Anatomy of the reproductive system

Question 1

Describe the regions of the pellvis

Answer 1

The pelvis can be divided into two regions:
- false pelvis or greater pelvis: this is the superior region related to upper parts of the pelvi bones and lower lumbar vertebrae. It is generally considered part of the abdominal cavity
- true pelvis or lesser pelvis: this is the region realted to the inferior parts of the pelvic bones, sacrum and coccyx. It has an inlet and outlet.

Question 2

Describe the position and contents of pelvis and perineum

Answer 2

The pelvic cavity is bowl-shaped.
The true pelvis consists of the pelvic inlet, walls and floor.
The pelvic cavity is continuous with the abdominal cavity superiorly and contains elements of the urinary, gastrointestinal and reproductive systems.
The perineum is inferior to the pelvic floor.
Its boundaries comprise the pelvic outlet.
The perineum contains the external genitalia and external openings of the genitourinary and gastrointestinal systems.

Question 3

Which three systems comprise the pelvic viscera?

Answer 3

Pelvic viscera come from three systems: digestive (rectum and anal canal), urinary system (bladder and urethra), and reproductive system (male and female).

Question 4

Describe the components of the the male reproductive system and describe their function briefly

Answer 4

• testis: responsible for sperm production and testosterone (male sex hormone) secretion
  
  • genital ducts: epididymis, vas deferens, ejaculatory duct and urethra - responsible for transporting, storing and assisting in maturation of sperm
  • accessory ducts: seminal vesicles, prostate and bulbourethral glands - responsible for secreting most of the liquid portion of the semen
  • external genitalia: scrotum and penis – responsible for protection and copulation

Question 5

Describe testes

Answer 5

The testes are paired, oval glands, suspended by spermatic cords in scrotum.
It is responsible for sperm production and testosterone secretion.

The spermatic cord is the tube shaped connection between the pouch in the scrotum and the abdominal wall.
It contains ductus deferens and associated blood vessels and lymph vessels.

The sides and anterior aspect of the testis are covered by a closed sac of peritoneum known as the tunica vaginalis. It is originally connected to the abdominal cavity but the connection is closed after testicular descent, leaving a fibrous remnant.

As it is made of peritoneum, the tunica vaginalis is **comprised of a parietal layer, visceral layer and cavity.

Each testis is composed of seminiferous tubules and interstitial tissue. This is enclosed in a fibrous capsule known as the tunica albuginea. The tunica albuginea also forms septa and lobules.

Question 6

Descrube the seminiferous tubules

Answer 6

Spermatozoa are produced by the seminiferous tubules. The tubules are modified at each end to become straight tubules, which connect to a collecting chamber called the rete testis in a thick vertically oriented wedge of connective tissue known as the mediastinum testis. This projects from the capsule into the posterior aspect of the gonad.
12 to 20 efferent ductules originate from the upper end of the rete testis, penetrate the capsule and connect with the epididymis.

Question 7

Describe the epididymis

Answer 7

The epididymis is roughly 6 metres long.
It is the site of maturation and storage of sperm.
During passage through the epididymis spermatozoa acquire the ability to move and fertilise an egg.
The epididymis courses along the posterolateral side of the testis.
It is comprised of two distinct parts:
- efferent ductules which form an enlarged coiled mass that sits on the posterior superior pole of the testis, forming the head of the epididymis
- true epididymis, a single long coiled duct into which efferent ductules drain, and continues inferiorly along the posterolateral margin of the testist as the body of the epididymis and enlarges to form the tail of the epididymis at the inferior pole of the testis.
The end of the epididymis is continuous with the ductus deferens.

Question 8

Descibe the ductus deferens

Answer 8

The ductus deferens is a long muscular duct that transports spermatozoa from the tail of the epididymis in the scrotum to the ejaculatory duct in the pelvic cavity.

It ascends in the scrotum as a part of the spermatic cord and passes through the inguinal canal via the superficial inguinal ring in the anterior abdominal wall.
After passing through the deep inguinal ring the ductus deferens bends medially around the lateral side of the inferior epigastric artery and cross the external iliac artery and the external iliac vein at the pelvic inlet to enter the pelvic cavity. It crosses the ureter, posterior to the bladder, and continues inferomedially along the base of the bladder.
It joins with the duct of the seminal vesicle to form the ejaculatory duct.

