Pelvis Anatomy Quiz

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Questions and Answers

Which structure primarily supports the weight of the body and distributes it into the lower extremities?

Ischium

Sacrum (correct)

Coccyx

Ileum

What is the primary role of the pelvic diaphragm muscles?

Support pelvic organs (correct)

Assist in the movement of lower limbs

Facilitate locomotion

Connect to the vertebral column

Which of the following is NOT a component of the bony pelvis?

Pubis

Patella (correct)

Sacrum

Ileum

Which passageway allows for the exit of final spinal nerves from the vertebral canal?

Intervertebral foramen (D) Signup and view all the answers

Which part of the pelvis articulates with the femur at the acetabulum?

Ischium (B) Signup and view all the answers

Which terminology describes the region of the pelvis that contains the rectum, bladder, and reproductive organs?

Pelvic bowl (C) Signup and view all the answers

What defines the difference between true pelvis and false pelvis?

True pelvis contains reproductive organs (B) Signup and view all the answers

Which structure serves as a bridge between the ischium and pubis?

Ischiopubic ramus (C) Signup and view all the answers

What structures are considered to be part of the true pelvis?

Ring of bones in the pelvic cavity (C) Signup and view all the answers

Which anatomical feature serves as the imaginary division between the true and false pelvis?

Pelvic inlet (A) Signup and view all the answers

What shape does the perineum take?

Diamond-shaped (B) Signup and view all the answers

Which ligaments are primarily responsible for anchoring the distal sacrum to the os coxae?

Sacrospinous and sacrotuberous ligaments (A) Signup and view all the answers

What is the role of the pelvic diaphragm?

Separate the pelvic cavity from the perineum (B) Signup and view all the answers

The anal triangle is defined by which of the following borders?

Ischial tuberosity to tip of coccyx (D) Signup and view all the answers

Which muscles contribute to forming the floor of the pelvis?

Levator ani and coccygeus (D) Signup and view all the answers

Which of the following triangles contains openings for urinary and reproductive tracts?

Urogenital triangle (C) Signup and view all the answers

What is the primary role of the detrusor muscle in the urinary bladder?

To enable the bladder to expel fluid (C) Signup and view all the answers

Which structures are known to pass through the inguinal canal?

Testicular vasculature and vas deferens (A) Signup and view all the answers

What is the rectouterine space clinically important for?

Pooling of fluids in the abdominopelvic cavity (D) Signup and view all the answers

What type of epithelium lines the surface of the urinary bladder?

Transitional epithelium (C) Signup and view all the answers

Where do the ureters travel in relation to the uterine arteries and veins?

Below the uterine arteries and veins (B) Signup and view all the answers

Which of the following openings in the urinary bladder forms the trigone area?

Urethra and two openings for the ureters (B) Signup and view all the answers

Which muscle is located deep to the perineal skin?

External anal sphincter (D) Signup and view all the answers

Which ligament runs from the ASIS to the pubic tubercule?

Inguinal ligament (C) Signup and view all the answers

What is the function of paraurethral glands in females?

Secretion of mucus (C) Signup and view all the answers

What is the anatomical relationship of the urinary bladder to the pubis?

There is a potential space between the pubis and bladder (D) Signup and view all the answers

What role do Skene’s glands play during orgasm?

They secrete fluid similar to prostate secretions. (D) Signup and view all the answers

What happens to the cervix before birth?

It becomes rigid, shortens, and softens. (D) Signup and view all the answers

Which component is NOT produced by the prostate?

Fructose (C) Signup and view all the answers

What is a consequence of an ectopic pregnancy?

The implantation occurs outside the uterus, which can be dangerous. (D) Signup and view all the answers

What occurs during the remission phase of sexual arousal?

Smooth muscles constrict, decreasing arterial flow. (C) Signup and view all the answers

How does the body compensate for the shift in center of gravity during pregnancy?

Lumbar spine becomes more lordosed. (C) Signup and view all the answers

What triggers ejaculation during the reproductive process?

Smooth muscular contractions and closure of the internal urethral sphincter. (A) Signup and view all the answers

Which of the following statements about sperm development is accurate?

