PUDENDUM

• Aka, vulva, refers to the external genitalia
• Comprises structures that are sexually responsive and/or protect the vaginal opening.

Key features:

• Vaginal orifice (aka, opening).
• Hymen caruncles surround vaginal orifice; they are remnants of the hymen, which, at birth, partially closes the vaginal orifice and over time is stretched and/or torn by physical activity, tampon use, intercourse, etc.
• Ducts of greater vestibular glands release lubricating secretions upon sexual arousal.
• Urethral opening
• Ducts of the paraurethral glands vary in number (aka, lesser vestibular glands, Skene’s glands, female prostate gland); release mucous secretions, which may be a lubricating fluid, or may be involved in female ejaculation (which itself is a contentious topic).
• Glans clitoris is the “free” portion of the clitoris; the majority of the clitoris is deep to the skin.
• Labia minora:
  Medial and lateral folds.
  • Comprise erectile tissues and rich vasculature.
  • The right and left medial folds meet to form the frenulum of the clitoris; recall that a frenulum is a small fold of tissue that connects structures.
  • The lateral folds meet at the prepuce (aka hood), which covers the body of the clitoris.
  • Posteriorly, the folds merge to form the frenulum of the labia minora (aka, forchette).
• The area between the labia minora is the vestibule of the vagina.
• Labia majora:
  • Comprise adipose and smooth muscle tissue; the overlying skin has hair follicles and sebaceous glands.
  • Meet anteriorly at the mons pubis, which is the mound of fatty tissue superficial to the pubic symphysis.
  • Posteriorly, the labia majora are separated by the posterior commissure, which overlies the perineal body.

Superficial perineal pouch

• Potential space deep to the skin of the pudendum.
• Lies between the superficial perineal fascia and the perineal membrane.
• Contains erectile tissues and their overlying muscles.
• Pubic rami anchor the soft tissues.
• Perineal membrane has openings through which the vagina and urethra pass
• Clitoris:
  • Comprises the paired corpora cavernosa, which are erectile tissues.
  • Anchored to the pubic symphysis via the suspensory ligament.
  • Crus (plural = crura) the lateral “leg” that attaches to the pubic rami and perineal membrane.
  • Body is the “free part” where the corpora cavernosa meet medially.
  • Glans is the exposed end of the body.
  • Average clitoral length is between 2-5 cm, with significant interindividual variation.
• Bulbs of the vestibule lie lateral to the opening of the vagina (deep to the labia minora) and are connected to the glans of the clitoris:
  • They comprise erectile tissues and are rich in vasculature; in fact, some authors classify them as corpus spongiosum and/or as components of the clitoral root.
• Greater vestibular glands (aka, Bartholins’ glands); they release lubricating secretions during sexual arousal
• Muscles that overlie the erectile tissues:
  • Ischiocavernosus overlies the crura of the clitoris.
  • Bulbospongiosus overlies the bulb of the vestibule and the greater vestibular gland.
  • Force blood into the body and glans of the clitoris during sexual arousal.
• Superficial transverse perineal muscles arise from the ischial bones and meet at the perineal body, which they help to stabilize.

Clinical Correlation:

• Episiotomies are surgical cuts through the perineum between the vagina and the anus to widen the vaginal opening during childbirth.
• Current research shows that most women do not need episiotomies and that the risks, which include infection, increased tearing, and, therefore, longer recovery times, outweigh the benefits in many cases.

Breast (aka, mammary gland)

• Key reproductive function of the female breast is to produce and transport milk during the hormonally regulated process of lactation.
• Anatomy of male and female breasts is similar, though adult female breasts are much more developed, especially in those who are pregnant or lactating.

Anatomical context:

• Pectoralis major is the large muscle deep to the breast.
• Pectoralis fascia that overlies the muscle.
• Retromammary space (aka, bursa), which is a potential space between the pectoralis fascia and the breast tissue; it allows for movement of the breast.

External features:

• Nipple
• Areola is the darker ring of skin that surrounds nipple.
• Sebaceous glands lie deep to the areola; they give it a slightly bumpy appearance. During breastfeeding, sebum is released to reduce chaffing and cracking of the skin overlying the nipple.

