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004 - Reproductive Biology > (17) Sperm Maturation > Flashcards

(17) Sperm Maturation Flashcards

1
Q

(Structure of the Spermatozoa)

read pic

  1. Contain only 50% (normal 80-90) water due to what?
  2. Divided into what three main regions?
A
  1. loss of most cytoplasm during spermiogenesis and condensed nature of nucleus
  2. head

mid piece

principal piece

(mid piece + principal piece = tail)

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2
Q

(The head)

  1. consists mostly of what?
A
  1. head and acrosome

(Also some cytoskeletal elements and scant cytoplasm.)

The head is flattened “spatulate”

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3
Q

(Structure of Spermatozoa)

(nucleus)

  1. haploid DNA
  2. DNA is condensed ( Protamines replace histones during the final stages of spermiogenesis and there are lots of disulfide bonds - both resulting in DNA compaction.)
  3. the nuclear envelope (membrane) has very few pores over most of its surface
A
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4
Q

(Structure of the Spermatozoa)

(Acrosome)

  1. Derived from what?
  2. forms a cap over the apical 1/2 to b of nucleus
  3. tightly sandwiched bewteen what inside, and what outside?
  4. Contains a complex array of proteins and enzymes including acrosin (a trypsin-like protease) and hyaluronidase among others. These may be both free within the acrosome or bound to the inner membrane surface.
  5. Also bound to the inner membrane surface are numerous protein receptors that will be exposed later and are important in what?
A
  1. the golgi
  2. nuclear membrane inside, sperm plasma membrane outside
  3. binding to the egg zona pellucida during the process of fertilization
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5
Q

(Structure of the Spermatozoa)

(The Equatorial segment)

  1. This is an area where what occurs?
  2. does it contain enzymes?
  3. it is the PM of this region that dos what?
A
  1. caudal part of the acrosome thins
  2. no
  3. fuses with oocyte at fertilization
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6
Q

(Structure of the Spermatozoa)

(the tail)

  1. The propeller - provides the force of locomotion and egg penetration at fertilization. Divided into what 4 sections?
  2. If you look at cross section of the rest of the tail (distal to connectiv piece) the major structural components are what five things?
A
  1. connecting piece

middle piece

principal piece

end piece

  1. axoneme

outer dense fibers

mitochondiral sheath

fibrous sheath

outside all of these and covering sperm head - the PM

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7
Q

(Structure of the Spermatozoa)

(Axoneme)

  1. consists of microtubules in 9 + 2 - runs down center of entire tail (mid + principal + end)
  2. The two central microtubules are surrounded by 9 microtubule doublets. Radial spokes connect the central pair to the outer doublets and each outer doublet is connected to its 2 adjacent doublets (so in cross-section it looks like a wagon wheel).
  3. What proteins are important for generating the force required for axonemal slideing and movement?
A
  1. dynein and nexin (found in the connections)
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8
Q

(Strucuture of the Spermatozoa)

(Outer Dense Fibers)

  1. 9 dense fibers, one located outside and adjacent to each of the 9 outer microtubule doublets
  2. they extend how far?
  3. They don’t all end at the same level but gradually thin and disappear, fibers opposite each other tend to disappear at the same level.
  4. play a role in force generation?
A
  1. hrough the mid piece and for a variable length down the principal piece (~60%) depending on species
  2. no (provide stiffening and elastic recoil)
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9
Q

(Structure of Spermatozoa)

(mitochondrial sheath)

  1. confined to what?
  2. number and arrangement varies
  3. use what to provide close to all ATP needed for slding ithe axonemal microtubules (via movement of dynein arms) in force generation.
A
  1. middle piece

(mitochondria are helically arranged around the outer dense fibers in this region.)

  1. oxidative phosphorylation
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10
Q

(Structure of Spermatozoa)

(Fibrous Sheath)

  1. When the mitochondrial wrapping ceases at the end of the middle piece it is replaced by the fibrous sheath, that extends the length of what?
  2. unique to mammals and some birds
  3. It consists of 2 longitudinal columns connected by transverse ribs - it forms a slowly tapering cylinder.
  4. Regulates the spatial plane in which the tail beats  permits better propulsion?

