W1 - ANATOMY OF THE PELVIS AND PERINEUM & MALE REPRODUCTIVE SYSTEM

Question 1

What are the two main body cavities in the human body?

Answer 1

1. Dorsal body cavity
   
   1. Home to the central nervous system
   2. I.e. Brain and spinal cord
2. Ventral body cavity
   
   1. Is split up into two cavities - Thoracic and abdominopelvic cavity
   2. The thoracic cavity is demarcated by the 1st rib and 1st thoracic vertebrae and a solid diaphragm
   3. It is this diaphragm that separates the thoracic and abdominopelvic cavities
   4. Between the abdominal cavity and the pelvic cavity there is no such boundary
   5. As such the contents of the pelvic boundary (Particularly when women are pregnant) do share the space with the abdominal cavity
   6. Because of this sharing, organs of both of these cavities influence each other’s function

Question 2

What is the peritoneum? Explain its significance in both males and females

Answer 2

• The peritoneum is a double layered serious membrane that lines the abdominal and pelvic cavity
• It produces fluids that lubricate the abdominopelvic viscera, allowing the organs to move across each other (I.e. Through peristalsis)
• It is continuous with the pelvic cavity which means the organ can move smoothly against the parietal layer freely within its place in the pelvis
• This serous membrane goes all the way into the pelvis, however, it stops short of the pelvic floor
• In men it drapes over the structures of the pelvis (The bladder and rectum) to form the rectovesical pouch
• Pouches are ‘potential space’ - If there is a bleed, this is the first place to fill up
• In women, it drapes over the bladder, uterus and rectum forming a shallow recto-uterine pouch posteriorly (Between the rectum and uterus) and the vesico-uterine pouch anteriorly (Between the bladder and uterus)
• In women it also drapes over the fallopian tubes and ovaries laterally, it encloses them forming the broad ligament

Question 3

What is the false (greater) pelvis and the true (lesser) pelvis?

Answer 3

• The false (greater) pelvis - Lies superior to the pelvic inlet (superior pelvic aperture) and pelvic brim; cavity is part of abdominal cavity and contains abdominal viscera; bounded anteriorly by abdominal wall, laterally by iliac fossae and posteriorly by L5 and S1 vertebrae
• The true (lesser) pelvis - Lies inferior to pelvic brim, related to inferior parts of pelvic bones (pubis and ischium), sacrum and coccyx; limited inferiorly by pelvic outlet (inferior pelvic aperture) which is closed by pelvic diaphragm; cavity of true pelvis is the pelvic cavity; contains elements of urinary, gastrointestinal and reproductive systems; tilted anteroinferior in anatomical position
• Within females, the pelvic cavity contains most of the reproductive tract and in males it contains part of it

Question 4

What is the main strucutre of the pelvis and how are they joined posteriorly and anteriorly? Explain the clinical significance of the male and female pelvis

Answer 4

• The main structure of the pelvis contains two hip bones known as os coxa
• These two bones are joined by the sacrum which sits in between
• The two hip bones and the sacrum are joined posteriorly via two sacroiliac joints
• Anteriorly, these two hip bones then join together via the pubic symphysis, which is a fibrocartilaginous joint (During pregnancy this can expand up to 1cm)
• The coccyx is then the ‘tail bone’ at the inferior base of the sacrum
• The sacrum and the coccyx are considered to be a part of the axial skeleton
• The hip bones are considered to be a part of the appendicular skeleton (More related to the lower limb)
• Females pelvis have a more oval shaped inlet (As opposed to a heart shaped inlet in men) and is generally wider and flatter in shape in comparison to the male pelvis which is usually higher and narrower
• Furthermore, the female pelvis has a greater sub pubic angle (Thumb and forefinger) than the male (Forefinger and middle finger) to increase the space for a child to pass through
• These differences in the bony pelvis structurally means that functionally females are better adapted for parturition

Question 5

Describe the anatomical orientation of the pelvis using bony landmarks as reference

Answer 5

• In anatomical position, anterior superior iliac spine and superior edge of pubic symphysis lie in some vertical plane
• Pelvic inlet (sacral promontory, arcuate line and pecten pubis) angled 50-60 degrees relative to horizontal plane
• Urogenital part of pelvic outlet (ischiopubic arch) is nearly horizontal plane
• Therefore, urogenital triangle faces inferiorly; posterior part of outlet (ischial tuberosities to coccyx) more vertical
• Therefore, anal triangle faces more posteriorly

Question 6

What are the joints and stabilising ligaments of the human pelvis?

