male reproductive system

Male reproductive system

Lets start from ovotestis to testis transition. (see earlier blog for information about mullerian and wolfian duct, and ovotestis)

The Y chromosome has testis determining factor (tdf gene)

Y à(transcription)à RNAà(translation)àprotein

Now, this protein acts on adrenal cortex to secrete sexocorticoid called androgen.

Androgen does two things:

1. degenerates cortex part of ovotestis

2. It promotes medulla part of ovotestis. Thus, it promotes differentiation of gonadal cells to form interstitial cells and sertoli cells. These two help in spermatogenesis, but don’t form sperms.

Note : sperm mother cells are extra-gonadal and extra-embryonic, i.e they are not original residents of gonads.

Sertoli cells secrete MIS (mullerian inhibiting substance). It acts on mullerian duct and blocks its growth.

Interstitial cells secrete testosterone and promotes wolffian duct with form epididymis, vas deferens and vasa efferentia i.e whole ductous system.

This process is completed in 2^nd month of foetus.

è Testes

It is formed in abdominal cavity (not in scrotal sac). It is also connected with dorsal body wall.

Before parturition, in 7^th month of foetus, testosterone level in blood increases, which widens inguinal canal (inguinal canal connects abdominal cavity to scrotal sac). This results in descending of testes from abdominal cavity to scrotal sac (extra abdominal position but abdominal origin).

All blood vessels, nerve firbes, lymph vessels connected with muscles called cremaster muscles from dorsal abdominal wall. This structure is called spermaticord. It connects testes to dorsal body wall, and also supplies blood to it.

The mesentery of testes is called mesorchium

Note:

Mesentary = structure which connects an organ to dorsal body wall in human eg. Mesovarium is mesentery of ovary.

Omentum: connects organ to stomach

Ligament: a structure which connects one organ to another organ except stomach.

*** In birds and frog, mesorchium is connection between testes and kidney.

Lower portion of testes is connected with scrotum by gubernaculum. Similary, two testes in scrotum are separated by septa scroti.

Temperature of scrotum is 2 – 2.5 degree Celsius less than body for proper functioning of testes.

As testes descends, Inguinal canal is completely plugged with Connective tissue.

*** But in rat, bat testes descends to scrotal sac only during breeding season,i.e Inguinal canal is permanently open. Or, temperature varies from non-breeding to breeding season.

Empty scrotal syndrome

Testes remain in abdomen, temperature is high. This is also called cryptorchidism (crypt: hidden). It leads to steriliy.

As a cure, during birth, a booster dose of testosterone or Luteinizing Hormone (Interstitial Cells stimulating Hormone) is given which helps in descend of testes.

*** In whale, elephant, seal, spiny ant eater, platypus etc., testes is permanently present in abdominal cavity. i.e Cryptorchid condition is normal in these organisms. Inguinal canal is non functional in thes organism. In platypus, temperature of environment is so low that testes shud remain in abdomen.

Sometimes, two testes are fused together in scrotal sac, if septa is not developed. This is called synorchdism or testes fusion syndrome. It may(but not always) lead to sterility.

As body temperature rises, the scrotal sac has dartose muscles. It is highly thermosensitive. It enlarges so that surface area of srotum increases and heat radiates out faster. If temperature is low, it constricts and testis gets near the crater of inguinal cavity and takes body heat from abdominal cavity. Cremaster muscle is also heat sensitive.

Inguinal hernia: If inguinal canal remains open, part of large intestine just enters and exerts pressure. So, it descends.

Testes has 3 coverings, tunica vaginalis (outer coelomic peritoneum), tunica albuginae ( white fibrous and actual covering), and tunica vasculosa ( vascular part, with blood supply)

Hydrocoel = when coelomic fluid amount in cavity of vaginalis increases.

Some of the tunical albuginae enters into inner region of testes and divides it into 250-300 testicular lobules.

Each testicular lobule has 1-3 semeniferous tubules (highly coiled) where spermatogenesis occurs.

All semeiferous tubules open into 20-30 straight tubuli recti. Tubuli recti opens into highly coiled rete testes. It is internally lined by cuboidal epithelium.

Rete testes opens into small 10-20 ducts called vasa efferentia.

Vasa efferentia is internally lined by ciliated cells and endocytic cells. Ciliated cells support the movement of sperm to epididymis(as it is not fully mobile yet). Endocytotic cells feeds on cell debris, external fluid etc.

Vasa efferentia opens into paired highly coiled duct (around 6m… no I didn’t measure it anyways…I’ve better jobs to do)

In epididymis, movement of sperm is by peristalytic movement and segmental movement.