Internal features:

• Fatty matrix
• Suspensory ligaments (aka, Cooper’s ligaments) weave through the fatty matrix and attach the breast tissue to the pectoralis fascia and the skin.
• Lobe is a section of breast tissue between the suspensory ligaments; each breast typically comprises 15-20 lobes.
• Glandular tissue
  Comprises lobules.
  Lobules are collections of terminal duct lobular units: alveoli (which produce milk) that drain into terminal ducts.
• Smaller lactiferous ducts drain into main lactiferous ducts.
• Main lactiferous ducts open at the nipple.
• Lactiferous sinus is a small reservoir for milk.

Clinical Correlation:

Breast cancer typically begins within the cells of the lobules or ducts. If cancerous cells travel nearby axillary lymph nodes, they can be distributed to other parts of the body via the lymphatic vessels. Thus, early detection of breast cancer (before it spreads), improves prognosis.

Ovarian hormones regulate the functioning of the uterine tubes and uterus.

Uterine tubes

3 tunics of the uterine tubes:

• Serosa comprises the outermost layer.
• Muscularis is the muscular middle layer.
• Mucosa comprises ciliated epithelia; it faces the lumen of the tube.

Clinical Correlation:

Ectopic Pregnancy

These tunics facilitate fertilization via:

• Peristaltic contractions and cilia that transport ova and sperm.
• Mucosal secretions that initiate the final stages of sperm maturation.

Tube Segments

• Uterine (aka, intramural) segment arises within the uterus; it regulates the passage of sperm and bacteria into the uterine tubes.
• Isthmus comprises a relatively thick muscularis layer; sperm are held here for about 24 hours, while uterine tube secretions stimulate capacitation, which is required for fertilization.
• Ampulla is the thin-walled, dilated portion; the ampulla is the most common site of fertilization (joining of ovum and sperm).
• Infundibulum is the wide “trumpet-shaped” lateral end of the uterine tube.
• Fimbriae are the terminal finger-like projections.
• The fimbriae “catch” the ovulated ova from the ovaries as they burst into this space.
• Ova are released into the peritoneal cavity and (usually) swept up by the fimbriae.
• Abdominal ostium is the opening of the uterine tube to the peritoneal cavity.

Uterus

3 layers of the uterine wall:

• Perimetrium is the outermost layer.
• Myometrium comprises interweaving bundles of smooth muscle that contract during orgasm and to expel menstrual fluid during menstruation and the fetus and placenta during childbirth.
• Endometrium is the dynamic innermost layer that undergoes periods of regeneration, differentiation, and shedding over the course of the menstrual cycle.
  • When conditions are favorable, a fertilized ovum will implantinto the endometrium, and menstruation will not occur.

Regions of the uterus:

• Uterine cavity is the lumen of the uterus.
• Uterine horns are continuous with the uterine tubes.
• Body comprises the majority of the uterus.
• Superiorly is the fundus, which is the region above to the uterine cavity.
• Inferiorly is the isthmus, which is where the uterus constricts.
• Cervix is most inferior region of uterus.
  • Internal os is the opening between the cervix and the isthmus.
  • External os is the opening between the cervix and the vagina.
  • Cervical canal is between the internal and external os.
  • Glands within the cervical canal secrete mucus, which changes over the course of the menstrual cycle to allow or block the entry of sperm into the uterus.

Clinical correlations:

• Infections (such as pelvic inflammatory disease) can spread from the uterine tubes to the peritoneal cavity. Agglutination of the fimbriae can close off the opening and prevent the spread of infection, but, because the uterine tube is effectively sealed off, fertility is impaired.
• Cervical cancer is most commonly caused by HPV (human papillomavirus); thus, HPV vaccinations help prevent cervical cancer.

Ovarian hormones regulate the functioning of the uterine tubes and uterus.

Uterine tubes

3 tunics of the uterine tubes:

• Serosa comprises the outermost layer.
• Muscularis is the muscular middle layer.
• Mucosa comprises ciliated epithelia; it faces the lumen of the tube.

Clinical Correlation:

Ectopic Pregnancy

These tunics facilitate fertilization via:

• Peristaltic contractions and cilia that transport ova and sperm.
• Mucosal secretions that initiate the final stages of sperm maturation.