Answer 6

• Lumbosacral joints - Joints between the lumbar spine and the sacrum; part of the vertebrae column
• Zygapophysial joint - Between adjacent inferior and superior articular processes
• Intervertebral disc - Joins bodies of vertebrae L5 to S1
• Anterior longitudinal ligament - Joins the anterior parts of both discs
• Joint is angled posteriorly on the vertebrae L5 - Anterior part of the bone is thus thicker than the posterior part
• Reinforced by iliolumbar and lumbosacral ligaments
• Sacroiliac joints - Joints between the ilium and sacrum; they transmit forces from the lower limbs to the vertebral column
• Joint
  
  • Synovial joint between two L-shaped facets on the pelvic bone and sacrum
  • Surfaces are irregular and interlock and resist movement
• Stabilised by three ligaments
  
  • Anterior sacroiliac ligament
    
    • Thickening of fibrous membrane of the joint capsule
    • Anterior and inferior to the joint
  • Interosseous sacroiliac ligament
    
    • Largest and strongest ligament
    • Fills the gap in the L shaped joint
    • Attaches to roughened areas on the bone
  • Posterior sacroiliac ligament
    
    • Covers the interosseous sacroiliac ligament

Question 7

Which three bones make up the pelvis and where do they meet?

Answer 7

• The hip bone is made up of three bones during development
• At birth, these are three separate bones joined by cartilage at the acetabulum (Hip socket)
• Anteriorly - Pubis
• Inferiorly - Ischium
• Superiorly - The large ilium
• Together these make up the os coxa
• Bones of the os coxa meet at acetabulum

Question 8

What are the functions of the pelvis?

Answer 8

• Provide attachments for muscles of trunk (Assist in maintaining erect posture), and leg muscles (Locomotion)
• Transmit weight of upper body to lower limbs
• Supports abdominal organs
• Protects and supports pelvic viscera
• Provides attachment for erectile tissues and their associated skeletal muscles

Question 9

What is the line that denotes the separation between the true and false pelvis? Explain the location and shape of the pelvic inlet and pelvic outlet

Answer 9

• The line that denotes the separation between the true and false pelvis is known as the pelvic brim or the pelvic inlet
• The pelvic inlet is more or less a continuous ring around the top of the pelvis
• The pelvic outlet is more of a diamond shape, marked anteriorly by the pubic symphysis and pubic arch, the points of the ischial tuberosity and the coccyx posteriorly

Question 10

Which bones, muscles and ligaments make up the pelvic wall?

Answer 10

• The pelvic wall is made up of the bone’s inferior to the pelvic inlet, including the sacrum and coccyx
• Consists of two muscles
  
  • Obturator internus which wraps around to attach to the proximal part of the femur at the greater trochanter (Through the lesser sciatic foramen)
    
    • This provides protection and stability to the pelvic viscera and further is lined with obturator fascia (Connective tissue) which has a tendinous thickening that part of the pelvic diaphragm attaches to
  • The other muscle of the pelvic wall is the piriformis (Which means pear shaped)
    
    • It arises from the internal surface of the sacrum and wraps around to attach to the greater trochanter also (Though the greater sciatic foramen)
    • This piriformis splits the greater sciatic foramen into two parts, a superior and inferior section
• Consists of two ligaments
  
  • The sacrospinous ligament which travels from the sacrum to the ischial spine
  • Superficial to the above ligament is the sacrotuberous ligament, which travels from the ischial tuberosity to the sacrum
• These two ligaments functionally work to prevent the upward tilting of the sacrum
• The combination of these two ligaments and the greater/lesser sciatic notches become the greater sciatic foramen (Open in women and more closed in men), and the lesser sciatic foramen
• The greater sciatic foramen is sectioned into a superior and inferior region by the piriformis muscle
• Running through this inferior region behind the sacrospinous ligament and then through the lesser sciatic foramen into the perineum is the pudendal nerve and internal pudendal vessels along with the nerve to the obturator internus
• Thus, the greater sciatic foramen and the obturator canal supply the lower limbs, whereas the lesser factors sciatic foramen runs only to the perineum

