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The Perineum
The perineum
58
Anatomy
Undergraduate 3
03/19/2014

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Cards

Term
What is the perineum?
Definition
The diamond shaped space beneath the pelvic diaphragm
Term
What are the 3 things contained within the perineum?
Definition
1. External genitalia
2. Anal canal
3. Ischiorectal fossa
Term
What is the ischiorectal fossa?
Definition
The fat filled space in the perineum
Term
(T/F) The perineum is divided into 2 triangles
Definition
True
Term
Name the triangles, and which structures are within what triangle
Definition
1. Urogenital triangle (anterior) - external genitalia 2. Anal triangle - anal canal and the ischiorectal fossa
Term
What is the urogenital diaphragm?
Definition
A muscle that covers the inferior surface of the levator ani and fills the triangular space
Term
What is the superficial (inferior) fascia of the urogenital diaphragm called?
Definition
Perineal membrane
Term
What are the attachments of the urogenital diaphragm? What does this mean?
Definition
1. Ischiopubic ramus
2. Pubis
3. Ischium
- That it is a horizontal muscle
Term
What are genitalia?
Definition
The external reproductive organs
Term
What are the two parts to the male genitals?
Definition
1. Penis
2. Testes
Term
(T/F) The penis consists of 3 cylinders in its erectile tissue
Definition
True
Term
Name 3 groups of tissue
Definition
1. Corpora cavernosa
2. Corpus spongiosum
3. Urethra
Term
What are the two parts of the corpora cavernosa?
Definition
1. The crus
2. A shaft
Term
What is the function of the crus?
Definition
Helps form the root of the penis
Term
What is the function of the shaft?
Definition
reaches to the glans penis
Term
What is the function of the paired ischiocavernosus muscles?
Definition
Attach the crura to the body of the ischium
Term
(T/F) The corpus spongiosum lies between the two corpora cavernosa
Definition
True
Term
What forms the bulb of the penis?
Definition
The root of the corpus spongiosum
Term
What is the muscle that covers the corpus spongiosum at its root?
Definition
The bulbospongiousus muscle
Term
Where does the urethra enter the penis? What other structures joins the urethra here?
Definition
At the bulb; the bulbourethral glands
Term
What is the glans penis?
Definition
The distal, expanded end of the penis
Term
(T/F) The lower third of the vagina is the urogenital triangle
Definition
True
Term
What is at the superior angle of the vestibule?
Definition
The clitoris
Term
(T/F) The clitoris shares little structure with the penis
Definition
False, there is a lot of structure homology between the 2
Term
What is the labia majora?
Definition
Outer folds surrounding the vestibule
Term
What is the labia minora?
Definition
The folds of skin surrounding the vestibule
Term
What is the superior meeting point of the labia majora?
Definition
The mons pubis; superior
Term
What is the posterior meeting point of the labia majora?
Definition
The Fourchette
Term
(T/F) The fourchette is just anterior to the perineal body
Definition
True
Term
List the 5 structures comprising the vulva
Definition
1. Mons pubis
2. Lab Maj
3. Lab Min
4. Clitoris
5. Vestibule
Term
List the characteristics of the anal canal
Definition
- 4cm long
- Distal portion of digestive system
Term
Where does the anal canal begin?
Definition
As the rectum passes through the levator ani
Term
Name the features of the anal canal
Definition
1. Anal columns
2. Pectineal line
Term
What are the anal columns?
Definition
The longitudinal folds in the upper section
Term
What is the pectineal line?
Definition
The inferior border of the anal columns
Term
What is the significance of this line?
Definition
Marks the end of the blood and nerve supply to the GI tract
Term
What is the difference between the internal and external anal sphincters?
Definition
Internal: smooth muscle, involuntary
External: skeletal muscle, voluntary
Term
What are the 3 components of the external anal sphincter?
Definition
1. Deep
2. Superficial
3. Subcutaneous
Term
What is the fat filled space between the anal canal, the levator ani, and the obturator internus?
Definition
The ischiorectal fossa
Term
What is found within the ischiorectal fossa?
Definition
The pudendal canal
Term
What is found within the pudendal canal?
Definition
The pudendal artery, nerve, and vein
Term
List the two branches the internal pudendal artery gives rise to? How does this artery enter the perinium
Definition
1. Inferior rectal artery
2. Perineal artery

Via the pundendal canal
Term
What does the internal pudenal artery bifurcate into?
Definition
The deep and dorsal arteries of the penis/vagina
Term
(T/F) The pudendal nerve is a somatic nerve
Definition
True
Term
Where does it originate? How does it get to the perineum?
Definition
S2,3,4; follows the same path as the artery
Term
What is the branch that the pundendal nerve gives off before dividing? What is the target of this nerve?
Definition
Inferior rectal nerve - the skin of the anal triangle and to the externa anal sphincter
Term
What two nerves does the pudendal nerve divide into?
Definition
1. Perineal nerves
2. Dorsal nerve of the penis/clit
Term
Describe the general pathway of sympathetic innervation to the reproductive organs
Definition
Preganglionics from the lower thoracic and lumbar roots synapse at the same level, and the postgangs travel with the splanchnic nerves to the peraortic plexus, then continue down the plexi, through the inferior hypogastric plexus, and to the taregts
Term
Which portion of the reproductive system is an exception to this general pattern?
Definition
The gonads
Term
What usually supplies the gonads? Describe their route of innervation?
Definition
Least splanchnics - leave T12, synapse in the renal ganglia and follow the gonadal arteries to the gonads
Term
Where does parasympathetic input of the reproductive system originate?
Definition
Pelvic splanchnic (S2-4) via the inferior hypogastrics
Term
What is the SNS responsible for in the MRS? PNS?
Definition
SNS: induce ejaculation
PNS: erection
Term
What happens to the postgang fibers after the pelvic splanchnics have synapsed in the inferior hypogastric plexus?
Definition
Enter the erectile tissue and induce vasodilation, therefore causing erection
Term
Where does SNS output from ejaculation usually come from? Do the preganglionics usually synapse at that level, or are they splanchnic?
Definition
L1-2; usually synapse at that level
Term
Describe the route for SNS innervation for ejactulation?
Definition
Post synapse, the fibers usually follow the splanchnics down the descending chain of plexi to the inferior hypogastric plexus
Term
How do SNS fibers cause ejaculation?
Definition
- Musculature of the vas deerences and prostatic capsule is contracted by SNS
- Sphincter of bladder contracted as well
Term
What structure assists ejaculation, and what nerve innervates it?
Definition
- Bulbospongiosus
- Innervated by pudendal nerve
Term
(T/F) The clit receives similar innervation to the penis
Definition
True
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