Note that before it merges with the seminal vesicle, it enlarges to form the ampulla of ductus deferens.

Question 9

Describe the spermatic cord

Answer 9

The spermatic cord is the tube shaped connection between the pouch in the scrotum and the abdominal wall.
It contains ductus deferens, testicular artery, pampiniform veins, lymphatic vessels and autonomic nerves.
It is surrounded by two layers of fascia
- external spermatic fascia
- internal spermatic fascia

Question 10

Describe testicular torsion

Answer 10

This occurs when the spermatic cord becomes twisted.
This can be a consequence of ectopic testes, where interrupted descent of the testis.

Question 11

List the accessory glands and describe their function

Answer 11

There are several accessory glands including the seminal vesicle, prostate and bulbourethral glands. These organs secrete most of the liquid portion of semen.

Question 12

Describe the prostate gland

Answer 12

The prostate gland is a fibromuscular organ.
It surrounds the urethra in the pelvic cavity.
It lies immediately inferior to the bladder, posterior to te pubic symphysis and anterior to the rectum.
It is shaped like an inverted rounded cone with a larger base, continuous with the neck of the bladder, and a narrow apex.

Question 13

Describe presentations of problems with prostate gland

Answer 13

clinicallyrelevant

When the median lobe (in central zone) of the prostate gland enlarges it impinges on urethra, causing difficult micturition. An example of this is BPH or prostate cancer.
This can be examined via DRE.

Question 14

Describe the penis

Answer 14

The penis is the copulatory organ in males.

It consists of:
- a root: which is attached, and consists of two crura (tapered corpora cavernosa) and one bulb (enlarged corpus spongiosum)
- body containing urethra and erectile tissue
- glans penis, which is the distal portion, enlarged and acron-shaped, contains foreskin or prepuce, and external urethral orifice

Question 15

Describe the scrotum

Answer 15

The scrotum is comprised of loose skin and superficial fascia.
Its function is to protect the testes and regulate temperature, which should be within 2 or 3 degrees of the body temperature.

There are two key muscles located in the scrotum:
- cremaster: skeletal muscle, which is continuous with the internal oblique muscle. It elevates the testes when cold
- dartos muscle which is comprised of smooth muscles, and contracts when cold, relaxes when hot

Question 16

Describe the uterine tubes

Answer 16

The uterine tubes extend from each side of the superior end of the body of the uterus to the lateral pelvic wall.
They are enclosed wthin the upper margins of the mesosalpinx portions of the broad ligaments (free edge).
The uterine tubes pass superiorly over and terminate laterally to the ovaries.
Thus the ovaries are suspended from the posterior aspect of the broad ligaments.

The uterine tube has an expanded trumpet-shaped end known as the infundibulum. The infundibulum curves around the superolateral pole of the ovary,
The margin of the infundibulum is rimmed with finger-like projections known as fimbriae.

The fimbriated infundibulum facilitates the collection of ovulated eggs from the ovary.

The lumen of the uterine tube opens into the peritoneal cavity at the narrowed end of the infundibulum. Medial to the infundibulum, the tube expands to form the ampulla and narrows to form the isthmus before merging with the body of the uterus.

The tubes open into peritoneal cavity via the ostium –this is the only direct communication to peritoneum from exterior.

The function of the fallopian tubes are to transport an oocyte to the uterus.

Fertilisation normally occurs in the ampulla.

Question 17

Describe the ovary

Answer 17

The ovaries lie adjacent to the lateral pelvic wall, just inferior to the pelvic inlet.
Each ovary is about 3 cm long and is suspended by a mesentery (mesovarium) that is a posterior extension of a broad ligament.
The ovary is also tethered by the ligament of ovary which tethers it to the uterus, and the suspensory ligament which attaches it to the pelvic wall and through which ovarian vessels pass through.

The ovary does not have a peritoneal covering.