Question 11

Observe and explain the differences between the greater sciatic notch and greater sciatic foramen; and the lesser sciatic notch and lesser sciatic foramen. Addtionally, observe and name the structures that pass through the foramina

Answer 11

• Greater sciatic notch closed off by sacrospinous ligament, forming greater sciatic foramen
  
  • Piriformis traverses greater sciatic foramen, dividing it into two parts; nerves and vessels to superior part of lower limb (gluteal region) pass through superior part; sciatic nerve and vessels and other nerves to superior and posterior thigh pass through inferior part
• Lesser sciatic notch enclosed by sacrospinous and sacrotuberous ligaments, forming lesser sciatic notch
  
  • Tendon of obturator internus passes through lesser sciatic foramen; also nerve to obturator internus, internal pudendal vessels and pudendal nerve (latter two supply perineum

Question 12

Observe and name the components of the pelvic diaphragm and describe how these muscles contribute to the pelvic floor

Answer 12

• From anterior aspect, pelvic diaphragm is funnel shaped and consists of two muscles on each side - Large anterolateral levator ani and smaller posterior coccygeus
• Levator ani made up of three indistinct parts
  • Pubococcygeus - Body of pubis to attach along midline as far posteriorly as coccyx; can be further subdivided into pubovaginalis/puborectalis (levator prostatae) and puboanalis muscles
  • Puborectalis - Originated in association with pubococcygeus and passes inferiorly on each side to form sling around gastrointestinal tract which maintains perineal flexure at anorectal junction
  • Iliococcygeus - Originates from tendinous arch in fascia covering obturator internus and joins to contralateral iliococcygeus in midline to form anococcygeal ligament/raphe
• Levator ani support pelvic viscera and function as sphincter of vagina and anus
• Coccygeus muscle overly sacrospinous ligaments; originate from ischial spine and pelvic surface of sacrospinous ligament and insert on lateral margin of coccyx and related boarder of sacrum
• Coccygeus muscles form posterior part of pelvic floor and support pelvic viscera; also pull coccyx forward after defecation and childbirth

Question 13

Where is the perineal membrane and deep perineal pouch? Describe the location of the two perineal triangles

Answer 13

• Superficial to the pelvic diaphragm is the perineal membrane (The lavata ani will connect here)
• This forms the deep perineal pouch which exists in the space between the perineal membrane and the pelvic diaphragm
• This pouch is basically a space between the membrane and the pelvic diaphragm
• Within this pouch is the deep transverse perineal muscles (Located posteriorly)
• Further (In both males and females) there is the external urethral sphincter
• In women only, there are a sphincter urethrovaginalis (Which supports the vagina and aids continents) and compressor urethrae (Which aids support and aids continents)
• The perineum is divided into the urogenital triangle (Anterior part with the perineal membrane) and the anal triangle (Between ischial tuberosity’s to the coccyx)

Question 14

What are the boundaries of the urogenital triangle?

Answer 14

• Urogenital triangle boundaries
  
  • Lateral - Ischiopubic rami
  • Posterior - Imaginary line between the ischial tuberosities
  • Anterior - Inferior margin of the pubic symphysis
  • Ceiling - Levator ani muscles

Question 15

What are the erectile tissues in both males and females? Which two sets of tissues join to form these erectile tissues? How does erection occur?

Answer 15

• 2 sets of tissues join to form the penis and clitoris
  
  • Cylindrical corpora cavernosa - One on each side of the urogenital triangle (Anchored to the pubic arch)
  • Other tissue is gender dependant
    
    • Women - Bulbs of vestibule; one on each side of the vaginal opening
      
      • Small bands of erectile tissues connect anterior of these to the glans clitoris
    • Men - Corpus spongiosum (single erectile mass) anchored to the base of the perineal membrane
      
      • Forms ventral part of the penis and expands to form the glans penis
      • Encloses the urethra (opens at the end of the penis)
• Clitoris
  
