116 Questions
What type of epithelium lines the anal canal?
Columnar epithelium
What is the name of the vertical folds in the anal canal?
Anal columns
What nerve supplies the anal canal?
Somatic inferior rectal nerve
What is the arterial supply to the anal canal?
Inferior rectal artery
What is the venous drainage of the anal canal?
Inferior rectal vein
What type of sensation can the anal mucosa detect?
Stretch only
What is the approximate length of the anal canal?
1.5 inches (4 cm)
Which muscle helps to keep the lateral walls of the anal canal in apposition?
Levator ani
What is the name of the ligament that overlies the border of the gluteus maximus muscle?
Sacrotuberous ligament
In which direction does the anal canal pass from the rectal ampulla to the anus?
Downward and backward
What is the name of the triangle that contains the anus and the anal canal?
Anal triangle
What is the name of the muscle that forms the boundary of the anal triangle?
Gluteus maximus
What is the name of the structure that lies in the midline of the anal canal?
Icbloanal fossa
What is the name of the nerve that supplies the anal canal?
Inferior rectal nerve
What is the function of the longitudinal fibers of the anal walls and the puborectalis muscle?
To return the mucosa to the anal canal
Which artery supplies the lower half of the anal canal?
Inferior rectal artery
What is the function of the anal sphincters?
To close the lumen of the anal canal
Through which foramen does the internal pudendal artery pass?
Lesser sciatic foramen
What is the main tributary of the inferior mesenteric vein?
Superior rectal vein
What is the mass of fibrous tissue lying between the anal canal and the coccyx?
Anococcygeal body
What is the ischioanal fossa also known as?
Ischiore
Which nerve travels with the internal pudendal artery?
Pudendal nerve
What is the origin of the mucous membrane of the upper half of the anal canal?
Hindgut entoderm
What is the main direction of lymphatic drainage of the anal canal?
Upward along the superior rectal artery
What is the structure that lies posteriorly to the anal canal?
Anococcygeal body
What is the artery that supplies the anal canal?
Superior rectal artery
What is the structure that lies anteriorly to the anal canal in the male?
Membranous part of the urethra
What is the origin of the mucous membrane of the lower half of the anal canal?
Ectoderm of the proctodeum
What is the primary function of the puborectalis muscle?
To form a sling around the junction of the rectum and anal canal
Which nerve supplies the deep part of the external anal sphincter?
Perineal branch of the fourth sacral nerve
What is the attachment point for the deep part of the external anal sphincter?
No bony attachment
What is the primary function of the external anal sphincter?
To maintain continence
Which muscle is responsible for encircling the anal canal?
Puborectalis muscle
What is the origin of the deep part of the external anal sphincter?
Pubic bone
Which structure is formed by the combination of the external anal sphincter and puborectalis muscle?
Voluntary anal sphincter
What is the nerve supply of the puborectalis muscle?
Perineal branch of the fourth sacral nerve
What is the purpose of the rhythmic contractions of the bulbospongiosus muscles during ejaculation?
To compress the urethra and facilitate ejaculation
What is the function of the internal urethral sphincter during ejaculation?
To prevent reflux of spermatozoa into the bladder
What is the origin of the dorsal artery of the penis?
The internal pudendal artery
What is the name of the space that the internal pudendal artery enters after piercing the perineal membrane?
Deep perineal space
What is the term for the fluid that constitutes the spermatozoa and the secretions of the several accessory glands?
Semen
What is the length of the prostatic urethra?
1.25 in.
What is the direction of the anal canal from the rectal ampulla to the anus?
Not mentioned
What is the possible consequence of repeated inflammation of the prepuce?
All of the above
What is the site of the passage of the internal pudendal artery?
Through the perineal membrane
At what angle is the penis held during circumcision?
Right angle to the anterior abdominal wall
What is felt when the catheter reaches the intermediate part of the urethra?
Resistance due to the tone of the external urethral sphincter
What is the narrowest part of the entire urethra?
External orifice at the glans penis
What is the location of the parasympathetic outflow in the pelvic splanchnic nerves?
Second, third, and fourth sacral segments
Why is prophylactic circumcision commonly practiced?
Both a and b
What happens to the urethra within the glans?