Like the testes, the ovaries develop high on the
posterior abdominal wall and then descend before birth,
bringing their vessels, lymphatics, and nerves.

Unlike the testes, the ovaries do not migrate through the
inguinal canal into the perineum, but assume a position on the lateral wall of the pelvic cavity.

The ovaries are the site of oogenesis and female sex hormone secretion.

Mature eggs are ovulated into the peritoneal cavity and normally directed into the adjacent openings of the uterine tubes by cilia on the ends of the uterine tubes.

Question 18

Describe the uterus

Answer 18

The uterus is a hollow, thick- walled muscular organ.
It is continuous with the uterine tubes and vagina.
It is positioned in the midline between the bladder and rectum,

It consists of a body and cervix. Inferiorly it joins the vagina. Superiorly uterine tubes project laterally from the uterus and open into the peritoneal cavity immediately adjacent to the ovaries.

The body of the uterus is flattened anteroposteriorly and above the level of origin of the uterine tubes has a rounded superior end known as the fundus.

The cervix forms the inferior part of the uterus.
It is shaped like a short broad cylinder with a narrow central channel. The body of the uterus normally arches forward i.e. anteflexed on the cervix over the superior surface of the emptied bladder.

The cervix is angled forward or anteverted on the vagina so that the inferior end of the cervix projects into the upper anterior aspect of the vagina.

Because the end of the cervix is dome shaped, it bulges into the vagina, and a gutter, or fornix, is formed around the margin of the cervix where it joins the vaginal wall.

The tubular central canal of the cervix opens below as the external os into the vaginal cavity, and abode as the internal os into the uterine cavity.

It is comprised of three layers:
- perimetrium – peritoneum
- myometrium – smooth muscle
- endometrium – mucosa

It is the site of implantation of a fertilised ovum (normally) and the site of development of the fetus and labour.

On the surface of the uterus, midway between the apex and base, is a slight constriction known as the isthmus. The isthmus sits between the body and the cervix.
The myometrium here is narrower and thinner.

Question 19

Describe the cervix

Answer 19

The cervix forms the inferior part of the uterus.
It is shaped like a short broad cylinder with a narrow central channel. The body of the uterus normally arches forward i.e. anteflexed on the cervix over the superior surface of the emptied bladder.

The cervix is angled forward or anteverted on the vagina so that the inferior end of the cervix projects into the upper anterior aspect of the vagina.

Because the end of the cervix is dome shaped, it bulges into the vagina, and a gutter, or fornix, is formed around the margin of the cervix where it joins the vaginal wall.

The tubular central canal of the cervix opens below as the external os into the vaginal cavity, and abode as the internal os into the uterine cavity.

Question 20

Describe the vagina

Answer 20

The vagina is the female organ of copulation and a passageway of childbirth.
It is a muscular tube that is continuous with the uterus and contains thick epithelium.
There are no glands associated with the vagina.
The vagina courses from the pelvic cavity to the perineum i.e. from the uterus to the vaginal vestibule.

Question 21

List and briefly describe female external genitalia

Answer 21

• mons pubis: fat over pubic symphysis
  
  • clitoris - an erectile structure consisting of two crura, body and glans
  • labia minora: small folds of skin between majora and over vestibule
  • labia majora: bulky folds of skin
  • vestibule: the area between the labia minora with two openings: urethral and vaginal
  • hymen:membrane over vagina orifice

Question 22

Describe the uterine ligaments and pouches

Answer 22

clinicallyrelevant

The ligaments of the female reproductive system are crucial.
The round ligament runs from the uterus to the labia majora via the inguinal canal.