  • Composed of the corpus cavernosa and glans clitoris
    
    • Root (crura) is the attached part of the corpus cavernosa
    • Body formed by unattached part of the corpus cavernosa
      
      • Supported by ligaments
    • Glans clitoris is exposed in the perineum and can be palpitated through the skin
• Penis
  
  • 2 corpus cavernosa and 1 corpus spongiosum (enclosing the urethra)
    
    • Root - 2 crura attached to the pubic arch
    • Bulb of the penis - Proximal part of the corpus cavernosa is anchored to the perineal membrane
    • Body - Covered entirely by skin
  • Supported by suspensory ligament of the penis (pubic symphysis to the top of the penis, and fundiform ligament (slings around the penis from above)
• Erection - Arteries in the erectile tissues relax, causing blood to fill the tissues

Question 16

Where is the superficial perineal pouch? What is the contents of the superficial pernieal pouch?

Answer 16

• Is superficial to the deep perineal pouch
• This is where the erectile tissue and their muscles are found
• As a partner to the opposing deep muscle, in the superficial pouch there is the superficial transverse perineal muscle which helps support the perineal body
• Also, there is crura (Legs) of the clitoris and the penis which are covered by the ischiocavernosus muscle
• The ischiocavernosus muscle and the bulbospongiosus muscle work to force blood into the erectile tissues
• The bulb of vestibule is an erectile tissue

Question 17

What are the boundaries of the anal triangle? What is the major muscle in the anal triangle and what are its three parts?

Answer 17

• Faces posteroinferiorly (At an angle to the urogenital triangle)
• Defined by
  
  • Laterally - Medial margins of the sacrotuberous ligaments
  • Anteriorly - Horizontal line between two ischial tuberosities
  • Posteriorly - Coccyx
  • Superiorly - Pelvic diaphragm (Mostly levator ani and coccygeus muscles)
• Major muscle in the triangle is the external anal sphincter
  
  • Surrounds the anal canal - Formed by skeletal muscle
  • 3 parts
    
    • Deep - Thick, ring shaped, circles the upper part of the canal and blends with the fibres of the levator ani
    • Superficial - Also surrounds the anal canal, anchored anteriorly to the perineal body and posteriorly to the coccyx and anococcygeal ligament
    • Subcutaneous - Horizontally flattened disc of muscle beneath the skin

Question 18

What is the lateral and medial wall of the ischioanal fossae? What is the function of the ischioanal fossae?

Answer 18

• As the levator ani muscles create a bowl shape, it moves up and away from the perineal pouch and membrane, creating two effective gutters
  
  • Lateral wall is the ischium, obturator internus muscle and sacrotuberous ligament
  • Medial wall is the levator ani muscle
• The walls converge superiorly (where the levator ani muscles attach to the fascia)
• Allows for the movement of the pelvic diaphragm and expansion of anal canal during defecation

Question 19

What are the primary reproductive organs of the male reproductive system? Describe their location, clinical significance and venous supply

Answer 19

• Testes are the male gonads
• I.e. Primary reproductive organs
  
  • Thus, it produces gametes and sex hormones
• Everything else within the system is an accessory reproductive organ
• Location - The testes are suspended from, outside the body
  
  • This is due to the fact that sperm production is best at 3 degrees below core body temperature
• The testicular artery arises from the abdominal aorta
• The veins that drain the testes empty on the right-hand side into the inferior vena cava and on the left-hand side into the left renal vein (which then empties into the inferior vena cava)
• The scrotal sack is made up of different layers of skin and smooth muscle
• The lymphatic of the testis goes to the lumbar lymph nodes
• The lymphatic of the scrotum goes to the inguinal region

Question 20

Describe the decent of the testis

Answer 20

• The descent of the testis during embryological development is what creates the layers that surround them
• The testis form in the embryological upper abdominal wall (near the embryological kidneys)
• As it undergoes this descent, it goes through a number of layers that later on form the surrounding layers of the testes
• It follows this path
  
  • The testes first travel through the fascia that underlies the innermost muscle of the abdominal wall
    