It dilates to form the fossa navicularis
What is the function of the upper part of the external urethral sphincter?
To extend up along the prostatic urethra as far as the neck of the bladder
What is the purpose of gentle traction during circumcision?
To hold the penis erect
What is the name of the muscle that forms a true sphincter-like unit encircling the intermediate part of the urethra?
Sphincter Urethrae Muscle
What is the effect of parasympathetic stimulation on the helicine arteries?
Vasodilatation
What is the next step after the penis is lowered towards the thighs during circumcision?
The catheter is gently pushed through the sphincter
What is the path of the postganglionic fibers after synapsing on the postganglionic neurons?
They run through the prostadc nerve plexm and join the cavernous nerves
What is the effect of parasympathetic stimulation on the erectile tissue?
It causes the erectile tissue to expand
What is the name of the part of the external urethral sphincter that is between the perinea membrane and the prostate?
Inferior portion of the external sphincter
What is the function of the sphincter urethrae muscle?
To compress the intermediate part of the urethra
What is the function of the sensory endings in the epithelium of the glans?
To detect various types of sensations
Which artery supplies the clitoris and most of the surrounding area?
Internal pudendal artery
What is the name of the space posterior to the glans clitoris and between the labia minora?
Vestibule space
What is the function of the branches of the pudendal nerve?
To carry sensory fibers from the clitoris
What is the path of lymph drainage from the skin of the vulva?
Medial group of superficial inguinal nodes
What is the function of the labia majora, labia minora, and mons pubis?
To protect the clitoris and surrounding area
What is the relationship between the blood supply, lymph drainage, and nerve supply of the clitoris and penis?
Identical patterns in both
What is the location of the greater vestibular glands?
Between the labia minora
What is the function of the superficial transverse perineal muscles?
To fix the perineal body in the center of the perineum
Which arteries supply the scrotum?
All of the above
What is the function of the perineal branch of the pudendal nerve?
To supply the skin and muscles of the scrotum
Where do the contents of the scrotum (testis and epididymis) drain lymphatically?
Lumbar (paraaortic) lymph nodes at the level of the first lumbar vertebra
What is the perineal body?
A small mass of fibrous tissue that attaches to the center of the perineum
Which muscles attach to the perineal body?
External anal sphincter, superficial transverse perineal muscles, and bulbo cavernosus muscle
What is the function of the arteriovenous anastomoses in the scrotum?
To promote heat loss and assist in the environmental control of the temperature of the testes
What is the blood supply to the scrotum?
External pudendal branches of the femoral artery and ClOtal branches of the internal pudendal arteries
What is the main reason for the higher incidence of cystida in females compared to males?
The shorter length of the female urethra
What is the significance of the bluish discoloration of the vulva and vagina during pregnancy?
It is a result of venous congestion
What is the characteristic of the epithelium lining the vagina?
It is squamous and stratified
Why is catheterization easier in females compared to males?
The female urethra is shorter and wider
What is the significance of digital examination of the vagina?
It provides valuable information about the health of the vaginal walls
What is the consequence of repeated inflammation of the prepuce?
It can lead to phimosis
What is the advantage of the acidic pH of the vagina?
It decreases the risk of infection
What glands can become infected in the female reproductive system?
All of the above
What is the primary cause of types 1 and 2 epispadias?
Failure of the bud of ectodermal cells to grow into the substance of the glans
What is the name of the structure that forms the boundary of the anal triangle?
Puborectalis muscle
What is the location of the meatal orifice in the penoscrotal variety of epispadias?
In the midline of the scrotum
What is the name of the ligament that overlies the border of the gluteus maximus muscle?
Sacrotuberous ligament
What is the direction of the anal canal from the rectal ampulla to the anus?
Inferiorly and posteriorly
What is the name of the tissue that develops within the mesenchymal core of the penis?
Erectile tissue
What is the term for the fluid that constitutes the spermatozoa and the secretions of the several accessory glands?
Semen
What is the purpose of the frenulum?
To attach the skin to the ventral aspect of the root of the glans
What is the narrowest part of the entire urethra?
Membranous urethra
What is the result of the two genital folds fusing together progressively along the shaft of the phallus?
Formation of the penile urethra
In which direction does the penile urethra open?
