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45 Cards in this Set

  • Front
  • Back

How is gender expressed in an embryo?

SRY gene - sex determining region of Y - produces testis determining factor (TDF)




Expressed - forms testis




Not expressed - forms ovaries

Where is testosterone produced and what does it do embryologically?

Produced in Leydig cells




Maintains Wolffian duct system

Where is Mullerian Inhibiting Hormone (MIH) produced and what does it do embryologically?

Produced in Sertoli cells




Regressed Mullerian ducts

What is the pampiniform plexus?

A venous network surrounding the testicular artery that causes countercurrent heat exchange.

What are the roles of the seminiferous tubule, rete testis, efferent duct and epididymus in sperm production?

Seminiferous tubule - spermatogenesis


Rete testis - spermatozoa collected


Efferent duct - reabsorb fluid and concentrate sperm


Epididymus - mature and store sperm

At what phase are the sperm in at mitosis, meiosis, differentiation and spermiation?

Spermatogonia, spermatocyte, round spermatid, elongated spermatid, spermatozoa

What process differentiates spermatids to spermatozoa?

Spermiogenesis

Where are spermatogonial stem cells found in the seminiferous tissue?

Near the basal membrane.

What are the junctional complexes between Sertoli cells?

Blood-testis barrier.

What do Sertoli cells produce?

Seminiferous tubular fluid, androgen binding protein and inhibin

What functions do Sertoli cells have to do with hormones?

Mediate effects of FSH and testosterone on spermatogenesis.

Describe the phases of spermiogenesis.

Golgi - polarisation




Cap - enzyme fulled cap sythesised




Acrosomal - acrosome formed




Maturation - cytoplasm becomes phagocytosed

Describe sperm motility.

ATP and Ca2+ dependent.



Dynein arms attach to adjacent microtubules. ATP hydrolysis - microtubules slide past one another. Axomere fixed to sperm head - flagellum bending. Helical motion.

What ways can ATP be synthesised in sperm and which species use each method?

Oxidative phosphorylation (midpiece) - bull




Glycolytic ATP production - mice

What do Sertoli and Leydig cells produce?

Sertoli cells - oestrogens (major in boar and stallion), cytokines - inhibin, activin, MIH during development




Leydig - androgens (mostly testosterone), oxytocin

What is testosterone converted to and why?

DHT - more biologically active

What is the cause of boar taint?

Androsterone - sexually attractive to pigs

What is the function of Myoid cells?

Maintain functional integrity and contractility of tubules.

What stimulates Leydig cells to produce testosterone?

LH and FSH

What does FSH with androgens do to Sertoli cells?

Permissive effect on spermatogenesis




Produce ABP, inhibin, activin, transferrin

What types of GnRH pulses cause release of FSH and LH?

FSH - irregular, low amplitude




LH - high frequency

What controls FSH and testosterone production?




What prevents LH surges?

Inhibin inhibits FSH production.




Testosterone production controlled by long loop negative feedback at hypothalamus and pituitary.




Exposure to androgens masculinises hypothalamus.

How is testosterone transported?

Venous blood




Lymph




Seminiferous tubular fluid bound by androgen binding protein ABP

What are some examples of masculinisation due to androgens?

Female rodent between two males in utero - masculinised and produce male biased litters




Freemartins - infertile and culled

Define puberty in the male.

Able to produce enough sperm to impregnate a female.

Why does puberty happen?

Continued sensitivity of GnRH neurone to peptide neurotransmitter kisspeptin.

What happens if there is a lack of kisspeptin?

Puberty failure and hypogonadotropic hypogonadism.

What is the difference between developmental effects and activational effects of androgens?

Developmental - totally or partly irreversible




Activational - reversible

Why does castration after puberty not remove all behaviours?

Some are learned.

Is singing in birds activational or determinative in birds?

Canaries - activational




Zebrafinch - determinative

What is the action of oxytocin in relation to spermiation?

Produced by Leydig cells




Enhances contractility of seminiferous tubule via action on myoid cells.

What is fluid absorption dependent on?

Oestrogen in tubular fluid (Sertoli cells)

What happens during sperm maturation in the epididymus?

Sperm begin to swim in straight lines.




Middle and last section - secrete fructose and glycoproteins.




Dependent on androgen stimulation (DHT)

Ehat happens during sperm storage in the epididymus?

Fluid absorbed




Oxytocin increases sperm release




Stored in cauda for 3-13 days depending on species

What is the function of the ductus deferens?

Extragonadal sperm reserves.




Sperm build up prevented by phagocytosis and/or leakage through epididymal wall

What two factors could cause activation of sperm?

Factors in seminal fluid.




Dilution of epididymal inhibition factors when added to seminal fluid.

What are some of the components in seminal fluid?

Fructose/sorbitol


Citric acid


Buffers


Proteins


Paracrine agents e.g prostaglandins


STDs!

What types of seminal plugs are there?

Fibrous plug - block others from mating




Gelatinous plug - retention in vagina

What part of the hypothalamus controls male mating behaviour?

Medial preoptic area

What is the reflex associated with psychogenic stimuli called?

Bulbocavernosus reflex

What is priapism?

Persistant penile erection.

Why is sensory feedback from glans important?

Confirms intromission has occured. Spines - may induce ovulation.

What is emission and how is it controlled?

Delivery of sperm and fluid to urethra.




Parasymp - secretion from accessory sex glands and ductus deferens




Symp - contraction of smooth muscle to propel fluid and sperm forward and to close bladder sphincter to prevent retrograde ejaculation

What is ejaculation and how does it occur?

Expulsion of sperm from penis due to prolonged sexual arousal.




Rhythmic contraction of smooth muscle of urethra and straited muscle (bulbospongiosum).




Motor output coordinated by central pattern generator in lumbosacral spinal cord.




Stimulation in paraventricular nucleus.

What happens after ejaculation?

Symp activity increases - reduced blood flow.




Penis retractor muscle pulls penis back into prepuce.




Refractory period.