    1. This is known as the transversalis fascia (fascia is just connective tissue that binds, protects and supports things)
  • It then goes through the internal oblique muscle (bringing some of those muscle fibres with it)
  • It then travels through the aponeurosis (fibrous tissue) of the external oblique which is the outermost layer
  • After this, the testis follows the path of the processus vaginalis
• The testis then descends via the processus vaginalis, an out-pouching of the of the peritoneum, and travels through the deep inguinal ring, following a mesenchymal cord called the gubernaculum
• This descent occurs from about 3 months preterm until about 2 years old
• The processus vaginalis itself will usually close by about 2 years of age and when this happens, a pouching around the testis is left (forming one of the distinct layers of the testis)

Question 21

What is the location and function of the inguinal canal? Describe its contents

Answer 21

• Location - Lateral to the inferior epigastric vessels (which is the marker for the deep inguinal ring, the marker for the inguinal canal)
• The superficial ring is superficial to the deep inguinal ring
• Around this is a fibrous tissue that forms a ring with either ends joining onto the pubis
• Function - The inguinal canal is home to the spermatic cord (where the spermatozoa travel through the reproductive system) and various vessels and nerves
• It also contains the ilioinguinal nerve (not directly associated with the spermatic cord)
• Gubernaculum draws testis into scrotum during foetal development
• Deep inguinal ring persists as defect in transversalis fascia
• Superficial inguinal ring formed by medial and lateral crura of external abdominal oblique aponeurosis and lateral half of pubic crest
• Spermatic cord passes through inguinal canal and consists of
  
  • Ductus deferens and its artery
  • Testicular artery
  • Pampiniform plexus
  • Cremasteric artery and vein
  • Nerves, lymphatics and remnants of processus vaginalis
• Ilioinguinal nerve also passes through inguinal canal

Question 22

Describe the layers of the scrotum

Answer 22

• The scrotum is made up of the layers that were created due to the decent of the testes
• These layers are (from deepest to most superficial)
• Tunica vaginalis
  
  1. This is formed by the closing of the processus vaginalis
  2. It is a double layered covering - Parietal and visceral
  3. Only covers the testis and epididymis
  4. Only covers these structures, does not go up into the inguinal canal
• Internal spermatic fascia
  
  1. Is derived from the transversalis fascia
• Cremasteric fascia
  
  1. Is a middle layer of the scrotum
  2. Is derived from the internal oblique
• Cremaster muscle
  
  1. Is a middle layer of the scrotum
  2. Is derived from the internal oblique
  3. Assists with temperature regulation
  4. It is partly skeletal muscle (Derived from the internal oblique muscle)
  5. It is also smooth muscle, this helps temperature regulation as when there is cold temperatures, the cremaster smooth muscle contracts, bringing the testis closer to the body where it is warmer (To regulate the temperature of the testis)
• External spermatic fascia
  
  1. Derived from the external oblique
• Dartos fascia and dartos muscle
  
  1. This layer is really closely associated with the skin of the scrotum
  2. The dartos muscle is smooth muscle that will contract in response to cold by wrinkling the skin, reducing surface area and reducing heat loss
  3. Works with the cremaster muscle to regulate temperature
  4. Also works to form a septum between the two testes so that they both have their own compartment to live in

Question 23

What is the spermatic cord? What are the structures that form the spermatic cord?

Answer 23

• Spermatic cord suspends in scrotum
• Is a cord like structure formed by the following structures
  
  • Ductus deferens
  • Artery that supplies the ductus deferens and its associated vein
  • The testicular artery and vein
  • Cremasteric artery and vein
  • The genital branch of the genitofemoral nerve (innovates the cremaster muscle)
  • Lymphatics
  • Sympathetic and visceral afferent nerve fibres
• The testicular artery and vein together form a pampiniform plexus which is used in the temperature regulation of the testis
• They cool veins coming back from the testis which wrap around the artery absorbing warm arterial blood
• This cools the blood travelling down, and warms the blood going up

Question 24

Contents of the spermatic cord

Answer 24

• 3 arteries, 3 nerves, 3 other things
  
  • 3 arteries
    
    • Testicular
    • Deferential
    • Cremasteric
  • 3 nerves
    
    • Genital branch of the genitofemoral
    • Cremasteric nerve
    • Sympathetic nerve fibres
  • 3 other things
    
    • Ductus deferens
    • Pampiniform plexus - Absorbs heat from arteries to cool the testes
    • Lymphatic vessels

Question 25

What defines this hernia as an indirect inguinal hernia rather than a direct inguinal hernia?