Tube Segments

• Uterine (aka, intramural) segment arises within the uterus; it regulates the passage of sperm and bacteria into the uterine tubes.
• Isthmus comprises a relatively thick muscularis layer; sperm are held here for about 24 hours, while uterine tube secretions stimulate capacitation, which is required for fertilization.
• Ampulla is the thin-walled, dilated portion; the ampulla is the most common site of fertilization (joining of ovum and sperm).
• Infundibulum is the wide “trumpet-shaped” lateral end of the uterine tube.
• Fimbriae are the terminal finger-like projections.
• The fimbriae “catch” the ovulated ova from the ovaries as they burst into this space.
• Ova are released into the peritoneal cavity and (usually) swept up by the fimbriae.
• Abdominal ostium is the opening of the uterine tube to the peritoneal cavity.

Uterus

3 layers of the uterine wall:

• Perimetrium is the outermost layer.
• Myometrium comprises interweaving bundles of smooth muscle that contract during orgasm and to expel menstrual fluid during menstruation and the fetus and placenta during childbirth.
• Endometrium is the dynamic innermost layer that undergoes periods of regeneration, differentiation, and shedding over the course of the menstrual cycle.
  • When conditions are favorable, a fertilized ovum will implantinto the endometrium, and menstruation will not occur.

Regions of the uterus:

• Uterine cavity is the lumen of the uterus.
• Uterine horns are continuous with the uterine tubes.
• Body comprises the majority of the uterus.
• Superiorly is the fundus, which is the region above to the uterine cavity.
• Inferiorly is the isthmus, which is where the uterus constricts.
• Cervix is most inferior region of uterus.
  • Internal os is the opening between the cervix and the isthmus.
  • External os is the opening between the cervix and the vagina.
  • Cervical canal is between the internal and external os.
  • Glands within the cervical canal secrete mucus, which changes over the course of the menstrual cycle to allow or block the entry of sperm into the uterus.

Clinical correlations:

• Infections (such as pelvic inflammatory disease) can spread from the uterine tubes to the peritoneal cavity. Agglutination of the fimbriae can close off the opening and prevent the spread of infection, but, because the uterine tube is effectively sealed off, fertility is impaired.
• Cervical cancer is most commonly caused by HPV (human papillomavirus); thus, HPV vaccinations help prevent cervical cancer.

TESTES

• The primary sex organs of the male; they produce sperm and hormones.
• Their anatomical position “outside” of the body reflects a physiologic necessity: spermatogenesis (formation of sperm) requires a temperature slightly lower than that of the body.

Tunica albuginea

• Fibrous outer surface of the testis

Mediastinum of the testis

• Where the tunica albuginea forms a thickened ridge along the posterior aspect.
• Septa extend from the mediastinum, which separate the lobules.

Seminiferous tubules

• Lie within the lobules
• Sites of sperm production.
• Specialized cells within the lobules produce hormones that support sperm maturation.

Straight tubules

• Transport sperm from the seminiferous tubules to the rete testis

Rete testis

• Comprises a network of tubules within the mediastinum of the testis.

Efferent ductules

• Converge to deliver sperm to the epididymis

Epididymis

• Stores developing sperm
• Head comprises the tightly coiled merger of the efferent ductules
• Body comprises a singular long coiled duct
• Tail of the epididymis is continuous with ductus deferens

Ductus deferens

• Transports sperm to ejaculatory duct

Tunica vaginalis

• Double-layered sac that comprises a visceral layer, which is closely adhered to the tunica albuginea of the testis, and, a parietal layer, which is in contact with the innermost layer of the scrotum and spermatic cord.
• The cavity of the tunica vaginalis is the space between these two layers, and contains a small amount of fluid, which allows for movement of the testicles within the scrotum.

Spermatic cord

• Passes through the inguinal canal, which is an oblique passageway in the anterior abdominal wall.
• Comprises blood vessels, nerves, the ductus deferens, and several layers of tissue that collectively suspend the testes within the scrotum.
• Prior to testicular descent, the spermatic cord develops as an outpocket of the anterior abdominal wall; thus, its three coverings are derived from the fascial layers of the anterior abdominal wall.

Spermatic Cord Layers:

• Internal spermatic fascia, which is derived from the transversalis fascia of the anterior abdominal wall.
• Cremasteric fascia with muscle fibers, which is derived from the internal oblique fascia and muscle.
• External spermatic fascia, which is derived from the external oblique fascia/aponeurosis.