Sperm gain motility in the epididymis. (B) Signup and view all the answers

Which function do the bulbourethral glands serve?

Producing lubrication for the urethra. (D) Signup and view all the answers

What is the role of prostaglandins produced by seminal vesicles?

They dilate the cervix. (C) Signup and view all the answers

What is the primary function of the endometrium in the uterus?

Swells to receive a fertilized embryo and sheds if not fertilized (B) Signup and view all the answers

Which ligament serves to anchor the ovary to the uterine body?

Ovarian ligament (C) Signup and view all the answers

What is the anatomical position of the prostate gland in relation to the urinary bladder?

Posterior (A) Signup and view all the answers

What type of muscle forms the internal anal sphincter?

Circular smooth muscle (C) Signup and view all the answers

Which part of the female reproductive system acts as a conduit for eggs from the ovaries to the uterus?

Uterine/Fallopian tube (C) Signup and view all the answers

The broad ligament of the uterus is best described as what?

A fold of peritoneum that supports the uterus (B) Signup and view all the answers

What type of epithelium is found in the anal canal towards the anal verge?

Keratinised stratified squamous epithelium (B) Signup and view all the answers

Which artery is primarily responsible for supplying blood to the uterus?

Uterine artery (D) Signup and view all the answers

What anatomical structure is absent in the male urethra compared to the female?

External urethral orifice (C) Signup and view all the answers

What is the primary role of seminal vesicles?

Secrete fluid for sexual reproduction (C) Signup and view all the answers

What structure provides the main blood supply to the external genitalia in both males and females?

Internal pudendal artery (D) Signup and view all the answers

What role does the levator ani play in the pelvic anatomy?

Supports pelvic organs and encircles the anal canal (C) Signup and view all the answers

How long is the male urethra on average?

18 to 20 cm (B) Signup and view all the answers

What structure is primarily responsible for the formation of the internal urethral sphincter?

Circular smooth muscle of the bladder (D) Signup and view all the answers

What is the primary pathway for sympathetic nerves serving pelvic organs?

Thoracolumbar region between T1 and L2/3 (A) Signup and view all the answers

Which structures are primarily drained by the internal iliac lymph nodes?

Internal pelvic structures and middle part of the rectum (C) Signup and view all the answers

What is the function of the pudendal nerve in relation to micturition?

Maintains contraction of the external urethral sphincter during inappropriate locations (B) Signup and view all the answers

What delineates the boundaries of the perineum?

Coccyx and ischial tuberosities (D) Signup and view all the answers

Where does the internal pudendal artery exit the pelvis?

Greater sciatic foramen and then lesser sciatic foramen (A) Signup and view all the answers

Which type of erectile tissue is primarily responsible for rigidity during an erection?

Cavernous erectile tissue, which includes corpus cavernosum (D) Signup and view all the answers

What is the function of the levator ani muscle in the anal canal?

Maintains closure of the anal canal (C) Signup and view all the answers

What role do stretch receptors play in the micturition reflex?

Send urgency signals to CNS as bladder fills (D) Signup and view all the answers

What occurs when the pudendal nerve is activated during sexual activity?

It maintains erection by restricting venous outflow (D) Signup and view all the answers

Which section of the female reproductive tract is most commonly associated with fertilization?

Ampulla of the uterine tube (C) Signup and view all the answers

What is the primary structural difference between spongy and cavernous erectile tissues?

Spongy tissues are located in structures that require patent lumens (A) Signup and view all the answers

Which ligament is primarily responsible for suspending the ovaries?

Suspensory ligament (B) Signup and view all the answers

What is the anatomical significance of the perineal body?

A fibromuscular structure that connects various fascial layers (C) Signup and view all the answers

How do greater vestibular glands contribute to female sexual response?