Answer 25

• At the points where the spermatic cord structures leave the pelvis, there are two defective or weak regions in the pelvic wall
• These two regions are
  
  • Through the deep inguinal ring
  • Through the abdominal wall itself
• These two regions are points of weakness that can result in herniation
• Inguinal herniation by definition is when an organ in the abdominal cavity (a loop of digestive tube, intestinal tube) bulges through the layers which are meant to be containing the abdomen
• There are two different types of inguinal hernias
  
  • Indirect
    
    • Are 5 times more common
    • Goes through the deep inguinal ring indirectly
    • This is lateral to the inferior epigastric vessels
    • Much more common in men than women
    • This type is also known as congenital as it seems to be as a result of a failure to close by the processus vaginalis
  • Direct
    
    • Is when herniation occurs through the connective tissue medial to the inferior epigastric vessels
    • Directly through the abdominal wall
    • Occurs more commonly with age

Question 26

What caused the bulge in an indirect hernia? What body layers would surround it as it proceeded into the scrotum, and from which abdominal layers are they derived?

Answer 26

• The bulge was most likely caused by a loop of small intestine that traversed the inguinal canal
• The layers surrounding the intestinal bulge in the scrotum are as follows
  
  • Skin, dartos muscle, membranous layer of the superficial fascia, external spermatic fascia (from external oblique aponeurosis), cremasteric fascia (from internal oblique aponeurosis) and the internal spermatic fascia (from transversalis fascia)

Question 27

How is the inguinal canal formed and which structures are associated with the inguinal canal in the male?

Answer 27

• The inguinal canal forms as the gubernaculum ‘draws the testis down’ into the scrotum during foetal development in the male (or during analogous development in the female)
• The deep inguinal ring persists as a defect in the transversalis fascia formed as the gonadal structures descended
• The superficial inguinal ring is formed by the lateral and medial crura of the external abdominal aponeurosis, and the lateral half of the pubic crest
• The spermatic cord (ductus deferens and its artery, testicular artery, pampiniform plexus, cremasteric artery and vein, nerves, lymphatics and remnants of processus vaginalis) passes through the inguinal canal in the male and the ilioinguinal nerve passes through the inguinal canal in both sexes

Question 28

Describe the gross anatomy of the testes

Answer 28

• On the outer most layer is the tunica vaginalis
• This is a double layer that forms from the processus vaginalis
• Between these two layers has a thin layer of fluid to allow for the free movement of the testis within its sac
• The next layer in from this is a thick dense layer of connective tissue called the tunica albuginea
• This extends down and around all of the seminiferous tubules to form lobules (around 250)
• These lobules contain 1-4 seminiferous tubules each
• The seminiferous tubules straighten into straight tubules and deliver the sperm into the rete testis
• After this they travel through efferent ductules into the head of the epididymis
• Sperm then gain motility as they travel down into the tail of the epididymis

Question 29

Describe the duct system

Answer 29

• Moving out of the testis towards the penis is the duct system
• The epididymis is lined with pseudostratified columnar epithelia and is continuous with the ductus deferens
• The ductus deferens is lined by the same epithelia but further has quite thick smooth muscle that provides peristaltic waves to allow sperm to travel up through
• After leaving the testis, the ductus deferens travels through the deep inguinal ring, along the pelvic wall and then past the back of the bladder
• The ductus deferens then expands into an ampulla (expanded part of a tube) and joins with the seminal vesicle (behind the bladder) at a point which is called the ejaculatory duct

Question 30

Observe and name the accessory glands of the male reproductive system. Describe the location, secretions and functions of each

Answer 30

• Seminal vesicles (2)
  
  • Produces 50-70% of the volume of the semen
  • It produces an alkaline solution which contains
    
    • Fructose as an energy source for the motility of spermatozoa
    • A coagulating enzyme so that the sperm can stick to the wall of the vagina until they gain motility
    • Prostaglandins (lipids that have a hormone effect) that cause the smooth muscle in the female reproductive system to create peristaltic waves to help the sperm travel
    • Other substances to enhance sperm motility and fertilising ability
  • It is located at the base of the bladder and is about the size of a little finger (5cm)
  • After it combines with the ductus deferens at the ejaculatory duct it releases through two openings into the urethra as it goes through the prostate gland
• Prostate gland (1)
  