At the tip of the glans
What is the name of the space that the internal pudendal artery enters after piercing the perineal membrane?
Pudendal canal
What is the origin of the dorsal artery of the penis?
Internal pudendal artery
What is the term for the condition where the penis is curved in a downward or ventral direction?
Chordee
What is the possible consequence of repeated inflammation of the prepuce?
Phimosis
What is the origin of the remainder of the urethra in the glans?
A bud of ectodermal cells from the tip of the glans
What is the shape of the perineum when seen from below with the patient in the lithotomy position?
Diamond
What is the name of the cartilaginous joint that lies in the midline between the bodies of the pubic bones?
Symphysis pubis
What is the lower opening of the anal canal?
Anus
What is the structure that contains the penis and the scrotum in males?
Male urogenital triangle
What is the name of the muscle that supports the weight of the body in the sitting position?
Gluteus maximus
What is the name of the bony structure that forms the posterior boundary of the perineum?
Coccyx
What is the color of the anal margin in the living?
Reddish brown
What is the structure that lies in the midline between the bodies of the pubic bones?
Symphysis pubis
What is the characteristic of the pubic hair in the female?
Has an abrupt horizontal superior margin
What is the location of the vaginal orifice?
In the vestibule, posterior to the external urethral meatus
What is the function of the hymen in virgins?
Protects the vaginal orifice
What is the boundary of the anal triangle?
Formed by the gluteus maximus muscle
What is the shape of the vestibule?
Triangular
What is the location of the fourchette?
At the base of the vestibule
What is the characteristic of the labia majora?
Fat-filled folds of skin
What is the result of the first coitus on the hymen?
It tears, usually posteriorly or posterolaterally
Study Notes
Anal Triangle
- The anal triangle is the posterior half of the perineum.
- Its boundaries are the ischial tuberosities, sacrotuberous ligaments, and the tip of the coccyx.
Anal Canal
- The anal canal is about 1.5 inches (4 cm) long and passes downward and backward from the rectal ampulla to the anus.
- The levator ani muscles and the anal sphincters keep its lateral walls in apposition except during defecation.
Structure of the Anal Canal
- The mucous membrane of the upper half of the anal canal is derived from hindgut entoderm.
- It is lined by columnar epithelium and is thrown into vertical folds called anal columns.
- The mucous membrane of the lower half of the anal canal is derived from ectoderm and is lined by stratified squamous epithelium.
Arterial Supply
- The arterial supply is the superior rectal artery, a branch of the inferior mesenteric artery.
- The inferior rectal artery, a branch of the internal pudendal artery, supplies the lower half of the anal canal.
Venous Drainage
- The venous drainage is mainly by the superior rectal vein, a tributary of the inferior mesenteric vein.
- The inferior rectal vein, a tributary of the internal pudendal vein, also drains the lower half of the anal canal.
Lymphatic Drainage
- The lymphatic drainage is mainly upward along the superior rectal artery to the pararectal nodes and then eventually to the inferior mesenteric nodes.
Innervation
- The nerve supply is from the somatic inferior rectal nerve and the autonomic hypogastric plexuses.
- The nerve supply is sensitive to pain, temperature, touch, and pressure.
Ischioanal Fossa
- The ischioanal fossa is a fat-filled space on each side of the anal canal.
Perineal Body
- The perineal body is a mass of fibrous tissue lying between the anal canal and the coccyx.
- It is surrounded by the levator ani muscles and the external anal sphincter.
Urogenital Triangle
- The urogenital triangle is the anterior half of the perineum.
- Its boundaries are the ischial tuberosities, the pubic symphysis, and the tip of the coccyx.
Puborectalis
- The puborectalis is a muscle that forms a sling around the junction of the rectum and anal canal.
- It is a part of the levator ani muscle.
Anococcygeal Body
- The anococcygeal body is a mass of fibrous tissue lying between the anal canal and the coccyx.
- It is posterior to the anal canal.
Muscles of the Scrotum
- The superficial transverse perineal muscles compress the crus penis and assist in the process of erection of the penis.
- The function of these muscles is to fix the perineal body in the center of the perineum.
Blood Supply
- The external pudendal branches of the femoral and internal pudendal arteries supply the scrotum.
