscle; sensory to anterior scrotum/labium majus) and a femoral branch (sensory to upper anterior thigh).

Lumbar plexus and branches

A somatic nerve network formed within the psoas major muscle by the ventral rami of L1–L5 spinal nerves. Major branches include the iliohypogastric, ilioinguinal, lateral cutaneous of thigh, femoral, genitofemoral, obturator nerves, and lumbosacral trunk.

Sacral plexus

A nerve network located on the posterior pelvic wall formed by the lumbosacral trunk (ventral rami of L4–L5) and the ventral rami of S1–S4 spinal nerves, supplying the pelvis, perineum, gluteal region, posterior thigh, leg, and foot.

Femoral nerve

The largest terminal branch of the lumbar plexus, derived from the ventral rami of L2–L4. Passes beneath the inguinal ligament into the anterior thigh to innervate the anterior thigh muscles (including quadriceps), pectineus, and iliacus, and provides sensation to the anterior thigh and medial leg/foot.

Rectum (Female sagittal section)

The terminal fixed segment of the digestive tract lying anterior to the sacrum and posterior to the vagina and uterus in the female pelvis, running from S3 to the pelvic floor.

Anal canal (Female)

The terminal portion of the alimentary tract, approximately $4\,\text{cm}$ long, extending from the rectum through the pelvic floor to the anus within the anal triangle. Surrounded by involuntary internal and voluntary external anal sphincters to maintain fecal continence.

Ovary (Female sagittal section)

The primary female reproductive gonad, situated in the peritoneal cavity adjacent to the pelvic brim and uterine tube infundibulum; responsible for producing secondary oocytes and estrogen/progesterone.

Body of uterus

The muscular main portion of the uterus lying between the fundus and the cervix; lined internally by the endometrium, which sheds during menstruation, and composed of a thick myometrium that hypertrophies during pregnancy.

Uterine cavity

The slit-like internal space of the uterine body that receives sperm from the cervical canal, provides the space for blastocyst implantation and fetal development, and discharges menstrual fluid.

Cervical canal

The spindle-shaped lumen within the cervix of the uterus communicating superiorly with the uterine cavity via the internal os and inferiorly with the vaginal lumen via the external os; its lining is not shed during menses.

Posterior vaginal fornix

The deepest of the circular recesses formed around the protruding uterine cervix in the superior vagina; lies directly adjacent to the recto-uterine pouch (pouch of Douglas).

Anterior vaginal fornix

The shallow recess formed between the anterior lip of the cervix and the anterior vaginal wall, smaller than the posterior vaginal fornix.

Vagina

A fibromuscular canal (approximately $9\,\text{cm}$ long) extending from the cervix of the uterus to the vestibule of the perineum. Serves as the female copulatory organ, excretory duct for menstrual fluid, and the inferior portion of the birth canal. Contains no glands.

Labium minus

Paired, thin, hairless, and fat-free skin folds located medial to the labia majora within the urogenital triangle; unite anteriorly to form the prepuce of the clitoris and contain sebaceous glands that lubricate the vestibule.

Labium majus

Paired prominent cutaneous folds composed of subcutaneous fat pads, with hair on their lateral and inferior aspects. Extend posteriorly from the mons pubis to protect the external urogenital orifices.

Clitoris

An erectile female sexual structure located at the anterior junction of the labia minora in the urogenital triangle; consists of paired crura, a body, and an intensely sensitive glans clitoridis covered by a prepuce.

Vesico-uterine pouch

The anterior peritoneal recess in the female pelvis formed by the reflection of peritoneum from the superior surface of the urinary bladder onto the anterior surface of the uterus.

Urinary bladder (Female sagittal section)

The hollow pelvic urinary reservoir positioned immediately anterior to the vagina and anteroinferior to the body of the uterus in females.

Urethra (Female)

A short fibromuscular tube approximately $4\,\text{cm}$ in length extending from the internal urethral orifice of the bladder to the external urethral orifice in the vestibule; its short length and proximity to the anus account for higher UTI incidence in females.

Small intestine

A coiled, thin-walled, muscular tube measuring approximately $6\text{--}7\,\text{m}$ long, divided into duodenum, jejunum, and ileum; supported by the mesentery and serving as the primary site for nutrient digestion and absorption.

Anal canal (Male)

The terminal $4\,\text{cm}$ passage of the digestive tract passing through the pelvic floor between the rectum and the anus in the male anal triangle, surrounded by sphincters for fecal continence.

External anal sphincter

A voluntary skeletal muscle cylinder surrounding the anal canal, originating from the coccyx and inserting onto the perineal body and perianal skin. Innervated by the inferior rectal nerve; maintains continence via tonic contraction.

Internal anal sphincter

An involuntary ring of thickened circular smooth muscle encircling the upper two-thirds of the anal canal; innervated by parasympathetic fibers from S2–S4 and tonically contracted except during defecation.

Pelvic part of vas deferens (Male sagittal section)

The segment of the ductus deferens coursing from the deep inguinal ring along the lateral pelvic wall to the ampulla behind the bladder base, where it unites with the duct of the seminal vesicle to form the ejaculatory duct.