  • Is a structure which lies at the base of the bladder
  • Secretes 30% of semen
  • At the top of it is the internal urethral sphincter (which is smooth muscle) which contracts to stop the back flow of semen into the bladder
  • It produces an acidic solution that contains citric acid, enzymes and prostate specific antigen (PSA)
  • During ejaculation, the smooth muscle of the prostate will contract and squeeze more semen out into the urethra
  • This is the point at which the internal urethral sphincter will contract to prevent the backflow of semen into the bladder
  • When men approach middle age, the prostate gland enlarges putting pressure on the bladder and making men feel like they need to urinate more often, whilst at the same time making it harder to urinate as it is compressing the urethra
  • The rectum is immediately posterior to the prostate
• Bulbourethral glands (2)
  
  • After the urethra has travelled through the prostate it exits and travels into the deep perineal pouch
  • This is where the last of the accessory glands (the bulbourethral glands) are located
  • Whilst they are located in the deep perineal pouch, they actually empty into the urethra in the bulb of the penis (spongy part of the urethra)
  • Function - These glands produce thick clear mucous prior to ejaculation that empties into urethra, lubricating glans of penis and neutralising traces of acidic urine in urethra
  • Does not contribute to the semen

Question 31

Observe and describe the relationship of the prostate gland to the base of the bladder. Predict the consequences of benign prostatic hypertrophy

Answer 31

• Prostate abuts inferior surface of bladder, surrounding urethra on exit from bladder
• Prostatic hypertrophy increases pressure of bladder - Feeling of needing to urinate more frequently, while simultaneously constricting urethra so increase difficulty passing urine.

Question 32

Describe the bulbospongiosus and ischiocavernosus muscles. Based on their position and appearance, briefly explain their role in micturition, ejaculation and/or maintaining an erection

Answer 32

• Bulbospongiosus forms sphincter that compresses bulb of penis and corpus spongiosum (erectile tissue surrounding urethra); anterior fibres encircle most proximal part of body of penis, compressing erectile tissue in root of penis - assist in erection by pushing blood into more distal parts of penis (glans) and impeding venous drainage; compression of bulb of penis helps to expel last drops of urine; reflex contraction in ejection is responsible for pulsatile emission of semen from penis
• ​Ischiocavernosus maintains erection of penis by compressing outflowing veins and pushing blood from crus into body of penis

Question 33

Observe and describe the arrangement of erectile tissues in the penis. How does the corpus spongiosum differ structurally and functionally from the corpora cavernosa?

Answer 33

• Corpus spongiosum found ventrally
• Encloses urethra and expands over distal end of body of penis to form glans penis
• Proximal expanded end (bulb of penis) attached to perineal membrane
• In erection, maintain patency of urethral lumen
• Corpora cavernosa paired and make up most of penis
• Found on dorsal aspect and fused medially in body of penis
• Proximal ends form crura, covered by ischiocavernosus muscle and attached to pubic arch of bony pelvis
• Crura support corpus spongiosum penis between and inferior to conjoint region

Question 34

Observe a dissected testis. Identify and describe the tunica vaginalis, tunica albuginea and epididymis.

Answer 34

• Tunica vaginalis is double layered closed sac derived from processus vaginalis (from early peritoneum); superficial to tunica albuginea and visible on sides and anterior aspect of testis
• Tunica albuginea is thick white connective tissue capsule surrounding seminiferous tubules and interstitial tissue
• Epididymis located on posterolateral aspect of testis; long coiled duct comprising head of epididymis of superior pole (contains efferent ductules emanating from rete testis) and true epididymis, itself formed by body of epididymis along posterolateral margin and enlarged tail of epididymis at inferior pole

Question 35

What are the four regions of the urethra?