By providing lubrication to the vagina (A) Signup and view all the answers

Study Notes

Bony Pelvis Functions

Intersection of Abdomen and Lower Extremity: Serves as the connection point between the abdominal cavity and lower limbs.
Locomotor Function: Provides attachment sites for numerous muscles involved in movement and articulates with the lower limb through the acetabulum for the femur.
Weight Distribution: Each vertebra increases in size inferiorly, with the sacrum distributing body weight to the lower extremities.
Organ Protection: The ilia (superior bony pelvis) protects lower abdominal organs like the sigmoid colon, while the pelvic bowl protects the pelvic organs such as the rectum, bladder, and reproductive organs.

Bony Pelvis Components

Ox Coxae (Pelvic Bone): Fuses at 16-18 years old, composed of:
- Ilium: Superior bone with flaring wings (ala), the hip is located at the iliac crest.
- Pubis: Anterior bone, articulates with the opposite side.
- Ischium: Posterior bone, we sit on the ischial tuberosity.
Greater and Lesser Sciatic Notches: Important for neurovascular structures and muscles to pass through.
- Separated by the ischial spine.
- The roughened ischial tuberosity (inferior to the lesser notch) serves as the origin for the hamstrings.
- The ischiopubic ramus connects the ischium and pubis.
- The obturator foramen (a hole inferior to the acetabulum) is largely closed by a fibrous membrane.
Posterior Components: Sacrum and Coccyx
- The sacrum is the fusion of five inferior vertebrae, distributing weight to the ilia.
- The coccyx is below the sacrum, a remnant of 4-5 vestigial tailbones.
- The promontory is the most anterior and superior aspect of the sacrum.
- The sacrum articulates with the ilia laterally through the auricular surface.
- Intervertebral foramina between each vertebral pair allow spinal segments to exit.
- Anterior and posterior sacral foramina allow for the passage of spinal nerves.

True vs False Pelvis

True Pelvis: The ring of bones in the pelvic cavity, protecting organs such as the bladder, rectum, and reproductive organs.
False Pelvis: Superior projecting ala, located in the abdominal cavity.
Pelvic Inlet: The division between the true and false pelvis, formed by:
- Sacral promontory
- Arcuate line of ilium
- Pectinate line of pubis

Perineum

Diamond-shaped space separated from the pelvis by the muscular pelvic diaphragm.
Borders:
- Pubic symphysis
- Ischial tuberosities
- Tip of coccyx
Divided into two triangles:
- Urogenital triangle (anterior): Contains openings for urinary and reproductive tracts and external genitalia.
- Anal triangle (posterior): Contains the anus and the pelvic diaphragm.

Ligaments of the Pelvis

Posterior Ligaments:
- Sacrospinous ligament: More medial, between the sacrum and ischial spine.
- Sacrotuberous ligament: More lateral, between the sacrum and ischial tuberosities.
- Both ligaments anchor the distal sacrum to the ox coxae and close off the greater and lesser sciatic notches.
Obturator Foramen: Largely blocked by the obturator membrane, with the obturator internus and externus muscles.
Obturator Canal: A small tunnel allowing for the passage of the obturator artery, vein, and nerve.

Muscles of the Pelvis (Superior View)

Levator Ani: Cone-shaped muscle forming the majority of the pelvic floor.
- Originates on the pubis, ilium, and fascia of the obturator internus.
- Apex is at the anal canal.
Coccygeus: Internal sacrum (anterior) to the ischial spine.
Piriformis: Situated within the pelvic bowl.

Muscles of the Pelvis (Coronal Section)

Levator Ani: Tapers down to the anal canal.
External Anal Sphincter: Deep to the perineal skin.

Passageways for Structures to Enter/Leave the Pelvis

Inguinal Ligament: From the ASIS to the pubic tubercle.
- Femoral artery, vein, and nerve pass under the inguinal ligament.
Inguinal Canal: Oblique tunnel through the anterior abdominal musculature.
- Testicular vasculature and vas deferens (males), and round ligament of the uterus (females) pass through.
Obturator Canal: Passageway for the obturator artery, vein, and nerve.
Greater Sciatic Foramen:
- Gluteal artery, vein, and nerve pass through on either side of the piriformis.
- Pudendal nerve, internal pudendal artery, and vein exit and then turn to reach the perineum.
Urogenital Hiatus: Gap anterior for the openings of urinary and reproductive tracts into the urogenital triangle of the perineum.
- Allows for the passage of autonomic nerves to external genitalia.

