Sperm production
Download
1 / 54

Sperm Production - PowerPoint PPT Presentation


  • 684 Views
  • Updated On :

Sperm Production. Male Sex Organs. While the male sex organs are present at birth, they only begin to produce spermatozoa at puberty For most bulls, this is 7-12 mo.’s of age At 12-18 mo.’s, sperm production is half that of a fully mature bull.~. Pathway of Spermatozoa.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Sperm Production' - Donna


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Male sex organs l.jpg
Male Sex Organs

  • While the male sex organs are present at birth, they only begin to produce spermatozoa at puberty

  • For most bulls, this is 7-12 mo.’s of age

  • At 12-18 mo.’s, sperm production is half that of a fully mature bull.~


Pathway of spermatozoa l.jpg
Pathway of Spermatozoa

  • Spermatozoa are manufactured in the testes (primary sex organs of the bull)

    • Spermatozoa are the actual genetic material-carrying cells

    • Semen/sperm is everything – the cells, the fluids, etc.

  • Testes have two primary functions

    • 1. production of spermatozoa

    • 2. production of male sex hormones

  • Bulls should have two testes, each with their own compartment inside the scrotum. ~


Testes l.jpg
Testes

  • A testis is made primarily of small tubules (the seminiferous tubules)

    • Where production of sperm takes place

    • 0.2 mm in width, up to 4.8 km in length!

  • As spermatozoa mature, they move toward a duct at the center of each tubule

  • The testes also produce and secrete fluids that nourish and transport the spermatozoa in route to the epididymus.

    • This is separate from accessory gland fluids! ~


Testes8 l.jpg
Testes

  • Leydig cells/interstitial cells are dispersed throughout the testes and produce male hormones (androgens)

    • Testosterone is considered the primary male hormone

    • Testosterone is released under the influence of LH from the pituitary gland.

    • Both LH and FSH are needed for sperm production ~


Male hormones l.jpg
Male Hormones

  • Male Hormones are necessary for:

    • Onset and maintenance of sperm production

    • Sex drive (libido)

    • Development and maintenance of secondary sex characteristics (organs and features) ~


Epididymus l.jpg
Epididymus

  • After leaving the testes through ducts in the seminiferous tubules, sperm enter the epididymus.

  • The epididymus is a tubular structure located on one side of the testes.

  • It is packed with a milky nutritive substance as well as spermatozoa from the testes.

  • Spermatozoa mature in the epididymus

    • An assembly line, not a storage unit!~


Vas deferens l.jpg
Vas Deferens

  • From the epididymus, spermatozoa enter the vas deferens.

  • This carries the spermatozoa into the body cavity towards the urethra

  • It is surrounded by muscles that contract during ejaculation. ~


Ampullae of henle urethra l.jpg
Ampullae of Henle, Urethra

  • The vas deferens enlarges inside the pelvis to form the ampullae

    • Where spermatozoa are stored and mixed with a nutritive substance.

  • During copulation, sperm is moved into the urethra.

    • This is a common pathway for both urine and semen (the mix of the products of the testes and accessory glands.) ~


Accessory glands 3 l.jpg
Accessory Glands (3)

  • There are three accessory glands:

    • 1. Seminal Vesicles – secrete a fluid high in sugars (fructose) to nourish the spermatozoa – feels like a bag of grapes (palpation)

      • This fluid also dilutes sperm at ejaculation and serves to activate motility

      • Rich in proteins, fructose, enzymes.

      • Secretes prostaglandins, causing uterine contractions

    • 2. Prostate glands – forms bulk of fluid in semen

      • Creates a basic pH of 7.5-8 – protects sperm

    • 3. Cowper’s gland – lubricating substance

      • Cleanse male and female reproductive tracts prior to passage of spermatozoa (King Sperm’s archers)

  • These secretions are released almost instantaneously

  • Male sex hormones are crucial for this process. ~


Urethra and penis l.jpg
Urethra and Penis

  • The urethra extends to the tip of the penis, where it exits the body.