Answer 35

• The urethra connects the urinary bladder to the penis and also serves as a conduit for semen and sperm during sexual intercourse
• There are four regions of the urethra
  
  • Preprostatic part of the urethra which is surrounded by the internal urethra sphincter
  • Prostatic part of the urethra is when it travels through the prostate
  • Membranous part of the urethra is the part that goes through the deep perineal pouch
  • Spongy part of the urethra

Question 36

Describe the anatomy of the penis

Answer 36

• Males have the corpus cavernosum (erectile tissue) that is attached along the pubic arch
• This is the main part of the penis
• This is then covered by the ischiocavernosus muscles on either side
• These muscles help to
  
  • Push blood into the corpora cavernosa
  • Stop the drainage of blood out of the veins
• These two jobs contribute to the erection of the corpora cavernosa
• The smaller part of the penis is the corpus spongiosum and is covered by two bulbospongiosus muscles joined at the midline raphe (the corpus spongiosum is one singular, not paired)
  
  • This muscle helps to empty the urethra
  • It gets rid of the last few drops of urine in men and expel semen also
• At the tip of the penis, the corpus spongiosum expands to form the glans penis (head of the penis)
• This is then covered by prepuce (foreskin) which is also a part of the corpus spongiosum
• The penis is suspended by a line of connective tissue (same one that separates the six pack) known as the fundiform ligament
• Further, there is a suspensory ligament which is connected to the pubic bone
• The penis in the anatomical position is described in its erect position and therefore lies against the abdomen, hence the dorsal surface of the penis is actually anterior when the penis is pointing down between the legs

Question 37

Briefly describe the pathway of blood supply (arterial and venous) and lymphatic drainage to and from the testes and penis

Answer 37

• The testicular artery arises from the abdominal aorta and supplies the testis and epididymis; the testicular artery is surrounded by the pampiniform plexus; the lymphatic vessels drain the testes and closely associated structures and pass to the lumbar lymph nodes; the lymphatic drainage of the scrotum is to the superficial inguinal lymph nodes
• The penis is supplied by the internal pudendal artery from the anterior trunk of the internal iliac artery; branches of the internal pudendal artery that supply the penis include the artery of bulb of penis that supplies the corpus spongiosum; urethral artery supplying penile urethra and surrounding erectile tissue to the glans; deep artery of penis enters crus and supplies crus and corpus cavernosum of body of penis; dorsal artery of penis that courses along dorsal surface of penis and supplies glans penis and superficial tissue of penis
• Venous drainage is by veins that accompany arteries, except deep dorsal vein that drains mainly glans and corpora cavernosa and connects with venous plexus surrounding prostate
• Lymphatic vessels accompany the internal pudendal blood vessels and drain mainly into internal iliac nodes in the pelvis

Question 38

Where will the lymphatic drainage of the testis go? Compare this with lymphatic drainage of the scrotum. Why is this difference clinically important?

Answer 38

• Lymphatic vessels drain the testes and closely associated structures and pass through the inguinal canal to the lumbar lymph nodes; the lymphatic drainage of the scrotum is to the superficial inguinal lymph nodes; this is clinically important in the spread of carcinomas; cancer of the testes metastasizes to the lumbar lymph nodes, just inferior to the renal veins; that of the scrotum metastasizes to the superficial inguinal lymph nodes, which lie in the subcutaneous tissue inferior to the inguinal ligament and along the terminal part of the great saphenous vein

Question 39

Describe the cooling mechanisms used to keep the testes at a temperature below core body temperature. What is the functional consequence of not cooling the testes?

Answer 39

• The testes are situated outside of the pelvic cavity in the scrotum where it is cooler; the scrotum responds to temperature changes
  
  • When it is cold, the testes are pulled closer to the warmth of the body and the skin is wrinkled to reduce the area exposed to the cold environment; when it is warm, the scrotum hangs lower
• These changes help maintain a fairly constant temperature and are performed by two sets of muscles; the dartos muscle is a layer of smooth muscle in the superficial fascia of the scrotum and wrinkles the scrotal skin; the cremaster muscles are bands of skeletal and smooth muscle that arise from the internal oblique muscles of the trunk and help elevate the testes
• The pampiniform plexus of veins (contains blood cooled from being in the testis) that surrounds the testicular artery absorbs heat from the artery before the blood reaches the testis
• Abundant production of viable sperm only occurs in an environment 1-2°C below core body temperature