- The veins accompany the corresponding arteries.
Lymph Drainage
- The wall of the scrotum drains into the medial group of superficial inguinal lymph nodes.
- The contents of the scrotum (testis and epididymis) drain upward to the lumbar (paraaortic) lymph nodes at the level of the first lumbar vertebra.
Perineal Body
- A small mass of fibrous tissue that attaches to the center of the posterior margin of the perineal membrane.
- It serves as a point of attachment for the external anal sphincter, bulbospongiosus muscle, and superficial transverse perineal muscles.
Sphincter Urethrae Muscle
- A complex structure composed of multiple parts.
- The action of the lower part of the muscle on the urethra is somewhat uncertain.
- The inferior part of the external sphincter (between the perineal membrane and the prostate) appears to form a true sphincter-like unit encircling the intermediate part of the urethra.
Internal Pudendal Artery
- Pierces the perineal membrane, enters the deep perineal space (pouch), and passes forward.
- Gives rise to the artery to the bulb of the penis; the deep artery of the penis to the crus of the penis; and the dorsal artery of the penis, which supplies the skin and fascia of the penis.
Male Urogenital Triangle
- The urethra has three parts: prostatic, intermediate (membranous), and penile (spongy).
- The prostatic urethra is about 1.25 in. (3 cm) long and passes through the prostate from the base to the apex.
Catheterization
- The external orifice at the glans penis is the narrowest part of the entire urethra.
- The urethra dilates to form the fossa navicularis within the glans.
Female Genitalia
- The mons pubis, labia majora, labia minora, clitoris, vestibule, vestibular bulbs, and greater vestibular glands.
- The epithelium of the glans has numerous sensory endings and is the most sensitive part of the clitoris.
Pelvic Fractures and Infections
- Shearing forces in pelvic fractures can damage the urethra as it emerges from the fixed perineal membrane.
- The urethra, vagina, lesser vestibular glands, and sebaceous glands of the labia majora can become infected.
- The vagina has no glands and is lined with stratified squamous epithelium, capable of resisting infection to a remarkable degree if pH is kept low.
Catheterization
- Female urethra is shorter, wider, and more dilatable, making catheterization easier than in males.
- The urethra is straight, and only minor resistance is felt as the catheter passes through the external urethral sphincter.
Vulva and Pregnancy
- A bluish discoloration of the vulva and vagina appears at the 8th to 12th week of pregnancy due to venous congestion.
- Digital examination of the vagina provides valuable information concerning the health of the vaginal walls, uterus, and surrounding structures.
Urethral Infection
- The short length of the female urethra predisposes to ascending infection, making cystitis more common in females than males.
- Five degrees of severity can occur: glandular, coronal, penile, penoscrotal, and perineal.
Development of the Penis
- The penile urethra develops from the fusion of the two genital folds and the bud of ectodermal cells from the tip of the glans.
- The prepuce (foreskin) is formed from a fold of skin at the base of the glans.
- The erectile tissue develops within the mesenchymal core of the penis.
Female Genitalia
- The changes in the female are less extensive than those in the male.
- Epispadias occurs when the genital folds fail to unite on the undersurface of the developing penis.
Surface Anatomy
- The perineum is diamond-shaped and bounded by the symphysis pubis, the tip of the coccyx, and the ischial tuberosities.
- The male urogenital triangle contains the penis and scrotum.
- The anus is the lower opening of the anal canal and lies in the midline.
Radiographic Anatomy
- The radiographic anatomy of the bones forming the boundaries of the perineum is shown in Chapter 9.
Anal Triangle
- The anus is surrounded by coarse hairs and has a reddish-brown color.
- The anal margin is puckered by the contraction of the external anal sphincter.
Male Urogenital Triangle
- The penis consists of a root, a body, and a glans.
- The symphysis pubis is a cartilaginous joint that lies in the midline between the bodies of the pubic bones.
Female Genitalia
- The labia majora are prominent, paired, fat-filled folds of skin extending posteriorly from the mons pubis.
- The vestibule is a smooth triangular area bounded by the labia minora, with the clitoris at its apex and the fourchette at its base.
- The vaginal orifice lies in the vestibule, posterior to the external urethral meatus.
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