The broad ligament consists of peritineal folds/mesentery which connect uterus to the pelvic wall:
- mesometrium: which encloses the uterus
- mesosalpinx: which encloses the uterine tubes
- mesovarium: which encloses ovaries

Note also the vesico-uterine pouch and recto-uterine pouch or pouch of Douglas.
- vesicouterine pouch is a shallow space between the bladder and uterus, occurs anteriorly
- recto-uterine pouch is a deep space positioned posteriorly between the rectum and uterus
- it is an extremely important clinical region
- when patient is supine, the pouch is the lowest portion of the abdominopelvic cavity
- it is a site where infections and fluids typically collect
- it cannot be palpated transabdominally but can bee examined transvaginally and transrectal digital palpation
- it can be drained via the vagina in case of abscess

Question 23

Describe the relevance of understanding anatomical relationships

Answer 23

• pathogens can spread retrogradely from vagina to peritoneal cavity. Examples include pelvic inflammatory disease e.g. pelvic peritonitis or general peritonitis, as well as salpingitis from peritoneal infections
  
  • endometriosis- or retrograde menstruation (blood flows back into pelvis), where endometrial tissue grows on peritoneal surface of pelvic organs

Question 24

Describe the relationship between fundal height and age of foetus

Answer 24

During pregnancy the uterus dramatically expands superiorly into the abdominal cavity.
The age of the foetus can be roughly measured by fundal height:
- 12 weeks: pubic symphysis
- 20 weeks: umbilicus
- 36 weeks: xiphoid process

Question 25

List the support structures of the uterus

Answer 25

There are three sources of support for internal structures:
1. Pelvic diaphragm comprising levator ani muscle and coccygeus
- levator ani: iliococcygeus, pubococcygeus, and puborectalis
2. Perineal body or central tendon - a fibromuscular structure between the vagina and anal canal in the perineum
3. Three ligaments at the level of the cervix: transverse cervical ligament, pubocervical ligament and uterosacral ligament

Question 26

Describe how uterine prolapse occurs

Answer 26

Uterine prolapse occurs with damage to levator ani and ligaments during childbirth, or otherwise pelvic fascia atrophy post-menopause. They can no longer provide enough support for the uterus.

Question 27

Describe the blood supply of the female reproductive system

Answer 27

Blood supply of the female reproductive system is largely derived from the anterior trunk of the internal iliac artery.
Important vessels include:
- uterine artery
- ovarian artery and vein - with tubal and ovarian branches
- vaginal artery
- obturator arty
- superior vesical artery

Question 28

Describe the areas of the perineum

Answer 28

The perineum is a diamond shape structure, whose boundary is the pelvic outlet.
It is inferior to the pelvic floor or pelvic diaphragm. It contains external genitals and anus.
It can be divided into two areas:
- urogenital triangle, which is located anteriorly and contains external genitalia. Covered by perineal membrane (tough deep fascia)
- anal triangle which is posterior and contains the anus

Question 29

List and describe the common structures of the perineum in both males and females

Answer 29

There are several structures in the perineum common to both males and females:
- corpus cavernosum - which forms the crus and body of the clitoris or penis
- the bulb of vestibule which is the erectile structure on the side of the vagina. the corresponding structure on males is the corpus spongiosum, which is a single midventral structure containing the spongy urethra
- the greater vestibule glands or Bartholin’s glands which are positioned posterior to the bulb, and a duct opens into vestibule. the corresponding structure in males is the bulbourethral glands which are a deep perineal pouch that opens into the urethra

Other common structures include:
- levator ani
- deep perineal pouch: superior to perineal membrane
- perineal membrane
- superficial perineal pouch which sits between perineal membrane and superficial peritoneal fascia
- superficial fascia
- ischiocavernosus muscle which covers crura of penis and clitoris, and forces blood from crus into body
- bulbospongiosus muscle: bulb of vestibule/penis
- superficial transverse perineal membrane which stabilises the perineal body

Question 30

Describe the innervation and blood supply of perineum

Answer 30

• dorsal nerve of clitoris and penis
• perineal nerve
• inferior rectal nerve
• pudendal nerve (derived from S2-4)

As well as:
- dorsal artery of penis or clitoris
- perineal artery
- internal pudendal artery

Question 31

Describe the route of sperm

Answer 31

1. Spermatozoa produced in testes in semniferous tubules
2. Rete testis (network of tubules)
3. Epididymis (storage as they mature) head → body → tail
4. Vas deferens (travels through inguinal canal behind bladder)
5. Spermatic cord
6. (+ seminal vesicle duct) Ejaculatory duct → prostate
7. Prostatic urethra
8. Membranous urethra
9. Bulbar urethra
10. Spongy penile urethra