  • Urethra surrounded by smooth muscle – crucial for ejaculation.

  • Penis is composed of sponge-like blood tissue

  • Under sexual stimulation, this tissue fills with blood, enlarging it and enabling it to be inserted into a female’s vagina.

    • Otherwise, it is kept inside the body cavity in most species ~


Spermatogenesis l.jpg
Spermatogenesis

Topics:

  • Blood Testes Barrier

  • Cryptorchidism

  • Meiosis

  • Hormone cycles

  • Environmental androgens

    • ~


Blood testis barrier l.jpg
Blood Testis Barrier

  • Sertoli cells have a “tight junction” barrier which serves to prevent the body from destroying the sperm.

    • Why would the body destroy sperm?

    • HINT: Chromosome #’s and types

  • The BTB is a physical barrier between the testes and the seminiferous tubules.

    • Think of the grapefruit! ~


Slide24 l.jpg
BTB

  • The Sertoli cells form a barrier that prevents blood from accessing the lumen of the seminferous tubules.

    • How is this a good thing?

    • How is this a bad thing?

  • What would happen if the BTB were breached?

  • TPS~


Btb destroyers l.jpg
BTB Destroyers

  • Anything that destroys the BTB will lead to an impairment of meiosis and spermatogenesis.

  • BTB Destroyers include:

    • Heat

    • Heavy Metals

    • Pesticides

    • Low amounts of FSH and/or Testosterone


Case study l.jpg
Case study

  • You were called to the bull barns of ABS Global in DeForest.

  • One of their bulls appears to have a fertility problem and your diagnosis is needed.

  • What things should you check for?

  • When would the cause of infertility happen if we are just seeing symptoms now?

    • Would this make a diagnosis more difficult?

    • TPS~


Case study 2 l.jpg
Case Study #2

  • Heat damages sperm in 2 main ways:

    • 1: It can cause a breach in the BTB

    • 2: DNA polymerase in sperm requires a lower temperature; it will degrade at normal body temp and meiosis will be interrupted.

  • A stallion has been diagnosed with partial cryptorchidism (kript-or-kai-dizm).

  • The attending vet has recommended that the animal be put down.~


Case study 2 cont l.jpg
Case Study 2 (Cont)

  • The breeder is furious with the vet’s suggestion, given this is a prize animal.

  • She has contacted you for a second opinion.

  • Will you support the first vet’s suggestion of putting this prize animal down, will you perform an operation, or will you leave the animal alone (given it has one good testis)?

  • TPS!~


Cryptorchidism l.jpg
Cryptorchidism

  • Remember the importance of reproduction in agriculture!

  • Remember the one and only job of a male in the dairy, horse, sheep, etc. industry.

  • As vets, this is you primary concern in regards to bulls, stallions, and rams.

  • A testis or both testes can fail to descend for a number of reasons.~


Cryptorchidism causes l.jpg
Cryptorchidism causes

  • Cryptorchidism is usually a genetic disorder.

  • The physiological cause can be hormonal, a hernia, or a malformed structure (e.g. blood vessel that is too short).

  • As such, animals with the disorder should not be used for breeding purposes.

    • The risk of infertility in future generations outweighs any benefit an animal could otherwise have.~


Other concerns l.jpg
Other Concerns

  • Sperm cell formation-discussion to come later

  • Male health and nutrition

  • Male-orientation – Diagnosis difficult; can still be viable breeders under the right circumstances


Spermatozoa formation l.jpg
Spermatozoa Formation

  • Spermatozoa cells have to have half of the chromosomes that other cells have

    • Otherwise the baby would have double the number of chromosomes.

  • The formation of spermatozoa begins in the testes.

    • Multiple divisions take place (meiosis) until a final division that reduces the chromosomes to half their original number. ~


Spermatogenesis34 l.jpg
Spermatogenesis

  • Spermatogenesis starts at the edge of the seminiferous tubules and moves towards the lumen (center) of each ST.

