(18) Sperm Transport and Maturation in Female Repro Tract

Question 1

(Introduction)

1. For animals, it seems necessary for fertilization to occur in some form of aqueous environment. For water dwellers this was not a problem and many continue to broadcast eggs and sperm to the environment for fertilization to occur externally. Animals that moved onto the land needed a way of overcoming their dry terrestrial environment, and developed internal fertilization. As part of this process there had to be a way of transferring sperm from the male into the female, and many developed some form of intromittent organ, or penis.

Question 2

(Intro)

1. In birds… what percent still have a phallus?

in those that have one - erection is what rather than vascular?

semen is transferred via a what?

2. Chickens and turkeys have a non-intromittent phallus that is erectile and contains a median groove through which sperm is discharged.

In passerines the intromittent organ is insignificant/absent and sperm is transferred to the female during a brief “cloacal kiss”.

Answer 2

1. 3% (mostly waterfowl and ratites)

lymphatic

groove along the outside of the phallus rather than tube in the middle

Question 3

(Mammalin Penile Anatomy)

1. what are the 2 penis types?
2. Musculocavernous type has a large amount of erectile tissue and is found in what?
3. fibroelastic is seen most in what?

predominated by what?

The penis in these speies tends to have a sigmoid flexure, and the funtion of erectile tissue is to do what?

Answer 3

1. musculocavernosus and fibro-elastic
2. horse, dog, cat, human
3. artiodactyls (eg ruminants, pigs)

fibroelastic tissue with smaller amounts of elastic tissue

straighten this out so that the penis protrudes, (aided by relaxation of the retractor penis muscles)

Question 4

(Penis cont)

1. Within the penis are paired corpora cavernosa enclosed in the tunica albuginea.

Is separation of sides complete?

This is a high pressure system that provides what?

2. Some species (dogs, racoons, seals) have an os penis (or baculum) - which is what?
3. In others, especially those where the female is an induced ovulator, the penis may have a series of barbs on the glans to enhance mechanical stimulation of the vagina at mating - in what?

Answer 4

1. no (degree of fusion varies btwn spec)

rigidity

2. originates as a calcification of the fused ends of the corpora cavernosa.
3. rabbit, cat, ferret

Question 5

(Penis cont)

1. The corpus spongiosum surrounds the urethra and terminates as what?

It is a low pressure system that functions to do what?

2. innervation is what?
3. What is responsible for keeping the non-erect penis within the prepuce but are not present in all species.
4. During the juvenile period the penis is attached to the prepuce and cannot be fully extended. This attachment later breaks down.

Answer 5

1. the glans penis

increase penile volume

2. both both autonomic (sympathetic) and parasympathetic

and motor/sensory via pudendal

3. the paired retractor penis muscles

Question 6

(Erection)

1. Process of erection divided into what 4 phases?

Answer 6

1. flaccid, tumescense, stable erection, and detumescence

Question 7

(Erection)

(flaccid state)

1. maintained by tonic contraction of what?

under influence of what?

Answer 7

1. of smooth muscle in the corpora and arteries supplying them

under the influence of sympathetic adrenergic input (NE)

(little blood enters the vascular spaces.)

Question 8

(Erection)

1. During erection, psychic stimuli acting on the brain and tactile stimuli on the penis (transmitted both to the local spinal cord reflex and to the brain) result in what?

causing what?

2. Increased parasympathetic tone mediates this relaxation by doing what?
3. Venous drainage is then compressed, partly by what and by what?
4. Contraction of the ischiocavernosus muscles then compresses the “crura” or “bulb”, an expansion at the base of the corpus cavernosum, against the pelvis. This does what?

Answer 8

1. decreased sympathetic tone and increased para tone

relaxation of penile arterioles and smooth muscle of the cavernous sinuses

2. increasing formation of Nitric oxide (NO) and subsequently cGMP - which mediates the relaxation and blood flows into the erectile corpora (filling the sinusoidal spaces).
3. partly by expansion of the corpora (compresses subtunical venules) and partly by contraction of bulbospongiosus and ischiocavernosus muscles
4. pressurizes the blood in the corpus cavernosum and results in rigid erection

Question 9

(Erection)

1. At the start of detumesnence sympathetic tone does what? para?
2. synth of what ceases (and what happens as a result
3. There is a brief increase in corpus cavernosal pressure as smooth muscle begins to contract under the influence of what?
4. Venous outflow is re-established and blood expelled from the cavernous sinuses, returning the penis to the resting flaccid state.