Female Pelvic Viscera

Anterior: Urinary bladder and urethra.
Middle: Uterus and adnexa (ovaries, uterine tubes, ligaments).
Posterior: Rectum and anus.

Female Pelvic Viscera Positional Relationships

Retropubic Space: Potential space between the pubis and bladder, normally filled with loose connective tissue.
Vesicouterine Pouch: Real space between the bladder and uterus.
Rectouterine Space: Space between the uterus and rectum, clinically important as fluids can pool here.

The Bladder (Female)

Detrusor Muscle: Irregularly arranged smooth muscle in the bladder wall, responsible for contraction during urination.
Transitional Epithelium: Lines the bladder surface, accommodating extreme stretching during storage and evacuation of urine.

Female Urethra

4-6 cm long and 6 cm in diameter.
Located anteriorly to the vagina.
Both the urethra and vagina open into the vestibule between the labia majora.

Paraurethral Glands (Skene’s Glands)

Secrete mucus into the lesser vestibule.
Homologous to the male prostate gland.

Uterus and Adnexa (Female)

Uterus: Primary female reproductive organ, composed of the:
- Fundus: Superior portion.
- Body: Middle portion.
- Cervix: Inferior portion.
Myometrium: Fibromuscular wall of the uterus.
Endometrium: Internal lining of the uterus, responsible for receiving a fertilized embryo.
Cervix: Projects into the vagina, creating the fornix on either side.
Ovary: Lateral and posterior to the uterus.
Uterine/Fallopian Tube: Superior to the ovary, with fimbriae to capture eggs.

Ligaments of the Uterus (Female)

Suspensory Ligament: Fold of peritoneum from the abdominal cavity to the ovary, containing the ovarian artery and vein.
Ovarian Ligament: Anchors the ovary to the uterine body.
Cardinal Ligament: Pelvic floor component, containing the uterine artery and vein.
Uterosacral Ligament: Visceral connective tissue anchoring the base of the uterus to the pelvis walls.
Broad Ligament: Mesentery of the uterus, composed of the:
- Mesometrium: Broader part attached to the uterine body.
- Mesosalpinx: Attached to the uterine tube.
- Mesovarium: Attached to the ovary.
Round Ligament: Travels deep within the peritoneum towards the inguinal canal, anchoring the uterus to the body wall.

Rectum and Anal Canal (Female)

Anal Canal: Features characteristic circular and longitudinal smooth muscle of the digestive tract.
Internal Anal Sphincter (IAS): Autonomic control, formed by circular muscle in the anal canal.
Levator Ani: Encircles the anal canal, with the external anal sphincter at its end.

Rectum and Anal Canal (Female) - Histology

Anorectal Line: Border between anal canal and rectum, 4-5 cm distal to the anal verge (opening).
Pectinate/Dentate Line: Located below the anorectal line.
Rectal Epithelium: Simple columnar epithelium.
Anal Canal Epithelium:
- Stratified squamous epithelium: Below the anorectal line.
- Keratinized stratified squamous epithelium: Near the anal verge.
External Anal Sphincter (EAS): Skeletal muscle.

Male Pelvic Viscera

Anterior: Urinary bladder.
Posterior: Rectum.
Inferior: Prostate, seminal vesicles.

Male Pelvic Viscera - Positional Relationships

Retropubic Space: Potential space between the pubis and bladder.
Rectovesical Pouch: Space between the bladder and rectum.
Prostate: Dense, fibromuscular gland at the base of the bladder, supporting it.
Internal Urethral Sphincter (IUS): Well-defined in males.

Male Urethra

18-20 cm long.
Three regions:
- Prostatic: Through the prostate.
- Membranous: Through the external urethral sphincter (EUS).
- Spongy/penile: Through the root and body of the penis, expanding into the navicular sinus before exiting at the external urethral orifice.