  • This begins when a germ cell (reproductive cell) undergoes mitosis, becoming spermatogonia

    • Spermatogonia: stem cells that create sperm cells

  • Growth, meiosis, and differentiation follow. ~


Steps of spermatogenesis l.jpg
Steps of Spermatogenesis

  • Step 1: Mitosis - A germ cell divides into two identical cells, then four - spermatogonia~


Mitosis review l.jpg
Mitosis Review

  • Interphase: nucleus of cell is well defined; nothing much going on otherwise

  • Prophase: chromosomes form as DNA tightens into coils of chromatin. Chromosomes duplicate. Mitotic spindles form, centrosomes move to opposite sides of cell. ~


Mitosis l.jpg
Mitosis

  • Prometaphase: nuclear envelope disappears. Microtubules attach to chromosomes and attach to the kinetochore of the chromosome.

  • Metaphase: chromosomes line up~


Mitosis41 l.jpg
Mitosis

  • Anaphase: chromosomes separate, move to opposite ends with microtubules

  • Telophase: chromosomes begin to dissolve; nuclear envelope re-forms. Cell undergoes cytokinesis~


Meiosis l.jpg
Meiosis

  • Spermatogonia must then undergo meiosis to reduce their chromosome number to half the normal amount

  • Meiosis starts the same with a Prophase, Metaphase, Anaphase, and Telophase/Cytokinesis.

  • However, it then undergoes another round of divisions, this time without duplication. ~


Spermatogenesis animation l.jpg
Spermatogenesis Animation

  • http://highered.mcgraw-hill.com/olc/dl/120112/anim0043.swf


Hormones and sperm production l.jpg
Hormones and sperm production

  • After puberty, spermatozoa formation is a continuous process.

  • This process is controlled by the endocrine system.

  • FSH and LH are important in stimulating the testes to produce spermatozoa and testosterone. ~


Male hormone loop l.jpg
Male Hormone Loop

  • Brain releases GnRH

  • GnRH tells pituitary to release FSH, LH

  • LH tells Leydig cells to release testosterone, whichstimulates production of sperm.- note negative feedback! ~


Briefly edc s l.jpg
Briefly – EDC’s

  • Endocrine Disrupting Chemicals are a serious concern today.

  • These chemicals have similar chemical conformations to sex hormones and mimic their effects in the body.

  • What impact would this have on a body; remember negative feedback! ~


Edc s l.jpg
EDC’s

  • “To date, in vitro and in vivo studies have identified several antiandrogenic toxicants including vinclozolin, procymidone, linuron, several phthalate esters, and p,p’-DDE, all of which alter male rat sex differentiation.”

    • Emerging Issues Related to Endocrine Disrupting Chemicals and Environmental Androgens and Antiandrogens

    • Gray, et. al. , US Environmental Protection Agency ~


A concern l.jpg
A Concern

  • In humans and other mammals, male fertility has dropped significantly.

  • This has also been seen in cattle; it is much harder to breed a cow today than it was 50 years ago.

  • Furthermore, cases of sexual abnormalities have increased in amphibians and reptiles.

  • Is this genetic or environmental? ~


Sperm situations l.jpg
Sperm Situations

  • Sperm are not hardy; they are rather fragile cells

  • They are very susceptible to:

    • Heat

    • Jarring

    • Radiation

    • Poor Nutrition

    • Infrequent ejaculation (increases abnormalities)

      • A mature bull can ejaculate as much as 7 consecutive times without a severe reduction in spermatozoa


Infertility l.jpg
Infertility

  • Infertility is not immediately recognizable!

    • Symptoms may show 2.5-3 mo’s after!

    • It takes ~70 days to produce sperm, and overy two weeks to travel through the epididymus.

  • A mature bull should produce 70 billion sperm/week.

    • The heavier the testes, the more sperm is produced.


ad