Answer 9

1. sympathetic tone increases and parasympathetic tone decreases
2. synthesis of NO and thus cGMP ceases and existing cGMP is broken down by phosphodiesterase 5 (PDE5)
3. noradrenalin (sympathetic) while the venous outflow system is still closed

Question 10

(emission and ejaculation)

1. Ejaculation consists of 2 integrated components: Emission and Expulsion.
2. Both are mediated as spinal reflexes withing what?
3. The function of this center is to do what?
4. Sensory stimuli from the genitals, especially the penis, may involve temperature, pressure and tactile/friction stimuli.
5. The sensory receptors are located on what?
6. info is sent via what nerves?

Answer 10

2. the “spinal ejaculation generator”
3. integrate sensory inputs from the genitalia that will trigger ejaculation with the autonomic and motor outputs required to generate the ejaculatory response.
4. penile skin, glans, urethra and within the corpus cavernosum
5. dorsal penile and pudendal nerves.

(Supraspinal areas may exert either stimulatory or inhibitory control on the spinal reflex.)

Question 11

(Emission)

1. This phase involves getting all the components of ejaculation into the pelvic urethra
2. It includes what three things?

(Both parasympathetic and sympathetic components of the autonomic nervous system are involved.)

1. Parasympathetic supply stimulates what?
2. Sympathetic stimulation causes what?

Answer 11

2. secretion of fluids from the accessory glands, contraction of the cauda epididymis and vas-deferens containing the sperm, and closure of the sphincter at the bladder neck and the external urethral sphincter.
3. secretion of fluids by the epithelial lining of the accessory glands.
4. muscle contraction of the accessory glands to expel the fluid, cauda epididymis and vas deferens to move sperm and also contracts the bladder neck and external urethral sphincters.

(*Not all gland systems are stimulated to contract at the same time, with the result that the ejaculate may be fractionated. Generally a bulbourethral or prostatic fraction will be excreted first to cleanse the urethra, the sperm-rich fraction (containing some accessory gland fluid) will follow, and finally another accessory gland fraction, often from the seminal vesicles.)

Question 12

(Expulsion)

1. Continued sexual stimulation causes further activation of spinal systems and when this reaches a certain threshold, expulsion is triggered.
2. What act to expel semen from the urethra?
3. in addition there are rhythmic contractions of what?

Answer 12

2. Rhythmic contractions of urethral smooth muscle and the striated bulbospongiosus muscle
3. ischiocavernosus, levator ani and external urethral sphincter muscles.

(these are variously under para and motor control)

(This phase is normally followed by a refractory period where sexual arousal is inhibited.)

Question 13

(Activation of Sperm Motility)

Sperm were kept immotile during storage in the cauda epididymis. Their motility is activated during the process of emission and ejaculation when they are mixed with the accessory sex gland fluids (you can do the same with a physiological solution in vitro). In this state sperm show progressive motility - the kind you would see when looking at freshly ejaculated sperm under a microscope - and this is due to relatively low-amplitude wave motion of the tail which gives little lateral head movement and fairly straight line (progressive) motility in non-viscous media. With this type of motion sperm swim at 1-4 mm/min.

This term activated motility for sperm expressing progressive motion is somewhat confusing; it is called this because it is “activated” by dilution of the sperm in accessory sex gland fluids at the time of ejaculation. However it isn’t the “sperm activation” referred to previously that is necessary for fertilization and involves capacitation (mentioned in section L.i.b.). At the time of capacitation, sperm develop their second type of motility termed hyper-activated motility. We will talk about that change closer to fertilization.

Question 14

(Sperm Transport and Maturation in the Female)

1. Sperm transport in female depends on what?
2. Female can influence motility of sperm in what three ways?

Answer 14

1. movement of sperm and contractions of female
2. spatial constraints

epithelial cell surface characteristics

physical properties of tract secretions

Question 15

(Factors that influence movement of sperm to fert site)

• species variation in size and morphology of sperm
  • duration of estrus and the timing of ovulation in relation to estrus
  • anatomical site of sperm deposition
  • the life span of sperm within the female tract

Question 16

The anatomical site of sperm deposition affects the number of barriers the sperm must overcome before reaching the site of fertilization in the oviduct.

1. In species with vaginal deposition (ruminants, primates) the sperm need first to navigate what?
2. what is the second barrier?
3. In (ruminants and primates) they make cervical mucus thick when?

thin when?

4. Species with direct uterine deposition of sperm (horse,dog, pig) have what as physical barrier?

Answer 16

1. the vagina then cervix and cervical mucus
2. uterotubal junction (UTJ - junction of uterus and oviduct)
3. diestrus (prevent sperm penetration)

estrus (encourage it)

4. UTJ

(These barriers create a gradient of sperm numbers through the female tract, with relatively few ever reaching the site of fertilization.)

Question 17

(Rapid Sperm Transport)

1. sperm found in upper oviduct within minutes of mating - but are what?
2. most likely facilitated by what?
3. what is function?