Prostate and Seminal Vesicles (Male)

Vas Deferens: Travels along the posterior bladder to enter the prostate.
Seminal Vesicles: Secrete fluid for reproduction, opening into the ejaculatory duct of the prostate.
Bulbourethral (Cowper’s) Glands: Secrete lubricating fluid, opening into the spongy urethra.

Blood Supply and Venous Drainage of the Pelvis

Veins: Generally accompany the deep arteries.
Arteries: Primarily supplied by the internal iliac artery.
Variation: Significant variation in pelvic blood supply is common.

Male Schematic - Blood Supply through the Pelvis

Abdominal Aorta: Bifurcates before the pelvic inlet.
Right and Left Common Iliac Arteries:
- Median Sacral Artery: Between the common iliac arteries.
- External Iliac Artery: Extends outside the pelvis, becoming the femoral artery.
- Internal Iliac Artery: Supplies the pelvis, dividing into anterior and posterior branches.

Posterior Branches of Internal Iliac Artery

Superior Gluteal Artery: Supplies gluteus medius, minimus, and tensor fascia lata, exiting through the greater sciatic foramen.
- Iliolumbar Artery (branch of superior gluteal): Ascends back to the abdominal cavity.
- Lateral Sacral Artery: Supplies the lateral aspect of the sacrum.

Anterior Branches of Internal Iliac Artery

Umbilical Artery: No longer carries blood to the placenta in adults, obliterated in the anterior abdominal wall.
- Superior Vesical Artery (branch of umbilical): Supplies the superior bladder.
Obturator Artery: Enters the medial thigh through the obturator canal.
Inferior Gluteal Artery: Supplies gluteus maximus, exiting through the greater sciatic foramen.
Internal Pudendal Artery: Supplies the perineum, exiting through the greater sciatic foramen.
Middle Rectal Artery: Branch of the internal pudendal.

Male Specific Reproductive Arteries

Inferior Vesical Artery: Supplies the inferior bladder and seminal vesicles.
- Prostatic Artery: Arises from the inferior vesical.
Artery to the Vas Deferens: Arises from the superior vesical artery.

Female Schematic - Blood Supply through the Pelvis

Female Specific Branches:
- Uterine Artery: Highly variable, travels within the cardinal ligament of the uterus.
  - Supplies the uterus and gives rise to the vaginal artery.
- Vaginal Artery: Supplies the upper vagina and gives rise to the inferior vesical artery, supplying the base of the bladder.

Pelvic Nerves

Superior gluteal nerve exits the greater sciatic foramen (GSF) superior to the piriformis muscle.
Inferior gluteal nerve exits the GSF inferior to the piriformis muscle.
Internal pudendal nerve exits the GSF between the coccygeus and piriformis muscles before entering the perineum through the lesser sciatic foramen (LSF).
Obturator nerve travels with the obturator artery through the obturator canal.

Autonomic Innervation

Sympathetic nerves originate in the thoracolumbar region (T1-L2/3).
Parasympathetic nerves originate in the craniosacral region (Cn3,7,9,10 or S2-4).
Pelvic nerves coalesce to form the hypogastric plexus, responsible for innervating abdominal and pelvic organs.
The superior aspect of the hypogastric plexus mainly contains sympathetic nerves, while the inferior aspect contains a mixture of sympathetic and parasympathetic nerves.

Somatic Innervation

The somatic nerves (S2-4) in the perineum form the pudendal nerve, which innervates structures in the anal and urogenital triangles.
The pudendal nerve innervates the external urethral and external anal sphincters.
Micturition and defecation involve both smooth (autonomic) and skeletal (somatic) muscles.

Micturition Reflex

The detrusor muscle and internal urethral sphincter are both smooth muscles.
Sympathetic stimulation relaxes the detrusor and contracts the internal urethral sphincter, storing urine.
Parasympathetic stimulation contracts the detrusor and relaxes the internal urethral sphincter, facilitating urination.
The pudendal nerve contracts the external urethral sphincter if the location is inappropriate for urination.

