Flashcards in Sperm Transport and Maturation in the Female Reproductive Tract Deck (35):
Characteristics of the phallus in birds
1. mechanism of erection is lymphatic rather than vascular
2. semen is transfered via a groove along the outside of the phallus rather than a tube in the middle
What are the two types of penises in mammals?
Describe the musculocavernous penis
-large amount of erectile tissue
-found in horse, dog, cat, and human
Describe the fibro-elastic penis
-fibroelastic tissue with smaller amounts of erectile tissue
-tends to have a sigmoid flexure
-found mostly in artiodactyls (ruminants, pigs)
What other components are found within the penis?
-paired corpora cavernosa enclosed in tunica albuginea
-os penis in some species (dogs, raccoons, seals)
-barbs on the glans in some species (rabbit, cat, ferret)
-corpus spongiosum (surrounds urethra)
What is the purpose of the retractor penis muscle? (not in all species)
keeping the non-erect penis within the prepuce
What are the 4 phases of erection?
Describe the flaccid state
maintained by tonic contraction of s.m. in the corpora and arteries supplying them under the influence of sympathetic adrenergic input
-psychic stimuli acting on the brain and tactile stimuli on the penis result in decreased sympathetic tone and increased parasympathetic tone causing relaxation of penile arterioles and smooth muscle of the cavernous sinuses
-NO and cGMP mediate relaxation and blood flows into the erectile corpora
-venous drainage is then compressed
-sympathetic tone increases and parasympathetic tone decreases
-synthesis of NO and cGMP ceases
-venous outflow is re-established and blood expelled from the cavernous sinuses returns the penis to a flaccid state
Ejaculation consists of what 2 components?
What is the function of the spinal ejaculation generator?
integrate sensory inputs from the genitalia that will trigger ejaculation with the autonomic and motor outputs required to generate the ejaculatory response
Where are sensory receptors located on the penis?
within the corpus cavernosum
What is involved in emission?
getting all the components of ejaculation into the pelvic urethra
What happens during emission?
1. secretion of fluids from the accessory glands
2. contraction of the cauda epididymis and vas deferens containing the sperm
3. closure of the sphincter at the bladder neck and the external urethral sphincter
What does parasympathetic supply stimulate in emission?
secretion of fluids by the epithelial lining of the accessory glands
What does sympathetic supply stimulate in emission?
-muscle contraction of the accessory glands to expel the fluid
-cauda epididymis and vas deferens to move sperm
-contracts the bladder neck and external urethral sphincters
What is the order of contraction of the gland systems?
bulbourethral or prostatic fraction first
sperm-rich fraction next
gland fraction last
What is expulsion?
rhythmic contractions of urethral smooth muscle and the striated bulbospongiosus muscle that expel semen from the urethra
What follows expulsion?
refractory period where sexual arousal is inhibited
When is sperm motility activated?
during the process of emission and ejaculation when they are mixed with the accessory sex gland fluids
(show progressive motility at this stage)
What is progressive motility?
when the sperm show relatively low-amplitude wave motion of the tail which gives little lateral head movement and fairly straight line motility
When do sperm develop hyper-activated motility?
at the time of capacitation
Name some factors that can influence the mechanisms and speed of sperm transport to the site of fertilization
1. species variation in size and morphology of sperm
2. duration of estrus and the timing of ovulation in relation to estrus
3. anatomical site of sperm deposition
4. the life span of sperm within the female tract
What are the barriers to sperm that deposit in the vagina?
-need first to negotiate the vagina then cervix and cervical mucous
-second need to get past the uterotubal junction (UTJ)
What are the barriers to sperm that deposit in the uterus?
only the uterotubal junction (UTJ)
How does rapid sperm transport occur?
-due to contractions of the female tract and changes in intraluminal pressures
-can be found in the upper oviduct within minutes of mating (non-viable sperm though)
What is the prolonged phase of sperm migration?
distributes competent sperm throughout the tract and it is during this phase that the fertilizing population of sperm arrive near the site they will encounter the egg
How do sperm transport through the cervix?
mucus prevents passage of appreciable amounts of seminal plasma into the upper tract, so the sperm swim deep into the cervical crypts of the cervical folds
How do sperm transport through the uterus and into the oviducts?
-uterine contractility distributes sperm throughout the uterus
-viable sperm temporarily bind to uterine epithelial cells to avoid discharge back through the cervix
-sperm accumulate at the uterine side of the UTJ and only viable sperm can move past it
Where does sperm storage occur?
in sperm reservoirs, usually the caudal isthmus of the oviduct
What is the purpose of sperm storage sites?
1. maintain sperm viability
2. serve as the site of sperm capacitation
3. synchronize final sperm maturation with ovulation
4. selection of the highest quality sperm
Binding of sperm to the oviduct is mediated by what?
mediated by glycans on the surface of ciliated oviductal epithelial cells that interact with surface proteins on the sperm plasma membrane
(binding prevents capacitation)
Name some sites of sperm selection
2. uterine epithelium
4. oviductal sperm storage area