UG diaphragm Flashcards
Describe the anal canal and the pectinate line.
There is an internal sphincter of smooth muscle and an external sphincter of skeletal muscle. Both sphincters are right below the ampulla where waste gets stored.
External sphincter is the one we can control kind of but when peristalsis and pressure overrides the internal and external sphincter, we defecate.
The anal canal itself has two divisions and is the only area besides the mouth where ectoderm meets endoderm.
Above the pectinate line:——————
Origin: hindgut
Innervation: autonomic, visceral afferents which sense pressure
Blood supply: superior rectal artery, superior rectal vein (portal)
Lymphatics: internal iliac nodes
Hemorrhoids: internal, painless, covered by mucosa
Below the pectinate line ===========
Origin: ectoderm
Innervation: somatic efferent
somatic afferent (pain, temperature, touch)
Blood supply: inferior rectal artery, inferior rectal vein (caval system)
Lymphatics: the superficial inguinal nodes
Hemorrhoids: external, covered by skin, painful.
Describe the UG diaphragm
It is a sub-floor of the pelvic diaphragm having nothing to do with the anal canal and only sphincteric control of urethra (SPHINCTER URETHRAE MUSCLE) and vagina. It also contains the deep transverse perineal muscles which tighten everything.
Superior fascia > muscle > perineal fascia
These three layers will compose the deep perineal pouch
Is the base of support for external genitalia and stretches from ischiopubic ramus to ramus.
What is the difference between the deep perineal pouch between females and males.
In males, the muscle surrounding the urethra is the sphincter urethrae muscle.
In female, the muscle surrounding the urethra and the vagina is the compressor urethrae muscle.
The male has the bulbourethral gland which lubricates the spongy urethra. Obviously females wouldn’t have this.
Describe the male external genitalia.
First come in the erectile tissue - which has a lot of space and can be filled with blood.
Almost like a tripod, on the perineal membrane will be first left and right crura attached to the ischiopubic ramus. They come together to form the corpora cavernosa.
The corpus spongiosum has the urethra running through it and is inferior the corpora cavernosa. The region that is attached to the UG diaphragm is the bulb of the penis.
Next cover these tissues with a deep fascia (buck’s fascia) Now…
Surrounding the corpora cavernosa and corpus spongiosum are tunica albuginea which are quite rigid.
Between Buck’s fascia and the tunica albuginea is the deep dorsal vein which will become shut when the erection occurs. internal pudendal arteries supply the tissues.
The tunica albuginea is thinner around the corpus spongiosum because the urethra is running through it and needs to be more relaxed.
- Muscles will only be attached to regions that themselves have attachments.
Ischiocavernosus muscle attaches to the crura.
Bulbospongiosus muscle attaches to the bulb of the penis: it is important for squeezing the ejaculate out of the urethra.
Superior transverse perineal membrane, above the deep and does the same shit. - Superficial perineal fascia (dartos)
Describe two kinds of urethral tears.
The prostatic urethra detach - will get blood filling the subperitoneal space. (UG diaphragm)
A tear in the spongy urethra will have blood filling the superfifical perineal pouch
Describe the formation of the female external genitalia.
The short crura come together at the midline to form the corpora caveronosum to form the body of the clitoris. At the tip of the clitoris is a gland.
There are two corpus spongiosum on either side and that is the vestibular bulb. At the end of the bulb is the greater vestibular gland which lubricates the vagina). It is under the labia minora (the unfused urogenital sinus), the two vestibular bulbs meet at the midline.
Then a deep layer of fascia.
Then all of the erectile tissues are covered by muscle.
Bulbospongiosis muscle over the vestibular bulbs to maintain blood in there.
Ischiocavernous muscle covers the crura
Superficial transverse perineal muscle.
Then the superficial fascia, continuation of the scarpas and known as colles fascia.
What is an episiotomy
Cutting through skin and widens the space so the baby can come out easier. Likely cut through the perineal body.
Describe the blood supply of the perineum
Internal pudendal arteries exit the greater sciatic foramen and back into the lesser sciatic foramen and travel along the obturator internus lateral walls in the pudendal canal and send branches to erectile tissue, pouches, anal canal.
The venous drainage is the internal pudendal vein > internal iliac (caval)
IN MALES:
Draining the erectile bodies is the deep dorsal vein which empties into the prostatic plexus > internal iliac (caval)
Describe the innervation of the perineum
Somatic:
Pudendal nerve (S2, S3, S4)
Pudendal has three branches of interest
1. Inferior rectal nerve (motor and sensory)
-motor to external anal sphincter, levator ani, and sensory in the ischioanal fossa
- dorsal nerve (PURE sensory, between bucks and tunica albuginea, sensory to dorsum of the penis and clitoris
- Perineal nerve (sensory and motor)
supplies all the structures in the superficial and deep pouches.
preganglionic body in L1, L2
Postganglionic body from sacral paravertebral ganglia
-ejaculation
-the only place we see sympathetic chain being used
-preganglionics travel in lumbar splanchnics > synapse in sacral symapthetic ganglia > axons exit to the gray rami > travel along the pudendal nerve > reach the external genitalia.
Parasympathetic (THE LOWEST):
Preganglionic travel in pelvic splanchnics, postganglionic travel in cavernous nerves
-erection and vasodilation.
-preganglionics travel along the pelvic splanchnics > synapse in the inferior hypogastric plexus > postganglionic axons in cavernous nerves (to relax the blood and cause erection)
What muscles attach to the perineal body (central tendon)
Perineal muscles:
Deep and superior transverse perineal muscle, bulbospongiosus, external anal sphincter (somatic innervation, inferior rectal nerve)
Pelvic muscles:
Pubococcygeus
Puborectalis
What are two pathways for sympathetic innervation of the perineum?
What is the only pathway for parasympathetic?
- L1 or L2 of the spinal cord. Preganglionic axons travel in lumbar splanchnics nerves to superior hypogastric plexus, then enter the pelvis via hypogastric nerve, synapse on the inferior hypogastric plexus
Postganglionic- axons travel with the internal pudendal artery to the perineum. - Preganglionic cell bodies in L1 or L2. Their axons exit the white communicans, enters the sympathetic chain (paravertebral), travels down to sacral levels, exits the gray communicans and travels with the ventral rami through the pudendal nerve.
Parasympathetic
1. Cell bodies in S2,3,4, travel in pelvic splanchnic nerves to the inferior hypogastric plexus and synapse there, then the postganglionic axons travel through cavernous nerves, through UG diphragm to erectile tissue.