Defecation Reflex

The wall of the rectum and internal anal sphincter are smooth muscles.
Sympathetic stimulation relaxes the rectal wall and contracts the internal anal sphincter, storing feces.
Parasympathetic stimulation contracts the rectal wall and relaxes the internal anal sphincter, facilitating defecation.
The pudendal nerve contracts the external anal sphincter if the location is inappropriate for defecation.

Pelvic Lymphatics

Pelvic lymph nodes draining structures include internal iliac nodes (internal pelvic structures), inguinal nodes (external genitalia) and preaortic and lumbar nodes (testes and ovaries).
External iliac lymph nodes drain superior pelvic lymph nodes and structures near the inguinal canal.

Perineum and External Genitalia

The perineum is the space inferior to the pelvic floor, delineated by the levator ani muscle.
The perineum contains two triangles: the urogenital triangle (reproductive and urinary openings) and the anal triangle (anal opening).
The levator ani muscle encircles the anal canal and forms the ischioanal/ischiorectal fossae.
The perineal membrane is a thickened membrane in the urogenital triangle that provides support for the external genitalia.

Perineal Fascia

Perineal fascia is an extension of abdominal fascia.
Superficial perineal fascia (Colles' fascia) is continuous with Camper's and Scarpa's fascia.
Deep perineal fascia is superior to the perineal membrane.
The perineal body is a midline point where various fasciae converge.

Clinical Correlate: Extravasation of Urine

Urine extravasation can occur due to a perforated urethra.
If the spongy urethra is perforated, urine leaks into the superficial perineal pouch.
If the wound is more proximal, urine will be found in the ischiorectal fossa and between the peritoneum and transversalis fascia.

Female External Genitalia

Mons pubis is a rounded fatty eminence anterior to the pubic bone.
Labia majora are prominent folds protecting labia minora.
Labia minora are fat-free folds containing spongy erectile tissue.
Clitoris is an erectile organ composed of crura, a body, and a glans.
Vestibule is the space enclosed by the labia minora, containing the external urethral and vaginal orifices.

Erectile Tissues in Females

Clitoris contains both spongy and cavernous erectile tissues.
Bulbs of vestibule are spongy erectile tissues limiting the vaginal opening.
Greater vestibular glands secrete lubricating fluids.

Skeletal Muscles in Females

Ischiocavernosis muscle overlays the crus of the clitoris.
Bulbospongiosus muscle overlays the bulb of the vestibule.
Superficial and deep transverse perineal muscles support the pelvic floor.

Male External Genitalia

The penis consists of a root, body, and glans.
The root of the penis includes the two crura and the bulb.
The corpus cavernosum is composed of cavernous erectile tissue.
The corpus spongiosum is composed of spongy erectile tissue and contains the urethra.
The glans penis contains the external urethral orifice.

Testis

Testes produce testosterone and sperm.
The seminiferous tubules are responsible for sperm production.
Sperm travels from the seminiferous tubules to the epididymis, where it is stored until it becomes mobile.

Erectile Tissues in Males

The penis contains both cavernous and spongy erectile tissues.
The corpus cavernosum is primarily cavernous.
The corpus spongiosum is primarily spongy.

Perineal Muscles in Males

The bulbospongiosus muscle overlays the bulb of the penis.
The ischiocavernosus muscle overlays the crus of the penis.

Neurovasculature of the Perineum

The internal pudendal artery exits the pelvis through the GSF and enters the perineum through the LSF.
The internal pudendal artery runs through the pudendal canal (Alcock's canal).
The inferior rectal artery supplies the anus, EAS, and ischioanal fat.
The perineal artery supplies muscles of the external genitalia and erectile tissues.
The dorsal genital artery supplies the dorsal clitoris or penis.

Perineal Nervous Innervation

The pudendal nerve follows the same path as the internal pudendal artery.
The pudendal nerve innervates the bulbospongiosus, ischiocavernosus, external anal and urinary sphincters.

Autonomic Innervation of Erectile Tissue

Autonomic nerves enter the urogenital triangle through the urogenital hiatus.
Parasympathetic stimulation causes erection and remission.
Sympathetic stimulation causes emission and ejaculation.

