Male Reproductive Systems

8/10/2019 Male Reproductive Systems

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Topic 24- Reproduction & Development: Male Reproductive Syste

Reproductive systems:

Not essential for individual, essential for species continuation

Reproductive organ: gonad produces gametes & hormones

o Male: testes

o

Female: ovary

Male Reproductive anatomy

Glands of Male repro.

1. Seminal vesicle: Highly converluted glandular tube tightly coiled. Whenejaculation, smooth muscle contract and it pours out all the seminal fluid intoejaculatory duct

2.

Prostate: Upon ejaculation, pours its content into ejaculatory duct3. Bulbourethral gland: Pea size gland at base of penis. Function to lubricate theurethra. In normal state, lots of acidic urine passes through. During sexualarousal, it secrete lubricating fluid which makes it more alkaline and lubricatesthe tube so that it gets ready for the seman (sperm + seminal fluid)

Pathways/ducts

i. Spermatogenesis occur in the seminiferous tubules deep in the testis

ii. Immature non-fertile sperm go to epididymus (long tightly coiled tube 6m

long)where they learn to swim.

iii. Upon sexual arousal, ejaculation from epididymusmove through ductus

deferenloop over the pubic bone through inguinal canal (inguinal canal: weakare of abdominal wall, testes went through this during embryonic development; inguinal

hernia: part of bow herniated through canal)

iv. Ductus derferen loop over superior medial aspect of ureter.

v. Ductus deferen swell upampulla of ductus deferen

vi. 2 ductus deferen converge within the prostate glandto form ejaculatory

duct

vii.this duct is share with urethra. Prostatic urethrapass through uragenital

diaphragm at base of pelvis called membranous urethraspongy urethra

Corpus Cavernosum: erectile tissue full of vascular space


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Seminal fluid

Produced by Accessory glands

Sperm doesnt have a lot of cytoplasm:just carry genetic info, they rely on

the seminal fluid to provide nutrients to survive.

Transport medium, transport sperm and nourish them supply energy for

sperm

o 10% fluid & sperm: vas deferens(within seminiferous tubules)

o 60% fluid: seminal vesicle

o 30% fluid: prostate gland

o a small amount from bulbourethral gland (lubricating) goes before

the seman comes, activated by parasympathetic NS.

The seminal fluid from seminal vesicle contains:

o Fructose: the sugar the sperm rely on for energy

o Prostateglandin: cause excitation of smooth muscle in male and

female once semen gets to female repro tract helping to propel

semen and sperm along

o

Coagulating enzyme: once ejaculation occur, the semen coagulate

first, high up in the females tract and then after a few minutes it

starts to liquidfy again. The purpose of this is to hold it up in the

females repro tract to facilitate fertilization of ovum

The fluid from the Prostate gland:

o Citrate:for sperm energy

o PSA:Prostate Specific Antigen, diagnostic test for enlargement of

prostate gland that occurs in old man

o Fibrinolysin: help lyses the seminal fluid clot and liquidfy it

pH 7.5: Urethra tends to be acidic and the female repro tract is acidic so

the seminal fluid has to be slightly alkaline to counteract that

2~5mL semen. 100 million sperm/mL

Temperature regulation of the testes

Scrotal sac designs to support the testes outside of our body. Testes need to be 3

degrees cooler to facilitate spermatogenesis.

1. Vascular:

a. Pampiniform plexus- testicular artery branched from descending aorta

bringing the hot blood from the core to the testes. Venus blood is taken

back to core. Plexus like grape vine wrap around testicular artery covering

it. Reasonit absorb the heat of testicular artery so the heat from the

core is transfer into vascular network, so blood can take that heat back to

core.

2. Muscle

a. Dartos musclesmooth muscle deep to skin attach to dermis of scrotum

i. Cold: respond as reflex to cold temperature, it contracts and

causes the skin of scrotum to wrinkle conserving the loss of heat.

ii. Heat: relax, increase SA of skin to release heat

b. Cremaster muscleskeletal muscle extend from internal oblique muscle.

i.

Cold: Respond in relex fashion to cold they contract and lift thetestes up closer to core.

ii. Heat: relax allow the testes to move away from torsal


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Embryonic stage (5~6weeks)

In embryo, there are two ducts; outer: Mullerian duct, inner: Wolffian duct

Male:The Presence of chromosome SRY(Sex determining Region of Y chromosome)

Wolffianduct will elaborate and develop testes and ducts and start producing

testosterone. Mullerian duct will degenerate. Once testes start to form, they start

pumping out testosteronedrive the elaboration of male repro system andmature the testes.

Female: The absence of SRYwolffian duct will degenerate, mullerianduct will

elaborate to produce ovary and uterus.