Seminal vesicle

Paired, contorted, sacculated muscular accessory glands located between the fundus of the bladder and the rectum. Produces approximately $60\%$ of semen volume, secreting a thick, alkaline fluid rich in fructose and prostaglandins.

Prostate

An encapsulated fibromuscular and glandular accessory organ located inferior to the bladder and posterior to the pubic symphysis. Surrounds the prostatic urethra and contributes $30\%$ of semen volume via a thin, milky, slightly acidic fluid containing citric acid, seminal plasmin, and PSA.

Recto-vesical pouch

The most inferior peritoneal recess in the male pelvic cavity, formed by the reflection of peritoneum from the anterior rectum onto the posterior surface of the urinary bladder.

Prostatic urethra

The widest and most distensible part of the male urethra that traverses the prostate gland; receives the two ejaculatory ducts and $15\text{--}20$ prostatic ducts, serving as the mixing chamber for semen.

Membranous urethra

The short ($3\text{--}5\,\text{cm}$), least distensible segment of the male urethra traversing the pelvic floor and perineal membrane (urogenital diaphragm), surrounded by the voluntary external urethral sphincter.

Spongy urethra

The longest segment of the male urethra ($\sim 15\,\text{cm}$ long) traversing the bulb and corpus spongiosum of the penis to terminate at the external urethral orifice; also known as the penile urethra.

External urethral orifice (Male)

The external vertical slit-like opening of the urinary tract situated at the tip of the glans penis; serves for the discharge of both urine and semen.

Penis

The male copulatory organ located in the urogenital triangle, consisting of an attached root (crura and bulb) and a free body composed of three cylindrical erectile bodies: paired dorsal corpora cavernosa and a ventral corpus spongiosum.

Corpus cavernosum penis

Paired dorsal cylindrical erectile bodies encased in a thick fibrous capsule (tunica albuginea). Engorgement of their vascular cavernous spaces with blood produces the majority of penile rigidity and enlargement during erection.

Corpus spongiosum penis

The single midventral erectile column of the penis surrounding the spongy urethra; originates from the bulb of the penis and expands distally into the conical glans penis.

Glans penis

The expanded distal extremity of the corpus spongiosum that caps the blunt ends of the paired corpora cavernosa; rich in sensory nerve endings critical for the male sexual response.

Remnant of prepuce of penis

A circular cutaneous ridge behind the coronal sulcus marking the junction between the body and glans penis following circumcision (removal of the foreskin).

Scrotum (Sagittal section)

Cutaneous and fibromuscular pouch containing dartos smooth muscle, housing the testes, epididymides, and spermatic cords at a temperature approximately $3^\circ\text{C}$ below core body temperature.

Epididymis

A highly coiled muscular tube situated along the posterior border of the testis, divided into head, body, and tail. Serves as the site for sperm maturation, motility acquisition, and storage for $5\text{--}6\,\text{weeks}$.

Scrotal part of vas deferens

The initial convoluted-to-straight segment of the vas deferens ascending from the tail of the epididymis within the spermatic cord in the scrotum; common site for elective vasectomy.

Renal pelvis (Kidney Layer 1)

The funnel-shaped proximal expansion of the ureter exiting the renal hilum, formed by the convergence of two to three major calyces to collect and direct urine into the ureter.

Renal artery

Paired visceral branches of the abdominal aorta arising just below the superior mesenteric artery; enters the renal hilum to supply the kidney, upper ureter, and suprarenal gland. The right renal artery is longer than the left.

Hilum of kidney

The vertical slit-like medial indentation of the kidney that transmits the renal vein (anterior), renal artery (middle), renal pelvis (posterior), along with lymphatic vessels and autonomic nerves.

Renal vein

Large vein emerging from the renal hilum anterior to the renal arteries to drain into the inferior vena cava. The left renal vein is three times longer than the right and receives the left gonadal and left suprarenal veins.

Ureter (Kidney Layer 1)

A retroperitoneal muscular tube measuring $25\text{--}30\,\text{cm}$ in length that carries urine from the renal pelvis to the urinary bladder via rhythmic peristaltic contractions.

Renal pelvis (Coronal section)

The central urine collecting basin within the renal sinus that receives urine from major calyces and tapers inferomedially to become continuous with the ureter.

Major calyx

Two to three broad, funnel-like conduits per kidney formed by the confluence of two or more minor calyces; channels urine into the renal pelvis.

Renal sinus

The internal, fat-filled cavity of the kidney opening at the hilum that encloses the renal calyces, renal pelvis, branches of renal vessels, nerves, and lymphatics.

Minor calyx

Small cup-shaped tubes (eight to ten per kidney) that encircle the renal papillae of renal pyramids to collect urine emerging from papillary ducts.

Renal papilla

The apex or tip of a renal pyramid that projects into a minor calyx to release urine into the calyceal system.

Renal column

Inward extensions of renal cortex projecting between adjacent medullary renal pyramids toward the renal sinus; contains blood vessels and identical histological tissue to the cortex.