Also appears to act as the structural site anchoring many enzymes involved production of ATP by glycolysis - this is now considered extremely important for proper motility as ATP produced by oxidative phosphorylation in mitochondria of the mid piece would have too far to diffuse to be effective in most of the principal piece.

A
  1. the principal piece (It is located outside the dense fibers until these diasappear.)
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11
Q

(Structure of Spermatozoa)

(end piece)

  1. After the fibrous sheath ends the axoneme tapers and terminates
  2. This section that consists only of the tapering axoneme covered by the plasma membrane is the end piece
A
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12
Q

(Structure of the spermatozoa)

(The Sperm Plasma Membrane)

  1. Covering the entire sperm, the plasma membrane is highly specialized and vital for normal sperm physiology and the events of fertilization.
  2. The membrane is divided functionally, structurally and biochemically into different regions, with each being specialized to a different task.
  3. membrane over midpiece has proteins important for what?
  4. over areas of head has what?
  5. The membrane composition is further modified during transit through the what?
  6. It is damage to the plasma membrane that is responsible for most of the adverse effects of exposing sperm to cold temperatures, either inadvertently during collection, or deliberately during storage (cooled or frozen).
A
  1. ATP production
  2. proteins and lipids important for fertilization
  3. epididymis (and following ejaculation the female repro tract)
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13
Q

(Sperm Transport)

  1. Once released at spermiation the sperm (immotile at this stage) are carried through the seminiferous tubule and into the rete testis by fluid flow. Fluid movement is likely aided by peristalsis of the tubules in response to secretion of what?
  2. From the rete the suspension is moved rapidly through what into what?
A
  1. oxytocin secretion from Leydig cells
  2. efferent ducts in the proximal epididymis
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14
Q

(Epididymis)

  1. present in speceis that do internal fertilization (mammals, reptiles, birds) - not in fish or amphibilans
  2. highly coiled structure - connects what to what?
  3. functions to do what?
  4. While anatomically divided into caput, corpus, and cauda - functionally has been divided into what (plus give fuction)
A
  1. efferent ducts to vas deferens
  2. transport, protecnt ,sustain, mature and store spermatozoa

(It achieves this by maintaining a specialized internal environment that is a function of its lining epithelial cells. The environment and functions vary along its length.)

  1. initial (fluid resorption)

middle (sperm maturation)

terminal (sperm storage)

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15
Q

(Epididymis) cont

  1. Most fluid leaving the testes is resorbed in what?
  2. Fluid secretion also occurs, largely on a regional basis. This coupled with resorptive functions and secretion of specific products means sperm are exposed to an ever changing environment as they move through the epididymis and these changes are responsible for sequential maturational changes of the sperm. The protein composition of the epididymis is different to that of both serum and testicular fluid.
  3. Sperm do not swim through the epididymis but are moved passively through the caput and corpus by fluid flow induced by what?

is rate of transport affected by freq of ejacualation?

  1. cauda epidiymis is major site of what?

It’s wall contracts when stimulated - can ejacluation freq alter amount of time sperm spends here

  1. Can you increase sperm output by increasing freq of ejac to a certain point?
  2. Sperm transport through epididymis
A
  1. the efferent ducts and proxiaml epididymis (this raises osmotic pressure and sperm become dehydrated)
  2. peristaltic contractions of wall

no

  1. sperm stoarge

yes to a degree

  1. no

because sperm are produced at a constant rate in the seminiferous tubule, and move through the caput and corpus epididymis at a fixed rate

Up to that point you just catch more of those that were produced - i.e. you can’t make them actually produce any more).

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16
Q

(Epididymis cont)

  1. sperm tranpsort takes how long?
  2. how long can sperm be formed in fertile state in cauda?
  3. Many functions of the epididymis appear to be dependent on what?
A
  1. 7-14 in most (2-4 in humans)
  2. one month
  3. androgen, mainly DHT
17
Q

(Sperm Maturation)

  1. Are sperm fertile when they leave the testis?

When are they?

process by which they gain fertility is called what?