Epididymis is lined by basal cells(undifferentiated cells, form new principle cells) and principle cells ( have non motile stereo cilia, secrete nutritive substance and also secrete substance for maturation of sperm)

The sperm becums active and motile when it stays in epididymis for at least 18 hours. Thus, epididymis is responsible formaturation and storing sperms. Unejaculated sperms degenerate and absorbed there.

Principle cells of epididymis secrete maturation factor called glycerophosphocholine(GPC). GPC is incorporated with sperm membrane and makes it more stable and less permeable(because acrosome has a lot of digestive enzymes, so, GPC is needed)

Epididymis has 3 parts, caput (head), corpus(body) and cauda(tail).

Vasa efferentia opens into capute. From cauda, another duct develops called vas deferens. It is also lined by stereo cilia. Main part of storage of sperms is vas deferens. It is 35 m long.

Vas deferens is associated with spermaticord and enters into abdominal cavity. Swollen part is called ampulla of vas deferens. Vas deferens passes between rectum and urinary bladder.

As duct of seminal vescicle opens into vas deferens, it is not called ejaculatory duct.

Both the ejaculatory duct open into a common duct called urethra.

Urethra has 3 parts: -

1. prostatic urethra(around 5 cm): prostate gland secretes prostatic secretions at semen here.
2. membranous urethra (smallest, just around 1-2 cm)
3. penile urethra (around 20 cm)

At junction of penile urethra and membranous urethra,, paired glands called cowpers glands peresnt which secrete mucous.

Penis

It has 2 types of muscles: -

1. Corpora cavernosa: present dorsally, column like and paired
2. corpus spongiosum: single column like and present ventrally

In corpus spongiosum, penile urethra is present.

These muscles have a large no/- of sinusoids. Sinus is very vascular(has rich supply of blood). This helps in erection of penis.

At action of acetyl choline, the whole system of muscles becums erect.

At terminal part of penis, corpus spongiosum becums enlarged and now called glans penis. It is covered with loose flap of skin called as prepuce/ foreskin.

*** during circumsition, the prepuce is cut.

Prepusal glands called glands of Tyson are present between glans penis and prepuse. It secretes oily/waxy substance and prevents from infection.

Epididymis is absent in frog, fish and toad. In these, maturation and storing of sperms happens in semeiferous tubules.

Tubuli recti + rete testes + vasa efferentia = intra testicular genital ductus system

Entire testes + epididymis = testicle.

Some Glands:-

Seminal vescicles

• paired
• present between urinary bladdr and rectum
• secrete seminal fluid (contributes 60% – 70% of total semen)

Seminal fluid contains

1. fructoseè nutrition to sperms
2. prostaglandins è it makes uterus more receptive to sperm movements by inducing anti peristalytic movements in uterine canal
3. seminogelin: it is an important clotting protein
4. clotting factor: important for coagulation of semen in female genetaria
5. inosytol } support clotting
6. citrate } -do-
7. ascorbic acid } -do-
8. fibrinogen } -do-
9. other proteins

Prostate gland

• single
• prostatic secretions contribute 20% - 30% of semen

Prostatic secretion contain

1. ionic calcium (due to this, semen looks milky in colour) } contribute to
2. Phosphate ion } alkalinity
3. carbonate ion } of semen
4. spermine(a nitrogenous base like adenine):reacts with phosphate to form crystalline spermine phosphate
5. amino acid }
6. profibrolysin } important for clotting
7. clotting proteins }

Prostate is essential for activation of sperm. Its removal leads to sterility

Cowper’s gland

• secretes mucous
• lubrication of urethra

Semen

• each ejaculation contains 3-4 mL of semen
• it contains 80 – 100 million sperms per mL
• if sperm count decreases to less than 20 million, it leads to steriliy
• pH around 7.3-7.4 (slightly alkaline)
• In entire body, only semen has fructose.

Diseases

Prostatis: inflammation of prostate gland due to infection

It leads to dysurea (painful urination)

Benign prosatic hypertrophy: -

• Enlargement of prostate gland
• Completely normal
• 1^st during puberty, 2^nd during age of around 40 years
• Cells become enlarged
• May lead to dysurea and nocturea

Prostatic cancer

• due to removal of prostate gland
• testosterone promotes Pr. Cancer. Hence, castration(removal of testes) may cure this if done in early stages of cancer.

Impotence

• Inability to erect the penis in adult male
• Due to behavioural, neural, physiological or psychological disturbance.