Answer 17

1. non-viable
2. female tract contractions (too fast for sperm alone)
3. don’t know - could signal upper female tract which can then influence subsequent events of sperm transport and fert

Question 18

(Prolonged (Sustained) Phase of Sperm Migration)

1. In this phase competent sperm is distributed throughout tract - it is during this phase that what occurs?

Answer 18

1. he fertilizing population of sperm arrive near the site they will encounter the egg.

Question 19

Sperm Transport Through the Cervix

In species where semen deposited in vagina (ruminants, primates) must first get through cervix and mucus.

Sperm swin through the mucus

cervix has folds, and (at least in cow) sperm swim deep in these crypts (cervical folds)

1. do sperm travel slower or faster here?

why?

2. In these species it appears cervical mucus may serve as what?
3. there is some thought that cervix may be serving as what? (based on only some sperm making it)?

Answer 19

1. faster

secretions in crypts less viscous (sialomucins) than outside (sulfomucins)

2. a sperm reservoir (found 120 hrs after)
3. selective barrier (only strong get through)

(however, during diestrus the mucus is pretty much impenetrable)

Question 20

(Sperm Transport Through the Uterus and into the Oviduct)

Uterine contraction distributes sperm thorughout uterus - but doesn’t aid sperm motility much

some think contractions move sperm towards oviducts - some don’t

1. this may vary with site of deposition - with large volumes associated with direct uterine deposition the movement may be more what?
2. What have been shown to increase uterine contractions in certain species?
3. What is seminal plasma increase myometrial contraction
4. In Swine, large amounts of what in seminal plasma increase uterine contraction?

Answer 20

1. random (majority expelled out cervix)
2. Presence of the male, coitus and products within the semen
3. prostaglandins
4. estrogen (maybe by increasing prostaglandin)

Question 21

Sperm Transport through the Uterus and into the Oviduct

cont

1. viable sperm can temp bind to uterine epi cells - why?
2. Sperm accumulate at uterine side of UTJ - what are considered requirements for movement thorugh this barrier during prolonged phase of transport?

Answer 21

1. avoid discharge through cervix
2. normal motility, morphology and plasma membrane

(This is the major barrier for species with intrauterine ejaculation)

Question 22

(Sperm Storage)

When insemination occurs prior to ovulation, sperm accumulate in certain areas of the female
tract, sperm reservoirs, until an unknown signal activates them to continue to the site of fertilization.

1. The most important storage site = ?

in this area the sperm develop contact with what?

motility at this stage?

2. what four purposes does sperm storage at this site serve?

Answer 22

1. caudal isthmus of oviduct (fert occurs in next portion - the ampulla)

oviductal epithelium

is suppressed

2. maintain sperm viability

site of sperm capacitation

synchronize final sperm maturation (capacitation) with ovulation

selection of best sperm

Question 23

(Sperm Storage)

1. Binding of sperm with ciliated oviductal epithelial cells is mediated by what?

these lectins are product of what?

2. Only what sperm can bind in reservoir?

why?

3. Binding prevents uptake of what by sperm?

why?

4. Other sites that may be important for sperm storage are the cervical mucus in primates and ruminants; binding of sperm to the uterine epithelial cells in many species, and the uterine side of the UTJ in the mare. Millions of viable sperm may exist in these sites and likely serve to replenish numbers in the oviductal storage site, where only a few thousand may be found at any time.

Answer 23

1. glycans that interact with surface proteins (lectins) on sperm PM

accesory sex glands (seminal vesicles) that coat sperm during emiision/ejaculation

(lectins and glycans differ btwn species)

2. sperm that have not already undergone capacitation

prevent premature sperm activation

3. Ca++

keeps in stasis (prevents capacitance) - which preserves viability

(Release of sperm from binding may be controlled by the female, mediated by the events surrounding ovulation.)

Question 24

(Sperm Selection)

1. Sperm in the lower tract are rapidly removed by what?

others are eliminated how?

2. excess sperm in the oviduct may be removed by what?
3. of sperm selection (quality control) potentially occur where?

Answer 24

1. efflux through the cervix and out of the vagina.

by the leukocytes that invade the uterine lumen in response to insemination

2. flow out into the peritoneal cavity
3. cervix (mucus, access to privileged pathways)

uterine epithelium

UTJ oviductal sperm storage area

(and eventually site of fert)

Question 25

(The oviductal binding sites appear to select for sperm that are what four things?)

Answer 25

• not capacitated (see later)
  • not acrosome reacted (see later)
  • morphologically superior
  • chromatin intact (no DNA fragmentation)

(Of billions that may have been ejaculated, only a few hundred or thousand make it this far.)