(changes that occur in sperm during transport)

1-4 what are they?

A
  1. no

by the time they are stored in the epididymal tail

sperm maturation (poorly understood)

  1. gain potential for motility
  2. change in cell surface electrical charge (change in carb and protein of PM) - ability to fertilze
  3. alteration of PM structure
  4. movement of cytoplasmic droplet from neck to distal part of midpiece
18
Q

(Sperm Storage in Epididymis)

  1. stored in queisencet state - this allows what?
  2. can they be stored indefinitely?
  3. n the celibate male, once the cauda is full, the flow of new sperm moving down from the epididymal corpus expels more mature sperm out the what into what - where what happens?
A
  1. ejaculation of greater amount of sperm than daily output
  2. no (aging sperm undergo degeneration)
  3. vas deferens into urethra to be expelled in urine (ram, bulls) or spontaneous ejactulaton (rodents)

ensures that old sperm is removed

19
Q

Maintenance of sperm quiescence during storage

The mechanisms by which sperm are kept in a suspended state vary, some are general and some more species specific. Many species will use a combination of methods.

A
20
Q

(Maintaining metabolic quiescence)

  1. low sodium content in bathing fluid - to do what?
  2. close together - accomplishes what?
  3. secretion of viscous mucoprotiein (immobilia in rodents) - to do what?
  4. Secretion of cell permeating acids that diffuse into cells to keep pH low - (bulls)
  5. possibly high pCo2 and sperm dehydration
A
  1. H stays in cell for movement
  2. restricts movement
  3. restrict movement
21
Q

(Preventing premature sperm activation)

  1. Sperm need to be activated prior to fertilizing the egg, part of this process involves modification of the plasma membrane, an event termed what?
  2. If this happends to early how does this affect sperm?
  3. For mammals this generally will involve secretion by the epididymis of proteins that coat sperm membranes and stabilize them - these are termed what?
  4. in some species what also appears to be affective?
A
  1. capacitation
  2. incapable or reaching site of fertilization (Very early activation)

incapable of fertilizing egg

  1. decapacitation factors
  2. clumping of the sperm
22
Q

(The Vas Deferens (Deferent Duct))

  1. an extension of what?
  2. what kind of muscle?
  3. near urethra may widen to form what in some species?
A
  1. the epididymis (runs from cauda to pelvic urethra)
  2. smooth
  3. ampulla (considered accessory sex gland by some)
23
Q

(Accessory Sex Glands)

  1. these supply the bulk of what?
  2. what are they?
  3. Not all species contain all glands. The dog has only a prostate, while the cat has no seminal vesicles.
A
  1. bulk of fluid in the ejaculate
  2. seminal vesicles

prostate

bulbourethral gland (Cowper’s gland)

(some people include ampulla)

24
Q

(N.i. Functions of the Accessory Gland Fluids)

  1. Activation of sperm motility - due to what?
  2. Buffering capcity - some say it is for what?
  3. nutrient supply

what sugars

why important?

A
  1. dilution
  2. alkaline to neutralize acid vag
  3. fructose, glucose, and sorbitol

sperm rely 90% on external nutrients (sugars supply this - diff sugars used by diff spec)

also some lipid around that can be used

25
Q

(N.i. Functions of the Accessory Gland Fluids)

(Cont)

  1. Stimulate what?

due to presence of what?

  1. Clean what?
  2. Plug what?
  3. decapacitating factors - Glycoproteins in the ejaculate serve to do what?
A
  1. uterine contractions (uterine, vaginal, and cervical SM)

prostaglandins

  1. urethra

components expelled inorderly manner

bulbourethral first - cleans

  1. the cervix

In some species, such as rodents and humans, proteins in the seminal vesicular fluid coagulates the ejaculate, which later liquefies. In rodents an additional coagulating gland causes hardening of this fraction which forms the cervical plug to prevent backflow of semen from the uterus, or fertilization by another male.

  1. further coat the PM of sperm to stabilze and prevent activation - removed in female tract

004 - Reproductive Biology (30 decks)

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