Female Reproductive Tract

Ovaries produce oocytes and hormones.
The uterine tube (fallopian tube) captures the oocyte expelled from the ovary and guides it towards the uterus.
The uterus undergoes cyclical changes in the endometrium, controlled by hormones.
The vagina and cervix are involved in intercourse and childbirth.

Ejaculation/Orgasm

The complex interplay between somatic and autonomic nerves facilitates sexual function.
Somatic nerves contribute to maintaining erection and assisting in ejaculation.
Autonomic nerves mediate erection, emission, ejaculation, and remission.

Female Reproductive System

During orgasm, the bulbospongiosus and ischiocavernosus muscles contract violently, due to the pudendal nerve.
The Skene's glands, located periurethrally, are similar to the prostate and secrete a significant amount of fluid during orgasm.
Remission involves the parasympathetic, sympathetic, and somatic nervous systems.
- Smooth muscle constricts arteries, reducing blood flow to the cavernous tissue.
- The bulbospongiosus and ischiocavernosus muscles relax, allowing blood to drain.
Sperm travels through the acidic environment of the vagina and cervical os.
The sperm must choose the correct uterine tube and penetrate the oocyte's cell membrane for fertilization to occur.
After successful implantation, the embryo sustains progesterone production in the ovary until the placenta takes over, preventing menstruation (known as the gravid phase).
Ectopic pregnancy occurs when the fertilized egg implants outside the uterine cavity, commonly on the ovary surface, in the uterine tube, or in the peritoneal cavity.
- These pregnancies usually abort due to nutrient deficiency but can be dangerous if they don't.
During pregnancy, the uterus enlarges, displacing other organs.
- The respiratory diaphragm remains at the same height, and the abdominal organs adjust to fit within the remaining space.
The cervix becomes rigid, shortens, and softens before birth.
The cervical and thoracic spine straighten, while the lumbar spine becomes more lordotic.
- This balances the center of gravity which shifts anteriorly during pregnancy.
The pubic symphysis and sacroiliac joints relax, impacting the locomotor gait.

Male Reproductive System

Erectile Tissues/Sexual Stimulation:
- Smooth muscle relaxation near arteries supplying the corpora cavernosa and crura of the penis allows blood flow and dilation of cavernous spaces (parasympathetic).
- The bulbospongiosus and ischiocavernosus muscles contract, compressing venous return from the erectile tissues, similar to the female response.
Testis and Epididymis:
- Sperm develops in the seminiferous tubules.
- Sperm gains motility and "learns to swim" as it moves through the rete testis and efferent tubules to the epididymis.
Vas Deferens and Seminal Vesicles during Emission:
Sperm travels from the epididymis to the prostatic urethra via smooth muscle contractions (sympathetic innervation).
The seminal vesicles contribute:
- Fructose (energy for sperm).
- Prostaglandins (dilate the cervix).
- Bicarbonate (neutralizes the acidic vagina).
Prostate:
- The prostate is innervated by the sympathetic nervous system during sperm and seminal fluid transit through the ejaculatory duct.
- The prostate produces:
  - Citric acid (nutrient for sperm health).
  - Seminalplasmin (antibiotic).
  - Prostate-specific antigen (liquifies semen).
Bulbourethral Glands:
- The bulbourethral glands are innervated by the sympathetic nervous system and secrete clear mucus (lubricant) before ejaculation to condition the urethra.
Ejaculation:
- The smooth muscle contractions continue forcefully from emission (sympathetic).
- The internal urethral sphincter closes (sympathetic), preventing sperm and seminal fluids from entering the urinary bladder (essential for reproduction).
- The bulbospongiosus and ischiocavernosus contract forcefully to expel semen.
Remission:
- Smooth muscle (sympathetic) constricts cavernous tissue, reducing arterial flow.
- The bulbospongiosus and ischiocavernosus muscles relax, opening veins.

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Test your knowledge on the anatomy of the pelvis with this comprehensive quiz. Questions cover aspects like the pelvic diaphragm, bony pelvis components, and distinctions between true and false pelvis. Ideal for students in anatomy or health sciences.