Male fetus have testesstill part of the peritoneum. Once testosterone star to be

produced, it will elaborate the scrotum (scrotal swelling become scrotal sac) Testes start

to follow the ligament called Gunbernaculum. Gunbernaculum attach to scrotal sac. It

doesnt change size/length but fetus continues to grow. because the ligament stays the

same, it pull testes down to scrotal sac till birth. With male baby born too early,

undecended testes can be seen. Journey over pubic bone through inguinal canal. It will

close over leaving part of peritoneumtunica vaginalis stays covering testes.

If undecended, can be dangerous, not right position for spermotogenesisaffect

fertility. Called cript orcadium (sleeping fruit) not producing sperm.

The Penis

2 columns of erectile tissues (corpora carvinosa)

innermost (corpus spongiosum)

The arteries feed the erectile tissue are innervated with parasympathetic nerve fibres.

During sexual arousalparasympathetic dominate and erection

Nitric oxide is release from artery causing vasodialation cause blood to fill vascular space

in erectile tissue. The fibrous layer around the penis doesnt stretch so it keeps penis

erect. It presses on the vein and drain the penis so the erection can be sustain and once

ejaculation occur, it switch to sympathetic nervous system and blood vessel constrict

and called resolution

The testes

Testis has a fibrous layer called tunica albuginea(innermost layer) another covering

called tunica vaginalis(ourtermost later of testeis; come with it on its journey from

abdominal during embryo development)

Seminiferous tubule- convoluted in lobules 200 lobules within testes.

i. Spermatogenesis occur at seminiferous tubule,

ii. then immature sperm move to bigger space called rete testis

iii. then move to epididymus (stay for 20 days) learn to swim

a. ejaculated

b.

or get absorb by phagocytosis within duct of epididymus

Epididymus:Fluid regulation, recycling damaged spermatozoa, storage, transport and

maturation of spermatozoa


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Meiosis and Mitosis

Mitosis

cell replication and division where the chromosomal number remains unchanged

in the process line up along midline and divide

2 daughter cells

daughter cells have same amount of chromosome material as parent cell

Meiosis

reduction division process

number of chromosomes are halved to 23 (n)haplo, instead of 46 (2n) diplo

4 daughter cells

only occurs in production of gametes (in testes and ovary)

Process of Spermatogenesis

a. infant: spermatogonium are cell that are present in semineferous tubules from

birth, they undergo mitosis. Dividing so there are many of them around basal

lamina

b. Puberty: Spermatogonium enter into meiosis 1. Surge of hormone, testosterone

rises, the cells near the border (called B cells) enter into meiosis

c. Once it goes through the blood- testes barrier it turns into primary spermatocyte

d.

Meiosis I

e. Secondary spermatocyte

f. Meiosis II

g. Early Spermatids

Spermiogenesis

h. Late Spermatids

i. Morphological change to spermatozoa

In this process, they are moving deeper; from basal laminaadluminal

compartment

Sustentocytes support and nourish

Spermatogonium are outside of the sustentocytes but envelope by them

Tight junction forms blood-testes barrier when the cell enter meiosis during

puberty, all the antigenic protein on surface will change. To the individual, these

cell are unfamiliar so the blood/immune system recognise them as foreign. So

they have to be kept separate from the blood.


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Spermiogenesis

No chromosomal change Only morphological change

Sperm change from oval shape to spermatozoa

Headof sperm contain enzyme, it has a helmet called acrosomewhich prevents

the enzyme from coming out before it hits the ovum

Head: nucleus with DNA material

Midpiece: microtubules for whipping tail and a lot of mitochondria for ATP

Tail: Flagella

Released from sustentacular cell at stage 6


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Drive spermatogenesis

Secondary gender characteristic

Anabolic effeects

Metabolism: protein synthesis and muscle and bone growth

Anabolic steroids:

Mimic the effects of testosterone

Increase energy and tendency for aggression

Protein synthesis, muscle development

Long term use can lead to testicular atrophy (affecting the negative

feedback and interferes the HPG axis)

Cant separate the anabolic and androgenic effects yet

Male sexual response

Erection

parasympatheticnerve dilate the arteries of penis

secrete Ach which then release nitric oxide (NO)

NO relaxes arteries of penis and relax the smooth muscle in corpora cavernosa

nand corpus spongiosum, allowing them to become filled with blood

Ejaculation

Sympatheticnerves Contraction of vas deferens releases sperm into ejaculatory duct while prostate &

seminal vesicles expel fluids into urethra

Sphincter at bladder tightly closed to prevent backflow of semen into bladder

Filling urethra with semen triggers nerve impulses to skeletal muscles at base of

penis

Rhythmic contractions occur at 0.8 sec intervals & increase pressure in urethra

Semen ejaculated to exterior Orgasmic phase (intense physical pleasure)

Resolution Phase

Temporary refractory period

Another erection cannot be stimulated

Genitalia returns to pre-arousal state

Semen

Clotting enzyme from seminal vesicles causes fibrinogen in seminal vesicle fluid

to coagulate

Holds seman in deeper regions of vagina

Coagulum dissolves during next 15-30 mins because of lysis by fibrinolysin

(prostatic fluid)


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Documents

Male Reproductive Systems