Scrotum

• A cutaneous sac that holds the testes.
• Dartos fascia and muscle is the inner layer, gives rise to scrotal septum, which separates testes within scrotum.
• Skin is outermost layer of scrotum.
  The dartos muscle contracts when cold to wrinkle and thicken the skin, which helps to reduce heat loss.

Clinical correlation:

Torsion of the spermatic cord (aka, testicular torsion) can disrupt blood supply to the testis and cause necrosis; twisting can occur because of defects in the supporting connective tissues.

Key Function:

Conduct urine and semen to the outside environment.

Key Anatomical Features:

Skin

• Prepuce covers glans, is retractable in the adult.

Vessels

• Superficial dorsal vein and artery
• Deep dorsal vein
• Deep arteries within corpus cavernosa

Connective tissues

• Deep fascia surrounds erectile bodies and binds them together
• Intercavernous fascia separate corpora cavernosa from corpus spongiosum.

Erectile bodies

• Covered in tunica albuginea
• Comprise vascular tissues that engorge with blood upon arousal.

Singular corpus spongiosum surrounds the urethra:

• Glans is distal expansion; corona is rim of glans
• Bulb is the widened proximal end
• The bulb anchors the corpus spongiosum to the perineal membrane (not shown);
• The bulb is wrapped in the bulbospongiosum muscle, which contracts to: force blood into the erectile tissues, eject residual urine from the urethra,
  and produce pulsatile movements during ejaculation.

Paired corpus cavernosa (singular = cavernosum)

• Lie dorsal to corpus spongiosum
• Crus (singular = crura) of the corpus cavernosa extend laterally
• Crus attach to the pubic arch of the pelvis (not visible here), and are wrapped by ischiocavernosus muscles; like the bulbospongiosum, these muscles force blood into the erectile tissues.

Root

• Comprises bulb and crus of penis

Shaft

• Free, pendulous portion of penis between root and glans

Urethra

• Conducts semen to external environment
• Terminates at external urethral orifice
• Urethral glands secrete mucus to protect urethra from urine

Anatomical orientation

• Dorsal surface faces the torso
• Ventral surface faces away from the torso.

Semen/Seminal Fluid:

Semen (aka, seminal fluid)

• Comprises sperm and seminal plasma.

Sperm

• Gametes (aka, sex cells), produced by the testes

Seminal plasma

• Nourishes and protects the sperm
• Produced and secreted by the seminal vesicles, bulbourethral glands, and urethral glands.

Origins of semen:

Bulbourethral glands (aka, Cowper’s glands)

• Secrete lubricating mucous prior to arrival of the rest of the semen into spongy urethra

Ampulla of ductus deferens

• Drains sperm

Seminal vesicles

• Drain viscous, sugary seminal plasma fluid

Ejaculatory duct

• Where sperm and seminal vesicle secretions mix; merger of ductus deferens and seminal vesicle

Prostate gland

• Secretes alkaline, enzyme-rich fluid that protects sperm

Ejaculate

• Semen after it has been ejected from the urethra.

Clinical correlation

• Male circumcision is the surgical removal of the some or all of the prepuce, which leaves the glans exposed.
• A “fractured” penis occurs when the tunica albuginea tears, typically as a consequence of abrupt angling of an erect penis; swelling and bruising result.

Thoracic cage

• Protects the chest organs (the heart and lungs).

Main Structures:

The sternum (aka, breastbone) lies anteriorly.
12 thoracic vertebrae lie posteriorly.
12 ribs articulate with the thoracic vertebrae.

Sternum

• Manubrium (superiorly)
• Body (long and flat, middle portion)
• Xiphoid process
  • Easily injured during chest compression (for CPR).
• Sternal angle
  • Where manubrium and body meet
  • Easily palpated to find rib 2
• Sternal indentations:
  • Jugular notch (aka, suprasternal notch) is on the superior border of the manubrium.
  • Clavicular notches are to the sides of the jugular notch; these are where the clavicles (aka, collarbones), articulate with the sternum.
  • Costal notches articulate with the costal cartilages of the ribs (“costal” refers to the ribs).

Rib Types

• True ribs
  • Ribs 1-7; articulate with the sternum directly via their costal cartilages.
• False ribs
  • Ribs 8-12; do not articulate directly with the sternum.
  • Ribs 11 and 12 are “floating ribs,” do not articulate at all with the sternum.

Rib Features

• Head
  • Articulates with the vertebral body; typically comprises two articular surfaces separated by a bony crest.
• Neck
  • Extends from the head, and terminates at the tubercle.
• Tubercle
  • Comprises an articular facet, which is where the rib articulates with the transverse process of the vertebra.
• Shaft
  • Longest portion of the rib, extends from tubercle to rib end.
• Angle
  • Bend in rib, just lateral to tubercle.

Rib/vertebra articulation

• Head and tubercle of rib articulate with body and thoracic process of vertebrae.

Intercostal spaces

• The spaces between the ribs
• House muscles and neurovascular structures.
  • Intercostal neurovascular bundle, especially the intercostal artery, must be avoided during insertion of a chest tube.

Key Points

• The posterior abdominal wall muscles contribute to respiration and movement of the torso and thigh.
• The posterior abdominal wall is bound superiorly by the diaphragm, and, inferiorly, by the ilia of the pelvis.

Quadratus lumborum:

• Originates on the iliac crest and the transverse process of L5.
• Inserts on the transverse processes of L1-L4, and along the inferior border of rib 12 (intertextual variation regarding the specific origins and insertions of quadratus lumborum exists).
• It depresses and stabilizes rib 12, and laterally flexes the torso.

Diaphragm:

• Originates on the internal surface of the sternum, costal cartilages of ribs 6-12, and lumbar vertebrae L1-L3
  Inserts into the central tendon.
• Contraction of the diaphragm expands the thoracic cavity, which decreases intrapulmonary pressure and induces inspiration (inhalation).

Iliacus:

• Originates on the iliac fossa and lateral sacrum.
• Inserts on the lesser trochanter of the femur.
• Flexes the thigh at the hip.

Psoas major:

• Originates on the lateral aspects and intervertebral discs of vertebrae T12-L5 Inserts, with iliacus, on the lesser trochanter.
• Flexes the thigh at the hip.

Psoas minor:

• Originates on the lateral aspects and intervertebral discs of T12-L1
• Inserts on the pectineal line on the pelvis.
• Weak trunk flexor; it does not travel to the thigh with psoas major, and, therefore, does not act on the thigh.

Key Point:

• The muscles of the anterior abdominal wall comprise thin sheets that compress and protect the abdominal contents, and, therefore, are involved in a range of actions, including defecation and micturition, parturition, and forceful expiration of air (as in heavy breathing, coughing, or yelling).

External oblique:

• Originates from the external surfaces of ribs 5-12
• Inserts on the ilium (the anterior ½ of the iliac crest and the anterior superior iliac spine), the pubic tubercle, and, via its aponeurosis, the linea alba.
• The inferior border of this aponeurosis forms the inguinal ligament, which is a strong cord of connective tissue to which other muscles attach.
• The fibers of the external oblique extend inferomedially from their posterior origins.
• The external obliques compress the abdomen and flexes and rotates the trunk.

Internal oblique:

• Originates on the lateral 2/3rds of the inguinal ligament, the iliac crest, and the thoracolumbar fascia.
• It inserts at the linea alba, pubic crest and pectineal line, and external surfaces of ribs 9-12; it gives rise to an aponeurosis, which inserts at the midline.
• Its fibers run superomedially at an oblique angle.
• The internal oblique works with the external oblique to compress the abdomen and flex and rotate the trunk.

Rectus abdominis:

• Originates on the pubic crest and pubic symphysis of the pelvis.
• Inserts into the xiphoid process of the sternum and on the external surfaces of the costal cartilages of ribs 5-7.
• Rectus abdominis depresses the ribs and flexes the trunk.
• Rectus sheath covers anterior and posterior surfaces of rectus abdominis; it is formed by the aponeuroses of the other abdominal muscles.
• Its fibers run vertically in four segments that are separated by horizontal tendinous intersections.

Transversus abdominis:

• Originates on the lateral 1/3rd of the inguinal ligament, the iliac crest, the thoracolumbar fascia, and the external surfaces of the costal cartilages of ribs 7-12.
• Inserts along the linea alba, pubic crest, and pectineal line.
• Transversus abdominis compresses the abdomen and depresses the ribs.